Mount Cimone (2379m a.s.l.) Is in the Mildness, while a Thin Layer of Hoar Frost Has Formed in the Lower Raccolana Creek Valley (475m a.s.l.): this Is the Late Autumn Anticyclonic Thermal Inversion; Western Julian Alps, Saletto, Udine, FVG, Italia
15-November-2024
The Raccolana valley descends rapidly and narrowly from Sella Nevea resort (that's on the mountain saddle between the Canin and Montasio main ranges, dividing the wide Rio del Lago valley from this narrower and lower valley) towards the western Julian Alps.
The thermal inversion of the valleys and basins is caused by the persistence of a dynamic high pressure with warm air at high altitude, which favors the accumulation and stagnation of progressively colder and more humid air in their lower layers.
The center of a dynamic HP increases the gravitational attraction favoring an adiabatic push downwards where the cold air, which is denser and heavier than the warm air, stagnates in areas without local and orographic winds and/or strong night breezes.
Partly this cold air arrived earlier, but a greater part was formed on site due to the long nights with loss of heat from the ground towards space (HP clear sky) and the perennial shadow during the day.
The warm air of sub-tropical origin that "inflates" the dynamic anticyclone slides above and so there is an inverse gradient in the lower layers of the air column with frost on the ground of the flat areas and mildness on the sloping areas and mountains peaks.
Frost, of whatever type, is not dew that freezes (which would form glassy or black ice and not white crystals, which form only in saturated air, in clouds and fogs), although the meteorological conditions of formation are very similar, but, with temperatures below freezing point and saturated air there is direct sublimation of the vapor into crystals, only on meadows (rime) if the inversion is limited to a few dozen centimeters from the ground, even on vertical structures up to tens of meters high (hoar frost) if the inversion is thicker with the presence of freezing fogs, especially at night.
Mount Cimone (2379m a.s.l.) Is in the Mildness, while a Thin Layer of Hoar Frost Has Formed in the Lower Raccolana Creek Valley (475m a.s.l.): this Is the Late Autumn Anticyclonic Thermal Inversion; Western Julian Alps, Saletto, Udine, FVG, Italia
15-November-2024
The Raccolana valley descends rapidly and narrowly from Sella Nevea resort (that's on the mountain saddle between the Canin and Montasio main ranges, dividing the wide Rio del Lago valley from this narrower and lower valley) towards the western Julian Alps.
The thermal inversion of the valleys and basins is caused by the persistence of a dynamic high pressure with warm air at high altitude, which favors the accumulation and stagnation of progressively colder and more humid air in their lower layers.
The center of a dynamic HP increases the gravitational attraction favoring an adiabatic push downwards where the cold air, which is denser and heavier than the warm air, stagnates in areas without local and orographic winds and/or strong night breezes.
Partly this cold air arrived earlier, but a greater part was formed on site due to the long nights with loss of heat from the ground towards space (HP clear sky) and the perennial shadow during the day.
The warm air of sub-tropical origin that "inflates" the dynamic anticyclone slides above and so there is an inverse gradient in the lower layers of the air column with frost on the ground of the flat areas and mildness on the sloping areas and mountains peaks.
Frost, of whatever type, is not dew that freezes (which would form glassy or black ice and not white crystals, which form only in saturated air, in clouds and fogs), although the meteorological conditions of formation are very similar, but, with temperatures below freezing point and saturated air there is direct sublimation of the vapor into crystals, only on meadows (rime) if the inversion is limited to a few dozen centimeters from the ground, even on vertical structures up to tens of meters high (hoar frost) if the inversion is thicker with the presence of freezing fogs, especially at night.