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Lecture 3. Vertical Structure of the Atmosphere. Average Vertical Temperature profile. Atmospheric Layers. Troposphere On average, temperature decreases with height Stratosphere On average, temperature increases with height Mesosphere Thermosphere. Lapse Rate.
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Lecture 3 Vertical Structure of the Atmosphere
Atmospheric Layers • Troposphere • On average, temperature decreases with height • Stratosphere • On average, temperature increases with height • Mesosphere • Thermosphere
Lapse Rate • Lapse rate is rate that temperature decreases with height
Soundings • Actual vertical temperature profiles are called soundings • A sounding is obtained using an instrument package called a radiosonde • Radiosondes are carried aloft using balloons filled with hydrogen or helium
http://www.srh.noaa.gov/mob/balloon.shtml Radiosonde
Application: Reduction to Sea Level(See Ahrens, Ch. 6) proportional to weight of this column of air Surface pressure also called station pressure (if there is a weather station there!) Surface pressure here
Math Obtained by integrating the hydrostatic equation from the surface to top of atmosphere.
Deficiencies of Surface Pressure • Spatial variations in surface pressure mainly due to topography, not meteorology
Height contours on topographic map Units: m It’s a mountain! 1050 1000 950 900
Surface pressure (approximately) Units: hPa 885 890 895 900 Isobar pattern looks just like height-contour pattern!
“Reduction to Sea Level” is proportional to weight of this column of air Let T = sfc. temp. (12-hour avg.) Surface pressure here For sea level pressure add weight of isothermal column of air temp = T. Sea Level
Pressure as Vertical Coordinate • Pressure is a 1-1 function of height • i.e., a given pressure occurs at a unique height • Thus, the pressure can be used to specify the vertical position of a point
Pressure Surfaces • Let the pressure, p1, be given. • At a given instant, consider all points (x, y, z) where p = p1 • This set of points defines a surface
z p = p1 z(x2) z(x1) x x1 x2
Height Contours Heights indicated in dekameters (dam) 1dam = 10m
Two Pressure Surfaces z p = p2 z2 z2 – z1 z1 p = p1
Thickness • z2 – z1 is called the thickness of the layer • Hypsometric equation thickness proportional to mean temperature of layer
Thickness Gradients z p = p2 Large thickness Small thickness warm Cold p = p1
Exercise • Suppose that the mean temperature between 1000 hPa and 500 hPa is -10C. • Calculate the thickness (in dam)