Occurrence Of Dry Years Research Articles

The impact of selected agrotechnical treatments on the growth of wild garlic (Allium ursinum L.) leaves in field cultivation

Wild garlic (Allium ursinum L.) is a typical spring geophyte whose natural habitat is beech forests. The research aimed to assess the possibility of cultivating wild garlic in field conditions significantly different from those required by this plant, using environmentally friendly and unconventional treatments. This study aimed to evaluate the effect of selected agricultural practices (catch crop, shading plant, biopreparations) on the growth of wild garlic leaves grown in the field. The results show that the biomass of catch crops and shade plants and biopreparations from marine algae are justified in cultivating wild garlic in field conditions regarding the leaf yield. Ploughing of phacelia biomass on a catchment soil with an unstable structure positively affected the growth of wild garlic, increasing the length of leaves, their number, and the length and width of the leaf blade. Winter turnip rape used as a shade plant caused an increase in the length of the leaves and the value of the FV/FM index (the quotient of the variable fluorescence to the maximum fluorescence), and also, depending on the year of the study, the length and width of the garlic leaf blade. Soaking the bulbs before planting in the ‘Kelpak SL’ solution increased the number of garlic leaves growing without turnip rape cover in the second and third years of cultivation. In the first year of vegetation, longer leaves with a larger leaf blade ensured the preparation was sprayed three times without pre-soaking the bulbs. Considering the biopreparations’ positive effect on the growth of garlic leaves and the FV/FM ratio values, their use is prospective regarding the increasing occurrence of dry years and is an alternative to plant irrigation.

Prediction of bimodal monsoonal rainfall in the central dry zone of Myanmar using teleconnections with global sea surface temperatures

In the central dry zone of Myanmar, the mean annual rainfall is less than 1000 mm. Although rainfed agriculture is commonly practiced there, the feasibility of rainfed farming is compromised by the large fluctuations of rainfall and the frequent occurrence of dry years. The monthly distribution of rainfall follows a bimodal pattern. The intensity of the monsoonal rainfall from May to October is characterized by two peaks, an early peak (May-June) and a late peak (August–October), separated by the inter-monsoon (July). The return times of dry and wet years make management of rainfed agriculture problematic. There is very little correlation between the early and late monsoonal rainfall (r=–0.257). However, monsoonal rainfall is teleconnected to sea surface temperatures (SSTs) in certain areas of the Pacific Ocean in real time. Furthermore, at lag times of 6–9 months, there are teleconnections between the early monsoonal, inter-monsoonal, and late monsoonal rainfall and SSTs in certain areas of the Indian Ocean and Atlantic Ocean. We used an Elman artificial neural network model to predict early monsoonal, inter-monsoonal, and late monsoonal rainfall based on teleconnections with SSTs in the Indian and Atlantic oceans 6–9 months before the rainfall occurred. The correlation coefficient between the predicted and observed rainfall exceeded 0.7 in all three cases.

Evaluation of Linear and Machine Learning Models for Determining Pedotransfer Functions

Modelling of water content and the transport of water in soil has become a useful tool in simulating agricultural productivity or in solving various hydrological analyses. For instance, optimum irrigation management requires a systematic estimation of the soil-moisture to determine both the appropriate amount and timing of irrigation. Soil characteristics appear as an essential input in the numerical simulation of a soil-water regime. A critical physical property used in the description of a soil-water regime in such modelling is a soil water retention curve. This paper aims to evaluate so-called pedotransfer functions, which helps to assess the soil water retention curve easier than by standard complex and lengthy procedure involving both field and laboratory work. As a case study Zahorska Lowland, which is located in central Europe in the western part of Slovakia, was selected. The frequent occurrence of dry years in this area results in the necessity to construct irrigation systems in this area, so modelling water content in the soil is an important task here. This study aims to support such modelling with determining pedotransfer functions. Authors compare linear methods (multiple linear regression, LASSO regularized regression) and CatBoost machine learning model.

Impact of climate change on water availability and its propagation through the Western U.S. power grid

Climate change is expected to affect the availability of water for electricity generation, yet the propagation of climate impacts across a large and diverse power grid remains unexplored. In this study, we evaluate how projected changes in water availability affect electricity generation at hydroelectric and thermal power plants and how the coincident impacts propagate locally and throughout the interconnected power grid of western United States. We also evaluate whether the prospect of climate-driven change could affect regional power dependencies. Hydrologic simulations derived from three Global Circulation Models (CCSM4, INMCM4, and GFDL-CM3), two radiative scenarios (RCP4.5 and RCP8.5) and the VIC hydrology model are used to force a large-scale, distributed water management model (MOSART-WM), which translates water availability into power generation constraints at hydropower plants and water-dependent thermoelectric plants. Power system dynamics are evaluated using the production cost model PLEXOS. We find that the interregional connections across the contemporary Western U.S. electricity infrastructure play an essential role in managing variations in regional generation due to hydrological variability. Projected WECC-scale changes in mean annual precipitation ranging from −3.8% to +17% are moderated to −6% to +4% in mean annual production cost changes. Climate change impacts on water availability in the Northwest drive future changes in other regions’ generation and in regional power flows. Northwest total generation influences interannual variability in other regions’ net generation, explaining about 40%, 50%, and 35% of the variability in Southwest, Rockies, and Southern California regions respectively. The propagation of Northwest climate change impact throughout the grid is exacerbated by the occurrence of dry years in Northern California. Generation from the Desert Southwest emerges as a critical resource to compensate for variations in water availability, and generation, in these regions. Though the regional power flow directions seem insensitive to long-term variations in water availability, our analysis highlights the need to consider other compounding regional factors, such as changes in Southern California’s net load and changes in regional fuel prices.

