A different perspective on how parameterized orographic gravity waves influence atmospheric transport and dynamics in current generation global climate models

2020 ◽  
Author(s):  
Harald Rieder ◽  
Petr Šácha ◽  
Roland Eichinger ◽  
Aleš Kuchař ◽  
Nadja Samtleben ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Climate Models ◽  
Atmospheric Transport ◽  
Global Climate ◽  
Internal Gravity Waves ◽  
Global Climate Models ◽  
Current Generation ◽  
The Individual ◽  
The Impact

<p>In the atmosphere, internal gravity waves (GWs) are a naturally occurring and ubiquitous, though intermittent phenomenon. In addition, GWs (especially orographic; OGWs) are asymmetrically distributed around the globe. In current generation global climate models (GCMs), GWs are usually smaller than the model grid resolution and the majority of their spectrum therefore must be parameterized. To some extent, the intermittency and asymmetry of a spatial distribution of the resulting OGW drag (OGWD) is present also in GCMs. As the GW parameterization schemes in GCMs are usually tuned to get the zonal mean climatology of particular features right, an important question emerges: what kind of influence do GW parameterizations have on the individual models atmosphere locally? Here we focus on answering this question regarding the impact of spatiotemporally intermittent OGW forcing in the extra-tropical lower stratosphere region (LS). The LS region is characterized by a strong interplay of chemical, physical and dynamical processes. To date, the representation of this dynamically active region in models frequently mismatches observations. Although we can find a climatological maximum of oGWD in the LS, the role of OGW forcing for the transport and composition in this region is poorly understood. We combine observational evidence, idealized modeling and statistical analysis of GCM outputs to study both the short-term and long-term model response to the OGW forcing. The results presented will question the relationship between the advective part of the Brewer- Dobson circulation and the zonally asymmetric GW forcing, and a so-far neglected link between oGWD and large-scale quasi-isentropic stirring will be discussed.</p>

Seasonal modulation of trapped gravity waves and their imprints on trade wind clouds

2020 ◽  
Author(s):  
Claudia Stephan
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Wave Theory ◽  
Internal Gravity Waves ◽  
Global Climate Models ◽  
Trade Wind ◽  
Trapped Waves ◽  
Convective Boundary

<p>Idealized simulations have shown decades ago that shallow clouds generate internal gravity waves, which under certain atmospheric background conditions become trapped inside the troposphere and influence the development of clouds. These feedbacks, which occur at horizontal scales of up to several tens of km are neither resolved, nor parameterized in traditional global climate models (GCMs), while the newest generation of GCMs is starting to resolve them. The interactions between the convective boundary layer and trapped waves have almost exclusively been studied in highly idealized frameworks and it remains unclear to what degree this coupling affects the organization of clouds and convection in the real atmosphere. Here, the coupling between clouds and trapped waves is examined in storm-resolving simulations that span the entirety of the tropical Atlantic and are initialized and forced by meteorological analyses. The coupling between clouds and trapped waves is sufficiently strong to be detected in these simulations of full complexity.  Stronger upper-tropospheric westerly winds are associated with a stronger cloud-wave coupling. In the simulations this results in a highly-organized scattered cloud field with cloud spacings of about 19 km, matching the dominant trapped wavelength. Based on the large-scale atmospheric state wave theory can reliably predict the regions and times where cloud-wave feedbacks become relevant to convective organization. Theory, the simulations and satellite imagery imply a seasonal cycle in the trapping of gravity waves. </p>

scholarly journals Summer Season Squall-Line Simulations: Sensitivity of Gravity Waves to Physics Parameterization and Implications for Their Parameterization in Global Climate Models

2014 ◽  
Vol 71 (9) ◽  
pp. 3376-3391 ◽  
Author(s):  
Claudia Stephan ◽  
M. Joan Alexander
Keyword(s):  
Gravity Waves ◽  
Momentum Flux ◽  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Global Climate ◽  
Global Climate Models ◽  
Squall Line ◽  
The Impact

