Hydrometeorological Factors Research Articles

Diurnal Variation of the Diffuse Attenuation Coefficient for Downwelling Irradiance at 490 nm in Coastal East China Sea

The diurnal variation of the diffuse attenuation coefficient for downwelling irradiance at 490 nm (Kd(490)) has complex characteristics in the coastal regions. However, owing to the scarcity of in situ data, our knowledge on the diurnal variation is inadequate. In this study, an optical-buoy dataset was used to investigate the diurnal variation of Kd(490) in the coastal East China Sea, and to evaluate the Kd(490) L2 products of geostationary ocean color imager (GOCI), as well as the performance of six empirical algorithms for Kd(490) estimation in the Case-2 water. The results of validation show that there was high uncertainty in GOCI L2 Kd(490), with mean absolute percentage errors (MAPEs) of 69.57% and 68.86% and root mean square errors (RMSEs) of 0.70 and 0.71 m−1 compared to buoy-measured Kd12(490) and Kd13(490), respectively. Meanwhile, with the coefficient of determination (R2) of 0.71, as well as the lowest MAPE of 27.31% and RMSE of 0.29 m−1, the new dual ratio algorithm (NDRA) performed the best in estimating Kd(490) in the target area, among the six algorithms. Further, four main types of Kd(490) diurnal variation were found from buoy data, showing different variabilities compared to the area closer to the shore. One typical diurnal variation pattern showed that Kd(490) decreased at flood tide and increased at ebb tide, which was confirmed by GOCI images through the use of NDRA. Hydrometeorological factors influencing the diurnal variations of Kd(490) were also studied. In addition to verifying the predominant impact of tide, we found that the dominant effect of tide and wind on the water column is intensifying sediment resuspension, and the change of sediment transport produced by them are secondary to it.

A time series assessment of terrestrial water storage and its relationship with hydro-meteorological factors in Gilgit-Baltistan region using GRACE observation and GLDAS-Noah model

Mountains regions like Gilgit-Baltistan (GB) province of Pakistan are solely dependent on seasonal snow and glacier melt. In Indus basin which forms in GB, there is a need to manage water in a sustainable way for the livelihood and economic activities of the downstream population. It is important to monitor water resources that include glaciers, snow-covered area, lakes, etc., besides traditional hydrological (point-based measurements by using the gauging station) and remote sensing-based studies (traditional satellite-based observations provide terrestrial water storage (TWS) change within few centimeters from the earth’s surface); the TWS anomalies (TWSA) for the GB region are not investigated. In this study, the TWSA in GB region is considered for the period of 13 years (from January 2003 to December 2016). Gravity Recovery and Climate Experiment (GRACE) level 2 monthly data from three processing centers, namely Centre for Space Research (CSR), German Research Center for Geosciences (GFZ), and Jet Propulsion Laboratory (JPL), System Global Land Data Assimilation System (GLDAS)-driven Noah model, and in situ precipitation data from weather stations, were used for the study investigation. GRACE can help to forecast the possible trends of increasing or decreasing TWS with high accuracy as compared to the past studies, which do not use satellite gravity data. Our results indicate that TWS shows a decreasing trend estimated by GRACE (CSR, GFZ, and JPL) and GLDAS-Noah model, but the trend is not significant statistically. The annual amplitude of GLDAS-Noah is greater than GRACE signal. Mean monthly analysis of TWSA indicates that TWS reaches its maximum in April, while it reaches its minimum in October. Furthermore, Spearman’s rank correlation is determined between GRACE estimated TWS with precipitation, soil moisture (SM) and snow water equivalent (SWE). We also assess the factors, SM and SWE which are the most efficient parameters producing GRACE TWS signal in the study area. In future, our results with the support of more in situ data can be helpful for conservation of natural resources and to manage flood hazards, droughts, and water distribution for the mountain regions.

