Hubbard Brook Experimental Forest (US Forest Service): Vapor Pressure Measurements, 1966 - present
TITLE
Hubbard Brook Experimental Forest (US Forest Service): Vapor Pressure Measurements, 1966 - present
PRINCIPAL INVESTIGATOR(s)
John Campbell
USDA Forest Service
271 Mast Rd.
Durham, NH
USA

Phone: (603) 868-7643
OTHERS INVOLVED
Amey Bailey
USDA Forest Service, Hubbard Brook Experimental Forest
234 Mirror Lake Road
North Woodstock, NH 03262
USA

Phone: (603) 726-8902
ABSTRACT:
Hygrothermographs have collected relative humidity at 7 locations within the Hubbard Brook Experimental Forest since 1956. Minimum relative humidity at the time of maximum daily temperature is then converted to vapor pressure. Because vapor pressure varies little throughout a day and among locations, data from all available hygrothermographs were averaged in order to reduce error. Most of the period of record prior to 1981 is not digitally available. Data have only been read from the hygrothermograph charts for three periods: January 1966 to April 1966; June 1967 to Sept. 1967 and; May 1971 to April 1973. However, the entire hygrothermograph chart collection has recently been scanned and prepared for data extraction to fill in gaps in the dataset. Beginning in 1981, a humidity sensor has operated as part of the automatic weather station at Headquarters.
KEYWORD SET: Hubbard Brook Ecosystem Study LTER
climate, forests, HBR, Hubbard Brook LTER, humidity, relative humidity, vapor pressure, weather.
BEGIN DATE
1966-01-01
END DATE
2010-12-31
LOCATION
Headquarters station
West bounding coordinate: -71.700975
East bounding coordinate: -71.700975
North bounding coordinate: 43.945733
South bounding coordinate: 43.945733
Elevation
Minimum: 830
Maximum: 830
(Unit: foot)
DATA DESCRIPTION
Hygrothermographs have operated at Weather Stations HQ (22), 1, 1A, 6, 14, 17, 23 and 24 for the period of their records. Data have only been read from the hygrothermograph charts for three periods prior to 1981: January 1966 to April 1966, June 1967 to Sept. 1967, and May 1971 to April 1973. Beginning in 1981, a humidity sensor has operated as part of the automatic weather station at Headquarters.
SAMPLING DESIGN
The hygrothermographs at Stations HQ(22), 1, 1A, 6, 14, 17, 23 and 24 record relative humidity by sensing the expansion and contraction of a set of horsehairs. The accuracy of their calibration and frequency of maintenance has varied considerably over the years. For a time in the early 1960s, they were not maintained at all. Beginning around 1965 they were calibrated occasionally (less than once a year) by operating in a chamber with saturated salt solutions. Since the 1970s, maintenance and salt calibration has been conducted annually, normally in the spring. Minimum relative humidity at the time of maximum daily temperature was converted to vapor pressure. Because vapor pressure varies little throughout a day and among locations, data from all available hygrothermographs were averaged in order to reduce error. For 1971 - 1973, averaging gave triple weighting to HQ and double weighting to Station 1 to reflect the relative quality of their calibrations.
Beginning in 1981, a humidity sensor has been operated as part of the automatic weather station at Headquarters. This was originally a Brady Array. Brady Array values were corrected by calibration with an Assmann psychrometer. When the weather station blew over on August 1, 1983, this sensor was destroyed and data collection stopped. On April 26, 1985 a Lambda temperature-humidity probe was installed. The humidity sensor has been replaced about annually since then; however, missing data still occur for a variety of reasons. The manufacturer's calibration is used and is checked occasionally with an Assmann psychrometer.
VAPOR PRESSURE COLLECTION PERIODS
The following list includes the start date for each Hygrothermograph. Although they have been operating continuously since their start date, the humidity data needed to calculate vp data have not been read from the charts on a regular basis.
Station 1 -- 1956
Station 1A -- 1958
Station 6 -- 1961
Station 14 -- 1965
Station 22 (HQ) -- 1978
Station 23 -- 1996
Station 17 -- 1999
Station 24 -- 1999
REFERENCES
  • Bailey, A.S., Hornbeck, J.W., Campbell, J.L., and Eagar, C. 2003. Hydrometeorological database for Hubbard Brook Experimental Forest: 1955-2000. Gen. Tech. Rep. NE-305. 36 pp.Newtown Square, PA., U.S., USDA Forest Service Northeastern Research Station.
  • Molloy, J. 2013. An Analysis of the Sublimation at Hubbard Brook Experimental Forest. Masters of Science, Plymouth State University.
DATA ACCESS GUIDELINES
Data Use Policy



The re-use of scientific data has the potential to greatly increase communication, collaboration and synthesis within and among disciplines, and thus is fostered, supported and encouraged. Permission to use this dataset is granted to the Data User free of charge subject to the following terms:

1) Acceptable use. Use of the dataset will be restricted to academic, research, government or other not-for-profit professional purposes.

2) Redistribution. The data and metadata are provided for use by the Data User. The Data User will not redistribute the original Data Set or metadata to others without the explicit permission of the Principal Investigator.

3) Citation. It is considered a matter of professional ethics to acknowledge the work of other scientists. Thus, the Data User will properly attribute the Data Set in any publications or in the metadata of any derived data products that were produced using the Data Set. Citation should take the following general form: Creator, Year of Data Publication, Title of Dataset, Publisher, Dataset identifier.

Citation example: Holmes, R.T. 2012. Bird Abundances at Hubbard Brook (1969-2010) and on three replicate plots (1986-2000) in the White Mountain National Forest. Durham, NH. Hubbard Brook Data Archive [Database]. http://hubbardbrook.org/data/dataset.php?id=81 (23 July 2012)

4) Acknowledgment: The Data User should acknowledge any institutional support or specific funding awards referenced in the metadata accompanying this dataset in any publications where the Data Set contributed to its content. Acknowledgments should identify the supporting party, the party that received the support, and any identifying information such as grant numbers.

Acknowledgment example: Data on [topic] were provided by [name of PI] on [date]. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station, Newtown Square, PA. Significant funding for collection of these data was provided by [agency]-[grant number], [agency]-[grant number], etc.

5) Consultation and questions. Data users are strongly encouraged to consult with the Principal Investigator(s) who collected these data for further information. Also, when appropriate, Data Users should consider including the Principal Investigator as a collaborator and/or co-author in the use of these data.

6) Notification. The Data User will notify the Principal Investigator of any publication or derivative work based on the Data Set. The Data User will also provide the Principal Investigator and/or the administrator of the Hubbard Brook Ecosystem Study with a pdf or two reprints of any publication(s) resulting from use of the Data Set.

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CONTACT PERSON

Information Manager, Hubbard Brook LTER
234 Mirror Lake Road
North Woodstock, NH 03262
USA

Phone: Phone: (603) 726-8902
Email: hbr-im@lternet.edu

Data file: vp.txt
Description: Vapor pressure measurements at the Hubbard Brook LTER. Values are the mean of all vapor pressure data available on the specific date.
Notes on Data: The data is physically located at the USDA Forest Service, Durham, NH and was last updated in 2013.
ColumnVariableDescriptionUnitsCoded?Missing value label
1DATESample dateYYYY-MM-DDnnone
2VPVapor pressurekilopascaln
-99.00
3FLAGFlagnoneynone

CODES

Variable: FLAG
Code
Description
e
Estimated
-99
No flag present

MISSING VALUE CODES
Variable
Missing Value Code
Code Explanation
VP
-99.00
Data missing or not taken