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我怎么解释为什么青藏高原在类似的纬度比低地冷吗?

一个常见的门外汉解释为什么它让寒冷的高海拔(只考虑这里的对流层)定性归结为太阳加热地球表面和地球表面加热大气。我记得,每次我听到或读这个解释还是个孩子的时候,我想:为什么是青藏高原还比在同一纬度低地冷吗?毕竟,太阳能到达表面在西藏。显然有更多。

考虑的话从量子物理学讲师你只有真正理解什么在你教的两倍这样,我措辞问题:如何解释,门外汉来说,为什么青藏高原在类似的纬度比低地冷吗?

回答

你是正确的,在青藏高原太阳能输入将在海平面一样的位置在同一纬度。你也是正确的,太阳加热地球表面,加热大气。现在剩下的细节。反照率反照率是一个衡量的“白”,给了我们一个了解太阳能辐照度与地球。你可能知道深色时,事情往往会变得很热的太阳,而浅色对象不得到热。这是因为当一个来自太阳的光子撞击地球,这是吸收或散射。没有进入辐射的动态,我就离开这黑暗的颜色往往倾向于散射光吸收和颜色。现在我们翻译这个反照率,高价值的“白”是指太阳能输入被反射回大气中;低价值意味着太阳能输入被吸收。森林或海洋低反照率。 Snowpack and ice will have high albedo. However, the albedo in Tibet on average is only slightly higher than average (~0.35 as cited in the comments below) and so this effect is limited with only a slight decrease in absorbed solar radiation than average. - Absorption The solar input that is absorbed in Tibet will excite the molecules in the ground and they will respond by warming up (and emitting longwave radiation). The emitted radiation upward does nothing to the air temperature, only the greenhouse gases are good at absorbing these wavelengths, regular dry air is not. It is notable that at these altitudes will also be less water vapor, which is probably the best greenhouse gas. If radiation isn't going to warm the air, that leaves conduction and convection. - Conduction The Earth heats the atmosphere via conduction with the lowest level of molecules in the atmosphere. For conduction to happen, molecules need to touch. At the lower pressures at high altitude, there are less molecules of air and conduction will be less efficient than at lower altitudes. - Atmosphere Air getting up to the Tibetan Plateau will have blown in, already at high altitude, or it will be blown upslope from lower elevations. In either case, this air will tend to be cold and dry. Upslope flow will tend to cool around 6C/km until it dries out (rain, clouds) and then cool at 10C/km. For the air already at altitude, the average elevation of Tibet is around 580 hPa and the standard temperature at that pressure is -14 C. Of these two effects, cool air advection of air already at this altitude dominates over upslope adiabatic flow . This air at altitude tends to move faster than at the surface and you will have a constant flow of new incoming, cold air blowing over the surface of Tibet. Putting it all together: The slightly higher albedo is our first suspect as to why Tibet is colder than lower elevations at the same latitude -- more of the sunlight is reflected to space and does not contribute to warming the ground. The next suspect is the less efficient heating of the atmosphere by the surface. This is followed up by the atmosphere that is already much colder than the surface at sea level (at similar latitudes). Take a much colder airmass than sea level, heat it up less than at sea level and you end up colder than you would be at sea level.

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\ begingroup美元一些思想;根据Peixoto和奥尔特、物理气候,图6.10,反照率有点但不是西藏,更高(撒哈拉0.3,西藏0.35,冰盖0.8)。至于更少的空气分子;是的,但是需要按比例减少能源热分子。我认为关键问题是风和缺乏水蒸气(这意味着即使wind-sheltered谷不加热)。 \ endgroup美元
- - - - - -gerrit ♦
2014年4月16日18:07
\ begingroup美元这是一个干净、容易理解的解释。好了!我认为这将是完美的答案,如果强调冷却的大部分是由于冷却空气平流与绝热冷却(想想清凉的空气体积的运输由每个),尽管绝热冷却无疑是相关的。 \ endgroup美元
- - - - - -DrewP84
2014年4月18日19:46
\ begingroup美元 @gerrit是正确的,反照率并不像你想象的一样重要了。高原雨(雪)跟踪的喜马拉雅山脉的大部分。西藏的卫星图像。 \ endgroup美元
- - - - - -DrewP84
2014年4月18日19:53
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\ begingroup美元 @DrewP84我犯了一个编辑不再强调反照率效应和替换他们强调空气平流降温。 \ endgroup美元
- - - - - -凯西
2014年4月18日20:17

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