GEO 211 1st Edition Lecture 20 Outline of Last Lecture I Measuring precipitation A Standard rain gauge commonly used Cross section 10 times that of tube Measurable amount 0 01 inch OR greater Less than 0 01 is reported as a trace B Tipping bucket rain gauge consists of 2 buckets Each time a bucket fills up with 0 01 inch of rain it tips sending an electric signal to the remote recorder C Weighing gauge collects rainfall in a cylinder that sits on a sensitive weighing platform When cylinder fills up electrical impulse is transmitted to a pen that records the data II Measuring snowfall A 2 measurements of rainfall 1 Depth with calibrated stick 2 Water equivalent general ratio is 10 1 o Ex 10 inches deep 1 inch of rainfall III Cloud seeding Silver iodide and dry ice are injected in a cloud to act as condensation nuclei Works better in cold clouds with super cooled water Silver iodide commonly used Outline of Current Lecture IV Air pressure force exerted by the weight of air above a given point A Pressure measurements a Units used on weather maps B Standard atmospheric pressure at sea level 1013 25 mb 1013 25 hPa 29 92 in Hg 760 mm Hg 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 High pressure Low pressure Wind C Measuring pressure A Barometers 1 Mercury barometers 2 Aneroid barometers Altimeter Barograph B Air pressure and altitude decreased rapidly with altitude first but decreases slowly with altitude alof Current Lecture IV Air pressure force exerted by the weight of air above a given point Decreases with height A Pressure measurements a Units used on weather maps Millibar mb 1 bar 1000mb Hectopascal hPa 1 hPa 1mb Inches of mercury in Hg Millimeters of mercury mm Hg B Standard atmospheric pressure at sea level 1013 25 mb 1013 25 hPa 29 92 in Hg 760 mm Hg High pressure long column of air exerts more pressure Low pressure short column of air exerts less pressure Wind air moves from high pressure to low pressure C Measuring pressure A Barometers 1 Mercury barometers invented in 1643 by Torricelli Evangelista Figure 8 6 2 Aneroid barometers non liquid Altimeter calibrated to indicate attitude Figure 8 7 Barograph recording barometer Figure 8 8 B Air pressure and altitude decreased rapidly with altitude first but decreases slowly with altitude alof At about 18 400 f 5 km pressure is almost half 500 mb of its sea level
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