Влияние осеннего увлажнения почв на эрозионно-аккумулятивные процессы в Красноярской лесостепи

The results of field observations of erosion-accumulation processes caused by meltwater in the northern zone of the Krasnoyarsk forest-steppe in 2009-2017 are discussed. Hydrometeorological conditions of melt runoff formation during the study period and their influence on the values of washout and accumulation are analyzed. Data on snow cover, soil moisture in the pre-winter period, meltwater flow to the soil surface, and spring and autumn runoff are compared. Attention is focused on the autumn soil moisture. The correlation between the values of washout and preceding autumn moisture is revealed. Other things being equal, among all hydrometeorological factors on the territory of the Krasnoyarsk forest-steppe, pre-winter soil moisture has a significant impact on the intensity of erosion-accumulation processes. Keywords: soil washout, erosion, autumn moisture, hydrometeorological factors, runoff, snow cover, humidity, freezing, water permeability

ВЛИЯНИЕ КЛИМАТИЧЕСКИХ ИЗМЕНЕНИЙ НА МАКСИМАЛЬНЫЕ УРОВНИ ПЕРИОДА ПОЛОВОДЬЯ РЕКИ АБАКАН

Актуальность работы обусловлена воздействием изменений климата на гидрологические режимы рек южной Сибири, увеличением повторяемости опасных гидрологических явлений. Наблюдаемые и прогнозируемые изменения в режимах половодий вызываются множеством факторов и требуют различных подходов для характеристики типов этих изменений. Цель: стохастическое моделирование сумм твердых осадков в исследуемом бассейне р. Абакан, установление их связи с максимальными уровнями воды в р. Абакан периода половодья в условиях пространственно-временной изменчивости гидрометеорологических факторов. Методы: комплексный географо-гидрометеорологический анализ, выявление зависимостей по данным многолетних гидрометеорологических наблюдений с использованием методов математической статистики, а также методики оценки количества осадков в бассейне с учетом орографический добавки к скорости вертикальных движений во фронтальной зоне, разработанной В.П. Галаховым. Результаты. Основным фактором формирования максимальных уровней периода половодья является количество зимних осадков. Обильные жидкие осадки на спаде половодья могут вносить значительные коррективы в максимальные уровни. Однако для бассейнов горных рек юга Западной и Восточной Сибири в последние десятилетия в связи с климатическими изменениями отмечается влияние условий промерзания почвогрунтов в осенний период на формирование максимальных уровней вследствие снеготаяния. Для бассейнов со значительной долей предгорных равнин в отдельные годы возможно уменьшение максимальных уровней периода половодья. Для бассейнов, имеющих в основном горный ландшафт, подобного эффекта не наблюдается. Разработана методика расчета сумм зимних ежегодных осадков в бассейне Абакана, учитывающая физические особенности формирования осадков в горах, в частности орографическую добавку к скорости вертикальных движений. На примере независимых данных показано, что алгоритмы расчета максимальных уровней за счет снеготаяния, основанные на регрессионных зависимостях, не всегда дают адекватные результаты. Необходима их корректировка с учетом процессов промерзания на предгорной равнине. Для получения общей статистической зависимости требуются дополнительные данные наблюдений.

Is It a Drought or Only a Fluctuation in Precipitation Patterns?—Drought Reconnaissance in Poland

The process of propagation from meteorological to hydrological drought is studied using the Vistula basin in Poland (193,960 km2) as a case study. The study aims to set a background for the analysis of processes influencing drought propagation in the basin, including the availability of data on hydro-meteorological factors, groundwater, and major human activities that might influence the water cycle in the region. A recent history of drought events in the basin is derived based on a statistical analysis of flow measured at nine gauging stations located along the river, starting from upstream downwards in the 1951–2018 period. The study is enhanced by the analysis of the temporal and spatial variability of a number of drought indices. As a result, the factors affecting temporal and spatial variability of drought—with particular emphasis on the interaction between the variability induced by natural processes and human interaction—are identified. The drought dynamics is studied by analysis of the relationships between meteorological and hydrological drought indices. The results indicate that the Vistula River basin has been influenced in its upstream part mainly by the mining industry, and the middle and downstream parts are additionally affected by industry and agriculture.

Anomalous Phenomena in the Development of Phytoplankton in the Black Sea on the Basis of Remote Sensing Data

Anomalous phenomena in the development of phytoplankton in the Black Sea for the period of 2000–2020 have been recorded on the basis of satellite data. Anomalous summer blooms of diatoms were detected in the field of chlorophyll a for the blooming periods of 2001, 2010, and 2015. These blooms were unusual for the summer periods and developed under conditions of a negative anomaly in the surface layer temperature caused by active wind mixing. The highest level of development of summer blooms of coccolithophore was recorded in 2006, 2012, and 2017. These phenomena have been observed after abnormally cold winters. It has been shown that in some years, under conditions of low summer temperatures and active wind mixing, the summer vegetation of coccolithophores is poorly manifested and can be replaced by the development of diatoms. Satellite data over a twenty-year period demonstrated numerous signs of mass development of coccolithophores during the cold season. Winter blooms of coccolithophorids occur in warm winters with low wind activity. It has been noted that after the winter blooms of coccolithophores, their summer vegetation is largely smoothed. The influence of hydrometeorological factors on the seasonal and interannual variability of phytoplankton is discussed.

