A comparison of temperature and relative humidity measurements derived from COSMIC-2 radio occultations with radiosonde observations made over the Asian summer monsoon region
Venugopal Veenus, Siddarth Shankar Das, Bukya Sama, K. N. Uma
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.