scholarly journals Contribution Analysis of the Spatial-Temporal Changes in Streamflow in a Typical Elevation Transitional Watershed of Southwest China over the Past Six Decades

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 495 ◽  
Author(s):  
Chengcheng Meng ◽  
Huilan Zhang ◽  
Yujie Wang ◽  
Yunqi Wang ◽  
Jian Li ◽  
...  
Keyword(s):  
Land Surface ◽  
Southwest China ◽  
Potential Evapotranspiration ◽  
Influencing Factor ◽  
Climate Impacts ◽  
Spatial And Temporal Scales ◽  
Attribution Analysis ◽  
Land Surface Parameter ◽  
The Impact

Attribution analyses on streamflow variation to changing climate and land surface characteristics are critical in studies of watershed hydrology. However, attribution results may differ greatly on different spatial and temporal scales, which has not been extensively studied previously. This study aims to investigate the spatial-temporal contributions of climate change and underlying surface variation to streamflow alteration using Budyko framework. Jiangling River Watershed (JRW), a typical landform transitional watershed in Southwest China, was chosen as the study area. The watershed was firstly divided into eight sub-basins by hydrologic stations, and hydrometeorological series (1954–2015) were divided into sub-intervals to discriminate spatial-temporal features. The results showed that long-term tendencies of hydrometeorological variables, i.e., precipitation (P), potential evapotranspiration (E0), and runoff depth (R), exhibited clear spatial patterns, which were highly related to topographic characteristics. Additionally, sensitivity analysis, which interpreted the effect of one driving factor by unit change, showed that climate factors P and E0, and catchment characteristics (land surface parameter n) played positive, negative, and negative roles in R, according to elastic coefficients (ε), respectively. The spatial distribution of ε illustrated a greater sensitivity and heterogeneity in the plateau and semi-humid regions (upstream). Moreover, the results from attribution analysis showed that the contribution of the land surface factor accounted for approximately 80% of the R change for the entire JRW, with an obvious spatial variation. Furthermore, tendencies of the contribution rates demonstrated regulations across different sub-regions: a decreasing trend of land surface impacts in trunk stream regions and increasing tendencies in tributary regions, and vice versa for climate impacts. Overall, both hydrometeorological variables and contributions of influencing factors presented regularities in long-term tendencies across different sub-regions. More particularly, the impact of the primary influencing factor on all sub-basins exhibited a decreasing trend over time. The evidence that climate and land surface change act on streamflow in a synergistic way, would complicate the attribution analysis and bring a new challenge to attribution analysis.

scholarly journals Development and application of the WRFPLUS-Chem online chemistry adjoint and WRFDA-Chem assimilation system

2015 ◽  
Vol 8 (6) ◽  
pp. 1857-1876 ◽  
Author(s):  
J. J. Guerrette ◽  
D. K. Henze
Keyword(s):  
Land Surface ◽  
Vertical Mixing ◽  
Model Performance ◽  
Land Surface Model ◽  
Sensitivity Study ◽  
Climate Impacts ◽  
Surface Model ◽  
Time Period ◽  
Develop Land ◽  
The Impact

Abstract. Here we present the online meteorology and chemistry adjoint and tangent linear model, WRFPLUS-Chem (Weather Research and Forecasting plus chemistry), which incorporates modules to treat boundary layer mixing, emission, aging, dry deposition, and advection of black carbon aerosol. We also develop land surface and surface layer adjoints to account for coupling between radiation and vertical mixing. Model performance is verified against finite difference derivative approximations. A second-order checkpointing scheme is created to reduce computational costs and enable simulations longer than 6 h. The adjoint is coupled to WRFDA-Chem, in order to conduct a sensitivity study of anthropogenic and biomass burning sources throughout California during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign. A cost-function weighting scheme was devised to reduce the impact of statistically insignificant residual errors in future inverse modeling studies. Results of the sensitivity study show that, for this domain and time period, anthropogenic emissions are overpredicted, while wildfire emission error signs vary spatially. We consider the diurnal variation in emission sensitivities to determine at what time sources should be scaled up or down. Also, adjoint sensitivities for two choices of land surface model (LSM) indicate that emission inversion results would be sensitive to forward model configuration. The tools described here are the first step in conducting four-dimensional variational data assimilation in a coupled meteorology–chemistry model, which will potentially provide new constraints on aerosol precursor emissions and their distributions. Such analyses will be invaluable to assessments of particulate matter health and climate impacts.

scholarly journals The SCALEX Campaign: Scale-Crossing Land Surface and Boundary Layer Processes in the TERENO-preAlpine Observatory

