Article

From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth's Surface

Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology (ETH), Winter-thurerstrasse 190, CH-8057 Zurich, Switzerland.
Science (Impact Factor: 33.61). 06/2005; 308(5723):847-50. DOI: 10.1126/science.1103215
Source: PubMed

ABSTRACT

Variations in solar radiation incident at Earth's surface profoundly affect the human and terrestrial environment. A decline in solar radiation at land surfaces has become apparent in many observational records up to 1990, a phenomenon known as global dimming. Newly available surface observations from 1990 to the present, primarily from the Northern Hemisphere, show that the dimming did not persist into the 1990s. Instead, a widespread brightening has been observed since the late 1980s. This reversal is reconcilable with changes in cloudiness and atmospheric transmission and may substantially affect surface climate, the hydrological cycle, glaciers, and ecosystems.

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    • "surface irradiance contribution) that are propagated to the other meteorological fields over time following high non-linear relationships given by the governing equations (Section 4). For many years, the feedback between solar energy and the climate system has been under study by many authors a Budyko (1969) or Wild et al. (2005), among others. However, the effects on mesoscale simulations have not been treated as a relevant issue until now. "
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    ABSTRACT: A wide range of approaches for radiative transfer computations leads to several parameterizations. Differences in these approximations bring about distinct results for the radiative fluxes, even under the same atmospheric conditions. Since the transfer of solar and terrestrial radiation represents the primordial physical process that shapes the atmospheric circulation, these deviations must have an impact on the numerical weather prediction (NWP) model performance. In this paper, an analysis of the role of shortwave schemes on the Weather Research and Forecasting (WRF-ARW) model is presented. The study compares the effect of four parameterizations (Dudhia, New Goddard, CAM and RRTMG) in two cases: i) cloudless and ii) cloudy sky situations for a domain defined over Catalonia (northeast of the Iberian Peninsula). We analyze the direct and the indirect feedback between the dynamical aspects and the physical parameterizations driven by changes in the radiative transfer equation computation. The cumulative effect of these variations are studied through three simulation windows: current day (0-23 h), day-ahead (24-47 h) and two days ahead (48-71 h). These analyses are focused on several NWP model fields. From the most directly related to shortwave schemes such as global horizontal irradiance or the heating rate profile, to apparently secondary outcomes such as wind speed or cloud composition among others. The differences observed between model runs using different solar parameterizations increase with the simulation horizon, being more important in the cloudy scenario than in the cloudless sky.
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    • "Global solar radiation is the primary energy source for life on our planet, which largely determines the climatic conditions of our habitats (Budyko 1969; Wild et al. 2009; Wang et al. 2015a, b). A decreasing global solar radiation around the world (the solar dimming phenomenon) was observed between the 1950s and 1980s (Ohmura 2009; Wild 2009), and the global solar radiation began to increase (the brightening phenomenon) since the late 1980s (Alpert et al. 2005; Wild et al. 2005, 2009). It has been reported that the global solar radiation has generally increased in Germany, Austria, Switzerland, France and United Kingdom during 1985–2005 (Wild et al. 2009). "
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    ABSTRACT: Long-term variation of estimated global solar radiation (E g↓) and its relationship with total cloud cover (TCC), low cloud cover (LCC), water vapor content (WVC) and aerosol optical depth (AOD) were investigated based on the observations at 21 meteorological stations in Hunan province, China. Long-term variations of all variables were calculated for each station; the Mann–Kendall trend test was used to detect the significant level of temporal development trend for each variable; the Pearson correlation analysis was used to measure their linear relationships. Annual E g↓ generally decreased at the rate of −2.11 × 10−3 MJ m−2 decade−1 in Hunan province during 1980–2013. Seasonal mean E g↓ decreased at the rate of −11.99 × 10−3, −4.71 × 10−3 and −4.51 × 10−3 MJ m−2 decade−1 in summer, autumn and winter, respectively, while the increasing trend was observed in spring (15.74 × 10−3 MJ m−2 decade−1). The annual variation of E g↓ in Hunan province was dominantly determined by the variations of AOD (0.33 × 10−3 decade−1) and LCC (0.24 % p decade−1). But the spatial variation of E g↓ in Hunan province was complex. All 21 stations were divided into four groups according to the long-term trends of E g↓, TCC, LCC, AOD and WVC. An increasing E g↓ was observed at stations in group 1, which was determined by the variability of TCC. The variability of AOD and TCC might contribute to the increasing E g↓ in group 2. There were decreasing trends of E g↓ for the stations in group 3 and group 4, which were largely determined by the increases of AOD and LCC.
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    • "This is supported by the fact that observed decadal changes in anthropogenic aerosol emissions are in line with the trends in global solar radiation (Wild, 2009; Folini and Wild, 2011). These evidences have also been supported by changes in solar radiation under clear-sky conditions (Wild et al., 2005; Norris and Wild, 2007, 2009; Ruckstuhl et al., 2008; Folini and Wild, 2011; Soni et al., 2012). Change in aerosol optical depth has been suggested to play a role in the radiation change over China (Kaiser and Qian, 2002), India (Ramanathan and Ramana, 2005; Soni et al., 2012), Europe (Norris and Wild, 2007), and other regions (Wild, 2012). "
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    ABSTRACT: Recent observational studies show that solar radiation incident on ground has not been stable over the last several decades but underwent significant multi-decadal variations. From the 1950s, solar radiation has had a general decreasing trend, named dimming. Since the late 1980s, a trend reversal and partial recovery has been observed at many observations sites across the globe; it is the so-called brightening. The present study examined temporal and spatial trends in surface solar radiation (global and diffuse) and sunshine duration in India using a 40-year data set (1971-2010) of the twelve stations of solar radiation network of the India Meteorological Department. The research work examines the global solar radiation trends in all-sky and cloud-free sky conditions. The long-term variability in the diffuse components of solar radiation, bright sunshine duration, and cloud cover has also been studied over India.India is one of the few regions that showed a continuous and steady decline in global solar radiation from the 1970s to 2000. The declining trend of all-sky global irradiance over India as a whole was 0.6Wm-2 year-1 during 1971-2000 and 0.2Wm-2 year-1 during 2001-2010. A third-order polynomial fit to the data indicated a reversal in all-sky global irradiance around 2001 at some sites. Reversal or stabilization of global irradiance is also seen in seasonal mean values at some of the stations. The reversal in clear-sky global irradiance was clearly evident from 2001. Similar trend is also observed in bright sunshine duration. This confirms the well-known phenomenon of global dimming and global brightening over India. The analysis of global irradiance data highlights the fact that in general the dimming/brightening is station dependent because of regional sources and meteorology which contribute to the variation in solar irradiance.
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