Abstract
Abstract. Urban areas are treated as a single entity by mesoscale urban canopy models (UCM) for assessing the influence of urban morphology on climate. Weather Research and Forecasting Model (WRF) coupled with UCM along with urban physics options to describe the urban features such as Single Layer Urban Canopy Model (SLUCM), Building Energy Parameterization (BEP) and Building Energy Model (BEM) which enumerates the influence of urban features on the local scale other than the bulk parameterization (no urban physics option), which is generally used in most of the operational forecasting models. Besides, WRF model also enables to integrate multi-class Urban Land Use Land Cover (LULC) whereas most of the globally available LULC depict urban area as single urban built-up class. This study aims to analyze performance of high resolution urban LULC and urban physics options for Chandigarh area by downscaling climatic variables up to 1km and its validation with the ground observation data. The inner domain (1 km resolution) was configured with default LULC for one set of simulations and multi-class urban LULC for other set of simulations. All the simulations were carried out for 3 days (August 19–21, 2017) due to computational restrictions by employing all the four urban physics options. It has been found that multi-class urban LULC yielded better results than single class urban built –up simulation when validated with respect to ground observation. The RMSE values for multi-class urban LULC provided less RMSE than single class urban LULC, those are in terms of temperature at 2 m, relative humidity and wind speed are 0.91 °C, 2.63% and 1.82 m/s respectively. Similarly, BEP+BEM urban physics option provided reduced RMSE values than the SLUCM and BEP scheme. The RMSE values in terms of temperature at 2 m, relative humidity and wind speed are 1.11 °C, 4.39% and 2.62 m/s respectively.
Highlights
1.1 Back groundMore than half of the world’s population (54 percent) dwells in urban areas
Such a large scale human intervention with the natural environment has given rise to the phenomenon of Urban Heat Island (UHI) in which the temperature of the urban core is higher than the surrounding areas subject to calm weather conditions (Epa Chen & EPA, 2008)
According to the World Resources Institute (WRI), an international research organization, a major proportion of the world population will be subjected to frequent inland floods, rising sea levels, intense storms and more frequent periods of extreme hot and cold owing to climate change (“World ’ s 15 Countries with the Most People Exposed to River Floods,” 2018)
Summary
1.1 Back groundMore than half of the world’s population (54 percent) dwells in urban areas. Today there are over 400 cities in the world with populations of over 1 million (United Nations, 2007).The global urban population is estimated to grow by 2.5 billion urban inhabitants between 2014 and 2050, with nearly 90 per cent of the increase concentrated in Asia and Africa (UNDESA, 2014) alone Such a large scale human intervention with the natural environment has given rise to the phenomenon of Urban Heat Island (UHI) in which the temperature of the urban core is higher than the surrounding areas subject to calm weather conditions (Epa Chen & EPA, 2008). Mean thermal and effects of the cities on the atmosphere can be estimated using urban parameterizations incorporated in numerical weather prediction (NWP) models These models are executed with a grid spacing of 0.5-1 km for local and regional weather forecasts which provide input to air dispersion and pollution models. At such a fine horizontal resolution it becomes important to realistically represent the role of urban land use in local and regional weather
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