Spatiotemporal variation of drought characteristics in the Huang- Huai-Hai Plain, China under the climate change scenario

Understanding the potential drought characteristics under climate change is essential to reduce vulnerability and establish adaptation strategies, especially in the Huang-Huai-Hai Plain （3H Plain）, which is a major grain production area in China. In this paper, we investigated the variations in drought characteristics （drought event frequency, duration, severity, and intensity） for the past 50 years （1961-2010） and under future scenarios （2010-2099）, based on the observed meteorological data and the Representative Concentration Pathway （RCP） 8.5 scenario, respectively. First, we compared the applicability of three climatic drought indices： the standardized precipitation index （SPI）, the standardized precipitation evapotranspiration index based on the Penman-Monteith equation （SPEI-PM） and the same index based on the Thornthwaite equation （SPEI-TH） to correlate the recorded agricultural drought areas. Then, we analyzed the drought characteristics using ＇run theory＇ for both historical and the future RCP 8.5 scenario based on the best performing index. Correlation analyses between drought indices and agricultural drought areas showed that SPEI-PM performed better than SPI and SPEI-TH in the 3H Plain. Based on the results of SPEI-PM, drought risks including duration, severity and intensity during 1961-2010 showed an decreasing trend. However, under the RCP 8.5 scenario, drought is expected to rise in frequency, duration, severity, and intensity from 2010-2099, although drought components during the 2010-2039 are predicted to be milder compared with historical conditions. This study highlights that the estimations for atmospheric evaporative demand would create differences in the prediction of long-term drought trends by different drought indices. The results of this study can help inform researchers and local policy makers to establish drought management strategies.

Spatio-Temporal Analysis of Drought in the North-Eastern Coastal Region of Vietnam Using the Standardized Precipitation Index (SPI)

Spatio-temporal analysis of drought provides valuable information for drought management and damage mitigation. In this study, the Standardized Precipitation Index at the time scale of 6 months (SPI-6) is selected to reflect drought conditions in the North-Eastern coastal region of Vietnam. The drought events and their characteristics from 1981 to 2019 are detected at 9 meteorological stations and 10 Chirps rainfall stations. The spatio-temporal variation of drought in the study region is analyzed on the basis of the number, duration, severity, intensity, and peak of the detected drought events at the 19 stations. The results show that from 1981 to 2019 the drought events mainly occurred with 1-season duration and moderate intensity and peak. The number, duration, severity, and peak of the drought events were the greatest in the period 2001-2010 and were the smallest in the period 2011-2019. Among the 19 stations, the drought duration tends to decrease at 11 stations, increase at 7 stations, and has a slight variant at 1 station;the drought severity tends to decrease at 14 stations, increase at 4 stations, and has not a significant trend at 1 station;the drought intensity tends to decrease at 17 stations, increase at 1 station, and has a slight variant at 1 station;and the drought peak tends to decrease at 18 stations and increase at 1 station.

Assessment of Hydrological Drought Using the Standardized Streamflow Index (SSFI): A Case Study of the Tien Yen River Basin of Quang Ninh Province, Vietnam

Probabilistic assessment of drought plays an important role in providing valuable information for evaluating water resources systems under drought conditions, and bivariate copulas are effective and efficient for the probabilistic assessment of drought based on joint distributions and/or joint return periods of drought characteristics. In this study, hydrological drought events and their characteristics (including duration and severity) in the Tien Yen River Basin of Quang Ninh province are detected using the Standardized Streamflow Index (SSFI). The BB8Copula is selected as the best-fit copula for hydrological drought duration and severity. Joint probabilities and joint return periods of drought duration and severity in the cases “and” and “or” are calculated based on the BB8Copula, which are employed for drought assessment. The results show that the drought events with 1-season or cross-quarter duration were more popular than others;joint probabilities and joint return periods of the detected drought events from 1962 to 2009, ranged from 0.2% to 92.2% and from 0.782 years to 315.414 years, respectively, in the case “and”, and ranged from 3.8% to 99.6% and from 0.724 years to 18.785 years, respectively, in the case “or”.

