This data set contains five-minute resolution surface meteorological data in National Center for Atmospheric Research/Earth Observing Laboratory (NCAR/EOL) Quality Control (QC) format from stations within the following networks, and from the following participating research organizations, for the Terrain-induced Rotor Experiment (T-REX):
Data for the Terrain-induced Rotor Experiment (T-REX) domain (34N to 40N latitude and 115W to 126W longitude) and time period (01 March 2006 through 30 April 2006) are contained within this data set. This T-REX 2006 Five Minute Surface Meteorological Composite data set contains data from 154 stations.
Section 2.0 contains a detailed description of the instrumentation, siting, and algorithms used by the source network to collect the data. Section 2.1 contains a detailed description of the format of the composite data set. See Section 2.2 for information on data processing, and Section 3.0 below for the quality control processing performed by NCAR/EOL on this data set. Section 5.0 contains references.
Please review Section 4.0 for the T-REX Data Policy and additional data usage restrictions.
This data set contains surface meteorological data from the Arizona State University (ASU) Environmental Fluid Dynamics Group Sonics Flux Tower placed in Independence, CA for the T-REX project. There is one ASU sonics station included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The ASU Sonics Flux Tower collected data every 0.1 second. The five minute record for the T-REX 5-minute surface composite is an average of a minimum of 200 non-missing 0.1 second records that were recorded during the prior minute to the five minute record. The pressure and dew point measurements from the ASU flux tower were not included in this data set as the data collected during T-REX were not viable due to a power lead having a short.
Note that as directed in the ASU flux tower documentation file the wind direction used in this composite data set was adjusted by +11 degrees for all data from 26 March until 8 April. This was due to an intense wind period on 25 March that led to the booms on which the RM Young sonics were situated being rotated by the force of the wind.
Measurements from the following instrumentation are included in this T-REX 5-minute surface composite.
The Automated Surface Observing System (ASOS) is an automated observing system that is sponsored by the Federal Aviation Administration (FAA), National Weather Service (NWS) and the Department of Defense (DOD). ASOS provides weather observations which include: temperature, dew point, wind, altimeter setting, visibility, sky condition, and precipitation. ASOS stations are installed at airports throughout the country. All 50 stations that are in the T-REX area of interest are included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The Automated Surface Observing Systems are designed to provide airport weather observations in real time. The observing systems work nonstop, updating observations every minute, 24 hours a day, every day of the year. Aviation weather parameters are measured in the runway touchdown zone on the airport.
The ASOS data were acquired by NCAR/EOL for T-REX from an NCDC FTP website once monthly during the T-REX time of interest.
The ASOS uses a chilled mirror to determine the dew point temperature. Once per day the mirror is heated to recalibrate the reference reflection expected from a dry mirror (since a clean mirror needs relatively less indirect light to determine when dew has formed than a dry mirror). This procedure compensates for a possible dirty or contaminated mirror and redefines adaptive criterion value used to determine when dew or frost has occurred. This once per day recalibration nominally takes about 15 min ( ASOS Users Guide, 1998 [ PDF]). The occurrence time of this recalibration varies from station to station. Some stations also vary the occurrence time of the recalibration on about weekly intervals.
There are three station pressures reported at most station for each time period. All stations have at least two pressure sensors and the same methodology is used for stations with two sensors as we use for stations with three sensors. The lowest sensor pressure value obtained, whose pressure difference from either of the other sensors is 0.04 inches or less, is the designated ASOS pressure to be reported at the end of the minute. If no two sensors are within 0.04 inches of each other, then the station pressure is set to missing for that time period. ( ASOS Users Guide, 1998 Section 3.3.2 [ PDF]). Pressures are reported in inches of mercury. NCAR/EOL converts the designated ASOS pressure to millibars and reports it in this 5-minute surface composite.
All Automated Surface Observing System sites included in this composite are commissioned.
