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					   SNOW COVER MONITORING OVER
       SOUTH AMERICA USING
      PASSIVE MICROWAVE AND
  VISIBLE/INFRARED OBSERVATIONS


   Peter Romanov, Dan Tarpley and Bruce Ramsay


Office of Research and Applications, NOAA/NESDIS, Camp Springs, MD
 Objectives

• Assess potentials for snow cover mapping over
  South America using satellite data
• Improve characterization of snow cover and
  provide accurate high-resolution data on snow areal
  extent and variations for use in meteorological and
  climate models
NOAA/NESDIS automated snow products
for South America
     DMSP/SSMI (microwave)
           - Daily
           - 30 km resolution, global
           - All weather
           - Available since 1987 (SMMR since 1978)

     GOES Imager (visible/mid-infrared/infrared)
           - Daily
           - 4 km resolution, South America
           - Cloud clear observations
           - Available since 2000

     NOAA-16 AVHRR (visible/mid-infrared/infrared)
           - Daily
           - 4 km resolution
           - Cloud clear observations
           - Under development, expected later this year
Issues addressed:

• Snow cover monitoring using a new snow-mapping
  system based on GOES Imager data (visible, mid-
  infrared, infrared)
• Comparison of snow products derived from satellite
  observations in the microwave (DMSP SSM/I) and in
  vis/mir/ir (GOES Imager)
• Correspondence between satellite-derived snow cover
  and surface observations of snow and precipitation
• Long-term variability of snow cover in South America
  from available time series of satellite observations in
  the microwave
Snow cover monitoring using GOES Imager data




  Winter 2000   Summer 2001   Snow season duration
        Satellite vs surface observations of snow cover

                                                      Fractional snow cover, GOES Imager
                                                      Fractional snow cover, SSM/I

                                                      Event of snowfall or mixed snow/rainfall (surface obs)
                                                      Snow depth, cm (surface obs)


                                    1.0                                                                         30
                                                                                   46.51 S 71.01 W
            Fractional snow cover




                                    0.8




                                                                                                                     Snow depth, cm
                                                                                                                20
                                    0.6
SSM/I                                                                                                                                   Snow
                                    0.4
                                                                                                                10                       fall
                                    0.2
GOES
                                    0.0                                                                         0
                                                                                                                                        Snow
                                          May-2001   Jun-2001   Jul-2001    Aug-2001     Sep-2001    Oct-2001                           depth
                                              Snow fraction is estimated within 1x1 degree
Satellite                                     area centered at the location of the station
 snow                                                                                                                                   Surface
fraction                                                                                                                              observations
       Monthly frequency of snow cover
       GOES Imager vs DMSP SSM/I

       July, 2000              February 2001




GOES-8 Imager DMSP SSM/I   GOES-8 Imager DMSP SSM/I
                Snow cover over Patagonia (from SSM/I data)


                1.0


                0.8
Snow fraction




                0.6


                0.4


                0.2


                0.0
                      1986   1988   1990   1992   1994    1996   1998   2000   2002
                                                   Year

                                                                                      The area of reliable
                                                                                      SSM/I-based snow
                                                                                      retrievals
Conclusions

GOES Imager observations are promising for monitoring large-area variation
of snow cover in the mid-latitude portion of South America. However, they
cannot be used for monitoring tropical glaciers and ice fields because of
insufficient spatial resolution of the measurements and due to persistent
orographic cloud cover.

The NESDIS operational microwave snow product over South America has
several problems which mostly result from physical limitations of the
microwave method. These problems should be addressed when using SSM/I
snow retrievals in meteorological and climate applications.

Snowfalls typically produces a noticeable increase of the snow cover extent (or
fraction) identified form satellite observations. Therefore the results of satellite
snow cover monitoring can probably be used to improve the analysis of solid
precipitation.

				
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posted:3/14/2012
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