POSTER 22: NOMTM - Field campaigns, new sensors and methods
A Wavelet-based, Low-cost Method for Massive On-site Diurnal Urban Climate Observation Using Three Globe Thermometers
University of Hong Kong, Hong Kong S.A.R. (China)
Microclimate, different from macrometeorology or mesometeorology, is the direct meteorological influence on outdoor human thermal healthy and labour safety. Massive field measurement, which requests simultaneous observations of multiple meteorological parameters, is of crucial significance in the database refinement and the development of environmental information processing technologies of urban microclimate. However, most integrated scientific measuring instruments, either a portable weather station or a combination of several different functional instruments, are expensive and cumbersome. A real massive field experiment is costly and complex. It is impracticable for most research institutions, especially for those in developing countries and rural regions. To fill this gap, this paper proposes a low-cost back-calculation method for the massive on-site diurnal data observation. Parameters to be estimated are the air temperature, low-temperature longwave radiation, solar radiation and air velocity. These parameters govern outdoor human thermal balance and are the most representative elements that can describe a specific outdoor microclimate. The proposed back-calculation method is inspired by the globe thermometer and the pan-radiometer. The only format of collected signals is temperature, which is the easiest available parameter in meteorology. Continuous wavelet analysis is conducted to target the matching frequency range between the thermal response of globe thermometers and background environmental parameters. The globe temperatures are discomposed using discrete wavelet transformation according to its frequency domain correlation with radiation and air speed respectively. Environmental radiation and air velocity are estimated by solving real-time heat balance equation sets. Finally, calculation results are compared with the field measurement by standard meteorology instruments to validate this method.
Experimental Study on the Suitability of Acrylic and Copper Globe Thermometer for Diurnal Outdoor Mean Radiant Temperature Measurement
University of Hong Kong, Hong Kong S.A.R. (China)
The globe thermometer has been commonly used as a meteorological instrument for measuring the mean radiant temperature for at least 80 years. Originally it consisted of a hollow copper sphere. In recent years, the acrylic globe thermometer has also become widely used for outdoor measurements because of its fast response time and being more economical to produce. However it has been found that the mean radiant temperature measured using an acrylic globe thermometer is mostly inconsistent with that of the more accurate three-dimensional integral method. To investigate why such a discrepancy occurs, static indoor experiments and dynamic outdoor experiments were conducted to compare and explore the thermal response of both a copper and an acrylic globe thermometer. Our measurements were also compared with theoretical predictions. In addition, the spatial distributions of temperature on the exterior surface and in the interior of the globe were measured. The effect of surface optical properties was also discussed. We conclude that the acrylic globe thermometer is not suitable for outdoor use, while the copper globe thermometer can be used. Plastic globe thermometers are also not recommended for measuring the mean radiant temperature of an indoor environment with significant asymmetric radiation.
Measurement of roughness parameters over urban heterogeneous canopy
1National Defense Academy, Japan; 2National Institute of Advanced Industrial Science and Technology, Japan
Zero-plane displacement height over urban canopy was measured in the downtown area in Tokyo, where the building canopy was quite heterogeneous mixture of the high and low buildings. We used temperature variance method, which determined the displacement height from the measured variance of temperature at a single level. We installed a sonic anemometer at 51 m AGL on the tower, which was five times higher than the mean building height.
The measured displacement height was 24 to 35m; largest at the area with the skyscrapers and the least in the park area. However those were much larger than the mean building height. The reason for the exceeding should be owing to the height variation of buildings in the canopy. The measured displacement height normalized by the maximum building height agreed with the traditional morphometric method. The results are also agreed with a previous numerical model study.
One-year continuous observation enabled us to discuss seasonal variation of the displacement height. Our results showed higher displacement height in winter than in summer, which could indicate the atmospheric stability dependency of the displacement height.
MOBO – An Experimental Network for Urban Heat Island Analysis in a Green District of the Middle-East
Masdar Institute of Science and Technology, United Arab Emirates
Masdar hOBO (MOBO) is a three-year long experimental effort to evaluate the efficiency of Masdar Institute (UAE) in mitigating the Urban Heat Island (UHI). For this purpose, we installed a network of 72 temperature and relative humidity loggers over the Masdar Institute campus at 3, 7, 11, and 14 meters. A weather station was also installed at 700 meters from the campus to measure open desert conditions. In this paper, we analyze the summer UHI effect measured during the MOBO campaign. Using measurements of summer temperature from 2011 to 2013, we first calculated the average UHI intensity between each HOBO logger and the rural station. According to the MOBO experimental network, this statistical value varied from -0.5 to 1.7 degrees Celsius, and reached its mean value over the campus at 0.3 degrees Celsius in summer. Next, we evaluated the peak value of the UHI intensity average diurnal cycle assessed from measurements of each data logger. As a result of this analysis, it turns out that the summer diurnal cycle peak was 1.1 degrees Celsius on average over the MOBO network, and never exceeded 4.5 degrees Celsius. Finally, we compared the average and the diurnal cycle peak of UHI intensity we obtained in Masdar Institute to the ones reported in two other cities of the Middle-East: Kuwait City (Kuwait) and Muscat (Oman). From this survey, we found that the UHI effect is less significant in Masdar Institute than the one observed in Kuwait City and Muscat. To provide a suitable dataset for urban canopy model validation in a hot and arid climatic environment, we are planning to lead a new experimental campaign in Masdar Institute with measurements of urban turbulences and pressure in addition to temperature and relative humidity.
Two EC sites on one urban mast: what can we learn?
1Finnish Meteorological institute, Finland; 2Division of Atmospheric Physics, University of Helsinki, Finland
In urban micro-meteorology we are normally forced to compromise by measuring in non-ideal sites: on masts and even in the roughness sublayer. This typically creates flow distortion, creating complications in data analysis and flux estimations. Basic quality control of a single sensor can be performed based on vertical deflection angles and expected tke (turbulent kinetic energy), and sometimes even by simply disregarding whole (flow-distorted) sectors. It is of course not ideal that we have to reject so much data, especially for e.g. carbon budgets.
