scholarly journals Development and Evaluation of Chemistry‐Aerosol‐Climate Model CAM5‐Chem‐MAM7‐MOSAIC: Global Atmospheric Distribution and Radiative Effects of Nitrate Aerosol

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Rahul A. Zaveri ◽  
Richard C. Easter ◽  
Balwinder Singh ◽  
Hailong Wang ◽  
Zheng Lu ◽  
...  
Keyword(s):  
Climate Model ◽  
Radiative Effects ◽  
Nitrate Aerosol

scholarly journals An evaluation of clouds and radiation in a large-scale atmospheric model using a cloud vertical structure classification

2020 ◽  
Vol 13 (2) ◽  
pp. 673-684
Author(s):  
Dongmin Lee ◽  
Lazaros Oreopoulos ◽  
Nayeong Cho
Keyword(s):  
Large Scale ◽  
Vertical Structure ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Atmospheric Model ◽  
Radiative Effects ◽  
Surface Cooling ◽  
Vertical Location ◽  
High Clouds

Abstract. We revisit the concept of the cloud vertical structure (CVS) classes we have previously employed to classify the planet's cloudiness (Oreopoulos et al., 2017). The CVS classification reflects simple combinations of simultaneous cloud occurrence in the three standard layers traditionally used to separate low, middle, and high clouds and was applied to a dataset derived from active lidar and cloud radar observations. This classification is now introduced in an atmospheric global climate model, specifically a version of NASA's GEOS-5, in order to evaluate the realism of its cloudiness and of the radiative effects associated with the various CVS classes. Such classes can be defined in GEOS-5 thanks to a subcolumn cloud generator paired with the model's radiative transfer algorithm, and their associated radiative effects can be evaluated against observations. We find that the model produces 50 % more clear skies than observations in relative terms and produces isolated high clouds that are slightly less frequent than in observations, but optically thicker, yielding excessive planetary and surface cooling. Low clouds are also brighter than in observations, but underestimates of the frequency of occurrence (by ∼20 % in relative terms) help restore radiative agreement with observations. Overall the model better reproduces the longwave radiative effects of the various CVS classes because cloud vertical location is substantially constrained in the CVS framework.

scholarly journals Aerosol simulation applying high resolution anthropogenic emissions with the EMAC chemistry-climate model

2011 ◽  
Vol 11 (9) ◽  
pp. 25205-25261 ◽  
Author(s):  
A. Pozzer ◽  
A. de Meij ◽  
K. J. Pringle ◽  
H. Tost ◽  
U. M. Doering ◽  
...  
Keyword(s):  
High Resolution ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Inorganic Aerosols ◽  
The Usa ◽  
Central Atlantic ◽  
Nitrate Aerosol

Abstract. The new high resolution global anthropogenic emission inventory (EDGAR-CIRCE) of gas and aerosol pollutants has been incorporated in the chemistry general circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry). A high horizontal resolution simulation is performed for the years 2005–2008 to evaluate the capability of the model and the emissions to reproduce observed aerosol concentrations and aerosol optical depth (AOD) values. Model output is compared with observations from different measurement networks (CASTNET, EMEP and EANET) and AODs from remote sensing instruments (MODIS and MISR). The model reproduces the main spatial and temporal atmospheric features of the sulfate, ammonium and nitrate aerosol distributions. A good spatial agreement of the distribution of sulfate and ammonium aerosol is found when compared to observations, while calculated nitrate aerosol concentrations show some discrepancies. The simulated temporal development of the inorganic aerosols is in line with measurements of sulfate and nitrate aerosol, while for ammonium aerosol some deviations from observations occur over the USA. The calculated AODs agree well with the satellite observations in most regions, while a negative bias is found for the equatorial area and in the dust outflow regions (i.e. Central Atlantic and Northern Indian Ocean), due to an underestimation of biomass burning and aeolian dust emissions, respectively.

