Chapter 6 Physical Geography Exam 2

What are the two mechanisms needed for the formation of the precipitation?

Collision/Coalescence, and Ice-crystal formation

List in order components of the Hydrologic Cycle. (Figure 6-1)

Evaporation (from ocean), Condensation (in clouds), Precipitation (rain), moist air in between clouds, Condensation (clouds), Precipitation (rain),

Glaze

(freezing rain) Rain that turns into ice the instant in collides into a solid object. Raindrops fall through a shallow layer of subfreezing air near the ground. Although the drops do not freeze in the air, they become supercooled while in this cold layer and instantly converted to an icy surface when they land. The result can be a thick coating of ice that can be hazardous.

Latent heat of fusion

Energy released as water freezes

Cumulus

Tall, narrow, puffy

Cirrocumulus

Thin, white, icy

Describe the components of the Hydrologic Cycle. (Figure 6-1)

Unending circulation of our planets water supply; essential feature is that liquid water (primarily from oceans) evaporates into the air, condenses to the liquid (or solid) state, and returns to Earth as some form of precipitation; important determinate of climate;

Latent heat of vaporization

Energy required to convert liquid water to water vapor.

Describe the chemical structure of a water molecule.

A water molecule is made up of 2 Hydrogen atoms and one Oxygen atom. Hydrogen bonds form between water molecules because the negatively charged atom side of one molecule is attracted to the positively charged hydrogen side of another molecule.

Absolute Humidity (Contrast)

Absolute humidity is the measure of water vapor in the air; the mass of water vapor in a given volume of air. If the volume of air changes the value of absolute humidity also changes even though the total amount of water vapor remains the same; generally not used to describe moisture in the air that is rising or decreasing.

Stratiform clouds

Appear as grayish sheets that cover most or all of the sky; rarely broken up into individual cloud units

Convective lifting (6-32a)

Because of unequal heating of different surface areas, a parcel of air near the ground may be warmed by conduction more than the air around it. The density of the warm air is reduced as the air expands and so the parcel rises toward a lower-density layer.

Describe the relationship of temperature to relative humidity.

Changes as the temperature changes even if the amount of water vapor remains the same; as temperature increases, relative humidity decreases, as temperature decreases, relative humidity increases. In the morning, the temperature is low, and RH is high because the airs water vapor capacity is low.

Identify the major cloud forms and types

Cirriform clouds, stratiform clouds, cumuliform clouds

Explain cloud formation

Clouds are collections of minute droplets of liquid water or tiny crystals of ice; they are the visible expression of condensation and provide perceptible expression of other things happening in the atmosphere.

Describe conditions associated with relatively low rates of evaporation.

Cold water, cool air, when large amounts of water vapor are present in the air, when air overlying a water surface is almost saturated with water, if air remains calm and the temperature does not change,

Vapor Pressure

Contribution of water vapor to the total pressure of the atmosphere;

List the four types of atmospheric lifting and precipitation.

Convective lifting, orographic lifting, frontal lifting, convergent lifting.

Upslope or orographic fog

Created by adiabatic cooling when humid air climbs a topographic slope.

Advection fog

Develops when warm, moist air moves moves horizontally over a cold surface, such as snow-covered ground, or a cold ocean current. Air moving from sea to land is the most common source of advection fogs.

Saturated adiabatic lapse rate

Diminished rate of cooling during condensation; averages 6 degrees C per 1000 meters

Dry adiabatic lapse rate

Dry adiabatic lapse rate: As a parcel of unsaturated air rises, it cools at the relatively steady rate of 10 degrees C per 1000 meters. The air is not necessarily dry, just unsaturated; under many circumstances, the LCL is clearly visible as the often flat base of the clouds that form.

Stratocumulus

General overcast

Supersaturated

Has a relative humidity greater than 100 percent; occurs whenever there is no surface available for condensation to occur, the air becomes supersaturated.

Contrast the concepts of stable and unstable air.

High stability is promoted whenever cold air is beneath warm air; Unstable air occurs when a mass of air is warmer than the surrounding air.

Describe ice-crystal formation.

Ice crystals grow at the expense of water droplets until the crystals are large enough to fall; as they descend through the lower, warmer portions of the cloud, they pick up more moisture and become even larger. They may then either precipitate, or melt. Proposed by swedish meteorologist Tor Bergeron. It is now known as the Bergeron process, and is believed to account for a majority of precipitation outside of tropical regions.

Sleet

In U.S. it is considered small raindrops that freeze during descent and reach the ground as small pellets of ice. In other countries, it is considered a mixture of rain and snow

Altocumulus

Layered or puffy; made of liquid water

List the physical properties of water.

