Atmospheric precipitation in response to equatorial and tropical sea surface temperature anomalies
- Princeton Univ., NJ (United States)
Three sets of numerical experiments based on a GFDL GCM were developed to investigate the response of the large-scale tropical circulation and precipitation to the tropical and equatorial sea surface temperature (SST) anomalies. SST anomaly (SSTA) with a small latitudinal scale of 13.5[degrees] was imposed in regions of the Pacific Ocean in different sets of experiments and added to the climate-mean August SST to form a lower boundary forcing. Each set is two experiments in which the SSTA has the same coverage and intensity but opposite sign. Anomalies of meteorological fields are calculated as the differences between the results of the warm and cold SSTA experiments. Prominent anomalous low-level convergence and high-level divergence are observed over the warm SSTA regions. For experiments with warm SSTA placed at the equator, responses of the tropical streamfunction are similar to corresponding results found in other studies. When the warm SSTA is placed in the warmest SST region in the western North Pacific away from the equator, the excited anomalous streamfunction is different from that in the equatorial SSTA cases. Anomalous rainfall is balanced mainly by anomalous convergence of stationary water flux; transient flux and anomalous evaporation from the warm water surface are secondary. Advection of water vapor by the large-scale flow and its anomaly were significant in determining the rainfall pattern. Anomalous precipitation occurs in regions where the mean flow is down the SSTA gradient, or the anomalous flow is down the mean SST gradient. Advection of anomalous water vapor by strong low-level equatorial easterlies in the eastern equatorial Pacific causes anomalous rainfall associated with the warm SSTA in the region to shift westward. Away from the equator, advection of water vapor by the anomalous rotational wind becomes important. This contributor causes anomalous rainfall to shift away from the warmest SST region in the western North Pacific.
- OSTI ID:
- 6507195
- Journal Information:
- Journal of the Atmospheric Sciences; (United States), Vol. 49:23; ISSN 0022-4928
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ATMOSPHERIC PRECIPITATIONS
COMPUTERIZED SIMULATION
PACIFIC OCEAN
TEMPERATURE MONITORING
ADVECTION
CLIMATE MODELS
EQUATOR
EVAPORATION
EXPERIMENTAL DATA
RAIN
SOUTHERN OSCILLATION
TROPICAL REGIONS
WATER VAPOR
WIND
DATA
FLUIDS
GASES
INFORMATION
MASS TRANSFER
MATHEMATICAL MODELS
MONITORING
NUMERICAL DATA
PHASE TRANSFORMATIONS
SEAS
SIMULATION
SURFACE WATERS
VAPORS
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