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AMSU/MHS Snowfall Rate Product

NESDIS Snowfall Rate (SFR) Product Training Session Huan Meng , Ralph Ferraro NOAA/NESDIS December 5, 2013. AMSU/MHS Snowfall Rate Product. Satellite retrieved liquid equivalent snowfall rate (SFR) over land Need snow to liquid ratio to convert to solid snow

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AMSU/MHS Snowfall Rate Product

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  1. NESDIS Snowfall Rate (SFR) ProductTraining SessionHuanMeng, Ralph FerraroNOAA/NESDISDecember 5, 2013

  2. AMSU/MHS Snowfall Rate Product • Satellite retrieved liquid equivalentsnowfall rate (SFR) over land • Need snow to liquid ratio to convert to solid snow • The ratio is dependent on the local climatology and environmental conditions such as surface air temperature and temperature profile • SFR uses data from microwave sensors: Advanced Microwave Sounding Unit-A (AMSU-A) and Microwave Humidity Sounder (MHS). The sensors are aboard fourpolar-orbiting NOAA POES and EUMETSAT Metop satellites • Each satellite orbits the earth 14 times a day. It takes 2-3 orbits to cover CONUS. • Each satellite passes a location up to twice per day in and below mid-latitudes, maybe more in higher latitudes. The two passes are about 12 hours apart. The four satellites provide up to eight SFR estimates, grouped into 4 morning overpasses and 4 afternoon overpasses, in a location in mid-latitudes per day. • SFR resolution is 16 km at satellite nadir and 26 km x 52 km at limb • Maximum liquid equivalent snowfall rate is 0.2 in/hr; minimum is 0.004 in/hr

  3. Product Applications • Identify snowstorm extent and the location of the maximum intensity within the storm • Provide quantitativesnowfall information to complementsnowfall observations or estimations from other sources (stations, radar, GOES imagery data etc.) • Fill observational gaps in mountains and remote regions where weather stations are sparse and radar blockage and overshooting are common • Locate snowstorms at higher latitudes where the quality of the subjective GOES IR and VIS imagery data deteriorates • Track storms and derive trending information (e.g. strengthening or weakening of the storm) by pairing with GOES IR/VIS/WV images to

  4. What to be Aware of • This is a liquid equivalent snowfall rate • There usually is a time lag between the retrieved SFR and the best correlated ground observation, due to the slow terminal velocity of snow particles • Satellite microwave signal can penetrate cloud, so SFR represents snowfall throughout the precipitation layer • The current product is limited to regions where the surface air temperature is about 22°F and above • Extension to colder climate is currently under development • Not applicable to lake effect snow • The resolution of the product is too coarse to detect the narrow snow band of lake effect snow • Misses very light snowfall due to a minimum SFR limit • Polar-orbiting satellite product with latency of 30 min – 3 hrs

  5. Use Case 1 – Tracking Snowstorm Hard to determine snowing clouds from GOES Difficult to tell rain from snow in radar SFR Product at 17:05Z Snow max later rotated and moved north Snow edge and max intensity easy to infer GOES IR image at 17:00Z Radar at 17:06Z • How do I use the SFR Product? • SFR adds additional information to radar and GOES data • SFR makes it easy to identify edge of snowfall and area of maximum intensity • The movement and strength of a feature identified in SFR can be tracked using radar or GOES imagery between SFR overpasses • In addition, radar and GOES images can also be used to infer storm trending information SFR Product at 19:40Z

  6. Use Cases 2 & 3 – Filling Radar Gaps Higher elevation rain does not appear on SFR product SFR retrieval over an area in radar gap during a snow event in Newfoundland, Canada on November 29, 2012 Mono Lake x Lee Vining x x x June Lake Mammoth Lakes NEXRAD Composite Reflectivity & SFR NEXRAD Composite Reflectivity Maximum snowfall rate zone (MSRZ) The MSRZ moved further north MSRZ moved further north 19:40Z

  7. Product Summary • SFR is liquid equivalent snowfall rate • SFR uses observations from microwave sensors aboard polar orbiting satellites • Eight SFR estimates a day grouped into 4 morning and 4 afternoon overpasses • Most important applications: • Identify snowstorm extent and area with the most intense snowfall • Fill gaps in radar coverage and ground observations

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