Significant Precipitation Events Research Articles

Neural network-based climate index: Advancing rainfall prediction in EI Niño contexts

Accurate short-term climate predictions, specifically the prediction of dominant rain belts during flood seasons, represent a significant challenge, particularly in the absence of notable external forcing signal anomalies in the previous winter. To address this challenge, we propose a novel climate index based on an Auto-Encoder (AE) Neural Network that exhibits superior performance in indicating several significant precipitation events in the Yangtze and Huaihe River Basins under varying El Niño conditions. Notably, the novel climate index rectifies the discrepancy between the 2019/2020 Niño index and the 2020 summer precipitation. In order to understand the information source of AE, the causality between AE and other indices was further analyzed by Granger Causality. The results show that AE index mainly contains the information of subtropical high index and ocean index, which is consistent with previous studies.

Seasonal variation and influence factors of river water isotopes in the East Asian monsoon region: a case study in the Xiangjiang River basin spanning 13 hydrological years

Abstract. Seasonal variation and influencing factors of river water isotopes were investigated in the Xiangjiang River basin located in the East Asian monsoon region. This investigation involved comprehensive sampling of daily precipitation and river water with a 5 d interval as well as observing hydrometeorological factors spanning 13 hydrological years from January 2010 to December 2022, combined with the temporal and spatial correlation analyses based on linear regression and the isotopic Atmospheric Water Balance Model. Key findings are as follows: river water δ2H (δ2HR) exhibited significant seasonal variation, with the most positive and negative values occurring in the spring flood period and summer drought period, respectively, in alignment with those observed in precipitation. The correlations of the δ2HR with corresponding hydrometeorological factors with a 5 d interval were commonly weak due to the seasonality of precipitation isotopes and mixing of various water bodies within the basin, but the changes in the runoff (ΔR) and δ2HR (Δδ2HR) between two contiguous samplings with 5 d or higher intervals showed significant responses to the corresponding accumulated precipitation and evaporation. Prolonged rainless intervals with high evaporation rates in 2013 and 2022 as well as significant precipitation events in major flood periods in 2011 and 2017 had a significant impact on the δ2HR and runoff discharge. However, the most positive δ2HR values were primarily influenced by precipitation input with the most enriched isotopes in the spring flood period, while the moderately isotope-depleted precipitation during limited wetness conditions led to the most negative δ2HR. The spatial correlation analysis between water isotopes and hydrometeorological factors at the observing site and in the surrounding regions supported the representation of the Changsha site in the Xiangjiang River basin. These results underscore the potential of Δδ2HR as a proxy that reflects the seasonal variations in local environments, while caution is advised when interpreting extreme isotopic signals in river water. Overall, this study provides insights into the seasonal variation, extreme signal interpreting, and controlling factors of δ2HR in the study area, which was valuable for paleoclimate reconstruction and establishment of isotope hydrologic models.

Investigation of Subsurface and Geological Structures Contributing to Collapse Sinkholes in Covered Karst Terrain, Northeast Thailand

This study focuses on covered karst terrain situated in Phu Pha Man District, Khon Kaen Province, Northeast Thailand, where records of collapse sinkholes are limited. Here, we investigate the subsurface characteristics and potential causes of sinkhole formation within this area using geophysical methods, hydrogeological techniques, and precipitation analysis. We collected field data by measuring groundwater levels, and conducting electrical resistivity tomography (ERT) surveys. We identified eight cover-collapse sinkholes of various shapes and sizes. Analysis of the groundwater flow indicated that the predominant flow direction runs from north to southeast. Examination of rainfall data showed a progressive increase in total rainfall on a yearly basis, with a significant precipitation event preceding the initial occurrence of sinkholes. The ERT results revealed the presence of highly resistive bedrock, water-saturated layers, and potential cavities. Notably, the tomograms indicated variations in resistivity values, suggesting the presence of irregular surfaces of limestone bedrock and weathered zones as characteristics of karst settings. Intense precipitation is a possible dominant trigger for the formation of the sinkholes. This study contributes to understanding sinkhole formation in karst environments and provides key information for hazard mitigation, not only in the Phu Pha Man District but also in areas with similar geological settings.

