GCIP/LSA-NW EAOP 1999 Montana's Remote Weather Informational System (MT-RWIS) Hourly Surface Data in QC format 1.0 General Description Montana's Remote Weather Informational System (RWIS) Hourly Surface Data in QC format is one of several datasets provided in the GEWEX Continental-Scale International Project (GCIP) Large Scale Area-North West (LSA-NW) Enhanced Annual Observing Period (EAOP) 1999 This dataset contains the available data for the GCIP LSA-NW EAOP-99 domain and time period (01 April 1999 through 31 March 2000). The GCIP LSA-NW EAOP-99 domain is approximately 90W to 115W longitude and 36N to 51N latitude. These data were not quality controlled by the University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS). 2.0 Detailed Data Description Montana's Remote Weather Informational System (MT-RWIS) consists of 56 sites across the state. Remote weather informational systems provide real time information via standard communication tools (phone lines and computer networks) statewide. These sites are located in strategic locations to provide accurate real time weather information. This information allows Montana Department of Transportation (MT-DOT) employees to schedule personnel and equipment based on current weather and pavement surface conditions. Real time weather information improves response time, increases winter maintenance efficiency and minimizes the traveling public's exposure to hazardous weather related roadway conditions. A description of each parameter used in the MT_RWIS hourly surface data is provided below: Air Temperature: Air temperature at the RPU. Dew Point Temperature: Temperature 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. Wind Speed: Average speed of the wind during a one minute period. Wind Direction: Average wind direction during a one minute period. 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 001 to 360. Cardinal Format Degree Range ---------------------------- North N 338 - 22 Northeast NE 23 - 68 East E 69 - 112 Southeast SE 113 - 158 South S 159 - 202 Southwest SW 203 - 248 West W 249 - 292 Northwest NW 293 - 337 Gust: Maximum wind speed measured during a one minute period. The Remote Processing Unit (RPU) averages the wind speed every four seconds and collects 15 four-second averages in one minute. The largest of these 15 values is the gust value. Higher resolution MT_RWIS data is located in the Montana Remote Weather Informational System Specials Surface Data in a QC format dataset. More information can be found at the following MDT RWIS web sites: http://www.mdt.state.mt.us/departments/maintenance/rwis/mdtrwis.html and http://www.mdt.state.mt.us/ . To view the real time weather station information visit the MDT RWIS site at http://rwis.mdt.state.mt.us/ . 2.1 Detailed Format Description The GCIP LSA-NW EAOP-99 Hourly Surface Data contains ten metadata parameters and 38 data parameters and flags. The metadata parameters describe the station location and time at which the data were collected. The time of observation is reported both in Universal Time Coordinated (UTC) Nominal and UTC actual time. Days begin at UTC hour 0100 and end at UTC hour 0000 the following day. The data parameters are valid for the reported times. Missing values are reported as 9's in the data field. The table below details the data parameters in each record. Several data parameters have an associated Quality Control (QC) Flag Code. For a list of possible QC Flag values see the Quality Control Section 3.0. Parameters Units ---------- ----- Date of Observation UTC Nominal Time of Observation UTC Nominal Date of Observation UTC actual Time of Observation UTC actual Network Identifier Abbreviation of platform name Station Identifier Network Dependent Latitude Decimal degrees, South is negative Longitude Decimal degrees, West is negative Station Occurrence Unitless Station Elevation Meters Station Pressure, QC flag Hectopascals (mb) Reported Sea Level Pressure, QC flag Hectopascals (mb) Computed Sea Level Pressure, QC flag Hectopascals (mb) Dry Bulb Temperature, QC flag Celsius Dew Point, QC flag Celsius Wind Speed, QC flag m/s Wind Direction, QC flag Degrees Total Precipitation, QC flag mm Squall/Gust Indicator Code Value Squall/Gust Value, QC flag m/s Present Weather, QC flag Code Value Visibility, QC flag Meters Ceiling Height (first layer) Hundreds of feet Ceiling Flag (first layer), QC flag Code Value Cloud Amount (first layer), QC flag Code Value Ceiling Height (second layer) Hundreds of feet Ceiling Flag (second layer), QC flag Code Value Cloud Amount (second layer), QC flag Code Value Ceiling Height (third layer) Hundreds of feet Ceiling Flag (third layer), QC flag Code Value Cloud Amount (third layer), QC flag Code Value The list of code values for the Present Weather is too large to reproduce in this document. Refer to WMO, 1988 for a complete list of Present Weather codes. The code values for the Squall/Gust Indicator are: Code Definition ---- ---------- blank No Squall or Gust S Squall G Gust The code values for the Ceiling Flag Indicator are: Code Definition ---- ---------- 0 None 1 Thin 2 Clear below 12,000 feet 3 Estimated 4 Measured 5 Indefinite 6 Balloon 7 Aircraft 8 Measured/Variable 9 Clear below 6,000 feet (AUTOB) 10 Estimated / Variable 11 Indefinite / Variable 12 12-14 reserved 15 Missing The code values for the Cloud Amount Indicator are: Code Definition ---- ---------- 0 0 ( or clear) 1 1 okta or less, but not zero or 1/10 or less, but not zero 2 2 oktas or 2/10-3/10 3 3 oktas or 4/10 4 4 oktas or 5/10 5 5 oktas or 6/10 6 6 oktas or 7/10-8/10 7 7 oktas or more, but no 8 oktas or 9/10 or more, but not 10/10 8 8 oktas or 10/10 (or overcast) 9 Sky obscured by fog and/or other meteorological phenomena 10 Sky partially obscured by fog and/or other meteorological phenomena 11 Scattered 12 Broken 13 13-14 Reserved 15 Cloud cover is indiscernible for reasons other than fog or other meteorological phenomena, or observation is not made. 2.2 Data Remarks Wind speed, wind direction and wind gust values are averaged over the previous minute ending with the measurement time. 3.0 Quality Control Processing This data was not quality controlled by UCAR/JOSS. See Table 3-1 for a list of the possible quality control flags and their meanings. Table 3-1 - Quality Control Flags QC Code Description ------- ----------- U Unchecked G Good M Normally recorded but missing. D Questionable B Unlikely N Not available or Not observed X Glitch E Estimated C Reported value exceeds output format field size or was negative precipitation. T Trace precipitation amount recorded I Derived parameter can not be computed due to insufficient data. 4.0 References Montana's Remote Weather Informational Service http://www.mdt.state.mt.us/departments/maintenance/rwis/mdtrwis.html; Aug 9, 2002