The Central American Smoke Event of May 1998 A Draft Summary Based on Reports and Data on the Web Rudolf B. Husar and Bret Schichtel

Central American Smoke Event Synopsis During a ten-day period, may 7-17, 1998, smoke from fires in central America drifted northward into the USA and Canada. The smoke caused exceedances of the PM standard, health alerts, and impairment of air traffic, as well as major reductions of visual range, and red sunsets. It was a major air pollution event covered by the research community as well as by the national media.

Background Throughout the spring of 1998, thousands of fires in Central America have been burning as it happens every spring but the 1998 fires are said to be about twice as intense as the normal year. Unlike earlier years, the research community has followed with keen interest the 1998 Central American fires by a variety of UV, visible and infrared remote sensors from satellites. This is summary of the Web-based data as augmented by surface- based PM10 monitoring data by state agencies This preliminary and incomplete but timely summary is intended for air quality managers and researchers interested in pursuing further detailed analysis of this unusual event.

Location of fires (red dots) on May 15, 1998, based on Defense Meteorological Satellite Program (DMSP) satellite dataDefense Meteorological Satellite Program (DMSP) NOAA’s Operational Significant Event Imagery (OSEI) Throughout the spring of 1998, thousands of fires in Central America have been burning with twice the intensity of normal springtime fires. Forest Fires over Central America

Smoke from the Central American Fires Based on SeaWiFS and other satellite imagery, thick smoke has been lingering over southern Mexico, Guatemala and Honduras and adjacent oceans throughout the spring season.SeaWiFS

Smoke passes over Eastern North America The episode began with stagnation over Central America on May 10, 11, and 12, On May 12, a remarkably thick pall of smoke has accumulated over the entire Gulf of Mexico and begun a swift journey to the north along the Mississippi Valley.May 12 By May 15, the smoke pall had stretched out from Central America Hudson Bay. Over the next two days the smoke pall was literally shoved eastward by an approaching cold front, resulting in a remarkable contrast of haziness (smokiness) in the front and behind the front.May 15 On May 17, virtually the entire Eastern Seaboard was blanketed by a pall of smoke.May 17

TOMS Aerosol Index GOES 8 Visible Imagery May 12May 14May 15May 16 Smoke passes over Eastern North America

GOES 8 View of the SmokeSeaWiFS View of the Smoke

May 2 May 3 May 5 May 6 May 4 May 7 May 8 May 9 May 10 May 11 May 12 May 13 May 14 May 15 May 16 May 17May 18 May 19 May 20 May 21 May 22 May 23May 24May 25 May 26May 27 May 28 May 29May 30 May 31 Daily TOMS images of absorbing aerosol indexTOMS

Goes 8 Visible ImageHY-SPLIT Trajectories HY-SPLIT Plumes TOMS Aerosol Index Comparison of HYSPLIT Predictions of airmass transport to GOES 8 and TOMS imagery

PM10 concentration over the Eastern U.S. during the smoke event The smoke drifted into the US and Canada and caused exceedances of the PM standard, health alerts, and impairment of air traffic due to thick haze.

Surface Haze-Ozone Map Comparison Surface haze maps show the north and eastward transport of smoke aerosol Regionally, the smoke does not appear to add ozone to the existing values Rather, ozone in the smoky airmass tends to be lower than their surroundings

Shadowband Sun Photometer (Slusser) About half of the total solar radiation is backscattered and absorbed by aerosols Angstrom exp. > 1.0 implies mean particle size < 0.5 um. Single Scatter Albedo < 0.8 indicates absorbing smoke

Science - Management Interaction Regarding the Central American Smoke Event The Asian dust and Central American fire events were keenly monitored by broad scientific community using multiple satellite and surface sensors. The available on-line data were catalogued and summarized on the web. The local air quality data along with regional summaries were used by air quality managers to issue health advisories. The regional summaries were used by the federal EPA to grant the states preliminary exemptions from air quality standard violations.

Summary Aerosols can be easily detected because they effectively scatter visible light from the sun. Space-based aerosol monitoring systems already exist to monitor the daily aerosol pattern globally. The remaining measurement can be resolved in the near future. The Asian Dust and Central American Smoke events have shown that air quality management can be effectively aided by timely scientific support.

We recommend the establishment of an internet-based aerosol watch system. A few experienced observers would monitor the daily aerosol pattern for interesting dust, smoke, or haze aerosol events. They would utilize the publicly available on-line satellite, surface monitoring, and meteorological modeling data. When an interesting event occurs, the relevant science and management communities would be alerted. Given the alert, the communities could initiate more intense monitoring and/or prepare the public for the developing risks. Recommendation: Aerosol Watch System

May 07 May 08 May 09 May 10 May 11 May 12 May 13 May 14 May 15 May 16 May 17 Extinction Coefficient (BEXT) from Surface Visibility- TOMS Overlay The color shades are BEXT, the black lines are the TOMS-based smoke outline

May 07 May 08 May 09 May 10 May 11 May 12 May 13 May 14 May 15 May 16 May 17 Daily Maximum Ozone and BEXT Overlay Color shades represent ozone. Black lines outline the smoke boundaries based on BEXT.