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by: Ms. Kylee Marvin


Ms. Kylee Marvin
GPA 3.97

David Flory

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David Flory
Class Notes
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This 77 page Class Notes was uploaded by Ms. Kylee Marvin on Saturday September 26, 2015. The Class Notes belongs to MTEOR 311 at Iowa State University taught by David Flory in Fall. Since its upload, it has received 50 views. For similar materials see /class/214428/mteor-311-iowa-state-university in Meteorology at Iowa State University.




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Date Created: 09/26/15
Meteorology 31 1 Atmospheric Stability Fall 2008 Meteorology 31 1 Air Parcel Consider a parcel of infinitesimal dimensions that is Thermally isolated from the environment so that its temperature changes adiabatically as it sinks or rises Always at the same pressure as the environmental air at the same level assumed to he in hydrostatic equilibrium Moving slowly enough that its kinetic energy is a negligible fraction of its total energy Meteorology 31 1 Stability Stability describes how air parcels react to an initial vertical push by some external force Forced to return to its original position stable Continues to accelerate away from its originial position without outside help unstable Continues to move away from its original position without accelerating neutral Meteorology 31 1 Stability cont Consider a small disturbance from equilibrium 7 Note Primed values refer to the PARCEL P P39 Adiabatic displacements on small time scales Meteorology 31 1 Lapse Rates Dry adiabatic lapse rate 7 Rate at which quotdryquot parcel changes temperature if raised or lowered in the atmosphere 7 10 Clcm Moist adiabatic lapse rate 7 Rate at which moist parcel changes temperature if raised or lowered in the atmosphere 7 6 Ckm Environmental lapse rate F 7 Temperature structure of the environment Meteorology 31 1 F lt Parcel Lapse rate Buoyant acceleration lt 0 Buoyant force is opposite the displacement negatively buoyant Positive restoring force Hydrostatically stable or positive stability Meteorology 31 1 F Parcel Lapse Rate Buoyant acceleration 0 No restoring force Displacements are met without opposition Hydrostatically neutral or neutral stability Meteorology 31 1 I gt Parcel Lapse Rate Buoyant acceleration gt 0 Buoyant force in direction of displacement Negative restoring force Hydrostatically unstable or negative stability IVIeteorology 31 1 n Neura r t r o Unslahle r gt x J r 1 d Unsaturated I s Saturated at Figure 73 Vertical stability in terms of temperature and the environth lse r Meteorology 3 1 1 Stability Theta Uns able NewaL Slams l 1 l o Figurt 7A V39umcni stability undc umnmmwd canditinns in tcrms of porcmia tcmpcramr Meteorology 31 1 Moisture FltTmltTd 7 Absolutely stable l39gtl39dgtl39m 7 Absolutely unstable TmltFltTd 7 Conditionally unstable 7 Stable for unsaturated conditions 7 Unstable for saturated conditions Meteorology 311 in mm of Meteorology 31 1 Vertical Motion Stability determines a layers ability to support vertical motion and tranfer heat momentum and constituents How do you get vertical motion 7 Frontal boundaries airmass differences 7 Topography 7 Convergence continuity equation 7 Differential heating Meteorology 31 1 Temperatures Potential tempertature 7 Conserved in an adiabatic process 7 Dry adiabat Wetbulb temperature 7 Conserved in a moist adiabatic process 7 Moist adiabat Equivalent potential temperature 7 Raise parcel until all moisture has condensed out and bring parcel back to 1000mb 7 Used to compare parcels with different mositure contents and temperatur s Meteorology 31 1 Changes in Lapse Rate Environmental Lapse Rate can change over time Nonadiabatic heating and cooling Solid advection Differential advection Vertical motion Meteorology 31 1 Thermodynamic Diagrams