title: Deriving dynamics from GPS radio occultation: Three-dimensional wind fields for monitoring the climate.
abstract: Global Positioning System (GPS) radio occultation (RO) measurements are proven highly useful for observing the thermal structure of the troposphere and stratosphere. Here we use RO data for the first time to derive climatological wind fields from sampling error-corrected geopotential height fields on isobaric surfaces from about 800 hPa to 3 hPa. We find monthly mean RO geostrophic wind and gradient wind fields (2007 to 2012, about 500 km horizontal resolution, outside tropics) to clearly capture all main wind features, with differences to atmospheric analysis winds being, in general, smaller than 2 m/s. Larger differences (up to 10 m/s) occur close to the subtropical jet where RO winds underestimate actual winds. Such biases are caused by the geostrophic and gradient wind approximations, while RO retrieval errors introduce negligible effect. These results demonstrate that RO wind fields are of high quality and can provide new information on troposphere-stratosphere dynamics, for the benefit of monitoring the climate from weekly to decadal scales.
authors.affiliation: Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics (IGAM/IP), University of Graz Graz, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Scherllin-Pirscher
authors.affiliation: Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics (IGAM/IP), University of Graz Graz, Austria.
authors.forename: Andrea Karin
authors.initials: AK
authors.lastname: Steiner
authors.affiliation: Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics (IGAM/IP), University of Graz Graz, Austria.
authors.forename: Gottfried
authors.initials: G
authors.lastname: Kirchengast
keywords: GPS radio occultation; climate change; climate variability; geostrophic wind; gradient wind; troposphere and stratosphere