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.

Effects of forest re-growth, urban expansion, and climate variability on water quality in a tropical landscape

PowerPoint: Watershed protection as an ecosystem service? “Forests are assumed to be economically important for preventing soil erosion and flooding, protecting the water supply, and maintaining rainfall patterns. These assertion are often made with little supporting evidence.…First, benefits must be computed relative to an alternative land use. Second, benefit levels are highly location-specific and scale dependent”.

Urban heat island effect analysis for San Juan, Puerto Rico

Velazquez-Lozada, A., Gonzalez, J. E., and Winter, A., 2006. Urban heat island effect analysis in San Juan,
Puerto Rico. Atmospheric Environment 40, 1731-1741.

A climatological analysis of the differences of air temperature between rural and urban areas (dT(U–R)) corroborates the existence of an urban heat island (UHI) in the tropical coastal city of San Juan, Puerto Rico that has been increasing at a rate of 0.06 1Cyear1 for the last 40 years with predicted differences as high as 8 1C for the year 2050. The Regional Atmospheric Model System (RAMS) was used to validate the presence of this UHI and to simulate and compare three different land use scenarios consisting of potential natural vegetation, present, and projected future to quantify the impact of the urban development in the regional climate of Puerto Rico. RAMS simulated the UHI conditions at the lower and upper atmosphere revealing significant changes in sensible heat fluxes and sinks, and an increasing low turbulent-kineticenergy zone (LTKEZ) over the urbanized area of San Juan.


The Hydrometeorological Design Studies Center (HDSC), Hydrology Laboratory, Office of Hydrologic Development, U.S. National Weather Service is updating its precipitation frequency analysis for Puerto Rico and the Virgin Islands. Current precipitation frequency studies for the area are contained in Technical Paper No. 42 "Generalized estimates of probable maximum precipitation and rainfall-frequency data for Puerto Rico and Virgin Islands" (U.S. Weather Bureau 1961) and Technical Paper No. 53 "Two- to ten-day rainfall for return periods of 2 to 100 years in Puerto Rico and Virgin Islands" (Miller 1965). The current study includes collecting data and performing quality control, compiling and formatting datasets for analyses, selecting applicable frequency distributions and fitting techniques, analyzing data, mapping and preparing reports and other documentation. The study will determine annual and seasonal precipitation frequencies for durations from 5 minutes to 60 days, for return periods from 2 to 1000 years. The study will review and process all available rainfall data for the Puerto Rico and Virgin Island study area and use accepted statistical methods. The study results will be published as a Volume of NOAA Atlas 14. They will also be made available on the internet using web pages with the additional ability to download digital files.

Wind characteristics on the Caribbean island of Puerto Rico

Altaii, K. and R.N. Farrugia (2003), “Wind characteristics on the Caribbean island of Puerto
Rico”, Renewable Energy, 2003. 28(11): 1701-1710.

Wind data was measured at a number of sites on the Caribbean island of Puerto Rico over a 24 calendar-month time frame. The wind data gathered at four sites is envisaged to shed new light on the wind characteristics of this tropical island with an emphasis on the climate’s suitability for wind energy technology applications. Characteristics such as the diurnal, monthly and annual wind speed are subjectively investigated to determine the sites’ potential for further studies in the wind measurement field. Reasonable wind conditions for wind energy conversion system installation seem to exist in and around Aguadilla and Ponce.

Urban Heat Islands Developing in Coastal Tropical Cities

Gonza´lez, J. E., C. Luvall, D. Rickman, D. Comarazamy, A. Picon,
E. Harmsen, H. Parsiani, N. Va´squez, R. Williams, and R. W. Waide
(2005), Urban heat islands developing in coastal tropical cities, Eos
Trans. AGU, 86(42), 397, doi:10.1029/2005EO420001.

