Page 306 - E:\CloudStation\Project\1 DONE\Ranhill CIMAH\Flip Book\

Control of Industrial Major Accident Hazards (CIMAH) Report Page 27
Ranhill SAJ Sdn. Bhd. Revision 01
Part D: Information on the Potential Major Accident Date Aug 2019

Source: Meteorological Department Malaysia & Iowa Environmental Mesonet
st
st
Figure D.4.2: Wind Rose Summary (1 July 2014 to 31 August 2019)

D.4.3 Stability Class

One of the factors that affect the dispersion of gas cloud is the stability of the
atmosphere.

Atmospheric stability determines the extent of mixing as the cloud travels downwind.
Stability is classified into six (6) Pasquill stability classes. The Pasquill stability
classes is a method of categorizing the stability of a region of the atmosphere in
terms of the horizontal surface wind, the amount of solar radiation, and the fractional
cloud cover.