scholarly journals Seasonal Predictability of Extratropical Storm Tracks in GFDL’s High-Resolution Climate Prediction Model

2015 ◽  
Vol 28 (9) ◽  
pp. 3592-3611 ◽  
Author(s):  
Xiaosong Yang ◽  
Gabriel A. Vecchi ◽  
Rich G. Gudgel ◽  
Thomas L. Delworth ◽  
Shaoqing Zhang ◽  
...  
Keyword(s):  
High Resolution ◽  
Radiative Forcing ◽  
Climate Model ◽  
Storm Track ◽  
Storm Tracks ◽  
Boreal Winter ◽  
Seasonal Predictability ◽  
Coupled Models ◽  
Sea Level Pressure ◽  
Statistics Of Extremes

Abstract The seasonal predictability of extratropical storm tracks in the Geophysical Fluid Dynamics Laboratory’s (GFDL)’s high-resolution climate model has been investigated using an average predictability time analysis. The leading predictable components of extratropical storm tracks are the ENSO-related spatial patterns for both boreal winter and summer, and the second predictable components are mostly due to changes in external radiative forcing and multidecadal oceanic variability. These two predictable components for both seasons show significant correlation skill for all leads from 0 to 9 months, while the skill of predicting the boreal winter storm track is consistently higher than that of the austral winter. The predictable components of extratropical storm tracks are dynamically consistent with the predictable components of the upper troposphere jet flow for both seasons. Over the region with strong storm-track signals in North America, the model is able to predict the changes in statistics of extremes connected to storm-track changes (e.g., extreme low and high sea level pressure and extreme 2-m air temperature) in response to different ENSO phases. These results point toward the possibility of providing skillful seasonal predictions of the statistics of extratropical extremes over land using high-resolution coupled models.

Using PRIMAVERA high-resolution global climate models for European windstorm risk assessment in present and future climates for the (re)insurance industry

2020 ◽  
Author(s):  
Julia Lockwood ◽  
Erika Palin ◽  
Galina Guentchev ◽  
Malcolm Roberts
Keyword(s):  
High Resolution ◽  
Climate Models ◽  
Climate Model ◽  
Insurance Industry ◽  
Global Climate ◽  
Storm Track ◽  
Global Climate Models ◽  
Climate Modelling ◽  
Business And Society ◽  
High Resolution Models

<p>PRIMAVERA is a European Union Horizon2020 project about creating a new generation of advanced and well-evaluated high-resolution global climate models, for the benefit of governments, business and society in general. The project has been engaging with several sectors, including finance, transport, and energy, to understand the extent to which any improved process understanding arising from high-resolution global climate modelling can – in turn – help with using climate model output to address user needs.</p><p>In this talk we will outline our work for the finance and (re)insurance industries.  Following consultation with members of the industry, we are using PRIMAVERA climate models to generate a European windstorm event set for use in catastrophe modelling and risk analysis.  The event set is generated from five different climate models, each run at a selection of resolutions ranging from 18-140km, covering the period 1950-2050, giving approximately 1700 years of climate model data in total.  High-resolution climate models tend to have reduced biases in storm track position (which is too zonal in low-resolution climate models) and windstorm intensity.  We will compare the properties of the windstorm footprints and associated risk across the different models and resolutions, to assess whether the high-resolution models lead to improved estimation of European windstorm risk.  We will also compare windstorm risk in present and future climates, to see if a consistent picture emerges between models.  Finally we will address the question of whether the event sets from each PRIMAVERA model can be combined to form a multi-model event set ensemble covering thousands of years of windstorm data.</p>

scholarly journals Coupling aerosols to (cirrus) clouds in the global EMAC-MADE3 aerosol–climate model

2020 ◽  
Vol 13 (3) ◽  
pp. 1635-1661 ◽  
Author(s):  
Mattia Righi ◽  
Johannes Hendricks ◽  
Ulrike Lohmann ◽  
Christof Gerhard Beer ◽  
Valerian Hahn ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Climate Model ◽  
Cloud Droplet ◽  
Cirrus Clouds ◽  
Liquid Water Path ◽  
Coupled Models ◽  
Anthropogenic Aerosol ◽  
Intergovernmental Panel ◽  
New Model

Abstract. A new cloud microphysical scheme including a detailed parameterization for aerosol-driven ice formation in cirrus clouds is implemented in the global ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry–climate model and coupled to the third generation of the Modal Aerosol Dynamics model for Europe adapted for global applications (MADE3) aerosol submodel. The new scheme is able to consistently simulate three regimes of stratiform clouds – liquid, mixed-, and ice-phase (cirrus) clouds – considering the activation of aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is also performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the Northern Hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extratropical regions), which are both a common problem in these kinds of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling but within the range reported in the Intergovernmental Panel on Climate Change (IPCC) assessments.

