Abstract
Abstract. The objectives of the INSAT-3D satellite are to enhance the meteorological observations and to monitor the Earth's surface for weather forecasting and disaster warning. One of the weather-monitoring capabilities of the INSAT-3D sounder is the estimation of water vapour in the atmosphere. The amount of water vapour present in the atmospheric column is derived as the total precipitable water (TPW) product from the infrared radiances measured by the INSAT-3D sounder. The present study is based on TPW derived from INSAT-3D sounder, radiosonde (RS) observations and the corresponding National Oceanic and Atmospheric Administration (NOAA) satellite. To assess retrieval performances of INSAT-3D sounder-derived TPW, RS TPW observations are considered for the validation from May to September 2016 from 34 stations belonging to the India Meteorological Department (IMD). The analysis is performed on daily, monthly, and subdivisional bases over the Indian region. The comparison of INSAT-3D TPW with RS TPW on daily and monthly bases shows that the root mean square error (RMSE) and correlation coefficients (CC) are ∼8 mm and 0.8, respectively. However, on subdivisional and overall scales, the RMSE found to be in the range of 1 to 2 mm and CC was around 0.9 in comparison with RS and NOAA. The spatial distribution of INSAT-3D TPW with actual rainfall observation is also investigated. In general, INSAT-3D TPW corresponds well with rainfall observation; however, it has found that heavy rainfall events occur in the presence of high TPW values. In addition, the cases of thunderstorm events were assessed using TPW from INSAT-3D and network of Global Navigation Satellite System (GNSS) receiver. This shows the good agreement between TPW from INSAT-3D and GNSS during the mesoscale activity. The improvement in the estimation of TPW is carried out by applying the GSICS calibration corrections (Global Space-based Inter-Calibration System) to the radiances from infrared (IR) channels of the sounder, which is used by IMDPS (INSAT Meteorological Data Processing System). The current TPW from INSAT-3D satellite can be utilized operationally for weather monitoring and forecast purposes. It can also offer substantial opportunities for improvement in nowcasting studies.
Highlights
Water vapour is one of the most variable quantities in the troposphere, playing a crucial role in the climate and weather
We extended the work with 34 RS stations and taking National Oceanic and Atmospheric Administration (NOAA) data on daily, monthly, and subdivisional scales followed by the case studies of thunderstorm events with an India Meteorological Department (IMD)-installed network of Global Navigation Satellite System (GNSS) total precipitable water (TPW)
Five different regions were categorized according to meteorological subdivisions: northern India (NI), eastern India (EI), central India (CI), western India (WI) and peninsular India (PS) (Fig. 2)
Summary
Water vapour is one of the most variable quantities in the troposphere, playing a crucial role in the climate and weather It regulates air temperature by absorbing thermal radiation both from the Sun and the Earth; it is directly proportional to the latent energy available for the generation of storms; and it is the ultimate source of all forms of condensation and precipitation. The TPW may be used for monitoring the mesoscale to synoptic-scale convective activity, monsoonal activities, and moisture gradients. It has shown a significant improvement in precipitation forecasts when TPW is incorporated in the numerical weather prediction models (Kuo et al, 1996). The water vapour varies in time and in space (both vertically and horizontally) and the gaps in the observations makes its use Published by Copernicus Publications on behalf of the European Geosciences Union
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