Five types of fog are : steam , warm frontal , radiation , advection and upslope fog . Steam fog develops when into the air evaporates water with temperature higher than that of the air . Since there is now more water in the air the actual vapor pressure (AVP ) increases and water vapor condenses into a fog . This type may be seen on October over the lakes in Glacier National Park . Warm frontal fog forms when precipitation falls from warm air above through cold air below the warm one . When this precipitation is close to the surface , it
evaporates and therefore , the AVP increases and when it reaches the level of saturated vapor pressure (SVP ) the fog is formed . Both steam and frontal fog take place when AVP increases . The next three types of fog are caused by decreased AVP . The radiation fog is a nighttime happening generated by the radiation cooling of the Earth . The advection fog takes place when warm and moist air moves to a cool surface , and the upslope fog is when warm and moist air moves up the slope of a mountain
For each of the four types of precipitation types the lapse rate is different as the altitude changes . In case of snow , the lapse rate is below freezing regardless of the altitude . Rain takes place when the lapse rate started below freezing gets warmer closer to the surface Sleet is the same rain drop which encounters a thick freezing layer closer to the surface . And if the layer closer to the surface is thin rather than thick , we get freezing rain
Cold cloud formation requires the following steps : ice nuclei (have the same structure of ice crystal which may form by deposition , SVP over ice should be above SVP over water . The water vapor around the water droplet moves from the water droplet to the ice crystal , and as it leaves the droplet more of it evaporates from the droplet . Accretion happens when ice crystals combine with water droplets , and if they combine with other ice crystals we have aggregation
The process of a mid-latitude cyclone has six stages . At the initial stage the Polar Jet Stream forms a stationary front . At the Easterly wave stage , the Polar Jet wobbles taking the form of a wave . This wave gets stronger and low pressure forms at its top during the mature stage Here both warm and cold fronts intensify , the wind direction being the same as in previous stage . Next step , the late mature stage , happens when the warm air is lifted from the surface as a result of cold air catching up with warm . When the cold air catches the warm close to the apex , this is the occluded stage . At the last stage , the dissipated , all warm air goes up from the ground and cold air is circling around the upper level low PAGE
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