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| Titel |
Climate Sensitivities due to Stratocumulus Cloud droplet number concentrations |
| VerfasserIn |
Ben Parkes, Laura Stevens, Alan Gadian, John Lathman, Alan Blyth |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250045374
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| Zusammenfassung |
| Four experiments have been carried out using the Met Office Unified Model v6.1 (HadGEM1) to investigate the effects of albedo modification on the climate system as the amount of carbon dioxide in the atmosphere continues to rise. This work is designed to analyse and assess the "cloud whiteneing" method of geoengineering postulated in (Latham, 1990) and expanded upon by (Latham et al., 2008)(Salter et al., 2008) and (Rasch et al., 2009). Consideration will be given to the effect of the cloud modification on rainfall rates and global circulation patterns. Furthermore temperature changes in polar regions are investigated to assess the increase in polar sea ice coverage.
The four experiments are a control, one with an increase in carbon dioxide by 1% per year and two potential geoengineering scenarios based on a climate with increasing carbon dioxide. The first geoengineering simulation consists of forcing clouds with a cloud droplet number concentration (CDNC) of N = 375 m-3 over three regions of low lying stratocumulus clouds. These regions are the West coasts of California, Peru and Namibia(Latham et al., 2008). The second geoenginnering simulation is based upon forcing all marine environments with a CDNC of N = 375 m-3. Starting conditions for the experiments were provided by the UK Met Office from the A1B simulation used in the 2007 Intergovernmental Panel on Climate Change report(IPCC,
2007).
The geoengineering method proposed relies on the aerosol indirect effect(Twomey, 1977) and the second aerosol indirect(Albrecht, 1989) effects on clouds to increase their brightness and prolong their lifetime. The effects of a change in CDNC on a clean marine stratocumulus cloud can be investigated using data collected from the VOCALs field campaign which took place in the South Eastern Pacific in 2008. radiometry and in cloud data has been collected by several aircraft including the FAAM BAe-146 and the NCAR/NSF C-130(Allen & Abel, 2009). The albedo of the observed region has been provided by satellite imagery from the GOES-10 satellite.
References:
John Latham 1990: Nature vol 347, pp339-340
John Latham et al., 2008: Philosophical Transactions of The Royal Society A vol 366, pp3969-3987
Stephen Salter et al., 2008: Philosophical Transactions of The Royal Society A vol 366, pp3989-4006
Rasch et al., 2009: Environmental Research Letters 4
IPCC Working Group I, 2007: IPCC Synthesis report Chapter 2
S. Twomey, 1977: Journal of the Atmospheric Sciences vol 34, pp1149-1152
Bruce A. Albrecht, 1989: Science vol 245, pp1227-1230
Grant Allen & Steven Abel: 2009, VAMOS Ocean-Climate-Atmosphere-Land Study: UK component |
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