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Balloon-borne cryogenic frost-point hygrometer (CFH) observations conducted over three stations Trivandrum, Hyderabad and Kolkata in the Indian region during the period 2014–2017 are used to study the influence of deep convection and monsoon dynamics on the distribution of water vapour in the upper troposphere and lower stratosphere (UTLS) and to quantify the amount of water vapour transported to the lower stratosphere (LS) during summer-monsoon (June to September). In summer monsoon season, CFH observations show a water vapour enhancement of ~40–250% in the upper troposphere (UT) and 0.5–1 ppmv (10–40%) in the LS compared to pre-monsoon. In this season, the spatial pattern of Microwave Limb Sounder (MLS) derived water vapour mixing ratio (WVMR) at 100 hPa peaks north of the deep convection core over the head Bay of Bengal (BoB). In the LS, the water vapour maximum shows a south westward shift with altitude in accordance with the anticyclonic circulation flow. The maximum altitude of deep convective cloud top increases north eastward in accordance with the peak in tropical easterly jet (TEJ) causing the altitudinal shift in water vapour enhancement in the UT. The probability of dehydration (WVMR<3 ppmv) maximizes west of the deep convective core over Head BoB. During summer-monsoon, the day-to-day variability of water vapour in the tropical tropopause layer (TTL) is mainly controlled by the dehydration of air due to freeze drying (temperature dependent) and rehydration due to recurrent overshooting deep convections. Direct injection of water vapour into the LS region is probable when the tropopause is relatively warm (>192 K). • Insitu observations of effect of monsoon dynamics and deep convection on water vapour in the UTLS during summer monsoon • Water vapour enhancement of ~40–250% in the UT and 10–40% in the LS in summer monsoon compared to pre-monsoon • The water vapour maximum shows a south westward shift with altitude in the LS region • The maximum altitude of deep convective cloud top increases north eastward over Indian region similar to the peak in TEJ [ABSTRACT FROM AUTHOR]

This paper deals with the temporal changes in the altitude distribution of tropospheric ozone (O 3) based on the measurements by balloon-borne O 3 -sondes during 2011–2014, conducted at the tropical, coastal site Thiruvananthapuram on the south west coast of India. This is the first study from this region addressing the highly dynamic nature of tropospheric O 3 profiles (in terms of their vertical structure and short-term changes) and attempting to categorise them based on 121 in-situ measured O 3 profiles. The tropospheric O 3 profiles could be categorised into four major groups namely (i) those with steady O 3 mixing ratio (ii) with increasing mixing ratio, (iii) with mid-tropospheric enhancement and (iv) with multiple layers/laminar nature. The causative mechanisms of these different categories were examined. The observed differences in the tropospheric O 3 distribution are attributed to meteorological conditions in particular the synoptic scale systems, long range transport, intrusion from stratosphere and photochemistry, most importantly, the effect of water vapour content. Water vapour and O 3 showed complex dependence with positive and negative association depending on the precursor levels and availability of water vapour. The altitudinal changes in O 3 also exhibited close association with those of potential temperature and equivalent potential temperature. An analysis of the seasonal characteristics of vertical distribution of tropospheric O 3 also carried out along with the altitude-dependent seasonal behaviour. In general, the total column O 3 estimated by the integration of O 3 -sonde retrieved profiles differed by about ±10% with those retrieved by satellite-based measurements. The TCO contributes to about 16% (34 DU) of the total column O 3 , with minimum of 9% in October and maximum of 27% on March. In general, the OMI retrievals under-estimates the O 3 -sonde derived TCO by 5–10 DU in all the seasons. • Dynamic nature of tropospheric O 3 profiles observations based on O 3 -sonde. • Dependence of O 3 on water vapour shows positive and negative correlation. • Amount of water vapour and precursors decide nature of water vapour dependence of O 3. • The seasonal variation of tropospheric O 3 is altitude-dependent. • Tropospheric column O 3 contributes about 16% of the total column O 3. [ABSTRACT FROM AUTHOR]