转载：微爆气流什么鬼？飞行员为何不愿意招惹它？
飞行员培训
成维纲（微信号：welkinweigang）飞行员/飞机及航材销售本文英文原文由Aleks Udris创作，编译作者为成维纲
微爆气流 形成原因 注意事项共计 2027 字 | 建议阅读时间：8 分钟微爆气流可以将任何飞机从天空中击落，就连喷气机也不例外。现在正值夏季对流天气的中期，在全国各地都增加了危险的几率。
（美国东部航空）微爆气流曾在1975年击落美国东部航空（为行文方便，区别于我国东方航空，Eastern Airlines译为美国东部航空）的班次号为66的航班（727机型）和1985年达美航空的班次号为191的航班（L-1011洛克希德公司的三星客机）。自从发生了这两起事故，微爆气流的监测便开启了它漫长的道路，并且微爆气流危害变成了飞行训练中的标准部分。但微爆气流的影响现在却丝毫没有减弱，大多数轻型飞机所用的小机场没有办法监测微爆气流的存在。所以，它是如何形成的，你将会在哪里碰到它们？
Microbursts have the power to knock any aircraft out of the sky, even jets. And since we're in the middle of summer's convective weather, there's an increased risk everywhere in the US.Microbursts took down Eastern Airlines Flight 66 in 1975 (a 727), and Delta Airlines Flight 191 in 1985 (an L-1011).Since these two accidents, microburst detection has come a long way, and microburst hazards are a standard part of training. But, they're no less of a factor now, and most small airports used by light aircraft have no way to detect a microburst. So, how do they form, and where should you expect them?01它所需要的仅仅是一片积雨云微爆气流仍然是需要投入大量研究的课题，但我们知道差不多任何一片积雨云都可以促使它形成。实际上，甚至不需要雷和闪电。虽然微爆气流可以从气团风暴，飑线和剧烈超级细胞风暴中喷发出来，但孤立的，单细胞风暴将产生最强烈的危害。飞行员通常错误的认为极端天气不会产生在这些常见的风暴里。但如果它们其中的一个迅速发展成微爆气流，它将给你带来主要的问题。
Microbursts are still the subject of considerable research, but we do know that nearly any cumulonimbus cloud can form one. In fact, thunder and lightning aren't even necessary. And while microbursts can erupt from airmass storms, squall lines and severe supercell storms; isolated, single-cell storms may pose the greatest danger. Pilots often (and mistakenly) don't expect severe weather from these common storms. But if one sprouts a microburst, it can cause you major problems.02强降水形成下降气流微爆气流最典型的特点是呈柱状迅速下降的空气，其下降速度可达到每分钟6000英尺（1828.8米）。强降水是罪魁祸首，它通过拖拽和冷却来形成下降气流。当降雨开始，降雨和空气之间的摩擦开始把空气向下拉。同时，干燥的空气开始让雨水蒸发。它从周围空气中的热量吸取能量，将液态的水转化成气体。实际上，当雨水蒸发时它将空气中的热量带走，冷却空气柱。现在柱状体中的雨和空气比周围的大气冷一些。因为冷空气比暖空气密度更高，重量更大所以开始下降。当雨水和空气下落时，雨水持续的蒸发，使得空气变得更冷。下降率加速所以产生微爆气流。
A microburst's signature trait is a column of rapidly descending air, which can fall at 6,000 feet per minute. Heavy precipitation is the culprit here, forming a downdraft through drag and cooling.As rain falls, friction between the rain and air begins to pull the air downward. At the same time, dry air begins to evaporate the rain. It takes energy to turn liquid water into a gas, which comes from the heat in the surrounding air. Essentially, the rain sucks the heat out of the air as it evaporates, cooling the air column.The column of rain and air is now cooler than the surrounding atmosphere. Since cold air is more dense than warm air, it weighs more and begins to descend. As the rain and air fall, the rain continues to evaporate, cooling the air even more. The descent rate speeds up, and you have a microburst.03干的或湿的在潮湿的气候，微爆气流中的降水在到达地面前不会完全的蒸发。这称之为湿微爆气流。然而，在干燥的气候例如科罗拉多或者犹他，所有降水经常在到达地面前蒸发，留下一个看不见的，空气每分钟向下6000英尺（1828.8米）的柱状体。这称之为干微爆气流。在空气中你会看到雨幡，伴随着从微爆气流柱底向外展开的尘土漩涡云。不论微爆气流是湿的还是干的，不管怎样，他们都是危险的。
