Aerosol-cloud-precipitation effects over Germany as simulated by a convective-scale numerical weather prediction model

Seifert, Axel; Köhler, Carmen; Beheng, K.D.

doi:10.5194/acpd-11-20203-2011

Cited by 36 publications

(53 citation statements)

References 52 publications

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“…We propose to address this question by repeating large numbers of LES, CRM, and coarser mesh model simulations in specified cloud regimes using initial conditions from routine observations (or observationally constrained model output), as in ref. 35, but also including aerosol information. Initial conditions could be based on radiosondes or from reanalysis, daily Numerical Weather Prediction (NWP) derived soundings, or variational analysis (36).…”

Section: A Path Forwardmentioning

confidence: 99%

New approaches to quantifying aerosol influence on the cloud radiative effect

Feingold

McComiskey

Yamaguchi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphysical entities and, by their very nature, ephemeral and hard to predict. Atmospheric general circulation models represent aerosol−cloud interactions at everincreasing levels of detail, but these models lack the resolution to represent clouds and aerosol−cloud interactions adequately. There is a dearth of observational constraints on aerosol−cloud interactions. We develop a conceptual approach to systematically constrain the aerosol−cloud radiative effect in shallow clouds through a combination of routine process modeling and satellite and surfacebased shortwave radiation measurements. We heed the call to merge Darwinian and Newtonian strategies by balancing microphysical detail with scaling and emergent properties of the aerosol−cloud radiation system.T he climate system, with its couplings between land surface, vegetation, ocean, cryosphere, and atmosphere, is an extraordinarily complex system that is under intensive scrutiny for the purposes of climate analysis and prediction. The atmospheric aerosol and its interaction with clouds is a poorly quantified component of the climate system and is the focus of the current study. The aerosol comprises suspended particles that derive from the oceans, land surface, volcanoes, and anthropogenic activities. The difficulty in quantifying climate forcing by the aerosol emanates partly from the complexity in the aerosol itself, and partly from the fact that its influence on clouds requires detailed understanding of clouds and cloud feedbacks at a range of spatiotemporal scales. Untangling the multiple cloud responses that occur as a result of aerosol perturbations is particularly difficult (1). As one example, consider the influence of the aerosol on clouds and precipitation. Assuming no change in condensed water, the aerosol, by acting as nucleation sites for droplets, might generate smaller droplets, more reflective clouds (2), and reduced precipitation (3). However, through a multitude of complex and contingent pathways, aerosol-perturbed clouds sometimes appear to have similar reflectance because brightening is offset by reductions in cloud water, a fundamental property controlling cloud reflectance. On short timescales (hours), the aerosol tends to reduce precipitation in shallow, liquid-only clouds, but this may be offset over longer periods (multiple days) (4). Deep, mixed-phase convective clouds present even more complex pathways for generation of precipitation, and even more contingencies. The aerosol appears to change the distribution and intensity of surface rain from deep c...

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Section: A Path Forwardmentioning

confidence: 99%

New approaches to quantifying aerosol influence on the cloud radiative effect

Feingold

McComiskey

Yamaguchi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…This may introduce an underestimation of the glaciation of mixed phase clouds for high IN concentrations, but can be justified by a small fraction of cloud droplets originating from activated dust particles in our simulations. A detailed description of the cloud microphysical processes is given in , and a statistical analysis of the aerosol-cloud interaction for three summer seasons using the microphysics scheme is presented in Seifert et al (2011).…”

