Assimilation of TOPEX Altimeter Data into a One and One-half Layer Model of the North Pacific

Data assimilation is carried out using a reduced-gravity model of the North Pacific forced by ERS-1 winds and TOPEX altimeter data. The assimilation method in this study is a nudging technique. The RMS differences between observation and model solutions are extremely small in the whole region. A large reduction of RMS differences is done during the first few steps of the nudging. The obtained RMS differences depend on the value of a nudging parameter. When the nudging parameter is 0.01, the results give the smallest RMS difference. However, there is little difference between the nudging experiments with and without a geostrophic correction. It should be noted that the assimilation results are hardly affected by the wind forcing.