Littérature scientifique sur le sujet « Transitional soil moisture and evapotranspiration regime »
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Articles de revues sur le sujet "Transitional soil moisture and evapotranspiration regime"
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Schwingshackl, Clemens, Martin Hirschi et Sonia I. Seneviratne. « Quantifying Spatiotemporal Variations of Soil Moisture Control on Surface Energy Balance and Near-Surface Air Temperature ». Journal of Climate 30, no 18 (8 août 2017) : 7105–24. http://dx.doi.org/10.1175/jcli-d-16-0727.1.
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Abstract Soil moisture plays a crucial role for the energy partitioning at Earth’s surface. Changing fractions of latent and sensible heat fluxes caused by soil moisture variations can affect both near-surface air temperature and precipitation. In this study, a simple framework for the dependence of evaporative fraction (the ratio of latent heat flux over net radiation) on soil moisture is used to analyze spatial and temporal variations of land–atmosphere coupling and its effect on near-surface air temperature. Using three different data sources (two reanalysis datasets and one combination of different datasets), three key parameters for the relation between soil moisture and evaporative fraction are estimated: 1) the frequency of occurrence of different soil moisture regimes, 2) the sensitivity of evaporative fraction to soil moisture in the transitional soil moisture regime, and 3) the critical soil moisture value that separates soil moisture- and energy-limited evapotranspiration regimes. The results show that about 30%–60% (depending on the dataset) of the global land area is in the transitional regime during at least half of the year. Based on the identification of transitional regimes, the effect of changes in soil moisture on near-surface air temperature is analyzed. Typical soil moisture variations (standard deviation) can impact air temperature by up to 1.1–1.3 K, while changing soil moisture over its full range in the transitional regime can alter air temperature by up to 6–7 K. The results emphasize the role of soil moisture for atmosphere and climate and constitute a useful benchmark for the evaluation of the respective relationships in Earth system models.
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Akbar, Ruzbeh, Daniel J. Short Gianotti, Kaighin A. McColl, Erfan Haghighi, Guido D. Salvucci et Dara Entekhabi. « Estimation of Landscape Soil Water Losses from Satellite Observations of Soil Moisture ». Journal of Hydrometeorology 19, no 5 (1 mai 2018) : 871–89. http://dx.doi.org/10.1175/jhm-d-17-0200.1.
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Abstract This study presents an observation-driven technique to delineate the dominant boundaries and temporal shifts between different hydrologic regimes over the contiguous United States (CONUS). The energy- and water-limited evapotranspiration regimes as well as percolation to the subsurface are hydrologic processes that dominate the loss of stored water in the soil following precipitation events. Surface soil moisture estimates from the NASA Soil Moisture Active Passive (SMAP) mission, over three consecutive summer seasons, are used to estimate the soil water loss function. Based on analysis of the rates of soil moisture dry-downs, the loss function is the conditional expectation of negative increments in the soil moisture series conditioned on soil moisture itself. An unsupervised classification scheme (with cross validation) is then implemented to categorize regions according to their dominant hydrological regimes based on their estimated loss functions. An east–west divide in hydrologic regimes over CONUS is observed with large parts of the western United States exhibiting a strong water-limited evapotranspiration regime during most of the times. The U.S. Midwest and Great Plains show transitional behavior with both water- and energy-limited regimes present. Year-to-year shifts in hydrologic regimes are also observed along with regional anomalies due to moderate drought conditions or above-average precipitation. The approach is based on remotely sensed surface soil moisture (approximately top 5 cm) at a resolution of tens of kilometers in the presence of soil texture and land cover heterogeneity. The classification therefore only applies to landscape-scale effective conditions and does not directly account for deeper soil water storage.
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Yang, Zesu, Qiang Zhang, Yu Zhang, Ping Yue, Liang Zhang, Jian Zeng et Yulei Qi. « Hydrothermal Factors Influence on Spatial-Temporal Variation of Evapotranspiration-Precipitation Coupling over Climate Transition Zone of North China ». Remote Sensing 14, no 6 (17 mars 2022) : 1448. http://dx.doi.org/10.3390/rs14061448.
