Characterization and Validation of the Heat Storage Variability from TOPEX/POSEIDON at Four Oceanographic Sites

Oceanic heat storage and heat storage rate are correlated to the sea surface height anomaly signals from the TOPEX/Poseidon altimeter data from 1992 to 1998. The height anomaly data are decomposed into three components through finite impulse response 2D filtering: a basin-scale non-propagating signal (h_t), a large to meso-scale westward propagating signal (h_W) and a residual (h_R). h_t is mostly due to the seasonal heating and cooling of the sea surface in addition to basin-scale advective effects. h_W is dominated by first-mode baroclinic Rossby waves and is further subdivided into several bands with periods ranging from 45 days to two years. Similarly h_R is decomposed into components associated with equatorial Kelvin waves, meso-scale eddies and a small-scale high-frequency residual. The fractional variance of the components of the altimeter data establish a quantitative correspondence between the local dynamical processes and the heat storage variability. To validate the heat storage estimates from the remotely sensed data correlations and mean differences are estimated relative to estimates derived from in situ measurements. Four sites have a nearly continuous time series of temperature profiles of the upper ocean simultaneous with most of the TOPEX/Poseidon (T/P) data: TOGA/TAO, HOT/ALOHA, CalCOFI and Hydrostation S. In situ salinity measurements are used in contrast with climatology in the corrections for haline expansion of the water column. The use of in situ salinity estimates significantly augmented the correlations and decreased the rms differences between both heat storage and heat storage rate estimates. The Rossby wave aliasing problem affects estimates of amplitude, wavelength and phase speed of first mode baroclinic Rossby waves at mid-latitudes. The TOGA/TAO region shows a high correlation between the heat storage estimated from in situ and T/P time-series. The rms differences are in average 43x10⁷Jm^-2 and the mean correlation is 89%. For Hydrostation S, HOT/ALOHA and CalCOFI sites the heat storage correlations are, in average, 82%, 75% and 70% while the mean rms differences are 63x10⁷Jm^-2, 55x10⁷Jm^-2 and 55x10⁷Jm^-2.