Abstract: The relationship between the satellite thermal infrared brightness temperature and ground elevation is very important information that can reflect the thermal state of earth surface.It is also one of the main factors which influence the analysis of satellite thermal infrared anomalies before earthquakes.Previous study is not enough and comprehensive and it needs a deep research.In this paper,the decreasing infrared brightness temperature per 100m increase of the ground elevation is defined as brightness temperature gradient.The mainland of China is divided into 6 regions for separate research:the Northwest,the Qinghai-Tibet,the Sichuan-Yunnan,the Northeast China,the North China and the South China.This paper selects remote sensing data at midnight in order to reduce the influence of solar radiation and preprocesses thermal infrared remote sensing images systematically including cloud and noise removing and so on.On the basis of filtering and processing the satellite thermal infrared remote sensing data,this paper analyses the relationship between the satellite infrared brightness temperature and ground elevation in the 6 regions with the method of regression analysis.Studying on the 6 regions separately,some abecedarian results are developed:1)the general trends of brightness temperature gradient are similar between different areas,but there are some differences in details;2)the brightness temperature gradient of the 6 regions are all less than the air temperature lapse rate(0.64℃/(100m))calculated on the basis of air temperature data,also less than 0.4℃/(100m),from 0.15℃/(100m)to 0.35℃/(100m)in most situations;3)except the Qinghai-Tibet area,the brightness temperature gradient of the other five regions is generally greater in summer than in winter.On the whole,the brightness temperature gradient increases from January to September,reaches the maximum around September,decreases subsequently and gets to the minimum around January.It is considered as the result of the effect of the cold air in winter,the absorption of the atmosphere to ground radiation and the diversity of different geographical environments are the key factors that influence the temporal and spatial variation of brightness temperature gradient.

Key words: brightness temperature gradient, satellite remote sensing, infrared brightness temperature

摘要： 海拔高度与卫星热红外亮温的关系是尚待深入研究的能反映地球表面热状态的重要信息,也是影响地震热红外异常分析的主要因素之一,文中把海拔高度每增加100m亮温降低的幅度称为亮温梯度,在系统筛选处理卫星热红外遥感数据的基础上,把中国大陆划分为西北、青藏、川滇、东北、华北和华南6个地区分别进行研究,取得了一些初步的结果:1)不同地区、不同月份亮温梯度的总体趋势相似,但又存在细节上的差异;2)各个地区的亮温梯度都小于前人根据气温资料计算得到的气温直减率(0.64℃/(100m)),而且在绝大多数情况下都<0.4℃/(100m),变化范围主要集中在0.15～0.35℃/(100m)之间;3)除青藏地区以外,其它5个地区的亮温梯度总体上表现为夏大冬小的特点。分析认为冬季冷空气的作用、大气对地面辐射的吸收衰减以及地理环境的差异等是影响亮温梯度时空动态的主要因素。

关键词: 亮温梯度, 卫星遥感, 红外亮温