Weather Journals: a. copying forecast text b. figure captions. d. citing source material e. units

Transcription

1 Weather Journals: a. copying forecast text b. figure captions c. linking figures with text d. citing source material e. units

2 In the News:

3 In the News: warmer waters in the Pacific wind shear in the Atlantic

4 In the News: Rainfall from Typhoon Parma

5 Guest Lecture Tuesday: Forecasting: Mike Heard

6 Cloud Development and Forms (ERTH 303, 15 October 2009) a. Mechanisms that lift air [and cool air to the dew point] b. Static ti stability and the ELR c. Factors Influencing the ELR d. Limitations it ti and inversions Clouds enveloping the Bridger Range, with sundog. 6

7 Review: How does air become saturated? 1. Add water vapor to the air e.g. Warm shower: add vapor to air 2. Mix cold air with warm, moist air e.g. Contrails behind jets traveling at high altitudes; steam fog 3. Cool air to the dewpoint 7

8 a. Mechanisms that lift air 1. Orographic uplift: Upward displacement of air that leads to adiabatic cooling Responsible for creating a rain shadow, an area of lower precipitation on the leeward side of a mountain (range).

9 c. Adiabatic cooling Dry adiabatic lapse rate = 10 C / 1 km Wet adiabatic lapse rate = 5 C / 1 km Dew point lapse rate = 2 C / 1 km Windward Side Dew Elev. Temp Point (m) ( C) ( C) Lifting condensation level = elevation at which an air parcel reached the dew point temperature Leeward Side Dew Elev. Temp Point (m) ( C) ( C) At what elevation would cloud bases form? 2. How do sea-level temperature, dew point, and humidity on the leeward vs. windward side of the mountain range vary? 1000 Sea level Which side of the mountain is more often Sea cloudy and which side is more often clear? level 9

10 c. Adiabatic cooling Dry adiabatic lapse rate = 10 C / 1 km Wet adiabatic lapse rate = 5 C / 1 km Dew point lapse rate = 2 C / 1 km Windward Side Dew Elev. Temp Point (m) ( C) ( C) Lifting condensation level = elevation at which an air parcel reached the dew point temperature Leeward Side Dew Elev. Temp Point (m) ( C) ( C) Lifting condensation level Sea level 1. At what elevation would cloud bases form? How do sea-level temperature, dew point, and humidity on the leeward vs. windward side of the mountain range vary? Which side of the mountain is more often Sea cloudy and which side is more often clear? level

11 a. Mechanisms that lift air 2. Frontal lifting: Air flow along frontal boundaries resulting in widespread cloud development Cold front Warm front

12 a. Mechanisms that lift air 3. Convergence: Horizontal movement towards a common Horizontal movement towards a common location

13 a. Mechanisms that lift air 4. Localized convection: Lifting from heating of the boundary layer (Chap. 3)

14 b. Static Stability and the ELR Static stability: air s susceptibility to uplift Statically unstable: becomes buoyant, continues to rise Statically stable: resists upward displacement, sinks to original level Statically neutral: neither rises on its own nor sinks, rests where it was displaced.

15 b. Static Stability and the ELR Buoyancy of a rising air parcel depends on its rate of cooling relative to the surrounding air. Air parcel: dry or moist adiabatic lapse rate (DALR or MALR) Surrounding air: environmental lapse rate (ELR)

16 b. Static Stability and the ELR Absolutely unstable air: Air parcels cools less than ambient air ELR > DALR (If ELR > DALR, then ELR also > MALR)

17 b. Static Stability and the ELR Absolutely stable air: Air parcels cools more than ambient air ELR < MALR (If ELR < MALR, then ELR also < DALR)

18 b. Static Stability and the ELR Conditionally unstable air: Buoyancy of air changes DALR < ELR < MALR L l f f ti Level of free convection: Altitude a parcel of air Reach for it to become buoyant and rise on its on

19 b. Static Stability and the ELR ELR > DALR

20 b. Static Stability and the ELR ELR < MALR

21 b. Static Stability and the ELR DALR < ELR < MALR

22 06.02 Uplift along a cold front occurs because the cold air is than the air it pushes against. 1. lighter 2. denser 3. slower 4. more unstable

23 06.02 Uplift along a cold front occurs because the cold air is than the air it pushes against. 1. lighter 2. denser 3. slower 4. more unstable

24 06.04 This is an example of air that is. 1. conditionally stable 2. conditionally unstable 3. absolutely stable 4. absolutely unstable

25 06.04 This is an example of air that is. 1. conditionally stable 2. conditionally unstable 3. absolutely stable 4. absolutely unstable

26 Cloud Development and Forms (ERTH 303, 15 October 2009) a. Mechanisms that lift air [and cool air to the dew point] b. Static ti stability and the ELR c. Factors Influencing the ELR d. Limitations it ti and inversions 26 Clouds enveloping the Bridger Range, with sundog.

27 c. Factors influencing the ELR 1. Heating or cooling the atm. Diurnal temperatures: t

28 c. Factors influencing the ELR 2. Advection of cold and warm air at different levels

29 c. Factors influencing the ELR 3. Advection of an air mass with a different ELR

30 Cloud Development and Forms (ERTH 303, 15 October 2009) a. Mechanisms that lift air [and cool air to the dew point] b. Static ti stability and the ELR c. Factors Influencing the ELR d. Limitations it ti and inversions 30 Clouds enveloping the Bridger Range, with sundog.

31 d. Limitations on lifting unstable air 1. Unstable air stops ascent when it reaches a layer of stable air

32 d. Limitations on lifting unstable air 2. Entrainment: mixing of air parcel with ambient air Pyrocumulus cloud, Alaska.

33 d. Extremely stable air: Inversions Inversions: temperature increases with altitude

34 d. Extremely stable air: Inversions Inversions: Radiation inversion diabatic cooling Frontal inversions i Subsidence inversions