The Break Down of Zonal Circulation during the Period January 8 to 13, 1956, the Characteristics of Temperature Field and Tropopause and its Relation to the Atmospheric Field of Motion¹

1 This article summarizes part of the results of investigations on the General Circulation, especially with reference to the upper layers of the atmosphere.

(Air Research and Development Command, USAF, Contract AF 61 (514)-963, through the European Office, ARDC).

Abstract

I. An introductory outline of earlier work (Fr. Defant and H. Taba, 1957, 1958, 1958) on hemispheric changes in the type of General Circulation by means of tropopause maps is presented to make the reader familiar with the main features of tropopause and its intimate relation to the main windcores of the westerlies. The prehistory of the period from Jan. 8 to 13, 1956, which we studied in this paper, is described in detail.

II. Tropopause maps for each day (Jan. 8 to 13, 1956) are presented. By means of these maps it was shown, how the zonal type of Circulation (zonal with respect to a zonal polarfront jet) changes during this period into a meridional (meandering) type. The behaviour of subtropical jet (in a characteristic way different from that of polarfront jet) is simultaneously discussed.

III. A selection of soundings with respect to the breaklines in the tropopause level or according to the location of the belts of maximum wind of the westerlies was made for each day. Different characteristic groups of soundings (different with respect to the total vertical temperature distribution and the form as well as the height of tropopause) are discussed and characteristic mean soundings for each group are computed.

IV. A computation of standard deviation of the individual vertical temperature distributions from the mean one for each group is presented. An important conservatism of the sounding type in each group is shown.

Meridional temperature differences between different groups inform the reader about the possible locations of baroclinity in tropo- and stratosphere.

V. A statistical investigation of tropopause level by use of 2,513 atmospheric soundings from Jan. 1 to 13, 1956 is presented. The structure of tropopause is discussed.

VI. A synoptic vertical cross section clarifies the relationship between subtropical break in the tropopause level and the existence of the subtropical jet. Important aspects of form of subtropical jet are outlined.

Notes

1 This article summarizes part of the results of investigations on the General Circulation, especially with reference to the upper layers of the atmosphere.

(Air Research and Development Command, USAF, Contract AF 61 (514)-963, through the European Office, ARDC).