SAC-D. SMOS 4th Science Workshop April 2003, Porto Presented by Jordi Font, Prepared by Gary Lagerloef

Transcription

1 (Ocean Surface Salinity Measurement) Understanding the ocean s response to the global freshwater cycle SMOS 4th Science Workshop April 2003, Porto Presented by Jordi Font, Prepared by Gary Lagerloef 1

2 United States Argentina Partnership 2

3 Project Team Goddard Space Flight Center Principal Investigator Deputy Project Manager Deputy Project Systems Engineer Observatory Manager Observatory SMA Radiometer Science Data Processing Segment Validation ESR Education - Bigelow Spacecraft Manager Spacecraft Bus Spacecraft SMA Observatory I&T Mission Operations Segment Additional Payloads Project Manager Project Scientist Project Systems Engineer Project SMA Instrument Manager Scatterometer Instrument I&T Data Archiving and Distribution Segment 3

4 Project Timeline (Approximate) > Risk Mitigation Study SRR Formulation Implementation ( 37 Months ) // // Operations ( 3-5 years ) // IOC Science Operations SELECTION July 2002 CONFIRMATION LAUNCH Fall 2008 (Tentative) END OF MISSION 4

5 NASA SCIENCE QUESTIONS: SAC-D How is the global water cycle changing? How do climate variations affect ocean circulation? Global Water Cycle Precipitation Evaporation Ice Freeze/Melt Land Runoff Ocean Circulation Surface Height Barrier Layers El Niño/La Niña Thermohaline Flow Water Flux Change Aquarius SAC-D Sea Surface Salinity (SSS) Impact Sea Water Density 86% of global evaporation 78% of global precipitation Changes in Ocean circulation impact climate SSS responds to changes in water fluxes and alters the surface density field that drives ocean currents. 5

6 Likely Precipitation Trend over the next Years as indicated by a the Ensemble Mean of 14 Climate Model 2xCO 2 Simulations Enhanced ITCZ, Monsoon and ENSO? Increasing Subtropical Atlantic SSS? Increasing Intermediate Subduction Cell? Allen and Ingram, Nature,

7 Salinity Science Objectives 3-5 Year Explorer/Pathfinder Missions Focus on the seasonal cycle and year-to-year variability. Discovery and Exploration: Salinity mapping of unmeasured regions and features unknown to science. Water Cycle: Salinity response to surface water fluxes. Ocean Circulation and Climate: Tropics Climate feedback processes, El Niño La Niña. Mid-Latitudes Subduction and mode water formation. High-Latitudes Deep water formation processes Baseline for future long-term measurements 7

8 Measurement Objectives - Resolve key ocean and climate phenomena at 100 km and larger spatial scales, monthly and longer time scales. 8

9 SSS Science Measurement Requirements Global coverage Mission life: 3 year baseline, 1 year minimum Resolution: 100 km baseline, 200 km minimum Monthly accuracy: 0.2 psu (rss) baseline, or minimum 0.2 psu in the tropics and 0.3 psu in high latitude. 9

10 Aquarius Science Investigations The dynamical impacts on the subsurface ocean. Coupled ice-ocean processes. Processes that keep the Atlantic saltier than other oceans. Tropical ocean climate models and El Niño prediction. SSS seasonal cycle and mixing. Surface salinity transport processes that redistribute E-P imbalances. Ocean state estimation and the freshwater budget. Chet Koblinsky GSFC Gary Lagerloef ESR Yi Chao JPL Simon Yueh JPL Sirpa Hakkinen GSFC Bill Large NCAR David LeVine GSFC Bill Wilson JPL Tim Liu JPL Susan Lozier Duke Mike McPhaden NOAA/PMEL Michele Rienecker GSFC Robert Molinari NOAA/AOML Richard Feely NOAA/PMEL Arnold Gordon Columbia Chris Ruf Michigan Detlef Stammer Scripps Frank Wentz Remote Sensing Systems Jordi Font Barcelona Jim Gower IOS, Canada Shiro Imawaki Japan Alberto Piola Buenos Aires Thierry Delcroix IRD, France Jerry Miler US Navy 10

