scholarly journals Winter extreme weather in EURO-CORDEX climate models and their links to large-scale atmospheric circulation

2021 ◽  
Author(s):  
Eva Plavcová ◽  
Ondřej Lhotka ◽  
Jan Stryhal
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Regional Scale ◽  
Global Climate Models ◽  
Wind Gust ◽  
Climate Change Scenarios ◽  
Winter Weather ◽  
Large Scale Atmospheric Circulation

<p>Regional Climate Models (RCMs) are powerful tools to study changes in the climate system on the regional scale. However, the reliability of their simulations has been considerably limited by the longstanding issue that climate models often fail to reproduce various aspects of the historical climate. In our study, we analyse how RCMs from the EURO-CORDEX project are able to reproduce extreme winter weather. We analyse temporal and spatial characteristics of extreme wind gust, extremely cold temperature, and extreme precipitation. Model outputs are validated against observed data from the European gridded observational database (EOBS) and the novel ERA5 reanalysis. We focus on the Central European domain (defined between 48–52°N and 10–19°E) over the 1979 – 2017 period. We investigate a set of 9 simulations of 3 different RCMs driven by 3 different global climate models which allow us to analyse the influence of driving data on the RCM’s performance. Since local climate elements are relatively tightly linked to a large-scale atmospheric circulation over Europe in winter, we also evaluate the ability of RCMs to reproduce the atmospheric circulation and its links to selected high-impact winter weather in detail. We use the classification of circulation based on the method of Sammon mapping. Investigation of these links can lead to better physical understanding of the climate and to the identification of inadequacies in simulated characteristics of the studied events. All of this is an important step forward in further improving the models and enhancing the credibility of climate change scenarios based on climate model simulations.</p>

High-impact winter weather in EURO-CORDEX climate models and their links to large-scale atmospheric circulation

2020 ◽  
Author(s):  
Eva Plavcová ◽  
Ondřej Lhotka ◽  
Jan Stryhal
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Regional Scale ◽  
High Impact ◽  
Global Climate Models ◽  
Wind Gust ◽  
Climate Change Scenarios ◽  
Winter Weather ◽  
Large Scale Atmospheric Circulation

<p>Regional Climate Models (RCMs) are powerful tools to study changes in the climate system on the regional scale. However, the reliability of their simulations has been considerably limited by the longstanding issue that climate models often fail to reproduce various aspects of the historical climate. In our study, we analyse how RCMs from the EURO-CORDEX project are able to reproduce high-impact winter weather. We analyse temporal and spatial characteristics of snowfalls, wind gust, extreme temperatures, late spring frosts, total precipitation, and winter storms. Model outputs are validated against observed data from the gridded European database (EOBS) and the novel ERA5 reanalysis. We focus on the Central European domain (defined roughly between 48–52°N and 10–20°E) over the 1979 – 2017 period. We investigate a set of 12 simulations of 4 different RCMs driven by 3 different global climate models which allow us to analyse the influence of driving data on the RCM’s performance. Since local climate elements are relatively tightly linked to a large-scale atmospheric circulation over Europe in winter, we also evaluate the ability of RCMs to reproduce the atmospheric circulation and its links to selected high-impact winter weather in detail. Investigation of these links can lead to better physical understanding of the climate and to the identification of inadequacies in simulated characteristics of the studied events. All of this is an important step forward in further improving the models and enhancing the credibility of climate change scenarios based on climate model simulations.</p>

Evaluation of the tropical water vapor of CMIP6 GCMs with ESA CCI+ “Water Vapor” climate data records: Insights from large-scale atmospheric circulation

2021 ◽  
Author(s):  
Helene Brogniez ◽  
Jia He ◽  
Laurence Picon ◽  
Marc Schroder ◽  
René Preusker ◽  
...  
Keyword(s):  
Water Vapor ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Climate Models ◽  
Global Climate Models ◽  
Tropical Region ◽  
Tropical Atmosphere ◽  
Climate Data ◽  
Dynamical Regimes ◽  
Large Scale Atmospheric Circulation

