Climatic Boundary Research Articles

Latest Pleistocene and Holocene Floodplain Evolution in Central Europe—Insights from the Upper Unstrut Catchment (NW-Thuringia/Germany)

The upper Unstrut River is located in Germany at the modern Central European climate boundary of Cfb and Dfb climate. The river drains a loess landscape, which has experienced important environmental changes throughout the last 12,000 years. To evaluate the impacts of these changes on floodplain evolution, a multi-proxy research program, consisting of 2D electrical resistivity tomography profiling (ERT), vibracoring, and sedimentological investigations, 14C and OSL dating were applied. From base to top the investigations the following fluvial deposits were revealed: (1) gravels embedded in a fine-grained sediment matrix (interpreted as fluvial bedload deposits); (2) silty sediment with pedogenic features (interpreted as overbank floodplain deposits); (3) peat and tufa deposits (interpreted as wetland deposits) intercalated by pedogenetically influenced silty sediments (interpreted as overbank deposits); (4) humic silty sediment with some pedogenic features (interpreted as overbank floodplain deposits); and (5) silty sediments (interpreted as overbank deposits). Radiocarbon and luminescence dates yielded the following periods for sediment formation: (1) Younger Dryas to Preboreal period (around 11.6 cal ka BP); (2) Preboreal to early Atlantic period (approx. 11.6 to 7.0 cal ka BP); (3) early Atlantic to late Subboreal period (approx. 7.3 to 3.4 cal ka BP); (4) late Subboreal to early Subatlantic period (2.9 to 2.3 cal ka BP); and (5) late Subatlantic period (approx. 1.0 to 0.6 cal ka BP). The results suggest that floodplain development during the latest Pleistocene and early Holocene (approx. 11.6 to 7.0 cal ka BP) was considerably controlled by climatic conditions and short-term climate variabilities, which caused gravel deposition and overbank sedimentation. Afterwards floodplain conditions varied between rather stable (peat and tufa development, initial soil formation) and active periods (deposition of overbank fines). In this context, active periods with increased sediment input prevailed from approx. 5.1 to 3.4 cal ka BP, 2.9 to 2.3 cal ka, and 1.0 to 0.6 cal ka BP, temporally corresponding well with increased land-use phases of the past. In conclusion this study demonstrates that the investigated Unstrut catchment has reacted very sensitively to natural and human-induced changes during the latest Pleistocene and Holocene. Consequently, this high vulnerability to external changes should be considered in future river predictions or river management.

Future population transgress climatic risk boundaries of extreme temperature and precipitation

Anthropogenic climate change is influencing the frequencies of extreme weather events. Considering the adaptability to extreme climatic risks in the future, we focused on determining whether humans have been exposed to the risks before. We define the rim of two-dimensional histograms of population under 20-year extreme temperature and precipitation as a climatic risk boundary. More than 30% (16.3%) of world population in South Asia, sub-Saharan Africa, and other regions will transgress the climatic risk boundary by the end of this century under RCP8.5 (RCP2.6) scenario. While many areas with large cities will remain within the global climatic risk boundary, they will transgress their regional climatic risk boundaries. This study shows that it is also necessary to consider the limits to adaptation for each appropriate area, considering the cultural, technological, and social transferability of adaptation. This study will help refine public perceptions of extreme climatic risks and lead to more efficient policy making.

Verification on the mode of moisture transfer in the vadose zone of thick loess

AbstractPrecipitation is the only source of groundwater recharge in the Chinese loess region. However, rainfall has been the main driver of geological disasters and engineering challenges in China, such as landslides, slope collapse and sinking of foundations. The roles of preferential flow and piston flow in moisture transfer in the thick loess vadose zone remain controversial. This study used a 100‐m thick loess shaft to monitor soil moisture content and soil temperature over 5 years, whereas climate indices were monitored on the Earth surface. The soil water characteristic curves and hydraulic conductivity function of the loess and the palaeosol collected in the profile were measured in a laboratory. The soil profile moisture transfer process was simulated based on the climatic boundary conditions and measured hydraulic parameters. The monitored and simulated results suggest that loess moisture transfer is dominated by piston flow. The thick loess vadose zone above the groundwater level could be divided into two sub‐zones, namely the active and steady zones. The active zone has a thickness of ~7 m and shows a direct response to climate change, with soil moisture content regulated by rainfall infiltration, evaporation and transpiration and soil moisture moving as transient flow. Although preferential flow can move in the active zone along joints, fissures and holes when water accumulates in the lower ground during heavy rainfall, piston flow remains the main mode of water movement. The steady zone has a thickness of <7 m and is above the groundwater level. Soil moisture content and soil temperature in the steady zone show temporal stability and soil moisture moves as a steady flow. Piston flow is the only mode of water movement in the steady zone. Since percolation velocity in the steady zone is estimated to be 73.3 mm/year, 1330 years of rainfall infiltration through the 97.5 m thick vadose zone would be required to recharge groundwater.

