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Balloon-borne cryogenic frost-point hygrometer (CFH) observations over two tropical stations Trivandrum (8.53° N, 76.87° E) and Hyderabad (17.47° N, 78.58° E) [2014–2017] along with Microwave Limb Sounder (MLS) observations [2011–2017] are used to examine the signatures of local and regional dynamics in the distribution of lower stratospheric water vapour over the Indian region. The column-integrated water vapour in the lower stratosphere (IWVLS) varies in the range 2.5–5 g/m2 with low values during winter and high values during summer monsoon and post monsoon seasons. About 50–75% of IWVLS lies in the lower regime of the lower stratosphere, the region from cold point tropopause (CPT) to 21 km (LS1). Hygropause is very near to the CPT in winter and pre-monsoon and 2–3 km above the CPT in summer-monsoon and post-monsoon. The CPT and the minimum in saturated mixing ratio (SMRmin) altitudes show a positive correlation, with SMRmin mostly occurring below the CPT. Though water vapour mixing ratio (WVMR) at CPT increases with increase in SMRmin, it is mostly less than the corresponding SMRmin value. CFH observations showed that the tape recorder signal in the LS1 is disturbed by the local/regional dynamics. While the amount of water vapour entering the lower stratosphere is higher over Hyderabad in winter and summer monsoon, it is higher over Trivandrum in the other two seasons. Hydration at the tropopause level is mainly determined by the overshooting/deep convection, monsoon dynamics and horizontal transport and dehydration is determined by temperature variations in the tropical tropopause layer (TTL). [ABSTRACT FROM AUTHOR]

Cirrus clouds play a crucial role in regulating the Earth's radiation budget, and this paper aims to contribute to a deeper understanding of their optical and geometrical properties over the Arabian Sea (AS) and Bay of Bengal (BoB) regions using CALIPSO data. Comprehensive statistics are derived, encompassing mean values of cirrus cloud top, base altitude, geometrical thickness, cloud optical depth, and temperature. Over the AS region, the mean values are 15.10 ± 1.50 km, 12.63 ± 1.75 km, 2.52 ± 1.37 km, 0.4 ± 0.58, and -62.30 ± 10.6 (°C), respectively. For the BoB region, the corresponding values are 15.43 ± 1.51 km, 12.72 ± 1.74 km, 2.71 ± 1.46 km, 0.49 ± 0.67, and -64.35 ± 10.7 (°C). A larger spread in optical depth and a higher frequency of occurrence for both cirrus and subvisible cirrus (SVC) clouds were observed over BoB compared to AS. Additionally, the study delves into SVC cloud characteristics, emphasizing their thinness and higher base altitudes compared to cirrus clouds. This comprehensive investigation contributes valuable insights into the distinctive properties of cirrus and SVC clouds in these regions, enhancing our knowledge of atmospheric processes and their implications for climate modelling and predictions. • Spatial variability of SVC and cirrus cloud over ISMR region using CALIPSO data • Detailed analysis of physical and optical properties of cirrus and SVC over AS and BoB • Higher optical depth range and occurrence frequency of cirrus and SVC over BoB. [ABSTRACT FROM AUTHOR]

This paper assesses the performance of water vapor measurements by Sondeur Atmosphérique du Profild’ Humidité Intertropicale par Radiométrie (SAPHIR), microwave limb sounder (MLS), and the global reanalysis water vapor data [Modern Era Retrospective analysis for Research and Applications (MERRA) and European Center for Medium-Range Weather Forecasts reanalysis (ERA) interim] by comparing with water vapor-measured in situ by cryogenic frost-point hygrometer (CFH) at two tropical stations, Trivandrum (8.5°N, 76.9°E) and Hyderabad (17.47°N, 78.58°E). The iMet-1 radiosonde though overestimates frost-point temperature (3%–5%) in the 4–10-km altitude region with respect to CFH, it agrees well with CFH observations in the upper troposphere and the lower troposphere with a mean difference <2% and ~1%, respectively. SAPHIR–CFH intercomparison is done for the troposphere region, and MLS, MERRA, and ERA interim are compared with CFH in the lower stratosphere region. SAPHIR and CFH comparison shows a reasonable agreement between both the datasets with a relative humidity difference of about 15% in the lower and middle troposphere and a dry bias of ~40% in the upper troposphere. Intercomparison between CFH and MLS water vapor mixing ratios (WVMRs) shows a small wet bias (−10% to −20%) for the MLS in the lower stratospheric region between 100 and 50 hPa and a small dry bias (<10%) above that region. This paper shows that the MLS always underestimates when the CFH WVMR is greater than 6 ppmv and overestimates when the WVMR is less than 2 ppmv. The intercomparison of CFH with MERRA and ERA interim specific humidity shows results similar to that with MLS. [ABSTRACT FROM AUTHOR]

