Estimating Eliassen-Palm flux using COSMIC radio occultation

We present a methodology for analyzing the Eliassen-Palm (E-P) flux in the troposphere and stratosphere using GPS radio occultation data from the COSMIC project. In this methodology, geopotential height and temperature are mapped on constant pressure surfaces using a Bayesian interpolation scheme with a spherical harmonic basis, and the components of the E-P flux are evaluated using geostrophic winds. We perform a simulation-analysis study using the NCEP/NCAR Reanalysis as truth. E-P fluxes are evaluated daily, and it is found that patterns of E-P flux are estimated faithfully, and extrema in the vertical and horizontal components are underestimated by 5 - 10% and by 30 - 40%, respectively. Monthly hemispheric averages of the vertical component of the E-P flux at the tropopause can be estimated to < 5%. The error is due to the geostrophic approximation and spatial coverage, mostly the latter: COSMIC GPS radio occultation only resolves atmospheric eddies with scales greater than 1000 km on a daily basis.