Analysing Seasonal Variations in the Tropical Tropopause and the Impact of Deep Convection on the Tropopause Structure Over a High-Altitude Station in the Western Ghats

Jha, AK (2022) Analysing Seasonal Variations in the Tropical Tropopause and the Impact of Deep Convection on the Tropopause Structure Over a High-Altitude Station in the Western Ghats. In: Pure and Applied Geophysics .

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Abstract

The present work examines the structure and variability of the tropopause over a high-altitude site in the Western Ghats (WG) and attempts to understand the impact of deep convection on the thermal structure of the tropopause. The characteristics of the seasonal variations in the cold-point tropopause (CPT), lapse rate tropopause (LRT), convective tropopause (COT) and tropical tropopause layer (TTL) are studied using high-resolution radiosonde observations from 2012 to 2019 over Mahabaleshwar (17.92° N, 73.66° E; 1.38 km amsl) in the WG. On seasonal time scales, the altitude (temperature) of CPT, LRT and COT vary by ~ 1 km (~ 2 K), 0.5 km (~ 1.8 K) and 1.3 km (~ 6 K), respectively. CPT and LRT show highly similar seasonal behaviour, with higher and colder values during winter and lower and warmer values during monsoon months, whereas COT exhibits a different pattern of seasonal behaviour with higher variability. The thickness of the TTL varies from a minimum of 4.2 km in July to a maximum of 6 km in March. Further, the impact of deep convection on the tropopause was analysed by collocating the radiosonde observations with the deep convection based on infrared brightness temperature (IRBT) data of Indian geostationary satellites, INSAT-3D and Kalpana-1. The anomalies of temperature profiles and tropopause parameters (altitude and temperature) are estimated during deep convection categorized by IRBT values into three groups designated as DC1 (< 220 K), DC2 (220�235 K) and DC3 (235�245 K). The analysis reveals cooling within the TTL and warming in the middle troposphere which are enhanced with the deepening of convection. The TTL cooling (mid-tropospheric warming) peaks near 16 km (10 km) altitude and varies as �1.1 K (1.2 K), �0.8 K (0.9 K) and �0.6 K (0.4 K) for DC1, DC2 and DC3, respectively. The tropopause anomalies show that the CPT and LRT descend while the COT ascends during deep convection. The thickness of the TTL decreases due to the combined effect of the descent of the CPT and ascent of the COT, but the main contribution is the elevation of the COT. The TTL narrows as the convection deepens, and shrinks most (~ 1 km) during deepest convection (DC1). © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Item Type:	Journal Article
Publication:	Pure and Applied Geophysics
Publisher:	Birkhauser
Additional Information:	The copyright for this article belongs to Birkhauser
Keywords:	Clouds; Geostationary satellites; Radiosondes; Tropics; Troposphere, Cold point; Deep convection; High altitude sites; Infrared brightness temperature; Lapse rate; Radiosonde observations; Seasonal variation; Tropical tropopause; Tropical tropopause layers; Western ghats, Natural convection
Department/Centre:	Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited:	07 Feb 2022 12:14
Last Modified:	07 Feb 2022 12:14
URI:	http://eprints.iisc.ac.in/id/eprint/71257

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