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Evapotranspiration Data


Methods for Collecting Evapotranspiration Data

DESCRIPTION OF DAILY PAN ET FILE:

The file of pan Et at the Ing site contains daily rainfall and Et for the period April 27, 2001 through September 30, 2003. Both rain and Et are daily totals, in inches. The file contains:

Date: day/month/year
Rain: Total rain for the day, in inches
Et_pan: Total pan Et, in inches

DESCRIPTION OF 15-MINUTE BOWEN-RATIO SITE DATA FILES:

Average values are for the 15-or-30-minute period ending at the indicated time. All vapor-pressure and temperature gradient data (de and dt) are averages for 30-min periods, even though they are given at 15-minute intervals at most sites.

Date_time: The date and clock time of day (day/month/year hour:minute). All times are Eastern Standard Time. This combined Date_time field should import into most spreadsheet and data analysis applications as the appropiate date-time variable.
depth: The average depth of water at the site, in feet above land surface. Negative values indicate depth of water below land surface. At some sites, depths were estimated by interpolation during periods of sensor malfunction.
rain: The rainfall total, in inches.
winds: The average wind speed, in miles/hr.
windd: The average wind vector direction, in degrees clockwise from north.
pyro: The intensity of incoming solar radiation, in watts/square meter, measured with LX-200 pyranometers (Licor, Inc.)
nr: The net solar radiation, in watts/square meter, measured with Q7.1 radiometers (REBs, Inc.). This sensor measures the difference between incoming (solar and atmospheric ), and outgoing (reflected and longwave) radiation.
shf: The average soil-heat flux, in watts/square meter.
tair: The average air temperature, in degrees Celsius.
rh: The average relative humidity, in percent.
de: The average gradient in vapor pressure, in kilopascals/meter. At all sites except the open-water sites (sites 2 & 3), the gradient is measured between two sensors separated a vertical distance of about 1 meter, with the lower sensor about 1 meter or more above the top of the vegetative canopy. At open water sites (sites 2 & 3), the gradient is measured from the water surface to a sensor positioned about 2 meters above the water surface. All de measurements are for 30-min intervals, even though they are given at 15-minute intervals for most sites. The gradients are calculated by subtracting the lower-sensor measurement from the upper-sensor measurement, so that a positive gradient indicates increasing vapor pressure with height.
dt: The average gradient in air temperature, in degrees Celsius/meter. These gradients are measured using temperature sensors co-located with the vapor-pressure sensors. All dt measurements are for 30-min intervals. The gradients are calculated by subtracting the lower-sensor measurement from the upper-sensor measurement, so that a positive gradient indicates increasing air temperature with height.
wts: The average water temperature, in degrees Celsius, at the water surface, measured with a float-mounted sensor. Water temperatures are not given when water level is below land surface.
wtm: The average water temperature at a fixed position 1-2 feet above land surface.
(This was not recorded at most stations).
wtb: The average water temperature at the water/land interface.
Water temperatures are not given when water level is below land surface.
Et_edit: The cumulative evapotranspiration (Et), in inches, for the reporting period. Some of these values have been edited to eliminate possible unrealistic values. The Et given in each row is the total Et since the last reporting period. A no-value indicator (-999) is listed for times within the Et-reporting period. To obtain an Et sum for a period using a spreadsheet or other software will require replacement of the no-value indicators with 0 or a missing-value indicator.
Et_raw: This column is identical to the Et_edit column except that no editing has been done. Data values are measured if input data passed all screening criteria, or are calculated for the Priestley-Taylor site model if the criteria are not met.
Flag: The type of Et value indicator. Flag is 0 if the Et value is a measured value that passed all screening criteria. The Flag value is 1 if the Et value is from a site model rather than an actual measurement.

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Last updated: 15 January, 2013 @ 12:42 PM(TJE)