Sensitivity of NWP model skill to the obliquity of the GPS radio occultation soundings

Abstract

The impact of accounting for the drift of the tangent point of the global positioning system radio occultation (GPS RO) profiles within a data assimilation system has been investigated. The GPS RO processing centers provide geographic coordinates for each retrieved value within a profile, as well as profile-representative coordinates. Instead of assimilating each retrieved value with its corresponding latitude and longitude, several numerical weather prediction (NWP) centers have alternatively been using the profile-representative horizontal coordinates. This study shows that this simplification of the geometry of the GPS RO data should be avoided when possible in order to get optimal results in terms of NWP forecast skill. © 2011 Royal Meteorological Society.