Characteristics of a Marine Stratocumulus to Cumulus Cloud Transition
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The studies in this thesis aim to improve the overall understanding of the characteristics of the marine stratocumulus to shallow cumulus transition over the southeast Pacific Ocean. This study uses observations from CloudSat and CALIPSO satellite instruments in NASA’s A-Train constellation to analyze environmental, microphysical and macrophysical cloud properties, precipitation, and cloud radiative effects along the climatological wind trajectories between January 2007 and December 2010. The interannual, intraseasonal, and diurnal variability of clouds across the transition over the study region is also examined. Results show that as trade winds advect equatorward from the Peruvian coastline to warmer waters, thick, persistent, low-level stratocumulus clouds with high cloud fractions and strong shortwave cloud radiative effects in the southern portion of the study region gradually transition to shallow cumulus clouds with decreased cloud fractions and cloud radiative effects. The speed of this transition exhibits interannual, seasonal, and diurnal differences associated with changes in the large-scale environment. More frequent and intense precipitation along the trajectory corresponds to a more rapid reduction in cloud cover, implying that it may play a role in the transition through its reduction in cloud water and stabilizing effect on the boundary layer. Results also suggest that capturing the variability in the transition from stratocumulus to shallow cumulus clouds is important for improving representation of cloud feedback effects in current climate models.
Zapalac, Allison (2014). Characteristics of a Marine Stratocumulus to Cumulus Cloud Transition. Master's thesis, Texas A & M University. Available electronically from