Forecasting future climate boundary maps (2021–2060) using exponential smoothing method and GIS

Future-oriented forecasts have an important place in making forward-looking decisions and planning. At the beginning of these studies is the monitoring and detection of climate change. The climate is very variable. Therefore, by making predictions about the climate, preliminary information about how and to what extent the climate will change can be obtained, and accordingly, necessary precautions can be taken quickly. This study aims to produce predictive climate boundary maps using Geographic Information Systems (GIS), in which climate classification methods and time series methods are evaluated to monitor and determine the changes caused by the climate in 13 selected provinces in Turkey. The triple exponential smoothing method and the Erinc climate classification method were discussed. The data were obtained from the General Directorate of Meteorology (GDM) between 1930 and 2020, and each year's precipitation efficiency index (Im) of the Erinc climate classification method was calculated. It is divided into two classes for forecasting and testing current indices: test Im indices (1930–2014) and forecast test Im indices (2015–2020). MAD, MSE, and MAPE criteria were calculated to determine whether the Im estimates were meaningful. However, the accuracy of the estimates was ensured by considering the MAPE criteria for this study. After this stage, the analyses were performed again with test Im indices (1930–2020) and forecast Im indices (2021–2060), and Im indices predictions for the future were made. Finally, the obtained forecast indices were subjected to GIS interpolation analyses (Kriging and IDW), and future climate boundary maps were produced. Thanks to the outputs obtained from the study, how the climate classes of any region will be in the future and to what extent they will change will be provided by evaluating the climate classification and time series methods together. It will contribute to different studies in this field with its innovative analysis approach.

LORA Based Wireless Weather Station

Abstract: In this Project we foster a model of "LoRa Based Wireless Weather Station". Where LoRa is a remote organization innovation supporting the web of things (IoT) framework. This innovation is an elective to other remote organization modules that have proactively been notable like GSM modules, Wi-Fi Modules and Bluetooth Modules. The use of the LoRa network expands the scope of remote cells that can arrive at distances of as much as 8 kilometres while as yet having low power usage. Climate boundaries that we are estimated in this task are Temperature, Pressure, Dew point, Altitude, Rainfall, Humidity and Light Intensity. In this model we use Arduino UNO, Barometric Sensor, Rain Sensor, Light Intensity Sensor and LoRa modules. What's more, Thingspeak Web application for sharing information to the clients. This framework can possibly be executed in metropolitan and provincial zones with various kinds of sensors related to it. This undertaking can be directed to shape a Low Power-Wide Area Network as a greater sensor organization.

Assessing the conservation of eastern Ecuadorian cloud forests in climate change scenarios

The Tropical Montane Cloud Forests (TMCF) of South America are ecosystems facing rapid changes due to global warming. Herein, we used species climatic niche models to reconstruct the climatic boundaries of TMCF and to predict range shifts in climate change scenarios. Thirty-two species from three taxonomic groups (plants, birds, and amphibians) were modelled using community-level niche models under current and future climatic scenarios, as determined by two Global Climate Models (GCMs) for the year 2050. The community-level reconstructions were used to detect the overlap of TMCF with surrounding ecosystems and with current protected areas (PA). Approximate 42–54% area reduction and 207–429 m upward elevational shift was predicted under climate scenarios. Accordingly, severe environmental contractions (loss of suitability area) due to climate change were detected by our models. TMCF area within PA may increase 17–38% by 2050. We identified transition zones rather than clear limits of vegetational boundaries of TMCF with adjacent ecosystems, which suggested that both TMCF and transitional zones will be impacted, to what conservation strategies targeting TMCF and adjacent ecosystems should be prioritized.

