A global quasi-biennial wave in surface temperature and pressure and its decadal modulation from 1900 to 1994

Zonal wave number frequency spectra of surface temperature (ST) and sea lev el pressure (SLP) anomalies extending around the global tropical ocean at 1 0 degreesN from 1950 to 1997 display significant peaks for 2.0 and 2.4 year periods, dominated by eastward propagating zonal wave numbers of global sc ale. Applying complex principal component analysis to quasi-biennial ST, SL P, and surface wind (SW) anomalies for 25 years from 1973 to 1997 separates this global quasi-biennial wave (GBW) from corresponding global standing m odes, with patterns and evolution of the former similar to those observed i n the global El Nino-Southern Oscillation wave [White and Cayan, 2000] but centered on the equatorial waveguide and taking only 3 to 4 years (instead of 4 to 6 years) to transit the global tropical ocean at 0.30 to 0.40 in s- 1. We find the GBW contributing to the quasi-biennial signal in Nino-3 ST a nd SLP indices with amplitude twice that of global standing mode. In the GB W the ocean forces the atmosphere with SW anomalies directed toward warm se a surface temperature anomalies, while the atmosphere forces the ocean with SW-induced Kelvin waves on the equator and SW-induced sensible-plus-latent heat flux and/or vertical mixing anomalies elsewhere, both advancing ST an omalies eastward. Examining the GBW from 1900 to 1994 finds its amplitude m odulated by the decadal signal of similar to 10 year periodicity, robust (w eak) when tropical temperature gradients and trade winds were stronger (wea ker) than normal.