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Comment Response 7-1 7 0 Propose to Add References to AMAP Report 2012 on Effects of BC in the Arctic

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Comment Response 7-1 7 0 Propose to Add References to AMAP Report 2012 on Effects of BC in the Arctic Expert Review Comments on the IPCC WGI AR5 First Order Draft -- Chapter 7 Comment Chapter From From To To No Page Line Page Line Comment Response 7-1 7 0 Propose to add references to AMAP report 2012 on effects of BC in the Arctic. AMAP, 2011. The Impact of reviewer needs to be specific as to where this fits. Black Carbon on Arctic Climate (2011). Quinn et al. Arctic Monitoring and Assessment Programme (AMAP), Preference goes to peer-reviewed literature. Oslo. 72 pp. [Øyvind Christophersen, Norway] 7-2 7 0 This chapter is considerably improved from the ZOD, and I commend the authors for constructing a draft that We concur with these comments about the amounts is more balanced, better organized, covers most of the important issues, and is well written. That having been of detail in each section. We will try to address the said, there are still differences in approach and emphasis among the individual sections on clouds, aerosols, imbalances while at the same time reducing the and cloud-aerosol interactions. The chapter as a whole would benefit if these differences were reduced. The overall length as required by the TSU. clouds section, with one exception noted in a future comment, really focuses on the climatic effects of clouds and eschews detailed discussions of the cloud physics that leads to these climate effects, so much so that some of the more important science issues are ignored and others given short shrift. The aerosol section is just the opposite - it reads more like a review article in a journal than an IPCC report section, reviewing all the details of aerosol physics/chemistry, including many things that may or may not turn out to be significant in the future but which have not yet been demonstrated to be important to climate change. It seems to this reviewer that the cloud-aerosol interaction section comes closest to getting the balance right between explaining details of the physics and explaining how they are understood to affect or not affect climate change. The section on cosmic ray effects on climate is too long given that there are as yet no demonstrated, or even likely, effects on long-term climate change; the length of this section conveys to the reader a sense of the importance of this topic that is not indicative of the sense of the community. The geoengineering section strikes a reasonable balance. [Anthony Del Genio, USA] 7-3 7 0 This Chapter purports comprehensive information on the role of aerosols (both natural and anthropogenic), Thanks. clouds and their interactions in the present-day climate and climate change scenarios covering from tropics through poles. It provides an overview on the rapid responses and feedbacks between aerosols and clouds vis-a-vis precipitation in changing climate, particularly through their radiative forcing (direct, semi-direct and indirect effects). The state-of-the-art of process-based climate models, their capabilities and requirements for improving them against the in-situ and remote sensing observations has also been detailed in this Chapter. The deviations are discussed mainly in terms of the existing theories and new discoveries. The Chapter concludes with direction and further understanding of unknown feedbacks and aerosol-cloud-climate interactions including recently-introduced stratogies / studies like Solar Radiation Management for geoengineering, cosmic ray influence on new particle formation etc. [Panuganti China Sattilingam Devara, India] 7-4 7 0 This chapter gives an overview of our current knowledge and understanding of aerosols, clouds, and their This chapter focuses on cloud and aerosol processes, mutual interactions with the climate system by describing results from ground and space borne observations, rather than the regional climate response to clouds theoretical models, detailed cloud resolving models and global models. We find that not enough emphasis is and aerosols. In that sense, a lot of the discussion given to regional climate models as well as the regional impacts of clouds and aerosols in this chapter. Global applies equally to global and regional models. Some climate models are often not detailed enough to give robust information on the regional scale. Such regional aspects are discussed in section 7.2 (cloud information is however highly relevant for the society and for policy-makers. As has been noted in the chapter, feedbacks) and 7.6 (precipitation). Regional climates there currently is a gap between high resolution cloud models and global models. Although GCRMs might be are discussed in chapter 14. able to close this gap in a decade, regional online-coupled climate models with an explicit treatment of atmospheric chemistry and aerosols can close it much earlier, although for a limited area of the globe. We provide some concrete suggestions on how this point can be taken better into account in this review. Additional/further improvements may still be possible. [Andrew Ferrone, Germany] 7-5 7 0 Overall, I complement the authors on an excellent first draft. [Warren Richard Leaitch, Canada] Thanks. 