Internal Atlantic Multidecadal Variability mechanism at two model resolutions 

2021 ◽  
Author(s):  
Michael Lai ◽  
Jon Robson ◽  
Laura Wilcox ◽  
Nick Dunstone
Keyword(s):  
Climate Models ◽  
Surface Fluxes ◽  
The Arctic ◽  
Atlantic Multidecadal Variability ◽  
Surface Cooling ◽  
Arctic Water ◽  
Multidecadal Variability ◽  
Wide Range ◽  
Resolution Model ◽  
The Impact

<p>The Atlantic Multidecadal Variability (AMV) is a key factor in modulating climate change and its impacts around the world. Therefore, understanding of its physical mechanism will be crucial to achieving predictability on decadal timescales. However, details of the mechanism are not fully understood. This is evident in the wide range of simulated AMV timescales and spatial patterns exhibited by climate models in both pre-industrial and historical simulations.</p><p>In this study, we assess the impact of model resolution on the internal AMV mechanism by taking advantage of the close physical similarities between the medium- and low-resolution versions of the HadGEM3 models. Here, we present results from analysing the N96ORCA1 (~135km atmosphere, 1° ocean) and N216ORCA025 (~60km, 0.25°) pre-industrial simulations.</p><p>At both resolutions, we found that the internal AMV has a timescale of 70-100 years, comparable to the observed record. The processes driving decadal SST variability varies by latitude. Ocean heat transport changes associated with the AMOC drive subpolar variability, while surface fluxes associated with cloud and wind changes are more important in the subtropics. The AMOC strengthening is induced by density forcing from two sources. First, a Labrador Sea surface cooling driven by low-frequency positive NAO leads the AMOC by 5 years. Second, a source of anomalously saline Arctic water flowing into the subpolar North Atlantic also leads the AMOC by 5 years. Interestingly, the two resolutions disagree on the relative importance of these AMOC drivers. In the lower resolution model, the Arctic contribution is more important. However, the NAO dominates in the medium resolution model, and decadal NAO variability is more strongly associated with the AMV. Differences between the models are likely due to mean state differences including the strength and position of ocean currents such as the Gulf Stream, and their impacts on upper ocean properties.</p><p> </p>

The role of air-sea ice-ocean interaction processes for Arctic-midlatitude linkages

2020 ◽  
Author(s):  
Sara Khosravi ◽  
Annette Rinke ◽  
Wolfgang Dorn ◽  
Christof Lüpkes ◽  
Vladimir Gryanik ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
Large Scale ◽  
Climate Models ◽  
Arctic Sea Ice ◽  
Surface Fluxes ◽  
The Arctic ◽  
Russian Science ◽  
Large Scale Circulation ◽  
The Impact

<p>Climate models have deficits in reproducing Arctic circulation and sea ice development. The air-sea ice-ocean interaction parametrizations could be a potential reason of this shortcoming. In most climate models air-sea ice-ocean interaction are parametrized based on mid-latitude conditions which is not appropriate for polar region. The POLEX project, funded by Helmholtz Association and Russian Science Foundation, is studying the impact of improved representation of Arctic air-sea ice-ocean interaction on changes in Arctic atmospheric circulation and Arctic-midlatitude linkages. We have used a new suite of parametrizations, which are easily applicable for climate simulations and have been developed based on SHEBA expedition data by Gryanik and Lüpkes (2018). We implemented the new parametrizations in the global atmospheric model (ECHAM6) in the framework of POLEX to estimate its effect on regional Arctic and large-scale circulation changes. Several steps have been defined for implementing the new parameterization to be able to distinguish and understand better the impact of its parameters. Roughness length and stability functions for stable stratification have been modified. Here the initial results of ECHAM6 sensitivity runs for different steps of the parameterization will be presented. We will present first results from process-oriented evaluation over the Arctic sea ice, e.g. how is the impact on the simulation of the two states of the Arctic boundary layer in winter. Furthermore, we will show that the large-scale circulation reacts to the new parametrization in different months and years differently.<br>Reference:<br>Gryanik, V.M. and C. Lüpkes (2018) An efficient non-iterative bulk parametrization of surface fluxes for stable atmospheric conditions over polar sea-ice, Boundary-Layer Meteorol., 166, 301-325</p>

