GCIP LSA-NW EAOP 1999 Hourly Surface Composite 1.0 General Description This dataset contains the Great Plains Region Cooperative Agricultural Weather Network (AgriMet), Automated Surface Observing System (ASOS), Colorado Agricultural Meteorological Network (COAGMET), High Plains Climate Network (HPCN), Missouri Automated Agricultural Network (MOCAWS), National Oceanic and Atmospheric Administration (NOAA) Profiler Network (NPN), USDA Natural Resource Conservation Service National Water and Climate Center Soil Climate Analysis Network (SCAN) Soil Moisture/Soil Temperature (NRCS/SMST), National Climatic Data Center (NCDC) Surface Climatic Database (DATSAV3), Montana Department of Transportation Remote Weather Informational System (MTDOT_RWIS), and Wyoming Department of Transportation Roadway Weather Information Systems (WYDOT_RWIS) observation surface data in QC format. Data for the GEWEX Continental- Scale International Project (GCIP) Large Scale Area-North West (LSA-NW) Enhanced Annual Observing Period (EAOP) 1999 domain (36N to 51N latitude and 90W to 115W longitude) and time period (01 April 1999 through 31 March 2000) are contained within this dataset. This GCIP LSA-NW EAOP 1999 Hourly Surface Composite dataset contains data from approximately 800 stations. See section 3.0 below for the quality control processing performed by the University Corporation for Atmospheric Research/Joint Office for Science Support (UCAR/JOSS) on this dataset. 2.0 Detailed Data Description 2.0.1 Great Plains Region Cooperative Agricultural Weather Network (AgriMet) Algorithms UCAR/JOSS was given AgriMet data with a frequency of 15 minutes. These data were used by UCAR/JOSS to produce hourly surface data. AgriMet is a satellite-linked, weather and evapotranspiration (ET) reporting network operated by the United States Department of the Interior (USDI) Bureau of Reclamation. The Great Plains Region AgriMet Data System consists of 14 AgriMet stations operating in Montana. More information on these AgriMet sites can be found at: http://www.gp.usbr.gov/agrimet/agrimet.htm . Each AgriMet station measures temperature, accumulated solar radiation, dewpoint temperature, relative humidity, wind direction and wind gust speed every 15 minutes, as well as accumulated precipitation, average wind speed and the wind run every hour. Below is the description of a typical AgriMet station: Telecommunications Equipment (Manufacturer) * Data Collection Platform, Model 8004 (Sutron Corporation) * YAGI antenna & cable, Model 8200 A * 100 amp-hr battery & cable, #8200 PSB * Solar panel & cable, Model SX-10 * Integrator,solar * 190 amp-hr battery (Exide Corporation) * Integrator,solar (USDA-ARS (Burgess) * Integrator,wind run (USDA-ARS (Burgess) Sensors * Thermistor, YSI #44212 (Yellow Springs Instruments) * Wind Monitor #05103 (R.M.Young) * Pyranometer, Model LI-200SB (Li-Cor) * Relative Humidity Probe, Model 2013A (Texas Electronics) * Relative Humidity Probe, Model HMP-35A (Vaisala) * Tipping Bucket Rain Gage, 6010 & 6011-A (Qualimetrics) * Precipitation Collector, 12 inch (Belfort) The precipitation gages for AgriMet stations BFTM, BOMT, GFMT, and HVMT are not heated, so the precipitation quality control flags for these sites which were flagged "unchecked", "good", and "trace" have been reset to "questionable" during the winter months. 2.0.2 Automated Surface Observing System (ASOS) Algorithms The following are descriptions of the algorithms used by Automated Surface Observing System (ASOS) to produce hourly surface data. These algorithms were also used to generate the ASOS specials. Complete details may be found in the ASOS User's Guide (1992). The ASOS hourly values were produced from ASOS 5-minute data by extracting all parameters (except precipitation) from the 55-minute observation of the previous hour and assigning those values to the current hourly observation. The precipitation is the sum of the precipitation values from the 05-minute of the previous hour through the 00-minute of the current hour. The following are descriptions of the algorithms used by ASOS to produce five minute surface data. Complete details may be found in the ASOS User's Guide (1992). Temperature/Dewpoint ASOS takes 30-sec measurements and computes a 1-min average. A 5-min running average of these 1-min averages is computed. A minimum of four 1-min averages are required to compute a valid 5-min average. 