Uncertainties of the rainfall regime in a tropical semi-arid region: the case of the State of Ceará

The rural population of a tropical semi-arid region such as the northeast of Brazil is directly dependent on rainfall for agricultural production, pasture for livestock, and the storage of drinking water for human consumption. The region is characterised by the frequent occurrence of dry years and consecutive dry days (CDD) during the rainy season, demonstrating the vulnerability of rainfed agriculture. The aim of this study therefore, was to identify homogeneous regions of the State of Ceará where there is greater or lesser uncertainty of the rainfall regime. Accordingly, the occurrence of dry and very dry years were investigated as uncertainties between years, together with the occurrence of two classes of CDD (10-20 and 21-30 days) during the rainy season. To define similar regions as to the uncertainty of the rainfall regime, the technique of Hierarchical Cluster Analysis (HCA) was used. The study considered time series of least 30 years, from 77 rain gauge stations around the state of Ceará. The use of HCA resulted in the formation of seven homogenous groups in both of the phenomena being investigated. Municipalities in the Central Backlands, the Inhamuns Backlands and the Jaguaribana Region displayed a higher frequency of both inter-annual (dry years) and intra-annual (CDD) uncertainty, demonstrating the greater vulnerability of rainfed agriculture. The occurrence of a CDD event is not dependent on the total annual rainfall, as several stations with an average rainfall higher than that of the state showed potential for the occurrence of CDD. The number of CDD events recorded in the 11-20 day class was higher than in the 21-30 day class.

Regional extreme climate events on the northeastern Tibetan Plateau since AD 1450 inferred from tree rings

Qilian juniper ( Juniperus przewalskii Kom.) is a widely distributed tree species growing on south-facing slopes in the northeastern Tibetan Plateau in arid northwestern China. We established a tree-ring width network based on two new chronologies and four previously published chronologies. Correlation and response function analyses demonstrate that precipitation positively influences radial growth. Despite of minor differences in local climate–growth relations, precipitation for the annual window between previous July and current June shows consistent positive correlations with ring width at all study sites. Similar to the so called ‘pointer year’ approach, ‘anomalous’ growth years were defined to extract extreme climate events for the period AD 1450–2006. We defined a dryness–wetness grade series with five grades of climate events inferred from anomalous year analysis. During the last 50 years, the frequency of wet events increased and that of drought events decreased noticeably, implying that the probability of occurrence of dry years in the northeastern Tibetan Plateau will further decrease in the future if regional warming continues. Combining our proxy records with a historical dryness–wetness record from eastern China, we mapped dryness–wetness patterns over large parts of China. By analyzing the atmospheric pressure patterns at the 850 hPa level over China for selected extreme event years, we found that the confluence of cold and hot air is a precondition for a flood event in the northeastern Tibetan Plateau. Thus, a counter-clockwise atmospheric circulation centered in south of Lake Baikal only occurs in flood event years.

Climate Risks and Their Impact on Agriculture and Forests in Switzerland

There is growing evidence that, as a result of global climate change, some of the most severe weather events could become more frequent in Europe over the next 50 to 100 years. The paper aims to (i) describe observed trends and scenarios for summer heat waves, windstorms and heavy precipitation, based on results from simulations with global circulation models, regional climate models, and other downscaling procedures, and (ii) discuss potential impacts on agricultural systems and forests in Switzerland. Trends and scenarios project more frequent heavy precipitation during winter corresponding, for example, to a three-fold increase in the exceedance of today's 15-year extreme values by the end of the 21st century. This increases the risk of large-scale flooding and loss of topsoil due to erosion. In contrast, constraints in agricultural practice due to waterlogged soils may become less in a warmer climate. In summer, the most remarkable trend is a decrease in the frequency of wet days, and shorter return times of heat waves and droughts. This increases the risk of losses of crop yield and forage quality. In forests, the more frequent occurrence of dry years may accelerate the replacement of sensitive tree species and reduce carbon stocks, and the projected slight increase in the frequency of extreme storms by the end of the century could increase the risk of windthrow. Some possible measures to maintain goods and services of agricultural and forest ecosystems are mentioned, but it is suggested that more frequent extremes may have more severe consequences than progressive changes in means. In order to effectively decrease the risk for social and economic impacts, long-term adaptive strategies in agriculture and silviculture, investments for prevention, and new insurance concepts seem necessary.

Decade-Scale Precipitation Increase in Great Plains at End of 20th Century

During the 1980–1999 period, many regions in the central and southern Great Plains experienced the longest and strongest increase in average annual precipitation of the century. The size of the increase ranged from 6 to 12% of mean annual precipitation and from 25 to 60% of interannual precipitation variability. Precipitation increased for dry, average, and wet years, though not equally for each category. Generally, precipitation in very wet years increased less than in average and dry years. The probability of occurrence of dry years was greatly reduced compared to earlier in the century, whereas the probability of average years remained about the same and the probability of wet years increased. The observed decade-scale precipitation increase is attributed to a reduction in the number and severity of dry years, as well as to an increase in the number of wet years, though very wet years did not increase as much. The seasonal distribution of the increase in precipitation showed no statistically significant prevalence during any one particular month, yet qualitative considerations suggest that early summer and autumn months capture more of the annual precipitation increase. In the northern and northwestern Great Plains, a similar precipitation increase, but of smaller proportions, was observed during the 1990–1999 period.