A MODELING SYSTEM FOR CLIMATE CHANGE RISK ASSESSMENT, MANAGEMENT AND HEDGING IN COASTAL AREAS

2017 ◽  
Author(s):  
Sergei Soldatenko ◽  
Sergei Soldatenko ◽  
Genrikh Alekseev ◽  
Genrikh Alekseev ◽  
Alexander Danilov ◽  
...  
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Coastal Areas ◽  
Mitigation Strategies ◽  
System Structure ◽  
The Arctic ◽  
Risk Modeling ◽  
Wide Range ◽  
Adverse Weather ◽  
The Impact

Every aspect of human operations faces a wide range of risks, some of which can cause serious consequences. By the start of 21st century, mankind has recognized a new class of risks posed by climate change. It is obvious, that the global climate is changing, and will continue to change, in ways that affect the planning and day to day operations of businesses, government agencies and other organizations and institutions. The manifestations of climate change include but not limited to rising sea levels, increasing temperature, flooding, melting polar sea ice, adverse weather events (e.g. heatwaves, drought, and storms) and a rise in related problems (e.g. health and environmental). Assessing and managing climate risks represent one of the most challenging issues of today and for the future. The purpose of the risk modeling system discussed in this paper is to provide a framework and methodology to quantify risks caused by climate change, to facilitate estimates of the impact of climate change on various spheres of human activities and to compare eventual adaptation and risk mitigation strategies. The system integrates both physical climate system and economic models together with knowledge-based subsystem, which can help support proactive risk management. System structure and its main components are considered. Special attention is paid to climate risk assessment, management and hedging in the Arctic coastal areas.

scholarly journals Clouds damp the radiative impacts of polar sea ice loss

2020 ◽  
Vol 14 (8) ◽  
pp. 2673-2686 ◽  
Author(s):  
Ramdane Alkama ◽  
Patrick C. Taylor ◽  
Lorea Garcia-San Martin ◽  
Herve Douville ◽  
Gregory Duveiller ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Surface Radiation ◽  
Radiation Budget ◽  
The Arctic ◽  
Cloud Properties ◽  
Surface Radiation Budget ◽  
Cloud Radiative Effect ◽  
Radiative Impact ◽  
The Impact

Abstract. Clouds play an important role in the climate system: (1) cooling Earth by reflecting incoming sunlight to space and (2) warming Earth by reducing thermal energy loss to space. Cloud radiative effects are especially important in polar regions and have the potential to significantly alter the impact of sea ice decline on the surface radiation budget. Using CERES (Clouds and the Earth's Radiant Energy System) data and 32 CMIP5 (Coupled Model Intercomparison Project) climate models, we quantify the influence of polar clouds on the radiative impact of polar sea ice variability. Our results show that the cloud short-wave cooling effect strongly influences the impact of sea ice variability on the surface radiation budget and does so in a counter-intuitive manner over the polar seas: years with less sea ice and a larger net surface radiative flux show a more negative cloud radiative effect. Our results indicate that 66±2% of this change in the net cloud radiative effect is due to the reduction in surface albedo and that the remaining 34±1 % is due to an increase in cloud cover and optical thickness. The overall cloud radiative damping effect is 56±2 % over the Antarctic and 47±3 % over the Arctic. Thus, present-day cloud properties significantly reduce the net radiative impact of sea ice loss on the Arctic and Antarctic surface radiation budgets. As a result, climate models must accurately represent present-day polar cloud properties in order to capture the surface radiation budget impact of polar sea ice loss and thus the surface albedo feedback.

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.

NUKLEUS - User-relevant and applicable kilometer-scale climate information for Germany

2021 ◽  
Author(s):  
Kevin Sieck ◽  
Bente Tiedje ◽  
Hendrik Feldmann ◽  
Joaquim Pinto
Keyword(s):  
Climate Models ◽  
Local Scale ◽  
Easy Access ◽  
Climate Information ◽  
Post Processing ◽  
Last Mile ◽  
Wide Range ◽  
Impact Modelling ◽  
The Impact ◽  
Impact Models

