Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Tuesday November 18, 1997
April is one of the dry season months in Costa Rica and the rest of Central America with the region being influenced by a subtropical ridge, bringing drier weather and predominantly easterly trade winds. This is a time when burning of the fields in preparation for new crops is common.
In the 3.9/10.7 difference product, fires stand out as bright white spots and are identified digitally by large brightness counts. Figure 1 is a composite of maximum brightness counts for 2015 UTC covering April 1-30, 1997. As can be seen in this image, there are many regions in Honduras, Nicaragua and Panama and a few regions in Costa Rica and Columbia that saw fire activity at 2015 UTC throughout the month of April. For a fire to be 'picked up' in this composite, it has only to be detected once during the entire month. While most of the fires may be a result of intentional burning, some of the fires are accidental. Two accidental fires occurred between April 13 and 17 in the Guanacaste National Park in northwest Costa Rica.
Figure 2 shows the composite of minimum radiance (coldest temperatures) and Figure 3 shows the average radiance for the same time and period for 10.7 micrometer imagery. The color table on the minimum radiance composite uses blue, green, red and yellow to highlight the coldest temperatures (-30 C to -80 C), while the color table on the average radiance uses blue and green to highlight temperatures below freezing, and grey, orange and red to highlight temperatures above freezing. These composites indicate relatively little deep convection over the region at 2015 UTC for the month of April and confirm the dry weather occurring over the region. Compare these average and minimum radiance composites with those derived for the first the first two weeks in June 1997 during the wet season.