However, in dry climates like Colorado or Utah, all of the precipitation often evaporates before it reaches the ground, leaving an invisible column of air speeding down at 6,000 feet per minute. These are called dry microbursts. You'll see virga in the air, followed by a swirling cloud of dust spreading out from the base of the microburst column.In humid climates, precipitation may not completely evaporate in a microburst before it reaches the ground. These are called wet microbursts.04向外扩散并且逐渐衰退当微爆气流中柱状空气到达地面，他开始按照圆圈向外扩散并且向上向内卷起，在微爆气流的外边产生一个涡流环。微爆气流很小，通常小于2.5海里宽（约4公里）风速的最高峰值持续时间少于5分钟。许多类似的下爆气流，但通常都叫做微爆气流。微爆气流通常只持续几分钟，通常在前5分钟开始加剧，然后逐渐衰减。多个微爆气流可以并排产生，他们可以按顺序的持续30分钟或更久。
As the column of air in a microburst reaches the ground, it begins to spread out in a circle. It also begins to curl up and in, creating a vortex ring around the outside of the microburst.Microbursts are small, and are officially less than 2.5 nautical miles wide (about 4 kilometers) with peak winds lasting less than 5 minutes. The more generic "downburst" covers wider events, but both are commonly called a "microburst."Microbursts usually last only a few minutes, usually intensi fying in the first five minutes and then dying out. Multiple microbursts can happen in a row, and they can create a sequence that lasts for 30 minutes or more.05低空风切变的经历
如果你要从文章里学到最重要的一点，那便是，所有的微爆气流都是危险的。除了明显的向下气流可以将你推向地面，微爆气流中巨大的风切变可以使你失速，并且加快下降率。这里一步一步的举一个飞越微爆气流的例子。
1. 假设你在以80节（148.1千米/小时）的速度接近一个微爆气流。当你进入到涡流环中，你会遇到湍流并且在遇到逆风时迅速增加你的空速。你将会开始爬升，因为飞机的性能增加了。
2. 当你进入到水平轴中最强烈的部分时，你的空速增加了20节（37.04千米/小时），达到100节（185.2千米/小时）。当你进入到下降气流时你还在保持爬升姿态。
3. 在下降气流的内部，逆风开始转变成顺风。你被下降气流困住并迅速的向地面下沉。你的空速开始降低。
4. 当你离开下降气流，你的顺风迅速增加。切变会使得你的空速在原基础上减少20节（37.04千米/小时）降到60节（111.12千米/小时）。此时你正处于大仰角姿态并且持续下降中。
5. 当你进入到最后的涡流会遇到更多的湍流，这时如果你还没有撞击到地面，你将又开始爬升然后飞离涡流。If you take away one thing from this article, it's that all microbursts are dangerous. Besides the obvious downdraft that could push you into the ground, the massive wind shear across the microburst can cause you to stall, and adds to your descent rate.Here's an example flight through a microburst, step-by-step.1. Imagine you're approaching a microburst at 80 knots. As youenter the vortex ring, you experience turbulence and a rapid increase in airspeed as you pick up a headwind. You start to climb as your performance increases.2. As you enter the strongest part of the horizontal shaft, your airspeed peaks at 100 knots, an increase of 20 knots. You're still climbing as you enter the downdraft.3. Inside the downdraft, your headwind starts to switch to a tailwind. You're caught in the downdraft, sinking quickly toward the ground.Your airspeed begins to decrease.4. As you exit the downdraft, your tailwind increases rapidly. The shear drops your airspeed to 60 knots, which is 20 knots below your original speed. You're at a high angle-of-attack, and still descending.5. You encounter more turbulence as you enter the final vortex. If you haven't already hit the ground, you may begin to climb again as you exit the vortex.06总切变量=双倍的最高风速值虽然在微爆气流中的下降气流已经很危险了，但风切变会显而易见的将状况变得更糟。