Diurnal cycle of surface winds over the subtropical southeast Pacific
Diurnal cycle of surface winds over the subtropical southeast Pacific
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副热带东南太平洋地面风的日循环
DOI：
10.1029/2008jd009957
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发表时间：
2008
影响因子：
--
通讯作者：
R. Muñoz
中科院分区：
文献类型：
--
作者：
R. Muñoz
[1] 东南太平洋表面风的日变化通过 2000-2006 年的 QuikSCAT 数据来表征。每日两次卫星经过发生在 LT 0600 和 1800 左右（分别称为 AM 和 PM）。 PM-AM 风差在南纬 20° 至 30° 之间的区域达到最大，从智利海岸延伸至西经 75°。这种差异主要是经向（沿着海岸）的，季节性变化的特点是夏季晨风减弱。观测分析得到了 2003 年 12 月中尺度模型结果的补充。它们表明，沿海纬向流在当地时间 (LT) 0600 至 1200 之间增加，但随后在接下来的 6 小时内减少，这解释了 QuikSCAT PM-AM 差异中没有陆上成分的原因。额外的模型诊断表明，在该区域，海洋边界层 (MBL) 上方的昼夜周期记录仪比表面更简单且更大。动量和温度预算的评估揭示了垂直速度的昼夜循环与热结构在控制低层风的昼夜循环中的重要性。大约 1300 LT 的海岸沉降在从 36°S 的 1000 m 到 22°S 的 3000 m 的倾斜层中达到最大，从而导致地表形成沿海槽。夜间，高压扰动的通过使地面经向气压梯度力发生逆转，导致沿海经向风减弱。这些结果强调了 MBL 上方的低对流层动力学（例如，安第斯山脉东部的加热）在控制地表附近的风昼夜循环方面发挥的重要作用。
[1] The diurnal variability of surface winds over the SE Pacific is characterized with QuikSCAT data for years 2000–2006. The twice daily satellite passes occur around 0600 and 1800 LT (referred to as AM and PM, respectively). The PM-AM wind difference maximizes in a region between 20°S and 30°S, extending from the Chilean coast up to 75°W. This difference is mostly meridional (along the coast) with seasonal variation characterized by summertime weakening of the morning winds. The observational analysis is supplemented with mesoscale model results for December 2003. They show that the coastal zonal flow increases between 0600 and 1200 local time (LT) but then decreases in the next 6 hours, which explains the absence of an onshore component in the QuikSCAT PM-AM difference. Additional model diagnostics show that in this region the diurnal cycle hodographs are more simple and larger above the marine boundary layer (MBL) than at the surface. Evaluation of the momentum and temperature budgets reveals the importance of the diurnal cycle of vertical velocity coupled with the thermal structure in controlling the diurnal cycle of the low-level winds. Around 1300 LT coastal subsidence maximizes in a layer sloping from 1000 m at 36°S to 3000 m at 22°S, inducing the development of a coastal trough at the surface. During the night the passage of a high-pressure perturbation reverses the surface meridional pressure gradient force, inducing the decrease of the coastal meridional winds. These results stress the important role played by the dynamics of the low troposphere above the MBL (e.g., the heating of the Andes Cordillera to the east) in controlling the wind diurnal cycles near the surface.