In-orbit Microwave Reference Records 11 June 2018 In-orbit Microwave Reference Records Manik Bali, Cheng-Zhi Zou, Lawrence E Flnn and Ralph Ferraro MW Subgroup Meeting January 11, 2016

Outline Outline Introduction Selection matrix of In-orbit reference for MW Proposed in orbit reference for MW . Temperature and Scan Angle dependence of SATMS – FCDR bias Summary 04/08//2013

Introduction Introduction Need an in-orbit reference for MW In orbit Microwave instruments are often compared to in-situ targets and GPS-RO measurements. These comparisons get influenced by local weather conditions and usually require a forward model to compute the TOA (Top of Atmosphere) MW reference radiances from the in-situ and GPS-RO measurements. Inter-comparisons do not reveal the full scale of instrument biases such as scan angle dependence of measurements, temporal trends and temperature dependence of bias Need an in-orbit reference for MW How do we select one

Proposed- Process to identify GSICS reference Instrument The instrument and Channels agency wishes to monitor. The method/s they would employ to monitor( eg. single or blended references, use transfer target , stability criterion). May consider scoring proposed by Hewison and Reference Expectations gathered by GSICS Survey ( stated next slidse) Demonstrated use of the instrument by member agencies and users for instrument monitoring. Comparison of Instrument design specification ( Pre-launch testing) with In-orbit behavior. May consider if in-orbit status of key parameters of Candidate Ref instrument are monitored and available to users ( such as . ICVS). 7. Take Info ( global coverage, eq. cross time etc) related to instrument available ( eg OSCAR) Phone: +1 301-683-3550 Reference Selection Matrix 1. Sensor Record performance stability 2. Field of view (FOV) consistency (ATMS has oversampling FOV and can be B-G to AMSU-A and MSU) 3. Error budgets (prelaunch characterization and postlaunch verification) 4. Geolocation accuracy 5. Data availability

In-orbit references The AMSU/MSU L1B FCDR for O2 bands resembles a typical in-orbit reference that is stable and accurate. Has scan angle corrected radiances De-trended time series. Undergoes stringent quality assurance test Real time quality flags for each pixel provided with the product

MW References AMSU-A FCDR as a Reference for Cross-Calibration AMSU-A onboard six POES satellites were inter-calibrated using Integrated Microwave Inter-Calibration Approach (IMICA) 5 calibration errors were removed/minimized: nonlinearity, bias drift, frequency shift, sun-heating induced temperature variability in radiances; Inter-satellite Biases were reduced to 0.1-0.2K 19 years of swath data Dataset available from NCEI CDR website AMSU-A brightness temperature s for overlapping NOAA-15 and NOAA-18. Their differences for randomly selected region (e.g., within the dashed square ) are within 0.1-0.2K. FCDR provides ability to inter-compare at various times of the day

AMSU/MSU FCDR as a reference: Current progress Coded and Setup an AMSU – ATMS inter-comparison SNO algorithm NOAA-GDWG has helped AMSU FCDR resemble a typical MW orbit file – scan time stamps that can be used to generate SNO’s, uniformity of file format (NetCDF4) across time spans has been achieved. Computed AMSU footprint size Created a three month database of AMSU-FCDR – ATMS collocations. Scan angle corrected BT included that resemble RVS corrected IASI/VIIRS radiances and are used as reference. Next steps- analyze the collocations data set Once we have an in-orbit reference we can generate in-orbit cross calibration products

Overlap with Monitored instruments AMSU/MSU FCDR AMSR (2/E) JAXA MWTS-2 China SSMI DOD MTVZA ROSCOSMOS/Ukraine GMI NASA ATMS MSU/AMSU-A FCDR channels overlap with majority of MW instruments Source: https://www.wmo-sat.info/oscar/instruments

Monitoring ATMS-SDR by SNO inter- comparison with N18 Inter- comparison of ATMS-SDR with FCDR show Low scan angle dependence of ATMS-SDR Post launch ATMS-SDR maintains nearly pre-launch level of accuracy.

Monitoring ATMS-SDR by SNO inter- comparison with FCDR Aqua FCDR extremely consistent as a reference  Compared to N18, Inter- comparison with AQUA-AMSU FCDR gives similar results

Summary Rules of identifying in-orbit reference being formulated We made progress with evaluating the AMSU/MSU FCDR as a in-orbit reference. AMSU/MSU – SATMS Collocation data( N18 and Aqua) set extended to Dec 2016. AMSU/MSU – SATMS shows pre-launch level of temperature dependence and low scan angle dependence. FCDR measures the temperature dependence and scan angle dependence of bias realestically Further work underway to produce long time series of collocations.

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SATMS –AMSU-A 55.5 GhZ bias [NOAA-18] Collocations extended to Oct 2016 Stable temperature dependent bias Zenith angle dependence similar to model calculations Offset = -0.29 K Figure above shows pre-launch level of bias of SATMS Figure right Shows the scan angle dependence of ATMS-SDR is within 1% of the Nadir view when compared with the limb corrected AMSU-MSU FCDR.