A. Anthony Chen

Stochastic simulation and forecasting of hourly average wind speed sequences in Jamaica

Abstract Stochastic simulation and forecast models of hourly average wind speeds are presented in this paper. The models take into account several basic features of wind speed data including autocorrelation, non-Gaussian distribution, and diurnal nonstationarity. The positive correlation between consecutive wind speed observations is taken into account by fitting an autoregressive moving average (ARMA) process to wind speed data which were transformed to make their distribution approximately Gaussian and standardized to remove diurnal nonstationarity. Based on three years of data, separate models were obtained for the months of June, July, and August. Tests were performed to verify the adequacy of the models and comparisons were made between generated and real series and between forecasted and real series to check if the wind speed behaviour was faithfully reproduced. Good results were obtained.

Climate Change and the Caribbean: Review and Response

Caribbean economies, lifestyles, activities, practices and operational cycles are intricately linked to climate, making them vulnerable to its variations and/or changes. As examples, climate extremes impact agriculture, fisheries, health, tourism, water availability, recreation, and energy usage, among other things. There is however limited incorporation of climate information in the long term developmental plans and policies of the region. This is in part due to a knowledge deficit about climate change, it’s likely manifestation in the region and the possible impact on Caribbean societies. In this paper, a review of the growing bank of knowledge about Caribbean climate science; variability and change is undertaken. Insight is offered into the basic science of climate change, past trends and future projections for Caribbean climate, and the possible implications for the region. In the end a case is made for a greater response to the threats posed by climate change on the basis of the sufficiency of our current knowledge of Caribbean climate science. A general profile of what the response may look like is also offered.

Wind power in Jamaica

Parameters to evaluate the potential for using wind energy to generate electricity in Jamaica were obtained. These include the average wind power scaled to a height of 20 m at existing weather stations and temporary anemometer sites, the variation in annual and monthly wind power, and the frequency distribution of wind speed and wind energy available. Four small commercial turbines were assumed to be operating at some of the sites, and the estimated energy captured by them, the time they operated above their cut-in speed and their capacity factors were also determined. Diurnal variations of wind speed and prevailing wind directions are discussed and a map showing wind power at various sites was produced. Two stations with long-term averages, Manley and Morant Point, gave results which warranted further investigation. Results from some temporary stations are also encouraging. Mean wind speeds at two other sites in the Caribbean are given for comparison. A method for estimating the power exponent for scaling the wind speed from climatic data is described in Appendix 2.

Estimating daytime latent heat flux and evapotranspiration in Jamaica

The suitability of the two-parameter scheme of De Bruin and Holtslag (1982) to estimate daytime latent heat flux and evapotranspiration in Jamaica was examined using meteorological data collected over fields of short grass. The study covered three different periods, January to February of 1994, January to February of 1990, and August to September of 1989. The fields were irrigated regularly (three times a week) to provide enough water to evaporate. The daytime (07:00‐18:00 hours) 20 min and hourly latent heat flux values, average evaporation for the earlier mentioned three periods and evaporation on individual days were estimated using De Bruin and Holtslag scheme for two situations. One was with the parameter 0 D0.95 andD20 W m 2 and the other was with 0 D1.05 andD20 W m 2 . The analysis of the latent heat flux and evaporation led to the following results. (i) The values of latent heat flux and evaporation estimated using 0 D0.95 andD20 W m 2 compare well with the corresponding measured values for time steps of the order of 20 min to several days. (ii) The level of agreement between estimated and measured hourly values of latent heat flux seen in our work was very close to that reported in the study of De Bruin and Holtslag, implying the consistency of the skill of that scheme at higher average latent heat flux levels in Jamaica. (iii) The choice of 1.05 for 0 applies better for our data. These results indicate that the scheme of De Bruin and Holtslag with 0 D0.95 andD20 W m 2 can satisfactorily be used to estimate daytime latent heat flux and evaporation from well watered grass surfaces in regions having environmental conditions similar to those encountered in Jamaica, but appears better with 0 D1.05.

