2013 Aquarius Science Cal/Val Workshop
2013 Aquarius Science Cal/Val WorkshopJanuary 29-30, 2013
In late January 2013, over 90 people participated in the online 3-day Aquarius Science Calibration/Validation (Cal/Val) workshop. Objectives included assessing the following: overall accuracy of the data; radiometer calibration performance; antenna pattern correction; performance of the radio frequency interference (RFI) mitigation algorithm; scatterometer performance; and accuracy of geophysical modeling algorithms. The workshop provided a thorough review of sensor calibration and science data processing status, leading to a successful dissemination of Aquarius V2.0 in winter 2013.
APC Cross Polarization Couplings 3rd Strokes ParameterMeissner, T. and Wentz, F. (29-Jan-13). Presentation gives an overview of the Aquarius antenna pattern correlation, the 3rd Stokes cross-polarization couplings, and 3rd Stokes calibration, including measured versus calculated during an S/C pitch maneuver.
Aquarius Antenna Temperature Calibration AssessmentPiepmeier, J. (29-Jan-13). Findings include: initial calibration bias verified within pre-launch error bars; on-going instrument behavior exhibits exponentially decaying gain error ~0.5% (which has settled) and non-monotonic fluctuations ~0.1K, both of which are corrected in V2 products; and model exhibits errors of similar magnitude.
Aquarius Antenna Temperature Calibration Working Group ReportPiepmeier, J. (29-Jan-13). Findings include: there is a long-term gain drift well modeled by exponential decay; there are shorter-term non-monotonic offset errors (i.e., "the wiggles"); there remain modeling errors in the antenna temperature global average comparison; cold-sky and SMOS matchups over land indicate the full dynamic range calibration has too high a slope; and noise diode and APC coefficients are only consistent for ocean scenes.
Aquarius Cold Sky CalibrationDinnat, E. (29-Jan-13). Findings include: ocean calibration results in a few K cold bias at the low end of Ta's; temporal variation of cold Sky bias supports correction for large exponential drift at beginning of the mission; temporal variation of cold Sky bias & offset/wiggles is inconclusive; and there is a 1K uncertainty due to antenna pattern model.
Aquarius Data Processing System and Level-2 Data ProductsPatt, F. (29-Jan-13). Status of ground processing system and overview of L2 data products.
Aquarius Data Release Version 2.0 Validation AnalysisLagerloef, G., and Kao, H. (29-Jan-13). Findings include: global RMS error, for the entire 16-months together is ~0.46 psu; monthly mean RMS error is ~0.33 psu; significant annual error cycle and geographic error patterns, especially in southern hemisphere; ascending-descending annual cycle bias is mostly in the descending side of the orbit; and three-month average gridded fields global RMS error is ~0.27 psu.
Aquarius L2 Algorithm: Geophysical Model FunctionsMeissner, T. and Wentz, F. (29-Jan-13). Findings include: excellent Aquarius wind speed retrievals with optimal channel configuration; in testbed, instantaneous wind speed measurement significantly improves roughness correction and correction for reflected galactic radiation; and significant performance improvement in salinity retrieval in testbed.
Aquarius L2 RSS Testbed Status & ValidationHilburn, K., Scott, J., Meissner, T. and Wentz, F. (30-Jan-13). Overview of the following: status and description of Aquarius data set, including major changes/differences from Aquarius Data Processing System V2.0; microwave radiometer (MWR), including resampling methodology, absorption correction, and rain flagging; validation of sea surface salinity HYCOM model; and validation through a triple collocation error model using Aquarius and buoys.
Aquarius Project, Spacecraft, Instrument and Data Processing StatusFeldman, G., Gales, J., Hong, L., Kuring, N., Owens, T., Patt, F., Scott, A., and Wilding, J. (29-Jan-13). Summary of status includes: the Aquarius Ground Segment are working well, and there are no significant issues; the end-to-end process of Aquarius data collection has worked as designed since launch; and housekeeping Telemetry web-based analysis pages are widely used and have provided comprehensive, critical and timely information to help identify many issues that have arisen since launch.
Aquarius Radiometric Calibration V1.3.9 DataFore, A. (30-Jan-13). Findings include: no significant ascending/descending bias observed over Amazon for the three beams of Aquarius; and bias over the ocean is not consistent with land estimates for HH polarization.
