Pasquill chart

Critical GLC s can usually be calculated based on a unstable atmosphere, thus enabling the designer to determine a worst case scenario. For any given day, typical atmospheric stabihty data can usually be obtained from a local weather bureau, or may be estimated from the so-called Pasquill chart for the appropriate Atmospheric Stability Class (refer to Table 1). 

Table 1. The Pasquill Chart for Determining the Atmospheric Stability Class...

From Pasquill s chart (Table 1), for a bright summer day with windspeeds of 3 m/s, the atmospheric conditions can be described as Class B, unstable. 

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