AT 737 Aerosols Importance of Aerosols directly change

AT 737 Aerosols

Importance of Aerosols directly change the radiation budget Aerosols modify cloud properties (and clouds modify aerosol properties) Aerosols affect atmospheric chemistry Aerosols affect biological systems, including human health AT 737 Aerosols 2

Characteristics of Aerosols • Sizes range from 0. 01 to 10 or more micrometers • Chemical composition: NOTE: VERY CHEMICALLY HETEROGENEOUS ”PHYSICS OF DIRT” o Sulfate (SO 4) o Nitrate o Soil and mineral dust (silicates, clays) o Carbonaceous compounds (elemental and organic carbon) o Sea-salt (Na. Cl) SOURCE (of this and next four slides): Dr. Bill Collins, NCAR AT 737 Aerosols 3

Sources Sulfate: n n Oxidation of sulfur dioxide from fossil fuel burning Oxidation of DMS released from ocean micro-organisms Volcanic emissions Manmade now 4 times natural (IPCC time series) Nitrate: n Combustion Soil and mineral dust: n n Dry lake beds from prehistoric lakes Desertification Carbonaceous compounds n n Organic compounds released from forests Natural biomass burning Anthropogenic biomass burning Fossil fuel combustion Sea-salt: oceans, of course AT 737 Aerosols 4

Sinks Lifetime in the atmosphere: about 5 -7 days. Stratosphere: x 100 Removal mechanisms: n Sedimentation (settling) – about 10 -20% by mass w w n V = 50 cm/s for large silicates (50 microns) V =0. 03 cm/s for small particles (1 micron) “Scavenging” by precipitation – about 80 -90% by mass Consequence: aerosol is very uniformly mixed AT 737 Aerosols 5

Properties of Atmospheric Aerosols Type Altitude (km) Horiz scale (km) Freq. Composition Mass loading (mg m− 3) Optical depth Mean particle Size Trop. Aerosols 0 -10 10000 1 Sulfate, nitrate, minerals 0. 01 to 1 ~0. 1 -1 Dust storms 0 -3 10 -1000 Sporadic Silicates, clays <1 to 100 1 -10 Volcanic 5 -35 10000 Sporadic Mineral ash, sulfates <1 to 1000 0. 1 to 10 Smoke 0 -10 1 -100 Sporadic Soot, ash, tars 0. 1 t 1 0. 1 to 10 0. 1 to 1 AT 737 Aerosols 6

Types of Aerosol Continental: sulfate, nitrate, carbonaceous, mineral Marine: sea salt Stratospheric: e. g. , sulfate formed from volcanic eruptions AT 737 Aerosols 7

Aerosol Variablility Size spectrum Composition Number density Makes remote sensing difficult, perhaps more difficult than sensing clouds AT 737 Aerosols 8

Stratospheric Aerosols Stratospheric aerosols are few in number The long path length of limb sounding is useful AT 737 Aerosols 9

Solar Occultation Measures transmittance of solar radiation as a function of tangent height Self calibrating AT 737 Aerosols 10

Abel’s Equation Very peaky weighing functions AT 737 Aerosols 11

Corrections Need to correct for Rayleigh scattering and atmospheric gas absorption AT 737 Aerosols 12

Results AT 737 Aerosols 13

Tropospheric Aerosols If you can see them you can measure them, right? MODIS truecolor 12/17/04 05: 20 UTC AT 737 Aerosols 14

Another Example Note land/ocean differences! MODIS truecolor 3/10/07 AT 737 Aerosols 15

Processes Aerosols scatter solar radiation toward satellite Depends on aerosol properties as well as optical depth AT 737 Aerosols 16

NOAA POES AOD SOURCE: http: //www. osdpd. noaa. gov/PSB/EPS/Aerosol. html AT 737 Aerosols 17

NOAA GOES AOD SOURCE: http: //www. orbit. nesdis. noaa. gov/smcd/emb/GASP/Real. Time. html AT 737 Aerosols 18

Good Paper King et al. , 1999: Remote sensing of tropospheric aerosols from space: Past, present, and future. BAMS, 80, 2229 -2259. “Reflectance Function” AT 737 Aerosols 19

Aerosols Over Land AT 737 Aerosols 20

Color Ratio Angstrom exponent AT 737 Aerosols 21

Forecasts of Aerosols http: //www. nrlmry. navy. mil/aerosol_web/loop_html/glo baer_world_loop. html AT 737 Aerosols 22

National Park Service http: //www. cira. colostate. edu/nps. html AT 737 Aerosols 23

CALIPSO Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) http: //www-calipso. larc. nasa. gov/ 532 nm Backscatter AT 737 Aerosols 24