scholarly journals The North Atlantic variability structure, storm tracks, and precipitation depending on the polar vortex strength

2005 ◽  
Vol 5 (1) ◽  
pp. 239-248 ◽  
Author(s):  
K. Walter ◽  
H.-F. Graf
Keyword(s):  
North Atlantic ◽  
Storm Track ◽  
Polar Vortex ◽  
The State ◽  
Storm Tracks ◽  
The Arctic ◽  
Boreal Winter ◽  
Vortex Strength ◽  
The North ◽  
The North Atlantic

Abstract. Motivated by the strong evidence that the state of the northern hemisphere vortex in boreal winter influences tropospheric variability, teleconnection patterns over the North Atlantic are defined separately for winter episodes where the zonal wind at 50hPa and 65° N is above or below the critical velocity for vertical propagation of zonal planetary wave 1. We argue that the teleconnection structure in the middle and upper troposphere differs considerably between the two regimes of the polar vortex, while this is not the case at sea level. If the polar vortex is strong, there exists one meridional dipole structure of geopotential height in the upper and middle troposphere, which is situated in the central North Atlantic. If the polar vortex is weak, there exist two such dipoles, one over the western and one over the eastern North Atlantic. Storm tracks (and precipitation related with these) are determined by mid and upper tropospheric conditions and we find significant differences of these parameters between the stratospheric regimes. For the strong polar vortex regime, in case of a negative upper tropospheric "NAO" index we find a blocking height situation over the Northeast Atlantic and the strongest storm track of all. It is reaching far north into the Arctic Ocean and has a secondary maximum over the Denmark Strait. Such storm track is not found in composites based on a classic NAO defined by surface pressure differences between the Icelandic Low and the Azores High. Our results suggest that it is important to include the state of the polar vortex strength in any study of the variability over the North Atlantic.

scholarly journals The Effect of Ocean Dynamics and Orography on Atmospheric Storm Tracks

2009 ◽  
Vol 22 (13) ◽  
pp. 3689-3702 ◽  
Author(s):  
Chris Wilson ◽  
Bablu Sinha ◽  
Richard G. Williams
Keyword(s):  
Heat Transport ◽  
Climate Model ◽  
Wave Train ◽  
Storm Track ◽  
Ocean Dynamics ◽  
Storm Tracks ◽  
The Tibetan Plateau ◽  
Poleward Shift ◽  
Orographic Forcing ◽  
Hemisphere Winter

Abstract The control of atmospheric storm tracks by ocean dynamics, orography, and their interaction is investigated using idealized experiments with a simplified coupled atmosphere–ocean climate model. The study focuses on the quasi–steady state for the storm tracks in the Northern Hemisphere winter mean. The experiments start with a background state without mountains and ocean dynamics, and in separate stages include orography and a dynamic ocean to obtain a more realistic control simulation. The separate effects of ocean dynamics, orography, and their nonlinear interaction are identified for the storm tracks and the surface thermodynamic forcing over the ocean. The model study suggests that atmospheric storm tracks are a robust feature of the climate system, occurring at midlatitudes even if there is no orographic forcing or ocean heat transport. Ocean dynamics generally lead to a poleward shift in both the storm track and the maximum in atmospheric northward heat transport and induce a northeastward tilt over the Atlantic. This poleward shift is linked to the extra heat transport by the ocean and the tightening of sea surface temperature gradients on the western side of ocean basins. Orographic forcing causes along-track variability with a weakening of the storm track over the continents and induces a northeastward tilt over the western Pacific, which is associated with a stationary planetary wave train generated by the Tibetan Plateau. The interaction between ocean dynamics and orographic forcing plays a localized role, enhancing the contrast between the Atlantic and Pacific. Much of the response to the forcing is eddy mediated and transient eddies help to spread the influence of orographic and ocean forcing.

