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CrIMSS EDR Cloud Leakage (DR 7205) Investigation Report

CrIMSS EDR Cloud Leakage (DR 7205) Investigation Report. NGAS A&DP CrIMSS Team Aug 8, 2013. Undetected Clouds Causing Clear Retrieval Poor Performance Near the Surface. Problem occurred under low overcast cloudy conditions

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CrIMSS EDR Cloud Leakage (DR 7205) Investigation Report

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  1. CrIMSS EDR Cloud Leakage (DR 7205) Investigation Report NGAS A&DP CrIMSS Team Aug 8, 2013

  2. Undetected Clouds Causing Clear Retrieval Poor Performance Near the Surface • Problem occurred under low overcast cloudy conditions • Because overcast scenes are erroneously identified as clear, anomalous retrievals are produced and not flagged as degraded • Two possible fixes have been proposed and tested: • At the second stage retrieval, if an FOR is classified as a clear scene, force CLW to be zero in the retrieved profile for each iteration. This should result in high chi-square values for the misclassified scenes. Flag those retrievals as cloudy and report MW only results (NGAS) • Compare microwave only retrieved skin temperature with that from the MW/IR combined retrieval; if the difference exceeds a pre-set threshold, flag the retrieval as cloudy and report MW only results (LaRC) • Fixes developed and tested using G-ADA and off-line code • Golden Day 9-20-2012

  3. Correlation between AVTP/AVMP accuracy and Retrieved Tskin Difference AVMP AVTP

  4. Improved AVTP Performance After Fixes AVTP quality (bias and standard deviation) over clear ocean

  5. AVMP Performance Changed Little After Fixes AVMP quality (bias and standard deviation) over clear ocean

  6. Other Considerations • Yield • Fix I has a slightly fewer number of retrievals passed QC • Operational implementation • Fix I: Minor code change • Fix II: Minor code change. Need to determine a threshold for flagging overcast conditions – necessary to modify PCT file to make the threshold value tunable

  7. Summary • The fixes proposed by LaRC and NGAS seem to be effective to flag low overcast clouds that have not been detected by the current algorithm • Need to decide whether and when to make the change to the operational software

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