Variability of the tropical tropopause over Indian monsoon region

Abstract

The variations of the cold point tropopause (CPT), convective tropopause (COT), lapse rate tropopause (LRT), and tropical tropopause layer (TTL) from subdaily to seasonal timescales are studied using high‐resolution radiosonde observations from April 2006 to December 2008 over a tropical station Gadanki (13.5°N, 79.2°E), in the Indian monsoon region. The correlations between temperatures and altitudes of the different tropopauses and between TTL thickness and satellite brightness temperature (TBB) are estimated. Diurnal behavior of CPT, LRT, and COT is also investigated. The seasonal variation of the CPT at Gadanki shows notable differences when compared to Western Pacific region, though major features remain similar. CPT temperature at Gadanki goes below 191 K more frequently during December to May than during June to November. The TTL thickness, which is the difference between CPT altitude and COT altitude, is small during summer monsoon and is strongly correlated with TBB on seasonal scale. The CPT altitude and temperature show large variation by as much as ∼1 km and ∼3 K, respectively, even on subdaily scale. During deep convection (TBB < 240) the CPT is found to ascend (∼0.6–0.8 km) in some events and descend (∼1 km) in some other events. Interestingly, during clear sky conditions (TBB > 240), increase in the CPT altitude with increase in CPT temperature is noticed on some occasions. Strong correlation between LRT (and COT) altitude and temperature from subdaily to seasonal timescale is noticed in contrast to CPT altitude and temperature. However, the correlation between TBB and CPT, LRT, and COT degrades from seasonal to subdaily timescale.