PATMOS-x v6.0: 40-Years of Cloud Retrievals From Fused AVHRR and HIRS

Abstract:

The Polar Operational Environmental Satellites (POES) form the longest satellite global record of observations by similar instruments. The Pathfinder Atmosphere’s Extended (PATMOS-x) dataset is a long-term cloud record, suitable for climate analysis, and previously derived solely from the AVHRR radiances of POES. The limited number of AVHRR spectral channels makes accurate retrieval of cloud properties challenging, compared to sensors like MODIS or VIIRS, and especially over the poles. This lack of any stable long-term observations of cloudiness over the Arctic and Antarctica are significant barriers to quantifying the effect of cloud feedbacks in the polar climate.

To address these shortcomings, the High-resolution Infrared Radiation Sounder (HIRS) radiances available on all POES have been upsampled to AVHRR resolution and input into cloud property retrieval algorithms alongside the AVHRR radiances in the new version 6.0 of the PATMOS-x dataset. This additional spectral information improves both the baseline quality of the cloud properties as well as enables the homogenization of spectral channels across the multiple generations of AVHRR instruments. The increased number of channels is also accompanied by algorithmic improvements in the cloud mask.

In comparison with the previous version of PATMOS-x, we will show a large improvement of the cloud mask over the poles, using MODIS-based retrievals as reference. Retrieval of other cloud properties like cloud phase and cloud height is likewise improved with the new spectral channels (and cloud mask).