scholarly journals Exploring the Effect of Occurrence-Bias-Adjustment Assumptions on Hydrological Impact Modeling

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1573
Author(s):  
Jorn Van de Velde ◽  
Matthias Demuzere ◽  
Bernard De Baets ◽  
Niko E. C. Verhoest
Keyword(s):  
Climate Model ◽  
Climate Impact ◽  
Precipitation Intensity ◽  
Triangular Distribution ◽  
Broad Application ◽  
Bias Adjustment ◽  
Climate Impact Assessment ◽  
Continental Scale ◽  
Precipitation Occurrence ◽  
Climate Model Simulations

Bias adjustment of climate model simulations is a common step in the climate impact assessment modeling chain. For precipitation intensity, multiple bias-adjusting methods have been developed, but less so for precipitation occurrence. Intensity-bias-adjusting methods such as ‘Quantile Delta Mapping’ can adjust too many wet days, but not too many dry days. Some occurrence-bias-adjusting methods have been developed to resolve this by the addition of the ability to adjust too dry simulations. Earlier research has shown this to be important when adjusting on a continental scale, when both types of biases can occur. However, the newer occurrence-bias-adjusting methods have their weakness: they might retain a bias in the number of dry days when adjusting data in a region that only has too many wet days. Yet, if this bias is small enough, it is more practical and economical to apply the newer methods when data in the larger region are adjusted. In this study, we consider two recently introduced occurrence-bias-adjusting methods, Singularity Stochastic Removal and Triangular Distribution Adjustment, and compare them in a region with only wet-day biases. This bias adjustment is performed for precipitation intensity and precipitation occurrence, while the evaluation is performed on precipitation intensity, precipitation occurrence and discharge, which combines the former two variables. Despite theoretical weaknesses, we show that both Singularity Stochastic Removal and Triangular Distribution Adjustment perform well. Thus, the methods can be applied for both too wet and too dry simulations, although Triangular Distribution Adjustment may be preferred as it was designed with a broad application in mind.

scholarly journals Influences of Circulation and Climate Change on European Summer Heat Extremes

2013 ◽  
Vol 26 (23) ◽  
pp. 9621-9632 ◽  
Author(s):  
Robin T. Clark ◽  
Simon J. Brown
Keyword(s):  
Climate Model ◽  
Circulation Type ◽  
Root Depth ◽  
Atmospheric Circulation Patterns ◽  
Continental Scale ◽  
Circulation Types ◽  
Circulation Patterns ◽  
Hot Days ◽  
Climate Model Simulations ◽  
Heat Extremes

Atmospheric circulation patterns occurring on the warmest 10% of summer days for a region of Europe severely impacted by the 2003 heatwave have been identified using a perturbed parameter ensemble of regional high-resolution climate model simulations for the recent past. Changes in the frequency and duration of these circulation types, driven by the simulations following a moderate transient pathway of anthropogenic emissions, are then shown for the period 2070 to 2100. Increases in the future probability of hot days are then attributed separately to changes in the frequency and temperature intensity of the circulation types. Changes in temperature intensity are found to have an effect 2 to 3 times larger than in frequency. The authors then consider how model uncertainty in changes of future temperature within circulation patterns compares to the uncertainty irrespective of circulation, in an attempt to exclude contributions to the overall uncertainty arising from changes in circulation. Within individual patterns, the range of meteorological physical processes may be narrower. However, no reduction in uncertainty was found when single patterns were considered. Contributions to the lack of narrowing from circulation-type duration, model vegetation root depth and changes in cloud cover, pressure gradient, and continental-scale warming are subsequently examined using relationships between changes in surface latent heat and temperature. Vegetation root depth is found to be the greatest contributor to the temperature uncertainty.

