Environmental dependence and seasonal variation of diffuse solar radiation in tropical peatland
Environmental dependence and seasonal variation of diffuse solar radiation in tropical peatland
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DOI：
10.2480/agrmet.d-14-00028
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发表时间：
2014-12
影响因子：
1.3
通讯作者：
F. Marpaung;T. Hirano
中科院分区：
文献类型：
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作者：
F. Marpaung;T. Hirano
云量和大气气溶胶含量的变化对太阳辐射的漫射比例(Rd/Rg)有很大影响。据报道，植物在漫射光条件下的光合作用效率更高，但热带泥炭地经常遭受大范围火灾的漫射辐射(RD)机制描述得很差，到目前为止几乎没有基于现场的数据集。因此，我们在印度尼西亚加里曼丹中部热带泥炭地的一片被烧毁的前森林中连续测量了三年多的RD。日Rd/Rg与清晰度指数(Rg/Ro)呈线性阈值模型相关。模式参数表明，在气候湿润的热带泥炭地，晴空下的Rd/Rg比澳大利亚大。使用该模型，从附近森林上空测量的Rg估计了超过12年的Rd/Rg的长期变化。结果表明，Rd/Rg具有明显的季节性变化，月平均Rd/Rg在6月份(雨季和旱季的过渡)最小为0.51，在10月份(旱季后期)最大为0.68。从雨季晚期到旱季早期的减少模式对应于由于云量减少而导致的降水减少。相比之下，旱季后半段的增长模式是由于燃烧生物质和泥炭火排放的烟雾造成的。特别是，在2002年、2006年和2009年厄尔尼诺干旱期间，由于地面被大规模火灾产生的浓烟覆盖，月平均RD/Rg升至0.72以上。
Changes in cloud cover and atmospheric aerosol loading strongly affect the diffuse proportion of solar radiation (Rd/Rg). It has been reported that plant photosynthesis is more efficient under diffuse light conditions, but diffuse radiation (Rd) regimes in tropical peatland frequently subjected to largescale fires are poorly described, and there are few or no site-based datasets to date. Therefore, we continuously measured Rd for more than three years at a burnt ex-forest on tropical peatland in Central Kalimantan, Indonesia. Daily Rd/Rg was significantly related to the clearness index (Rg/Ro) with a linear threshold model. The model parameters showed that Rd/Rg under a clear sky is larger in tropical peatland with a humid climate than in Australia. Using the model, long-term variation in Rd/Rg for more than 12 years was estimated from Rg measured above a nearby forest. As a result, Rd/Rg showed a seasonal variation with its minimum of 0.51 in June (the transition between the wet and dry seasons) and its maximum of 0.68 in October (the late dry season) on a monthly basis. The decreasing pattern from the late wet season to the early dry season corresponded to decreasing precipitation due to fewer clouds. In contrast, the increasing pattern through the latter half of the dry season was due to shading by smoke emitted through burning biomass and peat fires. In particular, during the El Niño droughts in 2002, 2006 and 2009, the monthly mean Rd/Rg rose above 0.72, because the ground was densely covered with smoke from large-scale fires.