Sensitivity of The Lmd General Circulation Model To Variations In The Sea Surface Temperature In Tropical Pacific
The objective of this work is to verify if the LMD general circulation model, in the ver- sion LMDZ, is capable to represent the La Niña interanual variability. For that, it was necessary to study the sensitivity of the LMDZ model to sea surface temperature vari- ations. The model was integrated for 6 months (from September/98 to February/99) with maximum resolution grid centered in Rio de Janeiro state. The experiment is based in two simulations: the first with mean SST (control case) and the second in- troducing an artificial cooling in the eastern Tropical Pacific Ocean to simulate the La Niña phenomenon of 1998 (artificial cooling case). It was chosen for the artificial cooling a anomaly value of -2,5 zC, that was the mean cooling of the eastern Tropical Pacific Ocean from September of 1998 to February of 1999.So as to verify the performance, the anomaly fields generated by the model for the months Dez/Jan/Fev 98/99 were compared to the observed anomaly fields for the same period (artificial cooling case minus control case). The chosen fields for comparison were the surface pressure anomaly, 850 hPa level temperature anomaly and precipi- tation anomaly. In the surface pressure anomaly field simulated by the model there is an intensification of the Pacific high pressure, and a reduction of pressure is observed in the continental region close to Platinum plain. These anomalies were verified in the observed field, mainly the positive anomaly in the South Pacific Region. However, the center of negative anomaly is a little displaced for southwest in relation to the diagno- sis. In relation to the 850 hPa level temperature anomaly field, it can be easily observed that the results of the model follow a close behavior to the observed values, however the maximum and minimum anomalies centers are a little moved. For the precipitation anomaly field, it was found a decrease of the precipitation in the Equador/Peru coast, a notable increase in the east Amazon and in the north of the Brazilian Northeast Re- gion, which were already expected. Besides, it is noticed a considerable increase of the precipitation in Espírito Santo and south Bahia states and a negative anomaly nucleus close to Paraguay, both confirmed by the observations.
EGS General Assembly Conference Abstracts
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