scholarly journals Robust historical evapotranspiration trends across climate regimes

2020 ◽  
Author(s):  
Sanaa Hobeichi ◽  
Gab Abramowitz ◽  
Jason Evans
Keyword(s):  
Land Surface ◽  
Climate Extremes ◽  
Historical Period ◽  
Hybrid Techniques ◽  
Time Period ◽  
Optimal Linear Combination ◽  
Uncertainty Estimates ◽  
Out Of Sample ◽  
Physically Based ◽  
Optimal Linear

Abstract. Evapotranspiration (ET) links the hydrological, energy, and carbon cycle on the land surface. Quantifying ET and its spatiotemporal changes is also key to understanding climate extremes such as droughts, heatwaves and flooding. Regional ET estimates require reliable observationally-based gridded ET datasets, and while many have been developed using physically-based, empirically-based and hybrid techniques, their efficacy, and particularly the efficacy of their uncertainty estimates, is difficult to verify. In this work, we extend the methodology used in Hobeichi et al. (2018) to derive a new version of the Derived Optimal Linear Combination Evapotranspiration (DOLCE) product, with observationally constrained spatiotemporally varying uncertainty estimates, higher spatial resolution, more constituent products and extended temporal reach (1980–2018). After successful evaluation of the efficacy of these uncertainty estimates out-of-sample, we derive novel ET climatology clusters for the land surface, based on the magnitude and variability of ET at each location. The verified uncertainty estimates and extended time period then allow us to examine the robustness of historical trends spatially and in each of these six ET climatology clusters. We find that despite robust decreasing ET trends in some regions, these do not correlate with behavioural ET clusters. Each cluster, and the vast majority of the Earth's surface, show clear robust increases in ET over the recent historical period.

scholarly journals Robust historical evapotranspiration trends across climate regimes

2021 ◽  
Vol 25 (7) ◽  
pp. 3855-3874
Author(s):  
Sanaa Hobeichi ◽  
Gab Abramowitz ◽  
Jason P. Evans
Keyword(s):  
Land Surface ◽  
Climate Extremes ◽  
Historical Period ◽  
Carbon Cycles ◽  
Hybrid Techniques ◽  
Uncertainty Estimates ◽  
Out Of Sample ◽  
Physically Based ◽  
Optimal Linear ◽  
Spatio Temporal

Abstract. Evapotranspiration (ET) links the hydrological, energy and carbon cycles on the land surface. Quantifying ET and its spatio-temporal changes is also key to understanding climate extremes such as droughts, heatwaves and flooding. Regional ET estimates require reliable observation-based gridded ET datasets, and while many have been developed using physically based, empirically based and hybrid techniques, their efficacy, and particularly the efficacy of their uncertainty estimates, is difficult to verify. In this work, we extend the methodology used in Hobeichi et al. (2018) to derive two new versions of the Derived Optimal Linear Combination Evapotranspiration (DOLCE) product, with observationally constrained spatio-temporally varying uncertainty estimates, higher spatial resolution, more constituent products and extended temporal coverage (1980–2018). After demonstrating the efficacy of these uncertainty estimates with out-of-sample testing, we derive novel ET climatology clusters for the land surface, based on the magnitude and variability of ET at each location on land. The new clusters include three wet and three dry regimes and provide an approximation of Köppen–Geiger climate classes. The verified uncertainty estimates and extended time period then allow us to examine the robustness of historical trends spatially and in each of these six ET climatology clusters. We find that despite robust decreasing ET trends in some regions these do not correlate with behavioural ET clusters. Each cluster, and the majority of the Earth's surface, shows clear robust increases in ET over the recent historical period. The new datasets DOLCE V2.1 and DOLCE V3 can be used for benchmarking global ET estimates and for examining ET trends respectively.

scholarly journals Derived Optimal Linear Combination Evapotranspiration (DOLCE): a global gridded synthesis ET estimate

2018 ◽  
Vol 22 (2) ◽  
pp. 1317-1336 ◽  
Author(s):  
Sanaa Hobeichi ◽  
Gab Abramowitz ◽  
Jason Evans ◽  
Anna Ukkola
Keyword(s):  
Linear Combination ◽  
Energy Budgets ◽  
Weighted Mean ◽  
Weighting Method ◽  
Error Covariance ◽  
Optimal Linear Combination ◽  
Out Of Sample ◽  
Optimal Linear ◽  
Data Requirements ◽  
Better Than

