The sensitivity of numerical forecasts to convective parameterization during the warm period and the use of lightning data as an indicator for convective occurrence

Abstract

The sensitivity of numerical model quantitative precipitation forecasts to the choice of the convective parameterization scheme (CPS) is examined for twenty selected cases characterized by intense convective activity and widespread precipitation over Greece, during the warm period of 2005–2007. Namely, the study is conducted using MM5 model and the following three different CPSs: Kain–Fritsch, Grell and Betts–Miller–Janjic. Sixty numerical simulations were carried out on two nested domains, with horizontal grid increments of 24 and 8 km respectively. The simulated precipitation from the 8-km grid was verified against raingauge measurements and lightning data provided by the ZEUS long-range lightning detection system, operated by the National Observatory of Athens. Verification results showed that for all three schemes the model presented a tendency to overestimate light to moderate rain while in general it underestimated the high precipitation amounts. The validation against both sources of data showed that among the three CPSs, the more consistent behavior in quantitative precipitation forecasting was obtained by the Kain–Fritsch scheme that provided the best statistical scores. However, the differences of the results of statistical analysis between the Kain–Fritsch and Grell schemes were not large.