VORTEX Surface Composite 1.0 General Description The Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX) Surface Composite is composed of data from several sources (i.e., 20 minute Handar Automated Weather Observing System (AWOS), 20 minute Qualimetrics AWOS, 20 minute Artais AWOS, 5 minute Oklahoma Mesoscale Network, 5 minute Artais AWOS, and 5 minute Automated Surface Observation System (ASOS) for the VORTEX domain). Data from these sources (over 200 hundred stations) were merged and quality controlled to form this Surface Composite. This Surface Composite contains data for the VORTEX time period (01 April 1994 through 15 June 1994) and for the VORTEX domain only. The VORTEX domain is approximately 31N to 40N latitude and 91W to 107W longitude. A complete detailed data description is provided in Section 2.0. 2.0 Detailed Data Description The Surface Composite is composed of data from several different sources which report data at different frequencies, so it is important to note the conversion processes which were applied to each of these input datasets. Aviation Weather Observation System (AWOS) Data The AWOS data collected for VORTEX consisted of both Federal and Non-Federal networks of automated weather reporting stations located at thirty-three airports in the VORTEX domain. The FAA coordinated the operation, maintenance, and data dissemination of the Federal network, while individual airports/cities operated and maintained non-federal network stations. Most of the archived AWOS data consists of 20-minute averages of air temperature, dewpoint, altimeter, visibility, wind speed and direction, barometric pressure, sky conditions (cloud cover and height), and density altitude averages. Winds were averaged using a 2-min running mean and cloud heights were averaged using a 30-min running mean. Precipitation is the accumulated precipitation for either the 5-minute or 20-minute period, depending on the data frequency. Station pressure is calculated from altimeter setting. There are no present weather or sea level pressures reported for the AWOS data. Twenty minute AWOS data was collected from Handar (System manufactured by Handar Inc., Sunnyvale, CA), Qualimetrics (System manufactured by Qualimetrics, Inc., Sacramento, CA), and Artais (System manufactured by Artais Weather Check Inc., Columbus, OH) stations. Five minute data were collected from one Artais AWOS station in Norman, OK (OUN). The AWOS data were collected in near real-time by the Office of Field Project (OFPS) Data Management Center. Automated Surface Observation System (ASOS) data The National Weather Service, Federal Aviation Administration (FAA), and the U.S. Navy are installing a national network of ASOS stations as part of the NWS modernization plan, FAA airport upgrades, and DoD installations. Sixty-six stations in the VORTEX domain were installed by mid-June, primarily in the Kansas-Oklahoma area. Data collected from each station consisted of 5-min averages of air temperature, dewpoint, wind speed and direction (incl. gust), barometric pressure, altimeter, density altitude, visibility, sky conditions (cloud cover and height) and precipitation (5-min totals). Visibility and sky condition data were computed using a 30-min running average. A total of fifteen ASOS sites were officially commissioned during VORTEX. (Caution should be exercised by the researcher when using uncommissioned ASOS data.) Refer to the ASOS User's Guide to understand how the ASOS stations create the 5 minute reports from raw data. The initial ASOS observations were in SAO format. ASOS data were collected in real-time by the OFPS Data Management Center. Oklahoma Mesoscale Network The Oklahoma Mesonet is a joint effort of the University of Oklahoma and Oklahoma State University. The mesonet consists of 111 automated stations (at least one per county) that measure atmospheric and soil parameters at a station spacing of approximately 35 km (19 miles). Specifically these data include 5-min measurements of air temperature, relative humidity, solar radiation, wind speed and direction, precipitation, leaf wetness, and soil temperature. The data are transmitted to the Oklahoma Climatological Survey every 15-min for processing, quality assurance, archival and dissemination. Five minute Oklahoma Mesoscale Network data are included in this Surface Composite. The Surface Composite contains ten metadata parameters followed by 38 data parameters and flags. Table 1 below details the metadata and data parameters in each record. 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 0000 and end at UTC hour 2355. Missing data is shown as -9's (e.g., -999.99). When squall is not reported, that field is left blank. All records are identical in length. Several data parameters have an associated Quality Control (QC) Flag Code which is assigned during the OFPS quality control processing. For a list of possible QC Flag values see the Quality Control Section 3.0. Table 1 - Surface Composite parameters and descriptions. 