1. NASA, CGMS-43, May 2015 Coordination Group for Meteorological Satellites - CGMS Use of Satellite Observations in NASA Reanalyses: MERRA-2 and Future Plans Presented to CGMS-43 Working Group II session, Agenda Item WGII/10 Presented By: Jack Kaye, NASA Headquarters Will McCarty, NASA Goddard Space Flight Center David Considine, Tsengdar Lee, NASA Headquarters Cynthia Randles, Goddard Earth Science Technology & Research Lawrence Coy, Krzysztof Wargan, Science Systems and Applications, Inc. Mike Bosilovich, Ron Gelaro, NASA Goddard Space Flight Center

2. NASA, CGMS-43, May 2015 Coordination Group for Meteorological Satellites - CGMS MERRA-2 Overview MERRA-2 is a NASA atmospheric reanalysis for the modern satellite era (1979-onward) MERRA-2 is a follow-on to the original MERRA project ‐Though still in production, MERRA is on the verge of running out of core radiance observations; the latest satellite used is NOAA-18 The new system incorporates observations launched since NOAA-18, including NOAA- 19, SNPP, Metop-A, Metop-B Beyond modern operational sounder radiance observations, MERRA-2 has been expanded to use new observations including MODIS, AVHRR, GPS Radio Occultation, OMI, and MLS Additional advancements to MERRA-2 include: An in-line aerosol model and analysis over the entire period Improved water vapor assimilation resulting in a balance between precipitation and evaporation Land surface forcing by observed precipitation Ultimately, MERRA-2 is seen as the base for future reanalysis efforts coupling the atmosphere, ocean, and land models and data assimilation systems.

3. NASA, CGMS-43, May 2015 Coordination Group for Meteorological Satellites - CGMS Radiance Data Usage in MERRA-2 MERRA-2 assimilates radiance observations from microwave and infrared sounders and imagers in sun- and geo- synchronous orbits A full timeline of radiances used is available in the working paper Recalibrated MSU observations were used for NOAA-10 and later satellites (right of the red line) Recalibrated Observations Microwave Sounding Unit Channel 3 Before the introduction of recalibrated radiances, inter-satellite inconsistencies for MSU channel 3 are seen in monthly mean brightness temperature (top). The bias correction (bottom) adjusts those observations so the residuals between the observations and the model forecasts (O-F, middle) are consistent across various platforms

4. NASA, CGMS-43, May 2015 Coordination Group for Meteorological Satellites - CGMS Ozone Data Usage in MERRA-2 Assimilated Data: 1980 – 2004: SBUV instruments on NASA & NOAA platforms 2004 – onward: OMI and MLS on NASA Aura MERRA-2 exhibits a bias of ~1 Dobson unit (~0.3% of global ozone) with respect to SBUV, but zero bias with respect to NASA OMI The Aura suite provides better orbital coverage and 10 times more observations SBUV OMI Data coverage v v Globally Averaged Total Ozone Difference (MERRA-2 minus Observation)

5. NASA, CGMS-43, May 2015 Coordination Group for Meteorological Satellites - CGMS Aerosol Data Usage in MERRA-2 MERRA-2 produces three-dimensional fields of dust, sea salt, sulfate, black carbon, and organic carbon over the entire period Realistic emissions and remotely sensed observations are incorporated via the Goddard Chemistry, Aerosol, Radiation and Transport (GOCART) and an in-line aerosol analysis The example above shows consistency with a previous, offline aerosol reanalysis (MERRAero) and also shows that the system was able to capture the major volcanic eruptions of El Chichón and Pinatubo Globally Averaged Aerosol Optical Depth (AOD) El Chichón Pinatubo AVHRR NASA EOS + AERONET Assimilated Data: 1979 – 2001: AVHRR AOD 2002 – onward: NASA EOS (Aqua & TERRA MODIS, TERRA MISR) + AERONET AOD