7-6 7 0 Bell et al. (2008) and Lee (2012) have suggested that aerosol-pollution-induced changes in large-scale this chapter focuses on aerosol forcing. We have circulations affect clouds far removed from an aerosol-pollution source. Stately differently, aerosol pollution introduced the concept of adjusted forcing, which can be tele-connected to clouds far away from the pollution source, leading to the redistribution of energy and includes rapid adjustments to aerosol-cloud water in much larger areas than areas directly affected by aerosol pollution. This indicates that just focusing on interactions and remote effects of aerosols on clouds. polluted areas can be misleading and we need to think about the effect of aerosol pollution with temporal and The large-scale impact of aerosols on regional climate spatial scales larger than those scales for aerosol pollution. This tele-connection of aerosol effect is supported is discussed in Chapter 14. by other studies. Lynn et (2005a,b) simulated a rain event over Florida using MM5 with spectral bin Do not Cite, Quote or Distribute Page 1 of 143 Expert Review Comments on the IPCC WGI AR5 First Order Draft -- Chapter 7 Comment Chapter From From To To No Page Line Page Line Comment Response microphysics. They showed that in spite of the fact that aerosol pollution tends to intensify squall line over a polluted area, the total precipitation over larger computational area than the polluted area remained unchanged or slightly decreased. Even more pronounced mechanism of aerosol effect on a large scale phenomenon (a tropical cyclone (TC)) was investigated by Rosenfeld et al (2007), Zhang et al (2007), Khain et al (2008-2010). It was shown that aerosol-intensified convection developing at TC periphery competes with that in the eyewall convection leading to TC weakening and to a decrease in precipitation over the entire region. The importance of compensating downdrafts as well as of a cool pool in the boundary layer arising in zones of convective precipitation and expanding toward the TC center was stressed. This reviewer believes this tele-connection effect needs to be included in this report, considering increasing spatial gradient of aerosol concentration (which drives this tele-connection) since industrialization. Since industrialization, land-sea contrast in aerosol concentration has increased. Also, increasing pollution in urban areas since industrialization has enhanced the spatial gradient over land. Hence, it is likely that energy and water redistribution by tele-connection has been changing since industrialization. Large-scale circulations have a long-term effect on climate as compared to aerosol pollution itself and associated individual clouds. Thus, aerosol effect on these circulations and the effect of aerosol-induced circulations on much larger areas than polluted areas are likely to be more relevant to climate than aerosol pollution and its effect on clouds over the polluted areas. References: Bell, T. L., Rosenfeld, D., Kim, K.-M., et al.: Midweek increase in U. S. summer rain and storm heights suggests air pollution invigorates rainstorms, J. Geophy. Res., 113, D02209, doi:10.1029/2007JD008623, 2008. Khain, A. P., N. Cohen, B. Lynn and A. Pokrovsky, 2008: Possible aerosol effects on lightning activity and structure of hurricanes. J. Atmos. Sci. 65, 3652-3667. Khain, A. P., B. Lynn and J. Dudhia, 2010: Aerosol effects on intensity of landfalling hurricanes as seen from simulations with WRF model with spectral bin microphysics, J. Atmos. Sci. , 67, 365-384 Lee, S. S., 2011, Effect of aerosol on circulations and precipitation in deep convective clouds, J. Atmos. Sci., accepted. Lynn B., Khain, A. P., J. Dudhia, D. Rosenfeld, A. Pokrovsky, and A. Seifert 2005a: Spectral (bin) microphysics coupled with a mesoscale model (MM5). Part 1. Model description and first results. Mon. Wea. Rev. 133, 44-58. Lynn B., Khain, A. P., J. Dudhia, D. Rosenfeld, A. Pokrovsky, and A. Seifert 2005b: Spectral (bin) microphysics coupled with a mesoscale model (MM5). Part 2: Simulation of a CaPe rain event with squall line Mon. Wea. Rev. , 133, 59-71. Rosenfeld, D., Khain, A. P., B. Lynn, W. L. Woodley, 2007: Simulation of hurricane response to suppression of warm rain by sub-micron aerosols. Atmos. Chem. Phys. Discuss., 7, 5647-5674, Zhang, H., G.M. McFarquhar, S.M. Saleeby, and W.R. Cotton 2007: Impacts of Saharan dust as CCN on the evolution of an idealized tropical cyclone. Geophys. Res. Lett. 34 L14812, doi: 10.2029/2007GL029876 [Seoung Soo Lee, United States of America] 7-7 7 0 A well established chapter with clear explanations and statements [Claudia Mäder, Germany] Thanks. 7-8 7 0 As far as aerosols are concerned, about 70% of the global abundance still remains natural.It is also now well this is a good remark. Unfortunately there is extremely recognized that the increased human activity pressure, has significantly altered the natural component also, so little literature on anthropogenic modification to the that there is a signicicant human-induced nautral component.
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