Fire and Smoke

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Fire and Smoke. How does fire affect climate? Forest fires, brush fires, and slash and burn agriculture are a significant force for environmental change, both locally and globally. Intentional deforestation by burning radically alters local landscapes.
Transcript
• Laboratory Experiment
• In addition to the output of and the distance from the energy source, surface
• type (surface reflectivity, specific heat, etc.) affect the absorption of incident
• radiation and how incident energy changes the temperature of a surface.
• In this lab you will examine the effect of various types of “surfaces” on the time
• rate of change of temperature of those surfaces when they are exposed to
• incident “sunlight”. Recall that an object’s change in temperature,T, is related
• to the object’s mass, M, the specific heat of the object, csh, and the energy the
• object absorbs and uses to change its temperature, E, i.e.,
• T = E / ( csh M ) .
• Surface reflectivity impacts the amount of incident radiation that is used to change the surface’s temperature, i.e., the surface’s reflectivity contributes to determiningE in the above relationship. For example, if the surface were highly reflective, then little of the incident radiation would be absorbed and used to warm the surface. Mathematically, we can express this relationship for a dry surface as
• E = (1 - Albedo ) * (Incident Radiation),
• where Albedo is defined as the fraction of incident energy that is reflected, i.e., albedo is the amount of electromagnetic energy reflected divided by the amount of incident energy.
• Fire and SmokeWhat are the local climate effects of a fire?Smoke and aerosol particles from fires can rise high into the troposphere and be carried long distances by the wind. Smoke plumes from Mexico have traveled as far north as Wisconsin and the Dakotas, and as far east as Florida and out over the Gulf Stream.Effects of aerosols represent one of the greatest uncertainties regarding climate change, both on global and regional scales. August 13, 2007http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17744http://earthobservatory.nasa.gov/Library/GlobalFire/fire_4.htmlAugust 13, 2007http://earthobservatory.nasa.gov/NaturalHazards/natural_hazards_v2.php3?img_id=14443Fire and SmokeWhat are the local climate effects of a fire?Scientists do not fully understand the magnitude of their cooling influence on climate. Scientists do not know which of the emission products exerts the greater net effect on regional and global climate—the cooling influence of aerosols and clouds, or the warming influence of the greenhouse gases. Because both types of emission products change rapidly through time and space, they are difficult to observe and characterize. In the future, the greenhouse gas warming is expected to dominate due to the gases' much longer presence in the atmosphere (10-100 yrs.) than that of aerosol particles (7 days).http://earthobservatory.nasa.gov/Library/GlobalFire/fire_4.htmlIncoming SolarRadiation 100% Total Albedo 30%6% Scatteredby Air4% Reflectedfrom Surface20% Reflectedby Clouds25% Direct3% Absorbedby Clouds16% Absorbedby Air 26% Diffuse51% Absorbed at theEarth's SurfaceFire and SmokeHow does smoke affect the solar radiation budget? Typically, the “direct effect” of most smoke is to increase the atmospheric reflectivity as compared to that which would have occurred without the aerosols.
• Note: If smoke, clouds or other aerosols increase the atmospheric albedo, then
• the percent of incoming
• will increase,
• - less energy will reach
• the Earth’s surface,
• - the surface will not get
• as warm.
• Fire and SmokeHow does smoke affect the solar radiation budget? (Con’t)However, soot or “black carbon” smoke, which is generated from traffic, industrial pollution, outdoor fires and household burning of coal and biomass fuels, behaves diffe
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