Another look at atmospheric dynamics on Titan and some of its general consequences

Abstract

Mean wind velocities, U, and horizontal temperature differences, δT, are estimated for the Titan atmosphere using the similarity theory of the author. It is found that U is of order 1 m/sec and δT ∼ 0.1 K. The last value agrees with its estimate by Leovy and Pollack (1973, Icarus 19, 195–201); however the values of U are an order of magnitude less. While analyzing the causes of the difference it is found that the circulation models developed in I overestimate considerably the atmospheric efficiency in transformation of solar energy into the kinetic energy of motions. Possible reasons for such an overestimate are discussed. We conclude that the efficiency coefficient is a very sensitive characteristic of a circulation regime and that its determination is an efficient means for checking the correspondence of various circulation models with reality. Arguments are presented stressing the conclusion of I that the Titan atmospheric circulation is in the Hadley symmetric regime, which is strongly influenced by the satellite's own rotation. At the same time a thermal tide should be a noticeable feature of the circulation. In the upper part of the Titan atmosphere something like the phenomenon of the 4-day Venus circulation may be developed. It is noted that the analogy between the Titan and Venus atmospheric circulations might be a very close one.