Looming Challenges –Microwave Calibration

Requirements for Precipitation Monitoring from Space

Challenge for IPWG: Passive Microwave sensor calibration and intercalibration to ensure homogeneous time series of data needed for

precipitation records -- how accurate do these need to be?

Ralph Ferraro, NOAA/NESDIS and Chair, GSICS Microwave Subgroup

* CGMS & CEOS – GSICS, SCOPE-CM, etc.

* GPM – X-Cal* NOAA - CDR’s* EU – Copernicus, FIDUCEO, etc.

* What does IPWG need?5-9 November 2018IPWG-9, Seoul, Korea 2

Current Activities….

* Put in the CGMS related actions assigned….* Anything in the HLPP?

5-9 November 2018IPWG-9, Seoul, Korea 3

Some marching orders from ‘above’

* Do any of these have precise numbers, methodologies, etc. that span all MW sensors/spectrums that are relevant for precipitation?

* What accuracy do we need? Do they vary for different applications?

* How do these impact specific retrievals

* Yes/No determination

* Precipitation Rates

* Inversion schemes

5-9 November 2018IPWG-9, Seoul, Korea 4

What does IPWG require?

1. Can IPWG develop specific calibration requirements:

* MW imagers

* MW sounders

* Radars?

2. What are the sensitivity studies that need to be undertaken?

3. XXX

4. YYY

5. ZZZ

5-9 November 2018IPWG-9, Seoul, Korea 5

Next Steps

BACKUP SLIDES

5-9 November 2018IPWG-9, Seoul, Korea 6

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Real time use and/or climate use?

Latency vs. precision?

Different spectrum has different use and requirements

Potential application areas

Specific Needs of Microwave Subgroup [Best Practices]

To understand need of Microwave Subgroup a survey was launched

Expectation from a reference instrument

Expectation from a reference instrument

-> Split verdict

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GSICS MW Products

Survey Results

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Window Channels

O2 Channels

H2O Channels

Average ~ 0.4 K

Average ~ 0.3 K

Average ~ 0.4 K

GSICS MW Products

* Post Launch Testing – Lessons Learned – Legacy Sensors

* Moderate Resolution Imaging Spectroradiometer (MODIS) * Suomi National Polar-orbiting Partnership (SNPP) - Visible

Infrared Imaging Radiometer suite (VIIRS)* Geostationary Operational Environmental Satellite (GOES)

series* Global Space-based Inter-Calibration System(GSICS)

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.

Series of MSU/AMSU-A provide a long term reference records spanning over a large range of time and full span of scan angles.

Proposed In-Orbit Reference

* Post launch MW instrument needs to be done by inter-comparing with records that are several time more stable than the target/monitored instrument.

Post Launch MW Instrument Monitoring

MW sounder

1. Sensor performance stability2. 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 accuracy5. Data availability

References: AMSU/MSU FCDR

Summary1) Mapping time series of similar sensors but from vastly different

heritage (e.g., SSMT2 to AMSU-B) together is of low priority 2) More precise, longer latency correction are preferred 3) It does appear most users would look at time series for global

trends (most likely the O2 & H2O bands) and use to derive geophysical parameters (most likely window & H2O bands)

4) The average desired accuracy of the corrections was on the order of 0.4 K (slightly less for the O2 bands)

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GSICS MW Products -Summary

GSICS Subgroups are the center of GSICS Cross Calibration Research and product generation.

1. The instrument and Channels agency wishes to monitor.2. The method/s they would employ to monitor( eg. single or blended

references, use transfer target , stability criterion). 3. May consider scoring proposed by Hewison and Reference

Expectations gathered by GSICS Survey ( stated next slidse)4. Demonstrated use of the instrument by member agencies and users

for instrument monitoring. 5. Comparison of Instrument design specification ( Pre-launch testing)

with In-orbit behavior. 6. 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

Process of Selection to be carried out within sub group.

Proposed- Process to identify GSICS reference Instrument

Selection Process Reference for MW

Identify a instrument andchannels one wishes tomonitor.

Identify the method to monitor

Consider usage of instruments for similar applications by agencies

Consider demonstrated use of the instrument by other agencies

If in-orbit status of key parameters ofCandidate Ref instrument aremonitored , are within specs andavailable to users ( via websitessuch as ICVS) OSCAR provides

limited but critical information on instruments. (spectral, temporal and geographical coverage)

Detailed information is

Pre-launch characterization Vs Post launch behaviour reports

Application of Process- Example-1

IR sounder1. Sensor performance stability2. Spectral coverage/Spectral resolution3. Error budgets (prelaunch characterization and post-launch verification)4. Geo-location accuracy5. Data availability

References: CrIS, AIRS IASI A/B/C can be GSICS References ( No Primary or Secondary)

What are we looking for in a Reference Instruments

MW sounder

1. Sensor performance stability2. 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 accuracy5. Data availability

References: ATMS SDR/TDR, FCDR

References: CrIS, AIRS IASI A/B/C can be GSICS References ( No Primary or Secondary)

Hyper-spectral radiances spanning wide spectrum not available in MW

AMSU-A FCDR of Window Channels• AMSU-A onboard six POES satellites were inter-calibrated using Integrated Microwave Inter-Calibration Approach (IMICA) for window channels, same as sounding channels

• Scan bias, nonlinearity and bias drift errors were removed/minimized;

• Inter-satellite standard deviation improved by 50%, comparing to 1b data sets;

• Swath data from 1998 to present

• Dataset available from NCEI CDR website

As accompaniments to AMSU-A FCDR of sounding channels, the window channels cover channels 1, 2, 3 and 15 (23.8, 31.4, 50.3 and 89.0 GHz), which are widely used in many other sensors, such as SSMI, SSMIS, ATMS, GMI and etc. These channels are mainly for the input to hydrological products, and land surface products.

Proposed In-Orbit Reference

•AMSU-A/MSU FCDR continuously monitored in Real time•Scan Angle Dependence has been corrected•Validated with GPSRO and instruments monitored at ICVS

Search for a MW Reference

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 à Compared to N18, Inter-comparison with AQUA-AMSU FCDR gives similar results

NOAA-18