Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation.
Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation.
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DOI：
10.1002/2015ms000564
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发表时间：
2016-03
影响因子：
6.8
通讯作者：
Zadra, Ayrton
中科院分区：
文献类型：
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作者：
Sandu, Irina;Bechtold, Peter;Beljaars, Anton;Bozzo, Alessio;Pithan, Felix;Shepherd, Theodore G.;Zadra, Ayrton
最近由数值试验工作组(WGNE)提出的一项相互比较工作表明，天气预报模式中的参数化或未解决的地面应力高度依赖于模式，特别是在地形上。类似分辨率的模式在陆地上的纬向平均总亚网格表面应力(τTOT)差异高达20%。τTOT在不同参数化之间的划分方式也取决于模型。在这项研究中，我们在一个特定的模型中模拟了τTOT的增加，与WGNE相互比较中发现的差值相当。这种增加是通过两种方式来模拟的，即通过独立地增加湍流地形形式阻力方案和地形低层阻塞方案(BLOCK)对τTOT的贡献。在10天天气预报和季节积分中，增加参数化的地形阻力导致冬季北半球地面气压、纬向风和温度的显著变化。然而，流通中这些变化的幅度在很大程度上取决于修改的方案。在10天预报中，当TOFD强度增加时，变化更大，而在季节性时间尺度上，这种影响的程度与之相当，尽管细节不同。在这些时间尺度上，阻塞方案通过与地面撞击有关的分辨率行星波的变化来影响平流层低层风，而TOFD效应主要局限于对流层低层。τTOT在两个方案之间的分配似乎在所有时间尺度上都发挥着重要作用。参数化地形阻力在所有时间尺度上都影响北半球冬季环流。不同参数化之间的地面应力分配影响环流方面
A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model‐dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress (τtot). The way τtot is partitioned between the different parameterizations is also model‐dependent. In this study, we simulated in a particular model an increase in τtot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τtot of the turbulent orographic form drag scheme (TOFD) and of the orographic low‐level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τtot between the two schemes appears to play an important role at all time scales. Parameterized orographic drag affects the Northern Hemisphere winter circulation at all time scales The partition of the surface stress between various parameterizations affects circulation aspects