The Planetary Boundary Layer (PBL) or the boundary layer is the lowest part of the atmosphere ranging up to 2-4 km height and is largely influenced by the ground surface in contact with it. Above the PBL, the atmosphere is relatively free from the ground influences but the boundary layer dynamics has a role to play on it. Therefore the contributions of turbuances generated by heat exchange processes between ground and the atmosphere up to the PBL cannot be neglegted even at the free mixing

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... spheric environment up to the tropopause altitude of 15-16 km. It is important thus to identify the PBL height, the responsible region of earth /atmosphere interacting zone, so that the effct of turbulence at the free mixing status can be identified. In this paper a new approach is taken in identifying PBL height by adopting the irregular structure, the structure constant parameter (Cn 2 ) that involves variabilities like humidity, potential & ambient temperature and presuure. The exercise is done over Guwahati (26.2°N, 91.75°E), an earthquke prone zone so that the observed result may be examined in identifying earthquke realted modification in structure constant parameter within the PBL height. Finally the focuss is made on the importance of such study in formulating predictive features in climate modification through understanding coupling processes within PBL and free mixing zone.