The figure below shows the smoothed anomaly time series for three climate variables over the tropical oceans tropics (20 S to 20 N): sea-surface temperature (SST), lower tropospheric temperature (TLT), and total atmospheric water vapor (WV). Monthly averages are shown. The seasonal cycle has been removed, and the resulting anomaly time series smoothed to reveal the interannual variability. In the tropics, SST, TLT, and WV are closely coupled and exhibit relative scalings of WV/SST = 9.6%/K, W/LTT = 6.9%/K, and LTT/SST = 1.3, in close agreement with the Clausius-Clapeyron relationship and a moist adiabatic lapse rate, and predictions made by climate models (ref Mears et al, 2007, Santer et al 2005, 2007). In the figure, the TLT curve has been scaled down by a factor of 1.3 to reflect this scaling.
The three largest 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. In 2007-2008, a strong La Niña event occured without a preceding strong El Niño leading to reduced temperature and water vapor.
The Reynolds SST product is the NCEP optimally interpolated (OI) product available from NASA's Physical Oceanography Distributed Active Archive Center (PO.DAAC) / Reynolds Products.
It is blend of satellite retrievals from AVHRR and in situ observations (buoys and ships).
The TMI Microwave OI SST product is produced here at RSS from TMI aboard the TRMM satellite.
The SSMI Water Vapor product is also produced here at RSS from the SSM/I series of satellite radiometers.