Characteristics of Convective Cloud Systems Over Costa Rica, Darwin and Guam for CRYSTAL

Three possible sites have been chosen for the next phase IOP of CRYSTAL. In order to facilitate the site selection, convective life cycle statistics have been derived for each location. Frequent isolated convective systems would be ideal to monitor the transition of convective anvils into upper tropospheric cirrus. Full-scale convection is difficult to monitor with aircraft given the turbulence and its effect on landing. Conversely, long periods with little convective activity would limit the effectiveness of the field campaign. For this study, the GOES-8 4km IR hourly images over Costa Rica during July of 2002, and GMS-5 5km IR hourly images for Guam during July of 2002 and Darwin during January of 2002 were used. For each site large and small domains were determined to depict the conditions of the ground sites and aircraft flight ranges and are further subdivided into land and ocean regions. IR thresholds were used to estimate convective and anvil areal coverage. The areal coverages were also used to determine the diurnal cycle amplitude and Fourier analysis to determine the diurnal cycle consistency. For each site, isolated discernable anvils were visually inspected in order to record the convective diameter and anvil length for each IR image from the onset of convection to dissipation. Convective and anvil duration frequencies were computed and compared with previous CRYSTAL-FACE results. Also comparisons of convective diameters and anvil lengths will be presented. Results indicate that Darwin and Guam have the greatest areal coverage of convective systems and the Florida domain has the smallest. Darwin has the greatest diurnal convective cycle and matches that of Florida. The convective and anvil durations for all three sites are similar, but limited by the hourly and spatial resolution of the IR images, since the tracking of anvil dissipation is difficult. In any case anvils persist longer than those of CRYSTAL-FACE and cover greater areas.