For more information on ASOS data and instrumentation, see the National Weather Service Automated Surface Observing System web site (NWS, 2003), Federal Aviation Administration Automated Surface Observing System web site (FAA, 2004), and the ASOS Users Guide, 1998 [ PDF]. Also see the ASOS Users Guide appendices, 1998 [ PDF] which includes instrument specifications and frequencies.
For information on the calculation of parameters derived by NCAR/EOL from the raw parameters available, see Section 2.2.
The 5-minute ASOS data set is formed by extracting 5-minute surface meteorological data from the ASOS 1-Minute Surface Meteorological data. A 5-Minute file is created from a 1-minute file by summarizing the 5 1-minute observations as follows:
Parameter Summarization technique
-------------------------------------------------------------------------
Cloud Height Use amount reported at each 5-minute interval
Visibility Use amount reported at each 5-minute interval
Precip Total over the 5 1-minute periods
Temperature Average over the 5 1-minute periods
Dew Point Average over the 5 1-minute periods
Wind Dir/Speed Break into components, average components
over last two 1-minute periods, compute new vector
Wind Gust Greatest value in last two 1-minute periods
Station Pressure Convert altimeter setting to station pressure;
average over 5 1-minute periods
Sea Level Pressure Average over the 5 1-minute periods
A 5-minute average is calculated from the 1-minute averages provided that at least 4 valid 1-minute averages are available. No record will be written to the output file if more than one observation is missing in the 5-minute interval.
Wind Direction, Speed, and Gusts:
A 5-minute average is calculated from the last two 1-minute averages for the 5-minute time period. If either of these two 1-minute averages are missing, then wind direction, speed, and wind gusts will be set to missing.
This data set contains surface meteorological data from the Automated Surface Observing System (ASOS) station located at the Naval Air Weapons Station (NAWS) China Lake during the Terrain-induced Rotor Experiment (T-REX). These data were provided by NAWS China Lake for the T-REX period (March and April 2006).
See the section above, 2.0.2 Automated Surface Observing System (ASOS), for details on the instrumentation and processing.
This data set contains surface meteorological data from the Naval Air Weapons Station (NAWS) China Lake network of Handar weather stations. There are 8 stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
This data set contains surface meteorological data from the Desert Research Institute (DRI) automatic weather stations around Owens Valley in the southern Sierra Nevada mountains in eastern California. There are 16 stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The DRI AWS reported data every 30 seconds. The five minute records for the T-REX 2006 5-minute composite are the records that occured on the five minute interval.
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
The individual automatic weather stations have been built with the Campbell Scientific instrumentation (CSI; www.campbellscientific.com). Each station has a 10-meter tower with sensors for pressure, temperature, relative humidity and wind mounted directly on the tower or on arms attached to the tower. The sensors are sampled every 3 seconds, and the data is temporally averaged over 30-second non-overlapping intervals. A radio telemetry system connects individual stations to the base station located in Independence, CA to allow remote transmission of temporally averaged data to the central repository at DRI. The radio communication is through 900 MHz spread spectrum wireless radios, manufactured by Freewave.
The network was constructed and is operated in collaboration with Western Regional Climate Center at DRI (www.wrcc.dri.edu). The network has been in continuous operation since late February 2004.
Sensors
Air Temperature and Relative Humidity
Air temperature and relative humidity sensors are Vaisala HMP45C-L. The two separate sensors are packaged in the same sensor housing mounted two meters above the ground.
Wind
Wind is measured by 05103-L Wind Monitor, which has a propeller-type anemometer and a wind vane with fuselage and tail, manufactured by RM Young. It is mounted at the top of the tower, 10 meter above the ground.
Pressure
Air pressure is measured by Vaisala PTB210 digital barometer (www.vaisala.com) using Vaisala BAROCAP Sensor, a silicon capacitive absolute pressure sensor. The sensors and the attached static pressure heads are mounted two meters above the ground.
All sensors are field calibrated by the Western Region Climate Center once a year. The last calibration was in mid-February 2006, close to the start of the T-REX campaign. For information on the calculation of parameters derived by NCAR/EOL from the raw parameters available, see Section 2.2.
