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Diagnosing the causes of AMOC slowdown in a coupled model: a cautionary tale 在耦合模式中诊断 AMOC 减慢的原因:一个警世故事
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-03-22 DOI: 10.5194/esd-15-293-2024
Justin Gérard, Michel Crucifix
Abstract. It is now established that the increase in atmospheric CO2 is likely to cause a weakening, or perhaps a collapse, of the Atlantic Meridional Overturning Circulation (AMOC). To investigate the mechanisms of this response in CMIP5 models, Levang and Schmitt (2020) have estimated the geostrophic streamfunction in these models offline and have decomposed the simulated changes into a contribution caused by the variations in temperature and salinity. They concluded that under a warming scenario, and for most models, the weakening of the AMOC is fundamentally driven by temperature anomalies, while freshwater forcing actually acts to stabilise it. However, given that both 3-D fields of ocean temperature and salinity are expected to respond to a forcing at the ocean surface, it is unclear to what extent the diagnostic is informative about the nature of the forcing. To clarify this question, we used the Earth system Model of Intermediate Complexity (EMIC), cGENIE, which is equipped with the C-GOLDSTEIN friction-geostrophic model. First, we reproduced the experiments simulating the Representative Concentration Pathway 8.5 (RCP8.5) warming scenario and observed that cGENIE behaves similarly to the majority of the CMIP5 models considered by Levang and Schmitt (2020), with the response dominated by the changes in the thermal structure of the ocean. Next, we considered hysteresis experiments associated with (1) water hosing and (2) CO2 increase and decrease. In all experiments, initial changes in the ocean streamfunction appear to be primarily caused by the changes in the temperature distribution, with variations in the 3-D distribution of salinity only partly compensating for the temperature contribution. These experiments also reveal limited sensitivity to changes in the ocean's salinity inventory. That the diagnostics behave similarly in CO2 and freshwater forcing scenarios suggests that the output of the diagnostic proposed in Levang and Schmitt (2020) is mainly determined by the internal structure of the ocean circulation rather than by the forcing applied to it. Our results illustrate the difficulty of inferring any information about the applied forcing from the thermal wind diagnostic and raise questions about the feasibility of designing a diagnostic or experiment that could identify which aspect of the forcing (thermal or haline) is driving the weakening of the AMOC.
摘要目前已经确定,大气中二氧化碳的增加很可能导致大西洋经向翻转环流(AMOC)的减弱甚至崩溃。为了研究 CMIP5 模式中这种反应的机理,Levang 和 Schmitt(2020 年)离线估算了这些模式中的地转流功能,并将模拟的变化分解为温度和盐度变化的贡献。他们的结论是,在气候变暖的情况下,对大多数模式而言,AMOC 的减弱从根本上说是由温度异常驱动的,而淡水强迫实际上起到了稳定作用。然而,由于海洋温度和盐度的三维场都要对海洋表面的强迫做出反应,因此还不清楚诊断在多大程度上能说明强迫的性质。为了弄清这个问题,我们使用了中等复杂性地球系统模式(EMIC)cGENIE,该模式配备了 C-GOLDSTEIN 摩擦地转模式。首先,我们重现了模拟代表性浓度途径 8.5(RCP8.5)变暖情景的实验,观察到 cGENIE 的表现与 Levang 和 Schmitt(2020 年)所考虑的大多数 CMIP5 模型类似,其响应主要受海洋热结构变化的影响。接下来,我们考虑了与(1)水冲洗和(2)二氧化碳增减相关的滞后实验。在所有实验中,海洋流函数的初始变化似乎主要是由温度分布的变化引起的,盐度三维分布的变化只能部分补偿温度的影响。这些实验还显示了对海洋盐度分布变化的有限敏感性。诊断结果在二氧化碳和淡水强迫情景下表现相似,这表明 Levang 和 Schmitt(2020 年)提出的诊断结果主要是由海洋环流的内部结构决定的,而不是由对其施加的强迫决定的。我们的结果表明,从热风诊断中很难推断出任何有关外加强迫的信息,并提出了设计一种诊断或实验的可行性问题,这种诊断或实验可以确定强迫(热强迫或卤化强迫)的哪一个方面在驱动 AMOC 的减弱。
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引用次数: 0
Effects of idealized land cover and land management changes on the atmospheric water cycle 理想化土地覆被和土地管理变化对大气水循环的影响
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-03-20 DOI: 10.5194/esd-15-265-2024
Steven De Hertog, Carmen Lopez-Fabara, R. J. van der Ent, J. Keune, D. Miralles, Raphael Portmann, S. Schemm, Felix Havermann, Suqi Guo, Fei Luo, I. Manola, Q. Lejeune, J. Pongratz, C. Schleussner, S. Seneviratne, W. Thiery
Abstract. Land cover and land management changes (LCLMCs) play an important role in achieving low-end warming scenarios through land-based mitigation. However, their effects on moisture fluxes and recycling remain uncertain, although they have important implications for the future viability of such strategies. Here, we analyse the impact of idealized LCLMC scenarios on atmospheric moisture transport in three different Earth system model (ESMs): the Community Earth System Model (CESM), the Max Planck Institute Earth System Model (MPI-ESM), and the European Consortium Earth System Model (EC-EARTH). The LCLMC scenarios comprise of a full cropland world, a fully afforested world, and a cropland world with unlimited irrigation expansion. The effects of these LCLMC in the different ESMs are analysed for precipitation, evaporation, and vertically integrated moisture flux convergence to understand the LCLMC-induced changes in the atmospheric moisture cycle. Then, a moisture tracking algorithm is applied to assess the effects of LCLMC on moisture recycling at the local (grid cell level) and the global scale (continental moisture recycling). By applying a moisture tracking algorithm on fully coupled ESM simulations we are able to quantify the complete effects of LCLMC on moisture recycling (including circulation changes), which are generally not considered in moisture recycling studies. Our results indicate that cropland expansion is generally causing a drying and reduced local moisture recycling, while afforestation and irrigation expansion generally cause wetting and increased local moisture recycling. However, the strength of this effect varies across ESMs and shows a large dependency on the dominant driver. Some ESMs show a dominance of large-scale atmospheric circulation changes while other ESMs show a dominance of local to regional changes in the atmospheric water cycle only within the vicinity of the LCLMC. Overall, these results corroborate that LCLMC can induce substantial effects on the atmospheric water cycle and moisture recycling, both through local effects and changes in atmospheric circulation. However, more research is needed to constrain the uncertainty of these effects within ESMs to better inform future land-based mitigation strategies.