Cascade sensitivity tests to model deep convective systems in complex orography with WRF

The goal of the present study is to improve the analysis of the performance of the Weather Research and Forecasting (WRF) model, Version 4.3.3, under different settings, in the prediction of precipitation in case of deep convective events. This is done through a wide cascade sensitivity test involving parameterizations expected to play a major role in the description of precipitation for deep convective events: cloud microphysics (CM), planetary boundary layer (PBL), surface layer (SL) and land-surface (L-S) model. Four significant precipitation events, which were associated to deep convective systems and occurred between 2019 and 2021 in Lombardia and Liguria regions (Northern Italy), have been simulated according to 45 different WRF settings. High resolution simulations are required when dealing with small scale deep convective systems as well as a suitable verification method. So, traditional statistical indexes have been integrated with new-generation verification methods, based on the identification of precipitation patterns in forecast and observed fields and on the evaluation of their similarity through the calculation of a coupling index. This analysis method has been exploited to evaluate the quality of the high-resolution simulations performed, and to individuate the best-performing WRF setting in simulating intense convective events. From the present work emerges how the unique CM parameterization characterized by a triple-moment treatment for cloud ice significantly outperforms all other CM schemes underlying the main role of cloud ice in the description of the precipitation case studies. Furthermore, PBL and L-S schemes show a leading role, at least as much as CM, in the description of the events.

Rok 2022 v Česku

The article summarizes main events in the months of 2022 in meteorology, climatology, hydrology and ambient air quality. The average annual temperature of 9.2 °C with a deviation of +0.9 °C above the 1991–2020 normal (and +1.7 °C from the 1961–1990 normal) classifies the year as a temperature normal year. The annual precipitation amount of 630 mm classifies the year as normal compared to both the 1961–1990 and 1991–2020 normals. The highest and lowest temperatures, significant precipitation events and, where applicable, higher wind speeds and snowfall, and groundwater statistics are shown for each month. If the level of flood activity in Czechia was reached, it is also listed in the overview. With respect to the air quality, cases exceeding the limit values for human health protection, and smog situations declared are listed. Compared to the 10-year average (2012–2021) the dispersion conditions were significantly better in 2022. Good dispersion conditions, as expressed by the ventilation index for the whole country, were recorded in 320 days (88%), moderately poor dispersion conditions in 42 days (11%) and poor dispersion conditions in three days (1%) in 2022.

Rok 2022 v Česku

The article summarizes main events in the months of 2022 in meteorology, climatology, hydrology and ambient air quality. The average annual temperature of 9.2 °C with a deviation of +0.9 °C above the 1991–2020 normal (and +1.7 °C from the 1961–1990 normal) classifies the year as a temperature normal year. The annual precipitation amount of 630 mm classifies the year as normal compared to both the 1961–1990 and 1991–2020 normals. The highest and lowest temperatures, significant precipitation events and, where applicable, higher wind speeds and snowfall, and groundwater statistics are shown for each month. If the level of flood activity in Czechia was reached, it is also listed in the overview. With respect to the air quality, cases exceeding the limit values for human health protection, and smog situations declared are listed. Compared to the 10-year average (2012–2021) the dispersion conditions were significantly better in 2022. Good dispersion conditions, as expressed by the ventilation index for the whole country, were recorded in 320 days (88%), moderately poor dispersion conditions in 42 days (11%) and poor dispersion conditions in three days (1%) in 2022.