The July 2019 European Heat Wave in a Warmer Climate: Storyline Scenarios with a Coupled Model Using Spectral Nudging

Abstract Extreme weather events are triggered by atmospheric circulation patterns and shaped by slower components, including soil moisture and sea surface temperature, and by the background climate. This separation of factors is exploited by the storyline approach in which an atmospheric model is nudged toward the observed dynamics using different climate boundary conditions to explore their influence. The storyline approach disregards uncertain climatic changes in the frequency and intensity of dynamical conditions, focusing instead on the thermodynamic influence of climate on extreme events. Here we demonstrate an advanced storyline approach that employs a coupled climate model (AWI-CM-1-1-MR) in which the large-scale free-troposphere dynamics are nudged toward ERA5 data. Five-member ensembles are run for present-day (2017–19), preindustrial, +2-K, and +4-K climates branching off from CMIP6 historical and scenario simulations of the same model. In contrast to previous studies, which employed atmosphere-only models, feedbacks between extreme events and the ocean and sea ice state, and the dependence of such feedbacks on the climate, are consistently simulated. Our setup is capable of reproducing observed anomalies of relevant unconstrained parameters, including near-surface temperature, cloud cover, soil moisture, sea surface temperature, and sea ice concentration. Focusing on the July 2019 European heat wave, we find that the strongest warming amplification expands from southern to central Europe over the course of the twenty-first century. The warming reaches up to 10 K in the 4-K-warmer climate, suggesting that an analogous event would entail peak temperatures around 50°C in central Europe. Significance Statement This work explores a new storyline method to determine the impact of climate change on specific recent extreme events. The observed evolution of the large-scale atmospheric circulation is imposed in a coupled climate model. Variations in climate parameters, including ocean temperatures and sea ice, are well reproduced. By varying the background climate, including CO2 concentrations, it is demonstrated how the July 2019 European heat wave could have evolved in preindustrial times and in warmer climates. For example, up to 10°C warmer peak temperatures could occur in central Europe in a 4°C warmer climate. The method should be explored for other types of extreme events and has the potential to make climate change more tangible and to inform adaptation measures.

Links Between Faulting, Topography, and Sediment Production During Continental Rifting: Insights From Coupled Surface Process, Thermomechanical Modeling

AbstractContinental rifts form by extension, and their subsequent evolution depends on the tectonic and climatic boundary conditions. We investigate how faulting, topography, and the evolution of the sediment flux during rifting are affected by these boundary conditions, in particular whether it is possible to correlate tectonic activity, topography, and sediment flux on long timescales (40 Myr). We use a thermomechanical model coupled with a landscape evolution model and present a series of 14 models, testing the sensitivity of the models to crustal strength, extension rate, and fluvial erodibility. The degree of strain localization drives the structural evolution of the modeled rifts: slow extension, high crustal strength, and efficient surface processes promote a high degree of strain localization, resulting in fewer active faults with larger offset. Overall, the magnitude of sediment production correlates with the degree of strain localization. In case of unchanged erosional power and similar amount of extension, systems with slower extension produce more sediment owing to a stronger positive feedback between erosion and fault offset. We observe a characteristic sequence of events, reflecting the morpho‐tectonic evolution of rifts: the highest rock uplift rates are observed before the maximum elevation, and the highest sediment flux postdates the peak in elevation. Our results indicate that for natural systems, the evolution of the sediment flux is a good proxy for the evolution of topography, and that a time lag of 2–5 Myr between the peaks in main tectonic activity and sediment flux can exist.

