Patterns of Coherent Climate Signals in the Indian Ocean during the 20th Century

Abstract

QBO, ENSO, and BDO fluctuations are identified in the Indian Ocean from a joint frequency domain analysis of sea surface temperature (SST) and sea level pressure (SLP) conducted over the 20th Century. Within the ENSO band (3‐ to 7‐year period), local fractional variance (LFV) is maximum near 3.4‐year period, revealing spatially coherent SST and SLP variability propagating eastward from the Horn of Africa and southwest Indian Ocean respectively, toward the eastern tropical Indian Ocean. Within the QBO band (2.1‐ to 2.8‐ year period), LFV is maximum near 2.2‐year period revealing spatially coherent SST and SLP variability propagating northward and eastward from Southwestern Ocean, toward the South China Sea. The 3.4‐year period ENSO signal diminished in intensity in the 1920s and 1950s, whilst the 2.2‐year period QBO signal diminished in the 1910s, 1940s, and 1950s, as observed for the global QBO and ENSO signals [White and Tourre, 2003].