MODAPS PCR 2007-05-16
| PCR Number | |
|---|---|
| Date | 2007-05-16 |
| Initiator | Richard Frey |
| Abstract | Resolved problem where CTP retrievals failed due to negative GDAS relative humidity interpolations near the surface in extremely dry polar regions. |
| Problem Statement | Interpolation of mixing ratio vertical profiles (computed from GDAS relativehumidities) sometimes leads to very small but negative values at or near thesurface in extremely dry atmospheres. These negative values are then disallowed by the code and no CTP retrievals are produced using that profileas input. This leads to MOD06CT output data "holes" in polar regions duringpolar night, late polar autumn, and early polar spring. |
| Description of Change | When a mixing ratio value < 0.0 and >= -0.5 g/kg is found, change it to a small positive value. This has no effect on the resulting MOD06CT output products. Values < -0.5 g/kg are still disallowed and cause the retrieval to fail. Also, removed a check on the value of surface mixing ratio since this parameter is unused in the present algorithm. |
| Products Affected | MOD06_L2 |
| Software Affected | PGE06 |
| Processing String to Receive the Change | Terra Forward, Aqua Forward |
| Downstream Product Effects | Any Atmosphere L3 products using cloud top pressure, cloud effective emissivity as input |
| Data Granules to be Used for Science Testing | |
| Justification | Many 1-degree sized data "holes" are present in some polar night granules. As many as 0.6% of the total CTP retrievals for a calendar day in a mid-solstice season have been found. After the change, the total is lowered to approximately 0.05%. Those remaining are due to missing or bad radiance data, missing cloud mask input, etc. |
| Effective Date for Implementation of Change | |
| Status |