We now have the opportunity to test the validity of those basic quality-control measures given that we have many months of data of TWO eddy-covariance setups at the same height on either side of the same tower (Torni), in downtown Helsinki (Finland).
This work is part of a larger joint effort by the Finnish Meteorological Institute (FMI) and the University of Helsinki: we have launched a state-of-the-art observational network for Helsinki’s urban atmosphere, called Helsinki UrBAN (Urban Boundary-layer Atmosphere Network, http://urban.fmi.fi). The instruments within this network include a lidar, a ceilometer, weather stations, a sodar, eddy-covariance flux towers, a thermal camera, building surface thermometers and scintillometers.
- For directions where neither setup is downwind of the mast, how well do the data from the two setups compare?
- For flow-distorted directions, can we better assess the quality of data from this particular Helsinki mast?
- What can we learn that helps interpretation of other urban micro-meteorological tower-based measurements?
Challenges and results from conducting eddy covariance observations in areas of tall buildings
1Shanghai Institute of Meteorological Science; 2Department of Meteorology, University of Reading
While numerous eddy covariance (EC) studies of turbulent heat and carbon dioxide fluxes have been conducted for North American and European cities, such data are lacking for areas of tall, dense buildings which are being built extensively in Asia and elsewhere globally. Here, one year (December 2012 to November 2013) of EC measured turbulent heat and carbon dioxide fluxes for a central business district (CBD) of Shanghai, China are presented. Given complexities introduced by the variability of the building heights in the study area, data are analysed by wind direction and local- and micro-scale fluxes are considered separately.
At the local scale, the median daily peaks of sensible heat flux (QH) occurred in the early afternoon (winter: 82, spring: 150, summer: 242, autumn: 125 W m-2). The latent heat flux (QE) was small in winter (median daily maxima 26 W m-2) and slightly larger in spring, summer and autumn (49, 68, 70 W m-2, respectively). The Bowen ratio reflected the dominance of QH, with monthly median hourly micro-scale Bowen ratios typically ranging between 1 and 4.5. At this site, with predominately impervious surface (85% buildings and pavement, 14% vegetation), the enhancement of evaporation following rainfall usually lasted for about 12 h. Consistently larger Bowen ratios documented at the micro-scale compared to the local-scale may be attributed to roughness effects and the effect of extensive areas of dry walls. The daily median CO2 flux was dominated by traffic emissions, with two peaks associated with morning and evening rush hours.
This research provides much needed data for little studied area of tall buildings, with important insights for understanding urban energy and carbon dynamics. Such data can inform urban planning strategies in the context of rapid global urbanization and climate change.
Distribution of Aerodynamic Roughness Based on Land Cover and DEM- A Case Study in Shanghai, China
1Shanghai Meteorological Science Research Institute, China, People's Republic of; 2Department of Meteorology, University of Reading, Earley Gate,UK
Aerodynamic roughness length (zo) and zero-plane displacement (zd) are two of the most important parameters to describe turbulent exchange processes between the surface and atmosphere. Here we consider different approaches to estimate these parameters for Shanghai. ASTER GDEM data, Landsat ETM+ data and measured building heights in the downtown area of the city were used to obtain the surface height and land use type for the entire Shanghai city. The aerodynamic roughness length for momentum (zo) and Zero-planedisplacement length (zd) were derived using morphometric methods with GIS databases. In the central urban area, zo and zd were calculated with the DEM data given the significant variations in building height. While in the suburban area, zo and zd were determined according using assumptions linked to land use types.
Under gale force winds, which are likely to be associated with neutral stability, we can use the logarithmic wind profile model to assess the influence of the surroundings on the wind parameters. In Shanghai with its relatively flat terrain, observations are available at a number of different heights above the ground (10, 30, 50, 100, 400, 700, 1000, and 1300m) at several meteorological sites. Because of the varying measurement footprints, a series of zo(zd) values were used for different heights as the input of the model. The series of zo(zd) values represented the spatial average values of circles with different radii (100, 200, 500m, 1km, 2km,5km and 10km) centered on each meteorological site. The simulated wind speed and the met-tower/wind profiler measured values were compared to obtain the most suitable zo(zd) to calculate the most realistic wind speed for Shanghai.
The spatial distribution of aerodynamic roughness(zo, zd) can significantly affect the material and energy exchange between the surface airflow and the underlying surface especially for mega cities such as Shanghai, and the application of aerodynamic roughness to derive wind speed under neutral weather conditions is very useful for strong wind forecasts and wind disaster prevention.
Comparison on Different Methods to estimate Aerodynamic Parameters in Urban Areas
1Shanghai Meteorology Science Institute, China, People's Republic of; 2Department of Meteorology, University of Reading, Reading, RG6 6BB, UK
A number of different methods to calculate aerodynamic roughness parameters are evaluated for a site with tall buildings (> 39.5 m mean height) located in Xujiahui area of Shanghai. The methods use both observations (e.g. temperature variance method (TVM, Rotach, 1994), standard of wind speed method (Su, Beljaars, 1987), eddy co variance method (Es, Grimmond, et al., 1998)) and GIS database (e.g. Ra method (Raupach, 1994) and Kanda method (Kanda, et al., 2013 )). Tower mounted cup anemometer and ultrasonic anemometer data were analysed for the period from December 2012 to November 2013. The geometric data were collected for an area with a 500 m radius centered on the Xujiahui tower. The results show the influence on uniformity of building height and density on the TVM derived results. The Ra and Kanda methods both show similar variations for zd and z0 by wind direction. The same performance in z0 is evident for the Es and Su methods. There are obvious differences both in values and patterns of variation for the aerodynamic methods and morphometric methods. The most important factors influencing the TVM, Es method and Su methods are different. The values of zd calculated by the TVM method are proportionate to parameter C1, inversely proportional to the parameter C3 and effected by wind speed obviously. The z0 values calculated by Es method and Su method are inversely proportional to zd. These results have implications for more attention about the effect both in source area and parameters in aerodynamic methods, and better consideration of uniformity of building height and density for morphometric methods.
