Observing system simulation experiments for three-dimensional wind fields generated by tracking humidity features in hyperspectral sounder retrieved profiles
AbstractAbstractThe three-dimensional (3D) global wind field is critical for understanding the general circulation and initializing numerical weather prediction models. Although imagers on the polar and geostationary satellites provide wind information through atmospheric motion vectors (AMVs) by tracking cloud motion, they fail to adequately sample the clear-air mass prevalent in the midtroposphere. This gap can be addressed using AMVs on discrete pressure levels (3D winds) retrieved by tracking moisture from hyperspectral infrared soundings. Observing system simulation experiments (OSSEs) were conducted for AMVs derived from two satellite orbital constellations with different spatial coverage—one providing well-distributed global coverage and the other exhibiting coverage gaps at the mid- and low latitudes, with these gaps shifting longitudinally over time. Both configurations improved global forecasts, especially the wind fields, with the globally distributed constellation yielding greater benefits. Forecast improvements were more pronounced in the Southern Hemisphere, likely due to the sparse radiosonde network. Despite better wind analyses in the tropics, tropospheric temperature forecasts degraded there. This degradation may stem from climatological differences between the nature run and the Global Forecast System (GFS) or from suboptimal background error covariances for AMV assimilation. Future assimilation of real 3D wind observations will help validate these OSSE results and clarify the cause of the tropical temperature degradation.Significance StatementThe results of this paper are significant because more hyperspectral sounders are being launched by various countries. Their data can be used to derive three-dimensional winds, providing broad observational coverage and enabling these observations to positively impact global forecasts.