摘要。土地覆被和土地管理变化(LCLMCs)在通过陆基减缓实现低端变暖情景方面发挥着重要作用。然而,它们对水汽通量和循环的影响仍不确定,尽管这些影响对此类战略的未来可行性有重要影响。在这里,我们分析了理想化的 LCLMC 情景对三种不同地球系统模式(ESM)中大气水汽传输的影响:共同体地球系统模式(CESM)、马克斯-普朗克研究所地球系统模式(MPI-ESM)和欧洲财团地球系统模式(EC-EARTH)。LCLMC 情景包括完全耕地世界、完全植树造林世界和无限扩大灌溉面积的耕地世界。我们分析了这些 LCLMC 在不同 ESM 中对降水、蒸发和垂直整合水汽通量会聚的影响,以了解 LCLMC 引起的大气水汽循环变化。然后,应用水汽跟踪算法评估 LCLMC 对局部(网格单元水平)和全球(大陆水汽循环)水汽循环的影响。通过在完全耦合的 ESM 模拟中应用水汽跟踪算法,我们能够量化 LCLMC 对水汽循环的全部影响(包括环流变化),而水汽循环研究通常不考虑这些影响。我们的研究结果表明,耕地面积的扩大通常会导致气候干燥和局部水汽循环减少,而植树造林和灌溉面积的扩大通常会导致气候湿润和局部水汽循环增加。然而,这种影响的强度在不同的无害环境管理中各不相同,并且在很大程度上取决于主要的驱动因素。一些 ESMs 显示大尺度大气环流变化占主导地位,而另一些 ESMs 则显示仅在 LCLMC 附近的局部到区域大气水循环变化占主导地位。总之,这些结果证实了 LCLMC 可通过局部效应和大气环流变化对大气水循环和水汽循环产生重大影响。不过,还需要进行更多的研究,以限制无害环境管理中这些影响的不确定性,从而更好地为未来的陆基减缓战略提供信息。
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引用次数: 0
Possible role of anthropogenic climate change in the record-breaking 2020 Lake Victoria levels and floods 人为气候变化在 2020 年维多利亚湖水位破纪录和洪水中可能扮演的角色
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-03-18 DOI: 10.5194/esd-15-225-2024
Rosa Pietroiusti, Inne Vanderkelen, Friederike E. L. Otto, Clair R. Barnes, Lucy Temple, Mary Akurut, Philippe Bally, N. V. van Lipzig, W. Thiery
Abstract. Heavy rainfall in eastern Africa between late 2019 and mid 2020 caused devastating floods and landslides throughout the region. These rains drove the levels of Lake Victoria to a record-breaking maximum in the second half of May 2020. The combination of high lake levels, consequent shoreline flooding, and flooding of tributary rivers caused hundreds of casualties and damage to housing, agriculture, and infrastructure in the riparian countries of Uganda, Kenya, and Tanzania. Media and government reports linked the heavy precipitation and floods to anthropogenic climate change, but a formal scientific attribution study has not been carried out so far. In this study, we characterize the spatial extent and impacts of the floods in the Lake Victoria basin and then investigate to what extent human-induced climate change influenced the probability and magnitude of the record-breaking lake levels and associated flooding by applying a multi-model extreme event attribution methodology. Using remote-sensing-based flood mapping tools, we find that more than 29 000 people living within a 50 km radius of the lake shorelines were affected by floods between April and July 2020. Precipitation in the basin was the highest recorded in at least 3 decades, causing lake levels to rise by 1.21 m between late 2019 and mid 2020. The flood, defined as a 6-month rise in lake levels as extreme as that observed in the lead-up to May 2020, is estimated to be a 63-year event in the current climate. Based on observations and climate model simulations, the best estimate is that the event has become more likely by a factor of 1.8 in the current climate compared to a pre-industrial climate and that in the absence of anthropogenic climate change an event with the same return period would have led lake levels to rise by 7 cm less than observed. Nonetheless, uncertainties in the attribution statement are relatively large due to large natural variability and include the possibility of no observed attributable change in the probability of the event (probability ratio, 95 % confidence interval 0.8–15.8) or in the magnitude of lake level rise during an event with the same return period (magnitude change, 95 % confidence interval 0–14 cm). In addition to anthropogenic climate change, other possible drivers of the floods and their impacts include human land and water management, the exposure and vulnerability of settlements and economic activities located in flood-prone areas, and modes of climate variability that modulate seasonal precipitation. The attribution statement could be strengthened by using a larger number of climate model simulations, as well as by quantitatively accounting for non-meteorological drivers of the flood and potential unforced modes of climate variability. By disentangling the role of anthropogenic climate change and natural variability in the high-impact 2020 floods in the Lake Victoria basin, this paper contributes to a better understanding of changing