Analysis of Suspect Meteorological Data from Quality Control Process in Urban Area
Shanghai Meteorological Bureau, China, People's Republic of
In basic quality assurance (QA) procedures, samples fail the persistence test and step test usually, named dead band suspect samples and sudden change suspect samples. They are possible the result of small-scale perturbations, and can reflect important information of environment and weather systems. Studying these doubtful cases may be beneficial to improving the performance of a QA system and making the most of information derived from data in urban areas. Basic QA procedures are applied to hourly temperature observations (May in 2010 to April in 2011) of 18 automatic surface weather stations (AWS) in a highly urbanized area (Shanghai Expo). The distributions of suspect samples are shown and possible causes are investigated. The results show that dead band suspect cases can last for 11 hours maximum and occur at isolated stations. Most of them are more likely to be observed at shielded and blocked stations in cloudy winter evening because the sensible heat flux is low in this context. The sudden change suspect cases consist of two subsets: sudden rise cases and sudden drop cases. The former cases are more isolated than the latter ones. The sudden rise cases mostly occur around sunrise in autumn and winter morning, while the sudden drop cases mainly in spring and summer afternoon and evening. In autumn and winter morning, the increasing solar radiation heats the ground and certain stations warm up dramatically or vice versa at sunset in spring and summer. In addition, the sudden heavy precipitation in the afternoon causes dramatically cooling at stations. Therefore, multiple cross-checks are required when some samples from urban stations fail the QA test.
Investigation of temperature inversions in different conditions in Tomsk according to MTP-5 temperature profiler and the mesoscale Weather Research and Forecasting (WRF) model
1National Research Tomsk State University, Russian Federation; 2Institute of Monitoring of Climatic and Ecological Systems of the Siberian Branch of the Russian Academy of Sciences (IMCES SB RAS)
The classical method of retrieval information on the vertical structure of the atmosphere is based on the application of radiosondes measuring the atmosphere to altitudes of about 40 km. However, aerological observations providing valuable information for large-scale models of the atmosphere have insufficient resolution for measuring of its thin structure. One of the most efficient methods of obtaining such information is the application of an МТР-5 meteorological profilers that meet high requirements imposed on the spatiotemporal resolution at altitudes from 0 to 1000 m .
At the international Bogashevo airport in Tomsk, a refined MTP-5PE microwave temperature profiler with expanded range of temperature measurement and higher spatial resolution is installed.
Exact and regular data on the state of the lower layer of the atmosphere are also necessary in connection with the increased requirements to the quality of meteorological information not only for aviation but also for other consumers. Data on temperature inversions in the vicinity of Tomsk on the basis of MTP-5PE profiler data carried out at the IMCES SB RAS were summarized.
The forecast of winter temperature inversions is performed using of the mesoscale meteorological model WRF, version 3.4.1 for conditions of town Tomsk. The results of the forecast of air temperature at altitude are presented. Model based calculations were made at Tomsk State University claster «SKIF CYBERIA». The forecast of air temperature at different altitudes in the lower troposphere was carried out for three dates: 12.13.2012, 01.26.2013, 02.26.2014. These dates are different from each other by different meteorological conditions.
It’s the first time that data on temperature inversions in the vicinity of Tomsk were summarized on the basis of MTP-5PE profiler data. A few characteristics of inversions observed in the region of the Bogashevo airport are presented. It is shown that during persistent long-lived powerful anticyclones there is high recurrence of temperature inversions - they occur every day, or 90% of the time.
Results of numerical calculations showed that the vertical profiles the air temperatures in the lower part of the atmospheric boundary on the basis of a МТР-5 meteorological profilers and calculated on claster «SKIF CYBERIA» with use of the models of high resolution have the high level of quantitative and high-quality coincidence of results.
The findings of the lower atmosphere are important in the following cases: a reliable supply of air flight at the international airport Tomsk; monitoring of air pollution; assessment of urban heat island and its multifaceted influence.
This work was performed by order of the Ministry for education and science of the Russian Federation No. 5.628.2014/K
Characterising internal boundary layers forming over an idealised urban surface based on air temperature observations with high spatio-temporal resolution
1Tokyo Institute of Technology, Japan; 2University of Reading, UK
Boundary layer dynamics do not only impact the climate conditions experienced by people living in urban areas, they also contribute to the transport of pollutants. Internal boundary layers forming over the rough urban surface may separate areas of different air quality levels so that an improved understanding of these boundary layer structures has great potential to aid the interpretation of mixing processes within and above the urban roughness sublayer.
Several studies have used time-averaged statistics to define different boundary layer characteristics. This study, focuses on the “instantaneous boundary layer height”, defined as the height of strongest negative temperature gradient. High spatio-temporal resolution measurements of air temperature were conducted at the Comprehensive Outdoor Scale Model Experiment for Urban Climate (COSMO) over a period of 4 month. Totally, 60 thermocouples were aligned vertically (with a spacing of 0.2 m between 0 - 8 m), and sampled every 50 Hz. This gives clear images of time-height distribution of temperature fluctuations. The data provide insight into multi-layer structures of internal boundary layers forming over the idealised urban surface of COSMO during daytime and nighttime. Such information can be valuable for the evaluation of high-resolution models using similar simplified surfaces. It is analyzed how conditions vary with atmospheric conditions. The instantaneous boundary layer height statistics are compared with the conventional turbulent statistics and spectra of turbulent velocities from sonic anemometer measurements conducted simultaneously along the same vertical profile.
