Report of Working Group on

1
Report of Working Group on Long-term Analysis of
Surface SW Radiation Budget

• T. Hayasaka (RIHN, Japan)
• G.-Y. Shi (IAP, China)
• Ohmura (ETH, Switzerland)
• M. Wild (ETH, Switzerland)

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Objectives

• Review of long-term analysis of surface SW
  radiation and related items such as aerosols and
  clouds.
• Collection of long-term data of surface SW
  radiation and the related data including
  proxy-data useful for SW calculations.
• Promotion of long-term analysis of surface SW
  radiation and the related data, focusing on their
  regional properties.

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Scientific Review (1)

• The global dimming and brightening is reviewed in
  JGR special issue (M. Wild, ed.).
• Many of ground based measurements show a
  decreasing trend until around 1990 and then
  changed to increase (Wild, JGR2009b).

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Scientific Review (2)

• In the IPCC-AR4(2007), the global dimming
  phenomenon is implicated as a result of
  urbanization according to Alpert et al.
  (GRL2005).
• However, it is still uncertain. The global
  dimming and brightening phenomena are observed
  not only in urban areas but also remote areas
  such as Mauna Loa and South Pole (Dutton et al.,
  JGR2006).
• There are many evidences from direct and indirect
  observations (sunshine duration, pan evaporation,
  etc.).
• Anthropogenic aerosols have a potential to affect
  the surface shortwave irradiance and the
  mechanism of the aerosol effect is complicated
  and different among regions (Wild, JGR2009b).

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Scientific Review (3)

• GCM is still not sufficient for surface radiation
  budget studies (Wild, JGR2009a).

Obs. DS(1990-1960)-3.6(Wm-2/decade)
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Working group activity

• Dr. Martin Wild (ETH) joined the working group.
• The next step is to elucidate the mechanism of
  long-term variation of surface shortwave
  irradiance, for example, global dimming and
  brightening.
• We need a collaboration with observation and data
  archive group such as BSRN, GEBA, WRDC, SKYNET,
  etc.
• We also need a collaboration with GCM community
  because the observation and model simulation are
  not consistent with each other.
• Aerosol-cloud interaction is the key to
  understanding the surface shortwave irradiance
  variation. Therefore, not only the long-term
  analysis but also the process studies are needed.
• A next workshop or meeting focusing on the above
  topics should be held in the near future although
  a concrete plan is not decided yet.