Published: 2:20 PM GMT on February 04, 2013
In November 2009, one of the greatest success stories in the history of satellite meteorology came to an end when the venerable QuikSCAT satellite failed. Launched in 1999, the QuikSCAT satellite became one of the most useful and controversial meteorological satellites ever to orbit the Earth. It carried a scatterometer--a radar instrument that can measure near-surface wind speed and direction over the ocean. Forecasters world-wide came to rely on QuikSCAT wind data to issue timely warnings and make accurate forecasts of tropical and extratropical storms, wave heights, sea ice, aviation weather, iceberg movement, coral bleaching events, and El Niño. Originally expected to last just 2 - 3 years, QuikSCAT made it past ten, a testament to the skill of the engineers that designed the satellite. Last week, though, NASA announced that a new QuikSCAT-like instrument called ISS-RapidScat will be launched in 2014 on a SpaceX Dragon cargo spacecraft, and installed on the International Space Station (ISS.) In a clever reuse of hardware originally built to test parts of NASA's QuikScat satellite, the cost of the new instrument will be much lower than any previous scatterometer launched into orbit.
Figure 1. Artist's rendering of NASA's ISS-RapidScat instrument (inset), which will launch to the International Space Station in 2014 to measure ocean surface wind speed and direction and help improve weather forecasts, including hurricane monitoring. It will be installed on the end of the station's Columbus laboratory. Image credit: NASA/JPL-Caltech/JSC
Alternatives to QuikSCAT
Three valuable alternatives to QuikSCAT are available, but none are as good as QuikSCAT was. There's the European ASCAT satellite, launched in 2007. Like QuikSCAT, ASCAT can measure global wind speed and direction twice per day. However, ASCAT covers only 60% of the area covered by QuikSCAT, which saw a swath of ocean 1800 km wide. ASCAT sees two parallel swaths 550 km wide, separated by a 720 km gap. I find it frustrating to use ASCAT to monitor tropical storms, since the passes miss the center of circulation of a storm of interest more than half the time. On the plus side, ASCAT has the advantage that the data is not adversely affected by rain, unlike QuikSCAT. The other main alternative is the OSCAT instrument, which was sent into orbit on September 23, 2009, on the ISRO (Indian Space Research Organization) Oceansat-2 satellite. Like QuikSCAT, the OSCAT has a swath 1800 km wide that covers 90% of Earth's area every 24 hours. The winds at the edge of the swath are not as accurate as the ones in the middle. Moderate and heavy rain cause bogus winds that can be up to 45 mph too high. The resolution is not as high--25 km, versus the 12.5 km resolution of QuikSCAT and ASCAT. The third option is the Windsat instrument aboard the Coriolis satellite (launched in 2003), which measures wind speed and wind direction using a different technique. Evaluation of these data at NHC and NOAA's Ocean Prediction Center (OPC) shown the winds to be unreliable in and around tropical storms.
Figure 2. Bill Proenza, directory of the National Hurricane Center from January 2007 - July 2007.
Former NHC director Bill Proenza fired
Former National Hurricane Center director Bill Proenza, 68, was fired from his position as director of the National Weather Service's Southern Region last week. The reason stated for his firing was his unauthorized transfer of $528,000 from a local forecasting account to pay for new radar equipment in 2012. The issue of moving money without authorization in 2012 also landed the director of NWS, Jack Hayes, in trouble, forcing him to resign.
Proenza laudably made a big push in 2007 for a new QuikSCAT satellite, but unfortunately made claims about the usefulness of QuikSCAT for improving hurricane track forecasts that were not supported by scientific research, an error that may have ultimately led to his downfall as NHC director. Proenza lasted only six months as director of NHC, from January - July 2007. While there is evidence that scatterometer data may improve hurricane track forecasts of some computer models, NHC uses many models to make hurricane track forecasts, and some of these models are not helped by scatterometer data. Scatterometer data is extremely valuable for many other aspects of hurricane forecasting, providing early detection of surface circulations in developing tropical depressions, and helping define gale (34 kts) and storm-force (50 kts) wind radii. The information on wind radii from scatterometers is especially important for tropical storms and hurricanes outside the range of aircraft reconnaissance flights conducted in the Atlantic and Eastern Pacific basins, and for the regions where there are no reconnaissance flights (Central Pacific, Western Pacific, and Indian Ocean). Accurate wind radii are critical to the National Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), and Guam Weather Forecast Office (WFO) watch and warning process, since they affect the size of tropical storm and hurricane watch and warning areas. Between 2003 and 2006, QuikSCAT data were used at NHC 17% of the time to determine the wind radii, 21% of the time for center fixing, and 62% of the time for storm intensity estimates.
2007 NOAA QuikSCAT user impact study:
I'll have a new post on Wednesday.