On Sunday, August 21, 2016 at 8:57:59 AM UTC-7, Thomas 'PointedEars' Lahn wrote:
> Michael J. Strickland wrote:
>
> > Thunderheads go to 50-60 thousand feet and they must have some
> > moisture.
> Nonsense. 50'000 to 60'000 ft equal 15.24 to 18.29 km. The troposhere only
> extends up to ca. 12 km altitude from sea level. The adjacent higher
> atmospheric layer of Terra is the stratosphere (from ca. 12 km to ca. 50 km)
> where there are occasionally clouds, but none that (could) contribute to
> precipitation (directly).
The height of the top of the troposphere varies with latitude (it is lowest over the poles and highest at the equator) and by season (it is lower in winter and higher in summer). It can be as high as 20 km (12 miles or 65,000 feet) near the equator, and as low as 7 km (4 miles or 23,000 feet) over the poles in winter.
> > I don't think hail can form only 1000 meters up in hot summer air.
> Correct. But hailstones form when upwinds push water droplets (ca. 200 µm
> in diameter, too small to see individually, therefore clouds) further up the
> cloud, where, due to the low temperatures, they freeze to ice pellets
> (between 200 µm and 5 mm).
This is one theory. But it isn't a very good theory. In my expert opinion the only place the upwinds are strong enough to keep a droplet suspended long enough that it can freeze is on the inside of vortices.
Thomas, you should make an effort to not be gullible and pedantic. The reality is nobody exactly knows.
Being too heavy to be held in suspension by
> upwinds, they fall down again, where more water can condense on them, and
> they are pushed up again, where that water freezes on. And so on until the
> pellets are too heavy even in the lower parts of the cloud (or the upwinds
> slow down due to insufficient convection), when they finally fall out of the
> cloud.
There is no convection in earth's atmosphere. It is little more than an often repeated urban myth.
It's stories meteorologist tell themselves. It's not empirical science.
>
> While hailstones do form in cumulonimbus clouds that extend up to 12 km
> altitude, you are neglecting the basic physical fact that the air does not
> stay “hot” at higher altitudes: as it rises, it cools. In 3 km altitude and
> above, so in the *lower* part of a cumulonimbus already, the air temperature
> is already below 0 °C – low enough for water to freeze – even in summer.
>
> <
https://upload.wikimedia.org/wikipedia/commons/9/9d/Comparison_US_standard_atmosphere_1962.svg>
> > Water vapor rises because water (H2O at 18 grams/mole) is less dense
> > than air which is predominately nitrogen (N2 at 28 grams/mole). When
> > mixed with regular air (non-moist), this brings the air's
> > average/overall density down and causes it to rise above non-moist
> > air.
> Nonsense. Air contains about 1 % of water which is gaseous (water vapour)
> under standard conditions.
Like you have a clue. There is no gaseous H2O in the earth's atmosphere. It is far too cool to support the existence of gaseous H2O. Look at an H2O phase diagram.
> It is not the water vapour in the air alone that
> rises, but warm air with water vapour in it.
>
> When it cools, only the water in the air condenses (on condensation nuclei,
> small dust particles in the air, ca. 0.2 µm in size) and freezes; more water
> condenses and freezes on that, to form ice crystals and eventually ice
> pellets.
>
> It does that because the boiling and melting point of water is significantly
> higher (100 °C and 0 °C under standard conditions, respectively) than that
> of the other constituents of air – given the same atmospheric pressure that
> is decreasing approximately exponentially with altitude within the higher
> troposphere:
This is gibberish.
> p ≈ p₀ exp(−g M h∕(R T₀))
>
> where
>
> p – atmospheric pressure
> p₀ – standard atmospheric pressure at sea level (101'326 Pa)
> g – Earth-surface gravitational acceleration (ca. 9.81 m∕s²)
> M – molar mass of dry air (ca. 0.03 kg∕mol)
> h – altitude
> R – universal gas constant (ca. 8.31 J mol⁻¹ K⁻¹)
> T₀ – standard temperature at sea level (288.15 K = 15 °C)
Completely irrelevant.
James McGinn / Genius