Interannual variability of cloud cover from Terra MISR, MODIS, and ISCCP: ENSO influences

Terra MISR (Multiangle Imaging SpectroRadiometer) and MODIS (Moderate Resolution Imaging Spectroradiometer), and ISCCP (International Satellite Cloud Climatology Project) cloud cover observations are analyzed to characterize cloud responses to ENSO forcing. Cloud feedbacks, in terms of sign and amplitude of cloud amount response to SST in the Pacific, are estimated by regressing monthly cloud data to the ENSO (Nino 3.4) index. Compared to MODIS and ISCCP, MISR captures 20 to 40% more Marine Stratocumulus in the northeastern Pacific (NEP: west of North America) and the southeastern Pacific (SEP: west of South America). The ENSO-regressed low cloud patterns are generally consistent among thses observations with positive cloud feedback (decrease of low cloud with positive SST perturbation and increase of low cloud with negative SST perturbation), showing anti-correlation with the ENSO SST perturbation pattern. However, only MISR can capture the negative cloud feedback in the tropical eastern Pacific along the ITCZ. MISR cloud wind response to ENSO variability shows that the cloud response is linked to weakening of tropical Walker circulation.