Solar radiation in the cloud-free atmosphere

2021 ◽  
Author(s):  
Martin Wild
Keyword(s):  
Solar Radiation ◽  
Climate Models ◽  
Climate Model ◽  
Temporal Changes ◽  
Climate System ◽  
Radiation Budget ◽  
Radiative Effects ◽  
Free Atmosphere ◽  
Surface Solar Radiation ◽  
Radiative Fluxes

<p>The quantification of Earth’s solar radiation budget and its temporal changes is essential for the understanding of the genesis and evolution of climate on our planet. While the solar radiative fluxes in and out of the climate system can be accurately tracked and quantified from space by satellite programs such as CERES or SORCE, the disposition of solar energy within in the climate system is afflicted with larger uncertainties. A better quantification of the solar radiative fluxes not only under cloudy, but also under cloud-free conditions can help to reduce these uncertainties and is essential for example for the determination of cloud radiative effects or for the understanding of  temporal changes in the solar radiative components of the climate system.</p> <p>We combined satellite observations of Top of Atmosphere fluxes with the information contained in surface flux observations and climate models to infer the absorption of solar radiation in the atmosphere, which we estimated at 73 Wm<sup>-2</sup> globally under cloud-free conditions (Wild et al. 2019 Clim Dyn). The latest generation of climate models participating in CMIP6 is now able to reproduce this magnitude surprisingly well, whereas in previous climate model  generations the cloud-free atmosphere was typically too transparent for solar radiation, which stated a long-standing modelling issue (Wild 2020 Clim Dyn, Wild et al. 1995 JClim).</p> <p>With respect to changes in solar fluxes, there is increasing evidence that the substantial long-term decadal variations in surface solar radiation known as dimming and brightening occur not only under all-sky, but similarly also under clear-sky conditions (Manara et al. 2016 ACP, Yang et al. 2019 JClim; Wild et al. 2021 GRL). This points to aerosol radiative effects as major factor for the explanation of this phenomenon.</p>

scholarly journals Distributions and regional budgets of aerosols and their precursors simulated with the EMAC chemistry-climate model

2012 ◽  
Vol 12 (2) ◽  
pp. 961-987 ◽  
Author(s):  
A. Pozzer ◽  
A. de Meij ◽  
K. J. Pringle ◽  
H. Tost ◽  
U. M. Doering ◽  
...  
Keyword(s):  
North America ◽  
East Asia ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Climate Model ◽  
Temporal Distribution ◽  
Circulation Model ◽  
Temporal Correlation ◽  
Horizontal Resolution ◽  
Nitrate Aerosol

Abstract. The new global anthropogenic emission inventory (EDGAR-CIRCE) of gas and aerosol pollutants has been incorporated in the chemistry general circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry). A relatively high horizontal resolution simulation is performed for the years 2005–2008 to evaluate the capability of the model and the emissions to reproduce observed aerosol concentrations and aerosol optical depth (AOD) values. Model output is compared with observations from different measurement networks (CASTNET, EMEP and EANET) and AODs from remote sensing instruments (MODIS and MISR). A good spatial agreement of the distribution of sulfate and ammonium aerosol is found when compared to observations, while calculated nitrate aerosol concentrations show some discrepancies. The simulated temporal development of the inorganic aerosols is in line with measurements of sulfate and nitrate aerosol, while for ammonium aerosol some deviations from observations occur over the USA, due to the wrong temporal distribution of ammonia gas emissions. The calculated AODs agree well with the satellite observations in most regions, while negative biases are found for the equatorial area and in the dust outflow regions (i.e. Central Atlantic and Northern Indian Ocean), due to an underestimation of biomass burning and aeolian dust emissions, respectively. Aerosols and precursors budgets for five different regions (North America, Europe, East Asia, Central Africa and South America) are calculated. Over East-Asia most of the emitted aerosols (precursors) are also deposited within the region, while in North America and Europe transport plays a larger role. Further, it is shown that a simulation with monthly varying anthropogenic emissions typically improves the temporal correlation by 5–10% compared to one with constant annual emissions.

