GRWG/GDWG Web Meeting 20230504

Agenda

  1. Di Di and ZhengLong Li (SSEC/UW): Inter-calibration of geostationary imager and sounder on Fengyun Satellite

  2. Likun Wang (ESSIC/UMD): Angle effects on collocation related to the algorithm improvements

Attendees (18)

Guest Chair: Likun Wang

CMA: Chengli QI, Hanlie Xu, Xingwei He, Lu Lee, Yong Zhang, Zhiwei Wang, Zhiwei Wang

EUMETSAT: Tim Hewison, Ali Mousivand, Vincent Debaecher

JMA: Masaya Takahashi

KMA: Euidong Hwang

NOAA: Fangfang Yu, Manik , Likun Wang

UW: Di Di

ESA: Stefano Casadio

Univ. of : Martin Burgdorf

TNO: Gerard Otter

Summary

Di Di and ZhengLong Li (SSEC/UW): Inter-calibration of geostationary imager and sounder on Fengyun Satellite

Di Di (from SSEC/UW) presented Inter-calibration results of Geostationary Imager Infrared Bands Using a Hyperspectral Sounder on the Same Platform, which was recently published on Geophysical Research Letters, 50, e2022GL101628. https://doi.org/10.1029/2022GL101628. The results were based on the comparison of collocated AGRI band 12 and band 13 with GIIRS measurements from 01 to 07 July 2020 to addresses GEO imager specific calibration questions such as viewing angle dependence, scene (clouds, etc.) dependence, and diurnal characteristics.

Fangfang Yu: Can Local zenith angle reach 90 degree? Can zenith angle dependent pattern be corrected? The possible root causes are from collocation, or instruments

A: It should be very cautious when zenith angle gets large. At this stage, the root causes are not clear. :

Tim Hewison (comments): Welcome and thank you for sharing with us. It is a new idea to divide the scene by using clear sky, partially cloudy, and overcast cloudy scenes.

Tim Hewison: How about the spectral coverage for Band 14?

A: The results are not good and are not meaningful.

Tim Hewison (comments): Did you check diurnal variation over sea and overland. Did you find the bias over hot land issues? I would suggest that you breakdown the scenes into over sea or over land.

Martin Burgdorf: When can I get the GIIRS data with updated coefficients in the future?

A: For GIIRS/FY4A, it will plan to update in this summer.

Cheng-Li Qi: How do you perform the bias correction?

A: We will make two sensors consistent to each other.

Di Di will follow up to check 1) Band 14 results. 2) hot land issues

Likun Wang (ESSIC/UMD): Angle effects on collocation related to the algorithm improvements

To respond the action “A.GIR.20230301.1: Likun Wang (NOAA) will investigate parallax effects for GEO-LEO IR v2 algorithm and report back to the IR group in early May 2023”, Likun Wang presented the investigation on the angle effects on collocation related to the algorithm improvements and explored a resolution to avoid parallax effects, especially at high view angles.

Di Di: What value of the angle threshold do you suggest avoiding parallax effects?

A: I suggest using 15 degrees to constrain the angle between the LOS vectors. It will keep many samples and reduce the parallax effects.

Tim: The zenith and azimuth angle constrains are channel dependent. How do you choose them?

A: Yes. This study uses window channel only. It is the extremely case for parallax effects in window channels. For other channels (water vapor and CO2 absorption channels), the threshold can be relaxed.

Manik: Will this be applied to the GSICS products?

A: We are making efforts to improve the GSICS GEO-LEO V2 algorithms by addressing several issues. After the V2 algorithms is completed, it will be applied into the GSICS products.

Fangfang: I think it is like the ray match of collocation in the visible channels, but uses different terminology (e.g., line of sight vectors). What are the effects if we apply it? Can you also check the GOES18?

A: Yes. I agree. For current GSICS algorithms, only constraining the zenith angles are not enough. We should follow the similar method as the visible channels. With regards to the effects, I think we should reduce the uncertainties at each step during the collocation. And then we can analyze
Topic revision: r4 - 26 Jun 2023, LikunWang
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