92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Tuesday, 24 January 2012: 2:30 PM
Climatology of Tropical Cloud Clusters
Room 355 (New Orleans Convention Center )
Christopher C. Hennon, Univ. of North Carolina Asheville, Asheville, NC; and P. P. Papin and C. M. Zarzar

Poster PDF (697.0 kB)

Tropical cloud clusters (TCCs) are mesoscale convective systems that develop and persist over low latitude ocean basins. They are generally circular in shape, containing distinct convective updrafts with extensive cirrus canopies. TCCs can persist for several days and may develop into tropical cyclones if conditions are favorable. They are also important players in the tropical energy balance, releasing large amounts of latent heat and transporting moisture into the mid-upper troposphere. Their large size significantly affects the local and regional radiation balance.

There have been many efforts made to observe TCCs, including intensive observation periods of several field experiments (e.g. Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment (GATE), Tropical Cloud Systems Processes (TCSP)) and many smaller studies that developed their own TCC dataset. Though all of these efforts yielded valuable information on TCCs, the data were limited to a small spatial domain or short time period.

Recently, a 28-year dataset of global TCCs (1982-2009) was created by means of an automated TCC tracking algorithm, applied to homogenous geostationary satellite data. This work is the first analysis of these data, focusing on climatology and annual variability. TCCs form in all of the world's ocean basins, most frequently in the low-level convergent regions of the Intertropical Convergence Zone (ITCZ), monsoonal troughs, and the South Pacific Convergence Zone (SPCZ). TCCs typically last for about 2-3 days before dissipating or developing into tropical cyclones. Globally, approximately 7% of TCCs develop into tropical cyclones. The western Pacific is the most productive ocean basin for development – about 12% of all TCCs undergo tropical cyclogenesis there. Although the annual number of global TCCs has been remarkably consistent decadal time scales, there is a large amount of regional interannual variability. The data suggest this variability is primarily driven by the oceanic and atmospheric response to annual to decadal oscillations such as the El-Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO).

Supplementary URL: http://tinyurl.com/cloudcluster