GEOG 111 1st Edition Lecture 16 Outline of Last Lecture I Air Pressure II Wind a Wind systems Outline of Current Lecture I Wind a Wind systems b Factors affecting wind Current Lecture I Wind generated by pressure differences a Common wind systems i Monsoon seasonal reversal of winds 1 Ex In India Occurs due to thermal differences between land and water 2 Winds blow in opposite direction at the changing of the seasons 3 Land warms much quicker than water so we have higher pressures over water and lower pressure over land in the summer a Air wants to move from higher to lower pressure 4 Summer hot land low pressure onshore flow of air starting at the end of May moisture lift rain a Warmest month is May because a lot of energy is going into the sensible heat flux very dry b Convergence is necessary for cloud and rain development 5 Winter cooler land higher pressure offshore flow of air dry air from inland areas ii Sea land breeze 1 Pressure gradient force 2 Occurs on a daily basis 3 Land warms much quickly than ocean winds move inland clouds form over the beach 4 Strongest in summertime when there s more daytime heating 5 Creates a thermal circulation pattern because at night the land cools faster than the water so a cloud will form over the water instead iii Valley mountain breeze 1 Upslope flow mountains facing the sun heat more intensely than shaded valley areas This develops thermal low during the day which produces a valley breeze These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 2 Mountain breeze cold air drainage opposite phenomenon radiational cooling at night radiational fog cold air drainage into the valley frost can occur at the bottom of the valley called a frost hollow b Factors affecting wind i Pressure gradient wind blows from high to low pressure 1 Shallow pressure gradient low wind speed 2 Steep pressure gradient high wind speed ii Global circulation 1 Low pressure system at equator winds are moving into the low pressure system causing converging a Large scale convection cell is occurring in upper troposphere iii Coriolis Effect moving objects are slightly deflected 1 In Northern hemisphere particles will move West to East 2 Causes the most deflecting at the poles none at the equator increases with increasing latitude 3 Increases with the speed of the air parcel 4 Takes place regardless of the direction of motion 5 Only changes direction doesn t affect speed iv Geostrophic wind only occur in upper atmosphere where there s no friction 1 Occurs when pressure gradient force Coriolis force 2 Wind begins to move parallel with the isobars 3 Winds are particularly strong where isobars are close together where isoheight gradient is strongest v Friction in lower atmosphere surface not in upper 1 By slowing the wind down friction causes a decrease in the coriolis force thus air moves slightly towards low pressure 2 The greater the friction the greater the cross isobar flow 3 Different ways of measuring a Gust factor a rapid increase in wind speed i As friction increases wind speed decreases gust factor increases ii Ex In forest will be high iii Ex At airport will be low b Wind fetch how far wind can travel over a distance i As fetch increases wind speed increases gust factor decreases ii Ex In forest will be low iii Ex At airport will be high 4 Topographic constrictions provides a Bernoulli effect a Wind and water gaps in mountain ridges forces air flow in gaps high wind speeds b Between tall buildings forces air flow between streets vi Cyclonic flow counterclockwise circulation around cyclone low pressure system converging and rising clouds and precipitation 1 This lift drives a lot of severe weather vii Anticyclonic flow clockwise diverging sinking motions air from upper atmosphere moves to surface winds move away from high pressure system clear skies
View Full Document
Unlocking...