SEASONAL AND INTERANNUAL VARIABILITY OF TROPICAL CYCLOGENESIS - DIAGNOSTICS FROM LARGE-SCALE FIELDS

Gray's seasonal genesis parameter (SGP) is reassessed as a diagnostic quantity for both climatological and single-season tropical cyclogenes is. The SGP applied to global analyses from recent years is able to lo cate the regions of genesis activity during 1967-86. The SGP based on the climatology of a simulation by the CSIRO9 atmospheric model using prescribed ocean temperatures for 1979-88 has similar skill. The SGP a pplied to single-season means is then assessed as a diagnostic for int erannual variation of cyclogenesis. Increased cyclo-genesis in the cen tral Pacific during the 1982/83 El Nino coincides with increased SGP. CSIRO9 simulated similar variations in the SGP. Moderate correlations are found between the time series of the observed and inferred simulat ed cyclogenesis numbers in the central Pacific, eastern North Pacific, and North Atlantic regions during 1979-88. However, elsewhere the cor relations were poor.