2017 ◽  
Vol 98 (6) ◽  
pp. 1217-1234 ◽  
Author(s):  
B. Wolf ◽  
C. Chwala ◽  
B. Fersch ◽  
J. Garvelmann ◽  
W. Junkermann ◽  
...  
Keyword(s):  
Land Surface ◽  
Three Dimensional ◽  
Observational Research ◽  
Spatial And Temporal Scales ◽  
Soil Variables ◽  
Boundary Layer Processes ◽  
Long Time ◽  
Modelling Studies ◽  
June July

Abstract ScaleX is a collaborative measurement campaign, collocated with a long-term environmental observatory of the German Terrestrial Environmental Observatories (TERENO) network in the mountainous terrain of the Bavarian Prealps, Germany. The aims of both TERENO and ScaleX include the measurement and modeling of land surface–atmosphere interactions of energy, water, and greenhouse gases. ScaleX is motivated by the recognition that long-term intensive observational research over years or decades must be based on well-proven, mostly automated measurement systems, concentrated in a small number of locations. In contrast, short-term intensive campaigns offer the opportunity to assess spatial distributions and gradients by concentrated instrument deployments, and by mobile sensors (ground and/or airborne) to obtain transects and three-dimensional patterns of atmospheric, surface, or soil variables and processes. Moreover, intensive campaigns are ideal proving grounds for innovative instruments, methods, and techniques to measure quantities that cannot (yet) be automated or deployed over long time periods. ScaleX is distinctive in its design, which combines the benefits of a long-term environmental-monitoring approach (TERENO) with the versatility and innovative power of a series of intensive campaigns, to bridge across a wide span of spatial and temporal scales. This contribution presents the concept and first data products of ScaleX-2015, which occurred in June–July 2015. The second installment of ScaleX took place in summer 2016 and periodic further ScaleX campaigns are planned throughout the lifetime of TERENO. This paper calls for collaboration in future ScaleX campaigns or to use our data in modelling studies. It is also an invitation to emulate the ScaleX concept at other long-term observatories.

scholarly journals Land–atmosphere interactions in the tropics

2019 ◽  
Author(s):  
Pierre Gentine ◽  
Adam Massmann ◽  
Benjamin R. Lintner ◽  
Sayed Hamed Alemohammad ◽  
Rong Fu ◽  
...  
Keyword(s):  
Land Surface ◽  
Deep Convection ◽  
Lower Troposphere ◽  
Surface Fluxes ◽  
Surface Radiation ◽  
Spatial And Temporal Scales ◽  
Wide Range ◽  
Shallow Clouds ◽  
The Tropics ◽  
The Impact

Abstract. The continental tropics play a leading role in the terrestrial water and carbon cycles. Land–atmosphere interactions are integral in the regulation of surface energy, water and carbon fluxes across multiple spatial and temporal scales over tropical continents. We review here some of the important characteristics of tropical continental climates and how land–atmosphere interactions regulate them. Along with a wide range of climates, the tropics manifest a diverse array of land–atmosphere interactions. Broadly speaking, in tropical rainforests, light and energy are typically more limiting than precipitation and water supply for photosynthesis and evapotranspiration; whereas in savanna and semi-arid regions water is the critical regulator of surface fluxes and land–atmosphere interactions. We discuss the impact of the land surface, how it affects shallow clouds and how these clouds can feedback to the surface by modulating surface radiation. Some results from recent research suggest that shallow clouds may be especially critical to land–atmosphere interactions as these regulate the energy budget and moisture transport to the lower troposphere, which in turn affects deep convection. On the other hand, the impact of land surface conditions on deep convection appear to occur over larger, non-local, scales and might be critically affected by transitional regions between the climatologically dry and wet tropics.

scholarly journals Stability of temperatures from TIMED/SABER v1.07 (2002–2009) and Aura/MLS v2.2 (2004–2009) compared with OH(6-2) temperatures observed at Davis Station, Antarctica

2010 ◽  
Vol 10 (9) ◽  
pp. 21547-21565 ◽  
Author(s):  
W. J. R. French ◽  
F. J. Mulligan
Keyword(s):  
Cold Bias ◽  
Spatial And Temporal Scales ◽  
Ground Station ◽  
Volume Emission ◽  
The Difference ◽  
Miss Distance ◽  
Hydroxyl Layer ◽  
The Impact ◽  
Long Term Studies