Estimation of roughness parameters of urban area using wind profile data obtained by a Doppler lidar system
Meteorological Research Institute, Japan
Vertical profiles of horizontal wind speed in urban area of Tokyo, where is surrounded by many types and heights of buildings, were obtained using a Doppler lidar system. We tried to estimate roughness length and zero plane displacement height by the non-linear least square fitting method with 10 minutes mean profiles fit to the theoretical log-law wind profile. 936 profiles were obtained during 6 days observation period, and 132 profiles of them were adopted without calculation divergences. As the results, the roughness length and the zero plane displacement height around the site were estimated to 0.60±0.88m and 14.8±8.8m (above the rooftop of 12m, i.e. the estimated displacement was 26.8±8.8m above the ground and was very higher than 7.2m of the mean height of the surrounding buildings), respectively. The roughness length and the zero plane displacement height derived by another geometrical estimation method (Kanda et al. 2013) using the building floor information of GIS database of the Tokyo Metropolitan government, were estimated to 0.74m and 31.7m, respectively. The estimated roughness length was in the same order with many previous studies. However, the zero plane displacement heights estimated by two individual methods were seemed to be very different from the values of previous studies.
Monitoring of atmospheric turbidity and cloud above Tokyo using ground based network cameras
1Chiba Institute of Technology, Japan; 2National Defense Academy of Japan, Japan; 3Meteorological Research Institute, Japan
Several mega-cities are faced to open seas, and the atmosphere above the cities is well influenced by sea via sea/land breeze circulation. Furthermore, a drastic change of the surface roughness from sea to land, and a gap of atmospheric temperature and water content easily invoke a cumulous cloud. To address these events, we constructed ground-based camera network around Tokyo-Bay to monitor the atmospheric condition, especially clouds and atmospheric turbidity, above Tokyo and Tokyo-Bay.
The cameras were installed at 4 locations around Tokyo-Bay; Inage yacht harbor, Tokyo Institute of Technology, Kisarazu city hall, National Defense Academy of Japan. Each location includes 3 cameras directing to different horizontal directions. The camera images were stored every 1 minute, and they were transferred to a server using internet. This system has been operated for 2 years.
In this study, we apply a set of sky images to examine (1) development of cumulous cloud and, (2) diurnal and seasonal variations of atmospheric turbidity. During the measurement period, one cumulous cloud was monitored at two different locations. These stereo images allow determining the horizontal location of this cloud, and also the height of the cloud top. In addition, the speed of the vertical development of this cloud was examined by using sequential images.
We can also see a clear dependence of atmospheric turbidity, which is estimated from the camera images, on the wind direction since the south wind transport more turbid air from industrial district and cars, which are many in the southern coastal area of Tokyo.
Microclimatology of Tropical University Campus: In-situ measurement and GIS-based analysis
UNIVERSITI TEKNOLOGI MALAYSIA, Malaysia
A conducive and comfortable environment in a university campus is an essential aspect in supporting higher educational learning, and even so in a tropical environment. In Malaysia, rapid development has taken place in the university and its vicinity, especially in the urban area. Given the high population growth, lack of development lands, and poor urban planning made the development in the campus and its buffer remained in a non-sustainable manner. Quantification of microclimate in an urbanized university remains elusive especially in an equatorial region. Therefore, this study aims at providing better insight into the in-situ measurement and Modern Geographical Information System (MGIS) approach particularly in analysing the effect of urban surface land cover towards microclimate pattern in the university campus. The area is surrounded by governmental offices, residential area and situated about four kilometres away from the city centre of Kuala Lumpur. It affects changes in the essential climatic variables such as ambient air temperature, relative humidity, surface temperature, solar radiation, wind speed, and wind direction. The field measurement will be carried out for four weeks in December 2014. The instruments will be installed at approximately two meters above ground level at different locations in the campus to record the climatic variables within 10 minutes data sampling interval. The recorded climatic variables data will be stored and analysed using MGIS and the pattern of climatic variables will be critically discussed. The climatic variable patterns from the GIS application provide indicative in-situ campus environment and a step forward to have a better planning for sustainable campus. This study benefits urban planners and decision makers in the university for the development of sustainable campus in the near future.
Status and Future of the WISE Urban Meteorological Observation Network
Weather Information Service Engine, Korea, Republic of (South Korea)
For the purpose of scientific understanding in urban meteorology and implementation of these advances to improvement of high-resolution meteorological models applicable to the Seoul Metropolitan area, the Weather Information Service Engine, or WISE, meteorological observation network is proposed and now under installation. The WISE observation network includes the surface energy balance network, and surface-based 3-d meteorological networks consist of wind lidar, radiometer, aerosol lidar, and ceilometer as well as the existing surface-based meteorological observation netwok. The sites for the former network are determined by different thermal climate zones such as residential, commercial, mixture of residential and commercial, river, forest, rice paddy, etc. and those for the latter are determined by horizontal distributions of the topography and land covers. The WISE meteorological observation network will be installed during 2013 to 2015, and will be transferred to be the permanent network in 2018 after data checks and experimental studies during 2016 to 2017. Finally, the quality controlled WISE urban data will be served to researchers in field of air quality, environment, electricity, etc. as well as urban meteorology.
Cooling mechanism of leaves of urban vegetation
Chiba University, Japan
Urban vegetation shows low surface temperature when we see the thermal infrared images of urban surface data. One of the reasons of the low temperature is considered as the evaporation from the vegetation. Another important reason is high heat exchange between air and the vegetation. The temperature of leaves shows similar variation with air temperature.
In this study, heat transfer coefficients of different size of leaves were measured. By solving two energy budgets equation where one equation for non-evaporative leaves and one equation for evaporative leaves, heat transfer coefficient of the leave can be obtained. Measurements were also done for non-evaporative and evaporative leaves simultaneously and three sizes of leaves were measured.
As a result, small leaves shows higher heat transfer coefficient although there were varieties of values with the variation of environment. These value can be used for the whole tree model and whole urban model with vegetation to clarify the cooling mechanism of urban vegetation.