Please review Section 4.0 for the T-REX Data Policy and additional data usage restrictions.
The Integrated Surface Flux Facility (ISFF) is designed to study exchange processes between the atmosphere and Earth's surface. This includes the direct measurement of fluxes of momentum, sensible and latent heat, trace gases, and radiation as well as standard atmospheric and surface variables at five minute intervals. Only surface meteorological variables are included in this T-REX 5-minute surface composite. There are 3 ISFF stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
Measurements from the following instrumentation are included in this T-REX 5-minute surface composite.
* Sonic anemometers (all Campbell CSAT3) at 10m.
* T/RH sensors at 5m.
* Vaisala PTB220B, barometer at 1m, with a single-disk static pressure port at 5m.
Wind speed and direction were calculated from U and V wind components. dew point and calculated sea level pressure were calculated by NCAR/EOL. For information on the calculation of parameters derived by NCAR/EOL from the raw parameters available, see Section 2.2.
Algorithms and Sensor Notes
Following are notes on the deployment, operation, and post-project processing of data from each of the sensors. All deployment, operation, and post-project processing described in this section were performed by NCAR/EOL/ISFF. For information on the calculation of parameters derived by NCAR/EOL from the raw parameters available, see Section 2.2. See Section 3.0 for the quality control processing performed by NCAR/EOL on the composite dataset which contains this data.
Sonic Anemometer
CSAT3s were used at all sites. No problems were noted with these during the experiment. Data glitches that were caught by the sensor despiking algorithm appear always to be related to recent rain. The archived data appear to be good.
All sonics reported at 60sps.
The boom angles have been applied to the data, so winds are now in geographic coordinates (+u = wind blowing to East; +v = wind blowing to North; +w = upward). The tilt corrections have not been applied, to keep data from all towers in a similar reference frame (gravitational vertical). Note that fluxes from West (with tilt angles of ~4 degrees) will require some thought to interpret.
Rain Gauge
There are no data before April 6th, 2006, due to the rain gauge cable being connected to the wrong channel on the datalogger. Presumed rain dates judged from zero voltage readings from the krypton hygrometer as water moisture readings are as follows:
March 20th, 2006: ~17:00-00:00 (intermittent rain occurred at all sites)
April 3rd, 2006, ~13:00 - April 4th, 2006, ~11:00 (intermittent rain occurred only at west site only)
April 4th, 2006, ~15:00 - April 5th, 2006, ~1:00 (intermittent rain occurred at all sites)
Site characteristics
For detailed information on siting, instrumentation, and algorithms used during the T-REX project, and for information on, and to access, data and parameters not included in this T-REX 5-minute surface composite see the NCAR EOL ISFF web page (NCAR/EOL/ISFF, cited 2007).
The ISS (Integrated Sounding System) is a self contained meteorological observing system at the Earth Observing Laboratory of the National Center for Atmospheric Research. It consists of a wind profiler radar, radiosonde sounding system, a 10m meteorological tower, solar radiation and other sensors. Only surface meteorological variables are included in this T-REX 5-minute surface composite. There are 2 ISS stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The ISS stations reported data every 1 minute. The five minute records for the T-REX 2006 5-minute composite are the records that occured on the five minute interval with the precipitation being accumulated for the previous five minutes.
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
The ISS subsystems are integrated physically and digitally. A Sun workstation is the heart of the digital integration. The Sun is the center of the ISS computer network and serves to collect, display, and archive data from each of the subsystems. The Sun is connected to personal computers in both the radiosonde sounding system and the profiler/RASS sounding system via SAMBA. Data from the surface observing station are routed serially via RS-232 directly into the Sun workstation. The Sun can also format data and control data flow for transmission to sites well removed from the ISS site.
The ISS surface meteorological instrument installation includes several sensors mounted on two separate towers as well as a rain gauge mounted independently. An anemometer is mounted on the top of a ten-meter tower. Temperature and humidity sensors are mounted on the end of a one-meter boom attached to the ten-meter tower at two meters above the surface. The temperature and humidity sensors are aspirated and protected with a radiation shield. The pressure sensor is housed in the box containing the Campbell CR 10x datalogger. That box is mounted on the ten-meter tower at one meter above the surface and a "pressure port" is connected and mounted at 2 meters. The "pressure port" reduces noise in the pressure sensor due to the venturi effect from the wind.