摘要2019 年末至 2020 年中,非洲东部的强降雨在整个地区造成了毁灭性的洪水和山体滑坡。这些降雨使维多利亚湖的水位在 2020 年 5 月下半月达到破纪录的最高值。高湖水位、随之而来的海岸线洪水以及支流河流洪水,在乌干达、肯尼亚和坦桑尼亚等沿岸国家造成了数百人伤亡,并对住房、农业和基础设施造成了破坏。媒体和政府报道将强降水和洪水与人为气候变化联系在一起,但迄今为止尚未开展正式的科学归因研究。在本研究中,我们描述了维多利亚湖流域洪水的空间范围和影响,然后通过应用多模型极端事件归因方法,研究人为气候变化在多大程度上影响了破纪录的湖泊水位和相关洪水的概率和规模。利用基于遥感的洪水绘图工具,我们发现在 2020 年 4 月至 7 月期间,居住在湖岸半径 50 公里范围内的 29000 多人受到了洪水的影响。该流域的降水量创下了至少 30 年来的最高记录,导致湖泊水位在 2019 年末至 2020 年中上升了 1.21 米。洪水的定义是 6 个月内湖泊水位上升到 2020 年 5 月之前所观测到的极端水平,据估计,在目前的气候条件下,这是 63 年一遇的洪水。根据观测结果和气候模型模拟,最佳估计是,与工业化前的气候相比,在当前气候下发生该事件的可能性增加了 1.8 倍,如果没有人为气候变化,相同重现期的事件会导致湖泊水位比观测到的上升少 7 厘米。然而,由于自然变异性较大,归因声明中的不确定性也相对较大,包括在事件发生概率(概率比,95% 置信区间为 0.8-15.8)或相同重现期事件中湖泊水位上升幅度(幅度变化,95% 置信区间为 0-14 厘米)没有观测到可归因变化的可能性。除人为气候变化外,洪水及其影响的其他可能驱动因素还包括人类的土地和水资源管理、位于洪水易发地区的居民点和经济活动的暴露程度和脆弱性,以及调节季节性降水的气候变异模式。通过使用更多的气候模型模拟,以及定量考虑洪水的非气象驱动因素和潜在的非强制气候变异模式,可以加强归因说明。通过厘清人为气候变化和自然变异在维多利亚湖流域 2020 年高影响洪水中的作用,本文有助于更好地理解非洲东部和非洲大湖区不断变化的极端水文气象。
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引用次数: 0
Sea-ice thermodynamics can determine waterbelt scenarios for Snowball Earth 海冰热力学可以确定雪球地球的水带方案
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-03-15 DOI: 10.5194/esd-15-215-2024
Johannes Hörner, Aiko Voigt
Abstract. Snowball Earth refers to multiple periods in the Neoproterozoic during which geological evidence indicates that the Earth was largely covered in ice. A Snowball Earth results from a runaway ice–albedo feedback, but there is an ongoing debate about how the feedback stopped: with fully ice-covered oceans or with a narrow strip of open water around the Equator. The latter states are called waterbelt states and are an attractive explanation for Snowball Earth events because they provide a refugium for the survival of photosynthetic aquatic life, while still explaining Neoproterozoic geology. Waterbelt states can be stabilized by bare sea ice in the subtropical desert regions, which lowers the surface albedo and stops the runaway ice–albedo feedback. However, the choice of sea-ice model in climate simulations significantly impacts snow cover on ice and, consequently, surface albedo. Here, we investigate the robustness of waterbelt states with respect to the thermodynamical representation of sea ice. We compare two thermodynamical sea-ice models, an idealized zero-layer Semtner model, in which sea ice is always in equilibrium with the atmosphere and ocean, and a three-layer Winton model that is more sophisticated and takes into account the heat capacity of ice. We deploy the global icosahedral non-hydrostatic atmospheric (ICON-A) model in an idealized aquaplanet setup and calculate a comprehensive set of simulations to determine the extent of the waterbelt hysteresis. We find that the thermodynamic representation of sea ice strongly influences snow cover on sea ice over the range of all simulated climate states. Including heat capacity by using the three-layer Winton model increases snow cover and enhances the ice–albedo feedback. The waterbelt hysteresis found for the zero-layer model disappears in the three-layer model, and no stable waterbelt states are found. This questions the relevance of a subtropical bare sea-ice region for waterbelt states and might help explain drastically varying model results on waterbelt states in the literature.