Horizontal grid spacing comparison among Random Forest algorithms to nowcast Cloud-to-Ground lightning occurrence

The relation between the increase in the frequency and the effects of extreme events with climate change has been widely demonstrated and the related consequences are a global concern. In this framework, the strong correlation between significant lightning occurrence and intense precipitation events has been also documented. Consequently, the possibility of having a short-term forecasting tool of the lightning activity may help in identifying and monitoring the evolution of severe weather events on very short time ranges. The present paper proposes an application of Random Forest (RF), a popular Machine Learning (ML) algorithm, to perform a nowcasting of Cloud-to-Ground (CG) lightning occurrence over the Italian territory and the surrounding seas during the months of August, September, and October from 2017 to 2019. Results obtained with three different spatial resolutions have been compared, suggesting that, to enhance the skills of the model in identifying the presence or absence of strokes, all the data selected as input should be commonly gridded on the finest available spatial resolution. Moreover, the features’ importance analysis performed confirms that meteorological features describing the state of the atmosphere, especially at higher altitudes, have a stronger impact on the final result than topology data, such as Latitude or Digital Elevation Model (DEM).

Delayed 10Be dilution in detrital quartz following extensive coseismic landsliding: A 2016 Kaikōura earthquake case study

Large earthquakes play a major role in the topographic evolution of active orogens. Earthquake induced landslides can alter the mass balance of mountain belts for decades to centuries depending on how landslide material is transported and stored. In this study, we analysed in-situ10Be concentrations in fluvial sediments to capture a time series of post-earthquake denudation rates of the Tūtae Putaputa|Conway River catchment, which experienced ∼13 × 106 m3 of landsliding in the 2016 Kaikōura earthquake. 10Be concentrations were determined for detrital samples from the Conway River at the rangefront of the Seaward Kaikōura Mountains, South Island, New Zealand, and near the catchment outlet over three sampling intervals, including after significant precipitation events, 1-2 yr following the earthquake. Our results indicate somewhat higher apparent erosion rates at the rangefront (0.41-0.58 mm/yr) when compared to erosion rates incorporating lower-relief sub-catchments at the river outlet (∼0.28 mm/yr). No changes were found over the same time period in the Hurunui River, a neighbouring catchment that experienced negligible coseismic landsliding during the Kaikōura event. Apparent catchment-averaged erosion rates in the Conway River have remained similar to long-term exhumation rates from previously published thermochronology studies. To explain our results, we explore the observed controls on catchment-wide 10Be concentrations in our study area, such as the spatiotemporal variability in landslide connectivity to the channel and storage within the catchment. Our results highlight that using in-situ cosmogenic 10Be in fluvial deposits as a proxy for changes in sediment fluxes of earthquake-affected landscapes is complex and highly site-specific.

Impacts of climatic change and database information design on the water-energy-food nexus in water-scarce regions

The objective of this paper was three-fold. The paper highlights the synergies and tradeoffs in the interconnectedness of water-energy-food (WEF) for the agricultural corridor of North-South Al-Batinah, Sultanate of Oman. The study further evaluates the impacts of climate change on the WEF nexus. The results show that by 2099, Al-Batinah’s mean temperature will range from 2.0 to 3.5 °C and 1.0 to 2.5 °C for RCP8.5 and RCP4.5 scenarios, respectively, when compared to 1986–2005 historical simulations. From a precipitation standpoint, the analysis showed drier January and February months with significant heavy precipitation events in March for both scenarios when compared with the historical simulations. Thus, the significance and findings of this study further indicate there will be a persistent reduction in water availability which can affect crop yield. The excess wetness in March can lead to extreme climatic events such as flooding and inundation of farmlands. These impacts can trickle down to affect other links in the nexus such as the energy and food supply as well as Tanfeedh plans for economic diversification in agriculture and fisheries proposed by the central government. The study also recognizes the importance of data gaps and various sources of available data that could be integrated for improved planning and decision making. Therefore, a database system using the Unified Model Language was proposed. This platform, when implemented, will help Oman’s efforts in the next decade in strengthening the links between the WEF nexus, meeting the nexus’s demands as a result of climate change, population growth, etc., and also achieving sustainable development goals.

