Tropical Multidecadal and Interannual Climate Variability in the NCEP–NCAR Reanalysis

Abstract

Abstract The leading tropical multidecadal mode (TMM) and tropical interannual (ENSO) mode in the 52-yr (1949– 2000) NCEP–NCAR reanalysis are examined for the December–February (DJF) and June–August (JJA) seasons based on seasonal tropical convective rainfall variability and tropical surface (land + ocean) temperature variability. These combined modes are shown to capture 70%–80% of the unfiltered variance in seasonal 200-hPa velocity potential anomalies in the analysis region of 30°N–30°S. The TMM is the dominant mode overall, accounting for 50%–60% of the total unfiltered variance in both seasons, compared to the 22%–24% for ENSO. The robustness of the tropical multidecadal mode is addressed, and the results are shown to compare favorably with observed station data and published results of decadal climate variability in the key loading regions. The temporal and spatial characteristics of this mode are found to be distinct from ENSO. The TMM captures the global climate regimes observed during the 1950s–6...