Distribution and trends of the cold-point tropopause over China from 1979 to 2014 based on radiosonde dataset

Abstract

The variation trends of the cold-point tropopause (CPT) are presented using radiosonde observations from 77 stations over China during 1979–2014. The latitude regions over China from 18°N to 53°N are divided into 7 latitude zones with every 5° intervals, and the spatial areas of 18°N–53°N, 75°E–135°E are divided into 27 lattices with 5°×10° grids. The annual-mean values of height-of-CPT (H-CPT) and temperature-of-CPT (T-CPT) are then calculated by all the available samples within each latitude and longitude bin. By using the least squares regression method, it is found that the H-CPT increases with the rate of 273m/decade, and overall the significant cooling rate of −0.70K/decade for the T-CPT over the whole of China. Then, the trends and latitude distribution of H-CPT and T-CPT for each latitude zone are analyzed. The difference of H-CPT among latitude distribution characteristic is reducing year by year, and the difference of T-CPT is enlarging. The H-CPT displays a rising trend between 28°N–53°N latitude region with the positive change rates, and it has decline trend between 18°N–28°N latitude region with the negative change rates. The change rates of T-CPT are negative values for all latitude zones. At last, the nonuniform latitudinal and longitudinal distribution of long-term trends of H-CPT and T-CPT are first presented for each spatial cell.