Spatial structures and statistics of atmospheric gravity waves derived using a heuristic vertical cross‐section extraction from COSMIC GPS radio occultation data

Abstract

A number of studies have investigated atmospheric gravity waves (GWs) using temperature profiles from GPS radio occultation (RO). This study is the first to report the horizontal structures of GWs obtained directly by using multiple profiles based on the GPS RO data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC)/FORMOSAT‐3 mission. It was found that the horizontal locations of profiles obtained from successive passages of multiple COSMIC satellites were frequently aligned quasi‐linearly over distances of around 1500–5000 km. Therefore, almost instantaneous (within 1 h) snapshots of vertical‐horizontal cross sections of atmospheric temperature could be obtained. Clear GW features over multiple occultations were identified in many of the cross sections. It was indicated from a statistical analysis that horizontal wavelengths of GWs in the winter (here northern) hemisphere were generally smaller than those in the equatorial region or in the other hemisphere. A positive skewness was found in the probability distribution of the GW amplitude in middle to high latitudes, while the distribution was not skewed in low latitudes. GWs in the northern midlatitudes were studied further. In the zonal direction, both eastward and westward propagations relative to background winds were identified. The GW amplitude had a negative correlation with zonal wind shear. In the meridional direction, northward propagation was dominant, indicating that the dominant source region of meridionally propagating GWs was in the subtropics.