Potential of INSAT-3D sounder-derived total precipitable water product for weather forecast
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.