The radiation sensors are mounted on a one meter boom on the top of a separate one-meter tower. The standard ISS radiation sensors include an up-looking Eppley PSP solar radiation sensor, Eppley PIR sensor and a net radiation sensor. In situations which require more complete radiation measurements, additional sensors can be added.
The output from all the sensors is directed to the Campbell datalogger for processing. The Campbell datalogger, which is independently programmable, typically generates one-minute average data which are sent via RS-232 to the ISS Sun workstation. The data input to the Campbell datalogger are five-second sample data.
Pressure Measurement
The surface pressure sensor used in the ISS installation is either a Vaisala PTA427 or PTA427A pressure sensor. The PTA427 sensor pressure range is 800 to 1060mb while the PTA427A sensor pressure range is 600 to 1060mb. These sensors have an accuracy of +/- 0.5mb and +/- 0.8mb respectively. They are both silicon capacitive pressure sensors patented by Vaisala. Both are temperature compensated and produce a linear voltage output over the full operating range. In order to interface with the Campbell datalogger, a 2:1 voltage divider is incorporated into the cable from the pressure sensor.
Temperature and Humidity Measurement
The temperature and humidity sensors are contained in a Vaisala 50Y humitter which has been carefully calibrated with a curve fit. The actual sensors are a PRT and a Vaisala "humicap" capacitive relative humidity sensor. The temperature sensor accuracy is +/- 0.4 degrees C over the range -33 to +48 degrees C. The accuracy of the humidity sensor against field references is approximately +/- 2% with a long term stability of better than 1% RH per year. These specifications for accuracy are achieved by internal calibration at EOL and data curve fitting in real time. The 50Y humitter sensor probe is protected and ventilated by an RM Young aspirated radiation shield model number 43-408 and external high flow aspiration fan.
Wind Measurement
Wind speed and direction are measured with an R.M. Young 05103 Wind Monitor. The monitor is a propeller wind vane with a 0.9 m/s threshold for wind speed and a 60 m/s maximum. Wind direction is measured using a 360 degree mechanical precision conductive potentiometer. Direction measurements have a threshold of 1.0 m/s at a 10 degree displacement and 1.5 m/s at a 5 degree displacement. The potentiometer is 10 K-ohm, with a life expectancy of 50 million revolutions and has a 0.25% linearity through the entire range.
Rain Measurement
A Texas Electronics TE525 tipping bucket rain gauge is used at all land based ISS sites for measurement of rainfall. The rain gauge resolution is 0.254 mm. The gauge is typically positioned 1.5 meters above the ground about 7 or 8 meters from the ten-meter tower.
Site characteristics
For detailed information on siting, instrumentation, and algorithms used during the T-REX project, and for information on, and to access, data and parameters not included in this T-REX 5-minute surface composite see the NCAR EOL ISS web page, (NCAR/EOL/ISS, cited 2007).
The Mobile Integrated Sounding System (MISS) is a self contained portable meteorological observing system at the Earth Observing Laboratory of the National Center for Atmospheric Research. It consists of a wind profiler radar, radiosonde sounding system, a 10m meteorological tower, solar radiation and other sensors. Only surface meteorological variables are included in this T-REX 5-minute surface composite. There is 1 MISS station included in this T-REX 2006 Five Minute Surface Meteorological Composite . MISS moved several times during T-REX to a total of five different locations.
The MISS station reported data every 1 minute. The five minute records for the T-REX 2006 5-minute composite are the records that occurred on the five minute interval with the precipitation being accululated for the previous five minutes.
