Effect of Environmental Measurement Uncertainty on Prediction of Evapotranspiration

Ling-Hsi Chen,Jiunyuan Chen,Chiachung Chen

doi:10.3390/atmos9100400

Abstract

Evapotranspiration (ET) is a typical biological environmental process to influence leaf temperature, crop water requirement, and greenhouse microclimate. Affecting factors of ET include air temperature, air relative humidity, wind speed, solar radiation, longwave radiation, soil moisture, CO2 concentration, and crop state. In this study, two ET models of indoor cultivation commonly adopted in literature were selected to evaluate the effect of the performance of sensors on the model uncertainty. The method of the International Organization for Standardization, Guides to the expression of Uncertainty in Measurement (ISO GUM) was adopted. The result indicated that the performance of leaf area index (LAI) and solar radiation (Is) sensors were primary sources of uncertainty. The uncertainty of ET models due to sensor performance needs to be considered. To ensure the predictive ability for applying the ET model for crops irrigation management and greenhouse environmental control, the improvements in the measurement of environmental variables for calculating ET would be of particular importance. The method of this study can be used for evaluating the uncertainty of ET models that calculate ET based on environmental variables measured by meteorological sensors or the remote sensing technique.

Highlights

IntroductionThe proper management of irrigation is important for field and greenhouse cultivation
The proper management of irrigation is important for field and greenhouse cultivation.The accurate estimation of crop water requirements can provide the information needed to avoid the water stress caused by soil moisture excess or deficit [1].Two measurement techniques, direct and indirect, are used to estimate evapotranspiration (ET)values in greenhouses [2,3,4,5]
Direct methods include weights measured by lysimeter, soil/substrate volumetric water content measured by dielectric sensors, soil/substrate water potential detected by tension meters, and sap flow measured by gauges

Summary

Introduction

The proper management of irrigation is important for field and greenhouse cultivation. The indirect method consists of calculating ET from a model that is based on environmental variables measured by meteorological sensors or the remote sensing technique [4,5]. The ET value represents the water loss from the soil or substrates and plant surfaces It provides important information for water management for open fields or the greenhouse. Heterogeneity, and temporality, the validation technique of the biological model is incomplete [26] Other uncertainly sources, such as temporal and spatial effects, the reference standard, the model concept, and the performances of sensors need to be further studied. The GUM established from the ISO [27] and ISO/the International Electrotechnical Commission (IEC ) [28] proposed the propagation concept of uncertainty to describe the uncertainty factors This technique could be extended to the biological model. Two ET models were used to study uncertainty factors and evaluate the effect of the sensor performance on uncertainty

Evaluation of Model Uncertainty for Two ET Models

Results

Discussion

Conclusions