<p>Given the current developments in climate science it becomes more a more feasible to provide climate information at the kilometer-scale from convection-permitting climate simulations. This progress will enable many users to directly feed high-resolution climate information into their impact-models for climate impact studies at the local scale. Examples include urban heat stress at street level or the design of drainage systems for future precipitation extremes. Within the RegIKlim (Regional information for action on climate change) consortium, the NUKLEUS (Actionable local climate information for Germany) project will not only provide climate information at the local scale, but also to co-develop interfaces between climate and impact models, in order to fulfil the needs of the impact modelling community as good as possible. Within the RegIKlim consortium, the impact modelling community is organised in six “model regions” across Germany, which cover a wide range of geographical and socio-economic conditions.</p><p>For the NUKLEUS project, the baseline will be the latest generation of EURO-CORDEX downscaled CMIP6 simulations, which will be further refined to roughly 3 km horizontal resolution and 30-year time-slices for Germany with convection-permitting climate models (ICON CLM, COSMO-CLM, REMO-NH) and statistical-dynamical downscaling approaches. A detailed analysis on the performance of the multi-model mini-ensemble is planned to assess the quality of the provided data. At the interface to the users, we will follow three different approaches to provide usable climate information at the kilometer-scale. One is to provide easy-access to data and post-processing opportunities using the FREVA system. FREVA offers various access-levels from shell to web-based, which serves different levels of user-expertise. In addition, it provides a transparent way of post-processing data by workflow sharing mechanisms. The second one is to develop appropriate additional downscaling methods for the “last mile” where needed. For this “last mile”, we will apply dynamical and statistical methods such as urban climate models and/or weather generators. With the third approach we explicitly aim at integrating a collected user-feedback into the regional modelling systems used within NUKLEUS. Specifically, we intend to identify and incorporate data processing that is best done during the simulation permanently into the models. Examples are wind speeds at rotor heights of windmills or high frequency precipitation sums. NUKLEUS is a contribution to the German research program RegIKlim funded by the Federal Ministry of Education and Research (BMBF).</p>

The Impact of Mixed-Phase Microphysical Processes on the Turbulence in Low-level Clouds in the Arctic

2021 ◽  
Author(s):  
Jan Chylik ◽  
Roel Neggers
Keyword(s):  
Boundary Layer ◽  
Climate Models ◽  
Weather Forecast ◽  
Mixed Phase ◽  
The Arctic ◽  
Contributing Factors ◽  
Microphysics Scheme ◽  
Low Level ◽  
Microphysical Processes ◽  
The Impact

<p>The proper representation of Arctic mixed-phased clouds remains a challenge in both weather forecast and climate models. Amongst the contributing factors is the complexity of turbulent properties of clouds. While the effect of evaporating hydrometeors on turbulent properties of the boundary layer has been identified in other latitudes, the extent of similar studies in the Arctic has been so far limited.</p><p>Our study focus on the impact of heat release from mixed-phase microphysical processes on the turbulent properties of the convective low-level clouds in the Arctic. We  employ high-resolution simulations, properly constrained by relevant measurements.<br>Semi-idealised model cases are based on convective clouds observed during the recent campaign in the Arctic: ACLOUD, which took place May--June 2017 over Fram Strait. The simulations are performed in Dutch Atmospheric Large Eddy Simulation (DALES) with double-moment mixed-phase microphysics scheme of Seifert & Beheng.</p><p>The results indicate an enhancement of boundary layer turbulence is some convective regimes.<br>Furthermore, results are sensitive to aerosols concentrations. Additional implications for the role of mixed-phase clouds in the Arctic Amplification will be discussed.</p>

scholarly journals Economics of the disintegration of the Greenland ice sheet

2019 ◽  
Vol 116 (25) ◽  
pp. 12261-12269 ◽  
Author(s):  
William Nordhaus
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Social Cost ◽  
Climate Models ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Reduced Form ◽  
Small Contribution ◽  
Wide Range ◽  
The Impact

Concerns about the impact on large-scale earth systems have taken center stage in the scientific and economic analysis of climate change. The present study analyzes the economic impact of a potential disintegration of the Greenland ice sheet (GIS). The study introduces an approach that combines long-run economic growth models, climate models, and reduced-form GIS models. The study demonstrates that social cost–benefit analysis and damage-limiting strategies can be usefully extended to illuminate issues with major long-term consequences, as well as concerns such as potential tipping points, irreversibility, and hysteresis. A key finding is that, under a wide range of assumptions, the risk of GIS disintegration makes a small contribution to the optimal stringency of current policy or to the overall social cost of climate change. It finds that the cost of GIS disintegration adds less than 5% to the social cost of carbon (SCC) under alternative discount rates and estimates of the GIS dynamics.

scholarly journals Linking the uncertainty in simulated arctic ozone losses to modelling of tropical stratospheric water vapour

2018 ◽  
Author(s):  
Laura Thölix ◽  
Alexey Karpechko ◽  
Leif Backman ◽  
Rigel Kivi
Keyword(s):  
Water Vapour ◽  
Climate Models ◽  
Polar Vortex ◽  
The Arctic ◽  
Ozone Loss ◽  
Tropical Tropopause ◽  
Water Vapour Concentration ◽  
Vapour Concentration ◽  
The Impact ◽  
Stratospheric Water Vapour

