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Posts tagged Fog

Snowfall Over the Alps and Fog Across Northern Italy

45.4N 9.1E

February 17th, 2013 Category: Mountains

Italy – January 26th, 2013

The Alps, one of the great mountain range systems of Europe, are covered in snow in this winter image. The mountains stretch approximately 1,200 kilometres (750 mi) across eight countries from Austria and Slovenia in the east, Switzerland, Liechtenstein, Germany, France to the west and Italy and Monaco to the south. Here, a fog can be seen extending over northern Italy, from the Alps, across the valley of the River Po, to the northern slopes of the Apennines.

Thick Clouds Over Po Valley, Between Alps and Apennines, Italy – February 1st, 2011

44.9N 10.7E

February 1st, 2011 Category: Clouds, Image of the day, Lakes, Mountains

Italy - January 16th, 2011

While the white snow on the Alps serves to highlight their ridges and differentiate them from the valleys below, the Italian terrain to the south is completely obscured by thick, white clouds.

This cloud cover rests between the Alps and the Apennines, sits over the Po Valley, and spreads out over Venice and the Adriatic. Lake Garda, however, is visible at the base of the Alps and just at the beginning of the thick fog layer.

Clouds and Fog Along the California Coast – June 1st, 2009

37.7N 122.4W

June 1st, 2009 Category: Clouds

West Coast, USA - May 25th, 2009

West Coast, USA - May 25th, 2009

San Francisco Bay

San Francisco Bay

Here, the coast of California is framed by a blanket of clouds and sea fog. Fog begins to form when water vapor (a colorless gas) condenses into tiny liquid water droplets in the air. Fog normally occurs at a relative humidity near 100%.

Another common type of formation is associated with sea fog (also known as haar or fret), due to the peculiar effect of salt. Clouds of all types require minute hygroscopic particles upon which water vapor can condense. Over the ocean surface, the most common particles are salt from salt spray produced by breaking waves.

Except in areas of storminess, the most common areas of breaking waves are located near coastlines, hence the greatest densities of airborne salt particles are there.

Condensation on salt particles has been observed to occur at humidities as low as 70%, thus fog can occur even in relatively dry air in suitable locations such as the California coast, as shown here. Typically, such lower humidity fog is preceded by a transparent mistiness along the coastline as condensation competes with evaporation, a phenomenon that is typically noticeable by beachgoers in the afternoon.

The close-up focuses on San Francisco, where the combination of cold ocean water and the high heat of the California mainland create the city’s characteristic fog that can cover its western half all day during the spring and early summer. The fog is less pronounced in eastern neighborhoods, in the late summer, and during the fall, which are the warmest months of the year.

The high hills in the geographic center of the city protect neighborhoods directly to their east from the foggy and cool conditions experienced in the Sunset District; for those who live on the eastern side of the city, San Francisco is sunnier, with an average of 260 clear days, and only 105 cloudy days per year.

Fog Below Italian Alps

March 2nd, 2009 Category: Rivers, Snapshots

Northern Italy - February 26th, 2009

Northern Italy - February 26th, 2009

The Italian Alps, curving from the top right to the bottom left, are covered by snow, as is the smaller Apennine Range, running southward from the bottom right quadrant.

The lowlands towards the center, between the two mountain ranges, where cities such as  Turin and Milan are located, are free of snow but coated with a light fog.

The River Po can be seen flowing through the center of these lowlands, and Lake Garda is visible to the right, just below the Alps.

Fog in Northern Italy – October 18th, 2008

October 18th, 2008 Category: Image of the day

Italy - October 9th, 2008Italy

Italy - October 9th, 2008

Close up of a meteorological disturbance by Sardegna

Close up of a meteorological disturbance by Sardegna

Close-up of fog in northern Italy

Close-up of fog in northern Italy

Here, we have a clear view of Italy at the beginning of the second week in October. In the north, we can see fog covering the Padana Plains (Pianura Padana) from West to East, around the River Po and near cities including Turin, Milan and Ferrara. Further south, we can also observe a meteorological disturbance off the northeastern coast of Sardinia in the Tyrrhenian Sea, obscuring Olbia and other cities.