Abstract
This study aims to assess the spatial and temporal variability of reference crop evapotranspiration (ET) over the mountainous Jeju Island, South Korea. In this mountainous region, only limited observed, station-based meteorological data are available, and thus statistical approaches are used to construct monthly reference crop ET maps. The maximum and minimum temperatures, wind speed, and relative humidity are gap filled using principal component regression (PCR) or multiple linear regression (MLR) and are then spatially interpolated using the hybrid Kriging method to construct monthly maps of reference crop ET at a resolution of 100 m. This study reveals various reference crop ET characteristics for Jeju Island that have not been investigated in previous studies. With increasing elevation and distance from the coast, the air temperature decrease and relative humidity (RH) increase. Therefore, the reference crop ET generally decreases. An increasing trend until the mid-2000s is present in the annual average reference crop ET values, and most of this increase arises from increasing trends in spring and summer. Summer reference crop ET values exhibit increasing trends over time below 1000 m a.s.l. and decreasing trends over time above 1000 m a.s.l.
Highlights
Evapotranspiration (ET) is a principal component of the hydrologic cycle, in addition to precipitation and runoff
The monthly reference crop ET values at the sites are estimated based on the observed meteorological data and are evaluated against the observed small pan evaporation data
A comparison between the original and extended data shows that the monthly quartiles are generally similar between the two datasets (Figure 2)
Summary
Evapotranspiration (ET) is a principal component of the hydrologic cycle, in addition to precipitation and runoff. Estimating ET is important for understanding land surface processes from climatological and hydrological perspectives [4]. To understand ET in a given region, it is often necessary to first estimate the potential or reference crop ET values. One can estimate the actual ET rate for a specific crop using estimated reference crop ET values and apply the crop coefficient for the particular crop [5]. Potential ET is defined as the rate at which ET would occur from a large area completely and uniformly covered with growing vegetation that has access to an unlimited supply of soil water in the absence advection or heating effects [6]. The reference surface is a hypothetical grass reference crop with specific
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