Lecture 5: Weather Maps and Diagrams Flashcards
What are the two types of Thermodynamic Diagrams almost excessively used in the U.S.?
Skew-T and log-P
What are the 5 different sets of lines that are present in a Thermodynamic Diagram?
- 3 states: Pressure (P), Temperature (T), and mixing ratio (r)
- 2 processes: Dry Motion and Moist Motion
How does Pressure (hPa) lines look like in a Thermodynamic Diagram?
- Solid horizontal lines along the y-axis that represent pressure.
- The lines become more spread apart as height increases because of the logarithmic nature of pressure. (pressure decreases as height increases)
How does Temperature (C) lines look like in a Thermodynamic Diagram?
- Solid lines at a 45 degree angle, but values on the x-axis, making the the temperature lines appear “skewed”, which is why the diagram is called “skew-T”.
- The lines are evenly spaced in the x and y space.
How does Mixing Ratio (g/kg) look like in a Thermodynamic Diagram?
- Dashed lines also skewed, but greater than 45 degrees.
- The labels for the mixing ratio is displayed within the graph rather than on the axes.
- The mixing ratio also matches up with dew point temperature on x axis.
How does Dry Adiabats look like in a Thermodynamic Diagram?
- Solid skewed lines, but at a ~135 degree angle near y=0.
- A curved line.
- Used for tracking dry parcels
How do Moist Adiabats look like in a Thermodynamic Diagram?
- Also curved lines, but at a ~90-100 degree angle near y=0.
- Straight green or dotted line
- Used for tracking saturated parcels.
How to determine saturation from a Thermodynamic Diagram?
Saturated: T and Td are equal or very close on the graph.
Unsaturated: T and Td are not in the same location.
In a Skew-T log-P diagram, where is the dew point positioned relative to temperature for a non-saturated parcel?
The dew point is always positioned to the left or overlaying the actual temperature because for non-saturated air (dry rising parcel), the dew point temperature is always lower than the actual temperature.
In a Skew-T log-P diagram how can we determine the level at which a rising air parcel becomes saturated?
Dry parcels will follow the dry adiabatic lapse rate until it is saturated.
This process continues until the parcel reaches a level where it becomes saturated (where T = Td).
What is this formula and its variables? Δz=a(T − Td)
Calculating the height (Δz) to reach saturation.
Δz = heigh the parcel needs to rise to reach saturation
a = a constant that converts temperature difference to height
T = temperature
Td = dew point temperature
What happens to a rising parcel after it reaches Lifting Condensation Level (LCL)?
The rising air parcel starts to cool at the moist adiabatic lapse rate.
What is this formula and its variables θ=T(1000/P)^(0.285)?
The formula is for calculating the potential temperature (θ).
T = temperature of the parcel in Kelvin
P = pressure at the current level
What is the top left value on the station plot?
Temperature in Fahrenheit
What is the bottom left value on the station plot?
The Dew point in Fahrenheit