Abstract Diurnal variation of atmospheric water vapour in the troposphere over two tropical stations Trivandrum (8.5°N, 76.9°E) and Gadanki (13.5°N, 79.2°E) are studied using radiosonde observations for three years (December 2010–March 2014) carried out as part of Tropical Tropopause dynamics (TTD) campaigns under CAWSES (Climate And Weather of the Sun-Earth System) India Phase II program. Trivandrum is a coastal station and Gadanki an inland station in the Indian Peninsula. Even though the absolute value of columnar integrated water vapour content (IWV) is higher over Trivandrum in all the seasons, the amplitude of its diurnal variation is almost the same (∼± 5–8 kg m−2) at both the stations with lower values during the day and higher values during night. Though the absolute humidity decreases exponentially with altitude, the amplitude of normalized diurnal anomaly is more-or-less the same (15–20%) from the surface up to 10 km in all the seasons. There exists a time difference in the peaking hours of water vapour density between the two stations with Gadanki always leading Trivandrum. While the water vapour density maximizes around midnight over Trivandrum, it peaks in the late evening over Gadanki. Harmonic analysis shows that the diurnal and semi-diurnal components together account for almost all the sub-daily variations in IWV and absolute humidity. The contribution of semi-diurnal component is only 25% of that of the diurnal component. Diurnal variation of surface wind speed and direction together with the vertical motion associated with convection regulated by the diurnal variation in temperature seems to play the lead role in causing the diurnal variation in water vapour. While the diurnal variation over Gadanki is mainly controlled by the convectively induced vertical motion, the diurnal variation in the rate of evaporation due to surface wind and local circulation also plays a significant role over Trivandrum. Highlights • Diurnal variation of tropospheric water vapour over Indian peninsula delineated using 3 hourly radiosonde data. • The diurnal and semi-diurnal components together could account for almost all the sub-daily variability in water vapour. • Local dynamics regulated by the surface temperature causes the diurnal variability in water vapour. [ABSTRACT FROM AUTHOR]

Balloon-borne experiments carried out onboard ORV Sagar Kanya over the Arabian Sea (AS) and Equatorial Indian Ocean (EIO) during the period 16 January 2018–14 February 2018 in northern hemisphere winter are used to study the spatio-temporal distribution of tropospheric water vapour. The column-integrated water vapour (IWV) showed an increase of ~10 kg/m2 over the Equatorial Indian Ocean (EIO) compared to that over Arabian Sea (AS). Amount of water vapour in the free troposphere increases towards south with water vapour enhancement observed up to an altitude of 12 km over the equator. This is mainly due to convective outflows emanating from the Inter Tropical Convergence Zone (ITCZ). Along 2°S, the IWV showed an east–west (75–65°E) gradient with high values in the east. During the return leg of the ship cruise, when the AS is convectively disturbed with cloud tops extending up to mid-troposphere, the IWV showed an increase of about 10–15 kg/m2 compared to that observed during onward leg under fair weather conditions, particularly due to the accumulation of water vapour in the 2–7 km altitude region. Over the deep ocean the diurnal amplitude of water vapour shows a clear altitude variation with lesser amplitude in the lower troposphere compared to land. • An enhancement of ~ 10 kg/m2 in tropospheric water vapour from 15°N to equator. • Convective hydration cause an increase of 10–15 kg/m2 of water vapour over ocean. • Diurnal amplitude of lower tropospheric water vapour is smaller over the deep ocean compared to land. [ABSTRACT FROM AUTHOR]

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]

Balloon-borne cryogenic frost-point hygrometer (CFH) observations of water vapour in the upper troposphere and lower stratosphere (UTLS) region carried out over India, from Trivandrum [8.5°N, 76.9°E] and Hyderabad [17.5°N, 78.6°E], were compared with that obtained from quasi-collocated Aura-Microwave Limb Sounder (MLS) satellite observations. Comparisons show a small dry bias for MLS in the stratosphere. Saturated or super-saturation layers observed near the base of tropical tropopause layer (TTL) are consistent with the quasi-collocated space-based observations of tropical cirrus from KALPANA-1 and CALIPSO. Disturbance of large scale waves in the upper troposphere appears to modulate the water vapour and cirrus distribution. [ABSTRACT FROM AUTHOR]