Investigation of mineral aerosols radiative effects over High Mountain Asia in 1990–2009 using a regional climate model

2016 ◽  
Vol 178-179 ◽  
pp. 484-496 ◽  
Author(s):  
Zhenming Ji ◽  
Shichang Kang ◽  
Qianggong Zhang ◽  
Zhiyuan Cong ◽  
Pengfei Chen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
High Mountain ◽  
Radiative Effects ◽  
Mineral Aerosols

scholarly journals Aerosol–cloud interactions studied with the chemistry-climate model EMAC

2014 ◽  
Vol 14 (15) ◽  
pp. 21975-22043 ◽  
Author(s):  
D. Y. Chang ◽  
H. Tost ◽  
B. Steil ◽  
J. Lelieveld
Keyword(s):  
Cloud Cover ◽  
Climate Model ◽  
Osmotic Coefficient ◽  
Cloud Droplet ◽  
Radiative Effects ◽  
Aerosol Cloud ◽  
Cloud Radiative Effect ◽  
Albedo Effect ◽  
Cloud Radiative Effects ◽  
High Clouds

Abstract. This study uses the EMAC atmospheric chemistry-climate model to simulate cloud properties and estimate cloud radiative effects induced by aerosols. We have tested two prognostic cloud droplet nucleation parameterizations, i.e., the standard STN (osmotic coefficient model) and hybrid (HYB, replacing the osmotic coefficient by the κ hygroscopicity parameter) schemes to calculate aerosol hygroscopicity and critical supersaturation, and consider aerosol–cloud feedbacks with a focus on warm clouds. Both prognostic schemes (STN and HYB) account for aerosol number, size and composition effects on droplet nucleation, and are tested in combination with two different cloud cover parameterizations, i.e., a relative humidity threshold and a statistical cloud cover scheme (RH-CLC and ST-CLC). The use of either STN and HYB leads to very different cloud radiative effects, particularly over the continents. The STN scheme predicts highly effective CCN activation in warm clouds and hazes/fogs near the surface. The enhanced CCN activity increases the cloud albedo effect of aerosols and cools the Earth's surface. The cooler surface enhances the hydrostatic stability of the lower continental troposphere and thereby reduces convection and convective precipitation. In contrast, the HYB simulations calculate lower, more realistic CCN activation and consequent cloud albedo effect, leading to relatively stronger convection and high cloud formation. The enhanced high clouds increase greenhouse warming and moderate the cooling effect of the low clouds. With respect to the cloud radiative effects, the statistical ST-CLC scheme shows much higher sensitivity to aerosol–cloud coupling for all continental regions than the RH-CLC threshold scheme, most pronounced for low clouds but also for high clouds. Simulations of the short wave cloud radiative effect at the top of the atmosphere in ST-CLC are a factor of 2–8 more sensitive to aerosol coupling than the RH-CLC configurations. The long wave cloud radiative effect responds about a factor of 2 more sensitively. Our results show that the coupling with the HYB scheme (κ approach) outperforms the coupling with STN (osmotic coefficient), and also provides a more straightforward approach to account for physicochemical effects on aerosol activation into cloud droplets. Accordingly, the sensitivity of CCN activation to chemical composition is highest in HYB. Overall, the prognostic schemes of cloud cover and cloud droplet formation help improve the agreement between model results and observations, and for the ST-CLC scheme it seems to be a necessity.

scholarly journals Black carbon indirect radiative effects in a climate model

Tellus B ◽  
2017 ◽  
Vol 69 (1) ◽  
pp. 1369342 ◽  
Author(s):  
Ribu Cherian ◽  
Johannes Quaas ◽  
Marc Salzmann ◽  
Lorenzo Tomassini
Keyword(s):  
Black Carbon ◽  
Climate Model ◽  
Radiative Effects

scholarly journals Impacts of emission reductions on aerosol radiative effects

2015 ◽  
Vol 15 (10) ◽  
pp. 5501-5519 ◽  
Author(s):  
J.-P. Pietikäinen ◽  
K. Kupiainen ◽  
Z. Klimont ◽  
R. Makkonen ◽  
H. Korhonen ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Changes ◽  
Radiative Effects ◽  
Clear Sky ◽  
Aerosol Effect ◽  
Emissions Scenarios ◽  
Aerosol Cloud Interactions ◽  
Aerosol Radiative Effects ◽  
Near Future ◽  
Aerosol Radiative