Liquidity, ice expansion, surface tension, capillarity, solvent ability, and specific heat.

Cumuliform clouds

Massive or rounded, usually with a flat base and limited horizontal extent, but often billowing upward to great heights.

Rain

Most common and widespread form of precipitation; consists of droplets of liquid water; Most rain is the result of condensation and precipitation in ascending air that has a temperature above freezing. Categorized by rain (relatively long time, showers (brief with big drops), and drizzle (small drops long periods of time).

Snow

Name generally given to solid precipitation in form of ice crystals, small pellets, or flakes. Formed when water vapor is converted directly to ice through sublimation without an intermediate liquid stage.

List the region in the US that has the most precipitation.

Northwest.

Hail

Precipitation form with the most complex origin; consists of either small pellets or larger lumps of ice. Usually composed of roughly concentric layers of clear and cloudy ice. The cloudy portions contain numerous tiny air bubbles among small crystals of ice, whereas the clear parts are made up of large crystals of ice.

Describe the process of condensation.

Process by which water vapor is converted into liquid water; in order for it to occur the air must be saturated. Relative humidity and temperature are key factors in condensation

Describe collision/coalescence.

Process most responsible for precipitation in the tropics, and produces some rain at mid latitudes. Droplets of rain must coalescence (merge) into larger droplets; large droplets fall faster than small ones, then large droplets break into several small drops which grow by accretion

Identify the 5 forms of precipitation

Rain, snow, sleet, glaze, hail

Define the term 'sensible temperature'.

Refers to the temperature as it feels to a persons body. It involves not only the actual air temperature, but also other atmospheric conditions, particularly relative humidity and wind, that influence our perception of warmth and cold. Wind movement also influence sensible temperature, primarily its influence on evaporation and the convection of heat away from the body.

Radiation fog

Results when the ground loses heat through radiation, usually at night

Evaporation fog

Results when water vapor is added to cold air that is already near saturation.

What are the three physical states of water?

Solid, Liquid, Gas

Explain the importance of physical properties of water.

The different properties allow water molecules to combine in an effective way depending on their "state".

Latent heat of melting

The energy required to melt ice;

Specific Humidity (Contrast)

The mass of water vapor in a given volume of air; changes only as the quantity of water vapor changes, and is not affected by variations in air volume as absolute humidity is. Particularly useful in studying the characteristics and movement of air masses.

Describe the relationship of temperature to absolute humidity.

The maximum absolute humidity for a parcel of air is limited by temperature: cold air has a small maximum absolute humidity and warm air has a great maximum absolute humidity.

Evapotranspiration

The process whereby plants give up moisture through their leaves, is called transpiration, and so the combined process of water vapor entering the air from land sources .

Describe the term 'dew point'.

The temperature at which saturation is reached; varies with the moisture content in the air; useful way of describing actual water vapor content of a parcel of air.

Cirriform clouds

Thin and wispy; composed of ice crystals rather than water droplets

Orographic lifting (6-32b)

Topographic barriers that block the path of horizontal air movements are likely to cause large air masses of air to travel upslope. This can produce orographic precipitation if the ascending air is cooled to the dew point.

Describe conditions associated with relatively high rates of evaporation.

Warm water, warm temperature, when little water vapor is present in the air, as air gets closer to saturation, and if air/wind is in motion (dispersing of water vapor molecules).

Supercooled

Water than persists in liquid form at temperature below freezing; important to condensation because they promote the growth of ice particles in clouds by freezing around the participles or by evaporating into vapor form which molecules are readily added to the ice crystals.

Describe the relationship of capacity and actual water vapor in the air to relative humidity.

Water vapor capacity is the maximum amount of water vapor that can be in the air at a given temperature; cold air has low vapor capacity, warm air has high vapor capacity; water vapor capacity is determined by temperature, which determines the rate of vaporization of water. Relative humidity = actual water vapor in air/capacity x 100

What are the phase changes of water?

Water, ice, water vapor

Convergent lifting (6-32d)

When air converges, the result in general uplift because of the crowding. This forced uplift enhances instability and is likely to produce showery precipitation. It is frequently associated with cyclonic storm systems, and is particularly characteristic of the low latitudes. Common in the inter tropical convergence zone. Also in hurricanes.

Frontal lifting (6-32c)

When unlike air masses meet, they do not mix. Instead, a zone of discontinuity called a front is established, and the warmer air rises over the cooler air. As the warmer air is forced to rise, it may be cooled to the dew point with resulting clouds and precipitation. Characterized at mid latitudes.

What are the four types of fog?

radiation, advection, upslope, evaporation