1. 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

2. 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

3. 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

4. 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:
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

5. 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

6. 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 K
19 years of swath data
Dataset available from NCEI CDR website
AMSU-A brightness temperature s for overlapping NOAA-15 and
NOAA Their differences for randomly selected region
(e.g., within the dashed square ) are within K.
FCDR provides ability to inter-compare at various times of the day

7. 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

8. 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:

9. 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.

10. 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

11. 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.

12. THANK YOU

13. 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 = 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.