Detection Of Urban Thermal Environment And Its Storage Heat Flux By Remote Sensing

As one of the main factors of global change,human activities have altered environment and climate change by converting the natural surface to artificial impervious surface during urbanization.During these processes,the land surface properties was modified with more impervious surfaces in higher conductivity and heat storage.Therefore,the difference of urban and rural surface properties caused urban heat island effect due to their temperature difference,and further lead to the increase of extreme weather events and poor air qualities that influence people's lives.This research mainly includes:(1)An improved urban index(VANUI)was used here to detect urbanization process in JING-JIN-JI area from 2001-2012.Compared with the traditional method for urban detection using DMSP night light images,VANUI has improved the urban process monitoring by reducing signal saturation in urban center.The results showed that VANUI could catch the urbanization process happened in JING-JIN-JI area during last decades.Spatial pattern of urban expansion from 2001-2012 indicated that the urban area of JING-JIN-JI was doubled from 2001-2012,and the fasted urbanization region happened in Tangshan,Hebei Province.Linear trend was also detected in urban development by VANUI index from 2001-2012,and the most important increasing period happed in 2004-2007 and 2009-2012.(2)Land surface temperature product of MODIS was used to examine the spatial characteristics of thermal environment in Jing-Jin-Ji area from 2003-2012 and analyzed the different of LST in different land cover types.The results indicated that the LST in southern JJJ was higher than that of northern.Our results also indicated land surface temperature in urban area was higher than other land use types.The differences between natural and unnatural underlying not only showed on LST,but also reflected on the scale of temperature changes.Thermal environment in JJJ area was highly altered by human activities,especially the urbanization happened in last decades.(3)We tried to estimate the storage heat flux using satellite images and meteorological observation from Tianjin and Xiqing station in study area to analyze the variation of surface energy components in urban and rural regions.Our results indicated that impervious surface in urban area could capture more solar radiation than rural areas.The maximum value of heat storage flux appeared in industrial area,while the heat storage flux in low-rise building and road was lower than industrial area.Rural surface with large natural surface(woodland and grassland)has lowest heat storage flux.Urban heat island is related to or further driven by the distribution patterns of urban heat storage,and it is helpful to urban planning by detailed examine its variation in different urban land formation.