Quantifying the Impact of a Potential Gap in Afternoon Orbit Satellite Radiances on the North American Mesoscale (NAM) Forecast System

Both the Government Accountability Office and National Oceanographic and Atmospheric Administration acknowledge that there is a substantial risk of a gap in polar satellite data in the afternoon orbit, between the time that the current polar satellite is expected to reach the end of its life and the time when the next satellite is expected to be in orbit and operational. A satellite data gap could result in less accurate and timely weather forecasts and warnings of extreme events, such as hurricanes, storm surges and floods however the magnitude of a possible degradation has not been examined extensively. The NOAA Environmental Modeling Center performed an observing system experiment that replicates possible conditions expected with the loss of Joint Polar Orbit Satellite System (JPSS) radiances that would normally be ingested in the North American Mesoscale Data Assimilation System (NDAS) utilized in a developmental version of the NAM during a 60 day period preceding the 2012 development and landfall of Hurricane Sandy. Surface, upper air, and precipitation verification results will be presented that compare NAM simulations in which: all radiances are assimilated, afternoon orbit radiances are withheld, and a final experiment in which all satellite radiances are withheld. Furthermore, diagnostic output fields derived from forecasts are compared and contrasted for the two weeks leading up to US East Coast landfall of Hurricane Sandy for each experiment.