如果流动的阵风风速峰值在25节（46.3千米/小时），当你飞越微爆气流时则会遇到50节（92.6千米/小时）的切变。那意味着你的空速将会增加大概25节（46.3千米/小时），然后在你飞出（微爆气流）之前迅速的减少50节（92.6千米/小时）。然而，阵风速度可以达到45节（83.34千米/小时）。如果是那样的话，你将会承受90节（166.68千米/小时）的切变，这将是任何飞机都无法安全处置的。
While the downdraft in amicroburst is dangerous on its own, wind shear makes the situation sign if i cantly worse. If the peak gust speeds in the outflow are 25 knots, you'll experience 50 knots of shear as you cross through the microburst. That means your airspeed will increase around 25 knots, then quickly drop 50 knots before you exit.However, gust speeds in the out flow can reach 45 knots. If that were the case, you'd experience 90 knots of shear, which is more than any aircraft can safely handle.07避免微爆气流那么如何保持在微爆气流以外呢？有些机场拥有低空风切变警示系统（LLWAS），终端多普勒气象雷达（TDWR）或者天气系统处理器（WSP）当微爆气流产生时可以监测到。然而这些（设备）通常只能在Charly和Bravo空域的机场才能找到并且为航线飞行服务。如果可以提供这些服务，空管将会提醒你风切边的状态。在一些小的机场，飞行员报告以及通过双眼的观察将是避免微爆气流最好的方法。简而言之，不要飞行在雷暴下方。如果你看到从云中有降雨或者雨幡同时伴有从地面上卷起的尘土，那么做一个微爆气流的飞行员报告并且与其保持距离。同时也要注意精力在其它的飞机上。在美国东部航空66次航班坠机之前，一架DC-8（美国道格拉斯研制的四发动机大型喷气式客机）报告超强风切变并且另外一架美国东部航空的L-1011（三星客机）几近坠毁。美国东部航空的66次航班的机组人员意识到了情况却仍然决定继续进近。
How do you stay out of a microburst? Some airports have Low Level Wind Shear Alert Systems (LLWAS), Terminal Doppler Weather Radar (TDWR), or Weather Systems Process or (WSP), that can detect a microburst as it occurs. However, these are usually only found alarge Class C or B airports that serve airline traffic. If these services are available, ATC will alert you to wind shear conditions.At smaller airports, pilotreports and your eyes are the best way to avoid a microburst. Simply put, don't fly under neath a thunderstorm. And, if you see a rain or a virga shaft descending from a cloud with dust blowing up from the ground, file a pilotreport for a microburst and stay clear.Also, pay attention to other traffic. Prior to Eastern Airlines Flight 66's crash,a DC-8 reported severe wind shear and another Eastern L-1011 nearly crashed. Flight 66's crew was aware of the conditions and decided to continue the approach.08等待它的消散微爆气流的生命周期很短，风速的最高峰值持续仅有5分钟或更短。如果它们是由单细胞风暴产生的，你可以绕行或者延迟你的到达直到风暴消散。如果你见到了一个（微爆气流），等待它消散。穿越或者面对着微爆气流降落将是一个很糟糕的选择。
Microbursts are short lived, with peak winds lasting only 5 minutes or less. If they're caused by a single-cellstorm, you can often divert or delay your arrival until the storm is clear. If you see one, wait it out. Flying through or landing in the face of a microburstis simply the worst option.
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