DETECTION AND ANALYSIS OF SURFACE URBAN COOL ISLAND USING THERMAL INFRARED IMAGERY OF SALATIGA CITY, INDONESIA

The detection and monitoring of the dynamics of urban micro-climatesneeds to be performedeffectively, efficiently, consistently and sustainably inan effort to improve urban resilience to suchphenomena. Thermal remote sensing posesses surface thermal energy detection capabilities which can be converted into surface temperatures and utilised to analyse the urban micro-climate phenomenon overlarge areas, short periods of time, and at low cost. This paper studies the surface urban cool island (SUCI) effect, the reverse phenomenon of the surface urban heat island (SUHI) effect, in an effort to provide cities with resistance to the urban microclimate phenomenon.The study also aims to detect urban micro-climate phenomena, and to calculate the intensity and spatial distribution of SUCI. The methods used include quantitative-descriptive analysis of remote sensing data, including LST extraction, spectral transformation, multispectral classification for land cover mapping, and statistical analysis. The results show that the urban micro-climate phenomenon in the form of SUHI in the middle of the city of Salatiga is due to the high level of building density in the area experiencing the effect, which mostly has a normal surface temperature based on the calculation of the threshold, while the relative SUCI occurs at the edge of the city. SUCI intensity in Salatiga ranges between -6.71°C and0°C and is associated with vegetation.

Evaluating the performance of WRF urban schemes and PBL schemes over Dallas Fort Worth during a dry summer and a wet summer

This study evaluated the Weather Research and Forecasting (WRF) model sensitivity to different planetary boundary layer (PBL) schemes (the YSU and MYJ schemes) and urban schemes including the bulk scheme (BULK), single-layer urban canopy model (UCM), multi-layer building environment parameterization (BEP) model, and multi-layer building energy model (BEM). Daily reinitialization simulations were conducted over Dallas-Fort Worth during a dry summer month (July 2011) and a wet summer month (July 2015) with weaker (stronger) daytime (nocturnal) UHI in 2011 than 2015. All urban schemes overestimated the urban daytime 2m temperature in both summers, but BEP and BEM still reproduced the daytime urban cool island in dry summer. All urban schemes reproduced the nocturnal urban heat island, with BEP producing the weakest one due to its unrealistic urban cooling. BULK and UCM overestimated the urban canopy wind speed, while BEP and BEM underestimated it. The urban schemes showed prominent impact on daytime PBL profiles. UCM+MYJ showed a superior performance than other configurations. The relatively large (small) aspect ratio between building height and road width in UCM (BEM) was responsible for the overprediction (underprediction) of urban canopy temperature. The relatively low (high) building height in UCM (BEM) was responsible for the overprediction (underprediction) of urban canopy wind speed. Improving urban schemes and providing realistic urban parameters were critical for improving urban canopy simulation.

Summer- and Wintertime Variations of the Surface and Near-Surface Urban Heat Island in a Semiarid Environment

This paper examines summer- and wintertime variations of the surface and near-surface urban heat island (UHI) for the Phoenix metropolitan area using the Moderate Resolution Imaging Spectroradiometer (MODIS), near-surface meteorological observations, and the Weather Research and Forecasting (WRF) Model during a 31-day summer- and a 31-day wintertime period. The surface UHI (defined based on the urban–rural land surface temperature difference) is found to be higher at night and during the warm season. On the other hand, the morning surface UHI is low and frequently exhibits an urban cool island that increases during the summertime period. Similarly, the near-surface UHI (defined based on the urban–rural 2-m air temperature difference) is higher at night and during summertime. On the other hand, the daytime near-surface UHI is low but rarely exhibits an urban cool island. To evaluate the WRF Model’s ability to reproduce the diurnal cycle of near-surface meteorology and surface skin temperature, two WRF Model experiments (one using the Bougeault and Lacarrere turbulent scheme and one with the Mellor–Yamada–Janjić turbulent parameterization) at high spatial resolution (1-km horizontal grid spacing) are conducted for each 31-day period. Modeled results show that the WRF Model (coupled to the Noah-MP land surface model) tends to underestimate to some extent surface skin temperature during daytime and overestimate nighttime values during the wintertime period. In the same way, the WRF Model tends to accurately reproduce the diurnal cycle of near-surface air temperature, including maximum and minimum temperatures, and wind speed during summertime, but notably overestimates nighttime near-surface air temperature during wintertime. This nighttime overestimation is especially remarkable with the Bougeault and Lacarrere turbulent scheme for both urban and rural areas.

SPATIAL VARIATION OF URBAN HEAT ISLAND INTENSITY IN URBAN CITIES USING MODIS SATELLITE DATA

Urban Heat Island (UHI) refers to the occurrence of higher temperatures in urban areas than the neighbouring rural areas. The neighbouring land cover also has some influence on the urban temperatures. The present study focuses on the UHI effect observed in four different cities i.e. Bikaner, Hyderabad, Vadodara and Varanasi which were surrounded by different natural land covers using MODIS satellite images. Bikaner shows Urban Cool Island (UCI) and Varanasi show UHI during day time. Vadodara and Hyderabad do not show much variation in urban and rural LST during day time. However, UHI effect was found clearly significant during night time in the four cities. UHI intensity was calculated using night LST and found highest in Hyderabad and lowest in Bikaner. The relation of LST with % Impervious was studied which shows good positive linear relation when significant UHI effect was observed and negative linear relation when UCI effect was observed. The slope obtained from linear regression of night LST with % Impervious was compared with the UHI intensity in the four cities and found to show good positive linear relation. Therefore, % Impervious can be used to quantify UHI intensity in urban areas.

The Microclimatic Effect of Green Infrastructure (GI) in a Mediterranean City: the Case of the Urban Park of Ciutadella (Barcelona, Spain)

The use and promotion of green infrastructure (GI) is of great importance for improving urban climates and for helping cities to be more resilient and sustainable in the context of climate change. For this reason, the effect of urban parks on city climates is of great interest for research. In this study, temperature measurements were made during 14 nights in the winter and spring of 2015 in the largest park of the Mediterranean city of Barcelona, Spain: the Ciutadella Park. The analysis of the measurements made inside the park and in its adjacent urban environment has confirmed the existence of an urban cool island (UCI) with a maximum cooling intensity of 5.2°C (9.4°F) in winter, under anticyclonic situations preferably, and an average cooling intensity of 2.7°C (4.9°F). In the spring months, the urban cool island has an intensity under the average, with a maximum of 2.1°C (3.8°F).