Abstract Gravity waves have important effects on the middle atmosphere circulation, and those generated by convection are prevalent in the tropics and summer midlatitudes. Numerous case studies have been carried out to investigate their characteristics in high-resolution simulations. Here, the impact of the choice of physics parameterizations on the generation and spectral properties of these waves in models is investigated. Using the Weather Research and Forecasting Model (WRF) a summertime squall line over the Great Plains is simulated in a three-dimensional, nonlinear, and nonhydrostatic mesoscale framework. The distributions of precipitation strength and echo tops in the simulations are compared with radar data. Unsurprisingly, those storm features are most sensitive to the microphysics scheme. However, it is found that these variations in storm morphology have little influence on the simulated stratospheric momentum flux spectra. These results support the fundamental idea behind climate model parameterizations: that the large-scale storm conditions can be used to predict the spectrum of gravity wave momentum flux above the storm irrespective of the convective details that coarse-resolution models cannot capture. The simulated spectra are then contrasted with those obtained from a parameterization used in global climate models. The parameterization reproduces the shape of the spectra reasonably well but their magnitudes remain highly sensitive to the peak heating rate within the convective cells.

Assessing the effects of climate change on US West Coast sablefish productivity and on the performance of alternative management strategies

2019 ◽  
Vol 76 (6) ◽  
pp. 1524-1542
Author(s):  
Melissa A Haltuch ◽  
Z Teresa A’mar ◽  
Nicholas A Bond ◽  
Juan L Valero
Keyword(s):  
Climate Change ◽  
West Coast ◽  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Management Strategies ◽  
Climate Impacts ◽  
Global Climate Models ◽  
The Impact ◽  
Us West

Abstract US West Coast sablefish are economically valuable, with landings of 11.8 million pounds valued at over $31 million during 2016, making assessing and understanding the impact of climate change on the California Current (CC) stock a priority for (1) forecasting future stock productivity, and (2) testing the robustness of management strategies to climate impacts. Sablefish recruitment is related to large-scale climate forcing indexed by regionally correlated sea level (SL) and zooplankton communities that pelagic young-of-the-year sablefish feed upon. This study forecasts trends in future sablefish productivity using SL from Global Climate Models (GCMs) and explores the robustness of harvest control rules (HCRs) to climate driven changes in recruitment using management strategy evaluation (MSE). Future sablefish recruitment is likely to be similar to historical recruitment but may be less variable. Most GCMs suggest that decadal SL trends result in recruitments persisting at lower levels through about 2040 followed by higher levels that are more favorable for sablefish recruitment through 2060. Although this MSE suggests that spawning biomass and catches will decline, and then stabilize, into the future under both HCRs, the sablefish stock does not fall below the stock size that leads to fishery closures.

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.

scholarly journals The impact of precipitation evaporation on the atmospheric aerosol distribution in EC-Earth v3.2.0

2017 ◽  
Author(s):  
Marco de Bruine ◽  
Maarten Krol ◽  
Twan van Noije ◽  
Philippe Le Sager ◽  
Thomas Röckmann
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Earth Model ◽  
Climate Projections ◽  
Cloud Processing ◽  
Aerosol Distribution ◽  
Considerable Impact ◽  
The Impact

