Toward a Global Climatology of Tropical Cloud Clusters

A global climatology of tropical cloud clusters is being developed. Cloud clusters are persistent, organized areas of deep convection that sometimes develop into tropical cyclones. We use merged datasets of infrared brightness temperature (T(b)) to identify convective areas that are independent, circularly shaped, sizeable, and that persist for at least 24 hours. The algorithm is completely automated and can be applied to create near real-time cloud cluster data.

Current output from the algorithm include cloud cluster size and statistical descriptions of T(b), including mean, variance, and percentile ranks of the coldest cloud tops. Before completion of the initial phase of the project, we intend to include other variables that roughly describe the oceanic and atmospheric environment of the cloud cluster, such as: sea surface temperature, vertical wind shear, and columnar moisture. Because of the large potential for the use of the data in tropical cyclogenesis studies, the ultimate fate of the clusters (developing or not) and other specific genesis parameters (e.g. daily genesis potential) will also be included.

A 30-year (1980-2009) time series of tropical cloud clusters will be completed early next year and made available in both global and basin datasets soon thereafter. In addition to the tropical cyclogenesis research applications, we anticipate that the data will be useful in climatology studies as well as operational identification and tracking of potential tropical cyclones.