LAB 6 Due Friday Oct. 17 th

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 (Γ m
)
• Unstable: Layer lapse rate > 10°C/km (Γ d
)
• 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
Figure 9.26
* HINT for Part B : High-based t-storms lead to evaporation of the rain before it reaches the ground, which leads to fires

LAB 6 Due Friday Oct. 17 th
• 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