Title: Horizontal resolution impact on forecast error growth
Abstract: The error growth of ECMWF instantaneous forecasts with horizontal spectral truncation from T95 to T799 is analyzed. Attention is focused on synoptic-scale features represented by the 500 and 1000 hPa geopotential height and the 850 hPa temperature over the Northern Hemisphere winter. Forecast skill is investigated by applying a three-parameter model of forecast error growth, and forecast accuracy is measured by computing the time limits when fractions of the forecast error asymptotic value are reached in an idealized and a realistic framework. A strong sensitivity of forecast skill to model resolution has been found in the short and medium forecast range (say up to about forecast day 7), becoming weaker in the long forecast range. In the case of T799 forecasts verified in the realistic framework, the long range time limit τ(95%) has been estimated to be 14±2 days. Resolution increases have been providing continuously better forecasts especially in the short forecast range. Results indicate that while further increases in resolution are expected to further improve the forecast skill in the short and medium forecast range, simple resolution increases without model improvements would bring only very small improvements in the long forecast range.
Publication Year: 2010
Publication Date: 2010-05-01
Language: en
Type: article
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