Snow data assimilation at ECMWF
Rosnay, Patricia de ; Isaksen, Lars ; Dahoui, Mohamed
Over the last few years, significant changes to snow analysis have been implemented in the operational ECMWF land data assimilation system. The Optimal Interpolation interface to observations was revised, allowing the implementation of land surface observation monitoring capabilities for snow and screen-level observations in Cycle 40r1 of ECMWF's Integrated Forecasting System (IFS). Developments also include improvements in the combined use of snow depth and snow cover data. Cycle 40r1 has been operational since November 2013. An evaluation against independent observations shows that the revised snow data assimilation performs better than the earlier version on a range of scores. The revision has brought clear improvements both in snow depth and near-surface weather parameter forecasts. Continuous observation monitoring provides evidence of the high quality of short-range ECMWF snow depth forecasts, but it also shows a slight continuing overestimation of snow depth in the background field and the analysis compared with independent observations.
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