<p>Water vapor is one of the fundamental elements in the atmosphere. Its distribution is strongly associated with large-scale atmospheric circulation. Here the new global water vapor climate data records (CDR) generated within the ESA Water Vapor CCI+ project (WV_cci) is used to perform a comprehensive evaluation of total column water vapor provided by 21 global climate models (CMIP6 framework). The ESA WV_cci CDRs cover the period 2002-2017 with a daily frequency and a regular 0.5° spatial resolution. The focus is on the tropical region (30°S - 30°N). The observational diagnostic relies on the decomposition of the tropical atmosphere into large-scale dynamical regimes using the 500 hPa atmospheric vertical velocity w<sub>500</sub> (in hPa/day) as a proxy. The ESA WV_cci and the CMIP6 data are then sorted according to dynamical regimes (intervals of 10 hPa/day) allowing to study the evolution of the regimes in terms of frequency of occurrence and is linked to water vapor variation. While the basic picture of the tropical atmosphere is properly represented by the models (moister in ascending branches, drier in subsiding branches) there are noticeable differences in the patterns that will be discussed. The inter-annual variation of water vapor for both observation and the models will be analyzed, and the trend significance are assessed using Mann-Kendall test. This highlights the interest of water vapor climate data records for model evaluation.</p>

scholarly journals Influence of the representation of convection on the mid-Holocene West African Monsoon

2021 ◽  
Vol 17 (4) ◽  
pp. 1665-1684
Author(s):  
Leonore Jungandreas ◽  
Cathy Hohenegger ◽  
Martin Claussen
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Monsoon Season ◽  
West African Monsoon ◽  
West African ◽  
Global Climate Models ◽  
African Monsoon ◽  
Monsoonal Precipitation

Abstract. Global climate models experience difficulties in simulating the northward extension of the monsoonal precipitation over north Africa during the mid-Holocene as revealed by proxy data. A common feature of these models is that they usually operate on grids that are too coarse to explicitly resolve convection, but convection is the most essential mechanism leading to precipitation in the West African Monsoon region. Here, we investigate how the representation of tropical deep convection in the ICOsahedral Nonhydrostatic (ICON) climate model affects the meridional distribution of monsoonal precipitation during the mid-Holocene by comparing regional simulations of the summer monsoon season (July to September; JAS) with parameterized and explicitly resolved convection. In the explicitly resolved convection simulation, the more localized nature of precipitation and the absence of permanent light precipitation as compared to the parameterized convection simulation is closer to expectations. However, in the JAS mean, the parameterized convection simulation produces more precipitation and extends further north than the explicitly resolved convection simulation, especially between 12 and 17∘ N. The higher precipitation rates in the parameterized convection simulation are consistent with a stronger monsoonal circulation over land. Furthermore, the atmosphere in the parameterized convection simulation is less stably stratified and notably moister. The differences in atmospheric water vapor are the result of substantial differences in the probability distribution function of precipitation and its resulting interactions with the land surface. The parametrization of convection produces light and large-scale precipitation, keeping the soils moist and supporting the development of convection. In contrast, less frequent but locally intense precipitation events lead to high amounts of runoff in the explicitly resolved convection simulations. The stronger runoff inhibits the moistening of the soil during the monsoon season and limits the amount of water available to evaporation in the explicitly resolved convection simulation.

scholarly journals Downscale of future climate change scenarios applied to Recife-PE

2020 ◽  
Vol 9 (6) ◽  
pp. 361
Author(s):  
Rafaela Lisboa Costa ◽  
Heliofábio Barros Gomes ◽  
Fabrício Daniel Dos Santos Silva ◽  
Rodrigo Lins Da Rocha Júnior
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Reanalysis Data ◽  
Global Climate Models ◽  
Future Climate ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
The Future ◽  
Maximum Temperatures

The objective of this work was to analyze and compare results from two generations of global climate models (GCMs) simulations for the city of Recife-PE: CMIP3 and CMIP5. Differences and similarities in historical and future climate simulations are presented for four GCMs using CMIP3 scenarios A1B and A2 and for seven CMIP5 scenarios RCP4.5 and RCP8.5. The scale reduction technique applied to GCMs scenarios is statistical downscaling, employing the same set of large-scale atmospheric variables as predictors for both sets of scenarios, differing only in the type of reanalysis data used to characterize surface variables precipitation, maximum and minimum temperatures. For CMIP3 scenarios the simulated historical climate is 1961-1990 and CMIP5 is 1979-2000, and the validation period is ten years, 1991-2000 for CMIP3 and 2001-2010 for CMIP5. However, for both the future period analyzed is 2021-2050 and 2051-2080. Validation metrics indicated superior results from the historical simulations of CMIP5 over those of CMIP3 for precipitation and minimum and similar temperatures for maximum temperatures. For the future, both CMIP3 and CMIP5 scenarios indicate reduced precipitation and increased temperatures. The potencial evapotranspiration was calculated, projected to increase in scenarios A1B and A2 of CMIP3 and with behavior similar to that observed historically in scenarios RCP4.5 and 8.5.

