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首页> 外文学位 >Impact of land surface vegetation change over the La Plata Basin on the regional climatic environment: A study using conventional land-cover/land-use and newly developed ecosystem functional types.
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Impact of land surface vegetation change over the La Plata Basin on the regional climatic environment: A study using conventional land-cover/land-use and newly developed ecosystem functional types.

机译：拉普拉塔盆地上的地表植被变化对区域气候环境的影响：一项使用常规土地覆盖/土地利用和新开发的生态系统功能类型的研究。

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摘要

Naturally occurring or human induced changes in land surface vegetation have been recognized as one of the important factors influencing climate change. The La Plata Basin in South America has experienced significant changes in structural land-cover/land-use types, and those changes can involve changes in the surface physical properties such as albedo and roughness length, evapotranspiration, infiltration, and water storage eventually affecting the development of precipitation and the hydroclimate of the basin.;In this study, the Weather Research and Forecast (WRF) modeling system was employed to investigate the role of changing land surface conditions in the La Plata Basin. For this purpose, ensembles of seasonal simulations were prepared for a control case and two extreme land cover scenarios: the first one assumes an expansion of the agricultural activities and the second one assumes a "natural" vegetation cover where no croplands are present.;An extreme anthropogenic land-cover change-simulating an extensive agricultural practice- implies that the northern part of the basin, where croplands replace forests and savannah, would experience an overall increase in albedo and reduced surface friction. The two changes lead to a reduction of sensible heat and surface temperature, and a somewhat higher evapotranspiration due to decreased stomatal resistance and stronger near-surface winds. The effect on sensible heat seems to dominate and leads to a reduction in convective instability. The stronger low level winds due to reduced friction also imply a larger amount of moisture advected out of the basin, and thus resulting in reduced moisture flux convergence (MFC) within the basin. The two effects, increased stability and reduced MFC, result in a reduction of precipitation. On the other hand, the southern part of the basin exhibits the opposite behavior, as crops would replace grasslands, resulting in reduced albedo, a slight increase of surface temperature and increased precipitation. Notably, the results are not strictly local, as advective processes tend to modify the circulation and precipitation patterns downstream over the South Atlantic Ocean.;A newly developed land surface classification, so-called Ecosystem Functional Types (EFTs, systems that share homogeneous energy and mass exchanges with the atmosphere), is implemented in the WRF model to explore its usefulness in regional climate simulations of surface and atmospheric variables. Results show that use of the EFT data improves the climate simulation of 2-m temperature and precipitation, making EFTs a good alternative to land cover types in numerical climate models. An additional advantage of EFTs is that they can be calculated on a yearly basis, thus representing the interannual variability of the surface states. During dry years the 2-m temperature and 10-m wind are more sensitive to changes in EFTs, while during wet years the sensitivity is larger for the 2-m water vapor mixing ratio, convective available potential energy, vertically-integrated moisture fluxes and surface precipitation. This indicates that the impact of land-cover and land-use changes on the climate of the LPB is dependent not only on the wetness of the year, but also on the meteorological or climate variables. Comparisons with observations show that the simulated precipitation difference induced by EFT changes resembles the overall pattern of observed precipitation changes for those same years over the LPB. In the case of the 2-m temperature, the simulated changes due to EFT changes are similar to the observed changes in the eastern part and the southern part of the basin (especially in Uruguay), where the strongest EFT changes occurred.
机译：自然发生或人为引起的陆地表面植被变化已被认为是影响气候变化的重要因素之一。南美洲的拉普拉塔盆地的结构性土地覆盖/土地利用类型发生了重大变化，这些变化可能涉及地表物理特性的变化，例如反照率和粗糙度长度，蒸散量，入渗量和储水量，最终影响了本研究中，采用了天气研究与预报（WRF）建模系统来研究拉普拉塔盆地地表条件的变化。为此，为控制案例和两个极端土地覆盖情景准备了季节性模拟的合奏：第一个假设农业活动的扩大，第二个假设不存在耕地的“自然”植被覆盖；人为的极端土地覆盖变化模拟了广泛的农业实践，这意味着该流域的北部地区（农田取代了森林和热带稀树草原）将反照率总体增加，地表摩擦减小。这两个变化导致显热和表面温度的降低，以及由于降低的气孔阻力和更强的近地面风而导致的蒸散量更高。对显热的影响似乎占主导地位，并导致对流不稳定性的降低。由于减小的摩擦而产生的更强的低空风也意味着大量的水分从盆中涌出，从而导致盆内的水气通量收敛（MFC）减少。稳定性的提高和MFC的降低这两种作用导致了沉淀的减少。另一方面，盆地南部表现出相反的行为，因为农作物将取代草原，导致反照率降低，地表温度略有升高和降水增加。值得注意的是，由于对流过程往往会改变南大西洋下游的环流和降水模式，因此结果并非严格地局限性;一种新近开发的陆面分类，即所谓的生态系统功能类型（EFTs），共享均质能量和WRF模型中实现了与大气的质量交换），以探索其在地表和大气变量的区域气候模拟中的有用性。结果表明，利用EFT数据可以改善2 m温度和降水的气候模拟，从而使EFT成为数字气候模型中土地覆盖类型的良好替代方案。 EFT的另一个优点是，它们可以每年计算一次，因此代表了表面状态的年际变化。在干旱年份，2米温度和10米风对EFT的变化更敏感，而在潮湿年份，对于2米水蒸气混合比，对流可用势能，垂直积分的湿通量和表面沉淀。这表明，土地覆盖和土地利用变化对LPB气候的影响不仅取决于一年的湿润程度，而且还取决于气象或气候变量。与观测值的比较表明，由EFT变化引起的模拟降水差异与LPB相同年份观测到的降水变化的总体模式相似。在温度为2米的情况下，由EFT变化引起的模拟变化类似于在盆地东部和南部（特别是在乌拉圭）观测到的变化，其中EFT变化最大。

著录项

  • 作者

    Lee, Seung-Jae.;

  • 作者单位

    University of Maryland, College Park.;

  • 授予单位 University of Maryland, College Park.;
  • 学科 Climate Change.;Meteorology.;Atmospheric Sciences.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 170 p.
  • 总页数 170
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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