Publication Date:
2016-09-05
Description:
This study presents an assessment of the impact of a March 2006 change in the United Kingdom Met Office operational global numerical weather prediction model through the introduction of a non-local momentum mixing scheme. From comparisons with satellite observations of surface wind speed and sea-surface temperature (SST), it is concluded that the new parameterization had a relatively minor impact on SST-induced changes in sea surface wind speed in the Met Office model during the September and October 2007 monthly averages over the Agulhas Return Current region considered here. The performance of the new parameterization of vertical mixing was evaluated near the surface layer and further through comparisons with results obtained using a wide range of sensitivity of mixing parameterization to stability in the Weather Research and Forecasting (WRF) model, which is easily adapted to for such sensitivity studies. While the new parameterization of vertical mixing improves the Met Office model response to SST in highly unstable (convective) conditions, we conclude that significantly enhanced vertical mixing in the weak-to-moderately unstable conditions (non-dimensional stability –zi/L between 0 and 2) typically found over the ocean is required in order for the model surface wind response to SST to match the satellite observations. Likewise, the reduced mixing in stable conditions in the new parameterization is also relatively small; for the range of Richardson Number typically found over the ocean, the mixing was reduced by a maximum of only 10%.
Print ISSN:
0894-8755
Electronic ISSN:
1520-0442
Topics:
Geography
,
Geosciences
,
Physics