Abstract. The representation of aerosol-cloud interaction in global climate models (GCMs) remains a large source of uncertainty in climate projections. Due to its complexity, precipitation evaporation is either ignored or taken into account in a simplified manner in GCMs. This research explores various ways to treat aerosol resuspension and determines the possible impact of precipitation evaporation and subsequent aerosol resuspension on global aerosol burdens and distribution. The representation of wet deposition of aerosols by large-scale precipitation in the EC-Earth model has been improved by utilising additional precipitation related 3-D fields from the dynamical core IFS in the chemistry and aerosol module TM5. A simple approach of scaling aerosol release with evaporated precipitation fraction leads to an increase in the global aerosol burden (+7.8 to +15 %, for different aerosol species). However, when taking into account the different sizes and evaporation rate of raindrops following Gong et al. (2006), the release of aerosols is strongly reduced, and the total aerosol burden decreases by −3.0 to −8.5 %. Moreover, inclusion of cloud processing based on observations by Mitra et al. (1992) transforms scavenged small aerosol to coarse particles, which enhances removal by sedimentation and hence leads to a lower burden of small size aerosol by −10 to −11 %. Finally, when these two effects are combined the global aerosol burden decreases by −11 to −19 %. Compared to MODIS satellite observations, AOD is generally underestimated in most parts of the world in all model set-ups and although the representation is now physically more realistic, global AOD shows no large improvements in spatial patterns. Similarly, the agreement of the vertical profile with CALIOP satellite measurements does not improve significantly. However, aerosol resuspension after precipitation evaporation has a considerable impact on the modelled aerosol distribution and needs to be taken into account.

Impact of large-scale future floods on the railway system

2020 ◽  
Author(s):  
Weiping Wang ◽  
Saini Yang ◽  
Huijun Sun ◽  
Jianjun Wu ◽  
Jianxi Gao
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Negative Impact ◽  
Global Climate ◽  
Global Climate Models ◽  
Policy Implications ◽  
Transport Sector ◽  
Railway Network ◽  
Railway System ◽  
The Impact

&lt;p&gt;Increasing flood risk was caused by expanding climate change. The floods directly or indirectly disrupt the railway system and arise a significant negative impact on our social-economic system. This study developed an integrated approach to explore the impact of large-scale future floods on railway system. Firstly, A three layered traffic flow simulation model was constructed to study propagation and amplification effects of component failure after the event of flooding in the system. Secondly, future runoff scenarios were produced by using five global climate models and three different representative concentration pathways. The future floods was simulated by using CaMa-Flood model after inputting future runoff scenarios. Furthermore, we imposing simulated future floods into traffic simulation system and develop two measurements to evaluate the impact of floods on the railway system as the perspective of the entire system. Here we explore the impact of floods on the real-world highway network of China. The results illustrate that: (i) &lt;strong&gt;Unprecedented uncertainty&lt;/strong&gt;. The damage of the flood to the railway system is not linearly and positively correlated with representative concentration pathway and the year within different global climate models; Floods in different years have different impacts in connections among regions; (ii) &lt;strong&gt;Unacceptable damage&lt;/strong&gt;. 59.76 % of railway segments inundated and 98.61461% of large cities could not be reached by extreme floods. These results have critical policy implications for the transport sector in reference to railway location and design, railway network optimization and protection and can be also easily adapted to analyze other spatial damages for valuable protection suggestions.&lt;/p&gt;

scholarly journals Seasonal Modulation of Trapped Gravity Waves and Their Imprints on Trade Wind Clouds

2020 ◽  
Vol 77 (9) ◽  
pp. 2993-3009
Author(s):  
Claudia Christine Stephan
Keyword(s):  
Gravity Waves ◽  
Large Scale ◽  
Climate Models ◽  
Internal Gravity Waves ◽  
Global Climate Models ◽  
Trade Wind ◽  
Climate Projections ◽  
Shallow Convection ◽  
Trapped Waves ◽  
Convective Boundary

Abstract Shallow convection over the oceans is responsible for the largest uncertainties in climate projections. Idealized simulations have shown decades ago that shallow clouds generate internal gravity waves, which under certain atmospheric background conditions become trapped inside the troposphere and influence the development of clouds. These feedbacks, which occur at horizontal scales of up to several tens of kilometers. are neither resolved nor parameterized in traditional global climate models (GCMs), while the newest generation of GCMs (grid spacings &lt; 5 km) is starting to resolve them. The interactions between the convective boundary layer and trapped waves have almost exclusively been studied in highly idealized frameworks and it remains unclear to what degree this coupling affects the organization of clouds in the real atmosphere or in the new generation of GCMs. Here, the coupling between clouds and trapped waves is examined in 2.5-km simulations that span the entirety of the tropical Atlantic and are initialized and forced with meteorological analyses. The coupling between clouds and trapped waves is sufficiently strong to be detected in these simulations of full complexity. Stronger upper-tropospheric westerly winds are associated with a stronger cloud–wave coupling. In the simulations this results in a highly organized scattered cloud field with cloud spacings of about 19 km, matching the dominant trapped wavelength. Based on the large-scale atmospheric state, wave theory can reliably predict the regions and times where cloud–wave feedbacks become relevant to convective organization. Theory, the simulations, and satellite imagery imply a seasonal cycle in the trapping of gravity waves.

