Saharan Dust Event Impacts on Cloud Formation and Radiation over Western Europe

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.

[1]  G. d’Almeida,et al.  A model for Saharan dust transport , 1986 .

[2]  M. Tiedtke.  A Comprehensive Mass Flux Scheme for Cumulus Parameterization in Large-Scale Models , 1989 .

[3]  B. Ritter,et al.  A comprehensive radiation scheme for numerical weather prediction models with potential applications in climate simulations , 1992 .

[4]  Yongxiang Hu,et al.  An Accurate Parameterization of the Radiative Properties of Water Clouds Suitable for Use in Climate Models , 1993 .

[5]  Z. Levin,et al.  The Effects of Desert Particles Coated with Sulfate on Rain Formation in the Eastern Mediterranean , 1996 .

[6]  M. Garstang,et al.  Temporal and spatial characteristics of Saharan dust outbreaks , 1996 .

[7]  Yaping Shao,et al.  A new model for dust emission by saltation bombardment , 1999 .

[8]  B. Luo,et al.  Water activity as the determinant for homogeneous ice nucleation in aqueous solutions , 2000, Nature.

[9]  N. Middleton,et al.  Saharan dust storms: nature and consequences , 2001 .

[10]  Yinon Rudich,et al.  Desert dust suppressing precipitation: A possible desertification feedback loop , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[11]  L. Gomes,et al.  Modeling mineral aerosol production by wind erosion: Emission intensities and aerosol size distributions in source areas , 2001 .

[12]  F. Pradelle,et al.  Radiative and microphysical interactions between marine stratocumulus clouds and Saharan dust 1. Remote sensing observations , 2002 .

[13]  F. Pradelle,et al.  Radiative and microphysical interactions between marine stratocumulus clouds and Saharan dust 2. Modeling , 2002 .

[14]  B. Vogel,et al.  Modeling aerosols on the mesoscale‐γ: Treatment of soot aerosol and its radiative effects , 2003 .

[15]  Ina Tegen,et al.  Modeling the mineral dust aerosol cycle in the climate system , 2003 .

[16]  V. Freudenthaler,et al.  Long-range transport of Saharan dust to northern Europe : The 11-16 October 2001 outbreak observed with EARLINET , 2003 .

[17]  A. Heymsfield,et al.  Production of Ice in Tropospheric Clouds: A Review. , 2005 .

[18]  Richard Cotton,et al.  Efficiency of the deposition mode ice nucleation on mineral dust particles , 2006 .

[19]  Alexander Khain,et al.  A comparison of spectral bin and two-moment bulk mixed-phase cloud microphysics , 2006 .

[20]  Ulrike Lohmann,et al.  Sensitivity Studies of the Importance of Dust Ice Nuclei for the Indirect Aerosol Effect on Stratiform Mixed-Phase Clouds , 2006 .

[21]  J. Baldasano,et al.  Interactive dust‐radiation modeling: A step to improve weather forecasts , 2006 .

[22]  K. D. Beheng,et al.  A two-moment cloud microphysics parameterization for mixed-phase clouds. Part 1: Model description , 2006 .

[23]  P. Field,et al.  Some ice nucleation characteristics of Asian and Saharan desert dust , 2006 .

[24]  K. Prather,et al.  Direct observations of the atmospheric processing of Asian mineral dust , 2006 .

[25]  A two-moment cloud microphysics scheme with two process-separated modes of graupel , 2006 .

[26]  Klimawirksamkeit von Rußpartikeln in Baden-Württemberg , 2006 .

[27]  Joan E. Shields,et al.  Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density , 2006 .

[28]  C. Kottmeier,et al.  A model of dust transport applied to the Dead Sea area , 2006 .

[29]  Stephan Havemann,et al.  A new parametrization for the radiative properties of ice crystals: Comparison with existing schemes and impact in a GCM , 2007 .

[30]  Yan Yin,et al.  The effects of heating by transported dust layers on cloud and precipitation: a numerical study , 2007 .

[31]  Ari Laaksonen,et al.  The effect of H 2 O adsorption on cloud drop activation of insoluble particles: a theoretical framework , 2007 .

[32]  Manfred Wendisch,et al.  On the direct and semidirect effects of Saharan dust over Europe: A modeling study , 2007 .

[33]  Paul J. DeMott,et al.  An Empirical Parameterization of Heterogeneous Ice Nucleation for Multiple Chemical Species of Aerosol , 2008 .

