190 PHYSICS OF THE AIR
this is exactly what must occur in the stratosphere, if locally lifted <>r lowered bodily,1 hence, we infer that such lifting and lowering does occur over anticyclones and cyclones, respectively.
Let a stratospheric column be dropped bodily a distance <///, and let the surrounding air come in until equilibrium is again established. At each level there, obviously, will result a change in pressure directly proportional to the pressure at that level. That is, throughout the column
d? - K, a constant. P But, as is well known,
dT _ rdp
-yr - <,y
in which T is the absolute temperature, and C a constant, 0.2H43 for dry air. Hence, since T is constant, roughly, in the stratosphere, dT also is constant, and the upper air remains vert irally isot he • rmal, what over the pressure increase or decrease. An increase ol pressure in the stratosphere, such as presumably takes place* over cycluws, ///rw/.sr.s* its temperature, while a decrease of pressure, such as pmhably occurs over anticyclones, correspondingly decrease^ its temperature. In each ease the pressure effect presumably is slightly enhanced l»y tin* coincident, change in the intensity of radiation from below.
Suppose the temperature of the stratosphere over .a cyclone should differ from that at the same place over the following anticyclone hy 10° C., what, according to the above* conception, will lie t he approximate change of boundary level? Let // be this change, and l«'t the temperature of the stratosphere be 220° Abs. Then since
dp ^ (jh p ~ // '
in which H is the height of the homogeneous ;jf sim: pfu Te, ahout <)-!">() meters at the assumed t(ktnperature, it follow;- that
22() = 0.2S-i;>^' roughly, and
//, = 1 kilometer a|)pro\iniatrl\ ,
That is, the temperature of the stratosphere will im-n^ise or decrea.s<k at the rate of approximately 10° (\ per kilometer '-nf^rred f.-ill or rise, respectively, under the influence of cyclonic and anticyelonio disturbances.
In this connection, it should be noted that, nn the average, and at-least over the British Isles and continental Kumpe. th«- clinnges of pressure at the height of even 9 kilometers is substantially the same as at,
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