Key Points

Weather is the state of the Earth's atmosphere at a specific time and place. It includes conditions like being hot, cold, rainy, or windy.

The troposphere is the lowest layer of the Earth's atmosphere, extending 6 to 18 kilometers high. Almost all weather phenomena occur in this layer.

The five main elements that define weather are temperature, precipitation, atmospheric pressure, wind, and humidity.

Temperature measures how hot or cold the atmosphere is. It is measured with a thermometer in degrees Celsius ($^{\circ} \text{C}$) or Fahrenheit ($^{\circ} \text{F}$).

The range of temperature is calculated as $T_{\text{max}} - T_{\text{min}}$. The mean daily temperature is calculated as $\frac{T_{\text{max}} + T_{\text{min}}}{2}$.

Precipitation is any form of water, like rain, snow, or hail, that falls from the atmosphere. It is measured using a rain gauge in millimeters (mm).

Atmospheric pressure is the weight of the air on the Earth's surface. It is measured with a barometer, and the unit is millibars (mb).

Wind is the movement of air from an area of high atmospheric pressure to an area of low pressure. Its speed and direction are important characteristics.

A wind vane is used to determine the direction of the wind. An anemometer measures the speed of the wind, usually in kilometers per hour (km/h).

Humidity is the amount of water vapor present in the air. It is measured with an instrument called a hygrometer.

Humidity is expressed as relative humidity, a percentage from $0\%$ (no water vapor) to $100\%$ (air saturated with water vapor).

Early methods of forecasting weather involved observing nature, such as the behavior of ants and frogs or the opening and closing of pine cones.

Meteorology is the scientific study of weather and its evolution. Meteorologists use data from instruments to create accurate weather forecasts.

A weather station is a facility with instruments to measure and record weather conditions. Automated Weather Stations (AWS) collect data automatically.

Weather predictions are crucial for preparing for extreme events like cyclones and floods. They help sectors like farming, aviation, and disaster management.

The IMD, established in 1875, is the primary agency in India responsible for meteorological observations and weather forecasting.