Research article
16 Jun 2015
Research article
| 16 Jun 2015
Influence of along-valley terrain heterogeneity on exchange processes over idealized valleys
J. S. Wagner et al.
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M. N. Lang, A. Gohm, and J. S. Wagner
Atmos. Chem. Phys., 15, 11981–11998, https://doi.org/10.5194/acp-15-11981-2015, https://doi.org/10.5194/acp-15-11981-2015, 2015
Cornelius Immanuel Weiß, Alexander Gohm, Mathias Walter Rotach, and Thomas Torora Minda
Weather Clim. Dynam. Discuss., https://doi.org/10.5194/wcd-2022-20, https://doi.org/10.5194/wcd-2022-20, 2022
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Two gap flow events in the Great Rift Valley in Ethiopia were investigated with observations, ERA5 reanalysis data and simulations with the numerical weather prediction model WRF. The main focus was on strong winds in the area around Lake Abaya since the winds may generate waves on the lake which help to sustain the lakes ecology. That is important in terms of food supply for the local population. The gap winds exhibit a diurnal cycle and a seasonal dependence.
Manuel Saigger and Alexander Gohm
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In this work a special form of a foehn wind in an Alpine valley with a large-scale northwesterly flow is investigated. The study clarifies the origin of the air mass and the mechanisms by which this air enters the valley. A trajectory analysis shows that the location where the main airstream passes the crest line is more suitable for a foehn classification than the local or large-scale wind direction. Mountain waves and a lee rotor were crucial for importing air into the valley.
Matthias Göbel, Stefano Serafin, and Mathias W. Rotach
Geosci. Model Dev., 15, 669–681, https://doi.org/10.5194/gmd-15-669-2022, https://doi.org/10.5194/gmd-15-669-2022, 2022
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We present WRFlux, an open-source software that allows numerically consistent, time-averaged budget evaluation of prognostic variables for the numerical weather prediction model WRF as well as the transformation of the budget equations from the terrain-following grid of the model to the Cartesian coordinate system. We demonstrate the performance and a possible application of WRFlux and illustrate the detrimental effects of approximations that are inconsistent with the model numerics.
Hetal Dabhi, Mathias Rotach, and Michael Oberguggenberger
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High-resolution precipitation data consistent both in space and time for current and future climate are required for climate change impact assessments, but it is very challenging for complex topography. We present a model that generates synthetic gridded data of daily precipitation at 1 km spatial resolution using observed meteorological station data as input and provides data where historical observations are not available. We evaluate this model for a mountainous region in the European Alps.
Helen Claire Ward, Mathias Rotach, Alexander Gohm, Martin Graus, Thomas Karl, Maren Haid, Lukas Umek, and Thomas Muschinski
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This study examines how cities and their surroundings influence turbulent exchange processes responsible for weather and climate. Analysis of a four-year observational dataset for the Alpine city of Innsbruck reveals several similarities with other (flat) city-centre sites. However, the mountain setting leads to characteristic daily and seasonal flow patterns (‘valley winds’), and downslope windstorms that have a marked effect on temperature, wind speed, turbulence and pollutant concentration.
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Bettina Richter, Alec van Herwijnen, Mathias W. Rotach, and Jürg Schweizer
Nat. Hazards Earth Syst. Sci., 20, 2873–2888, https://doi.org/10.5194/nhess-20-2873-2020, https://doi.org/10.5194/nhess-20-2873-2020, 2020
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We investigated the sensitivity of modeled snow instability to uncertainties in meteorological input, typically found in complex terrain. The formation of the weak layer was very robust due to the long dry period, indicated by a widespread avalanche problem. Once a weak layer has formed, precipitation mostly determined slab and weak layer properties and hence snow instability. When spatially assessing snow instability for avalanche forecasting, accurate precipitation patterns have to be known.
Bettina Richter, Jürg Schweizer, Mathias W. Rotach, and Alec van Herwijnen
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Information on snow stability is important for avalanche forecasting. To improve the stability estimation in the snow cover model SNOWPACK, we suggested an improved parameterization for the critical crack length. We compared 3 years of field data to SNOWPACK simulations. The match between observed and modeled critical crack lengths greatly improved, and critical weak layers appear more prominently in the modeled vertical profile of critical crack length.
