A new approach to improved SST anomaly simulations using altimeter data: Parameterizing entrainment temperature from sea level

Observed Topex/Poseidon/Jason-1 (T/P/J) altimeter sea level (SL) data are used to improve an empirical parameterization of the temperature of subsurface water entrained into the mixed layer (T_e). An inverse modeling method is first adopted to estimate T_e from a SST anomaly (SSTA) equation using observed SST and simulated upper ocean currents from an intermediate ocean model (IOM). An empirical relationship between anomalies of T_e (estimated) and SL (observed) from T/P/J altimeter is then constructed by utilizing a singular value decomposition (SVD) of their covariance. As compared with SSTA simulations using modeled SL data, the use of T/P/J SL data allows observed information about dynamic ocean adjustments to be built directly into the empirical T_e model being used to parameterize the thermocline effect on SSTAs. The improved T_e model leads to better SSTA simulations in the tropical Pacific. Cross validation is made to examine the sensitivity of the SSTA simulations to the period chosen for training the T_e model. The proposed approach provides a new way to more effectively use T/P/J altimeter data in climate studies.