Let us plot the vertical structure of the atmosphere Tephigram Stuve Diagram 7 Pseudoadiabatic chart SkewT log P diagram 7 Most used operationally by forecasters Meteorology 31 1 SkewT Diagram YAxis is logarithmic in pressure Isotherms are quotskewedquot 45 from lower left to upper right Dry adiabats slope from upper left to lower right Label in degrees Celcius Saturation or moist adiabats curved 7 green on official charts Mixing ratio lines dashed almost and slope a little from lower left to upper right gkg Meteorology 31 1 Movement If air is dry notsaturated e is conserved 7 Adiabatic move along a dry adiabat or line of constant 9 7 Mixing ratio does not change If air is saturated moisture condenses or evaporates heat released impacts the temperature 7 Se and SW keep the same value 7 Mixing ratio changes Meteorology 31 1 Important Variables Mixing ratio w 7 Use w line through Td Saturated mixing ratio ws 7 Use w line through T RH 100 wws Vapor pressure e 7 Go from Td up isotherm to 622mb and read off mixing ratio in Inb Saturation vapor pressure 7 Use T not Td More Variables Wetbulb temperature TW Wetbulb potential temperature 9W Equivalent temperature Te Equivalent potential temperature Se Meteorology 31 1 Meteorology 31 1 Important Levels LCL lifting condensation level 7 Where lifted air becomes saturated LFC level of free convection 7 Where lifted air becomes positively buoyant EL Equilibrium level 7 Where lifted air becomes negatively buoyant up high CCL Convective condensation level 7 Height to which a parcel of air would rise adiabatically to saturation from surface heating CAPE CAPE Convective Available Potential Energy Positive area between parcel path and environmental profile Gives energy available to be converted to kinetic energy and upward motion standard height above sea level kilometers standard height above sea level kilometers O MWhUIQNICOLD Meteorology 3 1 1 Lifted Index 92 Showalter Index 70 SWEAT Index 5761 K Index 86 Total Total Index 559 CAPE 4425 Jouleskilogram CINH 93 Jouleskilogram Path of 39 risilng ailr parlcel Environmental Environmental Dewpoint Temperature L 80 70 60 50 40 30 20 10 0 10 20 30 40 Temperature C Lifted Index 284 Showalter Index 167 SWEAT Index 622 K Index 99 Total Total Index 256 CAFE O Jouleskilogram CINH 0 Jouleskilogram Environmental Dewpoint A Topeka Kansas L 9 N quot 200 VIII IIIIII W Temperature I 39 lL Path of rising air parcel 39 39 I l Il 80 70 60 50 4D 30 20 10 0 10 20 30 40 Temperature C 2002 KendallHunt Publishing Stability Indicies LI Lifted Index SI Showalter Index K Index TT Total totals Precipitable water Meteorology 31 1 Meteorology 31 1 Example mvg v A mm AWIaM A Meteorology 31 1 Example 2 Meteorology 31 1 Example 3 Meteorology 31 1 Example 4 Divergence Vorticity Vertical Motion Meteorology 311 Fall 2008 Expression of Winds Wind barbs magnitude and direction Meteorological degrees magnitude and direction Vector Components Taylor expansion of wind three terms Divergence vorticity deformation Divergence 6 gt 0 Expansion of a parcel After construction zone 6 lt 0 Compression of a parcel Before construction zone Calculation of divergenceconvergence is difficult on a cartesian grid What do we do Natural Coordinates Rotate axis so XAxis points along the wind Y Axis is 90 to the left s is aligned with wind n is positive to the left uVcoseb vVsineb 6b is angle which you have rotated the coordinate system Divergence Natural Coordinates Terms are usually both large and have opposite sign Hard to tell if there is divergence convergence just because there is con uence diffluence Vortioity Natural Coordinates Spin of a parcel Horizontal spin is most important to meteorologists 2 component Counterclockwise spin positive vorticity Clockwise spin negative vorticity Cyclonic vorticity having the same direction of rotation as the Earth Anticyclonic vorticity Opposite direction Why is this important 