Tuesday, 15 January 2002: 2:30 PM
Threshold sea surface temperature for initiation of convection
There has been controversy regarding the existence of a threshold sea surface temperature (SST) value for initiation of convection. We attempt to approach this topic from a different perspective. We add SST anomalies to subregions (with climatological SST elsewhere) and define the convective threshold as follows: for climatologically non-precipitating regions, the value to which SST must be raised locally to become convecting; and for climatologically precipitating regions, the value to which SST must be lowered to cease convection. This definition works adequately despite the caveat that the threshold SST may depend on the size of the subregions. We note that this threshold is not absolute since it is defined related to current climatology. The threshold relative to an altered climate is also presented. Spatial variations of threshold SST can occur from basin to basin. This "map" of threshold SST for convective initiation provides a useful starting point for the discussion of the importance of absolute SST value versus SST anomalies in setting convection.