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Climate Variability |
Monitoring Climate Change in the Tropics
The figure below shows the anomaly time series for three climate state variables in the tropics (20 S to 20 N): sea-surface temperature (SST), lower tropospheric temperature (LTT), and total atmospheric water vapor (WV). Monthly averages are shown. The seasonal cycle has been removed to reveal the interannual variability, which is primarily driven by the El Niño - La Niña cycle. In the tropics, SST, LTT, and WV are closely coupled and exhibit relative scalings of WV/SST = 9.2%/K, W/LTT = 6.7%/K, and LTT/SST = 1.4, in close agreement with the Clausius-Clapeyron relationship and a moist adiabatic lapse rate.
The three primary El Niños during the past 20 years are clearly evident as peaks in the time series occurring during 1982-1983, 1987-1988, and 1997-1998, with the most recent one being the largest. El Niños are often followed by a La Niña cycle characterized by cooler than normal temperatures.
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