摘要雪球地球是指在新近纪的多个时期,地质证据显示地球大部分被冰覆盖。雪球地球是冰-反渗透反馈失控的结果,但关于反馈是如何停止的一直存在争论:是海洋完全被冰覆盖,还是赤道周围有一条狭长的开放水带。后一种状态被称为水带状态,是对 "雪球地球 "事件的一种有吸引力的解释,因为它们为光合水生生物的生存提供了一个温床,同时还能解释新近纪地质。亚热带沙漠地区裸露的海冰可以稳定水带状态,从而降低地表反照率,阻止冰-反照率反馈失控。然而,气候模拟中海冰模型的选择会对冰雪覆盖产生重大影响,进而影响地表反照率。在此,我们研究了水带状态对海冰热力学表示的稳健性。我们比较了两种海冰热力学模型,一种是理想化的零层塞姆特纳模型(在该模型中,海冰始终与大气和海洋处于平衡状态),另一种是更复杂的三层温顿模型(该模型考虑了冰的热容量)。我们在理想化的水行星设置中部署了全球二十面体非静水压大气(ICON-A)模型,并进行了一系列综合模拟计算,以确定水带滞后的程度。我们发现,在所有模拟气候状态的范围内,海冰的热力学表示方法对海冰的积雪覆盖有很大影响。通过使用三层温顿模型将热容量包括在内,可增加雪盖并增强冰-反照率反馈。在零层模型中发现的水带滞后现象在三层模型中消失了,没有发现稳定的水带状态。这对亚热带裸露海冰区与水带状态的相关性提出了质疑,并可能有助于解释文献中关于水带状态的模型结果的巨大差异。
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引用次数: 0
Hemispherically symmetric strategies for stratospheric aerosol injection 平流层气溶胶注入的半球对称战略
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-03-13 DOI: 10.5194/esd-15-191-2024
Yan Zhang, D. MacMartin, D. Visioni, E. Bednarz, Ben Kravitz
Abstract. Stratospheric aerosol injection (SAI) comes with a wide range of possible design choices, such as the location and timing of the injection. Different stratospheric aerosol injection strategies can yield different climate responses; therefore, understanding the range of possible climate outcomes is crucial to making informed future decisions on SAI, along with the consideration of other factors. Yet, to date, there has been no systematic exploration of a broad range of SAI strategies. This limits the ability to determine which effects are robust across different strategies and which depend on specific injection choices. This study systematically explores how the choice of SAI strategy affects climate responses in one climate model. Here, we introduce four hemispherically symmetric injection strategies, all of which are designed to maintain the same global mean surface temperature: an annual injection at the Equator (EQ), an annual injection of equal amounts of SO2 at 15° N and 15° S (15N+15S), an annual injection of equal amounts of SO2 at 30° N and 30° S (30N+30S), and a polar injection strategy that injects equal amounts of SO2 at 60° N and 60° S only during spring in each hemisphere (60N+60S). We compare these four hemispherically symmetric SAI strategies with a more complex injection strategy that injects different quantities of SO2 at 30° N, 15° N, 15° S, and 30° S in order to maintain not only the global mean surface temperature but also its large-scale horizontal gradients. All five strategies are simulated using version 2 of the Community Earth System Model with the middle atmosphere version of the Whole Atmosphere Community Climate model, version 6, as the atmospheric component, CESM2(WACCM6-MA), with the global warming scenario, Shared Socioeconomic Pathway (SSP)2-4.5. We find that the choice of SAI strategy affects the spatial distribution of aerosol optical depths, injection efficiency, and various surface climate responses. In addition, injecting in the subtropics produces more global cooling per unit injection, with the EQ and the 60N+60S cases requiring, respectively, 59 % and 50 % more injection than the 30N+30S case to meet the same global mean temperature target. Injecting at higher latitudes results in larger Equator-to-pole temperature gradients. While all five strategies restore Arctic September sea ice, the high-latitude injection strategy is more effective due to the SAI-induced cooling occurring preferentially at higher latitudes. These results suggest trade-offs wherein different strategies appear better or worse, depending on which metrics are deemed important.