Christian Mallaun, Andreas Giez, Georg J. Mayr, and Mathias W. Rotach
Atmos. Chem. Phys., 19, 9769–9786, https://doi.org/10.5194/acp-19-9769-2019, https://doi.org/10.5194/acp-19-9769-2019, 2019
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This study presents airborne measurements in shallow convection over land to investigate the dynamic properties of clouds focusing on possible narrow downdraughts in the surrounding of the clouds. A characteristic narrow downdraught region (
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Johannes Horak, Marlis Hofer, Fabien Maussion, Ethan Gutmann, Alexander Gohm, and Mathias W. Rotach
Hydrol. Earth Syst. Sci., 23, 2715–2734, https://doi.org/10.5194/hess-23-2715-2019, https://doi.org/10.5194/hess-23-2715-2019, 2019
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This study presents an in-depth evaluation of the Intermediate Complexity Atmospheric Research (ICAR) model for high-resolution precipitation fields in complex topography. ICAR is evaluated with data from weather stations located in the Southern Alps of New Zealand. While ICAR underestimates rainfall amounts, it clearly improves over a coarser global model and shows potential to generate precipitation fields for long-term impact studies focused on the local impact of a changing global climate.
Daniel Leukauf, Alexander Gohm, and Mathias W. Rotach
Atmos. Chem. Phys., 16, 13049–13066, https://doi.org/10.5194/acp-16-13049-2016, https://doi.org/10.5194/acp-16-13049-2016, 2016
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Since populated valleys suffer often from poor air quality, it is of interest to better understand the various mechanisms relevant to remove pollutants from the valley atmosphere. One mechanism is the transport by along-slope flows, which are generated during fair-weather days. In this study we quantify the amount of tracer that is removed from a valley atmosphere and the amount that is re-circulated within the valleys. For this study we are using the numerical weather model WRF.
N. Kljun, P. Calanca, M. W. Rotach, and H. P. Schmid
Geosci. Model Dev., 8, 3695–3713, https://doi.org/10.5194/gmd-8-3695-2015, https://doi.org/10.5194/gmd-8-3695-2015, 2015
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Flux footprint models describe the surface area of influence of a flux measurement. They are used for designing flux tower sites, and for interpretation of flux measurements. The two-dimensional footprint parameterisation (FFP) presented here is suitable for processing large data sets, and, unlike other fast footprint models, FFP is applicable to daytime or night-time measurements, fluxes from short masts over grassland to tall towers over mature forests, and even to airborne flux measurements.
M. N. Lang, A. Gohm, and J. S. Wagner
Atmos. Chem. Phys., 15, 11981–11998, https://doi.org/10.5194/acp-15-11981-2015, https://doi.org/10.5194/acp-15-11981-2015, 2015
G. Massaro, I. Stiperski, B. Pospichal, and M. W. Rotach
Atmos. Meas. Tech., 8, 3355–3367, https://doi.org/10.5194/amt-8-3355-2015, https://doi.org/10.5194/amt-8-3355-2015, 2015
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Subject: Dynamics | Research Activity: Atmospheric Modelling | Altitude Range: Troposphere | Science Focus: Physics (physical properties and processes)
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Anna A. Shestakova, Dmitry G. Chechin, Christof Lüpkes, Jörg Hartmann, and Marion Maturilli
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Xiadong An, Lifang Sheng, Chun Li, Wen Chen, Yulian Tang, and Jingliang Huangfu
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Francisco J. Pérez-Invernón, Heidi Huntrieser, Sergio Soler, Francisco J. Gordillo-Vázquez, Nicolau Pineda, Javier Navarro-González, Víctor Reglero, Joan Montanyà, Oscar van der Velde, and Nikos Koutsias
Atmos. Chem. Phys., 21, 17529–17557, https://doi.org/10.5194/acp-21-17529-2021, https://doi.org/10.5194/acp-21-17529-2021, 2021
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Diego Aliaga, Victoria A. Sinclair, Marcos Andrade, Paulo Artaxo, Samara Carbone, Evgeny Kadantsev, Paolo Laj, Alfred Wiedensohler, Radovan Krejci, and Federico Bianchi
Atmos. Chem. Phys., 21, 16453–16477, https://doi.org/10.5194/acp-21-16453-2021, https://doi.org/10.5194/acp-21-16453-2021, 2021
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We investigate the origin of air masses sampled at Mount Chacaltaya, Bolivia. Three-quarters of the measured air has not been influenced by the surface in the previous 4 d. However, it is rare that, at any given time, the sampled air has not been influenced at all by the surface, and often the sampled air has multiple origins. The influence of the surface is more prevalent during day than night. Furthermore, during the 6-month study, one-third of the air masses originated from Amazonia.
Shipra Jain, Ruth M. Doherty, David Sexton, Steven Turnock, Chaofan Li, Zixuan Jia, Zongbo Shi, and Lin Pei
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-826, https://doi.org/10.5194/acp-2021-826, 2021
Revised manuscript accepted for ACP
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We provide a range of future projections of winter haze and clear conditions over the North China Plain (NCP) using multiple simulations from a climate model for the high-emission scenario (RCP8.5). The frequency of haze conducive weather is likely to increase whereas the frequency of clear weather is likely to decrease in future. The total number of hazy days for a given winter can be as much as ~3.5 times higher than the number of clear days over the NCP.
