Fog



  • Infact fog is low cloud which has hight not more than 50 feet and required very weak wind with speed of 9 km/h or less generaly fog will restrict horizentl surface visibility to less than 1000 m . as noted sunlight and strong wind with speed of more than 9 km/h are two major things which will destroy fogs . strong wind will separate or lift it to hight more than 50 feet and than the fog wil be called as low stratus cloud . other wise quickly after sun rise the relative humidity (whis is the actual amount of moisture in the air compared to the total amount of moisture that air can take to become saturate at that temperature) will rise and the fog will dissipate .



  • @RAVAR said
    "........ after sun rise the relative humidity ...... will rise "

    I think you are not right.
    The relative humidity usually FALLS afer sunrise and the fog dissipates.
    The temperature usually RISES after sunrise!



  • Yes that's right . that was my mistake . sorry for that !!!



  • Types of Fog

    Fog is classified according to the way it forms . Radiation fog also known as Ground fog is very common . it forms over fairly level surfaces on clear , calm humid nights . as surface cools by radiation the adjucent air is also cooled to it's dewpoint (which is the temperature at that air reaches a state where it can't hold any more water vapor) . radiation fog usually occurs in stable air associated with high pressure system .

    Advection fog is caused when a low layer of warm , moist air moves over cooler surface . it is most common under cloudy skies along coastlines where air moves from the warm water to the cooler surface of land .

    Upslope fog forms when moist , stable air forced up a sloping land mass . like advection fog , upslope fog occure under cloudy skies .

    Precipitation _ induced fog may form when warm air or drizzle falls through a layer of cooler air near surface . evaporation from the falling precipitation saturates the cool air causing fog to form . this fog can be very dense and usually it does not clear until the rain moves out of the area .

    Steam fog or Sea smoke occurs as cold , dry air moves over comparatively warmer water . it rises upward from the water surface and resembles rising sea smoke . it is composed entirely of water droplets that often freeze quickly and fall back into water as ice particles .

    Note : radiation fog is stronger than advection fog . temperture diffrent between dewpoint and environment temperture for fog formation must be less than 2 degree of C(4 degree of F)


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