摘要平流层气溶胶注入(SAI)有多种可能的设计选择,如注入的位置和时间。不同的平流层气溶胶注入策略会产生不同的气候响应;因此,了解可能的气候结果范围对于未来就气溶胶注入做出明智决策以及考虑其他因素至关重要。然而,迄今为止,还没有对各种 SAI 策略进行过系统的探索。这就限制了确定哪些效应在不同战略中是稳健的,以及哪些效应取决于具体的注入选择的能力。本研究在一个气候模式中系统地探讨了 SAI 策略的选择如何影响气候响应。在这里,我们引入了四种半球对称注入策略,所有这些策略都是为了维持相同的全球平均表面温度:每年在赤道注入(EQ),每年在北纬 15°和南纬 15°注入等量的二氧化硫(15N+15S),每年在北纬 30°和南纬 30°注入等量的二氧化硫(30N+30S),以及一种极地注入策略,即只在北纬 60°和南纬 60°的春季各注入等量的二氧化硫(60N+60S)。我们将这四种半球对称的 SAI 策略与一种更复杂的注入策略进行了比较,该策略在北纬 30°、北纬 15°、南纬 15°和南纬 30°注入不同数量的二氧化硫,以维持全球平均表面温度及其大尺度水平梯度。所有五种策略都是利用共同体地球系统模型第 2 版,以全大气共同体气候模型第 6 版的中间大气版本 CESM2(WACCM6-MA)作为大气成分,在全球变暖情景共享社会经济路径(SSP)2-4.5 下进行模拟的。我们发现,SAI 策略的选择会影响气溶胶光学深度的空间分布、注入效率以及各种地表气候响应。此外,在亚热带注入气溶胶会产生更多的单位注入量全球降温效应,要达到相同的全球平均气温目标,EQ 和 60N+60S 情况比 30N+30S 情况分别需要多注入 59% 和 50%的气溶胶。在更高纬度注入会导致更大的赤道到极点温度梯度。虽然所有五种策略都能恢复北极九月的海冰,但高纬度注入策略更为有效,因为 SAI 引起的降温优先发生在高纬度地区。这些结果表明,不同的策略有好有坏,这取决于哪些指标被认为是重要的。
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引用次数: 0
Impact of groundwater representation on heat events in regional climate simulations over Europe 欧洲区域气候模拟中地下水表示对热事件的影响
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-03-05 DOI: 10.5194/esd-15-167-2024
L. Poshyvailo-Strube, Niklas Wagner, K. Goergen, C. Furusho‐Percot, C. Hartick, S. Kollet
Abstract. The representation of groundwater is simplified in most regional climate models (RCMs), potentially leading to biases in the simulations. This study introduces a unique dataset from the regional Terrestrial Systems Modelling Platform (TSMP) driven by the Max Planck Institute Earth System Model at Low Resolution (MPI-ESM-LR) boundary conditions in the context of dynamical downscaling of global climate models (GCMs) for climate change studies. TSMP explicitly simulates full 3D soil and groundwater dynamics together with overland flow, including complete water and energy cycles from the bedrock to the top of the atmosphere. By comparing the statistics of heat events, i.e., a series of consecutive days with a near-surface temperature exceeding the 90th percentile of the reference period, from TSMP and those from GCM–RCM simulations with simplified groundwater dynamics from the COordinated Regional Climate Downscaling EXperiment (CORDEX) for the European domain, we aim to improve the understanding of how groundwater representation affects heat events in Europe. The analysis was carried out using RCM outputs for the summer seasons of 1976–2005 relative to the reference period of 1961–1990. While our results show that TSMP simulates heat events consistently with the CORDEX ensemble, there are some systematic differences that we attribute to the more realistic representation of groundwater in TSMP. Compared to the CORDEX ensemble, TSMP simulates fewer hot days (i.e., days with a near-surface temperature exceeding the 90th percentile of the reference period) and lower interannual variability and decadal change in the number of hot days on average over Europe. TSMP systematically simulates fewer heat waves (i.e., heat events lasting 6 d or more) compared to the CORDEX ensemble; moreover, they are shorter and less intense. The Iberian Peninsula is particularly sensitive with respect to groundwater. Therefore, incorporating an explicit 3D groundwater representation in RCMs may be a key in reducing biases in simulated duration, intensity, and frequency of heat waves in Europe. The results highlight the importance of hydrological processes for the long-term regional climate simulations and provide indications of possible potential implications for climate change projections.