Abstract. Temperature profiles from two satellite instruments – TIMED/SABER and Aura/MLS – have been used to calculate hydroxyl-layer equivalent temperatures for comparison with values measured from OH(6-2) emission lines observed by a ground-based spectrometer located at Davis Station, Antarctica (68° S, 78° E). The profile selection criteria – <500 km from the ground station and solar zenith angles >97° – yielded a total of 2359 SABER profiles over 8 years (2002–2009) and 7407 MLS profiles over 5.5 years (2004–2009). The availability of simultaneous OH volume emission rate (VER) profiles from the SABER (OH-B channel) enabled an assessment of the impact of several different weighting functions in the calculation of OH-equivalent temperatures. The maximum difference between all derived hydroxyl layer equivalent temperatures was less than 3 K. Restricting the miss-distance and miss-time criteria showed little effect on the bias, suggesting that the OH layer is relatively uniform over the spatial and temporal scales considered. However, a significant trend was found in the bias between SABER and Davis OH of ~0.7 K/year over the 8-year period with SABER becoming warmer compared with the Davis OH temperatures. In contrast, Aura MLS exhibited a cold bias of 9.9 ± 0.4 K compared with Davis OH, but importantly, the bias remained constant over the 2004–2009 year period examined. The difference in bias behaviour of the two satellites has significant implications for multi-annual and long-term studies using their data.

Dynamic modelling framework to track sediment provenance and solve lakes in long-term landscape evolution models

2021 ◽  
Author(s):  
Boris Gailleton ◽  
Luca Malatesta ◽  
Jean Braun ◽  
Guillaume Cordonnier
Keyword(s):  
Landscape Evolution ◽  
Dynamic Modelling ◽  
Signal Propagation ◽  
Sediment Provenance ◽  
Topological Order ◽  
Time Step ◽  
Spatial And Temporal Scales ◽  
Modelling Framework ◽  
The Impact

&lt;p&gt;Many laws have been developed to describe the different aspects of landscape evolution at large spatial and temporal scales. Natural landscapes have heterogeneous properties (lithologies, climates, tectonics, etc.) that are associated with multiple coexisting processes. In turn, this can demand different mathematical expressions to model landscape evolution as a function of time and or space. Landscape Evolution Models are mostly designed to facilitate the combination of different landscape-wide laws in a plug-and-play way and many frameworks are being developed in this aim. However, most current frameworks cannot capture important landscape processes such as lake dynamics and full sediment tracing because they are optimized for speed and handle fluxes separately. Several processes require information from more than the immediate neighboring cells within a time step and demand an integrated knowledge from the entire upstream trajectory. Lakes for example require knowledge of all upstream water and sediment fluxes to be filled. These can only be known if all the laws controlling those have been processed. Tackling these situation with a grid logic requires substantial amount of numerical refactoring from existing models.&lt;/p&gt;&lt;p&gt;We present an alternative method to tackle landscape evolution modelling in heterogeneous landscapes with a framework inspired from Lagrangian and cellular automaton methods. Our framework only relies on the assumption that upstream nodes needs to be processed before the downstream ones, including lakes with outlets, in order to process all selected governing equations on a pixel-to-pixel basis. This way, we ensure that the true content of sediment and water fluxes can be known and tracked at any points. We first utilise graph theory to (i) find the most comprehensive path to reroute water through depressions and (ii) determine a generic multiple flow topological order (any node is processed after all potential upstream ones). Particles that register and track all fluxes simultaneously can then &quot;roll&quot; on the landscape and merge between each other while interacting with the grid.&lt;/p&gt;&lt;p&gt;This formulation makes possible a number of generic features. (i) The laws can be dynamically adapted to the environment (e.g. switching from single to multiple flow function of water content, adapting erodibility function of the sediment composition and quantity), (ii) Depressions can be explicitly managed, filled (or not) and separated from the rest of the landscape (e.g. sedimentation or evaporation in lakes) as a function function of inputted fluxes and parameters, (iii) full provenance, transport time, and deposition tracking as the particle can always keep in memory where the fluxes are from and in what proportions. In this contribution, we demonstrate the impact the importance of considering these additional elements in landscape evolution. In particular, lake dynamic can significantly impact the long-term signal propagation from source to sink.&lt;/p&gt;

A simple approach to mimic the effect of active vegetation in hydrological models to better estimate hydrological variables under climate change

2021 ◽  
Author(s):  
Thedini Asali Peiris ◽  
Petra Döll
Keyword(s):  
Climate Change ◽  
Land Surface ◽  
Climate Models ◽  
Potential Evapotranspiration ◽  
Global Climate ◽  
Global Climate Models ◽  
Hydrological Models ◽  
Net Radiation ◽  
Ensemble Mean ◽  
The Impact

