Can an Atmospherically Forced Ocean Model Accurately Simulate Sea Surface Temperature During ENSO Events?
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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The performance of an atmospherically forced ocean general circulation model OGCM in simulating daily and monthly sea surface temperature SST is examined during the historical El Nino Southern Oscillation ENSO events during the time period 1993 -2003. For this purpose, we use the HYbrid Coordinate Ocean Model HYCOM configured for the North Pacific north of 20 degrees S at a resolution of 9 km. There is no assimilation of or relaxation to SST data and no date-specific assimilation of any data type. The ability of the model in simulating temporal variations of SST anomalies is discussed by comparing model results with two satellite-based SST products. The HYCOM simulation gives a basin-averaged monthly mean bias of 0.3 degrees C and rms difference of 0.6 degrees C over the North Pacific Ocean during 1993 -2003. While the model is able to simulate SST anomalies with mean biases 0.5 degrees C in comparison to observations during most of the ENSO events, limitations in the accuracy of atmospheric forcing specifically, net short-wave radiation have some influence on the accuracy of simulations. This is specifically demonstrated during the 1998 transition period from El Nino to La Nina, when a record large SST drop of 7 degrees C occurred in the eastern equatorial Pacific Ocean.
- Physical and Dynamic Oceanography
- Operations Research