Development of haze on land can often be related to the diurnal cycle of air and surface temperatures. With a significant increase in surface temperature during the day, convection and turbulence increase and dust particles are raised from the surface.
Thus the visibility decreases progressively through the day as an increasing number of particles remain suspended in the atmosphere. The condition is more marked when the E.L.R. limits the ascent of air to the lower part of the troposphere, thus causing a rapid increase in the concentration of dust particles. During the night the particles settle onto the surface, and visibility is improved in the early part of the day.
At sea, haze often the result of movement of dust and sand particles from land. A particular example occurs, usually between November and May, off the north-west coast of Africa, where large quantities of dust from the Sahara are blown off-shore by the local wind, the Harmattan. A similar condition occurs in the Gulf during the summer with the Shamal, a north-westerly wind which collects dust from the desert. Salt particles, which are potential condensation nuclei, may also produce haze at sea when the RH value of the atmosphere is too low for water droplets to develop.