scholarly journals Saharan Heat Low Biases in CMIP5 Models

2017 ◽  
Vol 30 (8) ◽  
pp. 2867-2884 ◽  
Author(s):  
Ross D. Dixon ◽  
Anne Sophie Daloz ◽  
Daniel J. Vimont ◽  
Michela Biasutti
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
West African Monsoon ◽  
West African ◽  
Global Climate Models ◽  
Cmip5 Models ◽  
African Climate ◽  
Heat Low

Representing the West African monsoon (WAM) is a major challenge in climate modeling because of the complex interaction between local and large-scale mechanisms. This study focuses on the representation of a key aspect of West African climate, namely the Saharan heat low (SHL), in 22 global climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) multimodel dataset. Comparison of the CMIP5 simulations with reanalyses shows large biases in the strength and location of the mean SHL. CMIP5 models tend to develop weaker climatological heat lows than the reanalyses and place them too far southwest. Models that place the climatological heat low farther to the north produce more mean precipitation across the Sahel, while models that place the heat low farther to the east produce stronger African easterly wave (AEW) activity. These mean-state biases are seen in model ensembles with both coupled and fixed sea surface temperatures (SSTs). The importance of SSTs on West African climate variability is well documented, but this research suggests SSTs are secondary to atmospheric biases for understanding the climatological SHL bias. SHL biases are correlated across the models to local radiative terms, large-scale tropical precipitation, and large-scale pressure and wind across the Atlantic, suggesting that local mechanisms that control the SHL may be connected to climate model biases at a much larger scale.

Drought modelling under climate change scenarios and its probabilistic characterization: A Review

2021 ◽  
pp. 403-417
Author(s):  
Amit Dubey ◽  
Deepak Swami ◽  
Nitin Joshi
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Climate Models ◽  
Time Window ◽  
Global Climate ◽  
Global Climate Models ◽  
Climate Indices ◽  
Climate Change Scenarios ◽  
Drought Forecasting ◽  
Copula Models

ncrease in the water scarcity and the related rise in demand of water coupled with the threating events of climate change, ultimately witnessed drought in the recent years to occur frequently. Therefore, Drought hydrology is drawing most of the attention. Drought which is a natural hazard can be best characterized by various hydrological and climatological parameters. In order to model drought, researchers have applied various concepts starting from simplistic model to the complex ones. The suitability of different modelling approaches and their negative and positive traits are very essential to comprehend. This paper is an attempt to review various methodologies utilized in modelling of drought such as forecasting of drought, drought modelling based on probability, Global Climate Models (GCM) under climate change scenarios. It is obtained from the present study that the past three decades have witnessed a very significant improvement in the drought modelling studies. For the larger time window of drought forecasting, hybrid models which incorporates large scale climate indices are promisingly suitable. Drought characterization based on copula models for multivariate drought characterization seems to have an edge over the others. At the end some conclusive remarks are made as far as the future drought modelling and research is concerned.

scholarly journals Process-oriented analysis of aircraft soot-cirrus interactions constrains the climate impact of aviation

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Bernd Kärcher ◽  
Fabian Mahrt ◽  
Claudia Marcolli
Keyword(s):  
Radiative Forcing ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Climate Impact ◽  
Global Climate Models ◽  
Soot Particles ◽  
Cloud Ice ◽  
The Impact

AbstractFully accounting for the climate impact of aviation requires a process-level understanding of the impact of aircraft soot particle emissions on the formation of ice clouds. Assessing this impact with the help of global climate models remains elusive and direct observations are lacking. Here we use a high-resolution cirrus column model to investigate how aircraft-emitted soot particles, released after ice crystals sublimate at the end of the lifetime of contrails and contrail cirrus, perturb the formation of cirrus. By allying cloud simulations with a measurement-based description of soot-induced ice formation, we find that only a small fraction (<1%) of the soot particles succeeds in forming cloud ice alongside homogeneous freezing of liquid aerosol droplets. Thus, soot-perturbed and homogeneously-formed cirrus fundamentally do not differ in optical depth. Our results imply that climate model estimates of global radiative forcing from interactions between aircraft soot and large-scale cirrus may be overestimates. The improved scientific understanding reported here provides a process-based underpinning for improved climate model parametrizations and targeted field observations.