摘要在大多数区域气候模式(RCMs)中,地下水的表示被简化,可能导致模拟结果出现偏差。本研究介绍了区域陆地系统建模平台(TSMP)的独特数据集,该数据集由马克斯-普朗克研究所地球系统低分辨率模型(MPI-ESM-LR)边界条件驱动,用于气候变化研究的全球气候模型(GCM)的动态降尺度。TSMP 明确模拟了全三维土壤和地下水动态以及陆地流,包括从基岩到大气顶部的完整水循环和能量循环。通过比较来自 TSMP 和来自 GCM-RCM 模拟的热事件(即近地表温度超过参照期第 90 百分位数的一系列连续天数)统计数据,以及来自欧洲地区协调区域气候降尺度试验(CORDEX)的简化地下水动力学数据,我们旨在加深对地下水表征如何影响欧洲热事件的理解。分析使用的是相对于 1961-1990 年参照期的 1976-2005 年夏季 RCM 输出结果。结果表明,TSMP 与 CORDEX 集合对高温事件的模拟结果一致,但也存在一些系统性差异,我们将这些差异归因于 TSMP 对地下水更真实的表现。与 CORDEX 集合相比,TSMP 模拟的高温日数(即近地面温度超过参照期第 90 百分位数的天数)更少,欧洲平均高温日数的年际变化和十年变化更小。与 CORDEX 合集相比,TSMP 系统模拟的热浪(即持续 6 天或更长时间的高温事件)更少,而且热浪的时间更短,强度更低。伊比利亚半岛对地下水特别敏感。因此,在 RCM 中加入明确的三维地下水表示可能是减少欧洲热浪模拟持续时间、强度和频率偏差的关键。这些结果突显了水文过程对长期区域气候模拟的重要性,并为气候变化预测提供了可能的潜在影响。
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引用次数: 0
Scaling artificial heat islands to enhance precipitation in the United Arab Emirates 在阿拉伯联合酋长国扩大人工热岛规模以增加降水量
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-30 DOI: 10.5194/esd-15-109-2024
Oliver Branch, L. Jach, T. Schwitalla, K. Warrach‐Sagi, V. Wulfmeyer
Abstract. Potential for regional climate engineering is gaining interest as a means of solving regional environmental problems like water scarcity and high temperatures. In the hyper-arid United Arab Emirates (UAE), water scarcity is reaching a crisis point due to high consumption and over-extraction and is being exacerbated by climate change. To counteract this problem, the UAE has conducted cloud-seeding operations and intensive desalination for many years but is now considering other means of increasing water resources. Very large “artificial black surfaces” (ABSs), made of black mesh, black-painted, or solar photovoltaic (PV) panels have been proposed as a means of enhancing convective precipitation via surface heating and amplification of vertical motion. Under the influence of the daily UAE sea breeze, this can lead to convection initiation under the right conditions. Currently it is not known how strong this rainfall enhancement would be or what scale of black surface would need to be employed. This study simulates the impacts at different ABS scales using the WRF-Noah-MP model chain and investigates impacts on precipitation quantities and underlying convective processes. Simulations of five square ABSs of 10, 20, 30, 40, and 50 km sizes were made on four 1 d cases, each for a period of 24 h. These were compared with a Control model run, with no land use change, to quantify impacts. The ABSs themselves were simulated by altering land cover static data and prescribing a unique set of land surface parameters like albedo and roughness length. On all 4 d, rainfall is enhanced by low-albedo surfaces of 20 km or larger, primarily through a reduction of convection inhibition and production of convergence lines and buoyant updrafts. The 10 km square ABS had very little impact. From 20 km upwards there is a strong scale dependency, with ABS size influencing the strength of convective processes and volume of rainfall. In terms of rainfall increases, 20 km produces a mean rainfall increase over the Control simulation of 571 616 m3 d−1, with the other sizes as follows: 30 km (∼ 1 million m3 d−1), 40 km (∼ 1.5 million m3 d−1), and 50 km (∼ 2.3 million m3 d−1). If we assume that such rainfall events happen only on 10 d in a year, this would equate to respective annual water supplies for > 31 000, > 50 000, > 79 000, and > 125 000 extra people yr−1 at UAE per capita consumption rates. Thus, artificial heat islands made from black panels or solar PV offer a means of enhancing rainfall in arid regions like the UAE and should be made a high priority for further research.
摘要区域气候工程作为解决缺水和高温等区域环境问题的一种手段,其潜力正受到越来越多的关注。在极度干旱的阿拉伯联合酋长国(阿联酋),由于高消耗和过度开采,水资源短缺已达到危机点,而气候变化又加剧了这一问题。为了应对这一问题,阿联酋多年来一直在进行云层播种作业和密集的海水淡化,但现在正在考虑采用其他方法来增加水资源。有人提出了用黑色网眼、黑色涂料或太阳能光伏(PV)板制成的超大型 "人造黑色表面"(ABS),作为通过表面加热和垂直运动放大来增强对流降水的一种手段。在每日阿联酋海风的影响下,这可能会在适当条件下导致对流的发生。目前还不清楚这种降雨增强的强度有多大,也不知道需要采用多大尺度的黑色表面。本研究利用 WRF-Noah-MP 模式链模拟了不同 ABS 尺度的影响,并研究了对降水量和基本对流过程的影响。对 10、20、30、40 和 50 km 大小的五个方形 ABS 进行了四次 1 d 模拟,每次模拟 24 h。通过改变土地覆被静态数据和规定一套独特的地表参数(如反照率和粗糙度长度),模拟了 ABS 本身。在所有 4 天中,20 千米或更大的低反照率地表都会增加降雨量,主要是通过减少对流抑制以及产生辐合线和浮力上升气流。10 km 平方 ABS 的影响很小。从 20 千米以上的范围来看,ABS 的大小对对流过程的强度和降雨量有很强的依赖性。就降雨量的增加而言,与对照模拟相比,20 千米的平均降雨量增加了 571 616 立方米/天,其他尺寸的降雨量增加情况如下:30 千米(100 万立方米/天-1)、40 千米(150 万立方米/天-1)和 50 千米(230 万立方米/天-1)。如果我们假定这种降雨事件每年只发生 10 天,那么按照阿联酋的人均消耗率计算,这相当于每年分别为 > 31 000、 > 50 000、 > 79 000 和 > 125 000 人增加供水。因此,利用黑板或太阳能光伏发电制造的人工热岛是增加阿联酋等干旱地区降雨量的一种方法,应作为进一步研究的重中之重。
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引用次数: 0
Future water storage changes over the Mediterranean, Middle East, and North Africa in response to global warming and stratospheric aerosol intervention 全球变暖和平流层气溶胶干预对地中海、中东和北非未来蓄水量变化的影响
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-29 DOI: 10.5194/esd-15-91-2024
Abolfazl Rezaei, Khalil Karami, S. Tilmes, John C. Moore
