Aerosol: a dispersion of microscopic solid or liquid particles in a gaseous medium, such as smoke and fog
Aerosol Light Extinction (Bep): The attenuation of light due to scattering and absorption of aerosols. According to the old IMPROVE algorithm, extinction is calculated according to the following equation:
Bep = 3F(RH)[Sulfate] + 3F(RH)[Nitrate] + 4[OMC] + 10[LAC] + 1[Soil] + 0.6[CM]
In the following table the brackets [ ] denote concentrations of that chemical species.
AIRS: The EPA Aerometric Information Retrieval System
ASOS: Automated Surface Observation System
BIA: Bureau of Indian Affairs
BLM: Bureau of Land Management
CASTNET: Clean Air Status and Trends network
CENRAP: Central Regional Air Planning organization
CM: Abbreviation for coarse mass. This is defined as the difference in mass of the PM10 fraction minus the fine fraction or PM2.5.
CMB: Chemical Mass Balance receptor model
Conditional Probability: The conditional probability typically is the fraction of backtrajectories for which when air passed over a given area it met some condition (i.e. within 20% worst haze. What we have plotted here is the percent residence time over an area for worst sulfate, etc. days divided by the average residence time over an area. Values greater than 1 indicate more transport than average for the given condition (e.g. worst sulfate); values less than 1 indicate less frequent than average transport over an area during those conditions.
COOP: National Weather Service Cooperative Observation station. This is a network of surface meteorological observations stations in the US for the collection of daily maximum and minimum temperatures, precipitation and sometimes snow fall.
Benefit: Under many circumstances a change in one deciview will be perceived to be the same on clear and hazy days.
Drawback: Deciview is not easily related to gaseous and aerosol concentrations
DV = 10*ln(Bext/10)
EDAS: Eta Data Assimilation model system. This is the primary meteorological data input to the HYSPLIT trajectory model used in the Causes of Haze Assessment. For the years 1997 to April 2004 we used the 80-km resolution dataset. From May 2004 to the present we use the 40-km version that is available from the NOAA Air Resource Laboratory's ftp site.
Emission Inventory: An emission inventory is a database of air emissions information with input from numerous State and local air agencies, tribes, and from industry. This database contains information on stationary and mobile sources that emit criteria air pollutants and their precursors, as well as hazardous air pollutants (HAPs). The database includes estimates of annual emissions, by source, of air pollutants on an annual basis. Emissions Inventories are the basis for numerous efforts including trends analysis, regional, and local scale air quality modeling, regulatory impact assessments, and human exposure modeling.
FCIA: Federal class I Area
FWS: US Fish & Wildlife Service
GIS: Geographic Information System
Great Basin High:
IMPROVE: Interagency Monitoring of PROtected Visual Environments
IMPROVE protocol: Interagency Monitoring of PROtected Visual Environments
Incremental Probability: Also called residence time difference. Residence time difference maps give the percent residence time for some condition (e.g. high sulfate) minus the percent residence time for all conditions ( i.e. average residence time).
Light Absorbing Carbon or LAC:
Light Absorbing Carbon or LAC:
Units: inverse distance, e.g. inverse mega meters (Mm-1)
Benefit: Light extinction can be directly related to gaseous and aerosol concentrations.
Drawback: Light extinction is non-linearly related to a person perception of changes in haze. For example, a 10 Mm-1 increase in bext will have a larger perceived impact on a scene at Bext = 20 Mm-1 than at Bext = 100 Mm-1
Marine Boundary Layer:
Microgram: One millionth of a gram (10-6 g) and also symbolized by µg
Micron: One millionth of a meter (10-6 m) and also symbolized by µm
Mm-1: A unit of light extinction called "Inverse megameters"
Nighttime drainage flow:
NWS: National Weather Service
Benefit: Quantitatively, measures haze or visibility impairment to how human observers perceive changes in visual air quality.
RAOB: Radiosonde observation. This is way to measure meteorological parameters as a function of height at one site. Meteorological parameters collected by a radiosonde include pressure, temperature, humidity, wind speed and wind direction. Routine radiosonde observations are taken world-wide at 00 and 12 UTC daily. See this National Weather Service Radiosonde page that describes the instrument used. There are 92 radiosonde sites in North America operated or overseen by the National Weather Service as shown in this network map.
A standard value of 10 Mm-1 is used in visibility calculations regardless of site elevation
Residence Time: Residence time is the fraction of the total time of
backtrajectories that the backtrajectory was over a given area of 1 degree
latitude by one degree longitude. What is important is not the absolute
residence time number, but the shape of the residence time distribution (e.g.
mostly from the east during hazy days, etc. The absolute number is arbitrary
because it depends on the size of the area considered and the length of the
backtrajectories in days.
Residence time difference: Residence time difference maps give the percent residence time for some condition (e.g. high sulfate) minus the percent residence time for all conditions (i.e. average residence time)
RPO: Regional Planning Organization
SO4: This refers to sulfate aerosol. Sometimes we represent SO4 as S (elemental sulfur) in this website. In this case we assume that all elemental sulfur is from sulfate that is from ammonium sulfate. This is a secondary pollutant primarily from fossil fuel combustion.
USDA FS: United States Department of Agriculture Forest Service
UTC: Coordinated Universal Time
Units: Distance, e.g. kilometers (km)
Benefit: This metric is most useful in situation where only the distance that one can see is important, such as for aviation.
Drawback: Does not account for changes in scene, such as loss of textures and discoloration as haze increases.
VOC: Volatile Organic Compounds
Vog: Conditions occurring in the Hawaiian islands during volcanic eruptions where fog and volcanic ash to mix to create visibility impairment.
WA: Wilderness Area
WRAP: Western Regional Air Partnership