Estimation of effective roughness length for suburban area of the city of Zagreb
Meteorological and Hydrological Service of Croatia, Croatia
Three methods are presented to estimate the effective roughness length zeff of inhomogeneous suburban area of the city of Zagreb (Croatia). The first method is based on root mean squared errors (RMSE) between estimated and corresponding measured values of wind speed at 2 m above ground. In the second method the relationship between the standard deviation of wind speed at 10 m height and zeff is used while the third approach takes into account the relationship between the median of wind gust factor at 10 m height and zeff. One of the more important results here is the classification of zeff according to wind direction; zeff values obtained are higher for western than for eastern quadrants of wind direction, what is in accordance with inhomogeneous (regarding surface roughness) studied suburban area.
Ceilometer based retrieval of Shanghai’s boundary layer height
1Shanghai Institute of Meteorological Science, Shanghai Meteorological Bureau, People's Republic of China; 2Department of Meteorology, University of Reading, UK
To understand the boundary layer processes within the coastal megacity of Shanghai the height of the boundary layer (BL) is of interest. Five methods were used to determine boundary layer height:
(a) analysis of observations from Vaisala CL-51 ceilometer backscatter data using a modified (Steyn et al., 1999) ideal curve fitting algorithm (m-IC). The m-IC method differs from the original Steyn ideal curve method in that instead of using a single initial estimate, values at every height below 2 km are used to fit the curve that best fits the original data.
(b) analysis of observations from Vaisala CL-51 ceilometer backscatter data using Vaisala’s BL-View/CL-51 software which use the gradient method (v-GM);
(c) a further modification to the m-IC algorithm (m2-IC) to consider more complex conditions that had been targeted and sorted based on the thorough checking of retrieved results. For example, when cloud occurs at very low altitude m-IC will consider the height of cloud top as ABLH, but m2-IC will consider the height of cloud base as ABLH. And when thick aerosol layer occurs above ABL, m-IC will consider the top of aerosol layer as ABLH, but m2-IC will consider the height where backscatter decrease sharply (using threshold or gradient as indicator) for the first time as ABLH.
(d) analysis of radiosounding data (temperature and humidity) (TH-RS); and
(e) analysis based on the Nozaki (1973) method which uses meteorological variables (N-MV)
The m-IC and v-GM retrieved values have good agreement when the boundary layer has a sharp decrease of backscatter creating a clear well-formed boundary. This is generally equal to the height with maximum gradient (v-GM). Also equal to the height to get best fitting curve (m-IC). ) However, there are relatively large differences under other conditions. The N-MV were compared with the TH-RS at 14:00 local time for Baoshan area of Shanghai, when the boundary layer is most likely to have mixing occurring. At this time there is strong agreement between methods. This indicates that the m-IC and m-IC2 algorithms are able to capture the boundary layer height. Given this the method was applied to other ceilometers installed in Shanghai. These data are used to investigate Shanghai boundary layer between September 2013 to August 2014. In this talk the details of these methods, analysis and the nature of new understanding of the ABL in this coastal megacity are presented.
1) D. G. Steyn, M. Baldi, and R. M. Hoff, 1999: The Detection of Mixed Layer Depth and Entrainment Zone Thickness from Lidar Backscatter Profiles. J. Atmos. Oceanic Technol., 16, 953–959.
2) Nozaki K Y,Mixing Depth Model Using Hourly Surface Observations Report 7053,USAF Environmental Technical Applications Center,1973.
A study on data analysis of densely observed climate variables in Seoul
1Weather Information Service Engine project of KMA, Korea, Republic of (South Korea); 2Social Eco-Tech Institute, Konkuk University, Seoul, Korea, Republic of (South Korea); 3National Institute Meteorological Research, KMA, Korea, Republic of (South Korea)
Recent studies showed the increased of high resolution modeling for local climate analysis. As the models equipped with higher resolution inputs, the resultant outputs can describe detail climate variables over space and time. However, this would follow validation such as intensive field campaign, massive installation of the weather observations, and networks for optimization and evaluation. That is, high resolution urban climate modeling requires objective, descriptive, and dense observation network for validation. Many studies showed that descriptive observations of climate variables (e.g. temperature, humidity, etc.) is essential for the understanding of the physical knowledge of urban climates such as surface-atmosphere exchanges of momentum, heat, water and other gases. However, it requires huge amount of budget and efforts. Recent in Korea, commercial company offers real-time information on extreme weather events such as localized heavy rain, heat wave, and typhoon by utilizing mobile phone base stations to collect weather data. The installation of Automatic Weather Stations in Seoul City is expanding; AWS network to include Incheon and Kyeonggi area, with plans to have around 1,100 AWS with an interval of 1~3km in the entire Seoul metropolitan area (weather planet). The purpose of this study is to analyze the densely installed and observed climate variables for the understanding of the physical property of Seoul climates and used it for the validation of CAS (climate analysis Seoul). We investigated the dense AWS data in Seoul with a statistical approach. In addition, we developed urban geometry based canopy parameters. Then, we compared AWS data with urban canopy parameters such as geometry base roughness length. Initial results showed the AWS data can describe the Seoul canopy condition better in terms of wind speed. Preliminary results showed the geometry based roughness length is closely correlated with wind speed derived from AWS. The wind speed decreased as the roughness length increased, which is linear both day time and night time. Additional analysis will be followed for the physical knowledge of urban climates in Seoul Metropolitan Area.