Storm track response to ocean fronts in a global high-resolution climate model

2013 ◽  
Vol 43 (3-4) ◽  
pp. 805-828 ◽  
Author(s):  
R. Justin Small ◽  
Robert A. Tomas ◽  
Frank O. Bryan
Keyword(s):  
High Resolution ◽  
Climate Model ◽  
Storm Track ◽  
Ocean Fronts

scholarly journals Storm Tracks and Climate Change

2006 ◽  
Vol 19 (15) ◽  
pp. 3518-3543 ◽  
Author(s):  
Lennart Bengtsson ◽  
Kevin I. Hodges ◽  
Erich Roeckner
Keyword(s):  
Climate Change ◽  
Southern Hemisphere ◽  
Climate Model ◽  
Storm Track ◽  
Future Climate ◽  
Eastern Pacific ◽  
Storm Tracks ◽  
Intergovernmental Panel ◽  
Atlantic Sector ◽  
Poleward Shift

Abstract Extratropical and tropical transient storm tracks are investigated from the perspective of feature tracking in the ECHAM5 coupled climate model for the current and a future climate scenario. The atmosphere-only part of the model, forced by observed boundary conditions, produces results that agree well with analyses from the 40-yr ECMWF Re-Analysis (ERA-40), including the distribution of storms as a function of maximum intensity. This provides the authors with confidence in the use of the model for the climate change experiments. The statistical distribution of storm intensities is virtually preserved under climate change using the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario until the end of this century. There are no indications in this study of more intense storms in the future climate, either in the Tropics or extratropics, but rather a minor reduction in the number of weaker storms. However, significant changes occur on a regional basis in the location and intensity of storm tracks. There is a clear poleward shift in the Southern Hemisphere with consequences of reduced precipitation for several areas, including southern Australia. Changes in the Northern Hemisphere are less distinct, but there are also indications of a poleward shift, a weakening of the Mediterranean storm track, and a strengthening of the storm track north of the British Isles. The tropical storm tracks undergo considerable changes including a weakening in the Atlantic sector and a strengthening and equatorward shift in the eastern Pacific. It is suggested that some of the changes, in particular the tropical ones, are due to an SST warming maximum in the eastern Pacific. The shift in the extratropical storm tracks is shown to be associated with changes in the zonal SST gradient in particular for the Southern Hemisphere.

scholarly journals The response of the Northern Hemisphere storm tracks and jetstreams to climate change in the CMIP3, CMIP5, and CMIP6 climate models

2020 ◽  
Author(s):  
Ben Harvey ◽  
Peter Cook ◽  
Len Shaffrey ◽  
Reinhard Schiemann
Keyword(s):  
Climate Change ◽  
Spatial Pattern ◽  
North Atlantic ◽  
Climate Models ◽  
Climate Model ◽  
Storm Track ◽  
Coupled Model ◽  
Storm Tracks ◽  
Cmip5 Models ◽  
Jet Streams

<p>Understanding and predicting how extratropical cyclones might respond to climate change is essential for assessing future weather risks and informing climate change adaptation strategies. Climate model simulations provide a vital component of this assessment, with the caveat that their representation of the present-day climate is adequate. In this study the representation of the NH storm tracks and jet streams and their responses to climate change are evaluated across the three major phases of the Coupled Model Intercomparison Project: CMIP3 (2007), CMIP5 (2012), and CMIP6 (2019). The aim is to quantity how present-day biases in the NH storm tracks and jet streams have evolved with model developments, and to further our understanding of their responses to climate change.</p><p>The spatial pattern of the present-day biases in CMIP3, CMIP5, and CMIP6 are similar. However, the magnitude of the biases in the CMIP6 models is substantially lower in the DJF North Atlantic storm track and jet stream than in the CMIP3 and CMIP5 models. In summer, the biases in the JJA North Atlantic and North Pacific storm tracks are also much reduced in the CMIP6 models. Despite this, the spatial pattern of the climate change response in the NH storm tracks and jet streams are similar across the CMIP3, CMIP5, and CMIP6 ensembles. The SSP2-4.5 scenario responses in the CMIP6 models are substantially larger than in the corresponding RCP4.5 CMIP5 models, consistent with the larger climate sensitivities of the CMIP6 models compared to CMIP5.</p>

scholarly journals The global impact of supersaturation in a coupled chemistry-climate model

2007 ◽  
Vol 7 (6) ◽  
pp. 1629-1643 ◽  
Author(s):  
A. Gettelman ◽  
D. E. Kinnison
Keyword(s):  
Water Vapor ◽  
Radiative Forcing ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Strong Impact ◽  
Small Component ◽  
Enhanced Production

