Implementation of Data ValidationAlgorithms in the Operational SFMR
Ivan PopStefanija; email@example.com
Alan Goldstein Aircraft Operations Centre NOAA
ProSensing Inc. 107 Sunderland Rd. Amherst, MA 01002 USA www.prosensing.com
Peter Black AOML Hurricane Research Division NOAA Miami, FL
In 2003, with funding from OFCM, the first operational Stepped Frequency Microwave Radiometer (SFMR) was delivered to NOAA/AOC by ProSensing Inc. The operational SFMR, deployed in a wing-pod, features a compact antenna and a pressure sealed cylinder to house the radiometer electronics. In 2005, the SFMR Processor was successfully integrated with the new radiometer unit. The SFMR Processor includes a single board computer, a small text message display and additional circuitry. The single board computer executes software developed by ProSensing to process raw brightness temperature data into estimates of wind speed and rain rate.
ProSensing has implemented data validity checking algorithms in three areas:
Validity flags indicating proper operation of each of the six receiver channels. Data from flagged channels are not used in the wind retrieval algorithm, which can still estimate the wind speed even if using less than six channels.
Validity flags based on auxiliary information provided by the main on-board computer. Auxiliary information contains aircraft attitude and geo-location. Data is flagged whenever the aircraft is not in a near-horizontal position since the wind speed inversion algorithm does not include models for off nadir incidence angles. Based on the latitude and longitude information, ProSensing also developed a data land mask with 1 by 1 km resolution. In instances when aircraft is flying over land, data reported to NHC is flagged invalid. In conjunction with AOC and NESDIS, we are currently developing code to add the sea surface temperature (SST) value, obtained from satellite measurements to every land-free pixel. This will improve the accuracy of the wind estimate as the wind retrieval algorithm will be able to use pre-flight updated SST values thought the entire Atlantic and Pacific Ocean.
A third data validity algorithm checks for deviation of the measured brightness temperature from the theoretical multi- parameter model versus frequency. We are analyzing data collected from previous hurricane seasons to develop the acceptable threshold levels for this error estimate, above which the data will be flagged invalid.
In 2005, US Congress appropriated funding to install pod-mounted SFMRs on all ten WC-130J Hurricane Hunter aircraft operated by the US Air Force Reserves 53rd Weather Reconnaissance Squadron. Two SFMRs were delivered to Lockheed Martin for test flights on the WC-130J in 2006. ProSensing is currently manufacturing an additional eleven SFMRs for the Air Force, with a total of four units scheduled for flights in the upcoming 2007 hurricane season. Increasing the number of operational SFMRs conducting routine hurricane surveillance will provide a large database for further development and analysis of surface wind data validity algorithms.