Temperature adjustment for reference evapotranspiration calculation in central Arizona

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Abstract

A key component in the calculation of reference crop evapotranspiration (ET,) is the weather data. If the weather data have been collected from a station under nonreference conditions, the data itself may contain errors, which will in turn yield inaccurate ET, estimates. It was proposed by Allen in 1996 that data used for evapotranspiration be scrutinized by comparing daily minimum temperature (Tmin) and the daily average dew point temperature (Tdew). If the difference between Tmin and Tdew is greater than 3°C, then the site is considered to be arid (nonreference) and adjustments are recommended for temperature and dew point data. In Arizona, normal weather conditions often occur where Tmin and Tdew do not approach each other. This study examined the appropriateness of applying the conditions set forth by Allen to temperature data collected in central Arizona. Two weather stations were set up in a 35.5 ha alfalfa field in central Arizona to measure dry bulb and wet bulb temperatures. Additionally, plant temperature data were collected to verify field conditions. Daily data were taken for 1.5 years at the University of Arizona's Maricopa Agricultural Center. Of the 611 days of data collected, the difference between Tmin and Tdew was greater than 3°C on 329 days, indicating that these data were not taken under reference conditions. Among these data, 178 days were verified as nonreference but 151 were verified as actually being under reference conditions. Making adjustments for these days (151 days) resulted in a 47 mm decrease in ET, estimation, which mostly occurred during the summer.

Original languageEnglish (US)
Pages (from-to)384-390
Number of pages7
JournalJournal of Irrigation and Drainage Engineering
Volume130
Issue number5
DOIs
StatePublished - Sep 2004

Fingerprint

Evapotranspiration
evapotranspiration
Weather
dewpoint
Temperature
temperature
meteorological data
bulbs
weather stations
dew point
Medicago sativa
alfalfa
weather
Crops
calculation
summer
crops
weather station

Keywords

  • Alfalfa
  • Arizona
  • Computation
  • Evapotranspiration
  • Temperature
  • Weather data

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Water Science and Technology
  • Civil and Structural Engineering

Cite this

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title = "Temperature adjustment for reference evapotranspiration calculation in central Arizona",
abstract = "A key component in the calculation of reference crop evapotranspiration (ET,) is the weather data. If the weather data have been collected from a station under nonreference conditions, the data itself may contain errors, which will in turn yield inaccurate ET, estimates. It was proposed by Allen in 1996 that data used for evapotranspiration be scrutinized by comparing daily minimum temperature (Tmin) and the daily average dew point temperature (Tdew). If the difference between Tmin and Tdew is greater than 3°C, then the site is considered to be arid (nonreference) and adjustments are recommended for temperature and dew point data. In Arizona, normal weather conditions often occur where Tmin and Tdew do not approach each other. This study examined the appropriateness of applying the conditions set forth by Allen to temperature data collected in central Arizona. Two weather stations were set up in a 35.5 ha alfalfa field in central Arizona to measure dry bulb and wet bulb temperatures. Additionally, plant temperature data were collected to verify field conditions. Daily data were taken for 1.5 years at the University of Arizona's Maricopa Agricultural Center. Of the 611 days of data collected, the difference between Tmin and Tdew was greater than 3°C on 329 days, indicating that these data were not taken under reference conditions. Among these data, 178 days were verified as nonreference but 151 were verified as actually being under reference conditions. Making adjustments for these days (151 days) resulted in a 47 mm decrease in ET, estimation, which mostly occurred during the summer.",
keywords = "Alfalfa, Arizona, Computation, Evapotranspiration, Temperature, Weather data",
author = "X. Jia and Martin, {Edward C} and Slack, {Donald C}",
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AU - Jia, X.

AU - Martin, Edward C

AU - Slack, Donald C

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N2 - A key component in the calculation of reference crop evapotranspiration (ET,) is the weather data. If the weather data have been collected from a station under nonreference conditions, the data itself may contain errors, which will in turn yield inaccurate ET, estimates. It was proposed by Allen in 1996 that data used for evapotranspiration be scrutinized by comparing daily minimum temperature (Tmin) and the daily average dew point temperature (Tdew). If the difference between Tmin and Tdew is greater than 3°C, then the site is considered to be arid (nonreference) and adjustments are recommended for temperature and dew point data. In Arizona, normal weather conditions often occur where Tmin and Tdew do not approach each other. This study examined the appropriateness of applying the conditions set forth by Allen to temperature data collected in central Arizona. Two weather stations were set up in a 35.5 ha alfalfa field in central Arizona to measure dry bulb and wet bulb temperatures. Additionally, plant temperature data were collected to verify field conditions. Daily data were taken for 1.5 years at the University of Arizona's Maricopa Agricultural Center. Of the 611 days of data collected, the difference between Tmin and Tdew was greater than 3°C on 329 days, indicating that these data were not taken under reference conditions. Among these data, 178 days were verified as nonreference but 151 were verified as actually being under reference conditions. Making adjustments for these days (151 days) resulted in a 47 mm decrease in ET, estimation, which mostly occurred during the summer.

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