Niwano Masashi, Hashimoto Akihiro, Aoki Teruo
Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, 305-0052, Japan.
National Institute of Polar Research, Tachikawa, 190-8518, Japan.
Sci Rep. 2019 Jul 17;9(1):10380. doi: 10.1038/s41598-019-46152-5.
Clouds have been recognized to enhance surface melt on the Greenland Ice Sheet (GrIS). However, quantitative estimates of the effects of clouds on the GrIS melt area and ice-sheet-wide surface mass balance are still lacking. Here we assess the effects of clouds with a state-of-the-art regional climate model, conducting a numerical sensitivity test in which adiabatic atmospheric conditions as well as zero cloud water/ice amounts are assumed (i.e., clear-sky conditions), although the precipitation rate is the same as in the control all-sky simulation. By including or excluding clouds, we quantify time-integrated feedbacks for the first time. We find that clouds were responsible for a 3.1%, 0.3%, and 0.7% increase in surface melt extent (of the total GrIS area) in 2012, 2013, and 2014, respectively. During the same periods, clouds reduced solar heating and thus daily runoff by 1.6, 0.8, and 1.0 Gt day, respectively: clouds did not enhance surface mass loss. In the ablation areas, the presence of clouds results in a reduction of downward latent heat flux at the snow/ice surface so that much less energy is available for surface melt, which highlights the importance of indirect time-integrated feedbacks of cloud radiative effects.
人们已经认识到云层会加剧格陵兰冰原（GrIS）的表面融化。然而，对于云层对格陵兰冰原融化面积和全冰原表面质量平衡影响的定量估计仍然缺乏。在这里，我们使用先进的区域气候模型评估云层的影响，进行了一次数值敏感性测试，其中假设了绝热大气条件以及云水/冰量为零（即晴空条件），尽管降水率与对照的全天空模拟相同。通过纳入或排除云层，我们首次量化了时间积分反馈。我们发现，云层分别导致2012年、2013年和2014年格陵兰冰原总面积表面融化范围增加了3.1%、0.3%和0.7%。在同一时期，云层分别使太阳加热减少，从而使每日径流量减少了1.6、0.8和1.0吉吨：云层并没有加剧表面质量损失。在消融区，云层的存在导致雪/冰表面向下的潜热通量减少，因此可用于表面融化的能量少得多，这突出了云层辐射效应间接时间积分反馈的重要性。
