AT351 Lab Seven Skew-T Stability Analysis

Transcription

1 AT351 Lab Seven Skew-T Stability Analysis Twice a day, all around the planet, small instrument packages called radiosondes are launched into the atmosphere using balloons. These instruments record the atmospheric temperature, dewpoint, wind speed, and wind direction, and radio the data back to the observers on the ground. The data is particularly useful to analyze the stability of the atmosphere, since the radiosonde reports the environmental temperature and dewpoint profiles. In order to make this stability analysis easier, meteorologists like to plot the environmental sounding on a chart that has overlaid on it lines representing the dry- and moist-adiabatic curves. We call such a chart a skew-t chart. In order to analyze the stability of the environment, then, all a meteorologist has to do is draw the parcel s path using the dry- and moist-adiabatic lines as a guide. Then, one simply compares the parcel s trajectory to the environmental data as reported by the radiosonde data to analyze stability. In this lab, you ll analyze three different soundings: one from Albuquerque, New Mexico (chart 1), one from the Grand Caymans (chart 2), and one from Kodiak, Alaska (chart 3.) Here s what s shown on the charts: the pressure is represented by horizontal solid blue lines, the temperature scale is represented by diagonal solid blue lines, the dry adiabatic lapse rate is represented by dashed red lines, the moist adiabatic lapse rate by dashed green lines, and lines of constant mixing ration by dashed yellow lines. The environmental temperature profile is drawn in solid red, and the environmental dewpoint is drawn in solid green. (Don t worry if this sounds like a lot by the end of this lab, it ll all be second nature.)

2 Question 1: (20 points total) Chart 1 (Albuquerque, New Mexico) a.) (5 points) Look at the bottom of the sounding. What is the surface temperature in degrees C? What is the surface dewpoint in degrees C? b.) (5 points) Starting from the surface dewpoint temperature, follow the yellow constant-mixing ratio lines up. Starting from the surface temperature, follow the red dashed dry adiabatic curve up, until it intersects with the dewpoint line you just drew. This is the parcel s Lifting Condensation Level (LCL) where the relative humidity is 100%. What is the pressure in millibars of the LCL? c.) (5 points) From your LCL, follow the parcel up along the green dashed moist adiabatic line up to 200 millibars. Does the parcel ever intersect the environmental temperature? If so, where? d.) (5 points) Before reaching the LCL, is the parcel stable or unstable? After reaching the LCL, is the parcel stable or unstable?

3 Question 2: (20 points total) Chart 2 (Grand Cayman Islands, Caribbean) a.) (5 points) Look at the bottom of the sounding. What is the surface temperature in degrees C? What is the surface dewpoint in degrees C? b.) (5 points) Starting from the surface dewpoint temperature, follow the yellow constant-mixing ratio lines up. Starting from the surface temperature, follow the red dashed dry adiabatic curve up, until it intersects with the dewpoint line you just drew. This is the parcel s Lifting Condensation Level (LCL) where the relative humidity is 100%. What is the pressure in millibars of the LCL? c.) (5 points) From your LCL, follow the parcel up along the green dashed moist adiabatic line up to 200 millibars. Does the parcel ever intersect the environmental temperature? If so, where? d.) (5 points) Before reaching the LCL, is the parcel stable or unstable? After reaching the LCL, is the parcel stable or unstable?

4 Question 3: (20 points total) Chart 3 (Kodiak, Alaska) a.) (5 points) Look at the bottom of the sounding. What is the surface temperature in degrees C? What is the surface dewpoint in degrees C? b.) (5 points) Starting from the surface dewpoint temperature, follow the yellow constant-mixing ratio lines up. Starting from the surface temperature, follow the red dashed dry adiabatic curve up, until it intersects with the dewpoint line you just drew. This is the parcel s Lifting Condensation Level (LCL) where the relative humidity is 100%. What is the pressure in millibars of the LCL? c.) (5 points) From your LCL, follow the parcel up along the green dashed moist adiabatic line up to 200 millibars. Does the parcel ever intersect the environmental temperature? If so, where? d.) (5 points) Before reaching the LCL, is the parcel stable or unstable? After reaching the LCL, is the parcel stable or unstable?

5 Question 4: (10 points) a.) (5 points) Which sounding was the most unstable? Which sounding had the lowest surface dewpoint? Which sounding had the highest LCL? b.) (5 points) At which location would you expect afternoon thunderstorms? At which location would you expect clear skies?

6 Chart 1: Albuquerque, New Mexico

7 Chart 2: Grand Cayman Island, Caribbean

8 Chart 3: Kodiak, Alaska