Meridional movement of geopotential height anomalies in the subtropics and the relationship to the base‐state flow,Quarterly Journal of the Royal Meteorological Society

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Meridional movement of geopotential height anomalies in the subtropics and the relationship to the base‐state flow
Quarterly Journal of the Royal Meteorological Society ( IF 3.0 ) Pub Date : 2020-10-18 , DOI: 10.1002/qj.3937
Jennifer Gahtan ₁ , Paul E. Roundy ₂

Affiliation

Qualities of the meridional movements of geopotential height anomalies in the upper troposphere of the subtropics are analysed via wavelet analysis using a meridional–temporal partial Morlet wavelet. Results show that power, which represents increased presence or amplitude of waves with direct meridional movement, is increased in regions where the corresponding equatorial winds in the upper troposphere are westerly or weakly easterly. Furthermore, equatorward power is enhanced near subtropical jet exit regions whereas poleward power is enhanced in jet entrance regions. Regressions of upper‐tropospheric winds, geopotential height, and outgoing long‐wave radiation (OLR) against the wavelet transforms demonstrate that the wavelets are identifying signals with tropical–extratropical interactions that are connected to organized convection in the tropics. The relationship of power with background‐state flow characteristics, including the horizontal winds and shear, are evaluated. Instead of the zonal wind and meridional shear of the zonal wind (du/dy), both the meridional wind and the zonal shear of the meridional wind (dv/dx) appear to have a clearer relationship with the power. Power is favoured for waves whose movement is aligned in the same direction as the meridional wind, and reduced in the opposite direction. Additionally, power increases with increasing zonal shear of the meridional wind in the Northern Hemisphere and with decreasing zonal shear of the meridional wind in the Southern Hemisphere. Power in the equatorward direction is stronger than in the poleward direction and more heavily influenced by background flow characteristics. Furthermore, power for wavelets with smaller meridional and temporal scales tends to have a higher sensitivity to the background horizontal flow as compared to larger meridional and temporal scales.

中文翻译：

亚热带地势高度异常的子午运动及其与基态流的关系

通过使用子午-时空部分Morlet小波的小波分析，分析了亚热带对流层上层高度势异常的子午运动的质量。结果表明，在对流层上层的相应赤道风为西风或弱东风的区域，功率增加了，表示随着子午线运动的出现，波的振幅也增加了。此外，在亚热带喷流出口附近，赤道功率增加，而在喷流入口区域，赤道功率增加。对流层上风的回归，地势高度，以及针对小波变换的外向长波辐射（OLR）证明，小波正在识别具有热带与热带关系的信号，这些信号与热带的有组织对流有关。评估了功率与背景状态流动特性（包括水平风和切变）之间的关系。代替纬向风和纬向风的子午切变（du / dy），子午风和子午风的纬向切变（dv / dx）似乎与权力有更清晰的关系。对于波的运动在与子午风相同的方向上排列并在相反的方向上减小的波来说，功率是有利的。另外，功率随着北半球子午风纬向切变的增加和南半球子午风纬向切变的减小而增加。赤道方向的功率比极方向的功率强，并且受背景流动特性的影响更大。此外，与较大的子午线和时间尺度相比，具有较小子午线和时间尺度的子波的功率倾向于对背景水平流具有更高的灵敏度。

更新日期：2020-10-18

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