GRWG/GDWG IR Group Web Meeting 2022-03-16

Q: How to use overlap in spatial density-enhanced acquisitions?
A: Could investigate applications requiring reduced noise
Q: Idea to use increased overlap test to check geolocation accuracy.

A: Expected same performance in terms of geolocation accuracy during test.
Q: Was the temperature increase during the maneuver expected?

A: Not expected

Q: Did the limb acquisition start before the maneuver?

A: Yes

Q: Data availability?

A: Yes – through NOAA CLASS and EUMETSAT Data Centre from Campaign #3 (End of Life tests), but not Campaign #4 (deorbitting tests)

Q: Have you compared with results of previous QSNO off-nadir comparisons?

A: Not yet – but in the plan

Q: Congratulations! Even though they said it couldn’t be done. How much processing work?

A: about 1 month – before end 2022

Propose to present at IR Web Meeting to consider whether GSICS proposes new dataset for IASI-A as anchor reference for FCDR generation.

Q: Any feedback on striping in CO2 channels from instrument scientists?

Fred Wu: strong VZA dependence evident in O-A maps – warrants further investigation

• Related to striping

• Could also check stripes correspond to instrument swaths

• Mark Liu: VZA dependence coming from RTM

Q: RTM error at 8µm - due to RTM or model inputs?

• Mark Liu offered to work together to resolve VZA dependence

Q: For high VZA, do you use a ray-trace through atmosphere to include multiple grid points?

A: no – could be a large effect for high VZA – could introduce systematic bias at high latitudes

Q: gaps in Indian Ocean?

A: Overlapped O-A from multiple instruments – could also use Meteosat-8/SEVIRI from 41.5°E in 2019

Q: More info on DARDAR cloud model?

A: Cloudsat+CALIPSO combined product, which reduced O-B bias

Q: Any sign of striping in O-B images?

A: Not found in ASR – but could be found in clear sky data, on close investigation

Q: Is model input uniform within each swath?

A: Use common profile – no 3D effects along slant-path – tricky in cloudy situations

Comment from Su-Jeong: striping issue observed only in CO2 channels – and due to detector differences.

Comment from Su-Jeong: striping issue observed only in CO2 channels – and due to detector differences.

Q: Why striping/banding only found in CO2 channels?

Web Meeting to follow-up on NWP method within GSICS

Discussion for Friday plenary session: Cooperation with RTM developers to document

Q: FY-4A also carries GIIRS - has this been used for any operational applications?

A: Chengli confirmed some papers have been published by CMA NWP on case studies (e.g. wind forecasting and hurricane monitoring)

A: Why change GIIRS focal plane detector layout?

A: long story - originally planned as an imager-sounder - new layout reduces off-axis effect

Q: What improvements in HIRAS-II design compared to HIRAS-I in instrument design?

A: Detector layout now more similar to CrIS + better noise performance + contiguous spectra + processing at full spectral resolution

Action: A.GIR.20220316.1: Chengli Qi (CMA) to share references of the papers you mentioned on the impact of GIIRS on NWP (winds, regional,... ) - done:

• https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093010

• https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093672

• https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093794

• https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL096207

• https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL095825

Q: What are the uncertainties in all the inputs? And how do you propagate them through the RTM? (see slide ~11)

A: conducted experiment with tropospheric emission spectrometer over Lake Tahoe - comparing with modelled radiances within 0.3K - will share poster

Comment: These are valuable dataset, but difficult working environment to collect

Q: Ground-up estimate of uncertainty in modelled top of atmospheric radiances?

A: Studies suggest 0.23-0.25K uncertainty from atmosphere + RTM - can share!

Q: With the movement of the moon and satellite and so on, how can you be sure the lowest count gives the good position of the moon in the FOV?

A: For the LW it is constant and easy to use, SW is more difficult we can’t be sure that we capture the moon

Q: About SEVIRI, there is saturation in the IR. We are not sure it is then possible.

A: Saturation is seen at specific phase angles. We need phase angle close to no moon (phase > 90) is possible, but not close to full moon where there will be saturation.