0 DivergenceConvergence Low level convergence a Upward motion Clouds and precipitation Continuity equation Low level divergence a Downward motion Fair weather 0 Vorticity PVA a Upward motion Downstream of a vorticity maximum Clouds and precipitation NVA a Downward motion Fair weather Usually looked at high up in the atmosphere Vertical Motion 0 Synoptic scale uandv10mls w 1 cms 0 Weather ballons 10 error in measuring horizontal winds 1 ms Not good enough Effectiver impossible to measure w 0 What do we do What do we do Diagnose w from other relationships If you have w or w in an equation you can solve for it Remember 0 Think about the sign Five techniques for estimating w or w Methods Kinematic Method Continuity equation Most commonly used Adiabatic Method T hennodynamic equation Isentropic Method Isentropic coordinate adiabatic motion Vorticity Method Vorticity equation Satellite Method Determine cloudtop temperature changes with time Meteorology 311 J gQmegian Cyclone Model 9F quot920082 a MidLatitude Cyclones What quot f V7quot 39396w pressurelocated between 30 and 60 latitude r g V 39 guise gffmqst39 6fthe stormy weatherin US 397 kespeciallyrdUrin39g the winter season ggegipting significant weather phenomena a 39ZZ r d sx ooding rains and severe we ti i g i Stages of Development Init ia39l Setup T g quotI j tiation M V A g gt gvel op mfeht M 4 Mature or Occ ll39J39ded M Initial Setup Knitiaz ion Initiation cont Development Temperature Advections Warm air advectiQn upward motion E39 f 0wers surface pressure Temperature advections cont Development Mature or Occuded Surface d Mature cont Surface Mature cont Aloft Mature cont r DISSpaz lon D I U 0 Textbook DAV L m 342800 ommm IQ C Textbook case Maroh superstorm of 1993 More than a foot of snow from Alabama to ma adds ripped through Florida m h39uri39 igri39 7 I 9 fl H urricane force winds and barometric pressure followed by record cold over y d States Storm of Century 3303121s Storm of the Century 83031318 vi 39 39 hmus 79f Tehuantepec Storm of the Century 1 3303141 Other models I Shapirorkeysar Mode 5 Narwegian Modal 1v TIT I j E 5 6V Meteorology 311 a 1 What is it Types of Sensing Weather slazmns Radarcuverage H V 39 Ovarmppinu39 quot Satellite Satelite Observations Geostationary Remains stationary over a specific point onme earth G ES Geostati O hary Operational Environmental Satellite 39 quot f 39 G e a39re giOh of interest defined by the owner 39 H tien 20 miles 7 e ssgt detail than POE39S butprovides many more lmages quot gor l owEarth Orbiting Track from pole to 4 pole l V Emilio hot coverthe same area Cover small strips Each pass sees an area tothe west of d L previous pass 39 1393 Sijh syh ohrohous path 39does not change with respect to sun relative ooord39 ate ystem 39 39 Completelrotatibh about every 15 hours ys ample aygiveh a39reaa few times per day Visible Images Record visible light from the sun that is re ected dr cloud land Oceans snow or ice quot 39Albedo 374 1 3052 072 microns 3 39 Angh and low Clouds look equally as bright and gt quotrage often indistinguishable ww WVv Visible Images Albedos Thunderstorm 8090 Lii39rmlli39s 39 70 smb39ke 20 i gBlackbody o Fresh snow cover 80 White Sands NM 60 Melting snow salt ats 50 Dry sandy soil 40 39 Clay granite glaciers 30 Tundra bare soil 20 Oceans lakes forest 10 Visible Image a GOESW10 Composite Visible Image 202 Tue Nov 10 1998 N Visible Imagery g W imm 7 Visible Imagery nfrared Images Record blackbody temperature of an object V 1 Ar o unt ofradiation T4 quot39Measures A 1021 1 2 microns 102112 pm wcl ouV di39top temperature in cloudy regions Bright clouds are COLD ciguds which are 3 u qay high eggsvaareh39ard to distinguish from the tKi agq fnfrared Images 202 Tue Nov 10 1998 Jrni 5 39 39 Comparison IR Imagery Water Vapor Images wasl i fWaz er Vapor Image 5 Comparison 2


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