Due to issues with the GPS system used during T-REX station elevations were not measured in the field. In order to determine the elevations for the system, the latitutde and longitude locations were input into Google Earth. Google Earth elevations are offset by 20-25 m from those of the DRI AWS and Leeds AWS stations as measured by those groups. The higher offsets were on the eastern side of the Owens Valley. Thus the Google Earth elevations for the MISS locations were offset by this amount. In order to verify these elevations the MISS data was included in some early HQC runs to compare the MISS calculated sea level pressure values with those of nearby stations. The MISS pressures compared very well with nearby stations (~80% good and 20% questionable). All of the questionable flags were applied at the station location F6.
The MISS 10 m tower was blown over during the high wind event of 25 March 2006. The wind data in particular were impacted by this event (e.g. the wind speed was a constant 0m/s for an extended period). Also, once the tower was reset the temperature and dew point data became problematic. The anemometer was reset on 29 March at 2148 UTC. The data during this period is at minimum suspect and has been flagged either questionable or bad.
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
The MISS utilizes the same instrumentation as the ISS above.
Site characteristics
For detailed information on siting, instrumentation, and algorithms used during the T-REX project, and for information on, and to access, data and parameters not included in this T-REX 5-minute surface composite see the NCAR EOL ISS web page (NCAR/EOL/ISS, cited 2007).
This data set contains surface meteorological data from the Tribal Environmental Exchange Network (TREX) from four Climatronics weather stations in the Owens Valley. These data were provided by IPS Meteostar with the approval of the involved tribes. The data were provided at 5 minute resolution. There are 4 stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
All four of these sites use Climatronics instrumentation. The temperature sensors are aspirated. It is not known what the RH sensor method is; the recording instrument is less sensitive in low humidity. All instrumentation is at 10 meters except for pressure and precipitation. These stations are primarily used for air quality purposes.
Photos of each of the stations are available: trex-network.meteostar.com/cgi-bin/lsr/site_photo.pl
Data Collection and Processing
The Tribal Environmental Exchange Network data were processed by the Texas Commission on Environmental Quality (TCEQ). TCEQ uses an automated collection system which analyzes all of the data as it is collected. Based on conditions at the site and the state of the instruments, the system may decide to automatically reject data. TCEQ personnel also continuously review the data and may decide to manually reject data. Rejected data is flagged in various ways depending upon why it was rejected and are flagged with a three-character-code.
During processing by TCEQ t he following codes were applied to the Tribal Environmental Exchange Network data :
NCAR/EOL marked all LST flagged data as Bad and allowed the NCAR/EOL quality control process to handle the LIM flagged data.
This data set contains surface meteorological data from the University of Houston Flux Tower placed at the Owens Valley Radio Observatory about 14 miles south of Bishop and close to the town of Big Pine. There is one Houston flux tower station included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The Houston Flux Tower collected data every 1 minute. The five minute record for the T-REX 5-minute surface composite only includes the records that occurred on the five minute intervals.
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
Measurements from the following instrumentation are included in this T-REX 5-minute surface composite.
This data set contains surface meteorological data from the University of Leeds Automatic Weather Stations. There are 14 stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The Leeds AWS collected data every 3 seconds. The five minute record for the T-REX 5-minute surface composite is an average of a minimum of 8 non-missing 3 second records that were recorded during the prior minute to the five minute record.
The Calculated Sea Level Pressure was computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
The dew point was computed from the temperature and relative humidity using the formula from Bolton (1980).
Instrumentation
The AWS consisted of a 10m instrumented mast with the exception of the "Notch" site being 2m high to minimize visual impact at this exposed site.
Data Notes
The mast at the Notch site blew down at some point in its operation. The exact time at which this happened has not been determined yet. The instruments all seemed to function correctly after the mast was blown down, and so all the Notch data is given here, but the data must be used WITH APPROPRIATE CAUTION.
Please review Section 4.0 for the T-REX Data Policy and additional data usage restrictions.
This data set contains temperature data from the University of Utah HOBO stations located on (a) a West-East line running through Independence, California from the Sierras to the Inyos, (b) a West-East line running through Manzanar, California from the Sierras to the valley center, and (c) on a South-North line running from Lone Pine, California through Bishop, CA. There are 49 HOBO stations included in this T-REX 2006 Five Minute Surface Meteorological Composite .