Michael Biggart, Jenny Stocker, Ruth M. Doherty, Oliver Wild, David Carruthers, Sue Grimmond, Yiqun Han, Pingqing Fu, and Simone Kotthaus
Atmos. Chem. Phys., 21, 13687–13711, https://doi.org/10.5194/acp-21-13687-2021, https://doi.org/10.5194/acp-21-13687-2021, 2021
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Heat-related illnesses are of increasing concern in China given its rapid urbanisation and our ever-warming climate. We examine the relative impacts that land surface properties and anthropogenic heat have on the urban heat island (UHI) in Beijing using ADMS-Urban. Air temperature measurements and satellite-derived land surface temperatures provide valuable means of evaluating modelled spatiotemporal variations. This work provides critical information for urban planners and UHI mitigation.
Tobias Wolf, Lasse H. Pettersson, and Igor Esau
Atmos. Chem. Phys., 21, 12463–12477, https://doi.org/10.5194/acp-21-12463-2021, https://doi.org/10.5194/acp-21-12463-2021, 2021
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House heating by wood-burning stoves is cozy and needed in boreal cities, e.g., Bergen, Norway. But smoke (aerosols) from stoves may reduce urban air quality. It can be transported over long distance excessively polluting some neighborhoods. Who will suffer the most? Our modelling study looks at urban pollution in unprecedented meter-sized details tracing smoke pathways and turbulent dispersion in a typical city. We prototype effective policy scenarios to mitigate urban air quality problems.
Piotr Sekuła, Anita Bokwa, Jakub Bartyzel, Bogdan Bochenek, Łukasz Chmura, Michał Gałkowski, and Mirosław Zimnoch
Atmos. Chem. Phys., 21, 12113–12139, https://doi.org/10.5194/acp-21-12113-2021, https://doi.org/10.5194/acp-21-12113-2021, 2021
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The wind shear generated on a local scale by the diversified relief’s impact can be a factor which significantly modifies the spatial pattern of PM10 concentration. The vertical profile of PM10 over a city located in a large valley during the events with high surface-level PM10 concentrations may show a sudden decrease with height not only due to the increase in wind speed, but also due to the change in wind direction alone. Vertical aerosanitary urban zones can be distinguished.
Jangho Lee, Jeffrey C. Mast, and Andrew E. Dessler
Atmos. Chem. Phys., 21, 11889–11904, https://doi.org/10.5194/acp-21-11889-2021, https://doi.org/10.5194/acp-21-11889-2021, 2021
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This paper investigates the impact of global warming on heat and humidity extremes. There are three major findings in this study. We quantify how unforced variability in the climate impacts can lead to large variations where heat waves occur, we find that all heat extremes increase as the climate warms, especially between 1.5 and 2.0 °C of the average global warming, and we show that the economic inequity of facing extreme heat will worsen in a warmer world.
Hyunju Jung, Ann Kristin Naumann, and Bjorn Stevens
Atmos. Chem. Phys., 21, 10337–10345, https://doi.org/10.5194/acp-21-10337-2021, https://doi.org/10.5194/acp-21-10337-2021, 2021
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We analyze the behavior of organized convection in a large-scale flow by imposing a mean flow to idealized simulations. In the mean flow, organized convection initially propagates slower than the mean wind speed and becomes stationary. The initial upstream and downstream difference in surface fluxes becomes symmetric as the surface momentum flux acts as a drag, resulting in the stationarity. Meanwhile, the surface enthalpy flux has a minor role in the propagation of the convection.
Xueling Liu, Arthur P. Mizzi, Jeffrey L. Anderson, Inez Fung, and Ronald C. Cohen
Atmos. Chem. Phys., 21, 9573–9583, https://doi.org/10.5194/acp-21-9573-2021, https://doi.org/10.5194/acp-21-9573-2021, 2021
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Observations of winds in the planetary boundary layer remain sparse, making it challenging to simulate and predict the atmospheric conditions that are most important for describing and predicting urban air quality. Here we investigate the application of data assimilation of NO2 columns as will be observed from geostationary orbit to improve predictions and retrospective analysis of wind fields in the boundary layer.
