Chinese scientists reconfirmed that the earth's tropics are becoming bigger and bigger, which is called tropical expansion.
It is the first time to find that the difference of tropopause height among latitude distribution characteristic is reducing year by year, and the difference of tropopause temperature is enlarging. It is further confirmed the expansion of the tropics.
WEI Heli and TANG Chaoli’s team at Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science(AIOFM) conducted a study on the distribution and trends of the cold-point tropopause (CPT) over China and they reported that with the temperature of CPT (T-CPT) decreased year by year, the height of CPT (H-CPT) in China was gradually increased in the past 40 years.
Research on the long-term trend of tropopause is of great importance as the tropopause structure is a potentially important indicator of the global climate change, and the variation of it closely linked to climate change. And in China, for such a large country, the climate varies from subarctic to subtropical, so the analysis of the temporal and spatial variations of the regional climate in China is of great importance in research of global climate change.
Dr. TANG Chaoli and his coworkers processed and analyzed a large volume of radiosonde data collected by the Integrated Global Radiosonde Archive (IGRA). In the study, they presented long-term trends of H-CPT and T-CPT over each latitude and longitude grids within China territory through analyzing the sounding dataset of 77 stations over China from 1979 to 2014.
The distribution of the variations and trends of H-CPT (T-CPT) are first presented over China region during 1979-2014. They statistically found that the H-CPT increases at the rate of 273 m/decade (Fig.1a), and overall the significant cooling rate of -0.70 K/decade for the T-CPT (Fig.1b) over the whole of China.
Through the study they reconfirmed the expansion of the tropics. At the same time they reported the difference of H-CPT among latitude distribution characteristic is reducing year by year (Fig.1c), and the difference of T-CPT is enlarging (Fig.1d).
This research entitled Distribution and trends of the cold-point tropopause over China from 1979 to 2014 based on radiosonde dataset has been published in Atmospheric Research. This work was partly supported by the National Natural Science Foundation of China.
Fig.1. The spatial variations and trends of H-CPT (T-CPT) over China. (a) The annual-mean trends of H-CPT over China during 1979—2014, the solid lines are the corresponding linear trends with a least square procedure, the change rates are shown at the right-top of each diagram; (b) Same as (a) but for T-CPT; (c) The annual-mean trends of H-CPT for each latitude zone; (d) Same as (c) but for T-CPT (Image by TANG Chaoli)