From Glossary of Meteorology
A local name given in Spain to the summer haze described by Kendrew (1937).
He says, "In summer there is very active evaporation and almost complete drought, broken only by an occasional thunderstorm, and the fierce heat burns up the vegetation. Without irrigation the landscape is semi-desert, brown and grey are dominant colors, and dust is everywhere— the parched ground is thickly covered, and the air is hazy with minute dust particles which have been swept up by the strong winds. The haze is known as the calina, and is probably due to irregular refraction of the light, as well as the dust. The view is frequently obscured by the dismal grey calina in all the south Mediterranean lands."
Kendrew, W. G. 1937. The Climate of the Continents. 3d ed., Oxford, The Clarendon Press, . 478 pp.