Abstract. Accurate global gridded estimates of evapotranspiration (ET) are key to understanding water and energy budgets, in addition to being required for model evaluation. Several gridded ET products have already been developed which differ in their data requirements, the approaches used to derive them and their estimates, yet it is not clear which provides the most reliable estimates. This paper presents a new global ET dataset and associated uncertainty with monthly temporal resolution for 2000–2009. Six existing gridded ET products are combined using a weighting approach trained by observational datasets from 159 FLUXNET sites. The weighting method is based on a technique that provides an analytically optimal linear combination of ET products compared to site data and accounts for both the performance differences and error covariance between the participating ET products. We examine the performance of the weighting approach in several in-sample and out-of-sample tests that confirm that point-based estimates of flux towers provide information on the grid scale of these products. We also provide evidence that the weighted product performs better than its six constituent ET product members in four common metrics. Uncertainty in the ET estimate is derived by rescaling the spread of participating ET products so that their spread reflects the ability of the weighted mean estimate to match flux tower data. While issues in observational data and any common biases in participating ET datasets are limitations to the success of this approach, future datasets can easily be incorporated and enhance the derived product.

scholarly journals Derived Optimal Linear Combination Evapotranspiration (DOLCE): a global gridded synthesis ET estimate

2017 ◽  
Author(s):  
Sanaa Hobeichi ◽  
Gabriel Abramowitz ◽  
Jason Evans ◽  
Anna Ukkola
Keyword(s):  
Linear Combination ◽  
Energy Budgets ◽  
Weighted Mean ◽  
Weighting Method ◽  
Error Covariance ◽  
Optimal Linear Combination ◽  
Out Of Sample ◽  
Optimal Linear ◽  
Data Requirements ◽  
Better Than

Abstract. Accurate global gridded estimates of evapotranspiration (ET) are key to understanding water and energy budgets, as well as being required for model evaluation. Several gridded ET products have already been developed which differ in their data requirements, the approaches used to derive them and their estimates, yet it is not clear which provides the most reliable estimates. This paper presents a new global ET dataset and associated uncertainty with monthly temporal resolution for 2000–2009. Six existing gridded ET products are combined using a weighting approach trained by observational datasets from 159 FLUXNET sites. The weighting method is based on a technique that provides an analytically optimal linear combination of ET products compared to site data, and accounts for both the performance differences and error covariance between the participating ET products. We examine the performance of the weighting approach in several in-sample and out-of-sample tests that confirm that point-based estimates of flux towers provide information at the grid scale of these products. We also provide evidence that the weighted product performs better than its six constituent ET product members in three common metrics. Uncertainty in the ET estimate is derived by rescaling the spread of participating ET products so that their spread reflects the ability of the weighted mean estimate to match flux tower data. While issues in observational data and any common biases in participating ET datasets are limitations to the success of this approach, future datasets can easily be incorporated and enhance the derived product.

SOME MEASURES OF LEGAL RESPONSIBILITY FOR CORRUPTION OFFENSES IN THE LAW OF THE MOSCOW STATE OF THE XV-XVI CENTURIES

2020 ◽  
pp. 67-71
Author(s):  
Любовь Евгеньевна Логунова
Keyword(s):  
Corporal Punishment ◽  
Criminal Responsibility ◽  
Legal Liability ◽  
Legal Responsibility ◽  
Historical Period ◽  
Legal Interpretation ◽  
Present Stage ◽  
Legal Documents ◽  
Time Period ◽  
Russian Law