Reconstruction of landslide movements using Digital Elevation Model and Electrical Resistivity Tomography analysis in the Polish Outer Carpathians

Landslides are a major threat to the environment, infrastructure and human activities, especially in mountainous and hilly areas. It is therefore important to accurately identify the mass movements triggering these mechanisms. This paper presents the impacts of lithotectonic conditions on the formation of mass movements on the example of the landslide that is located in the northern part of the Polish Outer Carpathians. In the area of the research, the ratio of the total area of landslides to the surface of the area reaches even 20%. The interpretation of a high resolution Digital Elevation Model (DEM), Electrical Resistivity Tomography (ERT) and fieldwork results allowed for the reconstruction of the landslide movements and dividing them into two areas; the western one, dominated by rotational movement, and the eastern one, featuring rotational and translational movement. It was found that the eastern part is more active now as it probably was also in the past, which might have resulted from the lithotectonic conditioned or from the impact of the flowing waters of the Dunajec River. Moreover, in the eastern part of the landslides, a small-sized ridge (55 m × 25 m) was identified, which shows greater stability in comparison with the colluvium that surrounds it. In order to explain the lower rate of movement of this landform, a morphometric analysis and research using ERT were performed. The geophysical measurements showed that the ridge comprised rock formations of greater resistivity than its surroundings. It is most likely that the only preserved sandstone packet, constituting the original secondary escarpment, became separated from the bedrock due to rotational movement. The presented studies indicate that the landslide was created due to geological and atmospheric conditions. A clear revival of landslide movements took place after significant precipitation events that last occurred in the years 2010 and 2015. The bedrock substrate due to its lithology and tectonics, facilitates these movements. It was found that the landslide studied is a complex entity, characteristic of the Polish Outer Carpathians, that has undergone multiple stages of development. The landslide is active or periodically active and, therefore, must be excluded from the planned development as well as from other forms of human activity.

An insight into water stable isotope signatures in temperate catchment

Stable isotopes are used to decipher hydrological processes in watershed research. A two-year monthly monitoring of hydrogen and oxygen stable isotope ratios (δ2H and δ18O) in a temperate catchment in Norther Europa, Latvia was undertaken. Isotope ratios in common water types – raised bog, confined groundwater, unconfined groundwater and surface water – were measured. We found characteristic signatures of isotope ratios for each of these four water types. The average isotope ratios of different water types ranged from −80.8 to −68.3‰ for δ2H and −11.46 to −8.76‰ for δ18O, with standard deviations from 18 to 25‰ and 0.10 to 1.59‰, respectively. The isotope ratios of the stream base flow were consistent with the groundwater isoscape and seasonally enriched by evaporation. Most enriched water are found in raised bogs and large lakes. The most depleted water is found in a spring discharging phreatic groundwater in a forest site with sandy soil. The most enriched water was associated with significant short-lived precipitation events, resulting in impoundment of water on the land surface and its enrichment due to evaporation. The novelty of this study is that this enriched isotope signal is propagated throughout the hydrological system, temporarily albeit significantly shifting isotope ratios of phreatic groundwater and surface runoff. Further case studies are needed to affirm if this is a regionally significant mechanism controlling isotope ratios of surface and subsurface water. The observed difference between the average δ18O of phreatic groundwater at two locations was 0.9‰. We suggest that the differences are due to different land use and soil conditions.

Gradients in climate, geology, and topography affecting coastal alluvial fan morphodynamics in hyperarid regions – The Atacama perspective