scholarly journals Estimating the Effective Radiative Forcing of Contrail Cirrus

2020 ◽  
Vol 33 (5) ◽  
pp. 1991-2005 ◽  
Author(s):  
Marius Bickel ◽  
Michael Ponater ◽  
Lisa Bock ◽  
Ulrike Burkhardt ◽  
Svenja Reineke
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Climate Models ◽  
Climate Model ◽  
Climate Impact ◽  
Lapse Rate ◽  
Reference Case ◽  
Radiative Forcings ◽  
Effective Radiative Forcing ◽  
Climate Model Simulations

AbstractEvidence from previous climate model simulations has suggested a potentially low efficacy of contrails to force global mean surface temperature changes. In this paper, a climate model with a state-of-the-art contrail cirrus representation is used for fixed sea surface temperature simulations in order to determine the effective radiative forcing (ERF) from contrail cirrus. ERF is expected to be a good metric for intercomparing the quantitative importance of different contributions to surface temperature and climate impact. Substantial upscaling of aviation density is necessary to ensure statistically significant results from our simulations. The contrail cirrus ERF is found to be less than 50% of the respective instantaneous or stratosphere adjusted radiative forcings, with a best estimate of roughly 35%. The reduction of ERF is much more substantial for contrail cirrus than it is for a CO2 increase when both stratosphere adjusted forcings are of similar magnitude. Analysis of all rapid radiative adjustments contributing to the ERF indicates that the reduction is mainly induced by a compensating effect of natural clouds that provide a negative feedback. Compared to the CO2 reference case, a less positive combined water vapor and lapse rate adjustment also contributes to a more distinct reduction of contrail cirrus ERF, but not as much as the natural cloud adjustment. Based on the experience gained in this paper, respective contrail cirrus simulations with interactive ocean will be performed as the next step toward establishing contrail cirrus efficacy. ERF results of contrail cirrus from other climate models equipped with suitable parameterizations are regarded as highly desirable.

scholarly journals Bias adjustment for threshold-based climate indicators

2018 ◽  
Vol 15 ◽  
pp. 107-116
Author(s):  
Peter Hoffmann ◽  
Christoph Menz ◽  
Arne Spekat
Keyword(s):  
Climate Model ◽  
Heavy Precipitation ◽  
Threshold Value ◽  
Maximum Temperature ◽  
Climate Projections ◽  
Climate Data ◽  
Bias Adjustment ◽  
Climate Indicators ◽  
Climate Model Simulations ◽  
The Individual

Abstract. A method is presented which applies bias adjustments to climate indicators that are based on fixed thresholds, e.g., the number of hot days with the maximum temperature exceeding 30 ∘C or the number of days with heavy precipitation in exceedance of 20 mm rainfall. The bias adjustment first identifies the percentile of the required threshold value in reference climate data. Then it computes the value of this percentile for the individual historical climate model simulations – here an ensembles of EURO-CORDEX model runs, including dynamical and statistical models. Finally, the climate indicator is re-calculated for each model. The method is applied to climate projections as well, giving further insight into the projected development of the ensemble for extreme conditions. It is assessed that communication to the public and decision makers is improved by expressing these changes in extremes based on absolute values.

scholarly journals Extreme precipitation on consecutive days occurs more often in a warming climate

2021 ◽  
Keyword(s):  
Extreme Precipitation ◽  
Climate Model ◽  
Temporal Correlation ◽  
Global Scale ◽  
Precipitation Intensity ◽  
Warming Climate ◽  
Intensity Changes ◽  
Climate Model Simulations ◽  
Increasing Precipitation

Abstract Extreme precipitation occurring on consecutive days may substantially increase the risk of related impacts, but changes in such events have not been studied at a global scale. Here we use a unique global dataset based on in situ observations and multi-model historical and future simulations to analyse the changes in the frequency of extreme precipitation on consecutive days (EPCD). We further disentangle the relative contributions of variations in precipitation intensity and temporal correlation of extreme precipitation, to understand the processes that drive the changes in EPCD. Observations and climate model simulations show that the frequency of EPCD is increasing in most land regions, in particular in North America, Europe and the Northern Hemisphere high latitudes. These increases are primarily a consequence of increasing precipitation intensity, but changes in the temporal correlation of extreme precipitation regionally amplify or reduce the effects of intensity changes. Changes are larger in simulations with a stronger warming signal, suggesting that further increases in EPCD are expected for the future under continued climate warming.

