背风

Rotaing and stratified flow ; Rotating experiments ; Lee wave and lee eddies

旋转层结流；转槽实验；背风坡与背风涡旋

Then, the fronts .of different intensities are superposed on the orographic disturbances and pushed by basic geostrophic flow to climb over the orography.

通过非静力模式讨论了两维地形扰动与锋面的相互作用，研究了不同基本气流，包括正压、斜压、层结强弱差异，不同尺度的地形，包括不同高度和不同宽度，强弱不同的锋面等多种情况下地形扰动与锋面扰动的相互影响，发现地形尺度和气流的性质不同带来的结果是有差异的，中尺度地形使冷锋在迎风坡锋消，在背风坡则是锋生和锋消相间的波状分布，表现为锋面在山顶附近锋生、快速下坡过程中锋消和山脚处锋生的分布特征，这与半地转模式中地形的动力作用使冷锋在背风侧单纯加强是不同的。

The results show that a separate dunk is observed near the stagnation point of the second sphere on the distance of spheres L≤2.5D because of the influence of reverse pressure gradient.

结果表明：当L≤2.5D时，由于逆压梯度的影响，在第二个圆球滞止点附近捕捉到附体分离泡；由于第二个与第三个圆球的置入，展向压力梯度诱发第一个圆球背风面流动的展向输运，且随着圆球间距的增加流场的展向输运趋势减小，但涡的强度增大；第二个圆球与第三个圆球背风面流动没有明显的展向输运；湍动能的增量与圆球间距近似成平方规律。

Conditions for maintenance of reticulate dune morphology under modern flow environment include enough space for the development of secondary ridges on the primary ridges in order that the overall pattern can not be modified by the subdominant winds, and sufficient amount of sand supply for the secondary ridges that can withstand the dominant winds.

在背风坡，因原始气流方向、强度和沙丘背风坡形态等的不同出现弱的反向气流，相对强的附体未偏向流和附体偏向流等三种特征次生气流，它们控制着背风坡表面过程、沙丘移动性质、内部层理类型和产状。

The results showed that the flow reattachment distance in the lee side of various dune models are ranged from 4.8H to 10.8H depending on different stoss slopes, the maximum of flow reattachment distance was found in the lee side of the transverse dune with a 15° stoss slope angle.

实验结果表明，当来流风速垂直于沙丘脊线时，沙丘背风侧的气流重附距离介于4.8H～10.8H之间，最大重附距离出现在迎风坡坡度为15 的沙丘背风侧；沙丘迎风坡坡度是控制背风侧气流重附距离的主要因素，而自由风速对气流重附距离的控制作用较小。

The field experiments on the secondary flow developed on the lee side show that there are strong sand transport potential at the lee side of the dunes near the surface because of the decreasing of the sand grain size and the other factors. The transport directions are nearly vertical to the dune trends. Those factors and the sand slumping on slip face, and the sand transport processes on the stoss slope make the transverse dunes maintaining their morphology under the advance processes.

对沙丘背风坡发育的二次流的野外观测表明，近地面一定高度内沙丘背风坡气流仍有一定的强度，由于背风坡的沙丘沙粒径较小等因素，背风坡气流仍保持一定强度的输沙率，输沙方向与沙丘走向基本上垂直，这种作用与沙物质向背风坡崩落、迎风坡的输沙过程等共同作用，因而使横向沙丘在运动中保持其形态。

In addition, the definition of characteristic air velocity is presented and the relationship between meteorological parameter and air inlet flow field at unwindy weather are discussed.

除了在180°的背风面区域附近，进风口各点的进风速度与侧风速度为二次多项式关系；而在180°的背风面区域附近，进风速度与侧风速度为Gauss分布关系。

The width effects of dune are studied and the reason that the barchan dune is formed on the lee slope of dune is given.

但对于背风坡形状的形成，特别是对新月形沙丘，这样一种沙漠、戈壁上最常见的相对稳定的横向沙丘的背风坡新月形落沙坡的形成和保持，无有完整的理论分析，只是简单地认为其坡度不能大于沙子的摩擦角而已。

The density of the foot 、middle part and top are 124grain /m~2、91 grain /m~2、66 grain /m~2,the seeds is more little windward than the leeward.The density of seed banks in windward is 81grain/m~2 and the leeward density is 100grain/m~2.The seed of ephemerals bourgeoning reaches the pinnacle on April and May.The diversity of different parts sand dune is different,but the differences do not reach the marked level.The similarity is high between the seed banks and the vegetation.

迎风坡种子库密度比背风坡面少，迎风坡种子库平均密度为81粒/m2，而背风坡种子库平均密度为100粒/m2；短命植物种子在4月上旬达到萌发高峰，沙丘不同部位物种多样性存在差异，土壤种子库和地上植被存在较高的相似性，此外短命植物在沙丘不同部位的分布存在较高的空间异质性。

What we need for thermals to form are differences in the air temperature.

每一个滑翔学校都教育学生不要去背风面飞行--&背风面永远充满了危险。&

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。