В статье автором проводится анализ законодательных памятников права Московского государства XV-XVI вв. и публично-правовых грамот. Выявляется проблема отсутствия законодательного закрепления таких понятий, как «коррупция», «коррупционное правонарушение». Предпринимается попытка определения данных понятий. Сравнивается понимание указанных явлений в XV-XVI вв. с современной правовой интерпретацией. Анализируются и раскрываются основные аспекты и особенности коррупционных правонарушений, характерные для периода Московского государства. Перечисляются меры противодействия коррупции на современном этапе и в рассматриваемом временном периоде. Изучаются не только такие известные памятники российского права, как судебники, но также и иные источники права периода XV-XVI вв. Перечисляются и раскрываются меры юридической ответственности за совершение коррупционных правонарушений. Дается краткая характеристика видам юридической ответственности, применяемым за совершение коррупционных правонарушений. Подчеркивается тяжесть уголовной ответственности, которую несли низшие судебные чиновники за совершение коррупционных правонарушений. Автор обращает внимание на то, что законодатель рассматриваемого периода придавал большое значение борьбе с чиновничьим произволом на местах. В ходе исследования автор приходит к выводу о том, что расширение видов мер юридической ответственности за коррупционные правонарушения, назначение тяжких телесных наказаний за совершение такого рода деяний не привело к искоренению коррупции в рассматриваемом историческом периоде. In the article, the author analyzes the legal monuments of the Moscow state of the XV-XVI centuries and public legal documents. The problem of the lack of legislative consolidation of such concepts as «corruption», «corruption offense» is revealed. An attempt is made to define these concepts. The understanding of these phenomena in the XV-XVI centuries is compared with the modern legal interpretation. The main aspects and features of corruption offenses typical for the period of the Moscow state are analyzed and disclosed. Measures to counteract corruption at the present stage and in the considered time period are listed. We study not only such well-known monuments of Russian law as sudebniki, but also other sources of law from the XV-XVI centuries the measures of legal responsibility for committing corruption offenses are Listed and disclosed. A brief description of the types of legal liability applied for corruption offenses is given. The author emphasizes the severity of the criminal responsibility that was borne by lower judicial officials for committing corruption offenses. The author draws attention to the importance that the legislator of the period under review attached to the fight against official arbitrariness on the ground. In the course of the study, the author comes to the conclusion that the expansion of the types of measures of legal responsibility for corruption offenses, the appointment of heavy corporal punishment for committing such acts did not lead to the eradication of corruption in the considered historical period.

THE USE OF HISTORICAL DATA IN ACCOUNTING RESEARCH: THE CASE OF THE AMERICAN SUGAR REFINING COMPANY

1997 ◽  
Vol 24 (2) ◽  
pp. 1-24 ◽  
Author(s):  
Robert Bricker ◽  
Kevin Brown
Keyword(s):  
Capital Market ◽  
Historical Data ◽  
Abnormal Returns ◽  
Deep Understanding ◽  
Historical Record ◽  
Historical Period ◽  
Financial Condition ◽  
A Value ◽  
Time Period ◽  
And Performance

In 1908, the American Sugar Refining Company (ASR) reversed its long-held policy of secrecy as to its financial condition and performance. Prior work, applying contemporary capital market methods to ASR security price data of that period, has suggested a value to ASR shareholders of this policy reversal. This paper examines the historical record of that time and presents additional evidence on this matter, particularly in terms of identifying potentially confounding events occurring during the period under study. The results of this analysis suggest a difficulty in attributing observed abnormal returns to ASR's secrecy policy reversal on the basis of the results obtained from applying capital markets methods. This analysis is useful for scholars interested in applying modern capital market methods to historical data. It highlights the significance of the possible effects of contemporaneous historical events, focuses attention on the importance of a deep understanding of the historical period studied, and suggests a value in combining historical and empirical-markets methods to gain a richer understanding of the events and conditions in the time period under study.

Toward a Robust Canopy Hydrology Scheme with Precipitation Subgrid Variability

2007 ◽  
Vol 8 (3) ◽  
pp. 439-446 ◽  
Author(s):  
Dagang Wang ◽  
Guiling Wang
Keyword(s):  
Land Surface ◽  
Surface Characteristics ◽  
Hydrological Processes ◽  
Canopy Interception ◽  
Time Step ◽  
Covered Area ◽  
Surface Models ◽  
Physically Based ◽  
Interception Loss ◽  
The Impact

Abstract Representation of the canopy hydrological processes has been challenging in land surface modeling due to the subgrid heterogeneity in both precipitation and surface characteristics. The Shuttleworth dynamic–statistical method is widely used to represent the impact of the precipitation subgrid variability on canopy hydrological processes but shows unwanted sensitivity to temporal resolution when implemented into land surface models. This paper presents a canopy hydrology scheme that is robust at different temporal resolutions. This scheme is devised by applying two physically based treatments to the Shuttleworth scheme: 1) the canopy hydrological processes within the rain-covered area are treated separately from those within the nonrain area, and the scheme tracks the relative rain location between adjacent time steps; and 2) within the rain-covered area, the canopy interception is so determined as to sustain the potential evaporation from the wetted canopy or is equal to precipitation, whichever is less, to maintain somewhat wet canopy during any rainy time step. When applied to the Amazon region, the new scheme establishes interception loss ratios of 0.3 at a 10-min time step and 0.23 at a 2-h time step. Compared to interception loss ratios of 0.45 and 0.09 at the corresponding time steps established by the original Shuttleworth scheme, the new scheme is much more stable under different temporal resolutions.

