Evaporation pan data beginning 1983 - Jornada LTER Weather Station

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Surface evaporation is measured weekly to twice weekly using an evaporation pan compatible with standard National Weather Service evaporation measurements. Measurements are made twice per week during hot periods because of high evaporation rate. The following data is collected: number of days between measurements, beginning and ending measurement period, current, minimum, and maximum water temperature; initial water level; final water level; rainfall since last evaporation measurement, and calculated evaporation (inches).

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field data sheets

Temperature readings are taken with submerged U-shaped max/min thermometer placed in evaporation pan on south side to maximize shade. Max/min values are reset using magnet kept at pan. A micrometer hook gage is used to measure initial water level and final water level (after evaporation). Total rainfall since last reading is obtained from adjacent standard rain gauge for which rainfall is recorded after each event. Data is recorded on data sheets and, beginning 11 June 2011, entered using KeyesPunch Data Entry software. This data is appended to a Microsoft Excel file, evap-pan.xls. The variables interval_days and begin_period are calculated and determined, respectively, once in the Excel file. The evaporation is calculated based on evaporation period determined by begin_period and data_read dates. Calculated evaporation is (i-water minus f-water). A comma-separated-file (CSV) is generated for final output. Quality assurance (QA): Beginning 11 June 2011, entries are validated based on acceptable values during data entry. The Quality Flag is autogenerated based on entries and visually checked. Data is verified using double-entry method with KeyesPunch Data Entry software. Prior to this, verification was a visual check after data was entered into an Excel spreadsheet.

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Pan water evaporation is calculated in early years within LOTUS 123 spreadsheet. Later years use Microsoft Excel. Evaporation = (initial H2O level + rainfall - final H2O level) A quality flag is assigned to each data record.

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Evaporation pan location: 12 Jul 83 Approximately 1/2 mile S from Jornada LTER to Weather Station about 100 meters downslope 10 Oct 91 from LTER-II C-CALI Lizard Pitfall grid within 10 meters of road leading up to powerline and within creosotebush zone. 10 Oct 91 Relocated to Jornada LTER Weather Station to which is located about 1/2 mile SE of NMSU Present College Ranch Headquarters in mixed-forb and grassland area about 200m from creosotebush transition zone. Rain gauge location: 12 Jul 83 Approximately 1/2 mile SE of NMSU College to Ranch Hdqr at LTER Upper Trailer (Graduated rain 07 Jul 92 gage) 08 Jul 92 Standard Can Gage at Jornada LTER Weather to Station. Present


weekly to twice per week

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