Section: Cloud Microphysicsmentioning

confidence: 99%

Saharan dust event impacts on cloud formation and radiation over Western Europe

et al. 2012

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Abstract.We investigated the impact of mineral dust particles on clouds, radiation and atmospheric state during a strong Saharan dust event over Europe in May 2008, applying a comprehensive online-coupled regional model framework that explicitly treats particle microphysics and chemical composition. Sophisticated parameterizations for aerosol activation and ice nucleation, together with two-moment cloud microphysics are used to calculate the interaction of the different particles with clouds depending on their physical and chemical properties.The impact of dust on cloud droplet number concentration was found to be low, with just a slight increase in cloud droplet number concentration for both uncoated and coated dust. For temperatures lower than the level of homogeneous freezing, no significant impact of dust on the number and mass concentration of ice crystals was found, though the concentration of frozen dust particles reached up to 100 l −1 during the ice nucleation events. Mineral dust particles were found to have the largest impact on clouds in a temperature range between freezing level and the level of homogeneous freezing, where they determined the number concentration of ice crystals due to efficient heterogeneous freezing of the dust particles and modified the glaciation of mixed phase clouds.Our simulations show that during the dust events, ice crystals concentrations were increased twofold in this temperature range (compared to if dust interactions are neglected).This had a significant impact on the cloud optical properties, causing a reduction in the incoming short-wave radiation at the surface up to −75 W m −2 . Including the direct interaction of dust with radiation caused an additional reduction in the incoming short-wave radiation by 40 to 80 W m −2 , and the incoming long-wave radiation at the surface was increased significantly in the order of +10 W m −2 .The strong radiative forcings associated with dust caused a reduction in surface temperature in the order of −0.2 to −0.5 K for most parts of France, Germany, and Italy during the dust event. The maximum difference in surface temperature was found in the East of France, the Benelux, and Western Germany with up to −1 K. This magnitude of temperature change was sufficient to explain a systematic bias in numerical weather forecasts during the period of the dust event.

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“…A detailed description of the cloud microphysical processes is given in Seifert and Beheng (2006a). A statistical analysis of the aerosolÁcloud interaction for three summer seasons using the microphysics scheme is presented in Seifert et al (2012). …”

Section: Cloud Microphysics Schemementioning

confidence: 99%

“…The scheme distinguishes six hydrometeor categories (cloud drops, cloud ice, rain, snow, graupel and hail) and represents each particle type by its respective number and mass densities. A generalised gamma size distribution is used for each hydrometeor class, where the so-called shape parameters are held constant during the simulation (Seifert et al, 2012, Table 1). For the warm-phase clouds, the scheme considers autoconversion of cloud droplets to rain, accretion of cloud droplets by rain drops, self-collection of cloud and rain droplets, break-up of rain drops and evaporation of rain drops.…”

Section: Cloud Microphysics Schemementioning

confidence: 99%

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Impact of aerosol on post-frontal convective clouds over Germany

Rieger¹,

Bangert²,

Kottmeier³

et al. 2014

Tellus B: Chemical and Physical Meteorology

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A B S T R A C TWe carried out simulations with predefined and simulated aerosol distributions in order to investigate the improvement in the forecasting capabilities of an operational weather forecast model by the use of an improved aerosol representation. This study focuses on convective cumulus clouds developing after the passage of a cold front on 25 April 2008 over Germany. The northerly flow after the cold front leads to increased sea salt aerosol concentrations compared to prefrontal conditions. High aerosol number concentrations are simulated in the interactive scenario representing typically polluted conditions. Nevertheless, due to the presence of sea salt particles, effective radii of cloud droplets reach values typical of pristine clouds (between 7 mm and 13 mm) at the same time. Compared to the predefined continental and maritime aerosol scenarios, the simulated aerosol distribution leads to a significant change in cloud properties such as cloud droplet radii and number concentrations. Averaged over the domain covered by the convective cumuli clouds, we found a systematic decrease in precipitation with increasing aerosol number concentrations. Differences in cloud cover, short wave radiation and cloud top heights are buffered by systematic differences in precipitation and the related diabatic effects. Comparisons with measured precipitation show good agreement for the interactive aerosol scenario as well as for the extreme maritime aerosol scenario.

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Aerosol-cloud-precipitation effects over Germany as simulated by a convective-scale numerical weather prediction model

Cited by 36 publications

References 52 publications

New approaches to quantifying aerosol influence on the cloud radiative effect

New approaches to quantifying aerosol influence on the cloud radiative effect

Saharan dust event impacts on cloud formation and radiation over Western Europe

Impact of aerosol on post-frontal convective clouds over Germany

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