Report of Working Group on “Long-term Analysis of Surface

SW Radiation Budget”

T. Hayasaka (RIHN, Japan)

G.-Y. Shi (IAP, China)

A.Ohmura (ETH, Switzerland)

M. Wild (ETH, Switzerland) 　　　　　　

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.

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).

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).

Scientific Review (3)• GCM is still not sufficient for surface radiation budget studies

(Wild, JGR2009a).

Obs.: S(1990-1960)=-3.6(Wm-2/decade)

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.