Annika Drews, Wenjuan Huo, Katja Matthes, Kunihiko Kodera, and Tim Kruschke
Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2021-241, https://doi.org/10.5194/acp-2021-241, 2021
Revised manuscript accepted for ACP
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Solar irradiance varies with a period of approximately 11 years. Using a unique large chemistry climate model dataset, we investigate the solar surface signal in the North Atlantic and European region, and find that changes over time, depending on the strength of the solar cycle. For the first time, we estimate the potential predictability associated with including realistic solar forcing in a model. These results may improve seasonal to decadal predictions of European climate.
Antara Banerjee, Amy H. Butler, Lorenzo M. Polvani, Alan Robock, Isla R. Simpson, and Lantao Sun
Atmos. Chem. Phys., 21, 6985–6997, https://doi.org/10.5194/acp-21-6985-2021, https://doi.org/10.5194/acp-21-6985-2021, 2021
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We find that simulated stratospheric sulfate geoengineering could lead to warmer Eurasian winters alongside a drier Mediterranean and wetting to the north. These effects occur due to the strengthening of the Northern Hemisphere stratospheric polar vortex, which shifts the North Atlantic Oscillation to a more positive phase. We find the effects in our simulations to be much more significant than the wintertime effects of large tropical volcanic eruptions which inject much less sulfate aerosol.
Ronny Badeke, Volker Matthias, and David Grawe
Atmos. Chem. Phys., 21, 5935–5951, https://doi.org/10.5194/acp-21-5935-2021, https://doi.org/10.5194/acp-21-5935-2021, 2021
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This work aims to describe the physical distribution of ship exhaust gases in the near field, e.g., inside of a harbor. Results were calculated with a mathematical model for different meteorological and technical conditions. It has been shown that large vessels like cruise ships have a significant effect of up to 55 % downward movement of exhaust gas, as they can disturb the ground near wind circulation. This needs to be considered in urban air pollution studies.
Taufiq Hassan, Robert J. Allen, Wei Liu, and Cynthia A. Randles
Atmos. Chem. Phys., 21, 5821–5846, https://doi.org/10.5194/acp-21-5821-2021, https://doi.org/10.5194/acp-21-5821-2021, 2021
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State-of-the-art climate models yield robust, externally forced changes in the Atlantic meridional overturning circulation (AMOC), the bulk of which are due to anthropogenic aerosol perturbations to net surface shortwave radiation and sea surface temperature. AMOC-related feedbacks act to reinforce this aerosol-forced response, largely due to changes in sea surface salinity (and hence sea surface density), with temperature- and cloud-related feedbacks acting to mute the initial response.
Jun-Ichi Yano and Nils P. Wedi
Atmos. Chem. Phys., 21, 4759–4778, https://doi.org/10.5194/acp-21-4759-2021, https://doi.org/10.5194/acp-21-4759-2021, 2021
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Sensitivities of forecasts of the Madden–Julian oscillation (MJO) to various different configurations of the physics are examined with the global model of ECMWF's Integrated Forecasting System (IFS). The motivation for the study was to simulate the MJO as a nonlinear free wave. To emulate free dynamics in the IFS,
various momentum dissipation terms (
friction) as well as diabatic heating were selectively turned off over the tropics for the range of the latitudes from 20° S to 20° N.
Peter Sherman, Meng Gao, Shaojie Song, Alex T. Archibald, Nathan Luke Abraham, Jean-François Lamarque, Drew Shindell, Gregory Faluvegi, and Michael B. McElroy
Atmos. Chem. Phys., 21, 3593–3605, https://doi.org/10.5194/acp-21-3593-2021, https://doi.org/10.5194/acp-21-3593-2021, 2021
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The aims here are to assess the role of aerosols in India's monsoon precipitation and to determine the relative contributions from Chinese and Indian emissions using CMIP6 models. We find that increased sulfur emissions reduce precipitation, which is primarily dynamically driven due to spatial shifts in convection over the region. A significant increase in precipitation (up to ~ 20 %) is found only when both Indian and Chinese sulfate emissions are regulated.
Melissa L. Breeden, Amy H. Butler, John R. Albers, Michael Sprenger, and Andrew O'Neil Langford
Atmos. Chem. Phys., 21, 2781–2794, https://doi.org/10.5194/acp-21-2781-2021, https://doi.org/10.5194/acp-21-2781-2021, 2021
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Prior research has found a maximum in deep stratosphere-to-troposphere mass/ozone transport over the western United States in boreal spring, which can enhance surface ozone concentrations, reducing air quality. We find that the winter-to-summer evolution of the north Pacific jet increases the frequency of stratospheric intrusions that drive transport, helping explain the observed maximum. The El Niño–Southern Oscillation affects the timing of the spring jet transition and therefore transport.