A three years long fieldwork experiment to monitor the role of vegetation on the urban climate of the city of Strasbourg, France
1ICube Laboratory, UMR 7357 University of Strasbourg - CNRS - INSA Strasbourg, France; 2PIAF Laboratory, UMR 547 University Blaise Pascal - INRA, France; 3ASPA Alsace, Strasbourg, France
The ICube Laboratory (UMR 7357 University of Strasbourg - CNRS), in collaboration with the PIAF Laboratory (UMR 547 University Blaise Pascal - INRA) and the local association for atmospheric pollution monitoring (ASPA), has initiated in 2013 a fieldwork experiment to measure and monitor the urban climate of the city of Strasbourg, France, with a particular focus on the role of vegetation with respect to micro-climatic conditions suitable for human comfort. This fieldwork experiment is organized around four complementary objectives. At first, a detailed analysis of the spatial and temporal variability of the urban heat island effect is conducted through the deployment of a network of twenty-three weather stations in and around the city, monitoring standard parameters such as air temperature and humidity, as well as wind speed and direction. This network also contributes to the European INTERREG IV project “Atmo-IDEE”. Secondly, to allow for an in-depth analysis of the physical processes controling the UHI, two sites have been equipped with a set of radiometers and eddy correlation sensors to measure the radiative and energy balance. The first site, located in a densely urbanized area, can be considered as mineral and has a large footprint since the sensors are installed 30 meters above ground. The second site is located in an urban park near the city centre, and is equipped with the same set of instruments, here on top of a 20 meters high mast. The later site is used to fulfil the third objective, which is to closely keep track of the contribution of the vegetation to turbulent fluxes measured on top of the urban canopy. To do so, a group of six trees is equipped with sap flow sensors. Simultaneously, other sensors are monitoring the soil temperature and water content at seven levels, as well as the photosynthetically active radiation profile below, inside and on top of a tree. Additionally, the contribution of the soil and grass is measured during intensive observation periods using a closed transpiration chamber. The last objective of this experiment is to measure thermal comfort indices, combining integral radiation measurement methods, black globe thermometers, 38 mm flat globe thermometers and a dense set of twenty weather stations (UBIQUITY auto-communicating network). The entire experimental design is presented together with first results.
Development of a Dense Climate Monitoring Network for the Georgia Institute of Technology
Georgia Institute of Technology Urban Climate Lab, United States of America
The physical context of the Georgia Institute of Technology campus is changing. In response to both global and local scale climate change, temperatures in the Atlanta region have been rising more rapidly than in previous decades. An analysis of urban and proximate rural temperature trends in major US cities finds Atlanta to be the third most rapidly warming metropolitan region in the country. The recently released National Climate Assessment finds the southeastern US to be experiencing a more rapid increase in heat index values than any other region of the country, with the annual number of extreme temperature days expected to more than triple by mid-century. With an increase in the incidence of extreme heat during the warm season, and higher temperatures generally throughout the year, the Georgia Tech campus and population is increasingly vulnerable to a growing range of health, outdoor comfort, and infrastructure-related impacts. More effective monitoring of climate trends on campus, in concert with climate-responsive design strategies, can lessen both the human impacts and infrastructure costs of rising temperatures. As a result, the Georgia Institute of Technology's Urban Climate Lab has established a dense network of temperature and relative humidity sensors throughout the campus and adjacent neighborhoods to determine the location of hot spots on campus, the impact of ongoing development influencing micro-climatic conditions and in turn how these conditions impact building energy consumption, and the effectiveness of specific climate-responsive design strategies in moderating temperatures on campus. The network consists of 25 HOBO sensors across the entire campus, representing many micro-climatic conditions including both 2-meter and rooftop locations. The selected rooftops represent a variety of albedo and heat mitigation techniques. Several sensors are located in areas scheduled to convert from impervious surfaces to green space, and will therefore record the impact of this transition. This data will become publicly available as it is collected. This study is the first of its kind for a US university, and lays the groundwork for the establishment of a more extensive network across the Atlanta metropolitan region.
Examination of empirical parameter in the thermal image velocimetry
Tokyo Institute of Technology, Japan
Thermal image velocimetry is a method to measure the two-dimensional velocity distribution from the time-sequential thermography with image processing technique. This method has used to examine the thermal updraft along a building wall, and detect a dust devil in a sports ground surrounded by residential buildings. Therefore, this method has a potential to evaluate the micro climatological process in urban area.
In a technical perspective of this method, we assume that moving velocity of a coherent pattern of surface temperature, which is directly measured from the sequential surface temperature images with image process, has linear relationship with the wind velocity close to the object’s surface as observed in the previous experiments. We examined this assumption based on a simultaneous measurement of surface temperature and wind velocity using thermal infrared camera and sonic anemometer.
A new Sky Arrow ERA light aircraft combining LIDAR and air quality payloads for atmospheric monitoring
1National Research Council, Institute for Agricultural and Forestry Systems in the Mediterranean (Cnr-Isafom); 2National Research Council, Institute of Atmospheric Sciences and Climate (Cnr-Isac); 3National Research Council, Institute of Biometeorology (Cnr-Ibimet)
Detailed observations of the atmosphere and its pollutants, especially in the entire Planetary Boundary Layer (PBL), are of fundamental importance to assess and improve air quality models, design more effective observing strategies for ground networks, and inform policy makers.
The use of aircraft is a valid way to retrieve these data, allowing investigation of heterogeneous landscapes containing a diverse mixture of air pollution sources that include urbanized areas, transportation pathways, industrial plants, agriculture and natural vegetation. Light aircraft may achieve the best compromise between observational capabilities and operational costs being an attractive solution to perform operational monitoring actions at the level of large cities and metropolitan areas.
In this work we present a new version of the Sky Arrow ERA (Environmental Research Aircraft) that is currently being used for intensive measurements in Campania region and Naples city over areas with population density among the highest worldwide.
The Sky Arrow is a two seat aircraft made of carbon fiber, having a cruise flight speed of 40 m/s and an endurance of 3.5 hours, covering flight distances of up to 500 km and reaching altitudes between 10 and 3500 m.
The in-situ payload is composed by a Mobile Flux Platform (MFP), which is capable of deriving the 3D wind vector at 50 Hz by measuring angles of attack with a pressure sphere and using aircraft attitude data retrieved with GPS and INS (Inertial Navigation System); CO2 and water vapor densities are measured at 50 Hz by an infrared gas analyzer (Licor 7500); particles are measured on 32 dimensional classes with an Optical Particle Counter (Grimm mod. 1.109); Nitrogen Oxides (NOx) are measured by an absorbance sensor (2BTech mod. 405) and Ozone (O3) by an UV monitor (2BTech mod. 202).
