Atmospheric Data Definitions
| Measurement | Label | Details | |||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Air Temperature | Air Temp | Air temperature at the site in Fahrenheit (F) degrees. | |||||||||||||||||||||||||||
| Relative Humidity | RH | Percent of moisture in the air. A relative humidity of 0% shows that the air contains no moisture and 100% shows that the air is completely saturated and cannot absorb more moisture. | |||||||||||||||||||||||||||
| Dew Point Temperature | Dew Temp | Temperature in Fahrenheit degrees at which the air becomes saturated as it cools. If the road or runway temperature drops to or below the dew point, moisture may develop on the surface. The form the moisture takes depends on the surface temperature and the amount of chemical present. | |||||||||||||||||||||||||||
| Wet Bulb Temp. | Wet Bulb | The wet bulb temperature is the temperature (F) of a thermometer whose bulb is wrapped in wet muslin. The wetbulb is always in between the temperature and dew point, except at saturation, when all three are equivalent. This value is only displayed for National Transportation Communications for Intelligent Transportation System (ITS) Protocol (NTCIP) sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| Min Air Temperature | Min Temp | The minimum temperature (F) recorded during the 24 hours preceding the observation. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| Max Air Temperature | Max Temp | The maximum temperature (F) recorded in Fahrenheit during the 24 hours preceding the observation. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| Average Wind Speed | Wind Avg | Average mile per hour speed (mph) of the wind during an evaluation cycle. | |||||||||||||||||||||||||||
| Average Wind Gust | Wind Gust | Maximum wind speed (mph) measured during an evaluation cycle. The time period over which wind gust speed is monitored can vary based on the type and manufacturer of the RWIS site. | |||||||||||||||||||||||||||
| Wind Direction Gust Direction |
Avg Dir Gust Dir |
Average wind direction during an evaluation cycle. Wind direction can be displayed in two formats: cardinal points or degrees. Cardinal format has 8 possible headings. Degree format displays wind direction in values ranging from 1 to 360.
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| Visibility | Visibility | Average distance that you can see, both day and night, computed every three minutes. | |||||||||||||||||||||||||||
| Precipitation Type | Type | Type of precipitation detected by a precipitation sensor, if one is available. Certain types of precipitation sensors can only detect the presence or absence of precipitation and will display Yes or No. Other types of precipitation sensors, such as the Weather Identifier and Visibility Sensor (WIVIS) or Optical Weather Identifier (OWI), can classify the type of precipitation and will report a specific type of precipitation. The WIVIS and OWI precipitation sensors may report Yes at the onset of precipitation until sufficient time has elapsed to classify the precipitation type. | |||||||||||||||||||||||||||
| Precipitation Intensity | Intensity | Intensity of the precipitation as derived from the precipitation rate. The National Weather Service defines the following intensity classes: light, moderate, or heavy. | |||||||||||||||||||||||||||
| Precipitation Rate | Rate | Average precipitation rate computed every minute. Snowfall is converted to water equivalent and the rate represents the rate of liquid equivalent. | |||||||||||||||||||||||||||
| Precipitation Start Time | Start Time | The time at which the most recent precipitation event began. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| Precipitation End Time | End Time | The time at which the most recent precipitation event ended. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| Precipitation Accumulations | Rainfall amount or snowfall liquid equivalent for the period from midnight Greenwich Mean Time (GMT) to the current time. At midnight GMT the total accumulation is reset to zero. See the accumulation definitions below for the proper NTCIP accumulation definitions. | ||||||||||||||||||||||||||||
| 1 Hour Precip Accum | 1 hour | Rainfall amount or snowfall liquid equivalent for the previous 1 hour period. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| 3 Hour Precip Accum | 3 hour | Rainfall amount or snowfall liquid equivalent for the previous 3 hour period. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| 6 Hour Precip Accum | 6 hour | Rainfall amount or snowfall liquid equivalent for the previous 6 hour period. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| 12 Hour Precip Accum | 12 hour | Rainfall amount or snowfall liquid equivalent for the previous 12 hour period. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
| 24 Hour Precip Accum | 24 hour | Rainfall amount or snowfall liquid equivalent for the previous 24 hour period. This value is only displayed for NTCIP sites configured with the appropriate sensor. | |||||||||||||||||||||||||||
Pavement Data Definitions
| Measurement | Label | Details |
|---|---|---|
| Surface Status | Status | Condition of the pavement surface. |