Two-Phase Fuzzy System for Multiple Hydro-Meteorological Spatial Risk Mapping in Surabaya, Indonesia

Disaster in Indonesia is caused by hydro-meteorological factors dominate disasters in Indonesia every year. Surabaya is the capital of East Java, which has population growth problems and a high incidence of hydro-meteorological disasters. Surabaya has a high vulnerability to floods, drought, and strong winds. The mapping of the risk of hydrometeorological hazards in cities with rapidly growing populations is used as a guide for preventive measures. The map can provide information on disaster risk which consists of 3 aspects, they are a hazard, vulnerability, and capacity. A multi-disaster map is needed because it provides a complete picture of the potential and history of disasters in an area. The hydro-meteorological multi-disaster map can be used by policymakers to weigh benefits or risks and to resolve contingent disasters. In this study, we proposed a multiple hydro-meteorological spatial risk mapping in Surabaya city using a two-phase Fuzzy system. The first phase assesses the risk of each flood, drought, and wind disaster in each sub-district based on multi-criteria, such as hazard, vulnerability, and capacity. The second phase calculates the risk assessment of the three disasters and divides it into three levels of risk, consist of the low, medium, and high for each sub-district. In 2014 and 2015, there are 16.1% of low risk, 77.4% of medium risk, and 6.5% high risk sub-districts for multiple hydro-meteorological risk assessments. The results of the analysis show that there are three districts in the city of Surabaya that are at high risk of hydro-meteorological disasters, consisting of Tambaksari, Wonokromo, and Sawahan.

ИНФОРМАТИВНОСТЬ ГИДРОМЕТЕОРОЛОГИЧЕСКИХ И АСТРОГЕОФИЗИЧЕСКИХ ФАКТОРОВ В ЗАДАЧЕ ОПИСАНИЯ МЕЖГОДОВЫХ КОЛЕБАНИЙ ЛЕДОВИТОСТИ ГРЕНЛАНДСКОГО МОРЯ

The interannual changes in ice coverage in the Greenland Sea for the winter (December–April), spring (May– June), summer (July–September), and autumn (October–November) seasons for the period 1950-2018 are considered. The presence of negative linear trends and the polycyclic oscillations of the ice coverage variability for all seasons has been confirmed. Using spectral analysis, the dominant fluctuations from 5 to 22 years were identified. The cross-correlation method allowed us to determine the significant relationship of the Greenland Sea ice coverage with hydrometeorological and astrogeophysical factors. The statistically significant relationship of the ice coverage for a concrete year with similar characteristics for a previous period persisting up to three years had been noted. The highest cross-correlation coefficients were noted in the winter and spring seasons. The ice coverage of the autumn season demonstrates the persistence of the inertia of ice conditions for up to two years. The analysis of correlations with astrogeophysical parameters revealed the closest relationship between the ice coverage and the longitude coordinate of the Earth's pole position, the nutation parameters of the Earth's axis, and the distance between the Earth and the Sun. When constructing the multi-regression equations, we investigated the informativeness of various hydrometeorological and astrogeophysical factors in the models of the ice coverage variability for each season. The following estimates of quality of the models were obtained: correlation coefficients (up to 0.89), determination coefficients (to up 0.80), and a model reliability which depends on the admissible forecast error and includes the mean square deviation of the investigated value) – up to 99%). The informativeness of various factors was estimated and the contribution to the total variance was revealed: hydrometeorological factors – up to 70%; astrogeophysical factors – up to 50%. The obtained statistical equations can be used for the diagnosis and for development of methods for the very-long-term forecast of the Greenland Sea ice coverage.