scholarly journals StreamFlow 1.0: an extension to the spatially distributed snow model Alpine3D for hydrological modelling and deterministic stream temperature prediction

2016 ◽  
Vol 9 (12) ◽  
pp. 4491-4519 ◽  
Author(s):  
Aurélien Gallice ◽  
Mathias Bavay ◽  
Tristan Brauchli ◽  
Francesco Comola ◽  
Michael Lehning ◽  
...  
Keyword(s):  
Source Code ◽  
Stream Temperature ◽  
Object Oriented Programming ◽  
Temperature Prediction ◽  
Uncertainty Estimates ◽  
Physically Based ◽  
Snow Model ◽  
Alpine Catchments ◽  
Alpine Rivers

Abstract. Climate change is expected to strongly impact the hydrological and thermal regimes of Alpine rivers within the coming decades. In this context, the development of hydrological models accounting for the specific dynamics of Alpine catchments appears as one of the promising approaches to reduce our uncertainty of future mountain hydrology. This paper describes the improvements brought to StreamFlow, an existing model for hydrological and stream temperature prediction built as an external extension to the physically based snow model Alpine3D. StreamFlow's source code has been entirely written anew, taking advantage of object-oriented programming to significantly improve its structure and ease the implementation of future developments. The source code is now publicly available online, along with a complete documentation. A special emphasis has been put on modularity during the re-implementation of StreamFlow, so that many model aspects can be represented using different alternatives. For example, several options are now available to model the advection of water within the stream. This allows for an easy and fast comparison between different approaches and helps in defining more reliable uncertainty estimates of the model forecasts. In particular, a case study in a Swiss Alpine catchment reveals that the stream temperature predictions are particularly sensitive to the approach used to model the temperature of subsurface flow, a fact which has been poorly reported in the literature to date. Based on the case study, StreamFlow is shown to reproduce hourly mean discharge with a Nash–Sutcliffe efficiency (NSE) of 0.82 and hourly mean temperature with a NSE of 0.78.

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 An assessment of the carbon balance of arctic tundra: comparisons among observations, process models, and atmospheric inversions

2012 ◽  
Vol 9 (4) ◽  
pp. 4543-4594 ◽  
Author(s):  
A. D. McGuire ◽  
T. R. Christensen ◽  
D. Hayes ◽  
A. Heroult ◽  
E. Euskirchen ◽  
...  
Keyword(s):  
Land Surface ◽  
Arctic Tundra ◽  
Process Models ◽  
Atmospheric Co2 ◽  
The Arctic ◽  
Uncertainty Estimates ◽  
Effective Transfer ◽  
And Inversion ◽  
Process Based Models ◽  
Observation Networks

Abstract. Although arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990–1999 and 2000–2006 among observations, regional and global applications of process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of the compilation of flux observations and of inversion model results indicate that the annual exchange of CO2 between arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of process-based model simulations suggests that arctic tundra acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Similarly, the observations and the applications of regional process-based models suggest that CH4 emissions from arctic tundra have increased from the 1990s to 2000s. Based on our analyses of the estimates from observations, process-based models, and inversion models, we estimate that arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1) and a source of CH4 to the atmosphere of 19 Tg C yr−1 (uncertainty between sources of 8 and 29 Tg C yr−1). The suite of analyses conducted in this study indicate that it is clearly important to reduce uncertainties in the observations, process-based models, and inversions in order to better understand the degree to which Arctic tundra is influencing atmospheric CO2 and CH4 concentrations. The reduction of uncertainties can be accomplished through (1) the strategic placement of more CO2 and CH4 monitoring stations to reduce uncertainties in inversions, (2) improved observation networks of ground-based measurements of CO2 and CH4 exchange to understand exchange in response to disturbance and across gradients of hydrological variability, and (3) the effective transfer of information from enhanced observation networks into process-based models to improve the simulation of CO2 and CH4 exchange from arctic tundra to the atmosphere.

Sign in / Sign up

Export Citation Format

Share Document