Neodymium isotopes as a paleo-water mass tracer: A model-data reassessment

Proxy reconstructions from deep ocean sediments have helped to shape our understanding of the role of the global overturning circulation in past climate change. Neodymium (Nd) isotopes have contributed to this knowledge, as a tracer of past bottom water provenance and mixing. Here, we extend the implementation of Nd isotopes in the physical-biogeochemical Bern3D model by revising a number of critical parameterizations, which result in an improved description of the marine Nd cycle. We exploit the dynamically consistent framework of the model, which allows us to assess the processes driving non-conservative Nd isotope behavior with a particular focus on the Last Glacial Maximum (LGM) and its substantially different climatic, oceanic, and biogeochemical boundary conditions. We show that the more radiogenic Nd isotopic compositions found throughout the glacial ocean can be explained by changes in the weathering input fluxes and do not require large reorganizations of the deep circulation. Our findings further highlight that the Nd isotopic composition of a water mass can not only be significantly affected by a benthic Nd flux, but also be modified by the vertical downward transport of Nd via reversible scavenging. While these non-conservative processes only have a limited impact in the modern ocean, they were substantially more pronounced during the LGM and mostly independent of the circulation state, with their contributions being non-linear, partially opposing, and spatially variable. During the transiently simulated deglaciation Nd isotope variations induced by major circulation weakenings and resumptions are found to be most pronounced in the South Atlantic, while they are increasingly muted towards the north. Hence, it emerges that the interpretation of authigenic Nd isotope records requires more spatially specific considerations of non-conservative processes in order to more reliably infer basin-scale ocean circulation and water mass mixing of the past.

Regional differences in influence of intermediate cover permeability on perched leachate in landfill

Intermediate cover may act as impervious layers in landfill and form perched leachates, which have adverse effects on the safe operation of landfill. The formation rules of perched leachate mound in different climate regions are not the same and still unclear. To solve this problem, a finite difference method that took account of climate boundaries was conducted. Four typical cities' climate data standing for Chinese climate and 4 permeability parameters of intermediate cover were used in the simulation. The results showed that key to the formation of perched leachate is that the infiltration rate of the leachate is greater than the ks of the intermediate cover. Under arid climate conditions, the infiltrates of the leachate are generally lower than the infiltration capacity of the intermediate cover, and it is not easy to form a perched leachate mound. In humid regions, when the ks of the intermediate cover is lower than 10−5 cm/s, perched leachate forms easily in rainy seasons. The result can be useful to determine the permeability parameters of intermediate cover, especially in humid climate.

Desert Climate Regionalization for Joshua Tree National Park and Surrounding Areas Using New Climate Network Observations

Abstract A new amalgamation of weather stations in and around Joshua Tree National Park in southeastern California has allowed for objective climate analysis regionalization at a much finer scale than past studies. First, it sets a baseline for many regions within the park’s boundaries that were not subject to direct observations. Second, these new observations are key to understanding shifting microclimate regimes in a desert ecosystem prone to the effects of climate change. Principal component analysis was used to regionalize the climate network based on monthly temperature and precipitation climate observations and standardized anomalies. Both the observation values and standardized climate anomalies identified regional boundaries. In general, these boundaries align with traditional ideas and past studies of the Mojave and Sonoran Deserts based on elevation (specifically the 1000-m contour) for the National Park Service. Standardized anomaly values identified a boundary based on seasonal precipitation, whereas observation values identified a boundary based on elevation. The boundary line within the park is similar for both data approaches, with the boundary running along the higher western one-third of the park. Conversely, the two methods differ significantly in the Coachella Valley, where low elevations and low precipitation meet winter-dominated seasonal precipitation. This study highlights the importance and opportunity of field observations to create climatological and ecological regionalization, and it also constructs a baseline to monitor and manage shifting desert regions in the future. Significance Statement This study identifies a high-resolution climate boundary zone in Joshua Tree National Park between the Sonoran and Mojave Deserts. The new transition zone presents the seasonal and elevational temperature and precipitation components of the two deserts, connecting with the unique ecology of the deserts. This finding highlights just one study opportunity of new field observation networks in arid or topographically diverse regions. It also provides a baseline for climate change as a resource for environmental management groups to better understand and preserve our natural spaces.

