Sirocco

Development

Siroccos arise from warm, dry, tropical air masses that are pulled northward by low-pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter-clockwise circulation of the low propels the mixed air across the southern coasts of Europe.

Effects

The sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and warm wet weather in Southern Europe. The sirocco does not affect other parts of Europe. The sirocco's duration may be as short as half a day or may last several days. While passing over the Mediterranean Sea, the sirocco picks up moisture; this results in rainfall in the southern part of Italy, known locally as "blood rain" due to the red sand mixed with the falling rain.

Sirocco is commonly perceived as causing unease and an irritable mood in people. In addition, many people attribute health problems to the wind, either because of the heat and dust brought from African coastal regions, or because of the cool dampness further north in Europe. The dust in the sirocco winds can cause abrasion in mechanical devices and penetrate buildings.

Sirocco winds with speeds of up to 100 km/h (62 mph; 54 kn) are most common during autumn and spring. They reach a peak in March and in November.

When combined with a rising tide, the sirocco can cause the acqua alta phenomenon in the Venetian Lagoon.

This wind also has an impact on fishing. For example, the anchovies caught in the Gulf of Trieste, near Barcola, which are in great demand as a delicacy, are caught only in a sirocco. In cold winds, like the bora, the fish disappear into the Adriatic.