Characteristics of the tropical tropopause over the northeast monsoon region

Abstract

In this study, we have characterized the tropical tropopause parameters such as the cold point tropopause (CPT) height (CPT-H) and temperature (CPT-T), convective tropopause (COT) height (COT-H) and temperature (COT-T), and the tropical tropopause layer (TTL) using radiosonde observations during 2014–2019 over Chennai (13.0oN, 80.06oE) located in the northeast (NE) monsoon region. The water vapor and ozone data from the microwave limb sounder (MLS) simultaneous to the radiosonde observations are also utilized to understand their roles on the CPT variations for different convective conditions obtained from Infrared brightness temperature (IRBT) data. CPT over Chennai becomes higher (17.6 ± 0.3 km) and colder (189.7 ± 0.9 K) during the winter season and lower (16.6 ± 0.2 km) and warmer (192.1 ± 1.0 K) during the summer monsoon season, however, not in the same month. The water vapor (CPT-W) and ozone (CPT-O) mixing ratios at CPT are found to be lower (~ 70 ± 1.4 ppmv and 3.1 ± 0.4 ppmv) during the winter season and higher (153 ± 4.2 ppbv and 4.8 ± 0.6 ppmv) during summer monsoon season. COT, however, becomes lower (12.4 ± 0.3 km) and higher (13.3 ± 0.3 km) during premonsoon and summer monsoon seasons, respectively. The TTL thickness is lesser (3.5 ± 0.6 km) and greater (4.8 ± 0.8 km) during winter and summer monsoon seasons. Over Chennai, the seasonal variation of the upper troposphere and lower stratospheric temperature, water vapor, and ozone anomalies are found to be in phase. We have categorized tropical convections as non-penetrative and penetrative. It is observed that the TTL temperature warms with the increasing strength of the non-penetrative convections and cools for the penetrative convection.