Although extensive areas of forests and grasslands are burned in the tropics, relatively little scientific attention has been focused on this phenomenon. In order to determine the land area burned and estimate the charcoal (elemental or graphitic carbon) produced, I monitored agricultural burning in a 1145 km 2 area in central Panama during the 1981 dry season. Over 10% of the land surface was burned in that year. Charcoal concentrations in the aerosol were also measured and reached values of 3.1 ~gC/m 3 during the peak in burning. Off-peak values of aerosol charcoal are less than 1 ~tgC/m 3. The high charcoal concentration reflects the massive amounts of vegetational burning occurring in the area.
The charcoal advected by the air mass flowing over the area has been estimated using a box model. Assuming an average aerosol concentration of charcoal of 1 ~tgC/m 3 for a three-month burning period, a 2 km atmospheric mixed layer, a 14 km/h wind velocity to the south, and a 150 km wide zone across the western Gulf of Panama watershed, I estimate that, during the dry season, 9 Γ 10 9 g charcoal are mobilized by the troposphere, if 4.1 Γ 1012 g phytomass are annually burned in this region, then the charcoal emission factor to the troposphere is 2.2 Γ 10 -3 .