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As a land–atmosphere coupling “hot spot”, the northern China climate transition zone has a sharp spatial gradient of hydrothermal conditions, which plays an essential role in shaping the spatial and temporal pattern of evapotranspiration-precipitation coupling, but whose mechanisms still remain unclear. This study analyzes the spatial and temporal variation in land–atmosphere coupling strength (CS) in the climate transitional zone of northern China and its relationship with soil moisture and air temperature. Results show that CS gradually transitions from strong positive in the northwest to negative in the southeast and northeast corners. The spatial distribution of CS is closely related to climatic hydrothermal conditions, where soil moisture plays a more dominant role: CS increases first, and then decreases with increasing soil moisture, with the threshold of soil moisture at 0.2; CS gradually transitions from positive to negative at soil moisture between 0.25 and 0.35; CS shows an exponential decreasing trend with increasing temperature. In terms of temporal variation, CS is strongest in spring and weakens sequentially in summer, autumn, and winter, and has significant interdecadal fluctuations. The trend in CS shifts gradually from significantly negative in the west to a non-significant positive in the east. Soil moisture variability dominates the intra-annual variability of CS in the study regions, and determines the interannual variation of CS in arid and semi-arid areas. Moreover, the main reason for the positive and negative spatial differences in CS in the study area is the different driving regime of evapotranspiration (ET). ET is energy-limited in the southern part of the study area, leading to a positive correlation between ET and lifting condensation level (LCL), while in most of the northern part, ET is water-limited and is negatively correlated with LCL; LCL has a negative correlation with P across the study area, thus leading to a negative ET-P coupling in the south and a positive coupling in the north.
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Buitink, Joost, Anne M. Swank, Martine van der Ploeg, Naomi E. Smith, Harm-Jan F. Benninga, Frank van der Bolt, Coleen D. U. Carranza, Gerbrand Koren, Rogier van der Velde et Adriaan J. Teuling. « Anatomy of the 2018 agricultural drought in the Netherlands using in situ soil moisture and satellite vegetation indices ». Hydrology and Earth System Sciences 24, no 12 (21 décembre 2020) : 6021–31. http://dx.doi.org/10.5194/hess-24-6021-2020.
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Abstract. The soil moisture status near the land surface is a key determinant of vegetation productivity. The critical soil moisture content determines the transition from an energy-limited to a water-limited evapotranspiration regime. This study quantifies the critical soil moisture content by comparison of in situ soil moisture profile measurements of the Raam and Twente networks in the Netherlands, with two satellite-derived vegetation indices (near-infrared reflectance of terrestrial vegetation, NIRv, and vegetation optical depth, VOD) during the 2018 summer drought. The critical soil moisture content is obtained through a piece-wise linear correlation of the NIRv and VOD anomalies with soil moisture on different depths of the profile. This non-linear relation reflects the observation that negative soil moisture anomalies develop weeks before the first reduction in vegetation indices: 2–3 weeks in this case. Furthermore, the inferred critical soil moisture content was found to increase with observation depth, and this relationship is shown to be linear and distinctive per area, reflecting the tendency of roots to take up water from deeper layers when drought progresses. The relations of non-stressed towards water-stressed vegetation conditions on distinct depths are derived using remote sensing, enabling the parameterization of reduced evapotranspiration and its effect on gross primary productivity in models to study the impact of a drought on the carbon cycle.
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Diro, G. T., et L. Sushama. « The Role of Soil Moisture–Atmosphere Interaction on Future Hot Spells over North America as Simulated by the Canadian Regional Climate Model (CRCM5) ». Journal of Climate 30, no 13 (juillet 2017) : 5041–58. http://dx.doi.org/10.1175/jcli-d-16-0068.1.
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Soil moisture–atmosphere interactions play a key role in modulating climate variability and extremes. This study investigates how soil moisture–atmosphere coupling may affect future extreme events, particularly the role of projected soil moisture in modulating the frequency and maximum duration of hot spells over North America, using the fifth-generation Canadian Regional Climate Model (CRCM5). With this objective, CRCM5 simulations, driven by two coupled general circulation models (MPI-ESM and CanESM2), are performed with and without soil moisture–atmosphere interactions for current (1981–2010) and future (2071–2100) climates over North America, for representative concentration pathways (RCPs) 4.5 and 8.5. Analysis indicates that, in future climate, the soil moisture–temperature coupling regions, located over the Great Plains in the current climate, will expand farther north, including large parts of central Canada. Results also indicate that soil moisture–atmosphere interactions will play an important role in modulating temperature extremes in the future by contributing more than 50% to the projected increase in hot-spell days over the southern Great Plains and parts of central Canada, especially for the RCP4.5 scenario. This higher contribution of soil moisture–atmosphere interactions to the future increases in hot-spell days for RCP4.5 is related to the fact that the projected decrease in soil moisture caused the soil to remain in a transitional regime between wet and dry state that is conducive to soil moisture–atmosphere coupling. For the RCP8.5 scenario, on the other hand, the future projected soil state over the southern United States and northern Mexico is too dry to have an impact on evapotranspiration and therefore on temperature.
