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Summary
Point data developed from in situ observations at four flux tower sites were combined to produce continuous, above the canopy, meteorological forcing data sets. Data from the OA and OBS sites in the SSA and the Fen and OBS sites in the NSA were used to create continuous time series with a time step of one hour, covering the period from 1-Jan-1994 through 1-Dec-1996.Meteorological variables of interest are surface air pressure, air temperature, dew point temperature, wind speed, wind direction, precipitation, incoming solar (shortwave) radiation, and incoming infrared (longwave) radiation.
This data set was Phase I among three categories of meteorological forcing data sets that have been assembled for BOREAS Hydrometeorological and Carbon Assimilation Model Intercomparison Projects as part of the BOREAS Follow-on activities. Additional meteorological forcing data sets, Phase II and III data, at study area and regional grid scales, respectively, have also been produced.
Data Citation
Cite this data set as follows (citation revised on October 30, 2002):Lettenmaier, D. P., and B. Nijssen. 2001. BOREAS Follow-On HMet-03 Hourly Meteorological Data at Flux Towers, 1994-1996. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.
Table of Contents
- Data Set Overview
- Investigator(s)
- Theory of Measurements
- Equipment
- Data Acquisition Methods
- Observations
- Data Description
- Data Organization
- Data Manipulations
- Errors
- Notes
- Application of the Data Set
- Future Modifications and Plans
- Software
- Data Access
- Output Products and Availability
- References
- Glossary of Terms
- List of Acronyms
- Document Information
1.0 Data set Overview
The data set contains continuous three year, hourly, meteorological time series at selected BOReal Ecosystem Atmosphere Study (BOREAS) tower sites. The data are meant as drivers for model studies. The tower sites are:
Northern Study Area (NSA):
Old Black Spruce (NSA-OBS)
Fen (NSA-FEN)
Southern Study Area (SSA):
Old Black Spruce (SSA-OBS)
Old Aspen (SSA-OA)
1.1 Data set Identification
BOREAS Follow-On HMet-03 Hourly Meteorology
Data at Flux Towers 1994-1996
1.2 Data Set Introduction
Surface station and remote sensing data
sets over BOREAS region were acquired and quality controlled in order to
provide investigators of Hydromet & Carbon Model Subgroups with standardized
meteorological forcing data sets. Data are prepared for period January
1, 1994 through November 30, 1996.
1.3 Objective/Purpose
Although the BOREAS field period covered
a period of about three years (1994-1996), few of the sites operated continuously
during that period. However, most hydrological models require a continuous
meteorological data set to operate. To construct a continuous, hourly time
series of meteorological model forcings, data from a large number of sites
had to be combined.
Data sets were assembled in order to
provide investigators of Hydromet and Carbon Model Subgroups with standardized
meteorological forcing data for model intercomparison studies. Six (6)
different hydrometeorological models and nine (9) different carbon models
were selected for intercomparison purposes.
1.4 Summary of Parameters
The variables included in the data set
are for each tower site:
Variable Units ---------------------------- ----- Time YYYY MM DD HH (UTC) Air Temperature degrees C Vapor pressure deficit Pa Zonal Wind speed m/s Meridional Wind speed m/s Pressure Pa Incoming shortwave radiation W/m2 Incoming longwave radiation W/m2 Precipitation mm/hr1.5 Discussion
This data set is Phase 1 among 3 categories of meteorological forcing data sets that have been assembled for BOREAS Hydrometeorological and Carbon Assimilation Model Intercomparison Projects as part of the BOREAS Follow-on activities. Additional meteorological forcing data sets, Phase II and III data, at study area and regional grid scales, respectively, have also been produced.
