Impact of African Dust on Clouds and Precipitation in a Caribbean Tropical Montane Cloud Forest

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The project will combine field and modeling investigations to address how the physico-chemical properties of long range transported African dust (LRTAD) aerosol influence Caribbean cloud properties and precipitation levels in a unique Puerto Rican tropical mountain cloud forest (TMCF). TMCFs occur globally in the Americas, Africa, and Asia and represent a primary source of drinking water. Three major hypotheses will be tested: 1) are cloud properties in the TMCF different during intense LRTAD periods; 2) Does LRTAD have unique chemical and physical properties which influence cloud properties and processes; 3) what is the correlation between precipitation patterns and LRTAD events? The study will be performed in Puerto Rico (PR), at Pico del Este (PE) and Cape San Juan (CSJ) stations. PE is in a TMCF with an elevation of 1051m asl which is at/above the cloud condensation level. This location facilitates the study of clouds without the need for aircraft studies which reduces the overall complexity and costs while allowing longer term observations within a single cloud. CSJ is a near sea level regional station of the Global Atmosphere Watch, upwind from PE, and is the first contact point for the trade wind air masses in PR. This station allows the sampling of the properties of the aerosol that enter the cloud (below-cloud aerosol). Data on the chemical and physical properties of aerosols, clouds, and rainwater samples will be collected via long term measurements and during an intensive field campaign in year 2. Using these results in conjunction with existing data sets of precipitation, cloud cover, temperature and humidity profiles and surface energy budgets, the sensitivity of precipitation distribution to LRTAD events will be investigated, particularly focusing on the length and intensity of the summer dry season in the Caribbean. Underrepresented student groups will interact with scientists and state-of-the-art instrumentation and be exposed to unique research opportunities. The regional capacity to cope with AD and climate change will be strengthened. Project results will be used in educational materials for students and communities over a range of educational levels. The "Program of Intensive Short Courses in Atmospheric Sciences", where CoPIs/collaborators will offer a short course at the University of Puerto Rico-Rio Piedras (UPR-RP), as well as the exchange of students among participating institutions will compensate for the non-existent curricula in atmospheric sciences at the UPR-RP.