Hot answers tagged atmospheric-science
13
If you were to surround the atmosphere by an adiabatic envelope and allow it to come to equilibrium, it probably would settle into such a state. However, the atmosphere is not a static place. It is actively mixed due to heating of the ground by the sun, and by cooling of the upper atmosphere by radiation into space. This makes the surface air less dense than ...
8
Temperature generally gets cooler as you go higher in altitude (which is one reason why you have snow on mountain peaks long after it has melted away in the foothills).
Hail develops in thunderstorms. A thunderstorm ~BY DEFINITION~ is a storm which has developed through the freezing layer. So think about this: If you see lightning or hear thunder from ...
6
The evidence for global warming is from the known heat-trapping dynamics of the atmosphere. The atmosphere opaquely rescatters infrared light according to the density of CO2, methane, and H2O, so that as each of these gasses increase in concentration, the atmosphere heats up. The coefficient which determines how much the temperature goes up can be estimated ...
6
From the Wikipedia article:(My emphasis)
Some people thought that the ozone hole should be above the sources of CFCs. However, CFCs are well mixed globally in the troposphere and the stratosphere. The reason for occurrence of the ozone hole above Antarctica is not because there are more CFCs concentrated but because the low temperatures help form polar ...
5
In general, yes the updrafts also occur in warm dry air, as a result of heating on the ground which produces hyrdostatic instability in the atmosphere. As the updrafts go higher, they cool adiabatically and may, if they go high enough and if there is enough moisture in the air, cool enough to condense water vapor and form clouds. However there can also be ...
4
Logarithmic profile for wind speed regards the bottom part of atmospheric boundary layer (say, about the bottom 100 m, on a boundary layer about 1000 m high). It can be deducted doing some non obvious but reasonable assumptions.
A) Vertical flux of horizontal momentum due to turbulence must be uniform in the lowest part of the atmosphere. Let's consider a ...
4
From [The ASCE Standardized Reference Evapotranspiration Equation]1
Given T is temperature in degrees Celsius, and RH is relative humidity:
Saturation Vapor Pressure (es) =
0.6108 * exp(17.27 * T / (T + 237.3))
Actual Vapor Pressure (ea) =
RH / 100 * es
Vapor Pressure Deficit =
ea - es
Why this is a meaningful measurement: "The strain under which ...
4
The greenhouse effect is well-established science, and experiments that demonstrate the effect on a lab scale are common to the point that they are often presented in science fairs. When I say "greenhouse effect" in this context, I'm referring to the radiative trapping of heat by absorption of outgoing radiation by gases. As has been pointed out on Physics ...
3
Climate modelling is a giant science of its own, and the proportion of CFD/statistics depends on the particular model.
In general, what models do is first a simple (often uncompressable) large-scale CFD to advect the scalar fields and then apply a bunch of subrutines simulating small scale and more complex processes, like radiation transfers, heat transfers, ...
3
Ultimately, the power source can be traced back to the sun. This supplies the heat energy to cause the atmospheric movements which give rise to the charge separation in Jack's answer.
I don't think it's feasible to do it artificially the same way (charge separation on water droplets/ice crystals). You would need an environmental chamber of size of the ...
3
I would not claim to understand what precisely is going on here, but other things remnaining constant, mathematically you have:
$$\lim_{L \rightarrow 0} \quad p_0 \cdot \left(1 - \frac{L \cdot h}{T_0} \right)^\frac{g \cdot M}{R \cdot L} = p_0 \cdot \exp \left( - \frac{ h \cdot g \cdot M}{T_0 \cdot R} \right)$$
3
Mirages are a visible effect of the inhomogeneous, temperature-dependent refractive index of air. They're visible because of the relatively large heat gradient close to the earth's surface, and the excellent reference line provided by a uniform, flat horizon. I think those conditions would be difficult to replicate in-flight - perhaps you could have a drone ...
3
Air of different temperature and pressure has different refractive index - but the difference is very small.
If you think of putting a piece of glass into water and trying to see it. The difference between glass (1.5) and water (1.33) is pretty large, air at different temperatures has refractive index differences of parts-per-million
Astronomers at least ...
3
There's always a reason although for different weather fronts, the discussion has to be different.
Different densities have to have a reason - different pressure and/or humidity etc. If there is a different pressure, there is a mechanical force the preserves the pressure difference: think about the cyclones that have a lower pressure in the center. The ...
2
I don't think there is anything wrong, but depending on the application you should consider studying a more complex dynamics. Consider how much water enters your system (per unit of time) and how much is drained.
