B5-28 PREPARATION OF CHARTS 
(3) The flight must extend to a pressure of 200 mb or less. 
(4) The average lapse rate does not exceed 3°C/km over at 
least 1kminany higher layer upto and including 100 mbs. 
14.2 Procedure for Selecting Tropopause Level. To facilitate the selec- 
tion of the tropopause level, a Tropopause Template WBAN-31B1 is pro- 
vided. This template may be used only with WBAN-31B. The sloping 
curves on the template approximate lapse rates of 2°C/km. The barbs 
on the curves are approximately the boundaries of 2-km layers. 
14.3 Tropopause Template WBAN-31B1. To use the Tropopause Tem- 
plate WBAN-31B1, superimpose it on WBAN-31B so that 500-mb isobar 
on the template coincides with the 500-mbisobar on the adiabatic chart, 
and so that the vertical border lines on the template are parallel to the 
isotherms on the adiabatic chart. Move the template to the right or left 
until the sloping curve, whose temperature is nearest that of the level 
tested, intersects the temperature curve at the level. If the lapse rate 
in the stratum immediately above the level testedis 2°C/km or less, and 
the temperature throughout the two-km layer above the level are every- 
where as high as , (orhigher than) a 2°C/km lapse rate, all temperatures 
will fall on or to the right of the sloping curve and the level tested may 
be regarded as the tropopause. This will be true regardless of the con- 
figuration of the temperature curve within the two-km stratum as long as 
no point within the stratum falls to the left of the sloping curve. If the 
level in question fails to qualify as the tropopause and another level must 
be tested, repeat the process until the tropopause is located, or until it 
is definitely established and no point within the range of the template 
meets the criteria for a tropopause. 
Since the curve on the template is based on the Standard Atmosphere, 
the actual lapse rate should be computed when the temperature trace and 
the sloping curve on the template almost coincide, to ascertain that the 
criteria in §B5-14.1(a)(2) are met. 
Whenever no tropopause is selected within the range of the Tropopause 
Template WBAN-31B1, the actual lapse rates must be computed. If the 
tropopause is selected at pressure greater than 500 mbs, the lapse rates 
above the tropopause must be tested for compliance withJB5-14.1(b)(4). 
14.4 Transmitted Data. Tropopause data will be included in the appro- 
priate ''Coded Message for Transmission"' block on WBAN-31A or B and 
will be transmitted in accordance with instructioninthe Federal Meteor- 
ological Handbook No. 4 (Radiosonde Code). Wind data will be taken from 
the winds-aloft graph at the corresponding pressure. 
= Soe) F MH#3 