scholarly journals Added value of the EURO-CORDEX high-resolution downscaling over the Iberian Peninsula revisited. Part I: Precipitation

2021 ◽  
Author(s):  
João António Martins Careto ◽  
Pedro Miguel Matos Soares ◽  
Rita Margarida Cardoso ◽  
Sixto Herrera ◽  
José Manuel Guttiérrez
Keyword(s):  
Iberian Peninsula ◽  
Climate Model ◽  
Regional Climate ◽  
Regional Model ◽  
Precipitation Extremes ◽  
Added Value ◽  
Model Ensemble ◽  
Continental Scale ◽  
Climate Model Simulations ◽  
Computational Resources

Abstract. Over the years higher resolution Regional Climate Model simulations have emerged owing to the large increase in computational resources. The 12 Km resolution from the Coordinated Regional Climate Downscaling Experiment for the European domain (EURO-CORDEX) is a reference, which includes a larger multi-model ensemble at a continental scale while spanning at least a 130-year period. These simulations are computationally demanding but not always revealing added value. In this study, a recently developed regular gridded dataset (Iberia0.1) and a new metric for added value quantification, the distribution added value (DAV), are used to assess the precipitation of all available EURO-CORDEX Hindcast (1989–2008) and Historical (1971–2005) simulations. This approach enables a direct assessment between the higher resolution regional model runs against their forcing Global model or ERA-Interim reanalysis, with respect to their PDFs. This assessment is performed for the Iberian Peninsula. Overall, important gains are found for most cases, particularly in precipitation extremes. Most Hindcast models reveal gains above 15 %, namely for wintertime, while for precipitation extremes values above 20 % are reached for the summer and autumn. As for the Historical models, although most pairs display gains, regional models forced by 2 GCMs reveal losses, sometimes around −5 % or stronger, for the entire year. However, the spatialization of the DAV is clear in terms of added value for precipitation, particularly precipitation extremes with significant gains, above 100 %.

scholarly journals Towards Determining the Contrail Cirrus Efficacy

Aerospace ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 42
Author(s):  
Michael Ponater ◽  
Marius Bickel ◽  
Lisa Bock ◽  
Ulrike Burkhardt
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Climate Model ◽  
Research Work ◽  
Temperature Response ◽  
Climate Impact ◽  
Mitigation Measures ◽  
Recent Climate ◽  
Effective Radiative Forcing ◽  
Climate Model Simulations

Contrail cirrus has been emphasized as the largest individual component of aircraft climate impact, yet respective assessments have been based mainly on conventional radiative forcing calculations. As demonstrated in previous research work, individual impact components can have different efficacies, i.e., their effectiveness to induce surface temperature changes may vary. Effective radiative forcing (ERF) has been proposed as a superior metric to compare individual impact contributions, as it may, to a considerable extent, include the effect of efficacy differences. Recent climate model simulations have provided a first estimate of contrail cirrus ERF, which turns out to be much smaller, by about 65%, than the conventional radiative forcing of contrail cirrus. The main reason for the reduction is that natural clouds exhibit a substantially lower radiative impact in the presence of contrail cirrus. Hence, the new result suggests a smaller role of contrail cirrus in the context of aviation climate impact (including proposed mitigation measures) than assumed so far. However, any conclusion in this respect should be drawn carefully as long as no direct simulations of the surface temperature response to contrail cirrus are available. Such simulations are needed in order to confirm the power of ERF for assessing contrail cirrus efficacy.

Sign in / Sign up

Export Citation Format

Share Document