Abstract Along the coast of the hyperarid Atacama Desert, late Quaternary alluvial fans emerge from the Coastal Cordillera to the Pacific Ocean between 20.5°S and 25.5°S. Coastal alluvial fans (CAF) show, in comparison to the interior fans of the Atacama Desert, pronounced recent activity. However, the complex interplay between climate, lithology, and tectonics affecting the CAF morphodynamics in such hyperarid coastal settings needs to be better understood. We therefore aim at assessing the major factors driving CAF activity and evaluate their effects along gradients. We conducted an extensive study relating climatic, lithologic, and tectonic characteristics to fan and catchment geomorphology of 123 CAF. Geomorphometric analyses are based on the 12.5 m TanDEM-X WorldDEM™, catchment lithology and faults are extracted from 13 regional geological maps, and the frequency of heavy rainfall events capable of activating CAF is derived from a Weather Research and Forecasting (WRF) regional climate model. Our results point to a primary climatic control on CAF morphodynamics shown in functional relationships with catchment hydromorphometric characteristics reflecting a high susceptibility to debris flows – the main CAF-constructing process. Catchment properties along the latitudinal gradient reflect the source of significant precipitation events: frontal systems and cut-off lows which mainly originate in the extratropics and become increasingly rare towards the north. The frequency of precipitation extremes can only be correlated to the hydromorphometry and geomorphic maturity of catchments that feature a high degree of sediment transport potential and generally do not cut back far into the Coastal Cordillera. Related to the strongly reduced influence of the Pacific precipitation source towards the east, this additional climatic transition is governed by the orographic effect of the steep W-E gradient in topography. In contrast, source-area lithology is of negligible relevance for CAF catchment morphometry and fan activity. An important indirect influence of tectonics, however, can be seen in the long-term (neo)tectonic activity within the Coastal Cordillera, which in turn shapes catchments and controls the topography.

A Multiscale Evaluation of Multisensor Quantitative Precipitation Estimates in the Russian River Basin

AbstractThe Russian River in northern California is an important hydrological resource that typically depends on a few significant precipitation events per year, often associated with atmospheric rivers (ARs), to maintain its annual water supply. Because of the highly variable nature of annual precipitation in the region, accurate quantitative precipitation estimates (QPEs) are necessary to drive hydrologic models and inform water management decisions. The basin’s location and complex terrain present a unique challenge to QPEs, with sparse in situ observations and mountains that inhibit remote sensing by ground radars. Gridded multisensor QPE datasets can fill in the gaps but are susceptible to both the errors and uncertainties from the ingested datasets and uncertainties due to interpolation methods. In this study a dense network of independently operated rain gauges is used to evaluate gridded QPE from the Multi-Radar Multi-Sensor (MRMS) during 44 precipitation events occurring during the 2015/16 and 2016/17 wet seasons (October–March). The MRMS QPE products matched the gauge estimates of precipitation reasonably well in approximately half the cases but failed to capture the spatial distribution and intensity of the rainfall in the remaining cases. ERA-Interim reanalysis data suggest that the differences in performance are related to synoptic-scale patterns and AR landfall location. These synoptic-scale differences produce different rainfall distributions and influence basin-scale winds, potentially creating regions of small-scale precipitation enhancement or suppression. Data from four profiling radars indicated that a larger fraction of the precipitation in poorly captured events occurred as shallow stratiform rain unobserved by radar.

Evaluation of Gridded Precipitation Data and Interpolation Methods for Forest Fire Danger Rating in Alberta, Canada

AbstractThe Canadian Forest Fire Weather Index System is the primary measurement of wildfire danger in Canada. Interpolating daily precipitation, one of the inputs for the Fire Weather Index System is a key challenge in areas without sufficient weather stations. This work evaluates the performance of gridded precipitation from the Canadian Precipitation Analysis (CaPA) System and six interpolation methods to achieve the best fire danger rating in Alberta, Canada. Results show that the CaPA System has only average performance due to limited radar coverage (10%) in the forested region; however, using the CaPA System as a covariate with regression kriging generates significantly better precipitation estimates. Ordinary kriging, regression kriging with elevation as a covariate, and the thin‐plate smoothed spline are methods with similar performance. Fuel moisture codes of the Fire Weather Index System respond differently to precipitation amounts due to differences in their time constants for drying. Fine fuels with a short drying time (Fine Fuel Moisture Code) are best estimated by the CaPA System because of its enhanced skill in estimating small precipitation events. Compacted organic fuels with longer drying times (Duff Moisture Code and Drought Code) are best estimated by regression kriging with CaPA because it better predicts significant precipitation events. The dense fire weather station network in our study area (~3.0 stations/10,000 km2) allows us to perform a sensitivity analysis, and we find that a threshold of >0.5 stations/10,000 km2 is needed for regression kriging with CaPA to become appreciably better than the CaPA System.