Solar radiation in Jamaica

Average monthly global radiation in Jamaica was calculated for the years between 1978 and 1987 from values measured at 12 stations and from Angstrom-coefficient derived values. From these values daily global radiation was estimated for various periods at grid points separated by approximately 10 km on a square. Three dimensional plots and contour maps for the various periods were produced. The interpolation was based on kriging adopted by Hay (1986). A relationship between global and diffuse radiation based on the Liu and Jordan (1960) relationship was obtained. The errors in the interpolated annual values were less than 10%. The maps were made available to the public with suggested usages of solar energy. Diffuse radiation formed less than 50% of the total radiation.

Determination of the orientation of ionospheric irregularities causing scintillation of signals from earth satellites

Abstract Data obtained from spaced receiver measurements made at Kingston, Jamaica, show that the irregularities causing the scintillation of signals from earth satellites are closely aligned along the magnetic field lines in the F-region. The method of determining the orientation of the irregularities in the ionosphere and the results are summarized.

The Climate Studies Group Mona

Introduction The Climate Studies Group Mona (CSGM) was launched in 1994, in the Department of Physics, the University of the West Indies, Mona campus. The initiative was set in motion by Professor the Honourable A. Anthony Chen, O. M., Professor of Applied Physics. During the formative years we were given valuable assistance from by the Centre for Ocean Land Atmosphere Studies (COLA), the Inter American Institute (IAI) for A Global Change Research and The University of the West Indies Research Fellowship Programme. The group, which now comprises lecturers, postgraduate and undergraduate students, and associate members (former students), has made significant contributions to the study of Caribbean climate. These include, identifying atmospheric and oceanic influences on our climate, investigating climate change and its impact, isolating the relation between climate and crop yield for sugar cane, climate and incidences of dengue fever outbreak, and investigating renewable energy prospects for Jamaica. This article outlines the work of the CSGM and its significance in a local, regional and international context. Mission At its inception, the primary aim of CSGM was to learn the techniques of dynamic modelling of climate by numerical models. Since then, however, the groups activities have expanded to include applications of climate prediction, projections of regional climate change, and prospecting for alternative energy resources as a means of reducing energy costs and greenhouse gas emissions. Therefore the mission of the CSGM is as follows: * To investigate and understand the mechanisms responsible for a) the mean climate and b) extremes in climate in both Jamaica and the wider Caribbean; * To use this understanding to predict climate on a seasonal and annual basis; * To promote awareness of global warming and to determine how anthropogenic climate change will manifest itself in the Caribbean region; * To investigate the potential for exploiting renewable energy resources; and * To investigate and promote the advantageous uses of climate prediction in socio-economic sectors Pioneering Work Over the last 14 years, the CSGM has been involved in ground-breaking research that has resulted in significant contributions to atmospheric science and society. These include: * The mapping of the average solar radiation available to Jamaica, the results of which highlight the strong prospects of solar photovoltaics applications. * The modelling of wind speed and power across Jamaica, thereby identifying regions with good potential for utility-scale wind power. * Identifying an increase in early season (May-July) rainfall amounts in the year following the onset of an El Nino event. This is in contrast to the amplified dryness over the Caribbean frequently reported in literature in relation to the onset of El Nino. * Elucidating the impact of meteorological drought on sugar cane productions. * Clarifying the role of both the Atlantic and Pacific Oceans in modulating seasonal rainfall over the Caribbean and adjacent Caribbean regions. * The issuing of seasonal Precipitation Outlooks for Jamaica, made possible by the creation of statistical models for the early (May- July) and late (August-October) rainfall seasons for the Caribbean and mid-dry season (January-February) rainfall for the eastern Caribbean and Jamaica. * Proposing the atmospheric circulation patterns that facilitate the rainfall gradient pattern evident during the dry season (November- April) for the mature El Nino. It was found that the gradient pattern involved higher than normal rainfall over the northern Caribbean (north of 20°) and below normal over the southern Caribbean in relation to El Nino. * Identifying the evidence of climate change over the Caribbean particularly with respect to temperature. * The development of a Caribbean Climate Interactive Database. …