The Probing of the Tropopause by Balloons that Follow It - A Suggestion

Over a half century after the discovery of its existence, t8he tropopause is still one of the challenging mysteries to meteorologists. Radiosonde observations indicat'e that the vertical temperat'ure gradient of the air often changes rattler abruptly at the tropopause, although the apparent sharp break of t'he t'emperature gradient m a y be artificial because of the fact' t'lrat' straight line segments between report'ed temperature observations are employed t'o represent the true, and perhaps smoother, temperature tlis-t'ribut'ion. Even if the kink of the temperature curve at the tropopause is removed, the fact remains that t'he temperature gradient changes rapidly within a rather narrow zone immediately above and below t'hc point designated as the tropopause. rlre mystery about the tropo-pause is, t'herefore, not primarily its location, bat rattwr the sharpness of the change of the temperature gradient' that is associated with it. The radiative processes and the other large-scale heat transport processes that cleter-mine the mean atmospheric temperature distribution probably also determine the large-scale features of t h e tropopause, such as its general location and its seasonal and large-scale spatial variations. Rut what is the reason for the often observed sharp change of the t'emperaturr gradient at the tropopause? What are the physical processes that are responsible for it's creation, maintenance, transformat'ion, and destruction? There are as yet no answers to these questions. Few suggestions concerning the creation of a sharp tropopause or its maintenance have been put forward (i.e. hloller [5], Staley [SI, Kaplan [ 3 ]) and they are hypothetical in that they are based on other assumptions. Still more basic and serious than this, it seems to this writer, is the fact that we do not even have an adequate observational study of the tropopause. We have only a gross and simplified picture of the t'ropopause :tnd we do not know how a particular tropopause evolves with t,ime. There are several reasons why ordinary radiosonde observations fail to provide a (detailed picture of thc tropopause. First of all, the ordinary practice of reporting alternatively the humidity and temperat'ure prohibits a continuous description of temperature. Second, as a result of the combined effect of the large ascensional rate of the balloon and the time lag of t.he sensing thermistor, the reported temperature actually-represents an average temperature over a rather large distance in the vertical below the location of the reporled temperat'ure.2 In addition, tlle representation of the temperature transmission …