5-min averages are rounded to the nearest degree F. ASOS will report the latest valid 5-min average during the previous 15-min period. If one is not available, the data are reported as "missing". If the 5-min average dewpoint is 1 or 2 degrees higher than the 5-min average temperature, then the dew point is reported equal to temperature. If the 5-min average dewpoint exceeds the 5- min average temperature by more than 2 degrees, the dewpoint is reported as "missing". Station Pressure and Derived Pressure Elements ASOS takes 10-sec measurements from at least two independent pressure sensors and computes respective 1-min averages. A minimum of 5 measurements are required to compute a 1-min average. The 1-min averages from each sensor are compared to verify that differences do not exceed 0.04" Hg. If the sensors are in agreement, the lowest pressure reading from all sensors is reported. If the sensor differences exceed 0.04" Hg, the data are reported as "missing". The reported pressure is then used in the computation of derived parameters (e.g., altimeter setting, sea level pressure, and pressure remarks such as tendency). Wind ASOS takes 5-sec measurements of wind speed and direction and computes a 2-min running average. Wind direction is rounded to the nearest degree and wind speed is rounded to the nearest knot. If the 2-min running average is 2 knots or less, the wind is reported as calm. The gust is computed using the highest 5-sec average wind speed during the past 10-min period. A gust is computed only when the 2-min running average exceeds 9 knots and the highest 5-sec measurement exceeds the 2-min running average by 5 knots (during the past minute). Precipitation ASOS takes 1-min accumulated measurements and computes total precipitation over 5-min, 15-min, hourly, 3-hr, 6-hr, and daily increments. Monthly totals are summed from daily totals. Present Weather There are currently two automated ASOS present weather sensors. They are the Precipitation Identification (PI) sensor which discriminates between rain and snow and the Freezing Rain (ZR) sensor. Although there is no ASOS "Obstruction To Vision" (OTV) sensor, ASOS algorithms evaluate data from multiple sensors (i.e., visibility, temperature, dewpoint temperature, and PI) and infer the presence of obstructions to vision (fog or haze). Once each minute the PI sensor output is stored in memory (up to 12 hours). The latest 10 minutes of data are examined. If 3 or more samples are missing, ASOS reports "missing" for that minute. If 2 or more samples indicate precipitation, and at least 8 one minute samples are available, the algorithm determines the type and intensity to report. In general, to report anything other than light precipitation (P-), two of the samples are required to be the same type. If there is a tie between two types of precipitation, snow is reported. The highest intensity obtained from two or more samples determines the present weather type and intensity that is reported. Once each minute the ZR sensor output is stored in memory (up to 12 hours). Data from the latest 15 minutes are used to compute the current minute freezing rain report. If 3 or more sensor outputs in the past 15- minutes are missing, the report is set to "missing". If at least one positive freezing rain report occurs in the past 15-minutes, freezing rain is reported for the current minute. If freezing rain is reported, the PI sensor report is examined and a hierarchical scheme is used to compute the present weather report. This scheme follows the familiar reporting hierarchy of LIQUID- FREEZING-FROZEN in ascending order of priority. ASOS does not report mixed precipitation. The beginning and ending times of one minute freezing rain reports are used in the hourly SAO reports. Once freezing rain has been sensed and the ambient air temperature is 36 degrees F or below, it will be carried in subsequent SAO reports for 15-minutes after it is no longer sensed. The OTV algorithm continuously monitors the reported visibility once each minute. When visibility drops below 7 statute miles, the algorithm obtains the current Dew Point Depression (DD) to distinguish between fog and haze. If the DD is < or equal to 4 degrees F, then fog will be reported and appended to the present weather report. If DD is > 4 degrees F and no present weather is reported by the PI and ZR sensors, then haze is reported as present weather. When present weather is reported by the PI and ZR sensors, haze is not reported. In the event DD is missing, visibility is used to discriminate between haze and fog. If visibility is < 4 miles, fog will be reported. When present weather is also reported, fog will be appended to the report. If visibility is > or equal to 4 miles but < 7 miles and no present weather is reported, then haze is reported. 