Global distribution of deep convection reaching tropopause

Correct description of stratosphere-troposphere exchange process is important in prediction of global climate change. In the process, convection may vertically transport tropospheric air and chemical species into the stratosphere through rapid injection of air. Therefore, it is critical to understand the geo-graphical distribution and characteristic of deep convection reaching tropopause globally.

To characterize and quantify tropopause-reaching deep convection, one-year Global Precipitation Mission (GPM) Ku-band radar echoes are surveyed in relation to several reference levels that are determined by the near-coincident ERA-Interim reanalysis dataset. Consistent with the observations of the Tropical Rainfall Measuring Mission (TRMM) over the tropics, the GPM has detected tropopause-reaching deep convection dominantly over tropical land, especially over Panama and Central Africa. At mid and high latitudes, tropopause-reaching convective storms are mainly found over land in the Northern Hemisphere during the summer. Compared to those in the tropics, convective cores at mid and high latitudes have relatively larger sizes at the tropopause, especially those over central North America. The meridional distributions of the occurrences of 15 dBZ and 20 dBZ radar echoes at the tropopause show two comparable maxima, one in the tropics and the other in northern mid-high latitudes. This implies that the convection penetrating the tropopause at northern mid-high latitudes is as frequent as those over the tropics. During boreal summer, such mid-high latitude storm occurrence is even greater than that in the tropics.

The properties of Overshooting Precipitation Features (OPFs) in different region are investigated. The OPFs above the cold point tropopause height (ZCP) and Z380K over land in the subtropics are even stronger than those in the tropics. It is important to understand the contributions of tropopause-reaching deep convection in the vertical transport of trace gases between the troposphere and the stratosphere.