Revegetation modifies patterns of temporal soil respiration responses to extreme-drying-and-rewetting in a semiarid ecosystem

Changes in climate and land-use are altering soil respiration patterns and thus affecting C sequestration rates globally. This study aims to understand the effect of revegetation induced land-use change on the response of soil respiration to precipitation pulses during an extreme-drying-and-rewetting period. Soil respiration (SR) in cropland, grassland, shrubland, and orchard were intensively monitored along with environmental variables during an extreme drought period with precipitation pulse on China’s Loess Plateau. SR was strongly correlated to soil water content for all land-uses. However, the relationship was highly dependent on land-use types: SR was only strongly suppressed in cropland and orchard when moisture content exceeded 10.8 and 13.7%, respectively, whereas no clear suppression was observed under other land-uses. As a result, the C loss in grassland and shrubland was 49.1–78.9% higher than in cropland following significant precipitation events. In addition, SR was negatively and weakly correlated with soil temperature, indicating the change in the dominant control on SR due to extreme drought. Land-use change alters the response of soil respiration to soil moisture during extreme-drying-and-rewetting periods in this revegetated ecosystem. Its effect on respiration pulses will amplify as extreme climate events increase in the future, which may potentially alter the existing C balance.

A review of gauge–radar merging methods for quantitative precipitation estimation in hydrology

In the case of a significant precipitation event, hydrological models play a key role in flood mitigation. To develop a hydrological model that produces results with a high degree of confidence, it is imperative that the model be provided with accurate quantitative precipitation estimates as input. For flood forecasting purposes, quantitative precipitation estimates at high spatial and temporal resolutions are preferable. Rain gauges and weather radar are the most widely used instruments for near real-time collection of precipitation estimates. While rain gauges and radar demonstrate certain strengths, both instruments suffer from a wide variety of well-known errors which inhibit their ability to provide optimal precipitation estimates for hydrological models. Considering this, several methods have been developed to merge the estimates of these two instruments in order to minimize their individual weaknesses and take advantage of their respective strengths. The goal of this paper is to provide a comprehensive review of gauge–radar merging methods and assess the opportunity for near real-time application of gauge–radar merging methods in hydrology. Methods presented include: mean field bias correction, Brandes spatial adjustment, local bias correction with ordinary kriging, range-dependent bias correction, Bayesian data combination, conditional merging, kriging with external drift and statistical objective analysis. While comparison of gauge–radar merging methods is difficult, several factors, including gauge network design, storm type and the temporal resolution of adjustment, have demonstrated a large effect on the overall accuracy of a particular merging method. The majority of research carried out on near real-time application of gauge–radar merging methods has been conducted outside of Canada. Further research is recommended to assess the capability of using gauge–radar merging schemes with Canadian radar products for precipitation estimation in hydrological applications, including operational hydrological modelling for flood forecasting.

A Climatology of the Vertical Structure of Water Vapor Transport to the Sierra Nevada in Cool Season Atmospheric River Precipitation Events

Abstract This study presents the climatology of the vertical structure of water vapor flux above the Sierra Nevada during significant cool season (November–April) precipitation events. Atmospheric river (AR) and non-AR events are analyzed to better understand the effect of this structure on precipitation patterns. Daily measurements of cool season precipitation at seven weather stations around the Tahoe basin from 1974 to 2012 and NCEP/CPC gridded daily precipitation analysis along the Sierra crest for the period 1948–2012 are examined. NCEP–NCAR reanalysis and soundings from Oakland are used to look at upper atmospheric conditions, including the presence of vapor transport by low- and midlevel jets on storm days as well as upstream static stability in relation to significant precipitation events. Key findings are as follows: 1) ARs play a disproportionately large role in generating Tahoe basin precipitation during the cool season; 2) strong midlevel vapor transport needs to occur in tandem with low-level transport to achieve the most extreme 2-day precipitation in the Tahoe basin; 3) when low- to midlevel vapor transport is present on days with a defined AR, the local maximum in 2-day precipitation intensity decreases with distance from the Sierra crest, and on non-AR days, the relative increase in 2-day precipitation intensity due to low- and midlevel vapor transport does not vary based on distance from the Sierra crest; 4) AR and non-AR moisture fluxes are significantly modified by upstream static stability; and 5) understanding the impacts of ARs and their lower- and midlevel moisture flux structure are crucial components of the hydrometeorology in this region.