МОДЕЛЬ НОРМИРОВАНИЯ ВОДОПОТРЕБЛЕНИЯ И РАСЧЕТА ЭКСПЛУАТАЦИОННОГО РЕЖИМА ОРОШЕНИЯ СЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР

Purpose: development of a current model of water consumption rationing and calculation of the corresponding rates and terms for agricultural crops irrigation under various hydrometeorological parameters. Materials and methods: the basis for the developed model is a series of field experiments conducted in 2012–2014, as well as analytical studies, the scheme of the experiment, soil and hydrometeorological characteristics, water balance dynamics, precipitation and total moisture supply of the irrigated massif, water consumption according to the development stages of summer planting potatoes were determined. Results and discussion: the model under consideration includes taking into account the water-physical properties of soil, the lowest moisture capacity and moisture reserves, setting critical limit for the irrigation regime, temperature and air humidity deficit, the duration of the growing and inter-irrigation periods, on the basis of which the water consumption of the selected crop is calculated according to the growth phase. Further, the irrigation regime is calculated: the irrigation rate and the difference in moisture reserves, which comparison with the critical limit allows to conclude on irrigation necessity or its prediction for the near future (up to five days) after which irrigation will be needed. A complex for differentiating the irrigation regime with the determining deficits and standards for the parameters under consideration is provided. Conclusions: the model of water consumption rationing, performed on the use of two hydrometeorological factors, taken into account the growth and development phases of the crop under consideration, makes it possible to substantiate the actual calculation of the corresponding norms and terms of agricultural crops irrigation. The model is stable and can be used in land reclamation practice as a part of general technological complex for agricultural crops cultivation on irrigated lands.

Spatiotemporal variations of water quality in Lake Baihua, Guiyang City in the past decade (2009-2018)

百花湖是贵阳市重要的城市饮用水源地，并且近年来经常发生水质异常现象.本文利用2009-2018年百花湖长时间序列的监测数据，采用综合营养状态指数法和Pearson相关性分析，研究了百花湖10年间的水质变化特征和影响因素.结果表明：1）库区叶绿素a（Chl.a）、总磷（TP）、总氮（TN）、高锰酸盐指数（COD_Mn）和透明度（SD）的浓度范围分别是3.43~39.72 mg/m³、0.034~0.115 mg/L、1.200~2.759 mg/L、1.41~5.51 mg/L和0.75~2.07 m，且高氮磷比（12~63）表明百花湖是磷限制型.2）在空间上，TP、TN、氨氮、COD_Mn和Chl.a浓度沿水体流向逐渐降低，SD呈相反变化趋势.3）10年来，百花湖水质由Ⅳ类转变为Ⅲ类，综合营养状态由轻度富营养化状态转变为中营养状态，水质整体向好.4）入库支流是影响百花湖库区水质的主要因素，长期以来，东门桥河、南门河水质TP和TN等超标严重，给库区水质稳定达标带来威胁.5）百花湖Chl.a浓度与气温、水位、风速和TP等指标显著相关，是受水文、气象及营养盐因素的综合控制.未来在百花湖水环境保护治理过程中，应加大对东门桥河、南门河等重点支流的污染治理，加强对水动力学、气候变化等水文气象因素影响库区水质（藻类水华）的机制研究.;Lake Baihua is an important source of urban drinking water in Guiyang City, and water quality anomalies often occur for many years. The long-term water quality monitoring data (from 2009 to 2018), together with the comprehensive trophic level index(TLI) method and Pearson correlation analysis, are used to study the water quality change characteristics and influencing factors of Lake Baihua over the past ten years. The results show that:1) The concentrations of chlorophyll-a(Chl.a), total phosphorus(TP), total nitrogen(TN), permanganate(COD_Mn) and transparency(SD) ranged from 3.43 to 39.72 mg/m³, from 0.034 to 0.115 mg/L, from 1.200 to 2.759 mg/L, from 1.41 to 5.51 mg/L and from 0.75 to 2.07 m, respectively. The high N/P ratio (12-63) indicates that Lake Baihua is a phosphorus limited type. 2) In space, the concentrations of TP, TN, ammonia nitrogen, COD_Mn and Chl.a decreased gradually along the flow direction of the water body, and SD showed the opposite trend. 3) The water quality of Lake Baihua has gradually improved from class Ⅳ to class Ⅲ from 2009 to 2018, and TLI has changed from light-eutrophic state to mesotrophic state. 4) The inflow tributaries are the main factors affecting the water quality in the reservoir area. The water TP and TN in Dongmenqiao and Nanmen Rivers were seriously over standard, which threatens the stability of water quality in the reservoir area. 5) The concentration of Chl.a was significantly related to temperature, water level, wind speed, and total phosphorus, which is considered to be controlled by the combination of hydrological, meteorological and nutrient factors. In the future, the pollution control of Dongmenqiao, Nanmen Rivers needs to be strengthened. Meanwhile, the mechanism of water quality (algal bloom) influenced by hydrodynamics, climate change and other hydrometeorological factors also needs to be further studied.

