Extended Abstract (1.2M)J16.1
Preliminary Assessment of ASCAT Ocean Surface Vector Wind (OSVW) Retrievals at NOAA Ocean Prediction Center
Khalil. A. Ahmad, NOAA/NESDIS/StAR - Perot Systems Government Services, Camp Springs, MD; and J. M. Sienkiewicz, Z. Jelenak, and P. S. Chang
The NOAA Ocean Prediction Center is responsible for issuing marine forecasts and wind warnings over the North Atlantic and North Pacific extratropical high seas, including the offshore waters of the continental United States.
In providing accurate marine warnings and forecasts, one of the most significant challenges facing an OPC forecaster is the scarcity of data over the vast ocean regions within the OPC's area of responsibility (AOR). The high quality, remotely sensed ocean surface vector wind (OSVW) data greatly help fill in the immense data void between the sparse conventional surface observations within the OPC's AOR. The SeaWinds scatterometer onboard QuikSCAT satellite has been providing the OPC forecasters, and the operational weather community with near real time (NRT) OSVW data since the spring of 2000. Over the eight years of availability, QuikSCAT winds have become an integral data source in OPC daily operations. An additional source of OSVW data have become available in the large and mostly void regions within the OPC's AOR after the recent launch of the Advanced Scatterometer (ASCAT) in October 2006 by EUMETSAT. The OSVW retirevals from ASCAT are produced at two horizontal resolutions of 50 and 25 km by NOAA NESDIS, and have been available to OPC forecasters since June 2007 and October 2007, respectively. The ASCAT wind data is being routinely viewed by OPC forecasters on a daily basis during the course of their operational shifts. Compared to QuikSCAT, the ASCAT instrument has different capabilities, due to ASCAT's coarser resolution, narrower swath, and reduced sensitivity to rain and high wind speeds.
In this paper, we provide an overview of the ASCAT measurement characteristics, and the instrument spatial / temporal coverage. Further, we present an up to date assessment of the ASCAT retrievals in support of OPC's analysis and warning operations, where we focus on the utility of the ASCAT OSVW data in detecting Hurricane Force (HF) extratropical cyclones, and estimating the wind warning category. In this activity, we utilize the surface analysis charts prepared by the OPC forecasters to locate and track all HF extratropical cyclones observed over both the North Atlantic and North Pacific oceans during the 2007/2008 winter season. Hundreds of passes from ASCAT and QuikSCAT are examined, and wind retrievals are compared to the output of two Numerical Weather Prediction models, and where available, to conventional buoy / ship observations. Results indicate that ASCAT can reliably retrieve low to moderate surface wind speeds in all weather conditions. This performance represents an improvement over QuikSCAT, which suffers from an artificially rain inflated retrievals in areas of rain. However, for higher wind speeds, ASCAT retrievals are found to have a low wind speed bias, which degrades ASCAT capability in detecting extratropical cyclones with Hurricane Force conditions
Joint Session 16, Operational Products and the Transition from Research to Operations
Wednesday, 14 January 2009, 4:00 PM-5:30 PM, Room 224AB
Next paper