Beautiful and breezy cities on small tropical islands, it turns out, may not be exempt from the same local climate change effects and urban heat island effects seen in large continental cities such as Los Angeles or Mexico City. A surprising, recent discovery indicates that this is the case for San Juan, Puerto Rico, a relatively affluent coastal tropical city of about two million inhabitants that is spreading rapidly into the once-rural areas around it. A recent climatological analysis of the surface temperature of the city has revealed that the local temperature has been increasing over the neighboring vegetated areas at a rate of 0.06°C per year for the past 30 years.This is a trend that may be comparable to climate changes induced by global warming. These results encouraged the planning and execution of an intense field campaign in February 2004, referred to as the San Juan Atlas Mission, to verify the spatial and temporal extent of this urban heat index. Results of this field campaign recently have been analyzed and are the main topic of this article. These results reveal the warming of a tropical coastal city that is significantly higher than typical temperatures in vegetated areas.This may be the first set of high-resolution thermal images taken in a tropical coastal city. Figure 1 shows that the daytime surface temperatures of a portion of San Juan at fi ve-meter resolution are as high as 60°C,and that differences between urbanized and limited vegetation areas are in excess of 30°C.

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.

Harmonic and Simple Kriging Analyses of Diurnal Precipitation Patterns in Puerto Rico

Sen-Roy S, Balling JrRV:
"Harmonic and Simple Kriging Analyses of Diurnal Precipitation Patterns in Puerto Rico",
Caribbean Journal of Science 41 (2) : 181-188 (Aug 2005)

ABSTRACT.—Relatively large, topographically complex tropical islands can produce diurnal precipitation patterns that vary considerably over relatively short distances. In this investigation, we assembled a variety of databases to analyze diurnal rainfall patterns in Puerto Rico. We found strong diurnal cycles for all parts of the island with times of maximum frequency or total that ranged from pre-dawn in the east to midafternoon in the west. The pattern is similar to findings from Hawaii, and appears related to the daily pattern of katabatic and anabatic winds interaction with the predominant easterly trade winds. The diurnal pattern in rainfall was consistent through the year and not significantly affected by local sea-surface temperatures, El Niño-Southern Oscillation, and/or the North Atlantic Oscillation.

Climate influence on dengue epidemics in Puerto Rico

Jury, M., 2008: Climate influences on dengue epidemics in Puerto
Rico. Int. J. Environ. Health Res., 18, 323–334.

The variability of the insect-borne disease dengue in Puerto Rico was studied in relation to climatic variables in the period 1979–2005. Annual and monthly reported dengue cases were compared with precipitation and temperature data. Results show that the incidence of dengue in Puerto Rico was relatively constant over time despite global warming, possibly due to the offsetting effects of declining rainfall, improving health care and little change in population. Seasonal fluctuations of dengue were driven by rainfall increases from May to November. Year-to-year variability in dengue cases was positively related to temperature, but only weakly associated with local rainfall and an index of El Nin˜ o Southern Oscillation (ENSO). Climatic conditions were mapped with respect to dengue cases and patterns in high and low years were compared. During epidemics, a low pressure system east of Florida draws warm humid air over the northwestern Caribbean. Long-term trends in past observed and future projected rainfall and temperatures were studied. Rainfall has declined slowly, but temperatures in the Caribbean are rising with the influence of global warming. Thus, dengue may increase in the future, and it will be necessary to anticipate dengue epidemics using climate forecasts, to reduce adverse health impacts.

Paleoclimate proxy perspective on Caribbean climate since the year 1751: Evidence of cooler temperatures and multidecadal variability

Kilbourne, K. H., T. M. Quinn, R. Webb, T. Guilderson, J. Nyberg, and A. Winter (2008), Paleoclimate proxy perspective
on Caribbean climate since the year 1751: Evidence of cooler temperatures and multidecadal variability, Paleoceanography, 23,
PA3220, doi:10.1029/2008PA001598.

Annually resolved coral delta O-18 and Sr/Ca records from southwestern Puerto Rico are used to investigate Caribbean climate variability between 1751 and 2004 C. E. Mean surface ocean temperatures in this region have increased steadily by about 2 degrees C since the year 1751, with Sr/Ca data indicating 2.1 +/- 0.8 degrees C and delta O-18 data indicating 2.7 +/- 0.5 degrees C. Coral geochemical records from across the tropics demonstrate that regional variability is important for understanding climate variations at centennial time scales. A strong multidecadal salinity signal in the oxygen isotope data correlates with observed multidecadal temperature variations in the Northern Hemisphere. Instrumental wind and precipitation data indicate that the most recent coral isotopic variations are caused by expansion and contraction of the steep regional salinity gradient, forced by trade wind anomalies through meridional Ekman transport. The timing of the fluctuations suggests that the multidecadal-scale wind and surface circulation anomalies might play a role in Atlantic temperature variability and meridional overturning circulation, but further work is needed to confirm this suggestion.
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