Abstract. Water storage plays a profound role in the lives of people across the Middle East and North Africa (MENA) as it is the most water-stressed region worldwide. The lands around the Caspian and Mediterranean seas are simulated to be very sensitive to future climate warming. Available water capacity depends on hydroclimate variables such as temperature and precipitation that will depend on socioeconomic pathways and changes in climate. This work explores changes in both the mean and extreme terrestrial water storage (TWS) under an unmitigated greenhouse gas (GHG) scenario (SSP5-8.5) and stratospheric aerosol intervention (SAI) designed to offset GHG-induced warming above 1.5 ∘C and compares both with historical period simulations. Both mean TWS and extreme TWS are projected to significantly decrease under SSP5-8.5 over the domain, except for the Arabian Peninsula, particularly in the wetter lands around the Caspian and Mediterranean seas. Relative to global warming, SAI partially ameliorates the decreased mean TWS in the wet regions, while it has no significant effect on the increased TWS in drier lands. In the entire domain studied, the mean TWS is larger under SAI than pure GHG forcing, mainly due to the significant cooling and, in turn, a substantial decrease in evapotranspiration under SAI relative to SSP5-8.5. Changes in extreme water storage excursions under global warming are reduced by SAI. Extreme TWS under both future climate scenarios is larger than throughout the historical period across Iran, Iraq, and the Arabian Peninsula, but the response of the more continental eastern North Africa hyper-arid climate is different from the neighboring dry lands. In the latter case, we note a reduction in the mean TWS trend under both GHG and SAI scenarios, with extreme TWS values also showing a decline compared to historical conditions.
摘要中东和北非(MENA)是全球水资源最为紧张的地区,因此蓄水对该地区人民的生活影响深远。根据模拟,里海和地中海周围的陆地对未来气候变暖非常敏感。可用水量取决于温度和降水量等水文气候变量,而这些变量将取决于社会经济发展路径和气候变化。这项研究探讨了在未减缓温室气体(GHG)情景(SSP5-8.5)和平流层气溶胶干预(SAI)的情况下,平均陆地储水量(TWS)和极端陆地储水量(TWS)的变化,旨在抵消 GHG 引起的超过 1.5 ∘C 的升温,并将两者与历史时期的模拟结果进行比较。预计在 SSP5-8.5 条件下,除阿拉伯半岛外,全域的平均 TWS 和极端 TWS 都将显著下降,尤其是在里海和地中海周围较湿润的地区。相对于全球变暖,SAI 部分改善了潮湿地区平均 TWS 的下降,而对干旱地区 TWS 的增加没有显著影响。在整个研究区域,SAI 条件下的平均 TWS 要大于纯温室气体强迫,这主要是由于相对于 SSP5-8.5,SAI 会显著降温,进而导致蒸散量大幅下降。SAI减少了全球变暖下极端蓄水偏差的变化。在这两种未来气候情景下,伊朗、伊拉克和阿拉伯半岛的极端 TWS 都大于历史同期,但北非东部大陆性超干旱气候的反应与邻近旱地不同。就后者而言,我们注意到在温室气体和 SAI 两种情景下,平均 TWS 趋势都有所下降,与历史条件相比,极端 TWS 值也有所下降。
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引用次数: 0
Historical and projected future runoff over the Mekong River basin 湄公河流域历史径流量和未来预测径流量
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-29 DOI: 10.5194/esd-15-75-2024
Chao Wang, S. Leisz, Li Li, Xiaoying Shi, J. Mao, Y. Zheng, Anping Chen
Abstract. The Mekong River (MR) crosses the borders and connects six countries, including China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. It provides critical water resources and supports natural and agricultural ecosystems, socioeconomic development, and the livelihoods of the people living in this region. Understanding changes in the runoff of this important international river under projected climate change is critical for water resource management and climate change adaptation planning. However, research on long-term runoff dynamics for the MR and the underlying drivers of runoff variability remains scarce. Here, we analyse historical runoff variations from 1971 to 2020 based on runoff gauge data collected from eight hydrological stations along the MR. With these runoff data, we then evaluate the runoff simulation performance of five global hydrological models (GHMs) forced by four global climate models (GCMs) under the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). Furthermore, based on the best simulation combination, we quantify the impact of future climate change on river runoff changes in the MR. The result shows that the annual runoff in the MR has not changed significantly in the past 5 decades, while the establishment of dams and reservoirs in the basin visibly affected the annual runoff distribution. The ensemble-averaged result of the Water Global Assessment and Prognosis version 2 (WaterGAP2; i.e. GHM) forced by four GCMs has the best runoff simulation performance. Under Representative Concentration Pathways (RCPs; i.e. RCP2.6, RCP6.0 and RCP8.5), the runoff of the MR is projected to increase significantly (p<0.05); e.g. 3.81 ± 3.47 m3s-1a-1 (9 ± 8 % increase in 100 years) at the upper reach under RCP2.6 and 16.36 ± 12.44 m3s-1a-1 (13 ± 10 % increase in 100 years) at the lower reach under RCP6.0. In particular, under the RCP6.0 scenario, the increase in annual runoff is most pronounced in the middle and lower reaches, due to increased precipitation and snowmelt. Under the RCP8.5 scenario, the runoff distribution in different seasons varies obviously, increasing the risk of flooding in the wet season and drought in the dry season.