Abstract. Ice supersaturation is important for understanding condensation in the upper troposphere. Many general circulation models however do not permit supersaturation. In this study, a coupled chemistry climate model, the Whole Atmosphere Community Climate Model (WACCM), is modified to include supersaturation for the ice phase. Rather than a study of a detailed parameterization of supersaturation, the study is intended as a sensitivity experiment, to understand the potential impact of supersaturation, and of expected changes to stratospheric water vapor, on climate and chemistry. High clouds decrease and water vapor in the stratosphere increases at a similar rate to the prescribed supersaturation (20% supersaturation increases water vapor by nearly 20%). The stratospheric Brewer-Dobson circulation slows at high southern latitudes, consistent with slight changes in temperature likely induced by changes to cloud radiative forcing. The cloud changes also cause an increase in the seasonal cycle of near tropopause temperatures, increasing them in boreal summer over boreal winter. There are also impacts on chemistry, with small increases in ozone in the tropical lower stratosphere driven by enhanced production. The radiative impact of changing water vapor is dominated by the reduction in cloud forcing associated with fewer clouds (~+0.6 Wm−2) with a small component likely from the radiative effect (greenhouse trapping) of the extra water vapor (~+0.2 Wm−2), consistent with previous work. Representing supersaturation is thus important, and changes to supersaturation resulting from changes in aerosol loading for example, might have a modest impact on global radiative forcing, mostly through changes to clouds. There is no evidence of a strong impact of water vapor on tropical tropopause temperatures.

scholarly journals Reconstruction of high resolution atmospheric fields for Northern Europe using analog-upscaling

2012 ◽  
Vol 8 (5) ◽  
pp. 1681-1703 ◽  
Author(s):  
F. Schenk ◽  
E. Zorita
Keyword(s):  
High Resolution ◽  
Sea Level ◽  
Climate Model ◽  
Regional Climate ◽  
Low Frequency ◽  
Climate Simulation ◽  
Northern Europe ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Realistic Situation

Abstract. The analog method (AM) has found application to reconstruct gridded climate fields from the information provided by proxy data and climate model simulations. Here, we test the skill of different setups of the AM, in a controlled but realistic situation, by analysing several statistical properties of reconstructed daily high-resolution atmospheric fields for Northern Europe for a 50-yr period. In this application, station observations of sea-level pressure and air temperature are combined with atmospheric fields from a 50-yr high-resolution regional climate simulation. This reconstruction aims at providing homogeneous and physically consistent atmospheric fields with daily resolution suitable to drive high resolution ocean and ecosystem models. Different settings of the AM are evaluated in this study for the period 1958–2007 to estimate the robustness of the reconstruction and its ability to replicate high and low-frequency variability, realistic probability distributions and extremes of different meteorological variables. It is shown that the AM can realistically reconstruct variables with a strong physical link to daily sea-level pressure on both a daily and monthly scale. However, to reconstruct low-frequency decadal and longer temperature variations, additional monthly mean station temperature as predictor is required. Our results suggest that the AM is a suitable upscaling tool to predict daily fields taken from regional climate simulations based on sparse historical station data.

scholarly journals Impacts of North Pacific Subtropical and Subarctic Oceanic Frontal Zones on the Wintertime Atmospheric Large-Scale Circulations

2020 ◽  
Vol 33 (5) ◽  
pp. 1897-1914 ◽  
Author(s):  
Jing Huang ◽  
Yang Zhang ◽  
Xiu-Qun Yang ◽  
Xuejuan Ren ◽  
Haibo Hu
Keyword(s):  
High Resolution ◽  
North Pacific ◽  
Large Scale ◽  
Diabatic Heating ◽  
Climate Model ◽  
Frontal Zone ◽  
Regional Climate ◽  
Storm Track ◽  
Atmospheric Circulations ◽  
The North

AbstractAn oceanic frontal zone is a confluent region of warm and cool ocean currents, characterized by a strong meridional gradient of sea surface temperature (SST). High-resolution SST observations show that the wintertime North Pacific exhibits a unique double-oceanic-front structure, with a subtropical frontal zone (STFZ) and a subarctic frontal zone (SAFZ), whose impacts on the weather and climate over the East Asia–North Pacific–North American region need further investigation. In this study, we conduct groups of multiyear and ensemble simulations using a WRF high-resolution regional climate model, through which the different impacts of the STFZ and SAFZ on the wintertime atmospheric circulations are identified and compared. Our multiyear simulations show that the STFZ, although with weaker intensity, exerts evident and consistent impacts on the storm track and westerly jet in the North Pacific by enhancing and elongating the eddy activity, zonal wind, and Aleutian low. The SAFZ exhibits coherent impacts on the low-level atmospheric baroclinicity and storm track; however, its impacts on the upper-level storm track and atmospheric circulations are divergent, exhibiting strong year-by-year difference. Our study suggests that the SAFZ’s impacts on the atmospheric circulations strongly depend on the background mean state, which contributes to the divergent impacts of the SAFZ. Furthermore, our results highlight the role of diabatic heating for the above different impacts of the STFZ and SAFZ on the atmosphere. We argue that the much deeper diabatic heating induced by the STFZ, via affecting the baroclinicity through the whole troposphere, can exert consistent influence on eddy activities and atmospheric circulations.

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