2.0.3 Colorado Agricultural Meteorological Network (COAGMET) The Colorado Agricultural Meteorological Network (COAGMET) consists of 32 automated weather stations in Colorado operated by the Colorado Climate Center. For more information on COAGMET visit the following website: http://ccc.atmos.colostate.edu/~coag/ . Below is the description of a typical COAGMET station. Most stations have a similar configuration but sensors, dataloggers and siting vary somewhat throughout the network. Only the temperature, relative humidity, vapor pressure, wind speed, wind direction and precipitation values are used to create the final dataset, but the description of the sensor for every parameter is included here for reference. Temperature, wind speed and wind direction values are averaged over the hour ending with the measurement time. Dewpoint temperature is calculated by UCAR/JOSS using the formula from Bolton (1980) and the temperature, relative humidity and vapor pressure values from each station. Temperature and Relative Humidity * Model: Vaisala HMP35C Probe * Sensor Height: 1.5 meters * Temperature Specs o Temperature Measurement Range: -35 to 50 DegC o Thermistor Interchangeability Error: Typically <+-0.2 DegC over 0 DegC to 60 DegC; +-0.4 DegC at -35 DegC o Polynomial Linearization Error: <+-0.5 DegC over -35 DegC to 50 DegC * Relative Humidity Specs o RH Measurement Range: 0% to 100% o RH Accuracy (at 20 DegC) +- 2%, 0% - 90%; +-3% >90% o Temperature Dependence of RH Measurement: +-0.04% RH/DegC Wind * Model: R.M. Young 05103 Wind Monitor * Sensor Height: 2 meters * Wind Speed Specs o Range: 0-60 m/s o Starting Threshold: 1.0 m/s o Distance Constant (63% recovery): 2.7 m. * Wind Direction Specs o Range: 0-360 Deg. (355-360 open) o Starting Threshold 10 deg displacement: 0.9 m/s o Starting Threshold 5 deg displacement: 1.3 m/s Precipitation * Model: TE525 tipping bucket raingage * Specs o Sensor height >1m o Collector diameter - 154mm o 0.254mm/tip o accuracy +- 1% for precip of 50mm/hr or less o Operating temperature 0 to 50C (not accurate during winter) Solar Radiation * Model: Licor 200S Pyranometer * Specs o Sensor Height ~2m o 0-10 mv output range o Sensitivity typically 80 microamp/1000 W/m2 o Linearity Maximum deviation 1% up to 3000 W/m2 o Spectral response from 0.4 to 1.1 mu o Typical error under natural daylight +-3%, maximum +-5% Soil Temperature * Model: CSI Model 107 Soil Temp Probe (thermistor) * Specs o +- 0.4C for -33 to +48C all errors inclusive o Sensor depth 50mm and 150mm where two sensors used, 100mm where only one. Leaf Wetness Sensor * Model: CSI Model 237 - Circuit board with interlocking gold plated copper fingers, coated with flat latex paint to spread water layer. Measures electrical resistivity of water film. * Specs o Sensor height ~0.5m Data Logger * Model: Campbell Scientific CR10 * A picture of a CR10 installation can be found at: http://ccc.atmos.colostate.edu/~coag/ws01.gif Site Pictures * Dove Creek (dvc01) - http://ccc.atmos.colostate.edu/~coag/ws01.gif * Burlington (brl02) - http://ccc.atmos.colostate.edu/~coag/ws02.gif * Grand Junction (gjc01) - http://ccc.atmos.colostate.edu/~coag/ws03.gif The precipitation gages in the COAGMET network are not heated, so the precipitation quality control flags for these sites which were flagged "unchecked", "good", and "trace" have been reset to "questionable" during the winter months. 2.0.4 High Plains Climate Network (HPCN) The algorithms used to produce the High Plains Climate Network (HPCN) hourly surface data are not currently available. The High Plains Climate Network reports only the moisture measurement of relative humidity, and does not report any pressure parameter. This hourly composite includes dewpoint as the moisture parameter. To convert relative humidity to dewpoint, the station elevation and the standard atmosphere were used to generate an estimate of the station pressure, which was then used in the relative humidity to dewpoint conversion. 2.0.5 Missouri Automated Agricultural Network (MOCAWS) The algorithms used to produce the Missouri Agricultural Network (MOCAWS) hourly surface data are not currently available. Since the precipitation gages in this network are not heated, the precipitation quality control flags for "unchecked", "good", and "trace" precipitation values have been reset to "questionable" during the winter months. 