Precipitation in the Madeira Island over a 10‐year period and the meridional water vapour transport during the winter seasons

ABSTRACTIn this paper, a 10‐year daily accumulated precipitation analysis of Madeira highland is presented, as well as the relationship between meridional water vapour transport during 10 winter seasons and the precipitation recorded in the island during the same period. Here, the meridional water vapour transport is considered as occurring in narrow corridors known as atmospheric rivers – ARs – which were visually identified in the total precipitable water vapour field extracted from Atmospheric Infrared Sounder (AIRS) data within a domain covering the North Atlantic Ocean. European Centre for Medium‐range Weather Forecasts (ECMWF) analysis was also used when necessary. Daily precipitation during the period covered by the study evidenced generally dry summers, whereas the highest values for daily accumulated precipitation were recorded mainly during the winter and also during the autumn and spring. Image analysis shows that moist air originating mainly in the Caribbean Sea flows northward or eastward, intersecting, on some occasions, the island during the winter season, often during a stage of dissipation. The orientation of the flow and the amount of water vapour transported to the island are important features, contributing to the occurrence of significant precipitation events. In fact, the moist environment created by ARs may favour the occurrence of precipitation, but this is not the sole factor favouring high rainfall over Madeira.

白刺沙堆退化与土壤水分的关系研究

PDF HTML阅读 XML下载 导出引用 引用提醒 白刺沙堆退化与土壤水分的关系 DOI: 10.5846/stxb201310242571 作者: 作者单位: 北京大学环境与能源学院,北京大学环境与能源学院,甘肃民勤荒漠草地生态系统国家野外科学观测研究站 甘肃省治沙研究所,甘肃民勤荒漠草地生态系统国家野外科学观测研究站 甘肃省治沙研究所,北京大学环境与能源学院,北京大学环境与能源学院,北京大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项项目(201304305);国家自然科学基金面上项目(20972421); 深圳市人民环境重点实验室专项. The degradation of Nitraria dunes and soil water in Minqin oasis Author: Affiliation: Energy and environment school, Peking University,,,,,,Peking University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:近几十年来,我国西北干旱区白刺沙堆退化严重,导致固定沙丘活化,流沙掩埋绿洲,造成了严重危害。如何尽可能长期保持白刺沙堆的稳定、防止白刺沙堆活化成为绿洲保护和沙漠化防治急需解决的问题。在多年野外观察的基础上,提出了"土壤水分收支不平衡所导致的土壤水分减少是白刺沙堆退化的主要原因"的研究假设。但是,由于缺少长期的野外观测试验,这个假设一直未被很好地证明。为了证明这个假设,在甘肃民勤的绿洲外围选择了雏形、发育、稳定和死亡四个退化阶段的白刺沙堆,于2008年1月至2012年6月利用中子水分仪和土壤烘干称重法对土壤水分进行了长期观测。结果表明:各样地的土壤含水量均呈现出2008年最大,2009年和2011年次之,2010年最小的趋势。年内变化是春季土壤含水量最低,夏季逐渐增加,随后逐渐减小。在不同发育阶段,雏形阶段的土壤含水量最大,且降水容易下渗。稳定和死亡阶段的白刺沙堆土壤含水量很低,降水难以下渗,只有大的降水事件发生时,水分才可以下渗。因此,稳定和死亡阶段白刺沙堆的土壤水分经常在植物的凋萎点之下,是造成白刺沙堆退化重要原因。证明了"土壤水分减少是白刺沙堆退化的原因"的研究假设。研究结果对今后的植物固沙实践活动会有积极的参考意义。 Abstract:Nitraria dunes can fix a huge amount of moving sand and are one of the most effective ways to protect oasis from moving sand in Northwest China. In recent decades, Nitraria dunes in Northwest China have seriously degraded. As a result, the fixed sand is released, and the oasis is damaged again and again. How to sustain Nitraria dunes long term and prevent the Nitraria plant from dying is an important issue. Based on observation over time, we hypothesized that declining soil water content resulted from an imbalanced soil water budget leading to Nitraria dunes degradation. However this hypothesis hasn't been proved satisfactorily for the lack of long-time field experiments. To prove this hypothesis, we observed soil water content from January 2008 to June 2012 in different degradation stages of Nitraria dunes in the marginal oasis of Minqin, Gansu Province. The methods we used to observe soil water content were the neutron moisture gauge method and weighting method after dried. Results showed that average volumetric