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Measuring High- L atitude Precipitation from Space

Measuring High- L atitude Precipitation from Space. Ralf Bennartz SSEC University of Wisconsin – Madison EES – Vanderbilt University. Outline. What can we do now? Connecting to the surface Greenland mass ba lance Validation Clouds and the surface energy balance Way forward.

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Measuring High- L atitude Precipitation from Space

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  1. Measuring High-Latitude Precipitation from Space Ralf Bennartz SSECUniversity of Wisconsin – Madison EES – Vanderbilt University

  2. Outline • What can we do now? • Connecting to the surface • Greenland mass balance • Validation • Clouds and the surface energy balance • Way forward

  3. Contributions • IWSSM-4 participants, in particular: • Tristan L’Ecuyer • Mark Kulie • Gail Skofronick-Jackson • Karen Boening • Anne Walker • Deb Vane

  4. IWSSM-4Fourth International Workshop on Space-based Snowfall Measurement • Held March 2013, Mammoth • 50 participants • Reports back to IPWG, CGMS, WMO • Detailed recommendations from four working groups: • Applications & Validation • Radiative Properties • Global & Regional Detection/Estimation • Missions & Concepts Ralf Bennartz, University of Wisconsin Robin Hogan, University of Reading Paul Joe, Environment Canada Gail Skofronick Jackson, NASA GSFC Graeme Stephens, JPL Deb Vane, JPL Jeff Dozier, UCSB

  5. Phase C. Kidd

  6. Type NEXRAD 1638Z Terra MODIS 1635Z

  7. Observing Snow with CloudSat Strengths of CloudSat: • Active sensor • Excellent sensitivity • Near-global coverage • Coincident measurements from other A-Train sensors Challenges: • Complex relationship between reflectivity and snowfall rate/IWC • Rain/snow discrimination • Sampling • Ground Clutter T. L’Ecuyer

  8. GPM - Courtesy of NASA GSFC Global Precipitation Measurement (GPM) • Joint NASA/JAXA mission • 2013: As soon as NASA find a launch vehicle… • Active: Dual-frequency Precipitation Radar (DPR) 12/17 dBZ MDS • Passive: Multi-frequency GPM Microwave Imager (GMI): 13 channels (10-183 GHz)

  9. Global Precipitation Measurement (GPM) • GPM-DPR • “It is estimated that due to its higher detectability threshold, only about 7%/1% of the near-surface radar reflectivity values and about 17%/4% of the total accumulation associated with global dry snowfall would be detected by a DPR-like instrument” (Kulie & Bennartz 2009, from global CloudSat observations)

  10. EarthCARE FOUR INSTRUMENTS: DOPPLER CLOUD RADAR HIGH SPECTRAL RESOLUTION LIDAR MULTI SPECTRAL IMAGER BROAD BAND RADIOMETER A. Illingworth Earth Explorer User Consultation Meeting 19 and 20 April 2004 EarthCARE 10

  11. Greenland Ice Sheet: Surface Mass Balance M. van den Broeke et al. 2009

  12. CloudSat data density • Even nadir-only sensors (CloudSat) provide decent coverage at higher latitudes • About 7000 obs per year per 1x2 deg box at 70 N.

  13. CloudSat: 2006 – 2010 Mean

  14. Greenland Ice Sheet: Surface Mass Balance • Cloudsat derived annual mean precipitation accumulation GIS 6/2006: • 650 Gt/yr

  15. GPCC: 2006 – 2010

  16. GPCC: 2006 – 2010

  17. Snowflakes Vermont – Bentley (ca. 1902) Summit Observatory – Greenland Shupe et al. (2012)

  18. Modeling Non-spherical Particles • In the last 5 years significant progress has been made in modeling non-spherical ice optical properties • What did we learn? • How can we constrain them?

  19. Uncertainty due to habit Hiley, Kulie, Bennartz (JAMC, 2011)

  20. Comparison to Canadian Surface Observations

  21. Ice Mass Increase and Antarctic Precipitation • CloudSat observes snowfall • Accumulated snow from CloudSat agrees well with GRACE’s observed mass • Sublimation plays minor role CloudSat This slide from Boening et al.

  22. Clouds and surface melting ICECAPS observations and models show that clouds were “just right” for enhanced ice surface melt in July 2012. Thin liquid water clouds trap infrared radiation while still permitting enough solar radiation to lead to maximum surface heating.

  23. Conclusions • Polar precipitation is a major gap with current satellite missions. Given the changes that are being observed in the Arctic due to climate change, a future satellite mission must focus on the capability to address polar precipitation and clouds synergistically in order to address climate and water cycle science/prediction priorities. • There is much to gained by the precipitation and snow on the ground communities working together to outline priorities for future missions and address retrieval issues. • If we want to observe climate signals, we need to have long-term records. Need for stable, well-calibrated long-term satellite datasets.

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