&lt;p&gt;Unlike global climate models, hydrological models cannot simulate the feedbacks among atmospheric processes, vegetation, water, and energy exchange at the land surface. This severely limits their ability to quantify the impact of climate change and the concurrent increase of atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentrations on evapotranspiration and thus runoff. Hydrological models generally calculate actual evapotranspiration as a fraction of potential evapotranspiration (PET), which is computed as a function of temperature and net radiation and sometimes of humidity and wind speed. Almost no hydrological model takes into account that PET changes because the vegetation responds to changing CO&lt;sub&gt;2&lt;/sub&gt; and climate. This active vegetation response consists of three components. With higher CO&lt;sub&gt;2&lt;/sub&gt; concentrations, 1) plant stomata close, reducing transpiration (physiological effect) and 2) plants may grow better, with more leaves, increasing transpiration (structural effect), while 3) climatic changes lead to changes in plants growth and even biome shifts, changing evapotranspiration. Global climate models, which include dynamic vegetation models, simulate all these processes, albeit with a high uncertainty, and take into account the feedbacks to the atmosphere.&lt;/p&gt;&lt;p&gt;Milly and Dunne (2016) (MD) found that in the case of RCP8.5 the change of PET (computed using the Penman-Monteith equation) between 1981- 2000 and 2081-2100 is much higher than the change of non-water-stressed evapotranspiration (NWSET) computed by an ensemble of global climate models. This overestimation is partially due to the neglect of active vegetation response and partially due to the neglected feedbacks between the atmosphere and the land surface.&lt;/p&gt;&lt;p&gt;The objective of this paper is to present a simple approach for hydrological models that enables them to mimic the effect of active vegetation on potential evapotranspiration under climate change, thus improving computation of freshwater-related climate change hazards by hydrological models. MD proposed an alternative approach to estimate changes in PET for impact studies that is only a function of the changes in energy and not of temperature and achieves a good fit to the ensemble mean change of evapotranspiration computed by the ensemble of global climate models in months and grid cells without water stress. We developed an implementation of the MD idea for hydrological models using the Priestley-Taylor equation (PET-PT) to estimate PET as a function of net radiation and temperature. With PET-PT, an increasing temperature trend leads to strong increases in PET. Our proposed methodology (PET-MD) helps to remove this effect, retaining the impact of temperature on PET but not on long-term PET change.&lt;/p&gt;&lt;p&gt;We implemented the PET-MD approach in the global hydrological model WaterGAP2.2d. and computed daily time series of PET between 1981 and 2099 using bias-adjusted climate data of four global climate models for RCP 8.5. We evaluated, computed PET-PT and PET-MD at the grid cell level and globally, comparing also to the results of the Milly-Dunne study. The global analysis suggests that the application of PET-MD reduces the PET change until the end of this century from 3.341 mm/day according to PET-PT to 3.087 mm/day (ensemble mean over the four global climate models).&lt;/p&gt;&lt;p&gt;Milly, P.C.D., Dunne K.A. (2016). DOI:10.1038/nclimate3046.&lt;/p&gt;

scholarly journals Contribution of soil moisture feedback to hydroclimatic variability

2010 ◽  
Vol 14 (3) ◽  
pp. 505-520 ◽  
Author(s):  
N. Y. Krakauer ◽  
B. I. Cook ◽  
M. J. Puma
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Cloud Cover ◽  
Temperature Fluctuations ◽  
Substantial Impact ◽  
Empirical Measures ◽  
Spatial And Temporal Scales ◽  
Moisture Variation ◽  
The Impact ◽  
Soil Moisture Feedback

Abstract. While a variety of model experiments and analyses of observations have explored the impact of soil moisture variation on climate, it is not yet clear how large or detectable soil moisture feedback is across spatial and temporal scales. Here, we study the impact of dynamic versus climatological soil moisture in the GISS GCM ModelE (with prescribed sea-surface temperatures) on the variance and on the spatial and temporal correlation scale of hydrologically relevant climate variables (evaporation, precipitation, temperature, cloud cover) over the land surface. We also confirm that synoptic variations in soil moisture have a substantial impact on the mean climate state, because of the nonlinearity of the dependence of evapotranspiration on soil moisture. We find that including dynamic soil moisture increases the interannual variability of seasonal (summer and fall) and annual temperature, precipitation, and cloudiness. Dynamic soil moisture tends to decrease the correlation length scale of seasonal (warm-season) to annual land temperature fluctuations and increase that of precipitation. Dynamic soil moisture increases the persistence of temperature anomalies from spring to summer and from summer to fall, and makes the correlation between land precipitation and temperature fluctuations substantially more negative. Global observation sets that allow determination of the spacetime correlation of variables such as temperature, precipitation, and cloud cover could provide empirical measures of the strength of soil moisture feedback, given that the feedback strength varies widely among models.

