Climate of Mesoamerica and Caribbean Prepared by Adam Carpenter, based on research by Amy Huff, Battelle

Climate Overview Subtropical to tropical Rainfall 150cm (60in) to 380cm (150in) Dry and rainy seasons, based on the Intertropical Convergence Zone (ITCZ)

ITCZ Low pressure near the equator –NW and SE trade winds meeting Band of heavy precipitation Moves with the seasons

Seasons April to November: Rainy Season November to February: Transition Period February to April: Dry Season

El Niño Southern Oscillation (ENSO) Irregularly occurring global climate phenomenon every 2-7 years NE Trade Winds Reduced Dry Season Lengthened

La Niña Essentially opposite of El Niño Rainy season extended Higher rainfall may cause: –Flooding –Landslides –Runoff das.uwyo.edu/~geerts/cwx/ notes/chap12/lanina_walke r.gif

Wind and Hurricanes Wind is primarily easterly –Rainfall tends to be on Atlantic side of elevation Hurricane’s often form in the Atlantic –June 1 to November 30 is main season –Peaks in September du/essc_web/news/im ages/hurricane.jpg

Weather Characteristics In the Caribbean, often heavy rain in afternoon due to on-shore flow Wider temperature changes inland, both day-to-night and over the year

Regional Overview of Aerosol Optical Depth (AOD) for Mesoamerica and the Caribbean

AOD & PM Overview Aerosol Optical Depth (AOD) measures absorbed/reflected light by particulate matter (PM) Major PM sources –Local Agricultural Fires: April-May Peak –Smoke and Dust from Africa & South America: June-July Peak –Reduced PM during rainy season

January 2007 March 2007 February 2007 April 2007 May 2007 July 2007 June 2007 August 2007 September 2007 November 2007 October 2007 December 2007

General Guidelines: Interpreting Air Quality based on Meteorology

Main Components of AQ Concentration of Pollutants Factors that increase or decrease pollutants Air mass

Wind Speed and Direction High winds (>10mph, 5m/s) improve AQ Low winds allow buildup of pollutants Winds from cities and agriculture tend to be reduce AQ Winds from off shore or “clean areas” tend to improve AQ

Height of Boundary Layer and Vertical Mixing A higher boundary layer promotes better AQ: –More space for pollutants to dilute into Greater vertical mixing promotes better air quality –Pollutants more likely to move away from ground

Precipitation and Cloud Cover Cloud Cover tends to improve AQ: –Blocks sunlight which decreases Ozone Precipitation also tends to improve AQ: –Rain “grabs” pollutants in the air as it falls

Frontal Boundaries AQ poor ahead of cold fronts, good after it passes. Warm fronts tend to cause poor AQ, especially when they are slow moving

High and Low Pressure Systems High pressure systems tend to cause poor air quality because of: –Clear, sunny skies –Light winds and limited vertical mixing Low pressure systems tend to cause good air quality because of: –Reduce ozone with cloud cover –Reduce PM with heavy rain /docu/wx_cyclone2.gif