The novelty of this platform is the integration of the in-situ payload with a compact LiDAR remote sensing system capable of retrieving vertical aerosol profiles and atmospheric optical properties with high spatio-temporal resolution. The source is made by a dual wavelength (532 and 1064 nm) pulsed laser, with an output energy up to 200 µJ per pulse at 1000 Hz. A polarizing beam-splitter separates the collected 532 nm signal into two polarized components parallel and perpendicular to the laser emission.
The first data from operational flights for air quality monitoring will be presented, that were collected to: i) estimate city-level emissions to validate emission inventories; ii) assess local and mesoscale circulations in coastal areas with complex terrain; iii) validate and improve dispersion models used for air quality forecasts.
3D tree architecture modeling from laser scanning for urban microclimate study
1ICube Laboratory UMR 7357, University of Strasbourg – CNRS – INSA Strasbourg, France; 2PIAF Laboratory, UMR547 University Blaise Pascal – INRA Clermont-Ferrand, France
The climatic conditions observed in cities are known to be dependent on the presence of urban vegetation. The evapotranspiration process of the vegetation produces a cooling effect and impacts the water and heat balances of urban areas. The project initiated by the ICube laboratory in collaboration with INSA Strasbourg and INRA Clermont-Ferrand aims to provide a better understanding of the impact of trees on the urban microclimate. This goal requires to investigate not only how trees cool the urban climate, but also to develop a 3D energy balance model of urban areas for monitoring heat fluxes. Obviously, to enrich the energy balance model, the knowledge of the canopy structure of urban trees is essential. A dedicated test area located in Strasbourg (France) has been selected for carrying out several microclimate measurements related to heat fluxes, surface temperatures, and also tree architecture metrics. For estimating the geometry of trees, usually manual techniques are used. Regarding automatic techniques, a state of the art enabled to highlight the potentiality of terrestrial laser scanning techniques for 3D modeling of trees.
Aim of this paper is to present a methodology developed for assessing the geometry of a tree based exclusively on terrestrial laser scanning measurements. A terrestrial 3D laser scanner enables the acquisition of millions of points located at the shape of the object and is used for a wide variety of applications, more commonly for building modeling than for tree modeling. After point cloud registration, a segmentation of the set of shoots is necessary. Then, a point cloud skeletonization methodology is performed. The processing chain provides a skeleton of the tree as well as a skeleton of every segmented set of shoots. Moreover, since the INRA team requires specific shoot’s metrics for leaf area reconstruction based on allometric relationships, the developed methodology has been improved to extract not only the skeletons composing the tree but also the shoot lengths and orientations. Experiments have been carried out on a silver lime tree located in the test area and laser scanner acquisitions have been performed at every season of the year. Results provided by our approach are better than expected, since the skeletons of more than 86% of the segmented shoots are automatically produced.
Keywords : Laser scanning, urban microclimate, tree modeling, skeleton, point clouds
Bulk Transfer Relations for the Roughness Sublayer Applied at a Sub-urban Area of Zagreb
Meteorological and Hydrological Service, Croatia
In the roughness sublayer (RSL), Monin–Obukhov surface layer similarity theory fails. This is problematic for atmospheric modelling applications over domains that include rough terrain such as forests or cities, since in these situations numerical models often have the lowest model level located within the RSL. Based on empirical RSL profile functions for momentum and scalar quantities, and scaling the height with the RSL height z∗, a simple bulk transfer relation that accounts for RSL effects has been developed by Koen De Ridder and published in Boundary-Layer Meteorology (2010) . To be verified the validity of that approach in Zagreb (Croatia) sub-urban area, these relations are employed together with wind speed and temperature profiles measured over that area during last few years to estimate momentum and heat fluxes. It is demonstrated that, when compared with observed flux values, the inclusion of RSL effects in the transfer relations yields a considerable improvement in the estimated fluxes.
Mapping urban ecosystem structure and function using hyperspectral imagery and airborne lidar
University of California, Santa Barbara, United States of America
In urban areas, high temperatures contribute to degraded air quality and increased demand for building climate control. In partial response, many cities are implementing the Urban Forest Effects (UFORE) model to estimate the extent to which trees modify climate and building energy use through direct shading and evapotranspirative cooling. The results of a traditional, sample-plot based UFORE study, however, do not allow for fine spatial resolution characterization of urban forest structure or the attendant climatic functions. In this research we use hyperspectral imagery and waveform lidar data to map urban forest species and leaf area index (LAI) in downtown Santa Barbara, California. We find that these advanced geospatial datasets allow for accurate species mapping (83.4% overall accuracy for 29 common species) and accurate estimation of LAI (r2=0.84, y = 0.99x) compared to field validation measurements. The resultant structural maps are then used as enhanced UFORE inputs to generate spatially explicit estimates of air pollution mitigation and building energy-use modification. This research will allow for improved urban forest management and more precise parameterization of urban energy balance and climate models.