1.6 Related Data Sets
BOREAS Follow-on HMet-03 Hourly Meteorology Data at Flux Towers 1994-1996
BOREAS TF-1 SSA-OA Tower Flux, Meteorological, and Soil Temperature
Data
BOREAS TF-2 SSA-OA Tower Flux, Meteorological, and Precipitation Data
BOREAS TF-3 NSA-OBS Tower Flux, Meteorological, and Soil Temperature
Data
BOREAS TF-6 SSA-YA Surface Energy Flux and Meteorological Data
BOREAS TF-8 NSA-OJP Tower Flux, Meteorological, and Soil Temperature
Data
BOREAS TF-9 SSA-OBS Tower Flux, Meteorological, and Soil Temperature
Data
BOREAS TF-10 NSA-Fen Tower Flux and Meteorological Data
BOREAS TF-10 NSA-YJP Tower Flux, Meteorological, and Porometry Data
BOREAS TF-11 SSA-Fen Tower Flux and Meteorological Data
BOREAS AFM-07 SRC Surface Meteorological and Radiation Data
BOREAS HYD-09 Belfort Rain Gauge Data
BOREAS HYD-9 Tipping Bucket Rain Gauge Data
BOREAS Gridded Met Data Over the Hydro-Meteorological Study Area 1994-1996
BOREAS TF-09 SSA OBS Tower Flux, Meteorological, and Soil Temperature
Data
BOREAS AES Campbell Scientific Surface Meteorological Data
BOREAS AES MARSII Surface Meteorological Data
BOREAS AES READAC Surface Meteorological Data
BOREAS TGB-4 NSA-BVP Tower Flux and Meteorological Data
BOREAS HYD-5 Winter Surface Flux Data
BOREAS TF-4 SSA-YJP Tower Flux, Meteorological, and Canopy Condition
Data
BOREAS TE-6 1994 Soil and Air Temperatures in the NSA
2. Investigator(s)
Dr. Dennis P. Lettenmaier, Professor of Civil Engineering
2.2 Title of Investigation
BOREAS surface radiation, energy, water,
and carbon budget variability studies at three different spatial scales
using field measurements, remote sensing, and combination of hydrometeorological
and carbon assimilation models.
2.3 Contact Information
Contact 1:
Bart Nijssen, Research Assistant
University of Washington
Seattle, WA
Fax: (206) 685 3836
E-mail: nijssen@u.washington.edu
Contact 2:
Dr. Dennis P. Lettenmaier, Professor of Civil Engineering
University of Washington
Seattle, WA
Fax: (206) 685 3836
E-mail: dennisl@u.washington.edu
3. Theory of Measurements
- 1st BOREAS Special Issue in 1997 Journal of Geophysical Research (vol 102/issue D24).
- Special Issue on Remote Sensing in BOREAS in 1997 Canadian Journal of Remote Sensing (vol 23/no 2).
- 2nd BOREAS Special Issue in 1999 Journal of Geophysical Research (vol 104/issue D22).
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4. Equipment
5. Data Acquisition Methods
BOREAS Site Id Descriptive Location -------------------------- -------------------- Atmospheric Environment Service (AES) Canada 15 minute continuous stations REG-999-WFF01-STAFF-AES01 Melfort, SK REG-999-WLJ01-STAFF-AES01 Meadow Lake, SK REG-999-WSR01-STAFF-AES01 Spiritwood West, SK SSA-999-WBU01-STAFF-AES01 Nipawin, SK SSA-999-WLV01-STAFF-AES01 Waskesiu Lake, SK Canadian historic stations: daily. NSA-999-THO01-STAFF-HISDY 5062922 - Thompson A, MB REG-999-BRI01-STAFF-HISDY 4060620 - Big River, SK REG-999-CAM01-STAFF-HISDY 4051080 - Cameo, SK REG-999-CHO01-STAFF-HISDY 4071560 - Choiceland, SK REG-999-ETH01-STAFF-HISDY 4052448 - Ethelton, SK REG-999-LRI01-STAFF-HISDY 4074640 - Lost River, SK REG-999-NIP01-STAFF-HISDY 4075518 - Nipawin, SK REG-999-RON01-STAFF-HISDY 4064150 - La Ronge A, SK REG-999-WAB01-STAFF-HISDY 5063041 - Wabowden, MB SSA-999-WSK03-STAFF-HISDY 4068560 - Waskesiu Lake, SK Canadian historic stations: hourly. REG-999-PRA01-STAFF-HISHY 4056240 - Prince Albert A, SK REG-999-RON01-STAFF-HISHY 4064150 - La Ronge A, SK NSA-999-THO01-STAFF-HISHY 5062922 - Thompson A, MB Saskatchewan Research Council Meteorological Stations, suite A, 15 min., late 1993 - Nov 1996 NSA-9BS-YTHSA-AFM07-SRCA1 Thompson Airport, MB (spruce stand) NSA-OJP-FLXTR-AFM07-SRCA1 NSA-OJP Flux Tower, MB REG-999-MDLSA-AFM07-SRCA1 Meadow Lake, SK REG-999-RONSA-AFM07-SRCA1 La Ronge, SK SSA-9OA-FLXTR-AFM07-SRCA1 SSA-OA Flux Tower, SK SSA-OJP-FLXTR-AFM07-SRCA1 SSA-OJP Flux Tower, SK Saskatchewan Research