Aquarius Scatterometer Engineering Data and Sigma0 StabilityNeumann, G., Yueh, S., Fore, A., Freedman, A., Hayashi, A. and Tang, W. (30-Jan-13). Findings include: scatterometer calibration drift, if any is small; seasonal ascending/descending difference observed; geographical variation observed up to ~0.5 dB; and deviation from expected Sigma0 differs most at high latitudes and near the inter tropical convergence zone.
Aquarius Warm End CalibrationBindlish, R., Jackson, T., Zhao, T., Lagerloef, G., and Le Vine, D. (29-Jan-13). Findings include: Aquarius observations compare well with SMOS observations over oceans; Aquarius observations are very stable over Dome-C; and SMOS observations are lower than Aquarius observations for all channels over land.
Aquarius' Combined Active-Passive (CAP) SSS and Wind RetrievalYueh, S., Tang, W., Fore, A., Chaubell, J., Freedman, A., and Hayashi, A. (30-Jan-13). Findings are: (1) CAP is more accurate than the L2 product, (2) the Aquarius salinity product (CAP) is about 0.25 psu RMS for 28-day average, and (3) Aquarius CAP wind speed is highly accurate (0.7 m/s error) - slightly better than SSM/I.
Ascending-Descending Bias: Correlation With Galactic BackgroundHong, L. (30-Jan-13). Findings include: galactic background is an important factor of remaining geophysical model errors; simple linear adjustment is an applicable correction to the current model; and other error sources are to be analyzed in residual dTf biases.
Assessing Drift Correction over Antarctica and AmazonMisra, S. and Brown, S. (29-Jan-13). Findings include: exponential drift correction successfully removes observed drift over Antarctica; calibration wiggles are observed in Antarctic model differences and have the same magnitude as those observed over the ocean; and calibration wiggles are observed over warm rainforest regions in inter-channel differences and have a similar magnitude as those observed over the ocean.
Cold Sky Spillover MeasurementDinnat, E. (29-Jan-13). Findings include: at all beams/polarizations, the scale model predicts a better range of Ta than the GRASP 2012, but GRASP model is better in other respects.
Development of a Soil Moisture Product Using Aquarius/SAC-D ObservationsBindlish, R., Jackson, T., Zhao, T., Cosh, M., Holmes, T., and O'Neill, P. (30-Jan-13). Summary: Our approach to soil moisture retrieval uses the SCA with NCEP LST and MODIS NDVI climatology; we are working with ADPS to implement the Aquarius soil moisture algorithm; the use of the scatterometer to parameterize vegetation will be investigated; and the use of MWR to compute LST will be investigated.
Earth Sidelobe CorrectionMeissner, T. and Wentz, F. (29-Jan-13). Conclusions include: 1-km land mask makes big improvement on sidelobe correction for islands; there is significant difference between sidelobe correction using scale model versus using GRASP; sidelobe correction is better than doing nothing; and there is significant room for improvement with better knowledge of antenna sidelobes.
Separating Instrument for Model ErrorsLagerloef, G., Piepmeier, J., Hong, L. and Gales, J. (29-Jan-13). Presentation gives an overview of the basic matrix formulation, regression model, global ascending and descending data from Aquarius channel 1V, computed instrument and geophysical errors for all six channels.
Status of Radiometer RFI Detection and Mitigationde Matthaeis, P. (30-Jan-13). Overview of the following: long and short accumulations of radio frequency interference (RFI); RFI detection algorithm; issues with RFI (e.g., removal of "short accumulation 1" values, which are inconsistent with short accumulations 2 to 5); detection algorithm thresholds; and equalization of false alarm rate.
Summary of Antenna Pattern Correction (APC) Working GroupYueh, S., Brown, S., Meissner, T., Freedman, A., Piepmeier, J., LeVine, D., Dinnat, E., Wentz, F., and Lagerloef, G. (29-Jan-13). Report includes: new model patterns were generated using a higher fidelity model developed for SMAP (Soil Moisture Active Passive); new APC terms and correction maps generated from the 2012 model patterns; recommendation that the Aquarius project use the new patterns; and potential issue that new patterns have a higher spill-over fraction compared to previous patterns.