摘要湄公河(MR)跨越国界,连接中国、缅甸、老挝、泰国、柬埔寨和越南等六个国家。它提供了重要的水资源,支持着自然和农业生态系统、社会经济发展以及该地区居民的生计。了解这条重要国际河流在预计气候变化下的径流变化对于水资源管理和气候变化适应规划至关重要。然而,有关 MR 的长期径流动态以及径流变化的基本驱动因素的研究仍然很少。在此,我们根据从 MR 沿线八个水文站收集到的径流测量数据,分析了 1971 年至 2020 年的历史径流变化。根据这些径流数据,我们评估了在部门间影响模型相互比较项目(ISIMIP)下,由四个全球气候模型(GCMs)强迫的五个全球水文模型(GHMs)的径流模拟性能。此外,基于最佳模拟组合,我们量化了未来气候变化对 MR 河流径流变化的影响。结果表明,在过去的 50 年中,MR 的年径流量变化不大,而流域内大坝和水库的建立则明显影响了年径流量的分布。在四种全球气候模式的作用下,水全球评估和预测版本 2(WaterGAP2,即 GHM)的集合平均结果具有最佳的径流模拟性能。在代表性浓度途径(RCPs;即 RCP2.6、RCP6.0 和 RCP8.5)下,MR 的径流预计将显著增加(p<0.05);例如,在 RCP2.6 下,上游径流为 3.81 ± 3.47 m3s-1a-1(100 年内增加 9 ± 8%);在 RCP6.0 下,下游径流为 16.36 ± 12.44 m3s-1a-1(100 年内增加 13 ± 10%)。特别是在 RCP6.0 情景下,由于降水和融雪的增加,中下游的年径流量增加最为明显。在 RCP8.5 情景下,不同季节的径流分布明显不同,增加了雨季洪水和旱季干旱的风险。
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引用次数: 0
Extremely warm European summers preceded by sub-decadal North Atlantic ocean heat accumulation 欧洲夏季极度温暖之前,北大西洋海洋热量积累达十年以下
IF 7.3 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-09 DOI: 10.5194/esd-15-1-2024
Lara Wallberg, Laura Suarez‐Gutierrez, Daniela Matei, Wolfgang A. Müller
Abstract. The internal variability of European summer temperatures has been linked to various mechanisms on seasonal to sub- and multi-decadal timescales. We find that sub-decadal timescales dominate summer temperature variability over large parts of the continent and determine mechanisms controlling extremely warm summers on sub-decadal timescales. We show that the sub-decadal warm phases of bandpass-filtered European summer temperatures, hereinafter referred to as extremely warm European summers, are related to a strengthening of the North Atlantic Ocean subtropical gyre, an increase in meridional heat transport, and an accumulation of ocean heat content in the North Atlantic several years prior to the extreme summer. This ocean warming affects the ocean–atmosphere heat fluxes, leading to a weakening and northward displacement of the jet stream and increased probability of occurrence of high-pressure systems over Scandinavia. Thus, our findings link the occurrence of extremely warm European summers to the accumulation of heat in the North Atlantic Ocean and provide the potential to improve the predictability of extremely warm summers several years ahead, which is of great societal interest.
摘要欧洲夏季气温的内部变化与季节、亚年代和多年代时间尺度上的各种机制有关。我们发现,在欧洲大陆的大部分地区,亚年代时间尺度主导着夏季气温的变化,并确定了亚年代时间尺度上控制极暖夏季的机制。我们的研究表明,经过带通滤波的欧洲夏季气温的十年以下温暖阶段(以下简称欧洲极暖夏季)与北大西洋副热带涡旋的增强、经向热输送的增加以及极端夏季前几年北大西洋海洋热含量的积累有关。海洋变暖影响了海洋-大气热通量,导致喷流减弱并向北移动,增加了斯堪的纳维亚半岛上空出现高压系统的概率。因此,我们的研究结果将欧洲极暖夏季的发生与北大西洋的热量积累联系起来,为提高未来几年极暖夏季的可预测性提供了可能,这具有重大的社会意义。
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引用次数: 0
期刊
Earth System Dynamics
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