Assessing the local- impacts of heat advection on urban heat islands in Kolkata Metropolitan Area
Assessing the local- impacts of heat advection on urban heat islands in Kolkata Metropolitan Area
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DOI：
10.1016/j.uclim.2022.101139
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发表时间：
2022-02-24
期刊：
影响因子：
6.4
通讯作者：
Chatterjee, Soumendu
中科院分区：
文献类型：
--
作者：
Dinda, Apurba;Chatterjee, Soumendu
城市热平流（UHA）是一种重要的气象过程，它通过在城市边界层（UBL）（屋顶以上）形成热羽流来调节城市周围顺风农村地区的气温（TA）。本研究认为，UHA 的影响也存在于城市冠层 (UCL)（从地面到屋顶层），从而影响局部城市热岛 (UHI)。此外，UHA的性质和强度取决于大气的动态特性，包括风速（WS）和风向（WD），以及城市环境中陆地大气相互作用的性质。调查伦敦大学学院的 UHA 现象及其对当地 UHI 影响的研究尚不充分，但此类研究有可能提供对当地热异常的深入了解，这些异常不能仅归因于现场城市表面特性（几何形状和材料）。本研究利用加尔各答都市区（KMA）9个固定天气监测站获得的每小时天气数据（2019年6月至2020年12月），实证认识WS和WD作为UHA的代理对UCL-UHI时空变化的影响。该研究还采用 ENVI-met 对微气候进行数值模拟，以明确探索局部尺度的 UHA 现象。结果表明，某个地点的逆风地表特征对于城市微气候环境中 UHA 引起的 UHI 变化具有相当大的影响。不透水和透水表面的顺风区域分别受到较暖和较冷空气平流的影响，在白天和夜间分别产生约 0.95 摄氏度和 1.62 摄氏度的 TA 对比度。在平静晴朗的天气下，不同UHA情况下WS对TA的影响是不对称的。对于较暖的空气平流，TA 随 WS 增加，直至达到类似于 2.5 m/s 的极限值；而对于较冷的空气平流，TA 持续显着降低，直至 WS 设置为类似于 5 m/s，超过该临界值，TA 对 WS 的响应对于冷空气平流和暖空气平流来说都是微不足道的。
The urban heat advection (UHA) is an important meteorological process that modulates the air temperature (TA) in downwind rural areas around cities by forming heat plume in the urban boundary layer (UBL) (above roof level). This study argues that the effects of UHA also exists in the urban canopy layer (UCL) (from the ground to roof level) to impact the urban heat island (UHI) locally. Moreover, the nature and intensity of UHA depend on dynamic properties of the atmosphere including wind speed (WS) and wind direction (WD), and the nature of land atmosphere interactions in the urban environment. Studies investigating UHA phenomena in the UCL and its impacts on the local UHIs are inadequate, but such studies are potential for providing insight into those local thermal anomalies which cannot be attributed only to onsite urban surface properties (geometry and materials). The present study uses hourly weather data (June 2019-December 2020) obtained from 9 fixed weather monitoring stations in the Kolkata Metropolitan Area (KMA) to empirically recognise the influences of WS and WD, as the proxy of UHA, on the spatio-temporal variability of UCL-UHI. The study also adopts numerical simulations of microclimate with ENVI-met for exploration of local scale UHA phenomena explicitly. Results highlight that the upwind land surface characteristics of a location have considerable influences in modifying UHI due to UHA in urban microclimatic environment. The downwind areas of impervious and pervious surfaces are influenced by the warmer and cooler air advection, respectively, and create TA contrasts by about 0.95 degrees C and 1.62 degrees C during the day and night-time, respectively. In calm and clear weather, WS imposes asymmetrical impacts on TA under different UHA situations. For warmer air advection, the TA increased with WS till a limiting value of similar to 2.5 m/s, while for the cooler air advection, significant lowering of TA continued till WS was set to similar to 5 m/s and beyond this critical value the response of TA to the WS was insignificant for both the cool and warm air advections.