NOMTM6 (cont): Urban Climate measurement networks
Climate moderation via green infrastructure – the potential to mitigate the UHI effect in Dar es Salaam
1University of Manchester, United Kingdom; 2Ardhi University, Dar es Salaam, Tanzania; 3Manchester Metropolitan University, UK
Regulating urban ecosystem services can have an important role for offsetting the higher temperatures which tend to be associated with urban compared to rural areas. In the rapidly developing cities of sub-Saharan Africa, there is relatively little knowledge about phenomena like the Urban Heat Island effect and even less about intra-urban temperature variations. Similarly, evidence of the potential of regulating ecosystem services is also scarce.
This paper analyses temperature observations made at 64 fixed locations across two transects of northern Dar es Salaam, Tanzania. The city is situated on the eastern coast of Africa (6°48’S 39°17’E) and has a population over 4.3 million. Dar es Salaam’s climate is generally hot and humid throughout the year, with an average temperature of 29°C and peak temperatures occurring during the austral summer (December-February). The city centre benefits from its coastal location but development can block the cooling effect of sea breezes.
Dar es Salaam can be characterised as having 11 high level Urban Morphology Types (UMTs). These, and 43 detailed UMTs, have been mapped for 2008 and 2002 for the wider administrative area (1502 square kms). Residential UMTs cover 46.5% of Dar es Salaam, followed by agricultural UMTs (40.4%) and a further 5.1% of the land area of the administrative zone is associated with other predominately vegetated UMTs. Important vegetation also exists outside predominantly green UMTs and proportional cover varies between classes. For example, condominium residential types contain 58% vegetation on average, compared to 42% in areas of mud/wood construction (often associated with low income settlements).
Air temperate data was collected using ibutton sensors over seven months (June 2012 - Jan 2013). This included the main dry season (June to September/early October), and the period of short rains termed “vuli” in Swahili (from October to December/ early January). Data were analysed against a rural reference point in Kibamba, located 24 km from the city centre (and at approximately 152m a.s.l). The results showed an elevation-adjusted nocturnal air temperature UHI intensity of up to 2°C in August 2012. Additional analyses were carried out in relation to urban morphological characteristics of the study sites, including the relative proportions of 11 different vegetated land cover types around the monitoring sites (such as large trees, small trees and shrubs, crops, bare ground, housing and other built surfaces). Development pressure is high and vegetation is rapidly being lost from both the peri-urban and urban core areas. Such changes have serious implications for enhancing the already evident UHI effect.
The research was funded through the EU CLUVA project (www.cluva.eu).
HIGH-RESOLUTION URBAN HEAT ISLAND MEASUREMENTS AND ELECTRICITY APPLICATIONS IN BIRMINGHAM, UK
University of Birmingham, United Kingdom
The Urban Heat Island (UHI) is one of the most well documented phenomena in urban climatology. Although a range of measurements and modelling techniques can be used to assess the UHI, the paucity of observations in urban areas is a significant limitation for many studies. As such, many UHI studies would benefit from high resolution air temperature data. Presently the only feasible way in which this can be achieved is by the use of dense sensor networks which are now becoming increasingly common in cities across the world. Indeed, this availability of such high resolution data is now enabling urban climate impacts to be investigated at an unprecedented granularity. This study investigates the spatial relationship between air temperature data obtained from the Birmingham Urban Laboratory, UK with electricity consumption data from across the city. In particular, the study highlights the added impact of the UHI during heatwave events on electricity consumption, when demand for fans and air conditioners is increased. The paper concludes by identifying the potential role of such networks in helping to forecast future electricity demand in cities.