Reliability Performance of Shipboard Power Complexes with Regard to Ecosystem Effects

The article deals with the impact of ecosystem on the operability of ship power systems. It is shown, that influence is caused by fouling of a vessel hull by various microorganisms, spontaneous destruction of external structures of vessels and hydrometeorological external factors. Methods of solving the problem of ecosystem impact on power complexes of marine equipment are given.

Cartographic support for assessing the suitability of land for agricultural production in the PRC’s Capital Region

This article examines the role of meteorological factors in the formation of adverse conditions for agricultural development in the capital region of the People’s Republic of China (PRC). This area is one of the most densely populated, and the problem of food supply is very acute. The suitability of the area for agricultural activities not only depends on hydrometeorological conditions, but also on the frequency of meteorological disasters. Such disasters include droughts, flooding of the territory due to intensive precipitation and extremely high air temperatures. In this work, it has been made an attempt to analyse the frequency of adverse events of meteorological phenomena and their distribution over the territory of the capital region. Electronic maps of frequency of both individual disasters and an integral map were created, which allowed dividing the territory into 4 categories of total adverse hydrometeorological factors for the development of agricultural production. This study can be as an additional basis for the planning and development of various sectors of agricultural production and for the implementation of measures to reduce the impact of meteorological disasters on agriculture.

Analysis of the relationship between structural indicators of phytoplankton and phenol content in the Kazan Bay of the Kuibyshev reservoir

In the waters of the Kazan Bay of the Kuibyshev reservoir, located within the city of Kazan, excessive concentrations of phenols are periodically present in the summer period, the number of Cyanophyta (Cyanoprokaryota) exceeds 100 million с./l, reaching a potentially dangerous level for public health. As a result of statistical analysis (p<0,05), it was revealed that in the spring-autumn period of 2017 - 2018, to a certain extent, the content of phenols correlates with structural characteristic of Cyanophyta (linear correlation coefficient was 0.66), Ochrophyta (-0,36 - -0,62) and Cryptophyta (-0,31). Hydrometeorological factors (air temperature, precipitation) can influence the number and biomass of phytoplankton and its individual taxonomic groups. In the Kazan Bay, which is characterized as a low-flow, in the rainy spring-autumn season, the risk of increasing phytoplankton biomass and phenol content in the water increases.

Asi Havzasında Hidrometeorolojik Faktörler ve Akım Arasındaki İlişkinin Modellenmesi

Dünya üzerinde birçok hava olayları, iklimsel değişiklikler ve su kullanımının planlanması hidrolojik döngüden etkilenirler. Su döngüsünün modellenmesi yağış değişkenliği ve taşkın için çok önemlidir. Bu çalışmada Asi Havzasına ait istasyonların 1962-2011 yılları arasındaki hidrometeorolojik parametreleri kullanılarak regresyon analizi yapılmıştır. Havzaya ait parametrelerin birbiriyle oluşturulan kombinasyonları ve akım ile ilişkileri DataFit programı aracılığı ile analiz edilmiştir. Analiz sonucunda en yüksek R², OKH ve KOKH (hata oranları) değerleri incelendiğinde yağış-buharlaşma-akım modeli önerilmiştir. Ayrıca bu parametrelerin trend analizleri parametrik olmayan Mann Kendall Testi ile analiz edilmiştir. Asi Havzasını etkileyen 6 parametre için parametrelerin %85 ve %95 güven aralıklarındaki eğilimleri incelenmiştir.

The direct and interactive impacts of hydrological factors on bacillary dysentery across different geographical regions in central China

