Multi-year Trends in MODIS and MISR Observed Cloud Fraction over the Extratropical Oceans

Thesis (Master's)--University of Washington, 2016-06

Examination of cloud fraction and top of atmosphere radiation data from NASA’s MISR, MODIS, and CERES instruments reveals a pervasive temporal decline in optically thick cloud over the extratropical ocean basins during the period 2000 to 2015, which is compensated by a corresponding increase in cloud of moderate optical depth. While cloud optical depth has changed in these regions, no significant trend in total cloud fraction or large scale area-averaged albedo over the world's oceans has been observed by these instruments during this period. Likewise, no significant poleward shift in cloud associated with the extratropical storm tracks has been observed during this period. These changes in cloud fraction have had an observable effect on albedo at regional scales and comparison to ECMWF reanalysis data and NOAA CPC climate indices indicates that they are the result of intra-decadal to decadal scale synoptic variability, which may be natural climate variability.