Dirk Offermann, Christoph Kalicinsky, Ralf Koppmann, and Johannes Wintel
Atmos. Chem. Phys., 21, 1593–1611, https://doi.org/10.5194/acp-21-1593-2021, https://doi.org/10.5194/acp-21-1593-2021, 2021
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Atmospheric oscillations with periods of up to several 100 years exist at altitudes up to 110 km. They are also seen in computer models (GCMs) of the atmospheric. They are often attributed to external influences from the sun, from the oceans, or from atmospheric constituents. This is difficult to verify as the atmosphere cannot be manipulated in an experiment. However, a GCM can be changed arbitrarily. Doing so, we find that long-period oscillations may be excited internally in the atmosphere.
Anna Shcherbacheva, Tracey Balehowsky, Jakub Kubečka, Tinja Olenius, Tapio Helin, Heikki Haario, Marko Laine, Theo Kurtén, and Hanna Vehkamäki
Atmos. Chem. Phys., 20, 15867–15906, https://doi.org/10.5194/acp-20-15867-2020, https://doi.org/10.5194/acp-20-15867-2020, 2020
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Atmospheric new particle formation and cluster growth to aerosol particles is an important field of research, in particular due to the climate change phenomenon. Evaporation rates are very difficult to account for but they are important to explain the formation and growth of particles. Different quantum chemistry (QC) methods produce substantially different values for the evaporation rates. We propose a novel approach for inferring evaporation rates of clusters from available measurements.
Jan Karlický, Peter Huszár, Tereza Nováková, Michal Belda, Filip Švábik, Jana Ďoubalová, and Tomáš Halenka
Atmos. Chem. Phys., 20, 15061–15077, https://doi.org/10.5194/acp-20-15061-2020, https://doi.org/10.5194/acp-20-15061-2020, 2020
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Cities are characterized by their impact on various meteorological variables. Our study aims to generalize these modifications into a single phenomenon – the urban meteorology island (UMI). A wide ensemble of Weather Research and Forecasting (WRF) and Regional Climate Model (RegCM) simulations investigated urban-induced modifications as individual UMI components. Significant changes are found in most of the discussed meteorological variables with a strong impact of specific model simulations.
William R. Hobbs, Andrew R. Klekociuk, and Yuhang Pan
Atmos. Chem. Phys., 20, 14757–14768, https://doi.org/10.5194/acp-20-14757-2020, https://doi.org/10.5194/acp-20-14757-2020, 2020
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Reanalysis products are an invaluable tool for representing variability and long-term trends in regions with limited in situ data. However, validation of these products is difficult because of that lack of station data. Here we present a novel assessment of eight reanalyses over the polar Southern Ocean, leveraging the close relationship between trends in sea ice cover and surface air temperature, that provides clear guidance on the most reliable product for Antarctic research.
Lejiang Yu, Shiyuan Zhong, Cuijuan Sui, and Bo Sun
Atmos. Chem. Phys., 20, 13753–13770, https://doi.org/10.5194/acp-20-13753-2020, https://doi.org/10.5194/acp-20-13753-2020, 2020
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The recent increasing trend of "warm Arctic, cold continents" has attracted much attention, but it remains debatable as to what forces are behind this phenomenon. Sea surface temperature (SST) over the central North Pacific and the North Atlantic oceans influences the trend. On an interdecadal timescale, the recent increase in the occurrences of the warm Arctic–cold Eurasia pattern is a fragment of the interdecadal variability of SST over the Atlantic Ocean and over the central Pacific Ocean.
Martina Krämer, Christian Rolf, Nicole Spelten, Armin Afchine, David Fahey, Eric Jensen, Sergey Khaykin, Thomas Kuhn, Paul Lawson, Alexey Lykov, Laura L. Pan, Martin Riese, Andrew Rollins, Fred Stroh, Troy Thornberry, Veronika Wolf, Sarah Woods, Peter Spichtinger, Johannes Quaas, and Odran Sourdeval
Atmos. Chem. Phys., 20, 12569–12608, https://doi.org/10.5194/acp-20-12569-2020, https://doi.org/10.5194/acp-20-12569-2020, 2020
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To improve the representations of cirrus clouds in climate predictions, extended knowledge of their properties and geographical distribution is required. This study presents extensive airborne in situ and satellite remote sensing climatologies of cirrus and humidity, which serve as a guide to cirrus clouds. Further, exemplary radiative characteristics of cirrus types and also in situ observations of tropical tropopause layer cirrus and humidity in the Asian monsoon anticyclone are shown.
