北京地区不同城市热岛指标和城市效应研究方法的对比分析

Comparative analysis of different urban heat island indicators and urban effects research methods in Beijing

城市热岛效应是城市气候的突出现象之一,由于观测手段差异和数据代表性的不同,对城市热岛存在多种定义,其中冠层城市热岛和地表城市热岛的应用最广泛,但是目前两者之间的比较工作开展相对较少.“城市效应”是指由于城市的出现对一个地区气候的影响,城市热岛本质上属于城市效应的表征之一.分离“城市效应”常用的方法有“城乡差异”和“城市化前后对比”两种,二者分别从观测资料的空间和时间差异着手计算,目前对两种方法结论的一致性分析尤为欠缺.以北京地区为研究对象,利用地面气象站和卫星遥感观测数据,对比分析了该地区气温和地表温度、冠层热岛和地表热岛的数值与变化情况,并进一步分析了分离“城市增温效应”两种方法的可比性,结果表明:(1)2009-2017年北京地区五种热岛指标均值比较为:由卫星遥感反演得到的日间地表热岛最大,其次为地面观测得到的最低气温冠层热岛和卫星遥感反演得到的夜间地表热岛,二者数值相近,地面观测得到的平均气温冠层热岛再次,而地面观测得到的最高气温冠层热岛远小于其他四类;(2)以通州站为例,1980-2017年用以分离“城市增温效应”的城市化前后差异和城乡对比两种方法的结果分别为0.65℃/(10a)和0.61℃/(10a),结论基本一致,虽然由于乡村站平均气温受到城市化影响,城乡对比法存在低估现象,但误差在可接受范围内,两种方法仍具有相互替代性.

Urban heat island effect is one of the prominent phenomena of urban climate.Due to the difference in observation methods and data representativeness,there are many definitions of urban heat island,among them,the canopy layer urban heat island and the surface urban heat island are the most widely used.However,the comparison between the two is relatively rare at present.The"urban effects"refer to the impact of the emergence of cities on the climate of a region.Urban heat island is essentially one of the characteristics of urban effects.There are two commonly used research methods for separating the"urban effects":"urban-rural difference"and"comparison before and after urbanization",which are calculated from the spatial and temporal differences of observed data respectively.At present,the consistency analysis of the two methods'conclusions is particularly lacking.Taking Beijing area as the research object,this paper compares and analyzes the values and changes of air temperature and surface temperature,canopy layer heat island and surface heat island in this area by using the ground meteorological station and satellite remote sensing observation data,and further analyzes the comparability of the two methods to separate"urban warming effect".The results show that:(1)The mean values of the five UHI(Urban Heat Island)indicators in Beijing from 2009 to 2017 were as follows:the daytime surface heat island obtained by satellite remote sensing inversion was the largest,followed by the minimum air temperature canopy layer heat island obtained from ground observation and the nighttime surface heat island obtained by satellite remote sensing inversion.The two values were similar.The average temperature canopy layer heat island obtained from ground observation was lower than the former,and the maximum temperature canopy layer heat island obtained from ground observation was much smaller than the other four types.(2)Taking TongZhou station as an example,the results of the two methods of separating"urban warming effect"from 1980 to 2017 were 0.65℃/(10a)and 0.61℃/(10a),which were basically consistent.Although there was an underestimation phenomenon in the urban-rural comparison method due to the impact of urbanization on the average temperature of rural stations,the error was within an acceptable range,and the two methods were still mutually substitutable.