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# This README file lists ESA-recommended QC for Aeolus L2B wind products.
#
#	Last Updated: 2021-02-02	K.Lukens	NOAA/NESDIS/STAR
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- The following quality control (QC) decisions recommended by ESA are listed in an Aeolus Technical Note released on August 31, 2020.
 
- This list of QC recommendations are for NON-REPROCESSED data for the Early FM-B period (August 2, 2019 - December 31, 2019) and Mid-2020 FM-B period (April 20, 2020 - late August 2020).

- L2Bp estimated observation error scaling of 1.4 for Rayleigh-clear, and 1.75 for Mie-cloudy. These were based on "Desroziers diagnostics" (Desroziers et al. 2005).

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= Current QC Decisions recommended by ESA
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 1. Only assimilate Rayleigh-clear and Mie-cloudy winds with "valid" overall confidence flag.
 2. Do NOT assimilate data within 20 hPa (~160 m) of the surface (to try to avoid any undetected ground returns).
 3. Avoid Rayleigh winds at pressure > 850 hPa. (It is unclear if this was necessary, but there were some indications of degradation when using 
    boundary layer surface Rayleigh winds.)

 4. Do NOT use any Rayleigh-clear winds with: 
	a. Estimated errors (before error scaling) > 12 m/s if pressure <= 200 hPa (to try to allow data in the wintertime polar vortex).
	b. Estimated errors (before error scaling) > 8.5 m/s if pressure > 200 hPa.
	c. Horizontal accumulation lengths < 60 km. 	(This pertains to Integration Length.)
	d. Vertical accumulation lengths < 300 m. 	(This pertains to the difference in the top and bottom heights of the range-bin: 
							 top height minus bottom height.)
							 
 5. Do NOT use any Mie-cloudy winds with:
	a. Estimated errors (before error scaling) > 5 m/s.

 6. For Rayleigh-cloudy wind experiments, do NOT use if:
	a. Estimated errors (before error scaling) > 5 m/s (This was found to be reasonable QC for removing gross errors).



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% OLD QC Recommendations
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 === Rayleigh winds ===
       Remove:
               Rayleigh cloudy
               Height < 2 km
               L2B Uncertainty (wind error estimate) > 12 m/s
               Accumulation length < 60 km
               Within 20 hPa of topography (here, we remove p>800 hPa)

 === Mie winds ===
       Remove:
               Mie clear
               L2B Uncertainty (wind error estimate) > 5 m/s
               Accumulation Length < 5 km
               Thinned to 90 km

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