Wind‐induced splash in Class A evaporation pan

Abstract

[1] This study investigates the wind-induced splash in the Class A evaporation pan through a series of wind tunnel experiments. The experimental results revealed that high wind speed can generate seiche wave inside the pan and splash water out of the pan in several minutes. The splash loss increases as the wind speed increases, and the loss rate is at least one order of magnitude greater than the evaporation rate. In other words, the water loss from the pan is not entirely due to evaporation, and the evaporation rates under high wind speeds are over-estimated. By checking the wind speeds and evaporation rates from a four-year (2004)(2005)(2006)(2007)(2008) field observation collected in northern Taiwan, it is found that the hourly evaporation rate was unusually high when wind speed was larger than 7 m s À1. The splash-out criterion is set as: hourly average wind speed U ≥ 7 m s À1 and evaporation rate E > 1.64 mm hr À1. The ratio of the splash-out to the average evaporation rate is 0.75% at this site. In addition, this study examines the influence of the initial water depth in the pan on the evaporation rate. The results demonstrate that, because of the shelter effect caused by the rim of the pan, the evaporation rates for water depth less than 8 cm are lower than that of standard water depth (20 cm) when wind speed U = 4 and 6 m s À1. However, the shelter effect becomes insignificant when wind speed was U = 2 m s À1 .

Identification of Parameters of Evaporation Equations Using an Optimization Technique Based on Pan Evaporation

“…According to him, pans that are installed in a way that represent the actual field conditions might produce accurate results, whereas the Class A Pan and other standard pans in use usually provide slightly inaccurate measured evaporation. Tanny et al [26] and Chu et al [27] conducted research related to the Class A evaporation pan and found that it is the least accurate method of measuring and estimating evaporation. All such limitations must be considered while dealing with evaporation estimates.…”

Daily pan-evaporation estimation in different agro-climatic zones using novel hybrid support vector regression optimized by Salp swarm algorithm in conjunction with gamma test

“…Low air humidity or less water vapor in the air allows more evaporation. Higher wind speed sweeps away more water from the waterbody to the atmosphere (Chu et al, 2012). Therefore, all these climatic factors significantly influence EP in any region.…”

Spatial variations and long-term trends of potential evaporation in Canada

“…A potential source of the difference could be the errors of the E pan data, including some extremely high values (Fig. 2 ), which are caused by multiple factors, such as intensive rain, high wind speeds 32 , and errors introduced while taking readings 33 , 34 . Also, K pan (0.77) used for E pan correction in this study is likely too small for some ecozones.…”