Abstract
Agricultural irrigation is an important factor affecting the development of agricultural drought, which is not showed in the Palmer Drought Severity Index (PDSI). In this work, the water balance model in PDSI has been modified by adding irrigation items, which improves the accuracy of the calculation results of the model and shortens the calculation time step. The modified Palmer Drought Severity Index (M_PDSI) is constructed by using daily weather data and irrigation data from 1985-2012 in the study area. Weekly indices cumulated in each growth stage are used for the implementation of crop models by a linear multiple regression model. The crop yield models are evaluated to determine a more appropriate agricultural drought index between M_PDSI and PDSI by comparing the predicted yields to the observed yields. By comparing the development of agricultural drought, it can be seen that the M_PDSI can improve the sensitivity to the dynamic change of soil wet and dry in short-term, and the development process of drought is more in line with the actual situation; by comparing the fitting test results of the predicted yields, it can be seen that, the M_PDSI ranks better than the PDSI in all four goodness-of-fit measures, M_PDSI is proved to be more suitable than PDSI for evaluating agricultural drought.
Highlights
The frequency and severity of droughts have increased over the past decade, causing heavy crop losses and posing a potentially grave threat to grain security, leading agriculture experts warn
Agricultural irrigation, a non-negligible human factor, is a significant factor that might be a marked influence on agricultural drought, as it significantly affects the dynamic of soil moisture
The modified Palmer Drought Severity Index (M_PDSI) and Relative Soil Moisture Drought Index (RSM) values changed from the original negative value to a positive value, indicating the occurrence and mitigation process of the drought, while the Palmer Drought Severity Index (PDSI) described the drought gradually increasing
Summary
The frequency and severity of droughts have increased over the past decade, causing heavy crop losses and posing a potentially grave threat to grain security, leading agriculture experts warn. In 2004, Wells revised the climate traits and drought persistence factors, and established a more adaptive time-space adaptive Palmer Drought Index (SCPDSI) [2]; Kingtse used measured evapotranspiration values, runoff values, and the soil moisture value replaces the calculated value, simplifies the soil moisture model, and establishes M_PDSI [3]. Agricultural irrigation, a non-negligible human factor, is a significant factor that might be a marked influence on agricultural drought, as it significantly affects the dynamic of soil moisture. This cannot be satisfactorily reflected by the PDSI. The performance of the two drought indices are evaluated using four goodness-of-fit measures
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