Improved hydrometeor detection near the Earth's surface by a conically scanning spaceborne W-band radar

Abstract. The Earth's strong radar surface return limits the detection of clouds and precipitation in the lowest part of the atmosphere by nadir-pointing spaceborne radars such as CloudSat and EarthCARE. The strength of the Earth's surface radar return is significantly reduced at non-zero incidence angles. The WIVERN (WInd Velocity Radar Nephoscope) 94 GHz radar, currently undergoing Phase-A studies by ESA, employs a 3 m antenna and conical radar sampling at high incidence angles. Here, the benefits of the narrow field of view and the reduction in the Earth's surface return for studying clouds and precipitation in the lowest kilometres of the atmosphere are quantified. The WIVERN radar is expected to improve the ratio of signal (hydrometeors) to clutter (surface return) over ice-free ocean surfaces and marginally worsen it over land and sea ice. The impact of these findings on the detection of light rainfall and snowfall near the Earth's surface is discussed.