METEO 003

LAB 6 Due Friday Oct. 17th

Chapter 8 Question 1 a,b,c

• Radiosonde: instrument carried by a weather balloon to measure atmospheric variables (such as temperature, pressure, relative humidity, etc) in the vertical direction• Lapse rate is the rate of decrease of temperature with altitude • Dry Adiabatic Lapse Rate: 10°C/km • Moist Adiabatic Lapse Rate: 6°C/km

• Layer lapse rate = temperature (bottom of layer) – temperature (top of layer) thickness of layer (distance from top to bottom)

Stability Review

• Stable Equilibrium (“Stable” atmosphere)• When a parcel is moved upward or downward, forces act to return it to it’s

original altitude (bowl with ball in it)

• Unstable Equilibrium (“Unstable” atmosphere)• When a parcel is moved upward or downward, forces act to accelerate it

away from it’s original altitude (upside-down bowl with ball on top)

Chapter 8 Question 1 a,b,c

• Ways to test stability:• Compare lapse rate of layer to dry and moist adiabatic lapse rates

• Stable: Layer lapse rate < 6°C/km (Γm)• Unstable: Layer lapse rate > 10°C/km (Γd )• Conditionally unstable: Layer lapse rate is between 6°C/km and 10°C/km

• Lift parcel of air from bottom of layer to top of layer (cool air parcel by dry or moist lapse rate)• Stable: temperature of air parcel is colder than environment after lifting the parcel• Unstable: temperature of air parcel is warmer than environment after lifting it

Chapter 8 Question 2 a,b,c,d

• Windward Side of Mountains: rising motion and clouds• Leeward side of Mountains: sinking motion and rain shadow• Use information on the last three slides to do this problem

• Example: • Wind is forcing air originating at sea level (0m) to rise over a mountain with a peak of 3000m.

Temperature and dew point of air at sea level is originally 20°C and 5°C respectively. Environmental temperature at peak of mountain is 0°C.

• Questions:• a. What elevation will a cloud form?• b. What will the temperature of the rising air be once it reaches the peak of the mountain?• c. Is the atmosphere at the peak unstable or stable?• d. What will the temperature of the air be once it sinks down the other side of the mountain?

Example

• Wind is forcing air originating at sea level (0m) to rise over a mountain with a peak of 3000m. Temperature and dew point of air at sea level is originally 20°C and 5°C respectively. Environmental temperature at peak of mountain is 0°C. • Questions:

• a. What elevation will a cloud form? (assume constant dew point)

20°C - 5°C = 15°C difference between temperature and dew point Air Parcel needs to cool 15°C so: 10°C = 15°C 10x°C = 15°C*km 1 km x x = 1.5km = 1500m

1500m – 0m (sea level) = 1500m is the elevation the parcel must rise for a cloud to form

Example

• Wind is forcing air originating at sea level (0m) to rise over a mountain with a peak of 3000m. Temperature and dew point of air at sea level is originally 20°C and 5°C respectively. Environmental temperature at peak of mountain is 0°C. • Questions:

• b. What will the temperature of the air be once it reaches the peak of the mountain?

3000m – 1500m = 1500m still to rise from cloud formation to peak of mountain So: 6 °C = _ x _ 1x km = 9°C*km 1 km 1.5 km x = 9°C

5 °C – 9 °C = -4 °C is the temperature of the air parcel once it reaches the peak

Example

• Wind is forcing air originating at sea level (0m) to rise over a mountain with a peak of 3000m. Temperature and dew point of air at sea level is originally 20°C and 5°C respectively. Environmental temperature at peak of mountain is 0°C. • Questions:

• c. Is the atmosphere at the peak unstable or stable?

Temperature of air parcel at the peak of the mountain is -4 °C vs an environmental temperature at the peak of the mountain of 0 °C so the air parcel is negatively buoyant and stable

Example

• Wind is forcing air originating at sea level (0m) to rise over a mountain with a peak of 3000m. Temperature and dew point of air at sea level is originally 20°C and 5°C respectively. Environmental temperature at peak of mountain is 0°C. • Questions:

• d. What will the temperature of the air be once it sinks down the other side of the mountain? (assume unsaturated now)

Air Parcel needs to sink 3000m so: 10°C = x 1x km = 30°C*km 1 km 3 km x = 30°C

30 °C + -4 °C = 26 °C is the temperature of the air parcel when it descends back to sea level * this is warmer than it originally was at sea level before traveling over the mountain

Chapter 8 Question 7 a,b

• Assuming air is unsaturated…use dry adiabatic lapse rate

• Standard room temperature is ~70-77⁰F so for Part B think about if that air temperature is comfortable immediately after it was pressurized

Chapter 8 Question 9 a

• Unstable: Bubbly appearance • Stable: flat appearance

Chapter 8 Question 11 a,b

• For Part A: also state what the wind direction is• Look at cloud type/texture of clouds

on visible image and relate that to stability• What can be said about the

temperature near the ground/water assuming the air up above is the same temperature over the entire image area?

Chapter 9 Question 2

• Speed of sound [m/s] = 20*sqrt(T [K]) *note temperature is in Kelvins

• Converting Fahrenheit to Celsius: ⁰C = 5/9(⁰F - 32)• Converting Celsius to Kelvin: K = ⁰C + 273.15

• Speed [m/s] = distance [m] / time [s]• Rearrange equation to get: Time [s] = distance [m] / speed [m/s]

Chapter 9 Question 6 a,b

• Height of cloud base for a thunderstorm would be where the temperature and dew point are equal (air becomes saturated)

• Use dry adiabatic lapse rate here to determine height of cloud base

*HINT for Part B: High-based t-storms lead to evaporation of the rain before it reaches the ground, which leads to fires

Figure 9.26

LAB 6 Due Friday Oct. 17th

• 8.1a(5),b(5),c(3) Dry Adiabatic Lapse Rate: 10°C/km, Moist Adiabatic Lapse Rate: 6°C/km

• 8.2a(2),b(2),c(2),d(2) reference the example• 8.7a(3),b(2) Sinking air warms• 8.9a(2) flat or bubbly appearance?• 8.11a(2),b(4) To part a add "what is the wind direction?" Look at cloud type and relate

to stability. What does that say about the temperature near the ground/water assuming the air above is the same temperature over the land and water?

• 9.2 (3) Convert temperature from Fahrenheit to Kelvin conversion [⁰C = 5/9(⁰F - 32), K = ⁰C + 273.15]

• 9.6a(2),b(1) High-based t-storms lead to evaporation of the rain before it reaches the ground, which leads to fires