Submitted to: International Evapotranspiration Irrigation Scheduling Conference
Publication Type: Proceedings
Publication Acceptance Date: April 12, 1996
Publication Date: N/A
Technical Abstract: Automated agricultural weather stations often use naturally aspirated radiation shields for the air temperature and relative humidity sensors. A study was undertaken to compare a standard cotton belt shelter (CBS) widely used in the U.S. for manual weather observations with a naturally aspirated shield (NAT) and a forced aspirated (ASP) shield with the same type temperature and relative humidity sensor. Both the ASP and NAT shields ha temperatures about 1.8 to 2.1 deg C higher than observed in the CBS shield, but both were linearly correlated to CBS measurements with a slope near unity. Relative humidity indicated only about a 1.5% RH difference between the shields. The NAT and ASP shields affected temperatures enough to bias maximum daily air temperatures by 1.5 deg C (or about 8%), computed reference evapotranspiration by 0.6 mm d**-1 (or about 11%), or growing degree days (GDD) by 1 deg C-d. These differences are large enough to warrant a more thorough study of radiation shelters used in automated agricultural weather stations. These differences could significantly affect reliability of such data for irrigation scheduling or crop growth modeling purposes.