[34]  Corinna Hoose,et al.  The global influence of dust mineralogical composition on heterogeneous ice nucleation in mixed-phase clouds , 2008 .

[35]  Q. Min,et al.  Evidence of mineral dust altering cloud microphysics and precipitation , 2008 .

[36]  A. Nenes,et al.  Parameterization of cirrus cloud formation in large‐scale models: Homogeneous nucleation , 2008 .

[37]  W. Paul Menzel,et al.  MODIS Global Cloud-Top Pressure and Amount Estimation: Algorithm Description and Results , 2008 .

[38]  A. Nenes,et al.  Parameterizing the competition between homogeneous and heterogeneous freezing in cirrus cloud formation – monodisperse ice nuclei , 2009 .

[39]  A. Nenes,et al.  Parameterizing the competition between homogeneous and heterogeneous freezing in ice cloud formation – polydisperse ice nuclei , 2009 .

[40]  K. Schepanski,et al.  Numerical model simulation of the Saharan dust event of 6-11 March 2006 using the Regional Climate Model version 3 (RegCM3) , 2009 .

[41]  Prashant Kumar,et al.  Parameterization of cloud droplet formation for global and regional models: including adsorption activation from insoluble CCN , 2009 .

[42]  P. Stier,et al.  Comprehensively accounting for the effect of giant CCN in cloud activation parameterizations , 2009 .

[43]  T. Stanelle,et al.  The comprehensive model system COSMO-ART – Radiative impact of aerosol on the state of the atmosphere on the regional scale , 2009 .

[44]  J. Lamarque,et al.  Description and evaluation of the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4) , 2009 .

[45]  T. Stanelle,et al.  Feedback between dust particles and atmospheric processes over West Africa during dust episodes in March 2006 and June 2007 , 2010 .

[46]  U. Lohmann,et al.  The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds , 2010 .

[47]  Zev Levin,et al.  An integrated modeling study on the effects of mineral dust and sea salt particles on clouds and precipitation , 2010 .

[48]  Albert Ansmann,et al.  Saharan dust and heterogeneous ice formation: Eleven years of cloud observations at a central European EARLINET site , 2010 .

[49]  On the effect of insoluble dust particles on global CCN and droplet number , 2010 .

[50]  Longwave indirect effect of mineral dusts on ice clouds , 2010 .

[51]  A. Nenes,et al.  Characteristic updrafts for computing distribution‐averaged cloud droplet number and stratocumulus cloud properties , 2010 .

[52]  Tristan L'Ecuyer,et al.  The impact of precipitating ice and snow on the radiation balance in global climate models , 2010 .

[53]  Athanasios Nenes,et al.  Sensitivity of the global distribution of cirrus ice crystal concentration to heterogeneous freezing , 2010 .

[54]  Slobodan Nickovic,et al.  Saharan dust and ice nuclei over Central Europe , 2010 .

[55]  D. Lüthi,et al.  Implementation and evaluation of aerosol and cloud microphysics in a regional climate model , 2011 .

[56]  H. Chepfer,et al.  Long‐range transport of Saharan dust and its radiative impact on precipitation forecast: a case study during the Convective and Orographically‐induced Precipitation Study (COPS) , 2011 .

[57]  Prashant Kumar,et al.  On the effect of dust particles on global cloud condensation nuclei and cloud droplet number , 2011 .

[58]  Prashant Kumar,et al.  Measurements of cloud condensation nuclei activity and droplet activation kinetics of fresh unprocessed regional dust samples and minerals , 2011 .

[59]  C. Kottmeier,et al.  Regional scale effects of the aerosol cloud interaction simulated with an online coupled comprehensive chemistry model , 2011 .

[60]  B. Vogel,et al.  Towards an online-coupled chemistry-climate model: evaluation of trace gases and aerosols in COSMO-ART , 2011 .

[61]  K. D. Beheng,et al.  Aerosol-cloud-precipitation effects over Germany as simulated by a convective-scale numerical weather prediction model , 2011 .

[62]  M. Baldauf,et al.  Operational Convective-Scale Numerical Weather Prediction with the COSMO Model: Description and Sensitivities , 2011 .

[63]  K. Lundgren.  Direct Radiative Effects of Sea Salt on the Regional Scale , 2012 .

[64]  Paul J. DeMott,et al.  A Particle-Surface-Area-Based Parameterization of Immersion Freezing on Desert Dust Particles , 2012 .