Leenes Uzan, Smadar Egert, Pavel Khain, Yoav Levi, Elyakom Vadislavsky, and Pinhas Alpert
Atmos. Chem. Phys., 20, 12177–12192, https://doi.org/10.5194/acp-20-12177-2020, https://doi.org/10.5194/acp-20-12177-2020, 2020
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Detection of the planetary boundary layer (PBL) height is crucial to various fields, from air pollution assessment to weather prediction. We examined the diurnal summer PBL height by eight ceilometers in Israel, radiosonde profiles, the global IFS, and regional COSMO models. Our analysis utilized the bulk Richardson number method, the parcel method, and the wavelet covariance transform method. A novel correction tool to improve model results against in-situ ceilometer measurements is introduced.
Jessica Slater, Juha Tonttila, Gordon McFiggans, Paul Connolly, Sami Romakkaniemi, Thomas Kühn, and Hugh Coe
Atmos. Chem. Phys., 20, 11893–11906, https://doi.org/10.5194/acp-20-11893-2020, https://doi.org/10.5194/acp-20-11893-2020, 2020
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The feedback effect between aerosol particles, radiation and meteorology reduces turbulent motion and results in increased surface aerosol concentrations during Beijing haze. Observational analysis and regional modelling studies have examined the feedback effect but these studies are limited. In this work, we set up a high-resolution model for the Beijing environment to examine the sensitivity of the aerosol feedback effect to initial meteorological conditions and aerosol loading.
Bernard Legras and Silvia Bucci
Atmos. Chem. Phys., 20, 11045–11064, https://doi.org/10.5194/acp-20-11045-2020, https://doi.org/10.5194/acp-20-11045-2020, 2020
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The Asian monsoon is the most active region bringing surface compounds by convection to the stratosphere during summer. We study the transport pathways and the trapping within the upper-layer anticyclonic circulation. Above 15 km, the confinement can be represented by a uniform ascent over continental Asia of about 200 m per day and a uniform loss to other regions with a characteristic time of 2 weeks. We rule out the presence of a
chimneyproposed in previous studies over the Tibetan Plateau.
Clare Marie Flynn and Thorsten Mauritsen
Atmos. Chem. Phys., 20, 7829–7842, https://doi.org/10.5194/acp-20-7829-2020, https://doi.org/10.5194/acp-20-7829-2020, 2020
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The range of climate sensitivity of models participating in CMIP6 has increased relative to models participating in CMIP5 due to decreases in the total feedback parameter. This is caused by increases in the shortwave all-sky and clear-sky feedbacks, particularly over the Southern Ocean. These shifts between CMIP6 and CMIP5 did not arise by chance. Both CMIP5 and CMIP6 models are found to exhibit aerosol forcing that is too strong, causing too much cooling relative to observations.
Marie-Noëlle Bouin and Cindy Lebeaupin Brossier
Atmos. Chem. Phys., 20, 6861–6881, https://doi.org/10.5194/acp-20-6861-2020, https://doi.org/10.5194/acp-20-6861-2020, 2020
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A coupled, kilometre-scale simulation of a medicane is used to assess the impact of the ocean feedback and role of surface fluxes. Sea surface temperature (SST) drop is much weaker than for tropical cyclones, resulting in no impact on the cyclone. Surface fluxes depend mainly on wind and SST for evaporation and on air temperature for sensible heat. Processes in the Mediterranean, like advection of continental air, rain evaporation and dry air intrusion, play a role in cyclone development.
Kevin M. Grise and Sean M. Davis
Atmos. Chem. Phys., 20, 5249–5268, https://doi.org/10.5194/acp-20-5249-2020, https://doi.org/10.5194/acp-20-5249-2020, 2020
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As Earth's climate warms, the tropical overturning circulation (Hadley circulation) is projected to expand, potentially pushing subtropical dry zones further poleward. This study examines projections of the Hadley circulation from the latest generation of computer models and finds several notable differences from older models. For example, the Northern Hemisphere circulation has expanded northward at a greater rate in recent decades than would be expected from increasing greenhouse gases alone.
Yufei Zou, Yuhang Wang, Zuowei Xie, Hailong Wang, and Philip J. Rasch
Atmos. Chem. Phys., 20, 4999–5017, https://doi.org/10.5194/acp-20-4999-2020, https://doi.org/10.5194/acp-20-4999-2020, 2020
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We analyze the relationship between winter air stagnation and pollution extremes over eastern China and preceding Arctic sea ice loss based on climate modeling and dynamic diagnoses. We find significant increases in both the probability and intensity of air stagnation extremes in the modeling result driven by regional sea ice and sea surface temperature changes over the Pacific sector of the Arctic. We reveal the considerable impact of the Arctic climate change on mid-latitude weather extremes.
