+ SNOW

Snow forms when water vapour in the atmosphere freezes into ice crystals. Snowflakes form in a variety of different shapes. Snow is a form of precipitation; other forms of precipitation are rain, hail and sleet. Light and fluffy snow is often called ‘powder’. Heavy snowfalls are often called ‘snowstorms’. Snowstorms with high winds are often called ‘blizzards’.

+ HAIL

Imagine a cold glass of water filled with lots of ice cubes. Now imagine those ice cubes falling from the sky like rain. That is exactly how hail drops from the sky. Just like rain, snow, and sleet, hail is a kind of precipitation. In other words, any kind of water that comes down from the clouds in different forms is called precipitation.

+ WIND

Wind is air in motion. It is produced by the uneven heating of the earth's surface by the sun. Since the earth's surface is made of various land and water formations, it absorbs the sun's radiation unevenly. Two factors are necessary to specify wind: speed and direction.

+ THE SUN AND SUNSHINE

The Sun is a star found at the center of the Solar System. It makes up around 99.86% of the Solar System's mass. At around 1,392,000 kilometres (865,000 miles) wide, the Sun's diameter is about 110 times wider than Earth's. Around 74% of the Sun's mass is made up of hydrogen. The Sun’s core is around 13600000 degrees Celsius! The sun also plays a big factor on are temperatures on earth as well as weather.

+ TEMPERATURE

Temperature refers to how warm or cold air is, and the density of the air is how many molecules are packed into a certain space of air. ... But, air pressure also affects temperature - the more those molecules bump into each other, the more heat they generate. So, more collision means warmer air.

+ FROST

Frost is the coating or deposit of ice that may form in humid air in cold conditions, usually overnight. In temperate climates, it most commonly appears as fragile white crystals or frozen dew drops near the ground, but in cold climates, it occurs in a greater variety of forms. Frost is composed of delicate, branched patterns of ice crystals that formed as the result of fractal process development.

The formation of frost is an indication that the air temperature has fallen below the freezing point of water, and plants that have evolved in warmer climates are known to suffer damage when the temperature falls low enough to freeze the water in the cells that make up the plant tissue. The tissue damage resulting from this process is known as "frost damage". Farmers in those regions where frost damage is known to affect their crops often invest in substantial means to protect their crops from such damage.

TYPES OF FROST There are different types of frost. The most common are radiation frost (also called hoarfrost), advection frost, window frost, and rime. Radiation frost is frost in the form of tiny ice crystals that usually shows up on the ground or exposed objects outside. Hoarfrost also forms in refrigerators and freezers.

+ ICE

Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white colour.

In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far away as the Oort cloud objects. Beyond the Solar System, it occurs as interstellar ice. It is abundant on Earth's surface – particularly in the polar regions and above the snow line – and, as a common form of precipitation and deposition, plays a key role in Earth's water cycle and climate. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes.

The most common phase transition to ice occurs when liquid water is cooled below 0°C at standard atmospheric pressure. It may also be deposited directly by water vapour, as happens in the formation of frost. The transition from ice to water is melting and from ice directly to water vapour is sublimation.

Ice is used in a variety of ways, including cooling, winter sports and ice sculpture.

+ FOG

Fog consists of visible cloud water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog has affected many human activities, such as shipping, travel, and warfare. Fog forms when the difference between air temperature and dew point is less than 2.5 °C (4.5 °F). Fog begins to form when water vapor condenses into tiny liquid water droplets suspended in the air. Six examples of ways that water vapour is added to the air are

• By wind convergence into areas of upward motion.
• Precipitation or virga falling from above
• Daytime heating evaporating water from the surface of oceans, water bodies, or wet land.
• Transpiration from plants
• Cool or dry air moving over warmer water and lifting air over mountains. Water vapour normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. Freezing Fog The formation of freezing fog is made in the same way as ordinary fog. This process takes place when the land cools down overnight with clear skies overhead.

The heat from the land diffuses back into the air, which leads to cooling at the earth’s surface. This reduces the air’s ability to hold moisture, which in turn allows water vapour to condense into tiny water droplets – it is this process of condensation that leads to the fog being formed. If fog is formed in temperatures that are below freezing, these tiny water droplets in the air remain as liquid.

They then become supercooled water droplets, which stay in this state despite being at a temperature below freezing. The Met Office says this occurs because the liquid needs a surface to freeze upon. Furthermore, when droplets from freezing fog freeze onto surfaces, they form a white deposit of feathery ice crystals known as rime. Interestingly, rime is a characteristic of freezing fog, and is often seen on vertical surfaces that have been exposed to the wind.

+ MIST

Mist is a phenomenon caused by small droplets of water suspended in air. Physically, it is an example of dispersion. It is most commonly seen where warm, moist air meets sudden cooling, such as in exhaled air in the winter, or when throwing water onto the hot stove of a sauna. It can be created artificially with aerosol canisters if the humidity and temperature conditions are right. It can also occur as part of natural weather, when humid air cools rapidly, for example when the air comes into contact with surfaces that are much cooler than the air. The only difference between mist and fog is visibility. The phenomenon is called fog if the visibility is one kilometre (1,100 yards) or less. In Ireland the definition of fog is visibility less than 100 metres, while for pilots the distance is one kilometre. Otherwise it is known as mist. Freezing Mist Freezing mist is similar to freezing fog, only the density is less and the visibility greater. (When fog falls below 0 degrees Celsius in temperature it is known as freezing fog.)