| Surface Temperature | Surface Temp | Temperature in Fahrenheit (F) of the pavement surface. |
| Pavement Temperature | Pavement Temp | Temperature (F) of the pavement 2 to 10 cm below the pavement surface. |
| Subsurface Temperature | Sub Temp | Typically, the temperature (F) approximately 43 cm (17 inches) below the top of the pavement. You can place additional subsurface sensors at different depths to monitor frost depth. |
| Freeze Temperature | Freeze Temp | Freezing point (F) of the moisture on the pavement sensor based upon the specific chemical in use. This field is reported when the surface status is Wet, Chemical Wet, or Snow/Ice Warning. |
| Chemical Factor | Chem Factor | Relative indication of chemical present in the moisture on the surface. Chemical factor uses a relative scale ranging from 0 to 100. |
| Chemical Percent | Chem Percent | Percent of chemical saturation in the moisture. This field is reported when the surface status is Wet, Chemical Wet, or Snow/Ice Warning. |
| Water Depth | Water Depth | Depth of water layer on the sensor. This field is reported when the surface status is Wet, Chemical Wet, or Snow/Ice Warning and the surface temperature is above the freeze point temperature. |
| Ice Percentage | Ice Percent | Percent of ice in the moisture. When ice percentage is roughly 50% to 85%, you would typically call the surface moisture "slush". This field is reported when the surface status is Wet, Chemical Wet, or Snow/Ice Warning. |
| Friction Index | Friction | A value from 0 to 1 represents the deceleration capabilities of vehicles while taking into account current surface conditions. Larger values indicate a higher level of friction while smaller values represent a lower level of friction. |
| Conductivity | Conductivity | The conductance of the ice/liquid mixture on the pavement. This value is only displayed for NTCIP sites configured with the appropriate sensor. |
| Salinity | Salinity | Salinity is roughly the number of grams of dissolved matter per kilogram of seawater. Units shown in parts per 100,000. This value is only displayed for NTCIP sites configured with the appropriate sensor. |
Surface Status Definitions
| The following surface status codes are listed in order of severity with the most critical status listed first. | |
| Status | Description |
| Snow/Ice Warning | Continuous film of ice and water mixture at or below freezing (32°F / 0°C) with insufficient chemical to keep the mixture from freezing. This status can only be reported at Vaisala ESP and SP sites when precipitation occurs. |
| Ice Warning | Continuous film of ice and water mixture at or below freezing (32°F / 0°C) with insufficient chemical to keep the mixture from freezing. This status can only be reported at NTCIP sites. |
| Snow Warning | This status can be reported at NTCIP sites, but will not be reported by Vaisala NTCIP sites. |
| Wet Below Freezing | Moisture on pavement sensor with a surface temperature below freezing (32°F / 0°C). This status will only be reported at Vaisala SCAN Detector sites. |
| Ice Watch | Thin or spotty film of moisture at or below freezing (32°F / 0°C). This status can only be reported at NTCIP sites when precipitation is not occurring. |
| Snow/IceWatch | Thin or spotty film of moisture at or below freezing (32°F / 0°C). This status can only be reported at Vaisala ESP and SP sites when precipitation is not occurring. |
| Snow Watch | This status can be reported at NTCIP sites, but is not detected at Vaisala NTCIP sites. |
| Frost | Moisture on pavement at or below freezing (32°F / 0°C) with a pavement temperature at or below the dew point temperature. This status can only be reported by Vaisala ESP, SP, and NTCIP sites when precipitation is not occurring. |
| Chemical Wet | Continuous film of water and ice mixture at or below freezing (32°F or 0°C) with enough chemical to keep the mixture from freezing. This status can only be reported by Vaisala ESP, SP, and NTCIP sites when precipitation occurs. |
| Wet | Continuous film of moisture on the pavement sensor with a surface temperature above freezing (32°F or 0°C). This status can be reported by Vaisala ESP, SP, SCAN Detector, and NTCIP sites when precipitation has occurred. |
| Damp | Thin or spotty film of moisture above freezing (32°F or 0°C). This status can only be reported by Vaisala ESP, and SP sites when precipitation is not occurring. |
| Trace Moisture | Thin or spotty film of moisture above freezing (32°F or 0°C). Surface moisture occurred without precipitation being detected. This status will only be reported at NTCIP sites when precipitation is not occurring. |
| Dry | Absence of moisture on the surface sensor. This status can be reported by Vaisala ESP and NTCIP sites. |
| Other | Other is the standard NTCIP ESS surface condition code to handle conditions not explicitly included in this table. This status will only be reported NTCIP by sensors installed at NTCIP ESS sites. |
| No Report | The surface sensor is not operating properly and requires maintenance. This status will only be reported by Vaisala ESP and SP sites. |
| Error | The surface sensor is not operating properly and requires maintenance. This status will only be reported by NTCIP sites. |