The sites for the temperature data loggers, also called HOBOs, are named by a one-letter prefix followed by a 2-digit number. This is optionally followed by a letter U. The sites are numbered consecutively from low elevations to higher elevations. On line (a) the HOBOs running westward up the Sierras from the Owens Valley floor are given the prefix W for West, on line (b) the hobos running up the east sidewall into the Inyo Mountains are given the naming prefix E for East. The HOBOs on line (c) are given the prefix M for Manzanar, while the HOBOs running up the valley floor from Lone Pine to Bishop are given the prefix V for Valley_floor. The HOBO temperature sensors were generally exposed in Gill-type 6-plate radiation shields, with the HOBO-radiation shield assembly bolted to fence posts so that the temperature sensors were generally 1 m above the ground. There was some variation in this height.
Seven of the sites on the valley floor had radiation shields that differed from the Gill-type shields mentioned above. These sites (V05U and V06-V11) used the 8-plate solar radiation shields that Onset Computer sells for the HOBOs. We do not anticipate that the type of radiation shield will be an important factor in the reported temperatures, as the radiation shields are both of the "self-aspirated" type and are comparable in design and effectiveness.
Instrumentation
The data logger is the HOBO H8 Pro Temp/Ext Temp data logger sold by Onset Computer of Bourne, Massachusetts (see URL below). This data logger is designed for outdoor use and is described in detail by Onset's commercial literature. The temperature data logger was tested for meteorological usage by Whiteman et al. (2003). Specifications and characteristics of the data logger are provided in that article. The data logger is attached to a Gill-type 6-plate radiation shield sold by the RM Young Co. (and by Campbell Scientific). The data logger is attached to the underside of the 6-plate shield with the temperature sensor itself exposed inside the shield. The radiation shield was attached to vertically-standing T-type steel fence posts that were pounded into the ground about 6 inches. The temperature sensors were nominally 1 m above ground. The effectiveness of the unaspirated radiation shields is described in papers referenced by Whiteman et al. (2000).
HOBO Specification
Number of Channels: 2 (internal and external temperature) Operating Range (logger): -30 to +50C Time Accuracy: 1 minute per week at 20 C Measurement Capacity: 21,763 measurements (one channel at 12-bit and one at 8-bit resolution) Memory: non-volatile eeprom Data Offload Time: <1 minute Size: 102 mm high, 81 mm wide, 55 mm deep Weight: 145 g Battery: 1/2 AA lithium, user-replaceable Battery life (continuous use): 3 years Storage Temperature: -30 to +75 C External Temperature Sensor: thermistor on 1.8 m lead Response Time: <5 minutes in still air Resolution: variable over temperature range -- <0.1 C over the range 0 to 40 C Accuracy: variable over temp range -- better than 0.4 C over the range from -10 to 50 C
Data Remarks
Sites W03 and V04 were knocked over by cows sometime during the deployment. The user should check data from these sites to determine when this happened and how it affected the data. Other sites (M03, M13, and W04) were disturbed slightly by cows rubbing against the fence posts and tilting the radiation shields upward (but not knocking them down). Data from these "disturbed" sites are probably OK without modification.
HOBO manufacturer: www.onsetcomp.comRadiation shield manufacturer www.met.utah.edu/Members/whiteman
Whiteman's T-REX web page: www.met.utah.edu/whiteman/T_REX
Whiteman's T-REX HOBO site photos (includes maps): homepage.mac.com/davidwhiteman/PhotoAlbum4.html
T-REX map server: mapserver.eol.ucar.edu/trex/
The T-REX Five Minute Surface Composite observation data contains 10 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. For this five minute surface composite, reported nominal time and actual time are the same. 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 Earth Observing Laboratory Data Management Group. 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.
