In summer, a mild wind is often found on the shore of a clam river. This is caused due to
difference in thermal conductivity of water and soil.
conduction between air and the soil.
radiation from the soil.
Convection current is the movement of air (or any fluid) due to the difference in the temperatures. During summer days, there is temperature difference of air above the land and river. Due to this, a convection current is set from the river to the land during daytime. On the other hand, during night, a convection current is set from the land to the river. Therefore, a mild air always flows on the shore of a calm river due to the convection current.