11 Salinity is Observed by Measuring Emissivity at L-Band (1.413 GHz) Tant (K) L-Ba nd Ve rtic a l psu 35 psu 40 psu K&S Model Passive Active L & S Band Sensor (Wilson and Yueh, JPL, October 2001) Water Temp (C) The Klien and Swift theory has been validated with controlled experiments over a wide range of T & S. New laboratory measurements of the sea water dielectric constant at GHz are being made. Recent field measurements to test models available from SMOS -WISE Campaign in the Mediterranean. 11

12 Tb <V+H> (K) SAC-D Geophysical Corrections Needed to Achieve the Required Scientific Accuracy Aquarius Will Carry a 1.2 GHz Radar Scatterometer to Correct for Surface Roughness Radar Backscatter * 100 Error Analysis (residual after correction applied) Surface roughness <5 K (0.15 K) SST ±0.14 K per 1º C (.07 K) Dry Air K (.07 K) Water vapor <0.01 K (.005 K) Cloud liquid water <0.1 K (.04 K) Rain cells <0.1 K (.02 K) Solar reflection <0.1 K (.005 K) Faraday rotation <5 K (.02 K) Galactic <2 K (6 K extreme) K (.02 K) Radiometer calibration stability (0.15 K) Radiometer NEDT per observation (.06 K) Total rss error (0.26 K) ~0.5 psu Spatial and Temporal Filtering will be Necessary to Reduce Error Objective: psu error 100km x monthly 200km x 10 days

13 Aquarius Real-Aperture 3-Beam Sampling Pattern Sun-Synchronous 6am/pm Orbit Aquarius will sample with 3 beams of km wide footprint diameters across the 300 km wide swath. The Aquarius Sampling Pattern Provides Global Coverage in 8 Days With the sun-synchronous 6am orbit, the beams will point into the night side to avoid sun glint. 13

14 SAC-D Approximate Orbit and Partial 1 day Swath Pattern 14

15 Post Launch Data Global and Regional Coverage Typical SSS Validation Data Distribution During Aquarius 8-day or SMOS 3-day Cycle Platform for salinity sensor Quantity Funded Y/N Sensor funding source Argo Buoys 300 Yes International commitments NE Pacific Drifters 50 Yes Aquarius (100 total) Subtropical Atlantic Drifters 50 Yes Aquarius (100 total) NOAA TAO Moorings 55 Pending NOAA Japan TRITON Moorings 13 Yes JAMSTEC (Japan) Ship thermosalinograph 32 Yes NOAA, IRD(France) 15

16 Validation The in situ surface validation measurements will make use of Operational Real-Time Data in partnership with NOAA and the ongoing international Global Ocean Observing System (GOOS) Research Ships Volunteer Merchant Ships Thermosalinograph data 16

17 Synergy between Aquarius SAC-D and SMOS Explorer/Pathfinder Missions Goddard Space Flight Center 17 SAC-D Soil Moisture Ocean Salinity SMOS

18 Synergy between Aquarius SAC-D and SMOS Orbits: 6am-6pm sun-synchronous Launch dates (current): 2007 SMOS 2008 Aquarius SAC-D Pre-launch Science: Joint science workshops, field campaigns, algorithm studies, joint co-investigator relationships, other ongoing activities Post-launch Science: Sensor inter-calibration, shared in situ validation resources, blended data products. Joint International Science Working Team - TBD 18

19 Scientific Synergy between Aquarius SAC-D and SMOS Aquarius SAC-D and SMOS together will provide direct measurements of the global water cycle changes over the land and ocean by measuring salinity and soil moisture. The Aquarius SAC-D radiometer, radar technology and salinity accuracy will provide a calibration reference for SMOS ocean measurements. Aquarius SAC-D will low resolution passive and active (Lband radar) land measurements to aid soil moisture retrieval science. The merged data from the two missions will provide better overall sampling and accuracy than either mission alone. 19