ENVS 203 Exam 2 Study Guide

Atmospheric Moisture and Weather

• Humidity is a measure of the amount of moisture in the air.
• Spatial patterns of humidity vary by latitude and land vs. water.
• RH (Relative Humidity) and SH (Specific Humidity) are two measures of humidity, with RH describing the percentage of water vapor in the air compared to the maximum amount of water vapor the air can hold, and SH describing the total amount of water vapor in the air.
• Air temperature has a relationship with RH and SH, with warmer air able to hold more water vapor.
• Dew point is the temperature at which the air becomes saturated with water vapor and dew or frost begins to form.
• Daily pattern of RH varies, with highest RH usually occurring at night and lowest RH during the day.
• TPW (Total Precipitable Water) is a measure of the total amount of water vapor in the air, with a general spatial pattern of higher TPW near the equator and lower TPW near the poles.

Lifting Mechanisms and Clouds

• There are four lifting mechanisms: orographic, frontal, convective, and uplift.
• Lifting mechanisms can cause air to rise, cool, and condense, forming clouds.
• Clouds are classified into different types, including cumulus, stratus, and cirrus, each with a distinct shape and precipitation characteristics.
• Precipitation forming mechanisms include frontal, orographic, and convective precipitation.

Precipitation and Air Masses

• Precipitation can occur through various mechanisms, including hail formation.
• Latent heat is released during phase changes, such as when water vapor condenses into droplets.
• Air masses have distinct characteristics, including temperature and humidity, and can influence different regions of the US.
• Air masses can be classified into different types, including polar, tropical, and continental.

Fronts and Mid-Latitude Cyclones

• A front is the boundary between two air masses of different temperatures and humidity.
• Mid-latitude cyclones are low-pressure systems that form when a cold front meets a warm front.
• Mid-latitude cyclones have a basic structure, including a cold front, warm front, and occluded front.
• Types of fronts include cold, warm, and stationary fronts, each with distinct weather characteristics.
• Mid-latitude cyclones are associated with the polar jet stream and rotate counterclockwise in the Northern Hemisphere.

Thunderstorms

• Thunderstorms go through three stages: cumulus, mature, and dissipating.
• The three stages of thunderstorms last for a total of around 30 minutes to an hour.
• Thunderstorms are associated with cumulonimbus clouds.
• Updrafts dominate during the cumulus stage, while downdrafts dominate during the dissipating stage.