Can’t see the wood for the trees? Canopy physiognomy influences the distribution of peninsular Indian flying lizards

AbstractAimIn the absence of topographic barriers to dispersal, spatial boundaries of species are largely governed by the environmental regimes they occupy. Flying lizards (Agamidae: Draco) from peninsular India have surmounted prominent geographic barriers, but their northern distribution abruptly ends at the ‘Goa gap’, a latitudinal boundary separating the wet and dry regions of the Western Ghats. Given their exclusively arboreal habits, we posit that canopy physiognomy determines Draco distribution in regions of climatic suitability.LocationPeninsular India.TaxaDraco dussumieri, Monilesaurus rouxii.MethodsWe analysed occurrence data collated from multiple sources against a suite of climatic and canopy‐specific predictors to model the occurrence of Draco. We used an information theoretic approach to binary logistic regression that incorporates presence/absence data, along with a maximum entropy‐based algorithm that models ecological niches in space using presence‐only data. Climatic data were obtained from CHELSA and WorldClim. We compared models for Draco dussumieri with the only other largely sympatric, arboreal agamid, Monilesaurus rouxii, which spans the Goa gap. Finally, we statistically tested how regions Draco inhabits differ in canopy physiognomy from the regions in the Western Ghats where it does not occur.ResultsCanopy height was the most influential predictor of Draco presence in regions of climatic suitability under both the logistic regression and maximum entropy models. While climatically suitable regions occur north of the Goa gap, these regions harbour significantly lower canopies with lesser coverage. Despite a narrower range of climatic suitability, Monilesaurus has spanned the Goa gap, presumably because it is less dependent on canopy traits.Main conclusionsLower canopies with lesser coverage act as a biogeographic barrier for the dispersal of Draco into regions of climatic suitability. In addition to being a climatic boundary, the Goa gap serves as a vegetational barrier that demarcates regions with significantly dissimilar canopy physiognomies. Our study highlights the importance of quantifying environmental regimes that organisms occupy to better understand distribution patterns. Our results implicitly predict the effects of deforestation on Draco distribution in the peninsula and therefore, influence its conservation strategy.

Spatio-Temporal Characteristics of Dry-Wet Conditions and Boundaries in Five Provinces of Northwest China from 1960 to 2020

The study of dry-wet climate boundaries in the context of climate warming is of great practical significance for improving the environment of ecologically fragile zones and promoting economic and natural sustainable development. In this study, based on the daily meteorological data of 110 stations, using the wetness index, empirical orthogonal function decomposition, regime shift detection test, Fourier power spectrum, and Kriging interpolation, the researchers analyzed the spatiotemporal characteristics of dry-wet conditions and boundaries in five provinces of Northwest China from 1960 to 2020. The results showed that the overall wetness index increased in the past 61 years, but with significant internal differences, among which the western and central climate tended to be warm and wet, and the eastern tended to be warm and dry. The annual wetness index changed abruptly in 1986 with cycles of 3.61 a, 7.11 a and 8.83 a. The mutations occurred correspondingly in spring, summer, autumn, and winter in 1972, 1976, 1983, and 1988, with periods of 3.88 a and 4.92 a, 2.18 a and 2.81 a, 2.15 a, and 2.10 a, respectively. The dry-wet climate boundary has fluctuated markedly since 1960. The extreme arid and arid regions boundary shifted southward and shrank in size until the extreme arid region disappeared in the 2010s. The arid along with semi-arid regions and semi-arid in addition to semi-humid regions boundaries both have two boundary lines, and show the shift of the northwestern boundary to the southeast and the southeastern boundary to the northwest, with the area of the arid together with semi-arid regions shrinking significantly by 5.64%, simultaneously, the area of the semi-humid region area expanding significantly by 84.11%. The boundary of semi-humid and relatively humid regions, and the boundary of relatively humid and humid regions all shifted to the southeast, moreover, the area of the relatively humid region and humid region shrank significantly by 12.08%. The expansion of semi-humid region and the contraction of other climate regions are characteristics of the dry-wet climate variability in five provinces of Northwest China. The area of the three arid climate zones dwindled by 9.61%, and the area of the three humid zones extended by 39.01%. Obviously, the climate inclined to be warm and humid in general.

Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model

Abstract. Since the middle Miocene (15 Ma, million years ago), the Earth's climate has undergone a long-term cooling trend, characterised by a reduction in ocean temperatures of up to 7–8 ∘C. The causes of this cooling are primarily thought to be due to tectonic plate movements driving changes in large-scale ocean circulation patterns, and hence heat redistribution, in conjunction with a drop in atmospheric greenhouse gas forcing (and attendant ice-sheet growth and feedback). In this study, we assess the potential to constrain the evolving patterns of global ocean circulation and cooling over the last 15 Ma by assimilating a variety of marine sediment proxy data in an Earth system model. We do this by first compiling surface and benthic ocean temperature and benthic carbon-13 (δ13C) data in a series of seven time slices spaced at approximately 2.5 Myr intervals. We then pair this with a corresponding series of tectonic and climate boundary condition reconstructions in the cGENIE (“muffin” release) Earth system model, including alternative possibilities for an open vs. closed Central American Seaway (CAS) from 10 Ma onwards. In the cGENIE model, we explore uncertainty in greenhouse gas forcing and the magnitude of North Pacific to North Atlantic salinity flux adjustment required in the model to create an Atlantic Meridional Overturning Circulation (AMOC) of a specific strength, via a series of 12 (one for each tectonic reconstruction) 2D parameter ensembles. Each ensemble member is then tested against the observed global temperature and benthic δ13C patterns. We identify that a relatively high CO2 equivalent forcing of 1120 ppm is required at 15 Ma in cGENIE to reproduce proxy temperature estimates in the model, noting that this CO2 forcing is dependent on the cGENIE model's climate sensitivity and that it incorporates the effects of all greenhouse gases. We find that reproducing the observed long-term cooling trend requires a progressively declining greenhouse gas forcing in the model. In parallel to this, the strength of the AMOC increases with time despite a reduction in the salinity of the surface North Atlantic over the cooling period, attributable to falling intensity of the hydrological cycle and to lowering polar temperatures, both caused by CO2-driven global cooling. We also find that a closed CAS from 10 Ma to present shows better agreement between benthic δ13C patterns and our particular series of model configurations and data. A final outcome of our analysis is a pronounced ca. 1.5 ‰ decline occurring in atmospheric (and ca. 1 ‰ ocean surface) δ13C that could be used to inform future δ13C-based proxy reconstructions.

Commensal microbiota and host metabolic divergence are associated with the adaptation of Diploderma vela to spatially heterogeneous environments.

Heterogeneous environment adaptation is critical to understand the species evolution and response to climate change. However, how narrow-range species adapt to micro-geographic heterogeneity has been overlooked, and there is a lack of insights from metabolism and commensal microbiota. Here, we studied the environmental adaptation for 3 geographic populations (>40 km apart) of Diploderma vela, a lizard endemic to dry-hot valleys of the Hengduan Mountain Region. The climatic boundary caused a cooler, droughtier, and barren environment for northernmost population (RM) than the middle (QZK) and southernmost populations (FS). Correspondingly, significant divergences in liver and muscle metabolism and commensal microbiota were detected between RM and QZK or FS individuals, but not between QZK and FS individuals. Phospholipid composition, coenzyme level (i.e. pyridoxal and NAD+ ), and cholesterol metabolism (e.g. androgen and estriol synthesis) constituted the major metabolic difference between RM and QZK/FS groups. FS and QZK individuals kept abundant Proteobacteria and antifungal strains, while RM individuals maintained more Firmicutes and Bacteroidota. Strong associations existed between varied host metabolite and gut microbes. How were these interpopulation variations associated to the environment adaptation were discussed. These results provided some novel insights into the environmental adaptation and implicated the consequence of climate change on narrow-range species.

Hygrothermal analysis of a wall isolated from the inside: the potential of dynamic hygrothermal simulation

Hygrothermal simulations are expected to provide powerful support to the design process in the context of energy retrofit of historic buildings and prevent the moisture-related damages. They can be used to predict the hygrothermal behaviour of the building in detail and exclude the occurrence of moisture related damages, such as mould formation or material degradation. However, these simulations require various input data related to materials and boundary conditions, which are often difficult to find during the design phase. In this article we analyse the potential of hygrothermal simulations in predicting the hygrothermal behaviour of an internally insulated wall, even with limited information on the hygrothermal properties of the materials composing the historical wall. The quality of the simulation’s results is evaluated through a comparison with monitored data. The numerical model is calibrated to maximise the agreement with the monitored data. The considered case study is a historical building located nearby Bolzano (Northern Italy). The monitoring system is installed with the aim of analysing temperature and relative humidity profiles within the construction. In addition, the climatic boundary conditions are measured both inside and outside the building, including temperature, relative humidity, driving rain and solar radiation. The numerical simulation of the wall under analysis is performed with the software DELPHIN.

