Polar meteorology: understanding impacts in the Tropics

This talk summarizes the current scientific understanding of polar weather and climate.

Abstract

There is currently a very low understanding of the weather and climate at the poles due to limited observations. However, from what is available, we know that the impact of climate at the poles is felt globally. This is confirmed by past climates. Thus it is necessary to understand what the impacts of varying climates at the poles means at various locations globally. Topics like the melting ice sheets at the poles and its impacts on water, tourism and agriculture sectors in the Caribbean region are dealt with in this talk.

Late season rainfall over Barbados and the southeast Caribbean: November 2004

This talk summarizes the meteorological events of November 2004 which lead to large totals of rainfall being recorded for the month.

Abstract

November is a transitional month between the ‘wet’ and ‘dry’ weather patterns over the tropics. Over the Caribbean it is more traditionally seen as the end of the hurricane season and to some extent the end of the rainy season. However, there have been years when rainfall events in the November over the Southeastern Caribbean have produced record rainfall and resultant severe flood events in many of the islands. November 2004 was such an occasion. The rainfall amounts recorded at the Caribbean Institute for Meteorology and Hydrology for the month was more than twice that recorded in any other month of 2004. Was this event an anomaly? What were the conditions which lead to such an event?

This study examines the rainfall events over Barbados and the Southern Eastern Caribbean in November, 2004. Most of the more common features that affect the region came into play, from the ITCZ to upper level troughs, which appeared to have the major impact oven the region. While not the instigator of unstable weather, upper troughs do enhance and sustain convection over prolonged periods, and can make the difference between a dry and wet month depending on the position the trough relative to the Caribbean islands. The results were deadly and devastating. Barbados experience floods which caused havoc on the roads, closed schools and businesses, while mud slides killed one in Tobago and caused damage that rivaled that of Hurricane Ivan earlier in that year.

The use of the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) for predicting severe weather

This talk assesses the ability of the MM5 to model severe weather in the Caribbean region. The event modeled was Tropical Storm Ernesto and Tropical Storm Debbie which formed in the 2006 Atlantic Hurricane season.

Radar rainfall and hydrologic modeling

This talk explains the principle use of radar in hydrology is to measure aerial precipitation. It highlights the value of radar measured rainfall towards the improvement in performance of hydrologic models and touches on the possible integration of the practice into flood warning systems throughout the Caribbean.

Abstract

The Cambridge Advance Learner’s Dictionary defines radar as “a system which uses radio waves to find the position of objects which cannot be seen”. Radar is capable of measuring patterns of rainfall not only in space, but also over time. The principle use of radar in hydrology is to estimate aerial precipitation. Atmospheric conditions between the radar and the target affect the efficiency with which precipitation returns energy back to the radar. Backscattering and absorption of the radar signal by the raindrops in the intervening atmosphere attenuate the signal strength, making accurate rainfall rate estimation difficult. The radar equation (Probert-Jones) relates received radar-measured power to reflectivity. Reflectivity-rainfall rate relationships (Z-R relationships) can be derived for different storm types. These Z-R relationships are subject to random and systematic errors, compromising the accuracy of rainfall rate estimates. However, radar rainfall improves the estimation of rainfall between rain gauges. It provides coverage over large areas at a high spatial resolution and can be ingested directly by conceptual distributed hydrologic models. Most hydrologic and water resource models are equipped to handle basin average rainfall. Radar rainfall improves model performance and can provide timely inputs to flood warning systems throughout the Caribbean.