Convective scheme and resolution impacts on seasonal precipitation forecasts

Abstract

An investigation is carried out to assess the role of different convective schemes and resolutions in seasonal quantitative forecasts of precipitation. The model performances are evaluated by changing convective schemes and the resolution impacts are examined by increasing the model horizontal resolution from T63 to T170 and finally T255. The predicted rainfall amounts are compared against the TRMM satellite estimate. Every forecast captures prominent rainfall features reasonably well. However, there are pros and cons in each of the forecasts. Predicted seasonal rainfall patterns and intensities from changing convective schemes exhibit larger variability and higher impact on predictability than those from increasing resolution. The impact of higher resolution with any currently implemented cumulus parameterization turns out to be smaller in seasonal precipitation forecasts than in short- to medium-range forecasts. © 2003 by the American Geophysical Union.