Council Meteorological Stations, suite B, 15 min., early 1994 - Nov 1996 NSA-FEN-FLXTR-AFM07-SRCB1 Nelson House, MB SSA-9OA-FLXTR-AFM07-SRCB1 SSA-OA Flux Tower, SK SSA-OJP-FLXTR-AFM07-SRCB1 SSA-OJP Flux Tower, SK Flux tower sites, 15 min. NSA-BVP-FLXTR-TGB04-FLX01 NSA Beaver Pond Flux Tower NSA-FEN-FLXTR-9TF10-FLX01 NSA Fen Flux Tower NSA-OBS-FLXTR-9TF03-FLX01 NSA Old Black Spruce Flux Tower NSA-OJP-FLXTR-9TF08-FLX01 NSA Old Jack Pine Flux Tower NSA-YJP-FLXTR-9TF10-FLX01 NSA Young Jack Pine Flux Tower SSA-9OA-FLXTR-9TF01-FLX01 SSA Old Aspen Flux Tower SSA-9OA-FLXTR-9TF02-FLX01 SSA Old Aspen Flux Tower SSA-9YA-FLXTR-9TF06-FLX01 SSA Young Aspen Flux Tower SSA-CLR-FLXTR-HYD05-FLX01 HYD-5 Tower Bear Trap Forest SSA-FEN-FLXTR-9TF11-FLX01 SSA Fen Flux Tower SSA-OBS-FLXTR-9TF09-FLX01 SSA Old Black Spruce Flux Tower SSA-OJP-FLXTR-9TF05-FLX01 SSA Old Jack Pine Flux Tower SSA-WAT-FLXTR-HYD05-FLX01 HYD-5 Tower Namekus Lake SSA-YJP-FLXTR-9TF04-FLX01 SSA Young Jack Pine Flux Tower Forestry meteorological stations operating in summer 1994 SSA-999-CND01-STAFF-FRS01 CANDLE LAKE, SK REG-999-COO01-STAFF-FRS01 COOKSON, SK REG-999-EBC01-STAFF-FRS01 EBCAM, SK REG-999-LBE01-STAFF-FRS01 LITTLE BEAR, SK REG-999-WAB01-STAFF-FRS01 WABENO, SK SSA-999-WSK01-STAFF-FRS01 WASKESIU, SK REG-999-WYK01-STAFF-FRS01 WAYAKWIN, SK Forestry meteorological stations operating in summer 1995 SSA-999-CND01-STAFF-FRS01 CANDLE LAKE, SK REG-999-COO01-STAFF-FRS01 COOKSON, SK REG-999-EBC01-STAFF-FRS01 EBCAM, SK REG-999-FLC01-STAFF-FRS01 FORT A LA CORN, SK REG-999-LBE01-STAFF-FRS01 LITTLE BEAR, SK REG-999-WAB01-STAFF-FRS01 WABENO, SK SSA-999-WSK01-STAFF-FRS01 WASKESIU, SK REG-999-WYK01-STAFF-FRS01 WAYAKWIN, SK
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6. Observations
The observations can be subdivided into a limited number of categories based on the data source. For more detailed information the reader is referred to the documentation for the original data sets (all of which are part of the BORIS data archive):
AES 15 minute continuous stations
These stations are long-term meteorological sites operated by Atmospheric Environment Canada, which record observations based on a 15 minute interval. A large suite is variables is measured including windspeed, wind direction, humidity, and pressure. No shortwave or longwave radiation is measured.Canadian historic stations: daily
These stations are also operated by Atmospheric Environment Canada, and only record daily minimum, maximum, and mean temperature and precipitation.Canadian historic stations: hourly
These stations are also operated by Atmospheric Environment Canada, and record observation on an hourly basis. A larger suite of variables is measured than in the daily stations, including windspeed, wind direction, humidity, pressure, and cloudiness. No shortwave or longwave radiation is measured.Saskatchewan Research Council stations
These stations were installed and operated by the Saskatchewan Research Council for the BOREAS project. The stations recorded observations based on a 15 minute interval. This data set provides the most complete coverage (temporally and spatially) of meteorological conditions in the Southern and Northern Study Area during the period 1994-1996. Unlike most flux towers, these stations also operated during the winter months. The stations observed a full set of meteorological observations, although only a limited number measured longwave radiation.Flux tower sites
The largest number of variables was measured at the BOREAS flux tower sites. Most towers measured all basic meteorological data at different levels. All levels have been retained in the quality-controlled data set. Few towers operated during the entire period from 1994-1996.Canadian Forest Service stations
These stations recorded hourly observations in the summers of 1994 and 1995 of air temperature, humidity, wind speed, wind direction, and precipitation.