2.0.6 National Oceanic and Atmospheric Administration (NOAA) Profiler Network (NPN) The algorithms used to produce the NOAA NPN hourly surface data are not currently available. 2.0.7 USDA Natural Resource Conservation Service National Water and Climate Center Soil Climate Analysis Network (SCAN) Soil Moisture/Soil Temperature (NRCS/SMST) The algorithms used to produce NCRS/SMST hourly surface data are not currently available. 2.0.8 National Climatic Data Center (NCDC) DATSAV3 Algorithms UCAR/JOSS was given data in the NCDC Surface Hourly Abbreviated Format, which is derived by NCDC from their DATSAV3 formatted data. This "Abbreviated" format data was used by UCAR/JOSS to produce hourly surface data. The following are descriptions of the algorithms used by NCDC to produce their NCDC DATSAV3 formatted data. The NCDC DATSAV3 Surface Database is composed of worldwide surface weather observations from about 10,000 currently active stations, collected and stored from several sources such as the Automated Weather Network (AWN) and the Global Telecommunications System (GTS). Most collected observations are decoded at the Air Force Global Weather Central (AFGWC) at Offutt AFB, Nebraska, and then sent electronically to the United States Air Force (USAF) Combat Climatology Center (AFCCC), collocated with NCDC in the Federal Climate Complex in Asheville, North Carolina. AFCCC builds the final database through decode, validation, and quality control software. All data are stored in a single ASCII format. The database is used in climatological applications by numerous DoD and civilian customers. DATSAV3 refers to the digital tape format in which decoded weather observations are stored. The DATSAV3 format conforms to Federal Information Processing Standards (FIPS). The DATSAV3 database includes data originating from various codes such as synoptic, airways, Meteorological Aviation Routine Weather Reports (METAR), and Supplementary Marine Reporting Station (SMARS), as well as observations from automatic weather stations. The users handbook provides complete documentation for the database and its format. AFCCC sorts the observations into station-date-time order, validates each station number against the Air Weather Service Master Station Catalog (AWSMSC), runs several quality control programs, and then merges and sorts the data further into monthly and yearly station-ordered files. AFCCC then provides the data to the collocated National Climatic Data Center (NCDC). For more information about the DATSAV3 format and the quality control performed on this data see NCDC, 1999a. For more information on the Abbreviated Format see the NCDC, 1999b. 2.0.9 Montana Department of Transportation (MTDOT) Remote Weather Informational System (MTDOT_RWIS) Algorithms UCAR/JOSS was given MTDOT_RWIS data with frequencies as high as 1 minute. These data were used by UCAR/JOSS to produce an hourly surface dataset using the reading closest to each hour. Montana's Department of Transportation Remote Weather Informational System 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 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 MTDOT_RWIS hourly surface data is provided below: Air Temperature: Air temperature at the Remote Processing Unit(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. The table below shows the cardinal, degree range, and UCAR/JOSS Quality Control Format (QCF) translation. Cardinal Format Degree Range QCF Translation (Deg) ---------------------------------------------------- North N 338 - 22 0 Northeast NE 23 - 68 45 East E 69 - 112 90 Southeast SE 113 - 158 135 South S 159 - 202 180 Southwest SW 203 - 248 225 West W 249 - 292 270 Northwest NW 293 - 337 315 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. Every wind direction for this network was flagged to be "questionable" since the directions were computed from ordinal values. More information can be found at the following MTDOT 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 MTDOT RWIS site at http://rwis.mdt.state.mt.us/ . 