*CLD Section

25NOV24
Type
Optional Section

Description
Change default criteria for handling clouds

Structure
Multiple PARAM=VALUE fields, any order.

Fields
Param Type Description Units Range Default
Nadir-Viewing
PIXCLD R Maximum Cloud Fraction[2] % 0–100 0.0
Limb-Viewing
CIXCLD R Maximum Cloud Index[3] −1 or >0 1.8
RADCLD R Minimum Cloud Radiance[4] ru −1 or >0 125.0
TOPCLD R Maximum Cloud Altitude[6] km −1 or >0 30.0

Notes
  1. These settings only have any effect on the retrievals if the CLD Flag in the *FLG section is set, otherwise the only effect is on the thresholds for which warning messages on possible cloud contamination are sent to the morse.log file.

  2. PIXCLD (for nadir-viewing) sets the maximum pixel cloud cover, as defined in the IASI L1C file, for a pixel to be used for the retrieval.

  3. CIXCLD is the maximum value of the U.Leicester Cloud Index for which the sweep will be assumed cloud-contaminated (ie assumed cloud free for higher values). Note that a Cloud Index of 0.0 in the L1C input file is assumed cloud-free.

  4. RADCLD is the minimum radiance in the MIPAS cloud detection channel (960.7cm-1) for which the sweep will be assumed cloud contaminated, (ie assumed cloud-free for lower values).

  5. Clouds are flagged if either the Cloud Index or the Cloud Radiance tests indicate a cloud. Set values of -1 to turn off either or both tests.

  6. TOPCLD sets the maximum altitude for which a cloud can be flagged. This is necessary because Cloud Index values become a bit random at high altitudes due to noise. Setting this to -1 turns off any altitude limit, but is not recommended unless CIXCLD=-1 also.

  7. Default values are set in module cldcom_dat.f90 and reported at the start of the morse.log file.

Example
*CLD RADCLD=-1 ! Remove Cloud Radiance threshold test CIXCLD=2.2 ! Set more stringent Cloud Index threshold