HR: 11:50h
AN: A32B-07    [Abstracts]
TI: The Effect of Oceanic Eddies on Marine Stratocumulus in the Southeast Pacific
AU: * Wijesekera, H W
EM: hemantha@coas.oregonstate.edu
AF: Oregon State University, COAS, 104 OC Admin, Corvallis, OR 97331, United States
AU: Paulson, C A
EM: cpaulson@coas.oregonstate.edu
AF: Oregon State University, COAS, 104 OC Admin, Corvallis, OR 97331, United States
AU: Maloney, E
AF: Oregon State University, COAS, 104 OC Admin, Corvallis, OR 97331, United States
AB: Air-sea interaction in the South East Pacific (SEP) plays an important role in the regional and global climate system. The combination of cold sea surface temperature (SST) and subsiding warm, dry air provide an ideal environment for the formation of marine stratocumulus clouds in the SEP. In this study, the modulation of clouds due to ocean meso-scale fluctuations has been examined using multi-year satellite data sets. Monthly averaged and 0.25 deg gridded sea surface temperature (SST), column water vapor (CWV), column liquid water (CLW), vector winds, and sea surface height (SSH) have been used to examine correlations among monthly anomalies of SST, SSH and cloud moisture parameters. Monthly anomalies, constructed by removing 6-year (1998-2003) monthly means, were averaged into 0.25C bins, over a 10x10 deg box centered at 20S, 85W. The analysis indicates that the anomaly of SST is highly correlated with anomalies of SSH and CWV. Wind divergence at height of 10-m shows a negative correlation with SST anomaly. A relationship of CLW anomaly with SST anomaly shows different phases of cloud formation. Preliminary interpretation suggests that high values of wind divergence are associated with low SST anomaly and relatively high CLW, consistent with descending air and relatively dense stratus clouds. For SST anomalies near zero and slightly positive, wind divergence is intermediate and CLW exhibits a broad minimum, consistent with weak subsidence and relatively less dense stratus. For SST anomalies in excess of 1C, there is evidence of the break-up of stratus into cumulus clouds driven by convection. Typically cold, negative SSH anomalies (cyclonic eddies) are regions of high biological productivity, which may lead to the generation of aerosols in the marine atmosphere. Therefore the clouds may be modulated by upper ocean biological productivity in addition to SST and wind.
DE: 3307 Boundary layer processes
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 4504 Air/sea interactions (0312, 3339)
DE: 4520 Eddies and mesoscale processes
DE: 4572 Upper ocean and mixed layer processes
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly