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Passive Microwave Data at NCDC John J. Bates and Hilawe Semunegus NOAA’s National Climatic Data Center Asheville, NC AMSR-E Group Meeting June 28, 2011 Asheville, NC NOAA’s National Climatic Data Center
Outline • Passive microwave data archive at NCDC • Recent work to address SSMIS data quality issues using the Unified Preprocessor (UPP) software developed by NRL and the UK Met Office (NWP SAF) • Collaborators include Steve Swadley (NRL), Bill Bell (NWP SAF), Joe Turk (NASA JPL), Wesley Berg/Mathew Sapiano (Kummerow’s group at CSU) • Modification of UPP for Climate and Precipitation (CP) applications • Latest on the GCOM-W1 (AMSR2) instrument
NCDC Passive Microwave Data Archive and CDR development • DMSP SSM/T1 and SSM/T2 (POR: 1992-2005); Fundamental Climate Data Record (FCDR) in progress; Luo et al • DMSP SSM/I and SSMIS (POR: 1987-present); FCDR in progress; Kummerow et al. • AMSU-A and AMSU-B (POR: 1998-present); FCDR in progress; Ferraro et al. and John et al. • Several products based on these passive microwave datasets are archived at NCDC (e.g. MIRS, SSMI-SSMIS Hydrological Products). • GCOM-W1 (AMSR2); pre-launch planning stage (will be archived at NCDC)
Corrections Needed for SSMIS TDR Data • Scan Non-Uniformity Correction (all satellites) • Channel dependent multiplicative coefficient applied to each beam position from static scan non-uniformity files • Radiometer Gain Correction (F16 all year, F17 at high solar elevation angles in spring and summer) • Corrects for solar intrusions into warm load resulting in short duration positive Gain anomalies • Radiometer sees warm load tines “warmer” than recorded warm load temperature, resulting in a brightness temperature depression of ~ 0.5-1.5 K • Short lived Gain anomalies are filtered using the Northrup Grumann (NG) developed algorithm and available in the operationally produced gain files (one file for each TDR file) • Reflector Emission and Thermistor Location (F16 and F17, but applied for all) • Requires knowledge of reflector temperature Trefl and frequency-dependent emissivity ε • F-16 required an emprically developed Trefl using the reflector rim temperature • F-17 - F-20 have the thermistor moved to the back of the graphite reflector shell
UPP to UPP-Climate & Precipitation (CP) Applications Native: UPP (original NWP application): Averages all channels to LAS resolution (N/3 X 60), then calls routines to apply corrections Scans= approx. 3200 IMA (6 chans) ENV (5) LAS (8) 180 90 60 Scan non-uniformity correction Apply scan uniformity to IMA, ENV, LAS For UPP-CP: Apply corrections at native resolution and output data in unique binary format Gain anomaly correction Apply gain ratio to each channel set Reflector emission correction ProcessLASTDR_v2 Remap to LAS and apply TB corrections
Reflector Emission (1-2 K) and Thermistor Location Reflector Emission (~1-2K) • 1) SSMIS Cal/Val team determined reflector’s layered SiOx/AL VDA coating process resulted in emissive F16 and F17 reflectors. F18 fixed this problem: • Thick white coating used over graphite epoxy reflector • Reflector surface slightly roughened using abrasive material IMA 50-60 GHz UAS 60 +/- GHz LAS 50-60 GHz IMA 91-183 GHz ENV 19-37 GHz 2) Depending upon the time of year and orbital parameters the sensor enters Earth shadow and/or solar Array shadowing and the reflector cools by ≈ 80K, then rapidly warms to near 300K upon exiting shadow • F16: thermistor located on reflector rim, Trefl based on “lagged-derivative” approach; over hundred scans discarded per orbit • F17-F20: thermistor moved to back to reflector, gives better estimate of Trefl; only few scans discarded per orbit. • F18 does not have this issue
F-16 Reflector Temperature Issue T_rflct does not keep up with the actual reflector face temperature immediately after emerging from shadow
F-16 SSMIS Solar Intrusions (-0.5 to -1K) June 1, 2010: Rev 34148 (one orbit) Solar intrusions into the warm load occur 2-4 times per orbit, as evidenced by the Gain ratio or Gain_Original/ Gain_Filtered Y-axis: 1-(Gain_Original/ Gain_Filtered), Range of 0.005 to +0.005 X-axis: scanline, range 1-3200
Solar Intrusion Corrections • Northrup Grumman (NG) developed a solar intrusion correction for operational use that is applied in UPP (and will be applied in UPP-CP) • NG produces ancillary “gain files” which are required to apply correction • Do not know how these are produced • Currently evaluating suitability of this correction technique for climate but may be sufficient for ICDR • At this point we have more questions than answers... Example from Gain file red line: actual gain; blue line: filtered gain
Antenna Pattern Corrections (APC) • Publicly available SSMIS SDR data (from FNMOC; archived at NCDC) uses spillover and cross-polarization coefficients (APC components) • FNMOC APC derived based on surface-dependent inter-calibration to SSM/I • Not applicable for climate and precipitation applications • UPP-CP needs new APC coefficients, currently being developed by CSU (Kummerow’s group) • US Navy (FNMOC) plans to run an operational version after UPP-CP group resolves APC coefficient issues.
SSM/I and SSMIS Fundamental Climate Data Record • Colorado State University (CSU) producing an FCDR of SSM/I and SSMIS under NCDC CDR program • FCDR will include QC, improved geolocation, intercalibratrion; code is open source and freely available • All three of the previously listed corrections are implemented for CSU SSMIS • Now beginning testing to understand effect on calibration of brightness temperatures produced • Will apply 4 independent inter-calibration techniques (already applied to SSM/I) to check for agreement between SSMIS and SSM/I • In addition, CSU will apply new scan non-uniformity corrections and will supply inter-calibration numbers
GCOM-W1 (AMSR-2) Update • Expected instrument launch is Feb. 2012 (delayed by 3 months because of Japanese earthquake) • NCDC/CLASS will receive JAXA GCOM-W1 (AMSR-2) RDRs in HDF5 format via the IDPS (very similar to NPP RDR functionality in terms of packaging and delivery) • Expected volume is ~975 MB/day of GCOM-W1 AMSR-2 RDRs, which represent 15 orbits per day; ~65 MB per file. • AMSR-2 RDR will have science, telemetry, housekeeping and diagnostic data types • AMSR-2 RDRs will be restricted to users specified by GCOM-W1 Working Group (POC: Jennifer Clapp at NESDIS IIA). • Continuity of existing observations (Level 2 and Level 3) for sea surface temperatures, sea ice and snow cover extent, vegetation index, soil moisture, ocean surface wind speed, water vapor, precipitation rates and ocean color. Products slated for 2013.