Coupled Air-Sea Observations of Tropical Cyclones in ITOP

The goal of the Impact of Typhoon on Ocean over the Pacific (ITOP) and Tropical Cyclone Structure 2010 (TCS10) is to better understand and predict TC formation and intensity change through a comprehensive observation of TC structure and its oceanic and atmospheric environment over a broad spatial and time scales. An objective cloud-cluster tracking method is used to identify the TC precursor clusters using hourly satellite IR images over the entire West-Central Pacific basin. By tracking all cloud clusters, we are able to objectively determine both developing and non-developing TCs, which have been a one of the most difficult problem in understanding of formation (genesis) of TCs in the past, especially the lack of objective method for determining non-developing TCs. Comparing with results from previous years (2003-2009), 2010 consists of more long-lived cloud clusters that do not develop into TCs, even though some apparent large-scale conditions such as warm SST and synoptic wave-like disturbances are abundant. Composite of the environmental conditions for developing vs. non-developing cases using the global analysis fields and in situ airborne dropsonde and AXBT data are used to quantify the mesoscale and large-scale “forcing” for TCs. The ITOP/TCS10 field experiments were designed to follow the developing TC throughout their lifecycle with extensive observations of pre-, during- and post-TC oceanic and atmospheric conditions. More than 800 GPS dropsondes and 1000 AXBTs/AXCTs as well as drifters and floats were deployed in TCs from August-October 2010, including Typhoon Fanapei and Supertyphoon Megi. Some preliminary analysis and implication for coupled TC prediction model development and verification will be discussed. Furthermore, a comparison of TC activities between the western Pacific and Altantic basins using the cloud-cluster tracking analysis will be presented.