On the use of Dvorak current intensity as a climate data record in the western North Pacific

Trends in tropical cyclone activity in the western North Pacific basin have been extensively studied over the past several years. Most of these studies have obtained varying and often opposite results. This is particularly extraordinary as most of these studies used one of two sources for the best track data in the basin. However, as is documented by the International Best Track Archive for Climate Stewardship (IBTrACS) best track dataset, several data sources are available in the western North Pacific. To that end, the IBTrACS dataset facilitates interagency comparisons and can help improve our understanding of the differences in intensity amongst the agencies. Since each agency has different operational procedures and employs different wind speed averaging periods, most intensity estimates in the best track record vary greatly between the agencies. Nevertheless, each agency used the Dvorak satellite-intensity estimation technique after 1985. This technique results in a current intensity (CI) estimate that is the fundamental measurement for comparison between agencies since the same technique is applied globally. As historical conversion factors are documented in the literature, it is possible to “back out” this conversion to re-derive CI, from which comparisons between the agencies can be achieved by working on the same plane - a technique that is referred to as working in “CI-space.” The poster presentation will introduce the new concept of working in CI-space and will demonstrate the utility of CI as a climate data record for the western North Pacific basin.