6.2 Field Notes
Not applicable.
7. Data Description
7.1.1 Spatial Coverage-------------------------------------------------------------------------- Site Id Longitude Latitude UTM UTM UTM Easting Northing Zone -------------------------------------------------------------------------- SSA-OBS-SE501 105.11779° W 53.98717° N 492276.5 5982100.5 13 SSA-9OA-SE501 106.19779° W 53.62889° N 420790.5 5942899.9 13 NSA-OBS-SE501 98.48139° W 55.88007° N 532444.5 6192853.4 14 NSA-FEN-SE501 98.42072° W 55.91481° N 536207.9 6196749.6 147.1.2 Spatial Coverage Map
Not applicable7.1.3 Spatial Resolution
Not applicable7.1.4 Projection
Not applicable.7.1.5 Grid Description
Not applicable
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
Data cover the period from Jan 1, 1994 through Dec 1, 1996.7.2.2 Temporal Coverage Map
Not applicable7.2.3 Temporal Resolution
The temporal resolution is hourly.
7.3 Data Characteristics
7.3.1 Parameter/Variable
The parameters contained in the data files are:Column Name ------------------------------ SITE_NAME DATE_OBS TIME_OBS AIR_TEMP VAPOR_PRESS_DEF U_WIND_SPEED V_WIND_SPEED PRESS SHORT_RAD_IN LONG_RAD_IN PRECIP CRTFCN_CODE REVISION_DATE7.3.2 Description/Definition
The descriptions of the parameters contained in the data files are:Column Name Description ------------------------------ ------------------------------------------------- SITE_NAME The identifier assigned to the site by BOREAS, in the format SSS-TTT-CCCCC, where SSS identifies the portion of the study area: NSA, SSA, REG, TRN, and TTT identifies the cover type for the site, 999 if unknown, and CCCCC is the identifier for site, exactly what it means will vary with site type. DATE_OBS The date on which the data were collected. TIME_OBS The Greenwich Mean Time (GMT) at the beginning of the observation interval. In this data set a backward time tag convention is used (i.e., time tag n indicates data record applies to hourly period n to n+1). AIR_TEMP Air temperature above the canopy VAPOR_PRESS_DEF Vapor pressure deficit above the canopy U_WIND_SPEED Zonal wind speed above the canopy V_WIND_SPEED Meridional wind speed above the canopy PRESS Surface pressure SHORT_RAD_IN Incoming shortwave radiation above the canopy LONG_RAD_IN Incoming longwave radiation above the canopy PRECIP Precipitation CRTFCN_CODE The BOREAS certification level of the data. Examples are CPI (Checked by PI), CGR (Certified by Group), PRE (Preliminary), and CPI-??? (CPI but questionable). REVISION_DATE The most recent date when the information in the referenced data base table record was revised.7.3.3 Unit of Measurement
The measurement units for the parameters contained in the data files are:Column Name Units ------------------------------ ------------------------------------------------ SITE_NAME [none] DATE_OBS [DD-MON-YY] TIME_OBS [HHMM GMT] AIR_TEMP [degrees C] VAPOR_PRESS_DEF [Pascals] U_WIND_SPEED [meters][second^-1] V_WIND_SPEED [meters][second^-1] PRESS [Pascals] SHORT_RAD_IN [Watts][meters^-2] LONG_RAD_IN [Watts][meters^-2] PRECIP [millimeters][hour^-1] CRTFCN_CODE [none] REVISION_DATE [DD-MON-YY]7.3.4 Data Source
The source of the parameter values contained in the data are (see Table 9.2 for detailed information):Column Name Data Source ------------------------------ ------------------------------------------------ SITE_NAME [BORIS Designation] DATE_OBS [Human Observer] TIME_OBS [Various, see section 5] AIR_TEMP [Various, see section 5] VAPOR_PRESS_DEF [Various, see section 5] U_WIND_SPEED [Various, see section 5] V_WIND_SPEED [Various, see section 5] PRESS [Various, see section 5] SHORT_RAD_IN [Various, see section 5] LONG_RAD_IN [Various, see section 5] PRECIP [Hmet-01 Phase 3 data set] CRTFCN_CODE [BORIS Designation] REVISION_DATE [BORIS Designation]7.3.5 Data Range
The data ranges for each variable were not computed for this data set.