Investigation of urban air temperature and humidity patterns during extreme heat conditions using satellite-derived data
National Center for Atmospheric Research, United States of America
Heat is a leading cause of weather-related human mortality in the United States and in many countries worldwide. The urban heat island (UHI) can magnify heat exposure in metropolitan areas. We previously quantified the accuracy of near-surface air temperature and humidity information derived from MODIS atmospheric profiles at 5 km resolution, and developed a new method—the urban heat island curve (UHIC)— to assess UHI intensity by integrating the urban surface heterogeneity into a curve that shows the relationship between air temperature (and dew-point temperature) and urban land use fraction. This study investigates the ability of the new MODIS-retrieved temperature and humidity dataset to depict urban heat patterns over metropolitan Chicago during summers (June-August) from 2003-2013. First, we corrected the mean biases of the dataset for four satellite overpasses, and the root-square-mean-error is deceased to 3 K or less compared with ground observations from 20 regional weather stations. Next, the clear-sky air temperature data were clustered into six predominant patterns using a self-organizing mapping (SOM) technique. Humidity information was grouped according to the temperature results. The pattern exhibiting the highest temperatures (and the corresponding humidity pattern) was compared with the 2003-2013 median conditions using the UHIC. We found the following: 1) during these hottest events, the air temperature and dew-point temperature over the study area increase most during nighttime, by at least 4 K compared to the median conditions; 2) the urban-rural temperature/humidity gradient is decreased as a result of larger temperature and humidity increases over the areas with greater vegetation fraction compared to those with greater urban fraction; 3) compared to median conditions, heat patterns grow more rapidly leading up to the hottest events, followed by a slower return to normal conditions afterward. This research provides an alternate way to investigate the temporal and spatial characteristics of the UHI, using a satellite remote sensing perspective. It has the potential to be applied to cities globally, and to provide a climatological perspective on extreme heat that complements the many case studies of individual events that have been previously performed. Better characterization of urban heat patterns will aid decision makers in mitigating the urban heat island and in preparing for more frequent and intense extreme heat events in the future.
Low cost air pollution sensors: New perspectives for the measurement of individual exposure?
1University Paris Diderot, Sorbonne Paris Cité - UMR CNRS PRODIG, Paris, France; 2PMCLab - University Pierre & Marie Curie, Paris, France
Air pollution is one of the main environmental concerns of the French (and others), especially due to its effects on health. In Paris, the levels of ozone and particles exceed each year the daily and annual European guidelines recommendations. Currently, pollution exposure is assessed at a regional scale for an entire population, depending exclusively on atmospheric conditions and emissions. However, the chronic exposure of each individual is depending on its time-activity patterns, its mobility and its time in different indoor environments.
The strong engagement of citizens on environmental pollution is increasing in North America and North and Western Europe (citizen projects, conferences...). At the same time, with the rise of open source and low cost sensors, new projects emerge on smaller air pollution sensors, portable or for the inside. In this context, this oral presentation focuses on the relevance and usefulness of these sensors in scientific studies. Could we use these sensors to obtain a finer knowledge of the individual exposure and the spatial variability of particles concentration?
We have tested several low cost particles and ozone sensors, at a price less than one hundred euros and a size smaller than some centimeters. After testing the sensors inside, we performed itinerant measurements in Parisian streets during various meteorological conditions. We will discuss the relevance of these sensors, and the comparison with more voluminous and more expensive approved sensors.
A development of mobile monitoring system for urban climatology
1National Institute for Environmental Studies, Japan; 2National Institute for Environmental Studies / Nagoya University, Japan
We developed a real-time mobile monitoring system on air quality and thermal environment at the city block scale. This system helps designing the city blocks to locally improve outdoor comfort and provides access to a high resolution spatio-temporal environmental database, which includes information on the fine-scale outdoor thermal environment, air pollution, magnetic field intensity, etc. Based on a citizen participation approach, this system provides an opportunity for citizens to collect data in the area where they live, work or exercise. To test and validate the system we performed several participatory experiments providing participants with portable sensors connected to their mobile devices through Bluetooth, who walked in the city blocks of interest and collected information on the surrounding them environments. The information was displayed on their mobile devices and uploaded to a server via WiFi in real-time. We also used this system during local sport activity events (Tokyo Marathon, Tsukuba marathon, etc.) to obtain physiological responses in participants to potential environmental exposure. Indeed, using this fine scale monitoring we could identify areas in city blocks with low air quality, which could be dangerous for continuing human health activity events and should be re-constructed.
Derivation of an urban materials spectral library through emittance and reflectance spectroscopy
1University of Reading, Department of Meteorology, United Kingdom; 2King's College London, Department of Geography, United Kingdom
The measurement of surface temperatures in urban areas is challenged by the three-dimensional form of the urban surface and its heterogeneity in material composition. Remotely sensed observations therefore provide important and increasingly detailed information about the thermal response of this complex land cover. Recent advances in thermal infrared remote sensing include the increased availability of airborne hyperspectral imagers (such as the Hyperspectral Thermal Emission Spectrometer, HyTES, or the Telops Airborne HyperCam and the Specim AisaOWL), and it is planned that an increased number spectral bands in the long-wave infrared (LWIR) region will soon be sampled from space at reasonably high spatial resolution (by imagers such as HyspIRI). Detailed LWIR emissivity spectra are required to best interpret and evaluate the observations made from such systems.However, urban construction materials are not yet particularly well represented in current spectral libraries. While differences between natural and artificial materials are fairly well understood, only a few studies have been concerned with the diversity of long-wave spectral properties of anthropogenic materials.
A new online spectral library of urban construction materials (http://www.met.reading.ac.uk/micromet/LUMA/SLUM.html, Kotthaus et al., 2014), combining LWIR emissivity spectra and matching short-wave (VIS-SWIR) reflectance spectra for each urban sample will be presented. LWIR spectra are derived using measurements made by a portable Fourier Transform InfraRed (FTIR) spectrometer. FTIR emissivity measurements need to be carefully made, else they are prone a series of errors relating to instrumental setup and radiometric calibration, which here relies on external blackbody sources. The performance of the laboratory-based emissivity measurement approach applied here, that in future can also be deployed in the field (e.g. to examine urban materials in situ), is evaluated.
Examination of the characteristic LWIR and VIS-SWIR spectral signatures may improve identification and discrimination of the various urban construction materials, given the frequent overlap of chemical/mineralogical constituents. Hyperspectral, or even strongly multi-spectral, LWIR information appear to be especially useful, as many urban materials are composed of minerals with distinct reststrahlen/absorption effects in this spectral region.
Kotthaus, S, TEL Smith, MJ Wooster, and CSB Grimmond 2014: Derivation of an urban materials spectral library through emittance and reflectance spectroscopy, ISPRS Journal of Photogrammetry and Remote Sensing, 94, 194-212.