Sentences with phrase «net upward force»

The pressure difference above and below the wing creates a net upward force, giving the aircraft lift.

Not exact matches

Before allowing the temperature to respond, we can consider the forcing at the tropopause (TRPP) and at TOA, both reductions in net upward fluxes (though at TOA, the net upward LW flux is simply the OLR); my point is that even without direct solar heating above the tropopause, the forcing at TOA can be less than the forcing at TRPP (as explained in detail for CO2 in my 348, but in general, it is possible to bring the net upward flux at TRPP toward zero but even with saturation at TOA, the nonzero skin temperature requires some nonzero net upward flux to remain — now it just depends on what the net fluxes were before we made the changes, and whether the proportionality of forcings at TRPP and TOA is similar if the effect has not approached saturation at TRPP); the forcing at TRPP is the forcing on the surface + troposphere, which they must warm up to balance, while the forcing difference between TOA and TRPP is the forcing on the stratosphere; if the forcing at TRPP is larger than at TOA, the stratosphere must cool, reducing outward fluxes from the stratosphere by the same total amount as the difference in forcings between TRPP and TOA.

If it reverses, we can treat the value at the point of reversal (marking a maximum height or depth of the hill or valley in the net upward flux spectrum) as the saturation value, and then include some additional effect at the center of the band for additional increases in CO2 that have the opposite sign as the band widenning in their contributions to radiative forcing.

In the most general sense, upper atmospheric cooling is a response to a forcing (reduction in net upward LW + SW radiation) that falls with height through the upper atmosphere.

Radiative forcing RF at a level is equal to a decrease in net upward flux (either SW, LW, or both; the greenhouse effect refers to LW forcing) at that given level, due to a change in (optical) properties, while holding temperatures constant.

What could hypothetically happen if a very large change in GHG amount / type is made, is that the forcing could increase beyond a point where it becomes saturated at the tropopause level at all wavelengths — what can happen then is that the equilibrium climate sensitivity to the nearly zero forcing from additional GHGs may approach infinity, because in equilibrium the tropopause has to shift upward enough to reach a level where there can be some net LW flux up through it.

(Note that radiative forcing is not necessarily proportional to reduction in atmospheric transparency, because relatively opaque layers in the lower warmer troposphere (water vapor, and for the fractional area they occupy, low level clouds) can reduce atmospheric transparency a lot on their own while only reducing the net upward LW flux above them by a small amount; colder, higher - level clouds will have a bigger effect on the net upward LW flux above them (per fraction of areal coverage), though they will have a smaller effect on the net upward LW flux below them.

Warming must occur below the tropopause to increase the net LW flux out of the tropopause to balance the tropopause - level forcing; there is some feedback at that point as the stratosphere is «forced» by the fraction of that increase which it absorbs, and a fraction of that is transfered back to the tropopause level — for an optically thick stratosphere that could be significant, but I think it may be minor for the Earth as it is (while CO2 optical thickness of the stratosphere alone is large near the center of the band, most of the wavelengths in which the stratosphere is not transparent have a more moderate optical thickness on the order of 1 (mainly from stratospheric water vapor; stratospheric ozone makes a contribution over a narrow wavelength band, reaching somewhat larger optical thickness than stratospheric water vapor)(in the limit of an optically thin stratosphere at most wavelengths where the stratosphere is not transparent, changes in the net flux out of the stratosphere caused by stratospheric warming or cooling will tend to be evenly split between upward at TOA and downward at the tropopause; with greater optically thickness over a larger fraction of optically - significant wavelengths, the distribution of warming or cooling within the stratosphere will affect how such a change is distributed, and it would even be possible for stratospheric adjustment to have opposite effects on the downward flux at the tropopause and the upward flux at TOA).

The effect of band widenning is a reduction in net upward LW flux (this is called the radiative forcing), which is proportional to a change in area under the curve (a graph of flux over the spectrum); the contribution from band widenning is equal to the amount by which the band widens (in units ν) multiplied by - Fνup (CO2).

(the negative sign is there because Fνup (CO2) is positive if CO2 increases the net upward flux, while positive forcing is a decrease in a net upward flux.)

For a small amount of absorption, the emission upward and downward would be about the same, so if the upward (spectral) flux from below the layer were more than 2 * the (average) blackbody value for the layer temperature (s), the OLR at TOA would be reduced more than the net upward flux at the base of the layer, decreasing CO2 TOA forcing more than CO2 forcing at the base, thus increasing the cooling of the base.

«Radiative forcing Radiative forcing is the change in the net, downward minus upward, radiative flux (expressed in W m — 2) at the tropopause or top of atmosphere due to a change in an external driver of climate change, such as, for example, a change in the concentration of carbon dioxide or the output of the Sun.»

There is no bulk transport of molecules because the gas is hydrodynamically stable by construction so no parcel of air experiences a net upward or downward force, begins at rest, and according to Our Friend Newton, remains at rest.

Radiative forcing - Radiative forcing is the change in the net, downward minus upward, irradiance (expressed in W m - 2) at the tropopause due to a change in an external driver of climate change, such as, for example, a change in the concentration of carbon dioxide or the output of the Sun.