Shanghai’s Urban Integrated Meteorological Observation Network (SUIMON): case studies of applications
1Shanghai Institute of Meteorological Science, Shanghai Meteorological Service, CMA,China, People's Republic of; 2Department of Meteorology, University of Reading, Earley Gate, PO Box 243, Reading, RG6 6BB, UK
Observations of atmospheric conditions and processes in cities are fundamental to understanding the interactions between the urban surface and weather/climate, improving the performance of urban weather, air quality and climate models, and providing key information for city end-users (e.g. decision-makers, stakeholders, public). Shanghai is one of a small group of cities with urban stations with long (>100 years) continuous records (Gherzi, 1950) (in Shanghai dating back to 1872). Today in Shanghai, there are a series of networks of different instrument types (e.g. automatic weather stations , weather radar, Met-towers, wind profilers, lightning mapping systems, remote sensing systems) that provide dense observations through a network of networks, referred to here as SUIMON (Shanghai’s Urban Integrated Meteorological Observation Network). In this presentation, an overview of Shanghai’s urban integrated meteorological observation network (SUIMON) will be presented, with examples of applications ranging (1) the heat island, sea breeze and convective weather, (2) photochemical and urban aerosol pollution, and (3) urban winds. The design and operation of the network, and the urban climate services it does and can support, are relevant to cities worldwide.
The Urban Heat Island of a middle-size French city as seen by high-resolution numerical experiments and in situ measurements – the case of Dijon, Burgundy
CRC/Biogéosciences, CNRS, France
This work aims at characterizing the spatio-temporal variability and features of the urban heat island (UHI) over the agglomeration of Dijon (north-eastern France; 260,000 inhabitants) under present-day conditions and during the boreal summer season (June through September). To that end, two complementary approaches are used:
• in situ measurements, using a network of 50 Hobo proV2 sensors measuring air temperature and specific humidity every 20 minutes, and implemented since June 2014 throughout the agglomeration;
• high-resolution (150m horizontal resolution) meso-scale atmospheric simulations performed using the WRF/ARW model coupled with the BEP-BEM urban canopy model.
Special attention was paid to the location of the thermometers. The sites were chosen to ensure a correct sampling of the various urban thermal environments such as described by the classification of Oke (2006). In order to ensure a representativeness of the neighbourhood and not merely the close environment, open locations are preferred, limiting shadows from the vegetation and nearby buildings. The sensors are fixed 3m above the ground surface, over the south face of public lampposts, with specific fixations designed to separate the measurements from the lampposts themselves. The density of our network enables us regionalizing in detail air temperature and humidity over the whole city.
Similar attention was also given to the static surface datasets used as surface boundary conditions for the climate modelling system (land-use maps, topography, urban morphology). Public and/or open databases developed by various French and European governmental services (Corine Land Cover, IGN, INSEE and OpenStreetMap databases) were used in order to obtain a generic and reproducible methodology, that can be used for any French city.
This presentation is the opportunity to first present the comparisons between both approaches and therefore quantify the capability of the climate modelling system (WRF/ARW - BEP+BEM) to simulate the main features of the UHI in Dijon during the 2014 summer period.
Urban climate monitoring system suitability for intra-urban thermal comfort observations in Novi Sad (Serbia) – with 2014 examples
1Climatology and Hydrology Research Centre, Faculty of Science, University of Novi Sad, Serbia; 2Department of Climatology and Landscape Ecology, University of Szeged, Hungary
In 2014, urban climate monitoring systems were established in two neighboring European cities (Novi Sad, Serbia; Szeged, Hungary) based on Local Climate Zones (LCZ) classification system, GIS model calculations and field work. In the built-up area of Novi Sad (55 km2) 7 LCZ types and 2 LCZ land cover types in nonurban environment in the vicinity of the city were delineated.
Urban climate monitoring system in Novi Sad consists of 27 stations equipped with air temperature and relative humidity sensors distributed across all LCZs. This system provided 10-minute measured temperature and relative humidity data, as well as calculated human comfort (Psychologically Equivalent Temperature - PET) index values since June 2014.
Suitability of the developed monitoring system for human comfort observations in different built-up areas of the city and its surroundings was investigated. Preliminary results showed that during summer months heat waves PET index had surplus values (>6°C) in highest built-up types of the city (midrise LCZ type) compared to the nonurban areas (LCZ D – low plants), while human thermal comfort differences among other built-up LCZs were smaller. Also, largest differences occurred during evening and nocturnal hours.