scholarly journals Stability of temperatures from TIMED/SABER v1.07 (2002–2009) and Aura/MLS v2.2 (2004–2009) compared with OH(6-2) temperatures observed at Davis Station, Antarctica

2010 ◽  
Vol 10 (23) ◽  
pp. 11439-11446 ◽  
Author(s):  
W. J. R. French ◽  
F. J. Mulligan
Keyword(s):  
Cold Bias ◽  
Spatial And Temporal Scales ◽  
Ground Station ◽  
Volume Emission ◽  
The Difference ◽  
Miss Distance ◽  
Hydroxyl Layer ◽  
The Impact ◽  
Long Term Studies

Abstract. Temperature profiles from two satellite instruments – TIMED/SABER and Aura/MLS – have been used to calculate hydroxyl-layer equivalent temperatures for comparison with values measured from OH(6-2) emission lines observed by a ground-based spectrometer located at Davis Station, Antarctica (68° S, 78° E). The profile selection criteria – miss-distance <500 km from the ground station and solar zenith angles >97° – yielded a total of 2359 SABER profiles over 8 years (2002–2009) and 7407 MLS profiles over 5.5 years (2004–2009). The availability of simultaneous OH volume emission rate (VER) profiles from the SABER (OH-B channel) enabled an assessment of the impact of several different weighting functions in the calculation of OH-equivalent temperatures. The maximum difference between all derived hydroxyl layer equivalent temperatures was less than 3 K. Restricting the miss-distance and miss-time criteria showed little effect on the bias, suggesting that the OH layer is relatively uniform over the spatial and temporal scales considered. However, a significant trend was found in the bias between SABER and Davis OH of ~0.7 K/year over the 8-year period with SABER becoming warmer compared with the Davis OH temperatures. In contrast, Aura/MLS exhibited a cold bias of 9.9 ± 0.4 K compared with Davis OH, but importantly, the bias remained constant over the 2004–2009 year period examined. The difference in bias behaviour of the two satellites has significant implications for multi-annual and long-term studies using their data.

Modeling the impact of oceanic circulation and marine productivity on Cretaceous seafloor anoxia

2020 ◽  
Author(s):  
Yannick Donnadieu ◽  
Marie Laugie ◽  
Jean-Baptiste Ladant ◽  
François Raisson ◽  
Laurent Bopp
Keyword(s):  
Land Surface ◽  
Oceanic Circulation ◽  
Equatorial Pacific Ocean ◽  
Oxygen Minimum Zones ◽  
Tethys Sea ◽  
Marine Biogeochemistry ◽  
Anoxic Events ◽  
Marine Productivity ◽  
The Impact

&lt;p&gt;Oceanic anoxic events (OAEs) are abrupt events of widespread deposition of organic-rich sediments and extensive seafloor anoxia. Mechanisms usually invoked as drivers of oceanic anoxia are various and still debated today. They include a rise of the CO2 atmospheric level due to increased volcanic activity, a control by the paleogeography, changes in oceanic circulation or enhanced marine productivity. In order to assess the role of these mechanisms, we use an IPCC-class model, the IPSL-CM5A2 Earth System Model, which couples the atmosphere, land surface, and ocean components, this last one including sea ice, physical oceanography and marine biogeochemistry which allows to simulate oceanic oxygen.&lt;/p&gt;&lt;p&gt;We focus here on OAE2, which occurs during the Cretaceous at the Cenomanian-Turonian boundary (93.5 Ma), and is identified as a global event with evidence for seafloor anoxia in the Atlantic and Indian Oceans, the Southwest Tethys Sea and the Equatorial Pacific Ocean. Using a set of simulations from 115 to 70 Ma, we analyze the long-term paleogeographic control on oceanic circulation and consequences on oceanic oxygen concentration and anoxia spreading. Short-term controls such as an increase of pCO&lt;sub&gt;2&lt;/sub&gt;, nutrients, or orbital configurations are also studied with a second set of simulations with a Cenomano-Turonian (90 Ma) paleogeographic configuration. The different simulated maps of oxygen are used to study the evolution of marine productivity and oxygen minimum zones as well as the spreading of seafloor anoxia, in order to unravel the interlocking of the different mechanisms and their specific impact on anoxia through space and time.&lt;/p&gt;

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