. Compendium of meteorology. Meteorology. 44 RADIATION part in the use of the improved radiation diagram, but jprincipally in the realization that the water-vapor con- tent of the stratosphere is much lower than was formerly assumed. For this reasonâas mentioned aboveâthe main emission level is shifted down to the altitude of the tropopause. The importance of reliable measurements of the water-vapor content of the stratosphere for these investigations cannot be over-emphasized, for a higher water-vapor content sharply reduces the emission at the Jievel of the tropopause. So far only two or thr
. Compendium of meteorology. Meteorology. 44 RADIATION part in the use of the improved radiation diagram, but jprincipally in the realization that the water-vapor con- tent of the stratosphere is much lower than was formerly assumed. For this reasonâas mentioned aboveâthe main emission level is shifted down to the altitude of the tropopause. The importance of reliable measurements of the water-vapor content of the stratosphere for these investigations cannot be over-emphasized, for a higher water-vapor content sharply reduces the emission at the Jievel of the tropopause. So far only two or three meas- urements of the frost point have been published. They show an unchanged decrease above the tropopause [131 sometimes interrupted by thin saturated layers [5]; however, we do not know whether, for example, the "Avater-vapor content over low-pressure areas is higher than shown by these measurements. There is consider- able evidence for this supposition, for otherwise how should the mother-of-pearl clouds observed in Norway â¢develop in the rear portion of cyclones at an altitude of â .28 km, if the relative humidity remains at 1 per cent .and less from an altitude of 14 km upward? If the ihumidity is greater, the radiation processes of the itropopause are reduced considerably. It is also very difficult to make any reasonable state- ments concerning the distribution with altitude of the upper cloud boundaries. It is here assumed that this boundary lies between 0 and 2 km in 15 per cent of all cases, between 2 and 5 km in 45 per cent, between 5 and 8 Ion in 30 per cent, and between 8 and 10 km in 10 per â¢cent of all cases. For the lower cloud boundaries, 80 per â¢cent are assumed to lie between 0 and 3 km, and 20 per "cent between 3 and 10 km. Consideration of these values gives a cooling of the free atmosphere on com- pletely overcast days as shown in Fig. 5, curve B, that is, there is a "radiation screen" in the lowest layers, but above 2 km
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