Effect of gravity waves on the tropopause temperature, height and water vapor in Tibet from COSMIC GPS Radio Occultation observations

• The tropopause temperature and height in Tibet are investigated from GPS RO.
• CPT temperature increases in winter correlating with GW potential energy.
• GW is main source of the water vapor transportation above the CPT in Tibet.

The tropopause plays an important role in climate change, particularly in Tibet with complex topography and climate change system. In this paper, the temperature and height of the Cold Point Tropopause (CPT) in Tibet are obtained and investigated from COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) GPS Radio Occultation (RO) during June 2006–Feb 2014, which are compared with Lapse Rate Tropopause (LRT) from Atmospheric Infrared Sounder (AIRS/NASA). Furthermore, the impact of Gravity waves (GW) potential energy (Ep) on the CPT-Temperature, CPT-Height, and the variation of stratospheric water vapor with GW Ep variations are presented. Generally the coldest CPT temperature is in June–July–August (JJA) with −76.5 °C, resulting less water vapor into the stratosphere above the cold points. The temperature of the cold point increases up to −69 °C during the winter over the Tibetan Plateau (25–40°N, 70–100°E) that leads to increase in water vapor above the cold points (10 hPa). Mean vertical fluctuations of temperature are calculated as well as the mean gravity wave potential energy Ep for each month from June 2006 to Feb 2014. Monthly Ep is calculated at 5°×5° grids between 17 km and 24 km in altitude for the Tibetan Plateau. The Ep raises from 1.83 J/Kg to 3.4 J/Kg from summer to winter with mean Ep of 2.5 J/Kg for the year. The results show that the gravity waves affect the CPT temperature and water vapor concentration in the stratosphere. Water vapor, CPT temperature and gravity wave (Ep) have good correlation with each other above the cold points, and water vapor increases with increasing Ep.