A comparison of temperature and relative humidity measurements derived from COSMIC-2 radio occultations with radiosonde observations made over the Asian summer monsoon region

ABSTRACT

The newly launched FORMOSAT-7/COSMIC-2 (Formosa Satellite Mission-7 and Constellation Observing System for Meteorology, Ionosphere, and Climate-2), has an equatorial constellation of six satellites carrying advanced radio occultation receivers, providing high-resolution measurements of temperature and humidity between 45° N to 45° S. COSMIC-2 provides global data of about 5000–6000 profiles per day and has better profiling over the tropics as compared to FORMOSAT-3/COSMIC-1. The vertical resolution of COSMIC-2 (50 m up to tropopause) is better than COSMIC-1 (100 m). In this study, two years of COSMIC-2 measurements are compared with radiosonde observations over the Asian summer monsoon region, which is a highly monsoon active region and a gateway for stratospheric pollutants. The present study analysed the accuracy of temperature and water vapour measurements in the lower and middle atmosphere. A very good agreement between COSMIC-2 and radiosonde measured temperature by an absolute mean difference of less than 0.5 K with a standard deviation of less than 2.5 K is observed. Relative humidity shows a mean difference of 10% with a standard deviation of 15–20%. These results indicate that the COSMIC-2 sounding is robust, has high accuracy, and has excellent global coverage, especially over the tropical and sub-tropical regions.

Acknowledgments

The authors greatly appreciate the team of COSMIC-2 for providing valuable data through COSMIC Analysis and Archive Centre, ECMWF for the ERA5 data, India Meteorological Department and University of Wyoming for radiosonde data. The authors Veenus Venugopal and Bukya Sama thank the Indian Space Research Organisation for providing doctoral fellowship during the study period.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Publicly available datasets were analysed in this study. COSMIC-2 data is available in the website https://data.cosmic.ucar.edu/gnss-ro/cosmic2/nrt/level2/ (10.5065 /t353-c093). Radiosonde data are available from the University of Wyoming sounding data archive http://weather.uwyo.edu/upperair/sounding.html. ERA5 reanalysis data were downloaded from https://cds.climate.copernicus.eu: (10.24381/cds.adbb 2d47).

Supplementary material

Supplemental data for this article can be accessed here.