Intercomparison review of IPWV retrieved from INSAT-3DR sounder, GNSS and CAMS reanalysis data

Ramashray Yadav,Ram Kumar Giri,Virendra Singh

doi:10.5194/amt-14-4857-2021

Abstract

Abstract. The spatiotemporal variations of integrated precipitable water vapor (IPWV) are very important in understanding the regional variability of water vapor. Traditional in situ measurements of IPWV in the Indian region are limited, and therefore the performance of satellite and Copernicus Atmosphere Meteorological Service (CAMS) retrievals with the Indian Global Navigation Satellite System (GNSS) as reference were analyzed. In this study the CAMS reanalysis data of 1 year (2018) and the Indian GNSS and INSAT-3DR sounder retrieval data for 1.5 years (January 2017 to June 2018) were utilized, and statistics were computed. It is noticed that seasonal correlation coefficient (CC) values between INSAT-3DR and Indian GNSS data mainly lie within the range of 0.50 to 0.98 for all the selected 19 stations except Thiruvananthapuram (0.1), Kanyakumari (0.31) and Karaikal (0.15) during the monsoon season and Panjim (0.2) during the post-monsoon season. The seasonal CC values between CAMS and GNSS IPWV range from 0.73 to .99 except for Jaipur (0.16) and Bhubaneswar (0.29) during the pre-monsoon season, Panjim (0.38) during the monsoon season, Nagpur (0.50) during the post-monsoon season, and Dibrugarh (0.49) Jaipur (0.58) and Bhubaneswar (0.16) during the winter season. The root mean square error (RMSE) values are higher under the wet conditions (pre-monsoon and monsoon season) than under dry conditions (post-monsoon and winter season), and we found differences in magnitude and sign of bias for INSAT-3DR and CAMS with respect to GNSS IPWV from station to station and season to season. This study will help to improve understanding and utilization of CAMS and INSAT-3DR data more effectively along with GNSS data over land, coastal and desert locations in terms of the seasonal flow of IPWV, which is an essential integrated variable in forecasting applications.

Highlights

Integrated precipitable water vapor (IPWV) is a meteorological factor that shows the amount of water vapor contained in the column of air per unit area of the atmosphere in terms of the depth of liquid (Viswanadham, 1981)
An attempt was made to evaluate the integrated precipitable water vapor (IPWV) retrieved from the INSAT-3DR satellite, with Global Navigation Satellite System (GNSS) observations showing that the root mean square error (RMSE) of 8 inland stations out of 10 stations lies between 4 and 6 mm, but it lies between 8 and 12 mm for Jalpaiguri (JPGI) and Dibrugarh (DBGH) stations
The differences in the magnitude and sign of CC of INSAT-3DR with respect to Copernicus Atmosphere Monitoring Service (CAMS) reanalysis IPWV may be due to a lack of assimilation of quality-controlled data over the Indian domain

Summary

Introduction

Integrated precipitable water vapor (IPWV) is a meteorological factor that shows the amount of water vapor contained in the column of air per unit area of the atmosphere in terms of the depth of liquid (Viswanadham, 1981). This parameter is of great importance in all studies related to the atmosphere and its properties throughout the year and in all seasons. Especially absorption in the infrared and microwave region of the solar spectrum, have wide coverage, are cheaper, and are almost maintenance-free but need to validate their retrieval performance and intercomparison before being applied in the operational meteorological service domain. Each absorbing water vapor molecule emits radiation according to Planck’s law, mainly depending on its temperature, and the extent of absorption differs depending on the wavelength – the satellite sees different levels of atmosphere

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Conclusion