This data set contains five-minute observations for the T-REX domain and time period. Please note that five-minute observations from the Weather Station on Wheels (WOW) are contained in a separate data set. The component data sets from which this data set was compiled are available on-line in native format via the T-REX Master Table of data sets (NCAR/EOL, 2006)
Calculated Sea Level pressure is computed from station pressure, temperature, dew point, and station elevation using the formula of Wallace and Hobbs (1977).
When not present in the raw data, the dew point temperature was computed by NCAR/EOL from station pressure, temperature, and relative humidity using the formula from Bolton (1980). This calculation was done for the following networks: China Lake Handar, Desert Research Institute (DRI) Automatic Weather Station Data, NCAR/EOL/ISFF, NCAR/EOL/ISS, NCAR/EOL/MISS, TREX, University of Houston Flux Tower, and University of Leeds AWS.
This T-REX Five Minute Surface Composite does not contain any Sea Level Pressures.
The T-REX 2006 Five Minute Surface Meteorological Composite was formed from several datasets:
These T-REX 2006 Five Minute Surface Meteorological Composite
datasets
were collected over the T-REX 2006 domain (i.e., 34N to 40N latitude and
115W to 126W longitude) and time period (1 March 2006 through 30 April 2006)
and were combined to form a surface composite. The composite was quality
controlled to form the final T-REX 2006 Five Minute Surface Meteorological Composite
.
NCAR/EOL MISS is included in the T-REX 2006 Five Minute Surface Meteorological Composite, but
no mobile data were included in the final Horizontal Quality Control processing.
During the NCAR/EOL Horizontal Quality Control (NCAR/EOL 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 NCAR/EOL 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 100 km Radius Of Influence (ROI) centered about the station being quality controlled (the station being quality controlled was excluded); i.e.;
theta_e = < theta(i)/w(i) > / < w(i) >
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. Only sites with elevation differences of less than or equal to 200.0 meters were included in the calculation of the "expected value". 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 T-REX 2006 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 T-REX 2006 data fell within these ranges. For example, 95% of the observed sea level pressure values that were flagged as "good" were within 1.2 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 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. Note that there were no sea level pressures in this composite.
Table 3-1 Normalizing factors used for T-REX 2006 Five Minute Surface Meteorological Composite
Parameter Good Questionable Unlikely
--------- ---- ------------ --------
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 T-REX 2006 Five Minute Surface Meteorological Composite
Parameter Good Questionable Unlikely
--------- ---- ------------ --------
Sea Level Pressure (mb) N/A N/A N/A
Calculated SLP (mb) < 2.8 [1.2-7.0] > 3.0
Dry Bulb Temperature (deg.C) < 2.4 [0.9-4.8] > 1.7
Dew Point Temperature (deg.C) < 3.2 [0.9-6.4] > 1.7
Wind Speed (m/s) < 8.5 [1.6-15.1] > 2.8
Wind Direction(degrees) < 146.9 [43.1-180.0] >77.8
The squall/gust wind speed data were not quality controlled.
General consistency checks were also applied to the dry bulb temperature, wind direction, squall/gust, 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 flagged "questionable". Also, wind direction for observed "calm" winds was given the same QC code as the wind speed. If the wind speed was greater than the squall/gust, then the squall/gust QC code was set to "dubious". If precipitation was reported, but the cloud amount was "none" or "clear", then both the cloud amount and precipitation values were flagged "questionable".
Several impossible values were also checked. Negative wind speeds were flagged "unlikely". Negative squall/gust wind speeds were flagged "unlikely". Wind directions of less than 0 degrees or greater than 360 degrees were flagged "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 NCAR/EOL 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.
Gross limit checks were also used to determine the quality of the precipitation values. The gross limits are shown in Table 3-3. Negative precipitation was flagged "unlikely".
Table 3-3 - Precipitation Gross Limit Values
Parameter Good Questionable Unlikely
--------- ---- ------------ --------
5 Minute Precip < 6.0 mm >= 6.0 mm >= 11.0 mm
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. See Table 3-4 for a list of the possible quality
control flags and their meanings.
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.
Any redistribution of this data must include this data acknowledgment statement.
Any redistribution of this data must include this data acknowledgment statement.
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