2.0.10 Wyoming Department of Transportation (WYDOT) Roadway Weather Information Systems (WYDOT_RWIS) Algorithms The Wyoming Department of Transportation maintains the Roadway Weather Information System which is comprised of two separate networks of automated climatological stations across the State of Wyoming. The purpose of the system is to provide near real-time atmospheric and road condition information to the Department of Transportation district and field offices as well as the Wyoming Highway Patrol. The system is also regularly used by the National Weather Service in the course of forecast activities. RWIS station deployment began in 1988 with 4 unique stations. The system has been upgraded and expanded through new station installation, and currently comprises a total of 27 stations statewide. RWIS stations operating in the State of Wyoming regularly monitor temperature, dew point, wind direction and speed, relative humidity, and precipitation determination. Accumulated precipitation values are also available for a few select sites. Significant changes in parameter values between pollings are identified with a special data flag. While only a minimal amount of QA/QC takes place with the climatological data that is collected, the information acquired in many cases represents the only known climatological monitoring ever done at these often remote locations. Individuals wishing to use RWIS climate data should be aware that only a very few agencies are archiving the information beyond the short term histories (last 3 months) resident on the Wyoming Department of Transportation servers. This includes the Department of Atmospheric Sciences at the University of Wyoming (UW), and the Water Resources Data System, which possess data back through the 1994 calendar year for a majority of the stations. For more information, contact source agency at Wyoming Department of Transportation 5300 Bishop Boulevard Cheyenne, WY 82009 307 777-4458 Or Wyoming Department of Transportation PO Box 1708 Cheyenne, WY 82009-1708 Additional information can be found at the following web sites; http://www.wrds.uwyo.edu/wydot/wydot.html , http://waterplan.state.wy.us/ and http://waterplan.state.wy.us/sdi/SP/SP06AP04.html , and http://www.wyoroad.info/highway/sensors/sensors.html . The Wyoming Roadway Weather Information Systems database contains observations of temperature, dewpoint, wind, relative humidity, wind speed and direction, and precipitation taken at 15-minute intervals. Data are available for 21 stations around the State of Wyoming. The following channels were converted to UCAR/JOSS QCF format when they existed: Tmp - Temperature in Degrees F converted to Degrees C Dew - Dew point temperature in Degrees F converted to Degrees C Dir - Wind direction from true north (0-360) 999 is missing or calm Spd - Wind speed in mph converted to m/s Gst - Wind gust in mph converted to m/s No other channels were converted. 2.1 Detailed Format Description The GCIP LSA-NW EAOP 1999 Hourly Surface Composite observation 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 0100 and end at UTC 0000 the following day. The table below details the data parameters in each record. Several data parameters have an associated Quality Control (QC) Flag Code which are assigned by the Joint Office for Science Support (JOSS). 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 This dataset contains only the "Nominal" hourly observations for the GCIP LSA-NW EAOP 1999 domain and time period. The special records are located in the GCIP LSA-NW EAOP 1999 Surface "Special" Dataset. MT RWIS wind speed, wind direction and wind gust values are averaged over the previous minute ending with the measurement time. Horizontal visibility values greater than 81910.00 meters were converted to missing due to limits within the EBUFR data format. The precipitation gages for every station in the COAGMET and MOCAWS networks and for stations BFTM, BOMT, GFMT, and HVMT in the AgriMet network are not heated, so the precipitation quality control flags for these sites which were flagged "unchecked", "good", and "trace" have been reset to "questionable" during the winter months (i.e., October through April). 3.0 Quality Control Processing The GCIP LSA-NW EAOP 1999 Hourly Surface Composite was formed from several datasets (i.e., Great Plains Region Cooperative Agricultural Weather Network (AgriMet), Automated Surface Observing System (ASOS), Colorado Agricultural Meteorological Network (COAGMET), High Plains Climate Network (HPCN), Missouri Automated Agricultural Network (MOCAWS), National Oceanic and Atmospheric Administration (NOAA) Profiler Network (NPN), USDA Natural Resource Conservation Service National Water and Climate Center Soil Climate Analysis Network Soil Moisture/Soil Temperature (NRCS/SMST), National Climatic Data Center (NCDC) Surface Climatic Database (DATSAV3), Montana Department of Transportation Remote Weather