%0 Journal Article
%T A Physically Based Spatial Expansion Algorithm for Surface Air Temperature and Humidity
%A Hongbo Su
%A Jing Tian
%A Renhua Zhang
%A Shaohui Chen
%A Yongmin Yang
%A Yuan Rong
%A Sujuan Mi
%A Jianwei Qi
%J Advances in Meteorology
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/727546
%X An algorithm was developed to expand the surface air temperature and air humidity to a larger spatial domain, based on the fact that the variation of surface air temperature and air humidity is controlled jointly by the local turbulence and the horizontal advection. This study proposed an algorithm which considers the advective driving force outside the thermal balance system and the turbulent driving force and radiant driving force inside the thermal balance system. The surface air temperature is determined by a combination of the surface observations and the regional land surface temperature observed from a satellite. The average absolute difference of the algorithm is 0.65 degree and 0.31£¿mb, respectively, for surface air temperature and humidity expansion, which provides a promising approach to downscale the two surface meteorological variables. 1. Introduction Air temperature and humidity are the most fundamental elements that human beings interact with in the environment. The heat and steam (moisture) that reach the surface (the surface or active surface of soil, vegetation, rocks, and water, generally called the earth¡¯s surface) have complex interaction with the air in the boundary layer, causing new balance and redistribution of heat and steam. The most important and frontier indicator for this new temporal and spatial distribution is the air temperature and humidity at the height of thermometer shelter in weather stations. For a long time, air temperature and humidity are not only the primary items of weather forecast, but also the core input to model the surface sensible heat flux and latent heat flux. The Penman-Monteith equation [1] requires the air temperature and humidity and some other inputs to calculate the evapotranspiration on the basis of energy balance. The spatial distribution of air temperature and humidity depends on the uniformity of the surface energy balance and the intensity of the horizontal advection [2]. So far, the observation means for such important parameters is still limited in very small ¡°point¡± scale [3]. The spatial representativeness of the air temperature and humidity at the height of thermometer shelter in weather stations is about a few hundred square meters [4, 5]. The density of weather stations varies with each country¡¯s capacity on meteorological observations and the corresponding financial budget. Currently in China, there is approximately one weather station for each administrative county, which means one weather station for average area of 5846 square kilometers (close to 6000 MODIS pixel; counties in
%U http://www.hindawi.com/journals/amete/2013/727546/