Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-280
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
12 Apr 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Improved rain-rate and drop-size retrievals from airborne and spaceborne Doppler radar
Shannon L. Mason1,2, J. Christine Chiu1,2, Robin J. Hogan1,3, and Lin Tian4,5 1Department of Meteorology, University of Reading, Reading, UK
2National Centre for Earth Observation, University of Reading, Reading, UK
3European Centre for Medium-range Weather Forecasts, Reading, UK
4NASA Goddard Space Flight Centre, Greenbelt MD, USA
5Morgan State University, Baltimore MD, USA
Abstract. Satellite radar remote-sensing of rain is important for quantifying of the global hydrological cycle, atmospheric energy budget, and many microphysical cloud and precipitation processes; however, radar estimates of rain rate are sensitive to assumptions about the raindrop size distribution. The upcoming EarthCARE satellite will feature a 94-GHz Doppler radar alongside lidar and radiometer instruments, presenting opportunities for enhanced global retrievals of the rain drop size distribution.

In this paper we demonstrate the capability to retrieve both rain rate and a parameter of the rain drop size distribution from an airborne 94-GHz Doppler radar using CAPTIVATE, the variational retrieval algorithm developed for EarthCARE radar–lidar synergy. For a range of rain regimes observed during the Tropical Composition, Cloud and Climate Coupling (TC4) field campaign in the eastern Pacific in 2007, we explore the contributions of Doppler velocity and path-integrated attenuation (PIA) to the retrievals, and evaluate the retrievals against independent measurements from a second, less attenuated, Doppler radar aboard the same aircraft. Retrieved drop number concentration varied over five orders of magnitude between light rain from melting ice, and warm rain from liquid clouds. Doppler velocity can be used to estimate rain rate over land, and retrievals of rain rate and drop number concentration are possible in profiles of light rain over land; in moderate warm rain, drop number concentration can be retrieved without Doppler velocity. These results suggest that EarthCARE rain retrievals facilitated by Doppler radar will make substantial improvements to the global understanding of the interaction of clouds and precipitation.


Citation: Mason, S. L., Chiu, J. C., Hogan, R. J., and Tian, L.: Improved rain-rate and drop-size retrievals from airborne and spaceborne Doppler radar, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-280, in review, 2017.
Shannon L. Mason et al.
Shannon L. Mason et al.
Shannon L. Mason et al.

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Short summary
Airborne Doppler radar measurements are used to estimate the properties of tropical stratiform rain. Doppler velocity measurements provide sufficient information to estimate rain rate over land, and to also retrieve the raindrop size distribution over ocean, addressing major uncertainties in current satellite measurements of rain. These results suggest that EarthCARE, with the first spaceborne Doppler radar, will facilitate improved global measurements of rain.
Airborne Doppler radar measurements are used to estimate the properties of tropical stratiform...
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