The inherent uncertainty of precipitation variability, trends, and extremes due to internal variability, with implications for Western US water resources

AbstractThe approximately century-long instrumental record of precipitation over land reflects a single sampling of internal variability. Thus, the spatiotemporal evolution of the observations is only one realization of `what could have occurred' given the same climate system and boundary conditions, but different initial conditions. While climate models can be used to produce initial-condition large ensembles that explicitly sample different sequences of internal variability, an analogous approach is not possible for the real world. Here, we explore the use of a statistical model for monthly precipitation to generate synthetic ensembles based on a single record. When tested within the context of the NCAR Community Earth System Model version 1 Large Ensemble (CESM1-LE), we find that the synthetic ensemble can closely reproduce the spatiotemporal statistics of variability and trends in winter precipitation over the extended contiguous United States, and that it is difficult to infer the climate change signal in a single record given the magnitude of the variability. We additionally create a synthetic ensemble based on the Global Precipitation Climatology Centre (GPCC) dataset, termed the GPCC-synth-LE; comparison of the GPCC-synth-LE with the CESM1-based ensembles reveals differences in the spatial structures and magnitudes of variability, highlighting the advantages of an observationally-based ensemble. We finally use the GPCC-synth-LE to analyze three water resource metrics in the Upper Colorado River Basin: frequency of dry, wet, and whiplash years. Thirty-one year ‘climatologies’ in the GPCC-synth-LE can differ by over 20% in these key water resource metrics due to sampling of internal variability, and individual ensemble members in the GPCC-synth-LE can exhibit large near-monotonic trends over the course of the last century due to sampling of variability alone.

A Combined Rock Magnetic and Meteorological Investigation of the Precipitation Boundary Across the Tibetan Plateau

AbstractCharacterizing the spatial distribution of precipitation across the Tibetan Plateau (TP) is important for understanding how the topography and atmospheric circulation influence the climatic patterns of the region. We collected 143 surface soil samples from the central and southeastern TP (SETP) for rock magnetic characterization of the spatial distribution of the pedogenic intensity. Comparison with meteorological data shows that pedogenic intensity decreases significantly along the pathway of moist air across the SETP toward the interior, and that there is a positive correlation between pedogenic magnetite/maghemite content and mean annual precipitation. By contrast, the samples from the central TP show a low degree of pedogenic alteration, consistent with the limited precipitation within this area. The results indicate the possibility of using magnetic properties of surface soils to determine the precipitation distribution in areas lacking meteorological stations. These observations, combined with published soil magnetic results, help to define the climatic boundary in the TP.

Characteristics and relationships between daily maximum boundary layer height and precipitation in the arid and semi‐arid regions of East Asia

The spatial distribution of mean daily maximum boundary layer height (BLH) from 1900 to 2010, and three climatic subzone boundaries. (The white line represents the annual average precipitation contour and the fill colour represents the average BLH).

Transient hillslope erosion in slow evolution landscapes

SummaryTransient evolution and adjustment to changing tectonic and climatic boundary conditions is an essential attribute of landscapes, and characterizing transient behavior is a key to understanding their dynamics and history. Developing new approaches to detect such transience has been explored by various methods, in particular to identify landscape response to Late Cenozoic and Quaternary climatic changes. Such studies have often focused on regions of high relief and/or active tectonic activity where interferences between tectonic and climatic signals might complicate the interpretation of the observations. We investigated the case of the hillslopes of the Serra do Cipó quartzitic range in SE Brazil in order to detect and quantify transience in a tectonically quiescent landscape over 100‐ka timescales. We determined hilltop curvature from a high‐resolution digital surface model derived from Pléiades imagery and measured cosmogenic nuclide (10Be and 26Al) concentrations at these hilltop sites. We compare both observations with predictions of hillslope diffusion theory, observing a distinctive signature of an acceleration of denudation. We performed a joint inversion of topographic and isotopic data to retrieve an evolution of the hillslope sediment transport coefficient through time. The timing of the increase in denudation cannot be unequivocally associated with a single climatic event but is consistent with important, climatically modulated fluctuations in precipitation and erosion in this area during the Middle and Late Pleistocene.