Abstract. Stratospheric water vapor plays a key role in radiative and chemical processes, it e.g. influences the chemical ozone loss via controlling the polar stratospheric cloud formation in the polar stratosphere. The amount of water entering the stratosphere through the tropical tropopause differs substantially between chemistry-climate models. This is because the present-day models have difficulties in capturing the whole complexity of processes that control the water transport across the tropopause. As a result there are large differences in the stratospheric water vapour between the models. In this study we investigate the sensitivity of simulated Arctic ozone loss to the amount of water, which enters the stratosphere through the tropical tropopause. We used a chemical transport model, FinROSE-CTM, forced by ERA-Interim meteorology. The water vapour concentration in the tropical tropopause was varied between 0.5 and 1.6 times the concentration in ERA-Interim, which is similar to the range seen in chemistry climate models. The water vapour changes in the tropical tropopause led to about 1.5 and 2 ppm more water vapour in the Arctic polar vortex compared to the ERA-Interim, respectively. We found that the impact of water vapour changes on ozone loss in the Arctic polar vortex depend on the meteorological conditions. Polar stratospheric clouds form in the cold conditions within the Arctic vortex, and chlorine activation on their surface lead to ozone loss. If the cold conditions persist long enough (e.g. in 2010/11), the chlorine activation is nearly complete. In this case addition of water vapour to the stratosphere increased the formation of ICE clouds, but did not increase the chlorine activation and ozone destruction significantly. In the warm winter 2012/13 the impact of water vapour concentration on ozone loss was small, because the ozone loss was mainly NOx induced. In intermediately cold conditions, e.g. 2013/14, the effect of added water vapour was more prominent than in the other studied winters. The results show that the simulated water vapour concentration in the tropical tropopause has a significant impact on the Arctic ozone loss and deserves attention in order to improve future projections of ozone layer recovery.

Sea-ice algal phenology in a warmer Arctic

2020 ◽  
Author(s):  
Letizia Tedesco ◽  
Marcello Vichi ◽  
Enrico Scoccimarro
Keyword(s):  
Sea Ice ◽  
Algal Blooms ◽  
Climate Models ◽  
Time Windows ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Biological Time ◽  
Algal Productivity ◽  
The Impact

<p>The Arctic sea-ice decline is among the most emblematic manifestations of climate change and is occurring before we understand its ecological consequences. We investigated future changes in algal productivity combining a biogeochemical model for sympagic algae with sea-ice drivers from an ensemble of 18 CMIP5 climate models. Model projections indicate quasi-linear physical changes along latitudes but markedly nonlinear response of sympagic algae, with distinct latitudinal patterns. While snow cover thinning explains the advancement of algal blooms below 66°N, narrowing of the biological time windows yields small changes in the 66°N to 74°N band, and shifting of the ice seasons toward more favorable photoperiods drives the increase in algal production above 74°N. These diverse latitudinal responses indicate that the impact of declining sea ice on Arctic sympagic production is both large and complex, with consequent trophic and phenological cascades expected in the rest of the food web.</p>

scholarly journals Computation of extreme heat waves in climate models using a large deviation algorithm

2017 ◽  
Vol 115 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Francesco Ragone ◽  
Jeroen Wouters ◽  
Freddy Bouchet
Keyword(s):  
Statistical Physics ◽  
Climate Models ◽  
Large Deviation ◽  
Heat Waves ◽  
Rare Event ◽  
Teleconnection Pattern ◽  
Extreme Heat ◽  
Sampling Efficiency ◽  
Wide Range ◽  
The Impact

Studying extreme events and how they evolve in a changing climate is one of the most important current scientific challenges. Starting from complex climate models, a key difficulty is to be able to run long enough simulations to observe those extremely rare events. In physics, chemistry, and biology, rare event algorithms have recently been developed to compute probabilities of events that cannot be observed in direct numerical simulations. Here we propose such an algorithm, specifically designed for extreme heat or cold waves, based on statistical physics. This approach gives an improvement of more than two orders of magnitude in the sampling efficiency. We describe the dynamics of events that would not be observed otherwise. We show that European extreme heat waves are related to a global teleconnection pattern involving North America and Asia. This tool opens up a wide range of possible studies to quantitatively assess the impact of climate change.

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