Previous studies found non-linear mutual interactions among hydrometeorological factors on diarrheal disease. However, the complex interactions of the hydrometeorological, topographical and human activity factors need to be further explored. This study aimed to reveal how hydrological and other factors jointly influence bacillary dysentery in different geographical regions. Using Anhui Province in China, consisted of Huaibei plain, Jianghuai hilly and Wannan mountainous regions, we integrated multi-source data (6 meteorological, 3 hydrological, 2 topographic, and 9 socioeconomic variables) to explore the direct and interactive relationship between hydrological factors (quick flow, baseflow and local recharge) and other factors by combining the ecosystem model InVEST with spatial statistical analysis. The results showed hydrological factors had significant impact powers (q = 0.444 (Huaibei plain) for local recharge, 0.412 (Jianghuai hilly region) and 0.891 (Wannan mountainous region) for quick flow, respectively) on bacillary dysentery in different regions, but lost powers at provincial level. Land use and soil properties have created significant interactions with hydrological factors across Anhui province. Particularly, percentage of farmland in Anhui province can influence quick flow across Jianghuai, Wannan regions and the whole province, and it also has significant interactions with the baseflow and local recharge across the plain as well as the whole province. Percentage of urban areas had interactions with baseflow and local recharge in Jianghuai and Wannan regions. Additionally, baseflow and local recharge could be interacted with meteorological factors (e.g. temperature and wind speed), while these interactions varied in different regions. In conclusion, it was evident that hydrological factors had significant impacts on bacillary dysentery, and also interacted significantly with meteorological and socioeconomic factors. This study applying ecosystem model and spatial analysis help reveal the complex and nonlinear transmission of bacillary dysentery in different geographical regions, supporting the development of precise public health interventions with consideration of hydrological factors.

Hydrodynamic Analysis of a Stormwater System, under Data Scarcity, for Decision-Making Process: The Duran Case Study (Ecuador)

Urban flooding is a major problem in many coastal cities around the world, mainly caused by factors such as poor urban planning, outdated sewer capacity or high frequent extreme events. In developing countries such as Ecuador, lack of monitoring, financial constraints and absence of proper policies exacerbate flooding problems. The use of the Stormwater Management Model (SWMM) helped to identify zones that are flooded even with a 2-year precipitation event at Duran city. Since there are no flood monitoring stations across the study area, model calibration was performed against unofficial records (people complaints, media photographs, and water marks on walls). Model results fairly agreed with those unofficial record. However, a validation process is not achievable yet due to lack of enough flood data even in flood prone areas. To further increase city resilience, authorities and stakeholders should engage in climate actions to raise flood hazard-risk awareness, monitoring hydro-meteorological factors, complement drainage operations with nature-based solutions, and improve hydrodynamic modelling to develop a flood early warning system for the city.

Water quality characteristics and assessment of Yongding New River by improved comprehensive water quality identification index based on game theory

The Yongding New River is essential for the water supplies of Tianjin. To date, there is no comprehensive report that assesses the year-round water quality of the Yongding New River Main stream. Moreover, little attention has been given to determining a combined weight for improving the traditional comprehensive water quality identification index (ICWQII) by the game theory. Seven water quality parameters were investigated monthly along the main stream of the Yongding New River from May 2018 to April 2019. Organic contaminants and nitrogen pollution were mainly caused by point sources pollution, and the total phosphorus mainly by non-point source pollution. Dramatic spatio-temporal variations of water quality parameters were jointly caused by different pollutant sources and hydrometeorological factors. In terms of this study, an improved comprehensive water quality identification index (ICWQII) based on entropy weight or variation coefficient and traditional CWQII underestimated the water qualities, and an ICWQII based on the superstandard multiple method overvalued the assessments. By contrast, water qualities assessments done with an ICWQII based on the game theory matched perfectly with the practical situation. The ICWQII based on game theory proposed in this study takes into account not only the degree of disorder and variation of water quality data, but also the influence of standard-exceeded pollution indicators, whose results are relatively reasonable. All findings and the ICWQII based on game theory can provide scientific support for decisions related to the water environment management of the Yongding New River and other waters.

Exploring the potential factors on the striking water level variation of the two largest semi-arid-region lakes in northeastern Asia

Global warming and drying have caused desiccation of lakes in arid and semi-arid regions worldwide, and the mechanisms underlying sharp decreases in water level of great lakes in arid and semi-arid regions in recent decades require elucidation. Using a combination of multiple statistical and modeling methods, we extracted multi-decadal trends from water level time series (~1960–2017) of the two largest lakes in northern China, and explored the influences of hydro-meteorological factors on the multi-decadal and inter-annual variation in lake water level. The hydrology components of the Hulun Lake basin varied with greater amplitude than those of the Qinghai Lake basin, with water level decreases of 5.3 (1991–2011) and 3.1 (1961–2004) m in Hulun Lake and Qinghai Lake, respectively. River runoff influenced multi-decadal changes in water level of the two great lakes most, followed by lake surface evaporation and precipitation at the lake surface. Lake surface evaporation, driven by potential evaporation and lake area dynamics, was the largest hydrology component of the two great lakes. Lake surface evaporation mitigated the decline of Hulun Lake over 1995–2011, while it aggravated the decline of Qinghai Lake over 1990–2005. Although El Niño–Southern Oscillation significantly affected various hydro-meteorological factors, it contributed less than 6% of inter-annual variation in Hulun Lake, and no significant effect on the variation in Qinghai Lake was found. Pan evaporation was negatively correlated with precipitation and land evapotranspiration in both great lake basins.

