Deviation from a Hydrostatic Atmosphere in Radio Occultation Data

Summary. A 1D Var sensitivity study of simulated radio occultation measurements is presented. Temperature and water vapor proles are retrieved, along with a refer-ence pressure to generate the pressure prole by applying the hydrostatic equation. High resolution European Center for Medium Range Weather Forecasts (ECMWF) atmospheric elds are used with a ray tracing tool to calculate the exact positions of the tangent point. The atmospheric proles following the calculated tangent points trajectory in the 3D ECMWF elds are used to simulate bending angle measure-ments with a 1D forward model. Assimilation of these bending angles in a 1D Var tool employing the same 1D forward model is performed. We analyze the sensitivity of the retrieval to the assumption of hydrostatic equilibrium for a non-vertical at-mospheric scan. Deviations of more than 1 % from a hydrostatic pressure prole can occur for certain mid-latitude and polar conditions. The eect upon the retrieval capabilities is usually negligible except for the most extreme cases.