7.4 Sample Data Record
The following are wrapped versions of data
record from a sample data file:
SITE_NAME,DATE_OBS,TIME_OBS,AIR_TEMP,VAPOR_PRESS_DEF,U_WIND_SPEED, V_WIND_SPEED,PRESS,SHORT_RAD_IN,LONG_RAD_IN,PRECIP,CRTFCN_CODE, REVISION_DATE NSA-FEN-FLXTR,1-Jan-94,0,-33.11,6.18,2.22,0.04,98837.48,0.03,161.26,0, CPI,27-Dec-00 NSA-FEN-FLXTR,1-Jan-94,100,-34.19,5.48,2.19,-0.27,98837.48,0.02,159.28,0, CPI,27-Dec-00 NSA-FEN-FLXTR,1-Jan-94,200,-33.89,5.52,1.9,0.04,98827.89,0.15,160.01,0, CPI,27-Dec-00
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8. Data Organization
There is one file for each year at each site, from 1994 through 1996.
8.2 Data Format(s)
The files are ASCII, comma-delimited,
one record of data per hour. There are no spaces between the fields.
9. Data Manipulations
9.1 Formulae
Not applicable
9.1.1 Derivation Techniques and Algorithms
Not applicable
9.2 Data Processing Sequence
9.2.1 Processing Steps
After cleaning and aggregating the individual data sites as described in section 6, these individual sites were combined to produce continuous, above canopy, data sets at the tower flux sites.Data processing consisted of the following steps:
- The general procedure for constructing a continuous data set started with the selection of a base data set for each of the variables at each of the flux towers (Table 9.1). This base data set covered as much of the period as possible, and was as complete as possible. In general, if available, SRC data sets were selected for this purpose, otherwise, tower observations were chosen.
Next, correlation and regression equations were calculated between the base variables, and all similar variables at the same and other sites. For example, the above canopy air temperature measured at the SSA-OA SRC site was chosen as the base variable for the above canopy air temperature at the SSA-OA site. This temperature series was then correlated with all other air temperatures within a radius of 250 km, at all levels. That is, the above canopy temperature was correlated with temperatures measured at other levels at the same site, as well as with temperatures at all levels at other sites.- The other data series were then sorted according to decreasing correlation with the base data set, and were used in that order for filling in missing data. Only data series that had more than one hundred points in common with the base data set were used in the filling process (since otherwise the correlation could easily be erroneous). For this reason it is important that the base data set covers as long a period as possible.
- Missing values of air temperature, zonal and meridional wind speeds, pressure and longwave radiation were filled based on the regression equation between the base data sets and the other data sets. Thus
Xnew = a + b * X
where:
Xnew New data value (missing in the base data set) a, b regression coefficients X Value in data set that has the highest correlation with the base data set and that is not missing. Missing values of vapor pressure deficit and shortwave radiation were filled by scaling the value in the "other" data series by the ratio of the means. This was done to prevent the occurrence of negative values, thus
Xnew = M_base/M_other * X
where:
Xnew New data value (missing in the base data set) M_base Mean of the base data set based on those values coincident with the other data set M_other Mean of the other data set based on those values coincident with the base data set X Value in data set that has the highest correlation with the base data set and that is not missing. - The above procedure does not produce satisfactory results for precipitation, since precipitation is not highly correlated between various sites on such short time scales (1 hour). Thus, the precipitation has been taken from the regional data set produced by Valentijn Pauwels. This regional data set covers the entire BOREAS region, and has a spatial resolution of 5' longitude by 10' latitude.
