1961～2009年我国地面太阳辐射变化特征及云对其影响的研究

Trends in Surface Solar Radiation (SSR) and the Effect of Clouds on SSR during 1961–2009 in China

基于我国100个地面站点的地面太阳总辐射、日平均云量资料分析1961～2009年我国地面太阳辐射(Surface Solar Radiation,SSR)变化特征及云在不同时期对SSR的影响。结果显示:1961～2009年我国SSR经历了先下降后上升的变化过程,其中1961～1990年SSR显著下降("变暗"),下降速率为-4.3%/10 a(7.87 W m–2(10 a)–1),各地SSR变化趋势比较一致;1990年后SSR开始上升("变亮"),上升速率为2.8%/10 a(2.4 W m–2(10 a)–1),各地SSR变化趋势不如前一阶段一致,但没有显著的地域分布特征。晴空条件的设置对1961～1990年各站点SSR变化特征影响不大,仍为大范围下降("变暗"),但对1990～2009年的结果影响显著。相比全天空条件的结果,晴空条件下1990～2009年我国SSR变化有明显的南北特征,南方地区以"变亮"为主,而北方地区大多继续"变暗",但"变暗"速度减缓。1961～1990年我国总云量总体呈小幅下降趋势,下降速率很慢,这一时期总云量与全天空SSR没有很好的对应关系;1990～2009年我国总云量总体呈小幅上升趋势,有显著的南北分布差异,北方地区以上升趋势为主,南方地区以下降趋势为主,期间云量与全天空情况下SSR有很好的对应关系。这些结果表明,在"变暗"阶段,云对SSR的作用不显著,而在"变亮"阶段,云的作用变得较为突出。

This study investigates variations in surface solar radiation （SSR） and the effects of cloud on SSR during 1961-2009 based on global radiation and cloud fraction data from 100 radiation observation sites over China. The resultsindicate a general decrease of --4.3%/10a （7. 87 W m-2 （10 a）-l） in SSR over land surfaces since measurements began （in about 1961） until 1990, with a turnover corresponding to a 2.8%/10a （2,4 W m-2 （10a） l） increase from 1990 onward. Moreover, this turnover was more significant in southern China. It seems that cloud was not one of the primary factors inducing global dimming during 1961-1990, based on the similar variation characteristics witnessed under all-sky and clear-sky conditions and the weak correlation between total cloud fraction and SSR. However, there were distinct differences between all-sky and clear-sky SSR results after 1990 and it shows a significant negative correlation between all-sky and clear-sky SSR values. Thus, it may be concluded that cloud had a significant effect on SSR variation, such that it may have inhibited global brightening in some way during 1990-2009.