As the sun warms the surface, the warmed ground warms the air, raising the air temperature above the temperature at which water vapor condenses into a cloud (or fog). The sun can penetrate the early morning fog enough to warm the surface and create the appearance that the fog is lifting. Places that warm slower will have the appearance of having fog longer. Cars and other things can also warm the area, causing roads to have little fog while the fields off to the side having fog.
Brad’s explanation is good. Places that are at higher elevation generally have slightly colder temperatures, so that is why you sometimes see fog covering hills while the valleys are clear.
Brad and Chris already explained why fog form and why it lifts differently in some situations. Sometimes it depends on the geography – is there a source of moisture (e.g. sea, river, lake) that is being brought to the area and does the air flow a certain way because of where the hills and valleys are?
When the lower part of the fog is being ‘burned’ off (warmed up), the moisture would move up (hot air rises) to the cooler region and condense there again (forming fog but higher up).
If there was recent rain, the moisture in the soil could come up into the air, which can make the fog lift later than if the ground is dry. Some locations is more prone to having more moisture available to form fog.
As the sun warms the surface, the warmed ground warms the air, raising the air temperature above the temperature at which water vapor condenses into a cloud (or fog). The sun can penetrate the early morning fog enough to warm the surface and create the appearance that the fog is lifting. Places that warm slower will have the appearance of having fog longer. Cars and other things can also warm the area, causing roads to have little fog while the fields off to the side having fog.
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Brad’s explanation is good. Places that are at higher elevation generally have slightly colder temperatures, so that is why you sometimes see fog covering hills while the valleys are clear.
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Brad and Chris already explained why fog form and why it lifts differently in some situations. Sometimes it depends on the geography – is there a source of moisture (e.g. sea, river, lake) that is being brought to the area and does the air flow a certain way because of where the hills and valleys are?
When the lower part of the fog is being ‘burned’ off (warmed up), the moisture would move up (hot air rises) to the cooler region and condense there again (forming fog but higher up).
If there was recent rain, the moisture in the soil could come up into the air, which can make the fog lift later than if the ground is dry. Some locations is more prone to having more moisture available to form fog.
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