Abstract. The global aerosol–climate model ECHAM-HAMMOZ was used to investigate changes in the aerosol burden and aerosol radiative effects in the coming decades. Four different emissions scenarios were applied for 2030 (two of them applied also for 2020) and the results were compared against the reference year 2005. Two of the scenarios are based on current legislation reductions: one shows the maximum potential of reductions that can be achieved by technical measures, and the other is targeted to short-lived climate forcers (SLCFs). We have analyzed the results in terms of global means and additionally focused on eight subregions. Based on our results, aerosol burdens show an overall decreasing trend as they basically follow the changes in primary and precursor emissions. However, in some locations, such as India, the burdens could increase significantly. The declining emissions have an impact on the clear-sky direct aerosol effect (DRE), i.e. the cooling effect. The DRE could decrease globally 0.06–0.4 W m−2 by 2030 with some regional increases, for example, over India (up to 0.84 W m−2). The global changes in the DRE depend on the scenario and are smallest in the targeted SLCF simulation. The aerosol indirect radiative effect could decline 0.25–0.82 W m−2 by 2030. This decrease takes place mostly over the oceans, whereas the DRE changes are greatest over the continents. Our results show that targeted emission reduction measures can be a much better choice for the climate than overall high reductions globally. Our simulations also suggest that more than half of the near-future forcing change is due to the radiative effects associated with aerosol–cloud interactions.

scholarly journals Radiative effects of ozone waves on the Northern Hemisphere polar vortex and its modulation by the QBO

2018 ◽  
Vol 18 (9) ◽  
pp. 6637-6659 ◽  
Author(s):  
Vered Silverman ◽  
Nili Harnik ◽  
Katja Matthes ◽  
Sandro W. Lubis ◽  
Sebastian Wahl
Keyword(s):  
Planetary Wave ◽  
Climate Model ◽  
Polar Vortex ◽  
Life Cycles ◽  
Early Winter ◽  
Mean Flow ◽  
Radiative Effects ◽  
Quasi Biennial Oscillation ◽  
Wave Effects ◽  
Opposite Manner

Abstract. The radiative effects induced by the zonally asymmetric part of the ozone field have been shown to significantly change the temperature of the NH winter polar cap, and correspondingly the strength of the polar vortex. In this paper, we aim to understand the physical processes behind these effects using the National Center for Atmospheric Research (NCAR)'s Whole Atmosphere Community Climate Model, run with 1960s ozone-depleting substances and greenhouse gases. We find a mid-winter polar vortex influence only when considering the quasi-biennial oscillation (QBO) phases separately, since ozone waves affect the vortex in an opposite manner. Specifically, the emergence of a midlatitude QBO signal is delayed by 1–2 months when radiative ozone-wave effects are removed. The influence of ozone waves on the winter polar vortex, via their modulation of shortwave heating, is not obvious, given that shortwave heating is largest during fall, when planetary stratospheric waves are weakest. Using a novel diagnostic of wave 1 temperature amplitude tendencies and a synoptic analysis of upward planetary wave pulses, we are able to show the chain of events that lead from a direct radiative effect on weak early fall upward-propagating planetary waves to a winter polar vortex modulation. We show that an important stage of this amplification is the modulation of individual wave life cycles, which accumulate during fall and early winter, before being amplified by wave–mean flow feedbacks. We find that the evolution of these early winter upward planetary wave pulses and their induced stratospheric zonal mean flow deceleration is qualitatively different between QBO phases, providing a new mechanistic view of the extratropical QBO signal. We further show how these differences result in opposite radiative ozone-wave effects between east and west QBOs.

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