Climates, Standard
NOTE: This sub-paragraph defines three standard climates – Temperate, Tropical and Arctic – by stating the envelope conditions applicable to each. The conditions thus represented are acceptable as giving suitable design criteria for aeroplanes intended for operation in such regions. They are drawn up on the basis of conditions unlikely to be exceeded more often than on one day per year except that they do not cover the extremes of temperature occasionally reached in tropical deserts or in Siberia in winter.
The Temperate, Tropical and Arctic climates are defined by:–
a.
The temperature envelopes enclosed by the appropriate maximum and minimum temperature lines of Fig. 1, from zero metres (feet) to the selected height (e.g. the temperatures appropriate to 0 – 10 000 m (0 – 30 000 ft)) in the standard Temperate climate are those within the envelope A, B, C, D, in Fig. 1;
d.
Every point included in these envelopes being associated with the density corresponding to the temperature, pressure and humidity; extreme values are given in Table 1.
Change 5 1–4 15 July 1996 These conditions do not cover variation of pressure from the International standard. This shall be allowed for by assuming a variation of pressure 5% above and below the International standard pressure (ICAO) associated with the International standard temperature (ICAO). (see IEM 1.1, Climates, Standard.)
b. Every point included in these envelopes being associated with a relative humidity range of 20% to 100%; except that in the conditions represented by the area E, F, G in Fig. 1 the relative humidities shall be assumed to vary from 100% maximum and 20% minimum respectively at the line EF to the value appropriate to the height at the line GF. The value of relative humidity on the line GF shall be taken to vary linearly from 100% maximum and 20% minimum at F to some lower values at G (given here as 10% maximum and 2% minimum);
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