scholarly journals Risk for large-scale fires in boreal forests of Finland under changing climate

2015 ◽  
Vol 3 (8) ◽  
pp. 4753-4795
Author(s):  
I. Lehtonen ◽  
A. Venäläinen ◽  
M. Kämäräinen ◽  
H. Peltola ◽  
H. Gregow
Keyword(s):  
Forest Fires ◽  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Mapping Method ◽  
Global Climate Models ◽  
Burned Area ◽  
Fire Weather Index ◽  
Short Period ◽  
The Impact

Abstract. The target of this work was to assess the impact of projected climate change on the number of large forest fires (over 10 ha fires) and burned area in Finland. For this purpose, we utilized a strong relationship between fire occurrence and the Canadian fire weather index (FWI) during 1996–2014. We used daily data from five global climate models under representative concentration pathway RCP4.5 and RCP8.5 scenarios. The model data were statistically downscaled onto a high-resolution grid using the quantile-mapping method before performing the analysis. Our results suggest that the number of large forest fires may double or even triple during the present century. This would increase the risk that some of the fires could develop into real conflagrations which have become almost extinct in Finland due to active and efficient fire suppression. Our results also reveal substantial inter-model variability in the rate of the projected increase in forest-fire danger. We moreover showed that the majority of large fires occur within a relatively short period in May and June due to human activities and that FWI correlates poorer with the fire activity during this time of year than later in summer when lightning is more important cause of fires.

scholarly journals Global climatology and trends in convective environments from ERA5 and rawinsonde data

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mateusz Taszarek ◽  
John T. Allen ◽  
Mattia Marchio ◽  
Harold E. Brooks
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Global Climate ◽  
Convective Available Potential Energy ◽  
Global Climate Models ◽  
Convective Precipitation ◽  
The Past ◽  
The Tropics ◽  
Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

scholarly journals A new world natural vegetation map for global change studies

2008 ◽  
Vol 80 (2) ◽  
pp. 397-408 ◽  
Author(s):  
David M. Lapola ◽  
Marcos D. Oyama ◽  
Carlos A. Nobre ◽  
Gilvan Sampaio
Keyword(s):  
Large Scale ◽  
New World ◽  
Climate Models ◽  
Global Climate ◽  
Horizontal Resolution ◽  
Vegetation Classification ◽  
Natural Vegetation ◽  
Global Climate Models ◽  
Vegetation Map ◽  
Vegetation Maps

We developed a new world natural vegetation map at 1 degree horizontal resolution for use in global climate models. We used the Dorman and Sellers vegetation classification with inclusion of a new biome: tropical seasonal forest, which refers to both deciduous and semi-deciduous tropical forests. SSiB biogeophysical parameters values for this new biome type are presented. Under this new vegetation classification we obtained a consensus map between two global natural vegetation maps widely used in climate studies. We found that these two maps assign different biomes in ca. 1/3 of the continental grid points. To obtain a new global natural vegetation map, non-consensus areas were filled according to regional consensus based on more than 100 regional maps available on the internet. To minimize the risk of using poor quality information, the regional maps were obtained from reliable internet sources, and the filling procedure was based on the consensus among several regional maps obtained from independent sources. The new map was designed to reproduce accurately both the large-scale distribution of the main vegetation types (as it builds on two reliable global natural vegetation maps) and the regional details (as it is based on the consensus of regional maps).

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