HYDROLOGY 2

LESSON 2 - WEATHER AND CLIMATE

Weather

This refers to short-term conditions like rainfall, storms, temperature, and humidity. These daily changes affect how fast water evaporates or how quickly streams rise after rain. It is not permanent and may vary from minute-to-minute due to temperature, humidity, wind speed & direction

Climate

This refers to the long-term pattern of weather in an area. It helps determine how much water a place usually receives each year and what seasons are wetter or drier. This can be changed in hundreds, thousands or millions of years

Altitude

-            The higher you go above sea level, the colder it gets.

-            Temperature drops by about 6.5°C for every 1,000 meters increase in elevation.

-            This is why mountain tops are cold even in tropical countries.

Latitude

-            It refers to how far a place is from the equator.

-            Areas near the equator receive more direct sunlight, so they are warmer.

-            Areas near the poles receive less sunlight, so they are colder.

Distance from Large Bodies of Water

-            Water heats and cools more slowly than land.

-            Places near oceans or seas have milder temperatures (not too hot or too cold).

-            Inland areas far from water experience more extreme temperatures.

Ocean Currents

-            Warm and cold currents in the ocean affect nearby land.

-            Warm currents make coastal areas warmer.

-            Cold currents make coastal areas cooler.

Topography & Landform

-            Mountains can block air masses.

-            The side facing the wind (windward side) gets more rain.

-         The opposite side (leeward side) gets less rain, often forming deserts—this is called the rain shadow effect.

Prevailing Wind

-            Winds move warm or cold air from one region to another.

-            Winds coming from oceans bring moist air (more rain).

-            Winds coming from land bring dry air

Seasons and Earth’s Tilt

-            The Earth is tilted at 23.5°, causing seasonal changes in sunlight.

-            Different parts of the Earth receive sunlight at different angles depending on the time of year.

-            This produces summer, winter, spring, and fall.

Human Activities

-            Burning increases fuels fossil greenhouse gases, which warm the atmosphere.

-            Deforestation reduces the Earth's ability to absorb CO₂.

-            Urbanization increases temperatures in cities (urban heat islands).

Water Vapor

The most abundant greenhouse gas in the atmosphere

Carbon Dioxide

A greenhouse gas that is from burning of fossil fuels

Methane

A greenhouse gas that produces from decaying plant or animal matter

Chlorofluorocarbons

A greenhouse gas that is used as refrigerant in refrigerator and air conditioning units.

Nitrous Oxide

Also called as laughing gas, a greenhouse gas that has been used in surgical and dental procedures for years because of its anesthetic and analgesic properties

Campbell-Stokes Sunshine Recorder

A meteorological instrument that consists of a spherical glass to focus sunlight onto a specially marked, photosensitive card, creating a burn trace that measures the duration of bright sunshine, working like a fixed-point sundial by recording the sun’s path through burns on the card.

Radiometer

A device used for measuring radiant flux of electromagnetic radiation.

Stevenson Screen

A shelter for thermometer, hydrometer and other instruments used in measuring temperature and humidity.

Maximum and Minimum Thermometer

It consists of two horizontally placed thermometers. One records the minimum temperature of the day and the other records the maximum temperature of the day.

Barometer

It is used to measure atmospheric pressure, instantaneously.

Barograph

It is used recording minute fluctuation of atmospheric pressure

Aerovane

This indicates both the wind direction and wind speed or simply the wind velocity. It is shaped like an airplane. The nose of the plane points to the direction from which the wind blows and the rotation of the propeller measures the wind speed.

Anemometer

This is used for the measurement of wind speed. Either three or four metal hemispheres are mounted on arms which rotate freely about a vertical axis.

Rain Gauge

A device used for measuring the amount of rainfall. It is 8 inches in diameter. The rainfall collected is being measured with the use of a dipstick with a measurement on it.

Tipping Bucket Recorder

Rainfall entering the funnel collector is directed to the tipping bucket assembly. When the incremental amount of precipitation has been collected, the buckets assembly tips and activates a magnetic reed switch. The sample is discharged through the base of the gauge.

Evaporating Pan

It is a device which measures the amount of water evaporated in certain time from a surface. It consists of a round reservoir with a diameter of 47.5 inches and depth of ten inches. The tank is filled with water up to two and half inches from the top. The decrease by noting the level of water with the help of a vernier scale.