Investigating the Impact of RapidSCAT in the GEOS-5 Data Assimilation System

The RapidScat instrument was launched by NASA in Fall of 2014 and is onboard the International Space Station (ISS). Built as a low-cost follow-on to the QuikScat mission, the instrument measures sea surface roughness from two viewing angles and retrieves an estimate of surface wind. Contrary to traditional scatterometers, for example the SeaWinds instrument on QuikScat and the Advanced Scatterometer (ASCAT) onboard the Metop platforms, RapidScat is flying in a non-sun-synchronous, low-inclination orbit. The orbital track of the ISS results in coverage that is complementary to the two ASCAT instruments, both of which are in mid-morning, sun-synchronous orbits.

As RapidScat is the first instrument onboard the ISS to be considered for routine operations, this study will present both the impact of the observations using traditional data assimilation metrics (e.g. observation statistics, forecast skills, adjoint-derived observation impacts). Additionally, the benefit of these observations on situation-specific events (e.g. sparsely observed tropical storms and midlatitude cyclones) will also be shown. It is noted that other than where the ISS orbits overlap with the Metop platforms, RapidScat is providing observations in areas that are otherwise generally unsampled. Therefore, a noted impact on case-specific events is expected.