The Controlling Role of Boundary Layer Inertial Oscillations in Meiyu Frontal Precipitation and Its Diurnal Cycles Over China
The Controlling Role of Boundary Layer Inertial Oscillations in Meiyu Frontal Precipitation and Its Diurnal Cycles Over China
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DOI：
10.1029/2018jd028368
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发表时间：
2018-05
期刊：
影响因子：
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通讯作者：
M. Xue;Xia Luo;K. Zhu;Zhengqi Sun;Jianfang Fei
中科院分区：
文献类型：
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作者：
M. Xue;Xia Luo;K. Zhu;Zhengqi Sun;Jianfang Fei
用允许对流模拟方法研究了中国梅雨降水日循环的主要机制。2014年梅雨季的6天用来在江淮流域上空产生一条“北”的合成雨带，另外6天用来产生一条“南”的合成雨带。两个雨带的雨量都在清晨出现峰值，南带的次峰出现在下午。发现低层非地转风(AGW)具有顺时针旋转的日周期和方向，其大小取决于背景地转季风流。进入包围每条雨带的控制体的净水汽通量几乎完全是由于大气环流。两个雨带的净通量均在LST~04时达到最大值，约在早晨降水高峰前3~4h。对于北带，一个显著的极小值出现在~19LST，比最小降水量早4小时。通过南方控制体边界的水汽通量对净通量及其日变化的贡献最大。大气环流的日变化及其与背景季风流的关系与Blackadar边界层惯性振荡理论的预测非常吻合，由惯性振荡引起的环流强迫辐合对梅雨锋降水的日循环起着重要的调制作用，包括产生早高峰和晚极小值。潜热释放的反馈只起到次要作用。普遍认为的季风日变化可以用Blackadar惯性振荡理论来解释。
Convection‐permitting simulations are used to investigate the key mechanism of Meiyu precipitation diurnal cycle over China. Six days from the 2014 Meiyu season are used to produce a “north” composite rainband over the Yangtze‐Huaihe River Basin and another 6 days used to produce a “south” composite band. Both rainbands have peak rainfall in the early morning, while the south band has a secondary peak in the afternoon. Low‐level ageostrophic winds (AGWs) are found to exhibit diurnal cycles with clockwise rotations and their directions, and magnitudes depend on the background geostrophic monsoon flows. Net moisture flux into a control volume enclosing each rainband is almost purely due to AGWs. For both rainbands, net flux reaches maximum at ~04 LST, about 3–4 hr before morning precipitation peak. For the north band, a prominent minimum occurs at ~19 LST, 4 hr before the precipitation minimum. The moisture fluxes through the southern control volume boundary make the largest contributions to the net flux and its diurnal variations. The diurnal variations of the AGWs and their relationship with the background monsoon flows agree very well with the prediction of Blackadar boundary layer inertial oscillation theory, and the convergence forcing by the AGWs resulting from the inertial oscillations plays a paramount role in modulating the diurnal cycles of Meiyu front precipitation, including the creation of early morning peak and evening minimum. Feedback of latent heat release plays only a secondary role. The commonly recognized diurnal monsoon variability can be explained by the Blackadar inertial oscillation theory.