1. Aid to Users Selection of GSICS Products Thoughts on need for RAC/ARC products
Tim Hewison
EUMETSAT

2. Conceptual Flow Diagram to Select ProductQ1 Q2
NRTC
RAC Q3
Prime

3. What are the Questions?
Do you care about satellite instrument calibration? (!)
Check the ReadMe for each product!
Establish typical calibration errors for the instruments/channels being used
Mean bias
Variability
How sensitive are your products to these changes?
Don‘t bother!
Apply static correction
Apply dynamic correction
Is it a near real-time application?
Yes - Then you need the NRTC!

4. What more Questions?
Does your application cover the period of mulitple reference instruments?
No – Just use NRTC/RAC
Yes – Then: How sensitive is your application to typical changes between references? (Obviously need to know what these are!)
Sensitive – Then use a Prime Correction
Not sensitive – don‘t worry!
Need to provide information to potential users:
Mean Bias + Temporal Stabilty (for each channel) + variability/uncertainty
Spectral (inter-channel)
Repeat for Prime Corrections – Double-difference by-products
Based on ECV Inventory

5. Example from SEVIRI-IASI User Guide
Table 1 Summary Statistics of Pre-Operational GSICS Re-Analysis Correction for Meteosat-10/SEVIRI in Full Disc Scanning in the period / (All Uncertainties are k=1)
Meteosat/ SEVIRI Channel IR
3.9
6.2
7.3
8.7
9.7
10.8
12.0
13.4 m
Standard Radiance (as Tb)
284
236
255
261
286
285
267 K
Mean Bias (SEVIRI-IASI) for Standard Radiance Scenes
+0.60
-0.15
+0.08
-0.05
+0.05
+0.04
-0.86
Standard Deviation of Bias for Standard Radiance Scenes
0.04
0.03
0.02
0.10
Median Uncertainty of Bias for Standard Radiance Scenes
0.008
0.006
0.009
0.007
Random Uncertainty estimated as rolling standard deviation of Bias over 29d
0.011
0.012
0.015
0.010
Total Systematic Uncertainty from [Hewison, 2013]
0.003
0.002
0.004

6. Quick-look User Guides Disussion
Would it help users to be able to quickly find:
„Typical“ Mean Bias? & Calibration Variability?
Uncertainty of GSICS Correction?
For each channel of monitored instruments?
Does this information need to be static/dynamic?
Is it a „GSICS Product“?
Does this information need to be centralised?
Or can we make a template for agencies to provide this info?
e.g. On Instrument Information landing pages?
Link to GSICS Product Catalog entry?
How to integrate into guide to select GSICS products?

7. What about RAC/ARC? For discussion 9a on Friday
What is the difference between a Prime RAC and an Archive Re-Calibration?
Consistent processing versions?
Timeliness?
Something else?
Do we need both?
Can GSICS support Archive Re-Calibration products?
Aren‘t they FCDRs?

8. Thank you for your attention
Your thoughts here...