Rudolf Husar

1. Global Aerosols:Distribution of Dust, Smoke and Haze Based onSurface and Satellite ObservationsorAtmospheric Aerosols as Indicators of Global Biogeochemical Changes Rudolf Husar CAPITA, Washington University http://capita.wustl.edu/CAPITA/CapitaReports/MTAEloadas/NASALangley/NASALanagley/

2. The Living, Changing Earth The physical, chemical and biological state of the Earth’s environment is constantly changing due to aging, evolution andhuman 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.

3. Earth Science: Explaining the Change The basic elements of life including carbon, nitrogen, phosphorus, calcium are in constant circulation between the earth’s major environmental compartments: atmosphere, hydrosphere, lithosphere, and biosphere. Changes will occur if the circulation of the substances is perturbed, e.g. the CO2 has increased because the rate of carbon input is larger than the rate of output from the atmosphere.

4. Sensory-Motor Response to Changes The inevitable and unforeseeable environmental changes require response to these changes consisting of three steps: Sensing and recognition (monitoring) Reasoning and explaining (sciences) Decision making, action (management) All living organisms use this type of sensory-motor feedback to maintain their existence (sustainable development).

5. 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 signiture 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 monitoring systems already exist to monitor the daily aerosol pattern globally.

6. Major Biogeochemical Processes That Produce Aerosols Dust storms Fires Volcanoes Anthropogenic 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.

7. Satellite Detection of Aerosols Just like the human eye, satellite sensors detect the total amount of solar radiation that is reflected from the earth’s surface (Ro) and backscattered by the atmosphere from pure air, clouds and aerosols. Today, geo-synchronous and polar orbiting satellites can detect different aspects of aerosols over the globe daily.

8. Satellite Detection of Aerosols A simplified expression for the relative radiatioin detected by a satellite sensor (I/Io) is: I / Io = Ro e- + (1- e-) P where  is the aerosol optical thickness and P the angular light scattering probability.

9. 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.

10. 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.

11. 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.

12. The 1998 Asian Dust and the Central American Smoke Events • In the spring of 1998 two major tropospheric aerosol events occurred that illustrate the global/continental-scale transport, as well as: • The utility of satellites to detect and to track the aerosol clouds • The support of the scientific community to aid the air quality management on short notice.

13. 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.

14. 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.

15. 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.

16. 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.

17. 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. The fires produce a thick and rather uniform smoke layer of several thousand kilometer size. The prevailing wind transport the smoke across the Atlantic Ocean to South America. Occasionally, the savanna smoke and the Sahara dust clouds overlap. The main atmospheric removal mechanism of the smoke, dust, and haze is through clouds and precipitation.

18. 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.

19. Smoke from the Central American Fires Thick smoke has been lingering over southern Mexico, Guatemala and Honduras and adjacent oceans throughout the spring season.

20. 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.

21. SeaWiFS View of the Smoke GOES 8 View of the Smoke

22. A füstfelhő hatása US-ban • A füstfelhő útjában mindehol a megengedett érték feletti aeroszol koncentrációt okozott, és a levegő homályossága gátolta a légiforgalmat

23. 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).

24. Volcanic Aerosol Volcanic aerosols are composed of grayish volcanic ash which settles out within a day or less. The lasting volcanic aerosol (0.5-1 µm) is due to sulfuric acid that is formed in the stratosphere from the emitted SO2 gas

25. Volcanic emissions tend to spread out through both the northern and southern Hemisphere and reside in the troposphere for 1-2 years. Volcanic events are not influenced by human actions but they tend to mask out more subtle changes man-induced changes. History of volcanic aerosol optical depth, 1850-1900 shows sporadic events several times a century. By monitoring the pattern of volcanic aerosols one can determine the magnitude and spatial impact of volcanic events.

26. The Human Peturbation Human actions have also been altering some of the main natural biogeochemical processes. The enhaced intentional burning of forests has increased the flow of biological substances over many parts of the world. The spreading of deserts due to desertification is also likely to influence the flow of windblown dust.

27. Anthropogenic Fuel Combustion Since the last century human activities have significantly influenced the Earth’s biogeochemical balance. The combustion of fossil fuels, coal, oil and gas has liberated large quantities of carbon, sulfur, and trace metals from its long term lithospheric reservoir and transferred it to the atmosphere.. In North America, the per capita sulfur emission is 1/2 kg per day. This large quantity of mobilized sulfur not only pollutes the air, but after deposition may acidify the soil, and may harm the plants.

28. Central Europe India Anthropogenic Pollution China Eastern U.S.

29. Summary: Aerosols as Biogeochemical Indicators Aerosols are suitable indicators of dust movement, fire and smoke, volcanic emissions and anthropogenic fossil fuel combustion. Each source type has a unique signiture either in size distribution, chemical composition, or optical properties. 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.

30. GAW with GAIN An internet-based global aerosol watch (GAW) system could established alert the relevant science and management communities for interesting dust, smoke, or haze aerosol events and to provide Just-In-Time science. The communication could be conducted through a Global Aerosol Information Network (GAIN) that would connect the users and the producers of earth science data, information and knowledge. PRODUCERS USERS Biomass burning - biogeochemists Surface obs. GAIN Global Aerosol Information Network Aeolian dust - geologists Satellites Vulcanologists Radiative effects-Climate Change Human obs. Pollution monitoring- Control Offices

31. Acknowledgements Thanks to the spontaneous web-based virtual communities on Asian dust and Central American smoke for willingness to share raw data sets as an example for future spontaneous collaboration on global aerosols. This research was supported by the U.S. Environmental Protection Agency.