当前位置： 首页»科研成果» 2013 Measurement Methods Affect the Observed Global Dimming and Brightening 王开存、马倩

 

Kaicun Wang, Robert E. Dickinson, Qian Ma, John A. Augustine, Martin Wild

 

State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing, China;

Department of Geological Sciences, The University of Texas at Austin, Austin, Texas;

College of Global Change and Earth System Science, Beijing Normal University, Beijing, China;

NOAA/Earth System Research Laboratory, Boulder, Colorado;

Institute for Atmospheric and Climate Science, ETH Zürich, Zurich, Switzerland.

 

ABSTRACT

Surface incident solar radiation G determines our climate and environment, and has been widely observed with a single pyranometer since the late 1950s. Such observations have suggested a widespread decrease between the 1950s and 1980s (global dimming), that is, at a rate of −3.5 W m−2 decade−1 (or −2% decade−1) from 1960 to 1990. Since the early 1990s, the diffuse and direct components of G have been measured independently, and a more accurate G has been calculated by summing these two measurements. Data from this summation method suggest that G increased at a rate of 6.6 W m−2 decade−1 (3.6% decade−1) from 1992 to 2002 (brightening) at selected sites. The brightening rates from these studies were also higher than those from a single pyranometer. In this paper, the authors used 17 years (1995–2011) of parallel measurements by the two methods from nearly 50 stations to test whether these two measurement methods of G provide similar long-term trends. The results show that although measurements of G by the two methods agree very well on a monthly time scale, the long-term trend from 1995 to 2011 determined by the single pyranometer is 2–4 W m−2 decade−1 less than that from the summation method. This difference of trends in the observed G is statistically significant. The dependence of trends of G on measurement methods uncovered here has an important implication for the widely reported global dimming and brightening based on datasets collected by different measurement methods; that is, the dimming might have been less if measured with current summation methods.

 

KEY WORDS: Shortwave radiation, Data quality control, Instrumentation/sensors, Surface observations, Climate variability, Decadal variability

 

PUBLISHED IN: JOURNAL OF CLIMATE, 2013, 26 (12): 4112–4120.

 

SOURCE: http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00482.1