Dan Li, Bärbel Vogel, Rolf Müller, Jianchun Bian, Gebhard Günther, Felix Ploeger, Qian Li, Jinqiang Zhang, Zhixuan Bai, Holger Vömel, and Martin Riese
Atmos. Chem. Phys., 20, 4133–4152, https://doi.org/10.5194/acp-20-4133-2020, https://doi.org/10.5194/acp-20-4133-2020, 2020
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Low ozone and low water vapour signatures in the UTLS were investigated using balloon-borne measurements and trajectory calculations. The results show that deep convection in tropical cyclones over the western Pacific transports boundary air parcels with low ozone into the tropopause region. Subsequently, these air parcels are dehydrated when passing the lowest temperature region (< 190 K) during quasi-horizontal advection.
César Sauvage, Cindy Lebeaupin Brossier, Marie-Noëlle Bouin, and Véronique Ducrocq
Atmos. Chem. Phys., 20, 1675–1699, https://doi.org/10.5194/acp-20-1675-2020, https://doi.org/10.5194/acp-20-1675-2020, 2020
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Air–sea exchanges during Mediterranean heavy precipitation events are key and their representation must be improved for high-resolution weather forecasts. This study investigates the mechanisms acting at the air–sea interface during a case that occurred in southern France. To focus on the impact of sea state, we developed and used an original coupled air–wave model. Results show modifications of the forecast for the air–sea fluxes, the near-surface wind and the location of precipitation.
Michal T. Filus, Elliot L. Atlas, Maria A. Navarro, Elena Meneguz, David Thomson, Matthew J. Ashfold, Lucy J. Carpenter, Stephen J. Andrews, and Neil R. P. Harris
Atmos. Chem. Phys., 20, 1163–1181, https://doi.org/10.5194/acp-20-1163-2020, https://doi.org/10.5194/acp-20-1163-2020, 2020
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The effectiveness of transport of short-lived halocarbons to the upper troposphere and lower stratosphere remains an important unknown in quantifying the supply of ozone-depleting substances to the stratosphere. In early 2014, a major field campaign in Guam in the western Pacific, involving UK and US research aircraft, sampled the tropical troposphere and lower stratosphere. The resulting measurements of CH3I, CHBr3 and CH2Br2 are compared here with calculations from a Lagrangian model.
Tobias Wolf, Lasse H. Pettersson, and Igor Esau
Atmos. Chem. Phys., 20, 625–647, https://doi.org/10.5194/acp-20-625-2020, https://doi.org/10.5194/acp-20-625-2020, 2020
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Exceedances of legal thresholds for urban air pollution are of wide concern. We demonstrate the usefulness of very high-resolution modelling for the assessment of air pollution in the urban space on the example of Bergen, Norway. Vulnerability maps highlight areas with high pollutant loading and pathways for pollutant dispersion. This supports the understanding of urban air pollution beyond existing, scarce monitoring networks and possibly the mitigation of impacts on the local population.
Masatomo Fujiwara, Patrick Martineau, and Jonathon S. Wright
Atmos. Chem. Phys., 20, 345–374, https://doi.org/10.5194/acp-20-345-2020, https://doi.org/10.5194/acp-20-345-2020, 2020
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The global response of surface air temperature (SST) to the eruptions of Mount Agung in 1963, El Chichón in 1982, and Mount Pinatubo in 1991 is investigated using 11 global atmospheric reanalysis data sets. Multiple linear regression is applied, with a set of climatic indices orthogonalized, and the residuals are investigated. It is found that careful treatment of tropical SST variability is necessary to evaluate the surface response to volcanic eruptions in observations and reanalyses.
Ping Zhu, Bryce Tyner, Jun A. Zhang, Eric Aligo, Sundararaman Gopalakrishnan, Frank D. Marks, Avichal Mehra, and Vijay Tallapragada
Atmos. Chem. Phys., 19, 14289–14310, https://doi.org/10.5194/acp-19-14289-2019, https://doi.org/10.5194/acp-19-14289-2019, 2019
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Producing timely and accurate intensity forecasts of tropical cyclones (TCs) continues to be one of the most difficult challenges in numerical weather prediction. The difficulty stems from the fact that TC intensification is not only modulated by environmental conditions but also largely depends on TC internal dynamics. The study shows that asymmetric eyewall and rainband eddy forcing above the boundary layer plays an important role in spinning up a TC vortex including rapid intensification.
Jonathan K. P. Shonk, Teferi D. Demissie, and Thomas Toniazzo
Atmos. Chem. Phys., 19, 11383–11399, https://doi.org/10.5194/acp-19-11383-2019, https://doi.org/10.5194/acp-19-11383-2019, 2019
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Modern climate models are affected by systematic biases that harm their ability to produce reliable seasonal forecasts and climate projections. In this study, we investigate causes of biases in wind patterns over the tropical Atlantic during northern spring in three related models. We find that the wind biases are associated with an increase in excess rainfall and convergence in the tropical western Atlantic at the start of April, leading to the redirection of trade winds away from the Equator.