Table 9.2 Base data set used for each variable for each site.Tower Site Variable Base Site Base Variable ------- ----------- ------------------------- ------------------------- NSA-FEN AIR_TEMP NSA-FEN-FLXTR-9TF10-FLX01 air temperature at 7.5 m VAPOR_PRESS_ NSA-FEN-FLXTR-9TF10-FLX01 generated from temperature and DEF relative humidity at 7.5 m U_WIND_SPEED NSA-FEN-FLXTR-9TF10-FLX01 generated from wind speed and wind direction at 6 m V_WIND_SPEED NSA-FEN-FLXTR-9TF10-FLX01 generated from wind speed and wind direction at 6 m PRESS NSA-FEN-FLXTR-9TF10-FLX01 atmospheric station pressure SHORT_RAD_IN NSA-FEN-FLXTR-9TF10-FLX01 downwelling solar radiation at 10.47 m LONG_RAD_IN NSA-FEN-FLXTR-9TF10-FLX01 downwelling longwave radiation at 10.33 m PRECIP Val Pauwels' data set cell 014-052 NSA-OBS AIR_TEMP NSA-OBS-FLXTR-9TF03-FLX01 air temperature at 30 m VAPOR_PRESS_ NSA-OBS-FLXTR-9TF03-FLX01 generated from air DEF temperature and relative humidity at 30 m U_WIND_SPEED NSA-OBS-FLXTR-9TF03-FLX01 generated from wind speed and wind direction (no height specified in NSA-OBS TF03 file) V_WIND_SPEED NSA-OBS-FLXTR-9TF03-FLX01 generated from wind speed and wind direction (no height specified in NSA-OBS TF03 file) PRESS NSA-FEN-FLXTR-9TF10-FLX01 atmospheric station pressure SHORT_RAD_IN NSA-FEN-FLXTR-9TF10-FLX01 downwelling solar radiation at 10.47 m LONG_RAD_IN NSA-FEN-FLXTR-9TF10-FLX01 downwelling longwave radiation at 10.33 m PRECIP Val Pauwels' data set cell 014-052 SSA-OBS AIR_TEMP SSA-OBS-FLXTR-9TF09-FLX01 air temperature at 26 m VAPOR_PRESS_ SSA-OBS-FLXTR-9TF09-FLX01 generated from air DEF temperature at 26 m and vapor pressure at 24 m U_WIND_SPEED SSA-OBS-FLXTR-9TF09-FLX01 generated from wind speed and wind direction at 24 m V_WIND_SPEED SSA-OBS-FLXTR-9TF09-FLX01 generated from wind speed and wind direction at 24 m PRESS SSA-OJP-FLXTR-AFM07-SRCA1 atmospheric station pressure SHORT_RAD_IN SSA-OBS-FLXTR-9TF09-FLX01 downwelling shortwave radiation at 16 m LONG_RAD_IN SSA-OJP-FLXTR-AFM07-SRCB1 downwelling longwave radiation at 35.1 m PRECIP Val Pauwels' data set cell 037-012 SSA-OA AIR_TEMP SSA-9OA-FLXTR-AFM07-SRCA1 air temperature at 23.71 m VAPOR_PRESS_ SSA-9OA-FLXTR-AFM07-SRCA1 generated from air DEF temperature and relative humidity at 23.71 m U_WIND_SPEED SSA-9OA-FLXTR-AFM07-SRCA1 westerly component of the wind speed at 23.71 m V_WIND_SPEED SSA-9OA-FLXTR-AFM07-SRCA1 southerly component of the wind speed at 23.71 m PRESS SSA-9OA-FLXTR-AFM07-SRCA1 atmospheric station pressure at 21.87 m SHORT_RAD_IN SSA-9OA-FLXTR-AFM07-SRCA1 downwelling solar radiation at 23.71 m LONG_RAD_IN SSA-9OA-FLXTR-AFM07-SRCB1 downwelling longwave radiation at 36.83 m PRECIP Val Pauwels' data set cell 041-0059.2.2 Processing Changes
Not applicable
9.3 Calculations
9.3.1 Special Corrections/Adjustments
Since the purpose was to construct an hourly record for the tower flux sites, all data sets were aggregated to an hourly time step. This was done by averaging all observations during a one-hour interval (arithmetic mean). Missing data were not counted in the averaging process. Of course this has the consequence that not all intervals may have included the exact same number of observations (if certain values were missing).