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McDermid, Sonali Shukla, Carlo Montes, Benjamin I. Cook, Michael J. Puma, Nancy Y. Kiang et Igor Aleinov. « The Sensitivity of Land–Atmosphere Coupling to Modern Agriculture in the Northern Midlatitudes ». Journal of Climate 32, no 2 (26 décembre 2018) : 465–84. http://dx.doi.org/10.1175/jcli-d-17-0799.1.
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AbstractModern agricultural land cover and management are important as regional climate forcings. Previous work has shown that land cover change can significantly impact key climate variables, including turbulent fluxes, precipitation, and surface temperature. However, fewer studies have investigated how intensive crop management can impact background climate conditions, such as the strength of land–atmosphere coupling and evaporative regime. We conduct sensitivity experiments using a state-of-the-art climate model with modified vegetation characteristics to represent modern crop cover and management, using observed crop-specific leaf area indexes and calendars. We quantify changes in land–atmosphere interactions and climate over intensively cultivated regions situated at transitions between moisture- and energy-limited conditions. Results show that modern intensive agriculture has significant and geographically varying impacts on regional evaporative regimes and background climate conditions. Over the northern Great Plains, modern crop intensity increases the model simulated precipitation and soil moisture, weakening hydrologic coupling by increasing surface water availability and reducing moisture limits on evapotranspiration. In the U.S. Midwest, higher growing season evapotranspiration, coupled with winter and spring rainfall declines, reduces regional soil moisture, while crop albedo changes also reduce net surface radiation. This results overall in reduced dependency of regional surface temperature on latent heat fluxes. In central Asia, a combination of reduced net surface energy and enhanced pre–growing season precipitation amplify the energy-limited evaporative regime. These results highlight the need for improved representations of agriculture in global climate models to better account for regional climate impacts and interactions with other anthropogenic forcings.
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Wang, Suping, Qiang Zhang, Ping Yue, Jianshun Wang, Jinhu Yang, Wei Wang, Hongli Zhang et Xueyuan Ren. « Precipitation-Use Efficiency and Its Conversion with Climate Types in Mainland China ». Remote Sensing 14, no 10 (20 mai 2022) : 2467. http://dx.doi.org/10.3390/rs14102467.
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The impacts of climate change on ecosystem productivity and water resources over a long term in China are not well quantified. Precipitation-use efficiency (PUE) is a key parameter that describes carbon and water exchange in terrestrial ecosystems. Research on the response of regional PUE to climate change and its driving forces is of great significance to climate-change mitigation and the sustainable development of regional ecology. Based on an improved actual evapotranspiration (ETa) model, the responses of ETa, net primary productivity (NPP), and PUE to climate change in different climatic regions of China were analyzed; the contributions of various environmental factors to PUE changes were quantified; and the conversion characteristics and regulatory mechanisms of the PUE regime in different climatic regions were identified. The results indicate that the improved ETa model, after considering the limiting effect of energy on ETa in humid regions, can simulate the ETa distribution in China well. Over the past 58 years (1960–2017), ETa and NPP have increased in the western regions and decreased in the eastern regions, with the boundary at 103° E. PUE presents a “low-high-low” spatial distribution from northwest to southeast in China. It is noteworthy that there was a zonal distribution for a high value area of PUE, which coincided with the summer monsoon transition zone. The soil moisture (SM) increase in arid regions is the main driving force of the PUE increase, whereas the annual net radiation (Rn) change in humid regions is the main driving force of the PUE change. The transition zone is the conversion zone, where the prevailing factor limiting vegetation growth transitions from water to energy.
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Ibragimova, Kh. « Irrigation Effect on Evapotranspiration (in Absheron) ». Bulletin of Science and Practice 6, no 11 (15 novembre 2020) : 179–87. http://dx.doi.org/10.33619/2414-2948/60/21.
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In the presented article, the results of the use of dispersed irrigation are considered. This method helps to reduce the ambient temperature, increase soil moisture, establish an optimal irrigation regime, reduce the need for water resources, prevent depression of photosynthesis of alfalfa agrophytocenosis under Absheron conditions. It is recommended to carry out dispersed irrigation on the soil surface at temperatures above 28 °C. The best results were obtained under the condition of the combined application of dispersed irrigation with sprinkling, especially in dry years.
