THUNDERSTORMS 
show usually considerable difference from the ascent (times of begin- 
ning of ascent and end of descent are given at bottom). The clouds 
are realistically pictured, and their amounts and character listed at 
the top, also direction and velocity. On July 11 PM air from the 
NW has been moving over the station for almost 2 days. The 4:49 
a.m. sounding made 1 hr and 28 min after sunrise, shows a nocturnal 
radiation inversion, and a few shallow Su clouds under a stable 
layer and haze line at about 1850 meters. At 14:34 h the clouds had 
thickened to .6 Cu with base at 2km, the lapse rate averaged dry 
adiabatic but irregularities in some layers are evident, probably due 
to descending and rising currents, thermals). At 19:15 h (just 20 
min before sunset) the clouds are gone, only the haze line remains, 
and the nocturnal inversion is already beginning, with a slight stabil- 
ity developed at all levels. That was a relatively dry air mass, like 
Npep in central United States. 
The case of Aug. 9 was in CPW (i.e., returning NPC air of a Russian 
High) and there was enough moisture for instability to produce show- 
ers in the afternoon. At 6:32 a.m. (2 hrs 24 min after sunrise) there 
are only haze lines at 2 km and 1 km, at the bases of the slightly more 
stable layers. The descent, however, shows a much steeper lapse rate 
with the inversion wiped out and a positive energy area already in 
evidence. By 10:58 h the sky is full of Cu congestus starting at 1200 
meters and large amounts of positive energy are present from the 
surface up to high levels. The descent was even more unstable. At 
13.57 h Cb have developed with large cirrus anvils observed, the 
cloud base is higher, and the positive energy areas reduced by the con- 
vection working up to higher levels. At 18:29 h, 25 min before sunset, 
the clouds have largely evaporated and the remnants spread out into a 
shallow Fe vesperalis layer. Stability is returning rapidly along 
with a general subsidence (compare descent with ascent) and a strong 
radiation inversion has already begun to form. At higher levels and 
in the distance scattered remnants of Ci and Cb systems are still 
visible. 
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