You see that 1 meter of water in 1 square meter sounds a lot! but if it's in a period of one week then the water will probably drain or evaporate ...
2
Lets put it another way though @user1631 is correct :
There are convective movements in the atmosphere due to non uniform absorption of heat and release of energy through radiation due to ground formations ( ocean, land, mountain, desert), altitude, latitude, Coriolis forces, atmospheric tides etc. Generally air will move from hot to cold generating high ...
2
To make things simple you want to compare two atmospheres that are identical, except that one has infinitessimally more of some IR absorber. In the second case, some IR photons that were traveling upwards are absorbed, and thermalized (i.e. the energy is transferred to the surrounding gas molecules, before being re-emitted). The IR photons are basically ...
2
Water vapor inside clouds condenses into droplets that fall trough the cloud. If the cloud has sufficient up drafts then the droplet or crystal, if it's cold enough, will rise through the cloud gaining more mass before finally it becomes too heavy and the up draft is no longer neough to prevent it from falling out of the cloud. In extreme cases this can lead ...
2
You need to distinguish between the greenhouse effect, which is well established, and anthropogenic global warming, which is rather more controversial.
The greenhouse effect is due to gases like water vapour and carbon dioxide that allow visible light to pass through them but scatter infrared light. This causes the planet to warm up just like a greenhouse ...
2
X rays have a short wavelength. Imagine a road covered with pingpong balls. Try to roll a marble across, and it will most probably bounce back and forth amongst the balls, and eventually stop without getting to the other side. Now try a soccer ball. These will cross almost all the time. And now a truck. I doubt that you will find a situation where these ...
2
I wasn't going to answer, since this is a duplicate, but I saw these clouds on the way to work and since they are relevant for the question I thought I'd post them.
Look closely at the clouds and you'll see their bottoms are flat. That's because they are being shaped by air currents (thermals) rising from below the clouds. The average density of a cloud ...
2
It most likely is a cosmic phenomenon more commonly known under the name "sunrise".
Quoting this page http://www.bom.gov.au/australia/radar/about/radarfaq.shtml)
"Near sunrise and sunset the radar antenna momentarily scans the sun. On occasions this can be seen as a pencil line radiating out from the centre of the image in the direction of the sun."
I ...
2
Certainly. Any time there is a temperature gradient, air will move. Altitude doesn't matter (from the standpoint of existence, the speeds possible are different based on air density).
Numerous papers investigate both what causes winds in the mesosphere as well as what effects these winds have on various atmospheric formations.
2
The flight actually took 25 minutes, the video you linked to is edited down, and the later stages of it look pretty turbulent. I'd guess it was the shaking that eventually broke off the chair leg, possibly due to metal fatigue. Note that the leg broke off after the balloon had burst and while the chair was falling back to Earth.
As Anna says, the low ...
2
I can't point to a definitive reference, but my recollection is that thunderstorms are associated with a lower layer of warm air rising rapidly through an upper layer of cold air. It's the rapid vertical transport that generates the static charge and hence the lightening. In winter it's rare to get these atmospheric conditions.
So it's not that there's ...
1
I would put it down to coincidence: a cloud to cloud bolt concurrent with a cloud to earth bolt.
Have a look at this, where branching is also seen. Do not forget that in cloud to ground, a bolt starts from the ground.
Or this one, which shows following two branches in cloud to cloud:
1
The first process in the generation of lightning is the forcible separation of positive and negative charge carriers within a cloud or air. The mechanism by which this happens is still the subject of research, but one widely accepted theory is the polarization mechanism. This mechanism has two components: the first is that falling droplets of ice and rain ...
1
Like almost everything that is not nuclear on earth the energy comes from the Sun.
Its possible some tiny amount of unused chemical energy still exists from the formation of the earth. Its hard to know since everything gets renewed from the Sun.
Either way, all our weather is powered by the Sun. Without it we would be a deep frozen planet with no weather.
...
1
I suppose what you want is the graph at http://en.wikipedia.org/wiki/Radio_window, provided you are talking about vertical transmission from space to the earth's surface. Results would presumably be different for horizontal transmission because the pressure and chemical composition of the atmosphere would be much closer to constant, but I can't immediately ...
1
I would like to add a few points to the other answer. The question could be taken to be asking why the Earth's atmosphere consists of the thermodynamic equivalent of "domains". That is why are there different regions (of homogeneous parameter values) with discontinuities between those regions? These regions here being the "air masses" - defined as having a ...
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