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WANG, Cong, Shuai WANG, Bojie FU, Lu ZHANG, Nan LU et Lei JIAO. « Stochastic soil moisture dynamic modelling : a case study in the Loess Plateau, China ». Earth and Environmental Science Transactions of the Royal Society of Edinburgh 109, no 3-4 (septembre 2018) : 437–44. http://dx.doi.org/10.1017/s1755691018000658.
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ABSTRACTSoil moisture is a key factor in the ecohydrological cycle in water-limited ecosystems, and it integrates the effects of climate, soil, and vegetation. The water balance and the hydrological cycle are significantly important for vegetation restoration in water-limited regions, and these dynamics are still poorly understood. In this study, the soil moisture and water balance were modelled with the stochastic soil water balance model in the Loess Plateau, China. This model was verified by monitoring soil moisture data of black locust plantations in the Yangjuangou catchment in the Loess Plateau. The influences of a rainfall regime change on soil moisture and water balance were also explored. Three meteorological stations were selected (Yulin, Yan'an, and Luochuan) along the precipitation gradient to detect the effects of rainfall spatial variability on the soil moisture and water balance. The results showed that soil moisture tended to be more frequent at low levels with decreasing precipitation, and the ratio of evapotranspiration under stress in response to rainfall also changed from 74.0% in Yulin to 52.3% in Luochuan. In addition, the effects of a temporal change in rainfall regime on soil moisture and water balance were explored at Yan'an. The soil moisture probability density function moved to high soil moisture in the wet period compared to the dry period of Yan'an, and the evapotranspiration under stress increased from 59.5% to 72% from the wet period to the dry period. The results of this study prove the applicability of the stochastic model in the Loess Plateau and reveal its potential for guiding the vegetation restoration in the next stage.
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Buchtele, J., M. Tesař et P. Krám. « Variability of water regime in the forested experimental catchments ». Soil and Water Research 4, Special Issue 2 (19 mars 2010) : S93—S101. http://dx.doi.org/10.17221/1366-swr.
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The water regime variability in most catchments is frequently influenced not only by the changes of the vegetation cover in the annual cycle but also by its development in the time span of decades. That means that the resulting evapotranspiration depends not only on the actual climatic situation but also on the soil moisture. The simulations of the rainfall-runoff process have been used with the intention to follow the possible role of the developing land cover. The differences between the observed and simulated flows in relatively long periods can be considered as an appropriate tool for the assessment of the water regime changes, in which the evapotranspiration demand variability is a significant phenomenon.
Thèses sur le sujet "Transitional soil moisture and evapotranspiration regime"
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Castelli, Giulio. « Evidences of climate mitigation from Landscape Restoration and Water Harvesting : A Remote Sensing Approach ». Doctoral thesis, 2018. http://hdl.handle.net/2158/1131579.
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When changes are made in a landscape, changes are made to the microclimate. When farmers plant trees in or around their field, and when communities dig bunds to improve water retention, they change the local climate around them. In the current global climate debate, adaptation and mitigation are dominant concepts, while no attention has been paid to local solutions that can enhance local climatic resilience of landscapes. In arid to semi-arid areas of the world, measures such as Landscape Restoration and Water Harvesting (LRWH) are implemented to revert land degradation and increase soil moisture, reducing runoff losses. The present work aims to analyse to what extent storing soil moisture, with adequate land and water management practices, can reduce temperatures in the hot months after the rainy season, as a consequence of Soil Moisture-Temperature Coupling. Since it is demonstrated how soil moisture deficit can enhance heatwaves in diverse regions of the world, it is hypothesized that increasing soil moisture availability, during the dry and hot periods, can mitigate hot temperatures. The analysis has been carried out for Enabered catchment, in Tigray Region, Ethiopia, where the rainy season runs from June to August. Here, large scale LRWH implementation ended in 2008. An analysis based on remote sensing data has been carried out to evaluate (1) to what extent LRWH implementation can enhance soil moisture conservation at catchment scale; (2) to what extent LRWH implementation can mitigate temperatures in the dry season at catchment scale; and (3) if SMTC were evident. Results showed an increased capacity of the catchment to retain soil moisture produced in the rainy season until September (P < 0.01) and October (P < 0.1) and reduced temperatures for September (P < 0.1), October (P < 0.01) and November (P < 0.05), with decreases of Land Surface Temperatures up to 1.74 °C. A simple, parsimonious linear regression model demonstrated that SMTC is evident at catchment scale and that the implementation of LRWH measures provided a climate mitigation effect in the watershed. The present work can reinforce the call for an increased adoption of water harvesting, land restoration and green water management, to increase the resilience of agricultural ecosystem located in arid and semi-arid areas, that represent a key element to achieve global food security.