Daily Climatological Fields Based on GNSS Radio Occultation Measurements: A Feasibility Study

GNSS Radio occultation (RO) technique can provide high-quality measurements of the Earth’s atmosphere. Monthly (or seasonly) RO climatological fields have been widely used in climate and weather studies. However, the low temporal resolution makes it difficult in resolving the rapid variations in the atmosphere. Here we established the daily climatological fields by GNSS RO measurements from the Constellation Observing System for Meteorology, Ionosphere, and Climate. By applying a “point” strategy, RO profiles are assimilated into a 3°×3° longitude-latitude global grid through the Gaussian weighting function. By comparison between the RO climatological fields and European Centre for Medium Range Weather Forecasts reanalysis, the differences display distinctive features in different layers of the Earth’s atmosphere. The overall differences are about 2 K, 1.5% and 40 m (temperature, density, and geopotential height) in the lower troposphere; 1 K, 0.5% and 40 m in the upper troposphere and lower stratosphere region; and 2 K, 1% and 100 m in the upper stratosphere. The results have demonstrated that the observation-based RO climatological fields are reliable in both northern and southern hemispheres.