Informational System (MT_RWIS), and Wyoming Department of Transportation Roadway Weather Information Systems (WY_RWIS)). These GCIP LSA-NW EAOP 1999 Hourly Surface Composite datasets were collected over the GCIP LSA-NW EAOP 1999 domain (i.e., 36N to 51N latitude and 90W to 115W longitude) and time period (01 April 1999 through 31 March 2000) and were combined to form a surface composite. The composite was quality controlled to form the final GCIP LSA-NW EAOP 1999 Hourly Surface Composite. During the JOSS Horizontal Quality Control (JOSS HQC) processing, station observations of pressure, temperature, dew point, wind speed and wind direction were compared to "expected values" computed using an objective analysis method adapted from that developed by Cressman (1959) and Barnes (1964). The JOSS HQC method allowed for short term (>/= 30 day) variations by using 30 day standard deviations computed for each parameter when determining the acceptable limits for "good", "questionable", or "unlikely" flags. "Expected values" were computed from inverse distance weighted station observations within a 300 km Radius Of Influence (ROI) centered about the station being quality controlled (the station being quality controlled was excluded); i.e.; theta_e = / Where theta_e is the "expected value" of the parameter at the site in question, theta(i) is the observed value of the parameter at site i, w(i) is the weighting factor for site i (here the inverse of the distance between site i and the station being quality controlled), and <...> is the sum over all stations "i" in the current ROI that have valid observations of the parameter at the time in question. Data were always compared at like solar times. To determine an observation's HQC flag setting, the difference between the actual observation and its "expected value" was compared to that parameter's normalized standard deviation. Normalizing factors (also called the sensitivity coefficients) were chosen to control the "good", "questionable", and "unlikely" flag limits for each parameter. See Table 3-1 for GCIP LSA-NW EAOP 1999 normalizing factors. Table 3-2 contains the HQC flag limit ranges derived from the normalizing factors given in Table 3-1 and estimated standard deviations for each parameter so that 95% of the QC limits applied to the GCIP LSA-NW EAOP 1999 data fell within these ranges. For example, 95% of the observed station pressure values that were flagged as "good" were within 1.5 mb of the expected value. The significant overlap of the ranges seen in Table 3-2 was partially due to seasonal and station differences in standard deviations. The actual HQC limits applied at any particular time depended upon the dynamic nature of the particular station's parameter values over time. Data were never changed, only flagged. HQC was only applied to station pressure, sea level pressure, calculated sea level pressure, temperature, dew point, wind speed and wind direction. If the calculated sea level pressure quality control information was available, its flag was applied to the station and sea level pressures. If the calculated sea level pressure could not be quality controlled, the sea level pressure quality control flag was applied to the station pressure. If the sea level pressure could not be quality controlled, the station pressure quality control flag was not overridden. Table 3-1 Normalizing factors used for GCIP LSA-NW EAOP 1999 Hourly Surface Composite Parameter Good Questionable Unlikely --------- ---- ------------ -------- Station Pressure 0.2 0.2 0.5 Sea Level Pressure (SLP) 0.2 0.2 0.5 Calculated SLP 0.4 0.4 1.0 Dry Bulb Temperature 0.5 0.5 1.0 Dew Point Temperature 0.5 0.5 1.0 Wind Speed 2.25 2.25 4.0 Wind Direction 1.22 1.22 2.2 Table 3-2 Ranges of HQC flag limit values for GCIP LSA-NW EAOP 1999 Hourly Surface Composite Parameter Good Questionable Unlikely --------- ---- ------------ -------- Station Pressure (mb) < 1.8 [0.5-4.6] > 1.1 Sea Level Pressure (mb) < 2.0 [0.6-5.0] > 1.4 Calculated SLP (mb) < 4.3 [1.2-10.6] > 3.0 Dry Bulb Temperature (deg.C) < 3.7 [1.1-7.4] > 2.2 Dew Point Temperature (deg.C) < 3.5 [1.1-7.1] > 2.2 Wind Speed (m/s) < 7.6 [1.6-13.4] > 2.8 Wind Direction(degrees) < 163.7 [64.0-180.0] >115.4 The squall/gust wind speed data were not quality controlled. General consistency checks were also applied to the dry bulb temperature, wind direction, and the relationship between precipitation and cloud amount/cloud cover. If the dew point temperature was greater than the dry bulb