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ATM OCN 100 101 Week 7 Stability and Vertical Motion Reading AK Ch 3 and 4 Sections on Stability Buoyancy and Temperature in the Atmosphere Static Stability and Cloud Formation Thunderstorms Learning Objectives Determine cloud features from a sounding LCL LFC Cloud Top Explain stability for a layer of air in the atmosphere Use a sounding to determine stability by comparing the environmental lapse rate to the dry or moist adiabatic lapse rate Describe the kind of weather one might expect after calculating stability in an atmospheric sounding 1 2 10 16 24 1 Cloud Top Any further cooling and parcel becomes colder than its surroundings LFC Parcel first becomes warmer than its surroundings we may not always see it LCL Parcel s temperature equals its dewpoint always temperature of colder than the environment a leveconvection free not 3 4 Learning Objectives Determine cloud features from a sounding LCL LFC Cloud Top Explain stability for a layer of air in the atmosphere Use a sounding to determine stability by comparing the environmental lapse rate to the dry or moist adiabatic lapse rate Describe the kind of weather one might expect after calculating stability in an atmospheric sounding 10 16 24 2 Definiton Stability Stability A measure of the likelihood that a physical system will remain unchanged after it is perturbed Stableaor X unstable situation L 5 6 Concept Stability Refers to the likelihood that a parcel if disturbed from its original position will Return to its origin stable Accelerate away from its origin unstable Be at equilibrium with its environment neutral Key Compare the environmental lapse rate to the rate at which a parcel would warm or cool if disturbed from its original position 10 16 24 3 Learning Objectives Determine cloud features from a sounding LCL LFC Cloud Top Explain stability for a layer of air in the atmosphere Use a sounding to determine stability by comparing the environmental lapse rate to the dry or moist adiabatic lapse rate Describe the kind of weather one might expect after calculating stability in an atmospheric sounding Environmental Lapse Rate Definitions Environmental Lapse Rate Rate at which temperature decreases with height positive when temperature gets colder with height Typically 6 5C km in the troposphere latexit sha1 base64 H1yLHD0m4 T962AKuZLGFlZQ1vU AAACH3icbVBNS8NAEJ3Ur1q ol4EL4tF8NKSiKgXoehBjwqtFZpQNtuNLt1Nwu5GaEP iRf ihcPiog3 43btAdtfbDsmzczzMwLEs6UdpxvqzQ3v7C4VF6urKyurW Ym1u3Kk4loS0S81jeBVhRziLa0kxzepdIikXAaTvoX4zy7UcqFYujph4k1Bf4PmIhI1gbqWsfe5dYCIzOUM1FnmaCKuSFEpOs2c2aOaoh85 neTachMMi7NpVp 4UQLPEnZBqYwcKXHftL68Xk1TQSBOOleq4TqL9DEvNCKd5xUsVTTDp43vaMTTCZhE K 7L0b5ReiiMpXmRRoX6uyPDQqmBCEylwPpBTedG4n 5TqrDUz9jUZJqGpHxoDDlSMdoZBbqMUmJ5gNDMJHM7IrIAzbuaGNpxZjgTp88S24P6 5x ejmqNo4H7sBZdiFPTgAF06gAVdwDS0g8AQv8Abv1rP1an1Yn PSkjXp2YY sL5 ABu oeY latexit 1 TT TB zT zB Rate 7 8 10 16 24 4 Environmental Lapse Rate The dry and moist adiabatic lapse rates refer to the rate at which a parcel will cool or warm if it is rising or falling in our atmosphere These lapse rates can be compared to the Environmental Lapse Rate which describes the lapse rate of the air around the parcel The environmental lapse rate can be determined from a sounding determineding ENVIRONMENTAL TEMPERATURE RISING PARCEL Stability First Determine the environmental lapse rate at a given elevation from the sounding Next compare the environmental lapse rate to the moist and dry adiabatic lapse rates at that elevation Let s take a closer look at this 9 10 10 16 24 5 Absolutely Stable Suppose Environmental Lapse rate is 4 C per 1000m m T H G I E H Absolutely Stable Suppose Environmental Lapse rate is 4 C per 1000m If the parcel is unsaturated then as it is lifted it will be colder than its surroundings lot colder so it would drop back down m T H G I E H 11 12 10 16 24 Temperature C Temperature C 6 10 16 24 Absolutely Stable Suppose Environmental Lapse rate is 4 C per 1000m If the parcel is unsaturated then as it is lifted it will be colder than its surroundings If the parcel is saturated then as it is lifted it will also be colder than its surroundings m T H G I E H de absolutya Temperature C 13 14 Absolutely Stable Absolutely Stable Environmental Lapse Rate is less than the moist adiabatic lapse rate If a parcel is vertically displaced it will return to its original position regardless of whether it is saturated or unsaturated m T H G I E H Temperature C 7 10 16 24 This sounding is for 12Z or around 7am As the day progresses assume the surface temperature warms to 15C What kinds of clouds might form Very Stable Absolutely Unstable Suppose Environmental Lapse rate is 12 C per 1000m m T H G I E H 15 16 very rare Temperature C 8 Absolutely Unstable Suppose Environmental Lapse rate is 12 C per 1000m If the parcel is unsaturated then as it is lifted it will be warmer than its surroundings m T H G I E H warmerthan theo a Temperature C Absolutely Unstable Suppose Environmental Lapse rate is 12 C per 1000m If the parcel is unsaturated then as it is lifted it will be warmer than its surroundings If the parcel is saturated then as it is lifted it will also be warmer than its surroundings m T H G I E H ounotwara Temperature C 17 18 10 16 24 9 Absolutely Unstable Absolutely Unstable Environmental Lapse Rate is greater than the dry adiabatic lapse rate If a parcel is vertically displaced it will accelerate away from its original position regardless of whether it is saturated or unsaturated m T H G I E H Conditionally Unstable Suppose Environmental Lapse rate is 8 C per 1000m m T H G I E H 19 20 10 16 24 Temperature C Temperature C 10 10 16 24 Conditionally Unstable Suppose Environmental Lapse rate is 8 C per 1000m If the parcel is unsaturated then as it is lifted it will be colder than its surroundings sinks back because colder environment the than m T H G I E H Z Temperature C 21 22 Conditionally Unstable Suppose Environmental Lapse rate is 8 C per 1000m If the parcel is unsaturated then as it is lifted it will be colder than its surroundings BUT If the parcel is saturated then as it is lifted it will be warmer than its surroundings m T H G I E H Temperature C 11 Conditionally Unstable Conditionally Unstable Environmental Lapse Rate is between the dry and moist adiabatic lapse rate If a parcel is vertically displaced its stability depends on is conditioned on whether the parcel is saturated or not m T H G I E H Temperature C This sounding is for 12Z or around 7am As the day progresses assume

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