ANALYTICAL EXPRESSION OF NOCTILUCENT CLOUDS AND POLAR MESOSPHERIC CLOUDS OCCURRENCE PROBABILITY FROM DATA OF THE MESOSPHERIC TEMPERATURE-MEASUREMENTS

Noctilucent and Mesospheric clouds form close to the mesopause on a he ight about 82 km, if temperature and humidiby are favourable. However, they do not become visible until obliquely illuminated by sun from be low the horizon, and, even then, only when the solar zenith angle lies within the limits of 96 and 106 degrees. The link between occurance o f Polar Mesospheric clouds and Noctilucent clouds with the pecularity of mesospheric tempereture profile points at the possibility of temper ature measurements for the prognosis of Polar Mesospheric and Noctiluc ent clouds occurances. Data of temperature measurements at height 82 k m have been analysed and analytical expressions for seasonal variation s of temperature have been obtained. Comparison of seasonal variations of temperature has shown accordance within 20%, thus this provides th e possibility of Polar Mesospheric clouds and Noctilucent clouds occur ances from the data of temperature measurements.