Global Mean Tropospheric Temperature Trends Test During The Last 50 Years

Based on datasets obtained from radiosonde, Satellite-borne Microwave Sounding Unit (MSU), and reanalysis et al, the analysis of upper air temperature trends have been well documented over the past decades. The reanalysis datasets are the main choice for the research of upper climate change, but due to complicated sources and different assimilation system for reanalysis datasets, inhomogeneity exists in the long time series. So far, there is no consistent result for the global upper climate change, especially, conclusions based on reanalysis and satellite data are less convinced. Therefore, it is always an important direction to research and develop a new upper radiosonde archives to analyze upper climate change. In this paper, for the analysis of the global troposphere temperature trends of each level, a new radiosonde dataset IGRA for monthly mean temperature covering 1963 to 2006 from US National Climatic Data Center (NCDC) was adopted, and in order to lower scientific uncertainty of the analysis results as much as possible, we combined the statistic results from NCEP/DOE AMIP-II reanalysis(R-2), ERA-40 and HadAT2 to do a comparative analysis. The following are the main studies and conclusions.1) Based on IGRA monthly mean temperature, a higher quality integrated global radiosonde gridded temperature dataset IGRA Grid is developed by thin plate smoothing splines.2) IGRA Grid dataset may really and scientifically reflect global troposphere temperature change. The 5*5 resolution gridded dataset have an advantage over HadAT2 because of its no missing values. In the middle and lower level of troposphere, the global annual mean temperature change trends of IGRA Grid are similar to those of HadAT2 and ERA-40, and also with the similar change rates. And in the middle and upper level of troposphere , the temperature change trends of IGRA Grid (1979～2006) and NCEP/DOE (R-2) are similar. And on the level of 100hPa (lower stratosphere), the temperature change rates of IGRA Grid are some larger than those of HadAT2, larger than those of ERA-40 significantly, the three former ones are much smaller than those of NCEP/DOE (R-2).3) The global upper temperature change trends identified by IGRA Grid show that,①The global annual mean temperature has increased by about 0.6℃from 1963 to 2006 covering the level 1000hPa (near surface) up to 400hPa (middle of troposphere), and the warming rate is 0.18±0.02℃/10yrs, among which it is a little larger on the level of 850hPa. But at the bottom of stratosphere (100hPa) it shows obviously decreasing trend (-0.3～-0.5℃/10yrs).②For the high latitude regions of northern hemisphere, warming trends on the level of 1000 and 850hPa in winter are clearly faster than that of in summer, and by contrary, up to 500hPa warming trends in summer are faster than those of in winter.