Analysis of Agricultural Droughts According to the 2018 Heat Wave in Korea

<p><span>According to the Korea Meteorological Administration, in 2018, Korea's national average temperature and maximum temperature are the highest in 111 years since meteorological observations (1907.10.1.) The highest value was observed since August 1 at </span><span> 39.6 </span>℃ <span>in Seoul. Heatwaves represent the number of days with the highest daily temperature above 33 ° C. The number of heatwaves in 18 years totaled 31.5 days. Heatwaves have a particularly significant effect on the growth and death of field crops. Indeed, 18,254 ha of field crops occurred nationwide. Precipitation in 2018 is higher than normal, but precipitation shortages have occurred due to seasonal and regional variations and local droughts due to the lowest precipitation from mid-July to late August. In particular, there were more rains than normal years at the beginning of farming season (March-May) and the end of farming season (October), but the summer agricultural drought occurred due to less precipitation than the average year-end of July-August. The second shortest rainy season (half of the average year) since 1987 and the rainy season was 72% compared to the average year, some of the reservoirs have caused a serious and severe stage. The country recorded the maximum number of rainfall days on 27th during the period of 7.10 ~ 8.5 days and 43 days on Chungnam. This is believed to have affected the drought occurrence by overlapping with the stage of water-forming, which requires the largest amount of water supply for rice growth. In the case of field crops, irrigation facilities are inferior to paddy fields, so field crop growth is directly related to no rainfall days, and droughts such as deterioration of field crops were recorded nationwide during the maximum rainfall period. Since the end of the rainy season, there have been a total of 22,767 ha droughts, iincluding 2,513 ha of paddy field and 20,254 ha of field crops, due to severe shortages of precipitation and damage to crops caused by heat waves. </span><span>For the 2018 rainfall-based drought frequency analysis, the analysis was based on cumulative precipitation from January to August of 18, and there was a severe shortage of precipitation from mid-July to mid-August, but the cumulative precipitation from January to August is normal. As a result of rainfall-based drought frequency analysis, the drought frequency area was analyzed into two regions for more than 10 years. Based on rainfall in July 2018, drought occurred in most parts of the country due to severe rainfall shortages. For over 200 years, the frequency of drought has been analyzed to 107 counties. As a result of the drought frequency analysis based on the reservoir storage rate in August 2018, there were 45 counties in the drought frequency area for more than 200 years due to the lack of water during the high demand period of rice crop growth period.</span></p><div data-hjsonver="1.0" data-jsonlen="11062"><span>This research was supported by a grant(2019-MOIS31-010) from Fundamental Technology Development Program for Extreme Disaster Response funded by Korean Ministry of Interior and Safety(MOIS).</span></div>

Bayesian Parameter Estimation to Bivariate Drought Regional Frequency Analysis Model: Application to Han-River Watershed

<p>Copula-based bivariate drought frequency analysis has been widely employed to evaluate drought risk in the context of point frequency analysis. However, the relatively significant uncertainties in the parameters are problematic when available data are limited. This study developed a bivariate regional frequency analysis model using Copula function within the Bayesian modeling framework. An experimental study is first performed to assure ourselves whether the proposed model can accurately reproduce drought characteristics. The proposed model is capable of effectively representing the recent drought events and can provide drought risk information along with its uncertainty. The results confirm that the proposed model is not only effectively representing correlation with regional dependencies of drought, but also providing the uncertainty of parameters.</p><p> </p><p>KEYWORDS: Copula, Bayesian, Bivariate drought regional frequency analysis, Uncertainty</p><p> </p><p>Acknowledgement</p><p>This work was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI 2018-07010.</p>

Extremeness of recent drought events in Switzerland: dependence on variable and return period choice

The 2018 drought event had severe ecological, economic, and social impacts. How extreme was it in Switzerland? We addressed this question by looking at different types of drought, including meteorological, hydrological, agricultural, and groundwater drought, and at the two characteristics deficit and deficit duration. The analysis consisted of three main steps: (1) event identification using a threshold-level approach, (2) drought frequency analysis, and (3) comparison of the 2018 event to the severe 2003 and 2015 events. In Step 2 the variables precipitation, discharge, soil moisture, and low-flow storage were first considered separately in a univariate frequency analysis; pairs of variables were then investigated jointly in a bivariate frequency analysis using a copula model for expressing the dependence between the two variables under consideration. Our results show that the 2018 event was especially severe in north-eastern Switzerland in terms of soil moisture, with return periods locally exceeding 100 years. Slightly longer return periods were estimated when discharge and soil moisture deficits were considered together. The return period estimates depended on the region, variable, and return period considered. A single answer to the question of how extreme the 2018 drought event was in Switzerland is therefore not possible – rather, it depends on the processes one is interested in.

Extremeness of recent drought events in Switzerland: dependence on variable and return period choice

The 2018 drought event had severe ecological, economic, and social impacts. How extreme was it in Switzerland? We addressed this question by looking at different types of drought, including meteorological, hydrological, agricultural, and groundwater drought, and at the two characteristics deficit and deficit duration. The analysis consisted of three main steps: (1) event identification using a threshold-level approach, (2) drought frequency analysis, and (3) comparison of the 2018 event to the severe 2003 and 2015 events. In Step 2 the variables precipitation, discharge, soil moisture, and low-flow storage were first considered separately in a univariate frequency analysis; pairs of variables were then investigated jointly in a bivariate frequency analysis using a copula model for expressing the dependence between the two variables under consideration. Our results show that the 2018 event was especially severe in north-eastern Switzerland in terms of soil moisture, with return periods locally exceeding 100 years. Slightly longer return periods were estimated when discharge and soil moisture deficits were considered together. The return period estimates depended on the region, variable, and return period considered. A single answer to the question of how extreme the 2018 drought event was in Switzerland is therefore not possible – it rather depends on the processes one is interested in.