Global Aerosols: Distribution of Dust, Smoke and Haze Based on Surface and Satellite Observations or Atmospheric Aerosols as Indicators of Global Biogeochemical Changes Seminar presented at NASA Langley, March 23, 99 Rudolf Husar CAPITA, Washington University/ The Living, Changing Earth The physical, chemical and biological state of the Earths environment is constantly changing due to aging, evolution and human influences. Some of the changes occur slowly in a steady fashion and they are foreseeable. However, many bio-geochemical changes occur quickly, unexpectedly, and they unevenly distributed in space and time, sometimes causing catastrophic events. Earth Science: Explaining the Change The basic elements of life including carbon, nitrogen, phosphorus, calcium are in constant circulation between the earths major environmental compartments: atmosphere, hydrosphere, lithosphere, and biosphere. Changes will occur if the circulation of the substances is perturbed, e.g. the CO 2 has increased because the rate of carbon input is larger than the rate of output from the atmosphere. Sensory-Motor Response to Changes The inevitable and unforeseeable environmental changes require response to these changes consisting of three steps: All living organisms use this type of sensory-motor feedback to maintain their existence (sustainable development). Sensing and recognition (monitoring) Reasoning and explaining (sciences) Decision making, action (management) Major Biogeochemical Processes Visualized by Aerosols Dust storms VolcanoesAnthropogenic pollution These processes are producing visible aerosols in form of dust, smoke, and haze. The quantity and spatial-temporal distribution of dust and smoke and haze can be used to characterize the flow of substances through the atmosphere. Fires Aerosols as Indicators of Global Biogeochemical Changes Aerosols are suitable indicators of dust movement, fire and smoke, volcanic emissions and anthropogenic fossil fuel combustion. Each source type has a unique signature either in size distribution, chemical composition, or optical properties. Aerosols can be easily detected because they effectively scatter visible light from the sun. Space and surface-based aerosol sensors already exist to monitor the daily aerosol pattern globally Just like the human eye, satellite sensors detect the total amount of solar radiation that is reflected from the earths surface (R o ) and backscattered by the atmosphere from pure air, clouds and aerosols. Satellite Detection of Aerosols Today, geo-synchronous and polar orbiting satellites can detect different aspects of aerosols over the globe daily. A simplified expression for the relative radiatioin detected by a satellite sensor (I/I o ) is: I / I o = R o e - + (1- e - ) P Satellite Detection of Aerosols where is the aerosol optical thickness and P the angular light scattering probability. Dust Storms Dust storms transport Aeolian dust from one part of the Earth to another. Loess, the fertile silty yellowish brown soil, covers about 10% of the land surface of the Earth. In China, for example, 100 meter deep layers of loess are found. The source areas of loess are the hot and temperate deserts. The dust particles are removed from the surface of sand dunes by the force of the wind. The chemical composition of the dust is similar to the composition of the sand. The smaller dust particles in the size range 1-5 mm are transported several thousand kilometers from their source. Sahara dust can be found in South America and East Asian dust over North America and Greenland. Sahara Dust Over West Africa Monitoring the atmospheric dust concentration and flow allows the estimation of the dust transport, drought conditions, desertification and other changes over arid regions. The Asian Dust Event of April 1998 On April 15th, 1998 an unusually intense dust storm began in the western China, just in time for the east Asian dust season. CNN reported that 12 people were missing in the storm. By the April 20th, the elongated dust cloud covered a 1000 mile stretch of the east coast of China. Transport over Pacific The dust cloud was traversing Pacific in five days. It appeared as a yellow dye on color SeaWiFS satellite images visualizing its own path across the Pacific. Impact of Asian Dust on North America By April 27th, the dust cloud rolled into North America. Satellite images show that one branch of the dust plume was heading southward along the California coast and another branch continued eastward across the Canadian Rockies. During the dust event the PM10 and PM2.5 concentrations in Washington state reached 120 and 40 mg/m3, respectively. Science Support to Air Quality Management A few scientists were monitoring Asian dust event. As the Asian dust approached the Pacific Coast of North America, air quality managers and other scientists were alerted. Within two days, over 40 scientists and managers have reported their observations and preliminary data on the web. The air quality managers used the science website to inform the public. Fires Vegetation fires are important to the ecology of many terrestrial systems because they cycle many trace elements. Fires are also major sources of atmospheric trace gases and aerosols. Nowadays vegetation fires are initiated mostly by humans for land clearing, agricultural harvest clearing, savanna burning for nomadic agriculture. Over the sub-Sahara savanna region has thousands of small fires every year in the December-February season. Smoke from Biomass Burning The monitoring of smoke aerosol from forest, grass, and agricultural fires can reveal the location, magnitude, and seasonality of biomass burning. Smoke plumes are visible over 1000s km. Occasionally, the savanna smoke and the Sahara dust plumes overlap. Forest Fires over Central America Throughout the spring of 1998, thousands of fires in Central America have been burning with twice the intensity of normal springtime fires. Smoke from the Central American Fires Thick smoke has been lingering over southern Mexico, Guatemala and Honduras and adjacent oceans throughout the spring season. Smoke passes over Eastern North America 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. 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. On May 17, virtually the entire Eastern Seaboard was blanketed by a pall of smoke.May 12May 15May 17 SeaWiFS View of the Smoke GOES 8 View of the Smoke A fstfelh hatsa US-ban A fstfelh tjban mindehol a megengedett rtk feletti aeroszol koncentrcit okozott, s a leveg homlyossga gtolta a lgiforgalmat Science - Management Interaction Regarding the Central American Smoke Event The Central American fires have been keenly monitored by broad scientific community using multiple satellite 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 exemptions from air quality standard violations. The Asian dust and the Central American smoke event has clearly demonstrated that the available current space-based aerosol monitoring data can enable virtual communities of scientists and managers to detect and follow major aerosol events and to support air quality management through JITERS (Just In Time Environmentally Relevant Science). GAIN Global Aerosol Information Network Biomass burning - biogeochemists Vulcanologists Radiative effects-Climate Change Pollution monitoring- AQ Managt. Aeolian dust - geologists GAW with GAIN An internet-based Global Aerosol Watch (GAW) system could alert relevant science and management communities for interesting dust, smoke, or haze aerosol events. A Global Aerosol Information Network (GAIN) could connect the producers and the consumers of earth science data, information and knowledge and provide just in time science support to the community. Surface data Satellites Human obs. PRODUCERSINFORMATION USERS Disaster Relief - Crisis Management Acknowledgements Thanks to the web-based virtual communities on Asian dust and Central American smoke for their willingness to share raw data as an example for future spontaneous collaboration. This research was supported by the U.S. Environmental Protection Agency.