Utility of GNSS Radio Occultation technique for tropopause height investigation over Egypt

ABSTRACT Global Navigation Satellite System (GNSS) Radio Occultation (RO) is an active limb sounding technique, where GNSS satellites transmitted signals passing through the atmosphere of the Earth and received by a GNSS receiver on low earth orbiter (LEO) satellite. RO provides accurate atmospheric refractivity profile. RO technique has been widely used to study the atmosphere of planets. This paper investigates the use of GNSS RO for tropopause height (TPH) estimation as one of the key climate parameters over Egypt. TPH is also very important in determining the wet delay in GNSS analysis. Two years (2016 and 2017) of MetOP A and B satellites data are used. ROPP software package is used in the analysis. For validation of the results, RO-derived TPH is compared with European Centre for Medium-Range Weather Forecast (ECMWF) model as well as radiosonde (RS). Good agreement and high correlation are found between TPH from RO and ECMWF and RS on the other hand. TPH varies between 14 and 16 km over Egypt. It decreases with latitude and shows no clear trend with longitude. Tropopause temperature is found to increase with latitude