Weather and Water Cycle: Humidity, Apparent Temperature, and Atmospheric Stability

Apparent temperature

The temperature it feels like, not the actual air temperature.

Dew point temperature

Temperature at which condensation occurs; also a measure of moisture in the atmosphere.

Heat Waves

Periods of excessively hot weather, which can lead to increased mortality.

Hydrologic Cycle

The continuous movement of water on, above, and below the surface of the Earth.

Evapotranspiration

The sum of evaporation from the land and transpiration from plants.

Properties of Water

Key component of Earth-Atmosphere System; absorbs, transports, and releases energy.

Hydrogen bonds

Weak bonds between hydrogen and oxygen atoms in water molecules.

Cohesion

Water molecules join to other water molecules.

Adhesion

Water molecules join to other objects.

Latent heat of water

Energy that is absorbed or released during a state change of water.

Sensible heat

Heat that causes a change in temperature but not a change in state.

Vapor pressure

Portion of air pressure exerted by molecules of water vapor.

Hygrometers

Instruments that measure water vapor in the atmosphere.

Liquid water density

1 kg/L (8.3 lbs./gal).

Record heat temperature

Apparent temperature of 81° C (178° F) recorded on July 8, 2003, in Dharan, Saudi Arabia.

Dew points > 21° C (70° F)

Increases discomfort.

Average deaths from heat-related situations

On average, 400 people die from this situation each year.

Deaths in Chicago and Milwaukee 1995

750 died due to heat-related issues.

Deaths in Europe 2003, 2006, and 2018

73,500 died due to heat-related issues.

Deaths in Russia 2010

56,000 died due to heat-related issues.

Phases of water

Solid, liquid, and gas.

Ice

A solid state of water with a lattice of hydrogen bonds.

Liquid water

Weaker bonds that stretch, break, and re-form.

Gas state of water

Few bonds, move freely.

Average Sea Level Pressure

1013.25 mb

Saturation Vapor Pressure

Vapor pressure at which saturation occurs

Specific Humidity

Mass of water vapor in grams per kilogram

Relative Humidity

Ratio of water vapor content to water vapor capacity expressed as percentage

100% Relative Humidity

Net condensation

Dew Point

Temperature at which the air becomes saturated

Dew-Point Depression

Difference between air temperature and the dew point

Unstable Air

Air moves higher in the atmosphere

Atmospheric Instability

Transports heat from Earth's surface

Adiabatic Temperature Change

Temperature change due to rising or sinking air

Dry Adiabatic Rate

10° C/1000 m (5.5° F/1000 ft)

Environmental Lapse Rate

6.5° C/1000 m (3.6° F/1000 ft)

Moist Adiabatic Lapse Rate

6° C/1000 m (3.3° F/1000 ft)

Atmospheric Stability

Measure of atmospheric buoyancy

Rain Shadow

Leeward side of mountains with sinking air, creating a desert

Lifting Mechanisms

Processes such as orographic, convection, frontal, and convergence that lift air

Lifting Condensation Level

Altitude where air temperature equals dew point temperature, resulting in 100% RH