Background: A fast and simple two-step multiplex real-time PCR assay has been developed to replace the traditional, laborious Salmonella serotyping procedure. Molecular beacons were incorporated into the assay as probes for target DNA. Target sequences were regions of the invA, prot6E and fliC genes specific for Salmonella spp. Salmonella Enteritidis and Salmonella Typhimurium, respectively, the two most clinically relevant serotypes. An internal amplification positive control was included in the experiment to ensure the optimal functioning of the PCR and detect possible PCR inhibition. Three sets of primers were used for the amplification of the target sequences. The results were compared to those of the Kauffmann-White antigenic classification scheme. Results: The assay was 100% sensitive and specific, correctly identifying all 44 Salmonella strains, all 21 samples of S. Enteritidis and all 17 samples of S. Typhimurium tested in this work. Therefore, the entire experiment had specificity and sensitivity of 100%. The detection limit was down to 10 copies of DNA target per 25 µl reaction. Conclusion: The assay can amplify and analyse a large number of samples in approximately 8 hours, compared to the 4 to 5 days conventional identification takes, and is thus considered a very promising method for detecting the two major serotypes of Salmonella quickly and accurately from clinical and environmental samples. [ABSTRACT FROM AUTHOR]

Seasonal variability in the vertical distribution of ozone over a tropical station, Thumba (8.5°N, 76.9°E) is investigated using nine-years (2011–2019) of ECC ozonesonde data obtained as part of Tropical Tropopause Dynamics (TTD) campaigns. Ozone exhibits a clear annual variation in the lower troposphere (0–2 km) with winter maximum (49.2 ± 3.6 ppbv) and summer monsoon minimum (21.9 ± 0.7 ppbv). In the middle (2–10 km) and upper (11–17 km) troposphere, ozone is maximum in pre-monsoon and minimum in summer monsoon. Ozone in the lower stratosphere exhibits a clear annual variation with summer monsoon maximum and winter minimum in tandem with the temperature cycle. The relative standard deviation (RSD) of ozone computed at different altitudes exhibits large intra-seasonal variability in the troposphere (~20–30%) compared to the stratosphere (~5%) and is significantly high close to the surface and in the tropical tropopause layer (TTL) (≥30%). Maximum RSD is observed during summer monsoon (June–September) in the upper troposphere (~50%) close to cold point tropopause (CPT). RSD in ozone and temperature profiles show a sharp peak immediately above the CPT in all the seasons, coinciding with the altitude of maximum wind shear. Tropospheric ozone shows an in phase relationship with temperature and is opposite in phase with water vapour. A significant negative correlation is observed between ozone and water vapour in the 2–5 km altitude region. Long-range transport and local convection contribute substantially to the observed variability in tropospheric ozone. The tropospheric column ozone shows a semi-annual variation with maximum contribution to the total columnar ozone during pre-monsoon (~16%) and minimum during summer monsoon (~8%). Mid-tropospheric ozone contributes more to the tropospheric column ozone (40–60%) compared to lower and upper tropospheric ozone. Tropospheric column ozone exhibits a similar seasonality as that of its precursors like NO 2 , CO and CH 4. • Ozone distributions shows high intraseasonal variability near the CPT. • Local convection and long-range transport determine tropospheric ozone variability. • Significant contribution to the tropospheric column ozone is from the mid-troposphere. [ABSTRACT FROM AUTHOR]

Altitude structure of turbulence in the troposphere and lower stratosphere (TLS) over the Indian peninsula is delineated using radiosonde observations carried out from six stations (August 2013 to December 2017) as part of the Tropical Tropopause Dynamics (TTD) Campaign under the GPS Aided Radiosonde Network Experiment for Troposphere–stratosphere Studies (GARNETS) program. Thorpe analysis applied to the potential temperature profiles, taking into account the impact of atmospheric moisture and instrumental noise, is used to estimate the turbulence parameters. This study shows that while the occurrence of turbulence is high in the lower (0–2 km) and upper (10–15 km) troposphere, the region 3–8 km is relatively devoid of turbulence at all the six stations. In general, ~60% of the Thorpe scale (L T) values in the troposphere are less than 250 m at all the stations, except at Cochin where it extends up to 400 m. Though the altitudinal structure of turbulence shows large variability from station-to-station, it does not show any systematic latitudinal pattern. This study also shows that the Thorpe method appears to be good in identifying convectively induced turbulence than the dynamically (shear) induced turbulence. In the lower troposphere, the turbulence is due to both convective and dynamic instability at all the stations. While turbulence in the altitude region between 10 and 15 km is mainly due to convective instability at Coimbatore, Gadanki and Goa and due to dynamic instability at Cochin, both these instabilities contribute significantly to the generation of turbulence at Trivandrum and Hyderabad. Occurrence of convective instability (turbulence) under clear-air conditions in the upper troposphere, suggests wave breaking as a mechanism. • Altitude structure of turbulence studied over six locations of Indian peninsula. • Occurrence of turbulence is high in the lower and upper troposphere. • There is no systematic station to station variations in the turbulent structure. • Convective and dynamical instabilities are responsible for the turbulence generation. • Thorpe method appears to be good in identifying convectively induced turbulence. [ABSTRACT FROM AUTHOR]