Xinxu Zhao, Julia Marshall, Stephan Hachinger, Christoph Gerbig, Matthias Frey, Frank Hase, and Jia Chen
Atmos. Chem. Phys., 19, 11279–11302, https://doi.org/10.5194/acp-19-11279-2019, https://doi.org/10.5194/acp-19-11279-2019, 2019
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The Weather Research and Forecasting model (WRF), coupled with greenhouse gas (GHG) modules (WRF-GHG), is considered to be a suitable basis for precise GHG transport analysis in urban areas, especially when combined with differential column methodology (DCM). DCM is an effective method not only for comparing models to observations independently of biases caused, for example, by initial conditions, but also for detecting and understanding sources of GHG emissions quantitatively in urban areas.
Xin Hao, Shengping He, Huijun Wang, and Tingting Han
Atmos. Chem. Phys., 19, 9903–9911, https://doi.org/10.5194/acp-19-9903-2019, https://doi.org/10.5194/acp-19-9903-2019, 2019
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The East Asian winter monsoon (EAWM) can be greatly influenced by many factors that can be classified as anthropogenic forcing and natural forcing. Our results show that the increasing anthropogenic emissions in the past decades may have contributed to the weakening of the EAWM, the frequency of occurrence of strong EAWM may have decreased by 45 % due to the anthropogenic forcing, and the anthropogenic forcing is a dominant contributor to the occurrence of a weak EAWM.
Christopher Pöhlker, David Walter, Hauke Paulsen, Tobias Könemann, Emilio Rodríguez-Caballero, Daniel Moran-Zuloaga, Joel Brito, Samara Carbone, Céline Degrendele, Viviane R. Després, Florian Ditas, Bruna A. Holanda, Johannes W. Kaiser, Gerhard Lammel, Jošt V. Lavrič, Jing Ming, Daniel Pickersgill, Mira L. Pöhlker, Maria Praß, Nina Löbs, Jorge Saturno, Matthias Sörgel, Qiaoqiao Wang, Bettina Weber, Stefan Wolff, Paulo Artaxo, Ulrich Pöschl, and Meinrat O. Andreae
Atmos. Chem. Phys., 19, 8425–8470, https://doi.org/10.5194/acp-19-8425-2019, https://doi.org/10.5194/acp-19-8425-2019, 2019
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The Amazon Tall Tower Observatory (ATTO) has been established to monitor the rain forest's biosphere–atmosphere exchange, which experiences the combined pressures from human-made deforestation and progressing climate change. This work is meant to be a reference study, which characterizes various geospatial properties of the ATTO footprint region and shows how the human-made transformation of Amazonia may impact future atmospheric observations at ATTO.
Quan Wang, Chanh Kieu, and The-Anh Vu
Atmos. Chem. Phys., 19, 8383–8397, https://doi.org/10.5194/acp-19-8383-2019, https://doi.org/10.5194/acp-19-8383-2019, 2019
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This study presents an analytical model to study large-scale tropical cyclone (TC) formation that can help us understand the maximum capacity of the Earth's atmosphere to produce TCs. Using a barotropic model for the intertropical convergence zone and recent advances in nonlinear dynamical transition, it is found that the Earth's atmosphere can support a limited number of TCs at any given time (<12) in the current climate, thus providing new theoretical insights into the TC formation process.
Bojan Škerlak, Stephan Pfahl, Michael Sprenger, and Heini Wernli
Atmos. Chem. Phys., 19, 6535–6549, https://doi.org/10.5194/acp-19-6535-2019, https://doi.org/10.5194/acp-19-6535-2019, 2019
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Upper-level fronts are often associated with the rapid transport of stratospheric air to the lower troposphere, leading to significantly enhanced ozone concentrations. This paper considers the multi-scale nature that is needed to bring stratospheric air down to the surface. The final transport step to the surface can be related to frontal zones and the associated vertical winds or to near-horizontal tracer transport followed by entrainment into a growing planetary boundary layer.
Tao Xian and Cameron R. Homeyer
Atmos. Chem. Phys., 19, 5661–5678, https://doi.org/10.5194/acp-19-5661-2019, https://doi.org/10.5194/acp-19-5661-2019, 2019
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Global characteristics and trends in the tropopause (the boundary between troposphere and stratosphere) over a 35-year period (1981–2015) are evaluated using both observations and models. The use of two coordinate systems reveals previously undiagnosed changes in the tropopause altitude within the tropics and extratropics and these results have important implications for studies of climate and atmospheric composition (especially that related to stratosphere–troposphere exchange).
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