Effects of class imbalance on resampling and ensemble learning for improved prediction of cyanobacteria blooms

This study aimed to explicitly explore the effects of the degree of class imbalance on predicting infrequently occurring events, i.e., cyanobacteria blooms. Although class imbalance poses a major issue in binary classification schemes, few efforts have been made to relate model performance with real-life applications. The data utilized herein were collected from 2013 to 2019 at 13 sites within three major rivers in South Korea; a variety of physicochemical and hydrometeorological factors were obtained as input variables, and the occurrence of cyanobacteria blooms (indicated by a cell count ≥ 1000 cells/mL) was included as a response variable. The imbalance ratio (IR) for cyanobacteria blooms differed significantly by site, ranging widely from 0.93 to 9.32. The study results suggested that class imbalance negatively affected model performance, with an increase in the IR significantly increasing the false negative (FN) rate. The application of resampling decreased the FN rate while simultaneously increasing the true positive (TP) rate, which yielded improvements that tended to increase with increasing IRs. Ensemble classifiers, which combine multiple single classifiers into an integrated classifier, alone could not successfully address the class imbalance problem; however, in combination with resampling, they consistently outperformed single classifiers. Among the ensemble classifiers, AdaBoost yielded the most stable performance across a range of IRs, irrespective of the resampling application. A variable importance analysis indicated that temperature was usually the primary influencing factor of cyanobacteria blooms. These findings highlight the effectiveness of resampling applications for addressing class imbalance, while providing useful guidelines for learning from imbalance data, including the selection of classification algorithms and model evaluation metrics.

АНАЛИЗ ВЛИЯНИЯ ПРИРОДНОЙ ВЛАГООБЕСПЕЧЕННОСТИ НА УРОЖАЙНОСТЬ ПОДСОЛНЕЧНИКА В ЗАСУШЛИВЫХ УСЛОВИЯХ КРЫМСКОГО ПОЛУОСТРОВА

The Crimean Peninsula is located in the dry zone. In the steppe Crimea, which is the driest part of the peninsula, the major limiting factor for crop productivity is the natural moisture supply of plants. The purpose of the research was to establish the relationships between hydrometeorological factors (moisture reserves in the soil before sowing, precipitation amount and Selyaninov hydrothermal coefficient during the growing season) and sunflower yield depending on planting dates (I, II, III decade of April) and plant density (30, 40, 50, 60, 70 thousand units per hectare). The studies were carried out on the trial fields of the Research Institute of Agriculture of Crimea (village of Klepinino) in 2017–2019 using hybrid of ultra-early sunflower ‘Avangard’. The laying of field experiments, accounting, analyzes and statistical processing of data were carried out according to the methods of field research and methodology of field agricultural experiments with oil crops. A strong correlation was observed: 1) between yield and precipitation amount in May (r = 0.977) and moisture reserves before sowing (r = 0.978), planting dates – the first decade of April; 2) between precipitation amount in May (r = 0.932) and moisture reserves before sowing (r = 0.977–0.978), sunflower was sown in the second decade of April; 3) moisture before sowing (r = 0.892), crop planted in the third decade of April. A close positive relationship (r = 0.853–0.972) was observed at the optimal plant density for the region (40 thousand units/ha) between the amount of precipitation in April–May, moisture reserves in the soil before sowing and yield of sunflower. This indicates a high value of moisture availability during this period in the crop yield formation. In denser crops (50–70 thousand units/ha), the closest relationship is observed between the yield and the amount of precipitation in May. This makes the latter primary and decisive in the cultivation of crops with such a density since the competition for moisture increases with an increase in the number of plants per unit area. The closest relationship between the Selyaninov hydrothermal coefficient and sunflower yield was observed in April and May (r = 0.833–0.967) when plants grow more intensively and require sufficient moisture.