Effects of land use on the climate of the United States
Effects of land use on the climate of the United States
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DOI：
10.1023/a:1005305708775
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发表时间：
1997-11-01
期刊：
影响因子：
4.8
通讯作者：
Bonan, GB
中科院分区：
文献类型：
--
作者：
Bonan, GB
土地利用方式已经用农作物取代了美国东部的大部分天然针叶常绿林、落叶阔叶林和混交林。在较小程度上，美国中部的天然草原也被农作物取代。陆面过程模式和大气环流模式的耦合模拟表明，美国现代植被和自然植被的气候有很大不同。现代植被造成的三个重要气候信号是：(1)春季美国东部降温1摄氏度，美国西部变暖1摄氏度；(2)美国中部大片地区夏季降温高达2摄氏度；(3)春季和夏季，美国大部分地区近地表大气增湿0.5至1.5克(-1)。尽管由于土地利用方式的不同，个别月份的降水量显示出很大的、在统计上显著的差异，但这些差异在三个月的季节过程中是平均的。地表温度和湿度的这些变化很好地延伸到大气中，最高可达500毫巴，并影响边界层和大气环流。气候变化的原因是与自然植被相比，现代植被的表面粗糙度降低，叶和茎面积指数减小，气孔阻力减少，地表反照率增加。土地利用做法造成的气候变化可与其他众所周知的人为气候强迫相媲美。例如，按照目前观测到的美国夏季变暖的速度，需要100到175年的时间才能抵消森林砍伐带来的降温。夏季硫酸盐气溶胶强迫完全抵消了美国东部的温室强迫。同样，北美森林砍伐的气候效应，加上夏季的大范围降温，进一步抵消了温室效应。
Land use practices have replaced much of the natural needleleaf evergreen, broadleaf deciduous, and mixed forests of the Eastern United States with crops. To a lesser extent, the natural grasslands in the Central United States have also been replaced with crops. Simulations with a land surface process model coupled to an atmospheric general circulation model show that the climate of the United States with modem vegetation is significantly different from that with natural vegetation. Three important climate signals caused by modern vegetation are: (1) 1 degrees C cooling over the Eastern United States and 1 degrees C warming over the Western United States in spring; (2) summer cooling of up to 2 degrees C over a wide region of the Central United States; and (3) moistening of the near-surface atmosphere by 0.5 to 1.5 g kg(-1) over much of the United States in spring and summer. Although individual months show large, statistically significant differences in precipitation due to land-use practices, these differences average out over the course of the 3-month seasons. These changes in surface temperature and moisture extend well into the atmosphere, up to 500 mb, and affect the boundary layer and atmospheric circulation. The altered climate is due to reduced surface roughness, reduced leaf and stem area index, reduced stomatal resistance, and increased surface albedo with modern vegetation compared to natural vegetation. The climate change caused by land use practices is comparable to other well known anthropogenic climate forcings. For example, it would take 100 to 175 years at the current, observed rate of summer warming over the United States to offset the cooling from deforestation. The summer sulfate aerosol forcing completely offsets the greenhouse forcing over the Eastern United States. Similarly, the climatic effect of North American deforestation, with extensive summer cooling, further offsets the greenhouse forcing.