About These Data

VISIBILITY:

Visibility monitoring provides a measure of how far and how well an observer can see through the atmosphere. Visual range conditions are calculated using air quality measurement data gathered by air quality monitors. Light extinction is defined as the loss of light due to scattering and absorption as it passes through the atmosphere.

For this Phoenix region application, the scattering component of extinction is measured by an instrument (nephelometer) that captures small amounts of air at a fixed location. Measurements taken by this instrument can be affected by weather, especially in foggy or rainy conditions.

METEOROLOGY:

Relative Humidity: The ratio of water vapor in ambient air compared to the maximum amount of water vapor that could occur at the ambient air temperature. The ratio is measured as a percent.

Temperature: The ambient air temperature measured in degrees Fahrenheit and Celsius.

Wind Direction: Wind direction is the direction from which the wind is blowing. It is measured using a compass scale of 0 to 360 degrees. North is 0 or 360 degrees; east is 90 degrees; south is 180 degrees; and west is 270 degrees. See diagram.

For example: a wind direction of 90 degrees describes wind blowing from the east.

Wind Speed: Wind velocity measured in miles per hour.

REAL-TIME DATA DISCLAIMER

All data posted on the 48-hour data record page are raw data. They have not been validated by human review and may contain errors. Real-time data must be interpreted with caution. These data are provided for public awareness and Land Manager review only. They should not be used in any medical or scientific study. Contact the Arizona Department of Environmental Quality to obtain quality-assured data summaries or access to fully-validated data.