Note: See also section 9, which describes how the continuous data sets were constructed after "cleaning" the individual station files. Some of the variables needed more processing than just quality checking. These additional procedures are discussed below.9.3.2 Calculated Variables
Vapor Pressure Deficit
For sites that reported relative humidity instead of vapor pressure deficit, vapor pressure deficit was calculated based on the temperature and relative humidity at the same level (or as close as possible). If either the temperature or relative humidity were missing for a given time step, the vapor pressure deficit value was set to 'missing'.Zonal and Meridional Wind Speeds
or sites that recorded wind speed and wind direction, wind speed was divided into zonal and meridional components. If no further information was given about the wind direction, the assumption was made that it was measured in degrees from true north. If it was indicated that direction was measured with regard to magnetic north, the appropriate correction was made.Precipitation
All values that were outside reasonable limits were found to correspond to measurement errors. For precipitation, these limits were set to 0 as a minimum, and 200mm as a maximum. See Phase 3 Document (Phase II and III Gridded Meteorological Data set at BOREAS Flux Towers 1994-1996) for more information.Shortwave Radiation
Additional shortwave time series were generated from the daily historic stations operated by the AES Canada. A daily average transmissivity of the atmosphere was calculated based on the difference between the maximum and minimum daily temperatures, and this correction was applied to the top of the atmosphere radiation generated using standard algorithms. Although this will most likely lead to a biased shortwave radiation amount, the methods used for filling in the missing data at the tower flux sites, as explained in section 9, should remove this bias to some extent. This was done only a last resort.Longwave Radiatuon
Longwave radiation was only measured at a limited number of sites in the BOREAS area, and even using all available observations it was not possible to construct a continuous record from observations alone. To augment the record, longwave radiation was calculated from air temperature, humidity, and cloudiness reported by he hourly historic stations operated by AES Canada.
9.4 Graphs and Plots
Not applicable
10. Errors
Errors for any given point or grid position can result from following:
- Measurement errors (systematic and random sensor errors).
- Diurnal cycle was imposed on temperature data by assuming that minimum temperature occurred in hour before sun rise and maximum temperature in afternoon when solar zenith angle increases most rapidly. Second order Hermite polynomials were then fit through these daily minimum and maximum temperatures. Resulting data series then resembles observed diurnal cycle and preserves observed minimum and maximum temperatures.
- No LW observations were available for first 20 days of January-1994 (hour 0 on Jan 1 to hour 20 on Jan 20). These data are filled in from an approximation formula based on air temperature, humidity, and cloud cover at AES hourly sites and then interpolated.
- For December, January and February of each year, on a few occasions, the diurnal cycle was imposed on daily measured precipitation to produce hourly precipitation. Therefore, attention should be given to daily totals rather than hourly totals. Since in winter, precipitation amount is more important than exact time precipitation falls, this source of error is assumed to be acceptable for modeling purposes.
- Winter precipitation is probably on low side. Not only are measurements during this period limited, but measurement of snowfall is generally more problematic than measurement of rainfall.
10.2.1 Data Validation by Source
All the sites were quality checked by first removing obvious outliers, and then a visual check was performed on all the remaining data by plotting the variables. All data points that were obviously problematic were assigned missing values.
In addition the following changes were made:10.2.2 Confidence Level/Accuracy Judgment
- all relative humidity values greater than 100% were set to 100%
- all vapor pressure deficits smaller than 0 were set to 0
- all incoming SW radiation fluxes smaller than 0 were set to 0
None.10.2.3 Measurement Error for Parameters
None given.10.2.4 Additional Quality Assessments
None.10.2.5 Data Verification by Data Center
None.
