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Atmos. Meas. Tech., 11, 3091-3109, 2018
https://doi.org/10.5194/amt-11-3091-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
30 May 2018
Evaluating tropospheric humidity from GPS radio occultation, radiosonde, and AIRS from high-resolution time series
Therese Rieckh1,2, Richard Anthes1, William Randel3, Shu-Peng Ho1, and Ulrich Foelsche4,2 1COSMIC Program Office, University Corporation for Atmospheric Research (UCAR), Boulder, Colorado, USA
2Wegener Center for Climate and Global Change (WEGC), University of Graz, Graz, Austria
3National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
4Institute for Geophysics, Astrophysics, and Meteorology/Institute of Physics, University of Graz, Graz, Austria
Abstract. While water vapor is the most important tropospheric greenhouse gas, it is also highly variable in both space and time, and water vapor concentrations range over 3 orders of magnitude in the troposphere. These properties challenge all observing systems to accurately measure and resolve the vertical structure and variability of tropospheric humidity. In this study we characterize the humidity measurements of various observing techniques, including four separate Global Positioning System (GPS) radio occultation (RO) humidity retrievals (University Corporation for Atmospheric Research (UCAR) direct, UCAR one-dimensional variational retrieval (1D-Var), Wegener Center for Climate and Global Change (WEGC) 1D-Var, Jet Propulsion Laboratory (JPL) direct), radiosonde, and Atmospheric Infrared Sounder (AIRS) data. Furthermore, we evaluate how well the ERA-Interim reanalysis and NCEP Global Forecast System (GFS) model perform in analyzing water vapor at different levels. To investigate detailed vertical structure, we analyzed time–height cross sections over four radiosonde stations in the tropical and subtropical western Pacific for the year 2007. We found that the accuracy of RO humidity is comparable to or better than both radiosonde and AIRS humidity over 800 to 400 hPa, as well as below 800 hPa if super-refraction is absent. The various RO retrievals of specific humidity agree within 20 % in the 1000–400 hPa layer, and differences are most pronounced above 600 hPa.
Citation: Rieckh, T., Anthes, R., Randel, W., Ho, S.-P., and Foelsche, U.: Evaluating tropospheric humidity from GPS radio occultation, radiosonde, and AIRS from high-resolution time series, Atmos. Meas. Tech., 11, 3091-3109, https://doi.org/10.5194/amt-11-3091-2018, 2018.
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Short summary
Water vapor is the most important tropospheric greenhouse gas and is also highly variable in space and time. We study the vertical structure and variability of tropospheric humidity using various observing techniques (GPS radio occultation, radiosondes, Atmospheric Infrared Sounder) and models. Time–height cross sections reveal seasonal biases for different pressure layers. We find that radio occultation humidity has high accuracy and can contribute valuable information in data assimilation.
Water vapor is the most important tropospheric greenhouse gas and is also highly variable in...
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