Possible air mass modification and vertical motion accompanying passage of dry continental air oyer a cold aiid a warm ocean and cool maritime air over a wann oceaii are discussed in the light of available satellite cloud photographs and meteorological data relating to Indian (kezti. Development of cellular clouds is discussed in detail and it is suggested that it occurs mostly in areas where air-sea interaction leads to conditionally unstable thermal stratification and favourable boundary layer convergence through ' thermal wind' effect of ocean surface temperature distribution