Midterm Unit Two Flashcards
Why are we interested in finding the value of ρ for moist air?
To assess if it is buoyant or not
What is the law of partial pressure?
Partial pressure: pressure a gas would exert if it were alone in the same volume at the same temperature.
It states that the total pressure is the some of each partial pressure in a gas.
Suppose you have a hurricane. What does convergence/divergence of flow tell you about the vorticity and thus sense of rotation at each level.
Divergence generates vorticity.
Convergence->negative divergence->positive vorticity-> ccw : this is at low level so generation of cyclonic vorticity
Divergence->positive divergence->negative vorticity->cw
What does pressure tendency at the surface’s equation state?
It states that the pressure tendency at the surface is the total convergence of mass into the atmospheric column
What is T_v
It is the virtual temperature which is the temperature that the parcel would need for its density to be maintained if all moisture were removed with the pressure held constant
Does a sample of dry air @ given T and p need to cool or warm to become as light as sample of moist air @ given T and p?
It need to have its temperature raise
What is the saturation vapour pressure?
It is the pressure at which there is equilibrium between liquid water that evaporates from a water surface into the air layer and water vapour that condenses into liquid water.
How can we estimate the density of a saturated air mass?
For any pair of p,T values we can estimate the corresponding Tv and thus the density ρ_saturated in the above condition.
What is Td?
It is the temperature dew point. The temperature to which an airmass must be cooled @ constant pressure so that it becomes saturated
What happens when we lower T to Td?
The air mass becomes saturated but w has not changed until saturation. RH does.
What is Tw?
It is the temperature of the air around an evaporative raindrop. It is the temperature that the air mass will acquire if water vapour is evaporated until the air mass reaches saturation.
What is the difference between cooling from T to Tw
and from T to Td
T -> Tw: Saturation through addition of water vapour. It is the absorption of latent heat by process of evaporation. Saturation achieved faster (1. External addition of water vapour 2. evaporative cooling)
T-Td: Saturation through cooling. It is externally imposed.
Td
What are the conditions for a dry adiabatic lapse rate?
Hydrostatic atmosphere
No exchange of heat with the air surrounding it
Without reaching saturation at any point
What is the internal energy of an air-mass?
It is the microscopic energy that an air mass has due to the potential E and KE of its molecules/atoms.
T increases:
- increase of KE so U
- change in phase so PE so U
What is cv?
It is the specific heat cv: the amount of heat dq required to be given to 1kg of air for its T to increase by amount dT with its volume kept constant.
