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Meterology Midterm
| Question | Answer |
|---|---|
| What can cause water vapor to condense out of the atmosphere? | The most effective way to cool the air until it becomes saturated. |
| What does atmospheric saturation depend on? | The air temperature. |
| What is the easiest way to cool the air? | To lift it |
| What happens to an air parcel as it rises into the atmosphere? | It moves into an area of lower pressure. |
| Do air parcels expand as they rise? | Yes |
| What causes the parcel to cool? | The "work" of expansion. |
| What is the rate at which the temperature cools by expansion? | Dry adiabatic lapse rate. |
| What does adiabatic mean? | "Not having anything to do with solar inputs." |
| What does the parcel or volume of air respond solely to? | The physics of fluid expansion/compression. |
| Does parcel exchange heat or energy with the surrounding air? | We have to assume it does not. |
| What is a better approximation, air parcels or adiabatic assumption? | Although air parcels do interact with their surroundings to some degree, the adiabatic assumption is a good first approximation. |
| What is the dry adiabatic lapse rate (DALR)? | The rate at which the air parcel cools is about -10C per km. |
| What does the negative sign in the DALR mean? | As elevation increases, the air parcel's temperature decreases. |
| How much does the temperature of the parcel decrease as it rises through the air? | By 10C every km it rises through the air. |
| If a parcel sinks through the atmosphere into an area of higher pressure, the parcel will be...? | Warmed by compression |
| Saturated (Moist) Adiabatic Lapse Rate | As the rising air parcel cools, what happens if it cools to its dew point? At that point, any further cooling will cause the water vapor in the parcel to begin to condense, and to release latent heat |
| What offsets the cooling due to expansion of the air parcel? | Release of latent heat partially off sets the cooling due to the expansion of the air parcel |
| Saturated Adiabatic Lapse Rate (SALR) Wet Adiabatic Lapse Rate or the Moist adiabatic lapse rate | If the parcel becomes saturated, any further lifting will cause the parcel to cool at the saturated adiabatic lapse rate |
| What does the saturated adiabatic lapse rate depend on? | The temperature of the saturated air parcel |
| Saturation vapor pressure curve | Warm Saturated Parcels contain a lot more moisture than cold saturated parcels |
| What does warm saturated parcels have a lot of? | Water vapor that can condense out, which releases a lot of latent heat within the parcel |
| What cools more slowly "wet" or "dry" air parcels? | Rising saturated "wet" air parcels always cool more slowly than rising unsaturated "dry" air parcels |
| What can cause the air to rise and cool (possible to saturation)? | Convergence near the center of low pressure, lifting of fronts, lifting by topography; surface heating (thermals) |
| Stability | Refers to a state of equilibrium |
| Stable | If the air parcel returns to its original position |
| Unstable | If the air parcel "keeps going" after being lifted |
| Neutral | If the air parcel stays where it is after being lifted |
| Determining the stability of the atmosphere | Comparing the temperature of out rising (or sinking) air parcel to the temperature of the air surrounding the parcel. |
| Environmental Lapse Rate | The change in temperature with height in the atmosphere surrounding the air parcel. It is related to the actual temperature in the atmosphere, which. typically, will be different from the temperature(s) inside our parcel |
| What is the environmental lapse rate measured by? | Radiosondes attached to weather balloons |
| How do we determine stability? | Comparing the temperature of the rising (saturated or unsaturated) air parcel to the temperature of the atmosphere surrounding the parcel. |
| What we know | Saturated adiabatic lapse rate depends on the temperature of the rising parcel, but for the examples below we will use a value of -6C/km, which is an average value of temperatures and pressures typically observed near the earth's surface. |
| Absolutely Stable | Occurs when a rising parcel of air is colder than its surroundings, regardless of whether the parcel is unsaturated ("dry") or saturated ("wet") |
| DALR | A parcel cooling at the dry adiabatic lapse rate is colder than its surroundings |
| SALR: If a parcel is cooling at the saturated adiabatic lapse rate it is...? | Also colder than its surroundings |
| When is the atmosphere absolutely stable? | When the environmental air is warmer than the air within either a dry parcel or a saturated parcel |
| Absolutely Unstable | Occurs when a rising parcel of air is warmer than its surroundings. regardless of whether the parcel is unsaturated ("dry") or saturated ("Wet") |
| A parcel cooling at the DALR is... | Warmer than its surroundings |
| A parcel cooling at the SALR also is.... | Warmer than its surroundings |
| This is very rare... | The atmosphere is absolutely unstable when the environmental air is cooler than the air within either a dry parcel or a saturated parcel |
| Conditionally unstable | Occurs when a rising parcel of unsaturated ("dry") air is colder than its surroundings, but a rising parcel of saturated ("wet") air is warmer than its surroundings. Depends on whether the rising parcel is unsaturated ("dry") or saturated ("wet") |
| Conditionally unstable stated another way | The atmosphere is conditionally unstable when the environmental air is warmer than the air within a dry parcel but cooler than the air within a saturated parcel. |
| Neutrally Stable | Occurs when a rising parcel of air has the same temperature as its surroundings (not as common as the other three conditions) |
| Neutrally Stability for unsaturated air | occurs when the environmental lapse rate equals the dry adiabatic lapse rate. |
| Neural Stability for saturated air | occurs when the environmental lapse rate equals the saturated adiabatic lapse rate |
| Atmospheric stability depends.. | on the environmental lapse rate |
| What can change the stability of the atmosphere--in other words, what can change the environmental lapse rate? | Some processes that destabilize the atmosphere, daytime heating, cold air advection aloft, warm air advection, cold air being heated by moving over a warmer surface |
Created by:
meganvu19
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