Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data
Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data
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DOI：
10.5194/angeo-32-1129-2014
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发表时间：
2014-09
影响因子：
1.9
通讯作者：
S. Zhang;Chunming Huang;K. Huang;F. Yi;Yehui Zhang;Yun Gong;Q. Gan
中科院分区：
文献类型：
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作者：
S. Zhang;Chunming Huang;K. Huang;F. Yi;Yehui Zhang;Yun Gong;Q. Gan
抽象。我们扩展了Zhang等人（2013）提出的用于提取中高频重力波（MHGW）的宽谱方法。利用1998-2008年北方92个测站的探空资料，分析了低层大气（2-25 km）MHGW参数的纬向、连续垂直和季节变化特征。波能密度和水平动量通量的纬向和垂向分布及其季节变化与惯性重力波的分布具有相当的一致性。尽管具有一致性，但MHGW具有更大的能量密度、水平动量通量和波浪力，表明MHGW在能量和动量传输以及背景加速中的作用更重要。对于观测到的MHGW，垂直波长通常大于8 km，水平波长在中高纬对流层中部达到峰值。这些特征明显不同于惯性重力波。能量密度和水平动量通量具有相似的纬向季节变化特征：在低纬地区，能量密度和水平动量通量均为半年变化，而在中纬地区，能量密度和水平动量通量均为一年变化，但在高纬地区，能量密度和水平动量通量在对流层中往往呈现一年两个以上的峰值。与惯性重力波相比，导出的固有频率对浮力频率的时空变化更敏感，在所有纬度区域，夏季的固有频率都较高。波长的季节变化较弱，只有在中纬度地区才能观察到明显的年周期。
Abstract. We extended the broad spectral method proposed by Zhang et al. (2013) for the extraction of medium- and high-frequency gravity waves (MHGWs). This method was applied to 11 years (1998–2008) of radiosonde data from 92 stations in the Northern Hemisphere to investigate latitudinal, continuous vertical and seasonal variability of MHGW parameters in the lower atmosphere (2–25 km). The latitudinal and vertical distributions of the wave energy density and horizontal momentum fluxes as well as their seasonal variations exhibit considerable consistency with those of inertial gravity waves. Despite the consistency, the MHGWs have much larger energy density, horizontal momentum fluxes and wave force, indicating the more important role of MHGWs in energy and momentum transportation and acceleration of the background. For the observed MHGWs, the vertical wavelengths are usually larger than 8 km; the horizontal wavelengths peak in the middle troposphere at middle–high latitudes. These characteristics are obviously different from inertial gravity waves. The energy density and horizontal momentum fluxes have similar latitude-dependent seasonality: both of them are dominated by a semiannual variation at low latitudes and an annual variation at middle latitudes; however at high latitudes, they often exhibit more than two peaks per year in the troposphere. Compared with the inertial GWs, the derived intrinsic frequencies are more sensitive to the spatiotemporal variation of the buoyancy frequency, and at all latitudinal regions they are higher in summer. The wavelengths have a weaker seasonal variation; an evident annual cycle can be observed only at middle latitudes.