归一化水汽指数与地表温度的关系

Relationship between normalized difference moisture index and land surface temperature

城市热岛的遥感研究,传统上主要利用归一化植被指数作为指标来评估地表温度-植被之间的关系。本研究探讨了以归一化水汽指数作为评估其与地表温度关系的适应性,比较了归一化水汽指数和归一化植被指数在表达城市热岛效应方面的效力。利用"单窗算法"和3个不同时段的TM/ETM+数据获取了珠江三角洲核心区域的地表温度分布图,分析了两种指数与地表温度之间的关系。对局部区域逐像元和对区域总体分析的结果表明:不同时段的地表温度与归一化水汽指数之间均存在较强的线性关系,而地表温度与归一化植被指数之间的线性关系相对较弱。说明在城市化的环境下,与传统上常用归一化植被指数作为指标来定量分析地表温度相比,归一化水汽指数提供了一种互补的、甚至更加有效的衡量指标。

Remote sensing of urban heat islands（UHIs） has traditionally used the Normalized Difference Vegetation Index（NDVI） as the indicator of vegetation abundance to estimate the relationship land surface temperature（LST） and vegetation.This study investigates the applicability of Normalized Difference Moisture Index（NDMI） as an alternative indicator.This paper compares the Normalized Difference Vegetation Index（NDVI） and Normalized Difference Moisture Index（NDMI） as indicators of surface urban heat island effects in Landsat imagery by investigating the relationships between the Land Surface Temperature（LST）,NDMI,and the NDVI.Landsat Thematic Mapper（TM） and Enhanced Thematic Mapper Plus（ETM＋） data were used to estimate the LST through the single window algorithm from three different months for the Zhujiang Delta area.Maps of NDVI and NDMI for three different data were generated from band 3,band 4 and band 5 of TM/ETM＋ imageries,respectively.The relationships between the LST,NDMI,and the NDVI were analyzed supported by Geographic Information System（GIS）.Our analysis indicates that there is stronger linear relationship between LST and NDMI for all three months,whereas the relationship between LST and NDVI is much weaker and varies by different months.With the change of seasons from summer to autumn,the linear correlation relationship between LST and NDMI was gradually lowered.This result suggests that NDMI provides a complementary metric to the traditionally applied NDVI for analyzing LST quantitatively over the three months for surface urban heat island studies using thermal infrared remote sensing in an urbanized environment.