soil water content was the highest in 2008 and the lowest in 2010.The variation of volumetric soil water content was the most obvious at the depth of 0-50 cm.The vertical variation pattern of volumetric soil water content was different in different degradation stages. At the depth of 0-90 cm, volumetric soil water content varied the greatest in the early growth stage and rapid growth stage for low water-holding capacity, high seepage power and high air permeability of soil. Three kinds of soil layers divided by soil water variation features occurred in these stages of the Nitraria dunes. These were sudden-change layer, stable layer and increasing layer. However, in the peak growth stage and senescence of Nitraria dunes, volumetric soil water content varied slightly because of crust on the Nitraria dunes surface. Average volumetric soil water content was lower in the early spring, gradually rising in the summer and declining in the autumn.The maximum soil water content occurred in July and September. Moreover, the variation of volumetric soil water content in different seasons was the most obvious at the depth of 0-30 cm. With increasing depth, the volumetric soil water content variation became less. During different degradation stages, the volumetric soil water content in the early growth stage was the highest because precipitation was easy to infiltrate. However, the soil water content was the lowest in the peak growth stage and senescence because precipitation cannot infiltrate without a significant precipitation event. And soil water content in the peak growth stage and senescence of Nitraria dunes was lower than their wilting coefficient. As a result, soil water content cannot satisfy the basic water demand for plant growth which was the principle reason why Nitraria dunes degraded. Through this study, it can be concluded that declining soil water content is the main reason why Nitraria dunes degraded. To take advantage of precipitation efficiently and prevent evapotranspiration on the surface of Nitraria dunes is the key to protecting Nitraria dunes and sand stabilization. This result will provide a positive influence on subsequent vegetation sand-control activities. 参考文献 相似文献 引证文献

Precipitation Trends over Time Using Mann-Kendall and Spearman’s rho Tests in Swat River Basin, Pakistan

Accurately predicting precipitation trends is vital in the economic development of a country. This research investigated precipitation variability across 15 stations in the Swat River basin, Pakistan, over a 51-year study period (1961–2011). Nonparametric Mann-Kendall (MK) and Spearman’s rho (SR) statistical tests were used to detect trends in monthly, seasonal, and annual precipitation, and the trend-free prewhitening approach was applied to eliminate serial correlation in the precipitation time series. The results highlighted a mix of positive (increasing) and negative (decreasing) trends in monthly, seasonal, and annual precipitation. One station in particular, the Saidu Sharif station, showed the maximum number of significant monthly precipitation events, followed by Abazai, Khairabad, and Malakand. On the seasonal time scale, precipitation trends changed from the summer to the autumn season. The Saidu Sharif station revealed the highest positive trend (7.48 mm/year) in annual precipitation. In the entire Swat River basin, statistically insignificant trends were found in the subbasins for the annual precipitation series; however, the Lower Swat subbasin showed the maximum quantitative increase in the precipitation at a rate of 2.18 mm/year. The performance of the MK and SR tests was consistent at the verified significance level.