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 [See Table 2.] 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 [See Table 3.] Cloud Amount (first layer), QC flag Code Value [See Table 4.] Ceiling Height (second layer) Hundreds of feet Ceiling Flag (second layer), QC flag Code Value [See Table 3.] Cloud Amount (second layer), QC flag Code Value [See Table 4.] Ceiling Height (third layer) Hundreds of feet Ceiling Flag (third layer), QC flag Code Value [See Table 3.] Cloud Amount (third layer), QC flag Code Value [See Table 4.] 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. Table 2 - Squall/Gust Indicator code values. Code Definition ---- ---------- S Squall G Gust Table 3 - Ceiling Flag code values which define ceiling information that can not be indicated by the numeric Ceiling Height value. 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 Table 4 - Cloud Amount Indicator code values. 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. 2.1 Data Remarks This Surface Composite contains both 5 minute and 20 minute data. 3.0 Quality Control Processing The Surface Composite was formed from several sub-datasets (i.e., 20 minute Handar AWOS, 20 minute Qualimetrics AWOS, 20 minute Artais AWOS, 5 minute Artais AWOS, 5 minute Oklahoma Mesonet, and 5 minute ASOS for the VORTEX domain). Each dataset was quality controlled by comparing the actual station observations with the MAPS (Mesoscale Analysis and Predictions System) hourly gridded surface analyses. MAPS was developed and the analyses were produced by the Forecast Systems Laboratory of the NOAA Environmental Research Laboratories (Miller and Benjamin, 1992). A similar method which was used to quality control the STORM- FEST data (Scully and McGuirk, 1993) was applied to the VORTEX Surface Composite. However, the limits used for flagging were modified for the VORTEX domain. Hourly MAPS gridded values were interpolated to a station's latitude, longitude, elevation and observation time and were then compared to the observed values. Observed values were then flagged "good", "questionable" or "unlikely" based upon the comparison with MAPS. Table 5 describes the flags used during quality control. Data were never changed, only flagged. Only the station pressure, sea level pressure, temperature, dew point, wind speed and wind direction were quality controlled this way. Gross limits checks were applied to precipitation data. Table 6 shows the allowed variance (flag limits) from MAPS values for each parameter. Table 5 - 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 precipitation value exceeds 9999.99 millimeters or was negative. T Trace precipitation amount recorded. Table 6 - Quality Control Flag limits. Parameters Good Questionable Unlikely ---------- ---- ------------ -------- Station Pressure <2.00mb >=2.00mb >=5.00 mb Sea Level Pressure <2.00mb >=2.00 mb >=5.00 mb Dry Bulb Temp <2.50 C >=2.50 C >=5.00 C Dew Point Temp <2.50 C >=2.50 C >=5.00 C Wind Speed <5.00 m/s >=5.00 m/s >=10.00 m/s Wind Dir (Ws<10m/s) <=90.00 deg >90.00 deg ---------- Wind Dir (Ws>=10m/s) <=50.00 deg >50.00 deg >=90.00 deg Precipitation (5min data) <10.00 mm >=10.00 mm >=25.00 mm Precipitation (20min data) <20.00 mm >=20.00 mm >=50.00 mm The squall/gust wind speed data were not quality controlled. Only gross limit checks were also used to determine the quality of the precipitation values. Note that different gross limits were applied to the 5 minute and 20 minute datasets. Several "questionable" and "unlikely" data values were also manually inspected. After inspection, the quality control flag may have been manually updated to better reflect the likelihood of the actual occurrence of the precipitation value. Data was never modified, only flagged. Negative precipitation was also coded "unlikely". General consistency checks were 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". Wind directions of less than zero or greater than 360 degrees were coded "unlikely". 4.0 References For additional station information, refer to the station list description document. Scully, K.W. and McGuirk, D.E., 1993: The Use of MAPS Analyses for Quality Control of Surface Observations from STORM-FEST. Preprints, Eight Symposium on Meteorological Observations and Instrumentation, Anaheim, California, 17-22. Miller, P.L. and Benjamin S.G., 1992: A System for the Hourly Assimilation of Surface Observations in Mountainous and Flat Terrain. Mon. Wea. Rev., 120, 2342-2359. World Meteorological Organization (WMO), 1988: Manual on Codes Volume I, Part B - Binary Codes. WMO, Geneva, Switzerland. ASOS User's Guide, National Weather Service, National Oceanic and Atmospheric Administration, Washington, D.C., June 1992.