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11. Notes
See section 10.1 and 11.2.
11.2 Known Problems with the Data
The winter precipitation is probably
on the low side. Not only are measurements during this period limited,
but measurement of snowfall is generally even more problematic than measurement
of rainfall.
Since the individual variables have
been processed independent of each other, it is possible that at certain
times "odd" combinations may occur. It might be worthwhile to attempt and
calculate missing longwave data from the radiation balance when all other
components are available (as has been done by Dr. Alan K. Betts for a site
in the North).
No longwave data were available at the
beginning of January 1994. This data is therefore calculated from cloud
cover, temperature, and humidity at the AES hourly sites, then interpolated.
Care should be taken in using this data.
11.3 Usage Guidance
Care has been taken in constructing
the best data set possible. The data is not "error-free". The user should
thus make sure that the data set is appropriate for his or her modeling
purposes. Please contact "Contact 1" in section 2 if you discover any obvious
problems with the data not mentioned here.
11.4 Other Relevant Information
None.
12. Application of the Data
13. Future Modifications and Plans
14. Software
Custom software was written to manipulate the data files.
14.2 Software Access
The processing software is available
upon request, but may not be of much interest to outsiders. The software
is closely tied to the data format used for the original files (NetCDF).
The final data set is provided in ASCII format.
15. Data Access
These BOREAS data are available from the Earth Observing System Data and Information System (EOS-DIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is:
ORNL DAAC User Services
Oak Ridge National Laboratory
(865) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov
15.2 Procedures for Obtaining Data
BOREAS data may be obtained through the ORNL DAAC World Wide Web site at http://www.daac.ornl.gov/ [Internet Link] or users may place requests for data by telephone or by electronic mail.
15.3 Output Products and Availability
Requested data can be provided electronically
on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs,
8-MM tapes, or diskettes.
16. Output Products and Availability
None.
16.2 Film Products
None.
16.3 Other Products
The three phases of the BOREAS hydrometeorological
model intercomparison forcing data are also available on CD-ROM. Contact
Eric Smith to obtain this set.
17. References
None.
17.2 Journal Articles and Study Reports
Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment
Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94).
Sellers, P., F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96).
Sellers, P., F. Hall, K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94).
Sellers, P., F. Hall, K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96).
Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577.
Sellers, P.J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry,
M. Ryan, K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar,
J. Newcomer, D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D.
Williams, B. Goodison, D.E. Wickland, and F.E. Guertin. 1997. BOREAS in
1997: Experiment Overview, Scientific Results and Future Directions. Journal
of Geophysical Research 102(D24): 28,731-28,770.
17.3 Archive/DBMS Usage Documentation
None.
18. Glossary of Terms
19. List of Acronyms
AES - Atmospheric Environment Service ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CD-ROM - Compact Disk-Read-Only Memory DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System FEN - Fen IFC - Intensive Field Campaign GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center NASA - National Aeronautics and Space Administration NSA - Northern Study Area (BOREAS) OA - Old Aspen OBS - Old Black Spruce ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SSA - Southern Study Area (BOREAS) nbsp; URL - Uniform Resource Locator (a World Wide Web address)
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20. Document Information
20.1 Document Revision Date
Written: 02-Mar-1999Last Updated: 23-Jan-2001 (citation revised on 30-Oct-2002)
20.2 Document Review Date(s)
BORIS Review: 31-Oct-2000Science Review:
20.3 Document ID
hmet03_hourlymet20.4 Citation
Cite this data set as follows (citation revised on October 30, 2002):Lettenmaier, D. P., and B. Nijssen. 2001. BOREAS Follow-On HMet-03 Hourly Meteorological Data at Flux Towers, 1994-1996. Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.
20.5 Document Curator:
webmaster@daac.ornl.gov20.6 Document URL:
http://daac.ornl.gov/BOREAS/FollowOn/guides/hmet03_hourly_met_p1_doc.htmlKeywords
Meteorological forcing
Model forcing
Vapor Pressure Deficit
Zonal Wind Speed
Meridional Wind Speed
Longwave Radiation