temperature both values were coded "questionable". Also, wind direction for observed "calm" winds was given the same QC code as the wind speed. If precipitation was reported, but the cloud amount was "none" or "clear", then both the cloud amount and precipitation values were coded "questionable". Several impossible values were also checked. Negative wind speeds were coded "unlikely". Negative squall/gust wind speeds were coded "unlikely". Wind directions of less than 0 degrees or greater than 360 degrees were coded "unlikely". If these consistency checks would have upgraded the quality control flags previously set by HQC or gross limit checks, then they were not applied. However, if these consistency checks would have degraded the previously set QC flags, they were applied. The JOSS HQC scheme relied on spatial and temporal continuity to flag the data. It has been shown that this method works very well for temperature, dew point, pressure, and wind speed, but is not a very good scheme for the wind direction. The flags appear to be overly lax and perhaps could be tightened. Gross limit checks were also used to determine the quality of the precipitation values. The gross limits are shown in Table 3-3. Certain "questionable" and "unlikely" data values were also manually inspected. After inspection, the quality control flag may have been manually modified to better reflect the physical reasonableness of the data. Data were never modified, only flagged. Negative precipitation was also coded "unlikely". See Table 3-4 for a list of the possible quality control flags and their meanings. Table 3-3 - Precipitation Gross Limit Values Parameter Good Questionable Unlikely --------- ---- ------------ -------- Hourly Precipitation < 20.0 mm >= 20.0 mm >= 50.0 mm Table 3-4 - 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 ASOS User's Guide, ASOS Project Office, NOAA, National Weather Service, Washington D.C., June 1992. Bolton, D., 1980: The computation of equivalent potential temperature., Mon. Wea. Rev., 108, pp 1046-1053. Colorado State University, Cited 2002: CoAgMet Homepage [Available online from http://ccc.atmos.colostate.edu/~coag/]. Great Plains Cooperative Agricultural Weather Network (AgriMet), cited 2002: [Available on-line from http://www.gp.usbr.gov/agrimet/agrimet.htm]. Grove, Tim, 2002, AgriMet, United States Department of the Interior (USDI) Bureau of Reclamation Precip Gages, information supplied with data. Montana's Remote Weather Informational Service http://www.mdt.state.mt.us/departments/maintenance/rwis/mdtrwis.html; Aug 9, 2002. MDT Remote Weather Information Systems (MTDOT_RWIS), cited 2002: Real Time Weather station information [Available on-line from http://rwis.mdt.state.mt.us/]. MDT Remote Weather Information Systems (MTDOT_RWIS), cited 2002: SCAN Web [Available on-line from http://www.mdt.state.mt.us/departments/maintenance/rwis/mdtrwis.html] and MDT [Available on-line from http://www.mdt.state.mt.us/]. National Climatic Data Center, 1999a: Data documentation for DATSAV3 surface TD-9956, April 20, 1999 National Climatic Data Center, 151 Patton Ave, Asheville, NC 28801-5001 USA. National Climatic Data Center, 1999b: Surface Hourly Abbreviated Format, 09/02/99 National Climatic Data Center, 151 Patton Ave, Asheville, NC 28801-5001 USA. Smithsonian Meteorological Tables, Table No. 65, p.269. Smithsonian Institution Press, Washington, D.C., September, 1949. United States Department of Commerce, 1988: Federal Meteorological Handbook Number 1, Surface Observations. National Oceanic and Atmospheric Administration, Washington, D.C., April 1988. Wallace, J.M., P.V. Hobbs, 1977: Atmospheric Science, Academic Press, 467 pp. World Meteorological Organization (WMO), 1988: Manual on Codes Volume I, Part B - Binary Codes. WMO, Geneva, Switzerland. Wyoming Department of Transportation - Roadway Weather Information Systems (WYDOT_RWIS), cited 2002: Home Page [Available on-line from http://www.wrds.uwyo.edu/wydot/wydot.html]. Wyoming Department of Transportation - Roadway Weather Information Systems (WYDOT_RWIS), cited 2002: The Wyoming Road Report - Atmospheric Sensors [Available on-line from http://www.wyoroad.info/highway/sensors/sensors.html]. Wyoming State Water Plan, Cited 2002: Home Page [Available on-line from http://waterplan.state.wy.us/]. Wyoming State Water Plan, Cited 2002: South Platte River Basin (Point Attribute Data) Roadway Weather Information System (RWIS) [Available on-line from http://waterplan.state.wy.us/sdi/SP/SP06AP04.html].