Focused Study of Interweaving Hazards Across the Caribbean

Braun J.J, Mattioli G.S., Calais E. Focused Study of Interweaving Hazards Across the Caribbean. EOS Vol. 93, No 9, 28 Feb 2012.

The Caribbean is a region of lush vegetation, beaches, active volcanoes, and significant mountain ranges, all of which create a natural aesthetic that is recognized globally. Yet these very same features, molded through geological, oceanic, and atmospheric processes, also pose natural hazards for the developing countries in the Caribbean. The rise in population density, migration to coastal areas, and substandard building practices, combined with the threat of natural hazards, put the region’s human population at risk for particularly devastating disasters. These demographic and social characteristics exist against a backdrop of the threat of an evolving climate, which produces a more vigorous hurricane environment and a rising average sea level. The 12 January 2010 earthquake in Haiti and Hurricane Ike (2008) both caused widespread destruction and loss of life, illustrating the need for a scientific focus on the underlying natural hazards of the Caribbean. Prompted by these and other events, a new National Science Foundation (NSF)– funded initiative known as the Continuously Operating Caribbean Observation Network (COCONet), which commits roughly $7 million over 5 years to a collaborative natural hazard research team, was formed in 2010. This team includes researchers from UNAVCO, Purdue University, University of Puerto Rico at Mayagüez, and the University Corporation for Atmospheric Research (UCAR)

Climate is affected more by maritime than by continental land use change: A multiple scale analysis

Van der Molen, M. K., Dolman, A. J.,Waterloo, M. J. and Bruijnzeel, L.
A. 2006. Climate is affected more by maritime than by continental land
use change: A multiple scale analysis. Global and Planetary Change,
54, 128–149.

Tropical deforestation appears to have larger impacts on local, regional and global climate when it occurs under maritime conditions rather then under continental conditions. At the local scale, we compare results from a field experiment in Puerto Rico with other long-term studies of the changes in surface fluxes after deforestation. Changes in surface fluxes are larger in maritime situations because a number of feedback mechanisms appears less relevant (e.g. the dependency of soil moisture on recycling of water and the larger reduction of net radiation in the wet season due to clouds in continental regions). Pastures may evaporate at similarly high rates as forests when soil moisture is sufficient, which has a strong reducing effect on the sensible heat flux after deforestation. At the regional scale (∼102 km2), model simulations show that the meso-scale sea breeze circulation under maritime conditions is more effective in transporting heat and moisture to the upper troposphere than convection is in the continental case. Thus islands function as triggers of convection, whereas the intensity of the sea breeze-trigger is sensitive to land use change. At the global scale, using satellite-derived latent heating rates of the upper troposphere, it is shown that 40% of the latent heating associated with deep convection takes place in the Maritime Continent (Indonesia and surroundings) and may be produced mostly by small islands. Continents contribute only 20% of the latent heating of the upper troposphere. Thus, sea breeze circulations exert significant influence on the Hadley cell circulation. These results imply that, from a climate perspective, further deforestation studies would do well to focus more on maritime conditions.

A Statistical Method for Forecasting Rainfall over Puerto Rico

Carter MM, Elsner JB. 1997. A statistical method for forecasting rainfall over Puerto Rico. Weather Forecasting 12: 515–525.

Using results from a factor analysis regionalization of nontropical storm convective rainfall over the island of Puerto Rico, a statistical methodology is investigated for its potential to forecast rain events over limited areas. Island regionalization is performed on a 15-yr dataset, while the predictive model is derived from 3 yr of surface and rainfall data. The work is an initial attempt at improving objective guidance for operational rainfall forecasting in Puerto Rico. Surface data from two first-order stations are used as input to a partially adaptive classification tree to predict the occurrence of heavy rain. Results from a case study show that the methodology has skill above climatology—the leading contender in such cases. The algorithm also achieves skill over persistence. Comparisons of forecast skill with a linear discriminant analysis suggest that classification trees are an easier and more natural way to handle this kind of forecast problem. Synthesis of results confirms the notion that despite the very local nature of tropical convection, synoptic-scale disturbances are responsible for prepping the environment for rainfall. Generalizations of the findings and a discussion of a more realistic forecast setting in which to apply the technology for improving tropical rainfall forecasts are given.

Meteorological Impacts of Land Use Change in the Maritime Tropics

The island Puerto Rico is the smallest of the Greater Antilles. Measuring roughly 180 x 60 km, it is situated in the eastern Caribbean at 18o15’N and 66o30’W (figure 1.1). Apart from the coastal plains on the north and south coast, the island is mountainous, with the highest peaks in the central and north-eastern part of the island rising to elevations of 1000-1300 ma:s:l: (figure 1.2).
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