Shoot and root traits in drought tolerant maize(Zea mays L.) hybrids

This study aimed to investigate the differences in shoot and root traits, and water use and water use efficiency（WUE） in drought tolerant（DT） maize（Zea mays L.） hybrids under full and deficit irrigated conditions. A two-year greenhouse study was conducted with four hybrids（one conventional hybrid, 33D53AM, two commercial DT hybrids, P1151 AM, N75H, and an experimental hybrid, Exp HB） grown under two water regimes（I（100） and I（50）, referring to 100 and 50% of evapotranspiration requirements）. Under water stress, the hybids P1151 AM, N75, and Exp HB showed more drought tolerance and had either greater shoot dry weight or less dry weight reduction than the conventional hybrid（33 D53 AM）. However, these three hybrids responded to water stress using different mechanisms. Compared with the conventional hybrid, the two commercial DT hybrids（P1151 AM and N75H） had a smaller leaf area, shoot dry weight, and root system per plant. As a result, these hybrids used less water but had a higher WUE compared with the conventional hybrid. In contrast, the experimental hybrid（ExpHB） produced more shoot biomass by silking stage at both irrigation levels than all other hybrids, but it had relatively lower WUE. The hybrids demonstrated different drought response mechanisms that may require different irrigation management strategies. More investigation and validation are needed under field conditions and in different soil types.

ANALYSIS ON EFFECT OF SOUTH ASIA HIGH ON MID-SUMMER EXTREME DROUGHT AND FLOOD IN SICHUAN-CHONGQING REGION

NCEP/NCAR data are utilized to analyze an extreme flood year(1998) and an extreme dry year(2006) in the Sichuan-Chongqing region(SCR) and the results are as follows. The positive divergence of South Asia High(SAH) is stronger in the flood year; the position of the ridge line of SAH is southward compared with the annual average; Western Pacific Subtropical High(WPSH) extends westward and its ridge line is southward. In the drought year, the positive divergence of SAH is weaker, its ridge line is northward, and the position of WPSH is also northward. As shown in the dynamics, in drought(flood) years, negative(positive) vorticity advection in the upper atmosphere can cause the atmosphere to ascend(descend), and anomalous circulation of SAH displays divergence(convergence), and anomalous circulation of the lower atmosphere shows convergence(divergence). Thermal structure of the atmosphere shows that there is warm(cold) temperature advection in the lower atmosphere, and the vertical distribution of diabetic heating causes SAH's local circulation to display convergence(divergence) and affects vertical motion of the lower atmosphere circulation eventually. To some extent, the two extreme years in the SCR is closely related to the vertical motion of atmosphere circulation and the variation of such vertical motion is caused by differences of interactions between SAH and lower atmosphere circulations.

Effects of Irrigation on Soil and Wheat Yield under Drought Conditions in Sichuan

In order to study the effective water-saving cultivation of wheat in Sichuan under drought conditions to reduce grain loss,the effects of different irrigation methods（ natural rainfall,artificial irrigation,and infiltrating irrigation） on soil physical characteristics and main agronomic characters and yield of wheat were analyzed. The results showed that different irrigation treatments at different growth stages had different effects on soil physical characteristics and agronomic characters of wheat. At the seedling and jointing stage,there were small differences between the treatments in soil compactness,soil bulk density,and soil water content. At the flowering and maturation stage,different irrigation treatments had great impacts on soil compactness,soil bulk density,soil water content,and agronomic characters of wheat. In the hilly areas of Sichuan Basin,infiltrating irrigation at the jointing stage was the best,and wheat yield increased significantly,2 113. 46 kg/hm^2 higher than that in the control.

茉莉酸甲酯处理的油用牡丹干旱下的光合及生理特性

以油用牡丹‘凤丹’为材料,整株喷施4种浓度(50、100、200、400μmol/L)的茉莉酸甲酯(MeJA),以喷施清水处理为对照(CK),连续喷施3 d后进行干旱处理再复水,在‘凤丹’到达中度、重度干旱2 d及复水2 d后取样,测定‘凤丹’叶片的渗透调节物质含量、丙二醛(MDA)含量、光合色素含量,同时对光合指标进行测定。结果表明:200μmol/L MeJA处理后,中度干旱的‘凤丹’幼苗的脯氨酸含量最高,较CK显著提高250.34%,净光合速率、气孔导度和蒸腾速率最大,较CK分别提高25.73%、68.0%、43.04%;‘凤丹’的叶绿素a、叶绿素b和类胡萝卜素含量在400μmol/L MeJA处理下达到最高,较CK分别提高了33.33%、26.09%、34.48%;喷施200μmol/L MeJA后,重度干旱的‘凤丹’幼苗可溶性糖含量达到最大值,净光合速率最大,较CK提高了41.73%;蒸腾速率和胞间CO;浓度在400μmol/L Me JA处理下最高,分别较CK提高了74.07%和13.44%;复水后,适宜浓度的MeJA处理使光合生理指标均得到不同程度的恢复。表明外源MeJA处理能增强‘凤丹’幼苗对干旱的抵抗能力,提高‘凤丹’幼苗的光合速率、光合色素和渗透调节物质含量,降低干旱对细胞膜的损伤,以200μmol/L MeJA处理效果最佳。