A Reanalysis of Australian Region Tropical Cyclones in the Geostationary Satellite Era. Part 1: Intensity, Using the Objective Advanced Dvorak Technique (ADT)

The goals of this project are to enhance the historical record of tropical cyclones (TCs) in the Australian region (defined as the area south of the equator between longitudes 90E and 160E) during the geostationary satellite era, and demonstrate objective reanalysis methodologies that could be applied globally. The study was conceived and sponsored by the regional oil and gas industry, to better define future risks from TCs based on past records. The project makes use of infrared (IR) imagery from the Japanese “Himawari” series of geostationary satellites (the earlier Himawari satellites were also known as either GMS or MTSAT satellites). Himawari-1 (aka GMS-1) was launched in July 1977 and Himawari satellites have provided continuous coverage of the Australian Area of Responsibility (AOR) since that time. The Australian Bureau of Meteorology (ABoM) has an archive of Himawari data extending from 1981 to the present day, which is the period of this reanalysis. Passive microwave imagery (specifically 85-91GHz imagery) is also used to augment the IR data for the intensity estimates. Microwave imagery commenced in 1987 and the frequency and resolution of the available data increased over the subsequent two decades. The project uses a pre-processed archive of this data kindly provided by the US Naval Research Laboratory (NRL-MRY).

The primary metrics for the reanalysis consists of TC intensity and surface wind radii. The reanalysis tool used to estimate TC intensity (MSLP and Vmax) in this project is the Advanced Dvorak Technique (ADT) developed at the University of Wisconsin-CIMSS. The latest operational version of the ADT was run on the fullest resolution IR and PMW (when available) imagery for all TCs in the domain and during the period of the data. Estimates of Vmax are based on the ADT CI numbers, while the concurrent MSLP values are derived from the Vmax using the Courtney-Knaff wind>pressure relationship. Colleagues at the University of New South Wales employed the Directional Angle Variance (DAV) algorithm to obtain estimates of the wind structure radii (see partner poster). Reprocessed storm histories with all of these parameters were delivered to the ABoM for final quality control and synthesis. Some results and examples will be presented on the poster at the conference.