Ten-year Trends in African Dust Episodes and its Effects on the Bimodal Rainfall Patterns across the Northeast Caribbean

Thursday, 21 April 2016
Plaza Grand Ballroom (The Condado Hilton Plaza)
Odalys Martínez-Sánchez, University of Puerto Rico, Rio Piedras Campus, San Juan, PR

African Dust reaches the Caribbean region during late spring through early autumn, and results in hazy skies and limited rainfall activity. Aerosol Optical Depth (AOD) measurements retrieved from NASA's AErosol RObotic NETwork (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) are been analyzed to determine changes in the frequency and magnitude of Dust Days (DD) across the Northeast Caribbean. The changes in frequency and magnitude of DD may affect the onset of the rainy season as well as rainfall maximums during May and Oct-Nov through cloud-physics processes associated with particle number size distribution (PSD) and cloud condensation nuclei (CCN). In order to understand vertical profiles of PSD across the Northeast Caribbean during DD and dust-free days, data retrieved aloft during the Ice in Clouds Experiment-Tropical (Ice-T), and at ground during the Puerto Rican African Dust and Cloud Study (PRADACS) were analyzed. PSD measurements were obtained using a passive cavity aerosol spectrometer probe (PCASP) and a high-flow dual channel differential mobility analyzer (HDDMA) onboard the NCAR/NSF C130, and an optical particle counter (OPC) and a scanning particle sizerspectrometer (SMPS) at the ground-based atmospheric observatory of Cabezas de San Juan, Puerto Rico. Preliminary results showed homogeneous vertical structure of size distributions below 4km during DD, while a decreasing trend with height was observed during dust-free days. Size distributions were trimodal during DD, while bimodal distributions were observed during dust-free days. Trends in frequency and magnitude of DD continue to be analyzed, and preliminary results will be presented at the conference.
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