Verification of GCM-Generated Regional Seasonal Precipitation for Current Climate and of Statistical Downscaling Estimates under Changing Climate Conditions

1999 ◽  
Vol 12 (1) ◽  
pp. 258-272 ◽  
Author(s):  
Aristita Busuioc ◽  
Hans von Storch ◽  
Reiner Schnur
Keyword(s):  
Climate Change ◽  
Statistical Downscaling ◽  
Large Scale ◽  
Climate Models ◽  
Regional Scale ◽  
The Other ◽  
Change Scenario ◽  
Climate Change Scenarios ◽  
Seasonal Precipitation ◽  
Empirical Downscaling

Abstract Empirical downscaling procedures relate large-scale atmospheric features with local features such as station rainfall in order to facilitate local scenarios of climate change. The purpose of the present paper is twofold: first, a downscaling technique is used as a diagnostic tool to verify the performance of climate models on the regional scale; second, a technique is proposed for verifying the validity of empirical downscaling procedures in climate change applications. The case considered is regional seasonal precipitation in Romania. The downscaling model is a regression based on canonical correlation analysis between observed station precipitation and European-scale sea level pressure (SLP). The climate models considered here are the T21 and T42 versions of the Hamburg ECHAM3 atmospheric GCM run in “time-slice” mode. The climate change scenario refers to the expected time of doubled carbon dioxide concentrations around the year 2050. The downscaling model is skillful for all seasons except spring. The general features of the large-scale SLP variability are reproduced fairly well by both GCMs in all seasons. The climate models reproduce the empirically determined precipitation–SLP link in winter, whereas the observed link is only partially captured for the other seasons. Thus, these models may be considered skillful with respect to regional precipitation during winter, and partially during the other seasons. Generally, applications of statistical downscaling to climate change scenarios have been based on the assumption that the empirical link between the large-scale and regional parameters remains valid under a changed climate. In this study, a rationale is proposed for this assumption by showing the consistency of the 2 × CO2 GCM scenarios in winter, derived directly from the gridpoint data, with the regional scenarios obtained through empirical downscaling. Since the skill of the GCMs in regional terms is already established, it is concluded that the downscaling technique is adequate for describing climatically changing regional and local conditions, at least for precipitation in Romania during winter.

Model Uncertainty in Cloud–Circulation Coupling, and Cloud-Radiative Response to Increasing CO2, Linked to Biases in Climatological Circulation

2018 ◽  
Vol 31 (24) ◽  
pp. 10013-10020
Author(s):  
Bernard R. Lipat ◽  
Aiko Voigt ◽  
George Tselioudis ◽  
Lorenzo M. Polvani
Keyword(s):  
Model Uncertainty ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Global Climate Models ◽  
Hadley Cell ◽  
Temperature Structure ◽  
Climatological Circulation

Recent analyses of global climate models suggest that uncertainty in the coupling between midlatitude clouds and the atmospheric circulation contributes to uncertainty in climate sensitivity. However, the reasons behind model differences in the cloud–circulation coupling have remained unclear. Here, we use a global climate model in an idealized aquaplanet setup to show that the Southern Hemisphere climatological circulation, which in many models is biased equatorward, contributes to the model differences in the cloud–circulation coupling. For the same poleward shift of the Hadley cell (HC) edge, models with narrower climatological HCs exhibit stronger midlatitude cloud-induced shortwave warming than models with wider climatological HCs. This cloud-induced radiative warming results predominantly from a subsidence warming that decreases cloud fraction and is stronger for narrower HCs because of a larger meridional gradient in the vertical velocity. A comparison of our aquaplanet results with comprehensive climate models suggests that about half of the model uncertainty in the midlatitude cloud–circulation coupling stems from this impact of the circulation on the large-scale temperature structure of the atmosphere, and thus could be removed by improving the climatological circulation in models. This illustrates how understanding of large-scale dynamics can help reduce uncertainty in clouds and their response to climate change.

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