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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Impact of land use on Costa Rican tropical montane cloud forests: Sensitivity of cumulus cloud field characteristics to lowland deforestation - art. no. 4206
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Impact of land use on Costa Rican tropical montane cloud forests: Sensitivity of cumulus cloud field characteristics to lowland deforestation - art. no. 4206

机译：土地使用对哥斯达黎加热带山地云雾森林的影响：积云场特征对低地森林砍伐的敏感性-艺术。没有。 4206

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1] Recent studies have shown that there has been a reduction in dry season moisture input from direct interception of cloud water and wind-blown mist at the lee edge of the Monteverde cloud forest, Costa Rica, since the mid 1970s. This reduction of moisture could be responsible for the population crashes of anurans observed in the region. It has been hypothesized that this behavior is a result of increases in cloud base height, linked to increased sea surface temperatures. In this study we present a complementary hypothesis, that deforestation upwind of the Monteverde cloud forest preserve is responsible for the observed changes in cloud base height. An automated cumulus cloud classification scheme extracts monthly spatial maps of the frequency of occurrence of cumulus cloudiness over Costa Rica from GOES 8 visible channel satellite imagery. We find that cumulus cloud formation in the morning hours over deforested regions is suppressed compared to forested areas. The degree of suppression appears to be related to the extent of deforestation. This difference in cloud formation between forested and deforested areas is a clear signal of land use change influencing the regional climate. Regional Atmospheric Modeling System numerical modeling simulations are used to explore the differences in cloud field characteristics over the lowland pasture and forest landscapes. Statistically significant differences in cloud base height and cloud thickness occur between the forest and pasture simulations. Clouds have higher base heights and are thinner over pasture landscapes than over forested ones. On the other hand, these simulations show no statistically significant differences in cloud top heights, cloud cover, mean cloud water mixing ratio, or cloud liquid water path between pasture and forest simulations. However, in the simulations there are enhanced sensible heat fluxes and reduced latent heat fluxes over pasture compared to forest. It is the drier and warmer air over pasture surfaces that results in the formation of elevated thinner clouds. This study suggests that deforestation results in warmer, drier air upwind of the Monteverde cloud forests and that this could influence the base height of orographic cloudbanks crucial to the region during the dry season. [References: 47
机译：1]最近的研究表明，自1970年代中期以来，在哥斯达黎加的蒙特维德云雾森林的背风边缘直接截取云水和风吹的薄雾，干旱季节的水分输入有所减少。水分的减少可能是造成该地区无氧菌种群崩溃的原因。据推测，这种行为是由于云底高度增加而导致的，这与海面温度升高有关。在这项研究中，我们提出了一个补充假设，即蒙特维德云雾森林保护区的上风森林砍伐是造成云底高度变化的原因。自动化的积云分类方案从GOES 8可见通道卫星影像中提取哥斯达黎加积云发生频率的月度空间图。我们发现，与森林区域相比，在森林砍伐区域的早晨，积云形成受到抑制。抑制程度似乎与森林砍伐的程度有关。森林区域和森林砍伐区域之间云形成的差异清楚地表明了土地利用变化影响区域气候的信号。区域大气建模系统的数值建模模拟用于探索低地牧场和森林景观在云场特征方面的差异。在森林和牧场模拟之间，云的基本高度和云的厚度存在统计学上的显着差异。在牧场景观上，云的基本高度更高，并且比森林景观更薄。另一方面，这些模拟显示牧场和森林模拟在云顶高度，云量，平均云水混合比或云液态水路径方面没有统计学上的显着差异。但是，在模拟中，与森林相比，牧场上的感热通量增加，潜热通量减少。牧草表面上较干燥和较热的空气导致形成升高的稀薄云层。这项研究表明，森林砍伐导致蒙得维德云森林的上风偏热，干燥，这可能会影响旱季对该地区至关重要的地形云堤的基础高度。 [参考：47

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