Weather and Climate

• Weather is the condition of the atmosphere at a specific time and place.
• Weather is described by temperature, humidity, precipitation, cloudiness, visibility, and wind.
• Climate is the long-term average of weather conditions in a region.

Weather Elements and Measurement

• Temperature is measured using thermometers (mercury, digital) in Celsius (°C) or Fahrenheit (°F).
• Maximum and minimum thermometers record the highest/lowest temperatures over a period.
• Humidity refers to the amount of water vapor in the air.
• Relative Humidity (RH) is the ratio of actual to maximum possible water vapor at a given temperature.
• Humidity is measured using hygrometers (hair, electronic).
• Precipitation is any form of water falling from the atmosphere (rain, snow, sleet, hail).
• Rainfall is measured in millimeters or inches using rain gauges.
• Snowfall is measured using snow gauges (converted to water equivalent).
• Wind is the movement of air horizontally.
• Wind speed is measured using anemometers in kilometers per hour, miles per hour, or knots.
• Wind direction is measured using wind vanes, indicating from where the wind blows.
• Atmospheric Pressure is the force exerted by the weight of air above a point.
• Atmospheric pressure is measured using barometers (mercury, aneroid) in hectopascals (hPa) or millibars (mb).
• Cloud Cover is the fraction of the sky obscured by clouds.
• Cloud cover is measured visually in okta (eighths) or with automated sensors.
• Visibility is the distance at which an object can be clearly seen.
• Visibility can be measured visually or using transmissometers (in meters or miles).

Atmospheric Composition

• Dry air is composed mainly of Nitrogen (N2) at ~78%.
• Dry air is composed mainly of Oxygen (O2) at ~21%.
• Dry air is composed mainly of Argon (Ar) at ~0.9%.
• Trace gases include neon, helium, methane, krypton, hydrogen, and ozone.
• Water Vapor (H2O) varies significantly (0-4%) depending on location and conditions.
• Aerosols are tiny solid or liquid particles suspended in the air (e.g., dust, sea salt, pollutants).

Atmospheric Layers

• Troposphere is the lowest layer where weather occurs; temperature decreases with altitude.
• Stratosphere contains the ozone layer; temperature increases with altitude.
• Mesosphere's temperature decreases with altitude.
• Thermosphere's temperature increases with altitude.
• Exosphere is the outermost layer, gradually merges into space.

Weather Processes

• Solar Radiation: The primary energy source for the Earth's weather systems.
• Differential heating of the Earth's surface creates temperature gradients.
• Air Masses: Large bodies of air with relatively uniform temperature and humidity characteristics.
• Fronts: Boundaries between air masses (cold, warm, stationary, occluded).
• Low-Pressure Systems (Cyclones): Associated with rising air, cloud formation, and precipitation.
• High-Pressure Systems (Anticyclones): Associated with sinking air, clear skies, and stable conditions.

Weather Forecasting

• Surface observations include Data from weather stations, ships, and buoys.
• Upper-air observations include Data from weather balloons (radiosondes).
• Remote sensing includes Weather satellites and radar provide images and data.
• Numerical Weather Prediction (NWP): Computer models that simulate the atmosphere.
• Forecast maps: Visualization of weather elements (pressure, temperature, precipitation).

Measurement Instruments

• Thermometer measures air temperature; common types include liquid-in-glass (mercury or alcohol), digital, and bimetallic strip thermometers.
• Barometer measures atmospheric pressure; mercury barometers are traditional, while aneroid barometers are more portable.
• Hygrometer measures humidity; hair hygrometers use human hair, while electronic hygrometers use capacitive sensors.
• Anemometer measures wind speed; cup anemometers use rotating cups, while sonic anemometers use sound waves.
• Wind Vane indicates wind direction; points in the direction from which the wind is blowing.
• Rain Gauge collects and measures rainfall; standard rain gauges are manual, while tipping bucket rain gauges are automated.
• Weather Balloon (Radiosonde) carries instruments aloft to measure temperature, humidity, pressure, and wind at various altitudes.
• Weather Radar detects precipitation intensity and movement; Doppler radar can also measure wind speed.
• Weather Satellite provides images of clouds, temperature profiles, and other weather data; geostationary and polar-orbiting satellites are common.

Basics of Synoptic Weather Charts

• Isobars are lines connecting points of equal atmospheric pressure.
• Isotherms are lines connecting points of equal temperature.
• Frontal Symbols indicate the type and location of fronts (cold, warm, stationary, occluded).
• High and Low Pressure Centers are marked with "H" and "L" respectively.
• Wind Barbs indicate wind direction and speed.
• Cloud Cover Symbols show the amount and type of cloud cover.

Cloud Types

• High Clouds: Cirrus (Ci), Cirrocumulus (Cc), Cirrostratus (Cs).
• Mid-Level Clouds: Altocumulus (Ac), Altostratus (As).
• Low Clouds: Stratus (St), Stratocumulus (Sc), Nimbostratus (Ns).
• Vertical Clouds: Cumulus (Cu), Cumulonimbus (Cb).

Factors Affecting Weather

• Latitude affects the angle of incidence of solar radiation.
• Generally, temperature decreases with altitude.
• Proximity to Water moderates temperature and increases humidity.
• Ocean Currents transport heat around the globe.
• Topography/Mountains can cause orographic lift and rain shadows.

Air Pollution

• Sources: Industrial emissions, vehicle exhaust, agriculture, natural sources (e.g., volcanic eruptions, dust storms).
• Pollutants: Particulate matter (PM), ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO).
• Effects: Respiratory problems, cardiovascular diseases, environmental damage.
• Air Quality Index (AQI) measures air quality based on pollutant concentrations.

Weather Hazards

• Thunderstorms bring heavy rain, lightning, strong winds, hail, and tornadoes.
• Hurricanes (Typhoons, Cyclones) are intense tropical cyclones with strong winds and heavy rain.
• Tornadoes: Violent rotating columns of air extending from a thunderstorm to the ground.
• Floods: Overflow of water in normally dry areas.
• Droughts: Prolonged periods of abnormally low precipitation.
• Heat Waves: Prolonged periods of abnormally high temperatures.
• Blizzards: Severe snowstorms with strong winds and low visibility.
• Ice Storms: Freezing rain that coats surfaces with ice.

Explore the elements of weather, including temperature, humidity, and precipitation. Learn about the tools used to measure these elements, like thermometers and hygrometers. Understand the distinction between weather and climate to grasp atmospheric conditions.