Eolian processes and heterogeneous dust emissivity during the 1930s Dust Bowl Drought and implications for projected 21st-century megadroughts
Eolian processes and heterogeneous dust emissivity during the 1930s Dust Bowl Drought and implications for projected 21st-century megadroughts
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DOI：
10.1177/0959683617702235
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发表时间：
2017-04
期刊：
影响因子：
--
通讯作者：
K. Bolles;S. Forman;Mark Sweeney
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文献类型：
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作者：
K. Bolles;S. Forman;Mark Sweeney
20世纪30年代美国大平原的沙尘暴干旱是一场环境危机，农业系统失败，景观剥蚀和大气粉尘负荷升高。不良的农业实践被认为是引发广泛的风沙侵蚀和粉尘排放增加的原因，但这一假设受到质疑。本研究分类的土地表面变化在西南堪萨斯从1936年和1939年采取的航空影像，以推断survival过程，灰尘来源，和相关的发射率。总之，七个独特的表面类被确定从光谱反射率值连接到表面植被覆盖和风沙活动的ArcGIS分析，表现出显着的异质景观响应干旱。地层学研究表明，在20世纪30年代以前的亚热带粉质土壤表面受到侵蚀的地方，风成沙的堆积高达4米。潜在的灰尘发射率估计颗粒物来自分类的陆地表面的分布和经验关系，在美国西部类似的灰尘排放表面。超过60%的总悬浮颗粒在1939年被推断为来自未开垦的桑迪表面和风成地貌的研究区域内，与人类修改的表面的其余部分。在研究区域，风速超过6 m s−1的单一沙尘事件的PM2.5和PM10发射率估计值分别为510-4514和4700- 41，607 µg m−3 d−1，与目前北非和东亚的沙尘暴事件相似。干旱频率预计将在21世纪后期增加，可能比沙尘暴更严重，并可能与大气尘埃负荷的幅度增加有关。
The 1930s Dust Bowl Drought on the US Great Plains was an environmental crisis with failure of agricultural systems, landscape denudation, and elevated atmospheric dust loads. Poor agricultural practices were implicated for triggering widespread eolian erosion and heightened dust emissions, but this assumption is called into question. This study classified land surface changes in southwest Kansas from aerial images taken in 1936 and 1939 to infer surficial processes, dust sources, and associated emissivity. In total, seven distinctive surface classes were identified from an ArcGIS analysis of spectral reflectance values connected to surface vegetation cover and eolian activity, demonstrating a strikingly heterogeneous landscape response to the drought. Stratigraphic studies indicate accumulation of up to 4 m of eolian sand in places with erosion of a subjacent silty pre-1930s soil surface. Potential dust emissivity estimates for particulate matter were derived from the distribution of classified land surfaces and from empirical relations on analogous dust-emissive surfaces in the western US. Over 60% of total suspended particles in 1939 were inferred to be derived from uncultivated sandy surfaces and eolian landforms within the study area, with the remainder from human-modified surfaces. The PM2.5 and PM10 emissivity estimates for a single dust event with winds over 6 m s−1 in the study area were 510–4514 and 4700–41,607 µg m−3 d−1, respectively, similar in magnitude to current dust storm events from North Africa and East Asia. Drought frequency is forecast to increase in late 21st century, potentially with greater severity than the Dust Bowl and may be associated with magnitude increase in atmospheric dust loads.