Types of Weather-Be Updated On This Issue

The sun drives different types of weather by heating land and water at varying rates, creating air masses. Cool air masses push warm ones out of the way, resulting in up and down movement of atmospheric pressure and humidity.

A few simple observations can help you notice changes in the weather. Watch for changing cloud patterns; cumulus towers may indicate rain, while nimbostratus clouds mean a dry front is coming in.

Temperature

Probably the most common measurement of weather, temperature is how warm or cold it feels. Temperature is a physical property of matter – the average kinetic energy of its molecules – and is closely related to heat. Heat is the energy that transfers between objects of different temperatures.

Atmospheric and ocean circulation redistribute heat around the globe, shaping regional temperature patterns. Temperature also depends on a region’s latitude and continental position. The average values of temperature and the extremes (which generally have the largest impacts on natural systems and human infrastructure) vary from one area to another.

The temperature scales most commonly used worldwide are Celsius and Fahrenheit. Other temperature scales include Kelvin, Rankine and Réchauffement de la planète (radiational). Most temperature conversions are done by multiplying or dividing a number with its unit by the conversion factor to get a new number with a different unit. There is no true conversion between all of these scales since each assigns a different value to zero, but they are all comparable when converted using this method.

Humidity

Humidity is the concentration of water vapor in the air. This vapor is invisible and is only seen when it condenses to precipitation, fog or dew. Humidity is affected by temperature, as the amount of vapor in the air increases with warmer temperatures. The amount of moisture in the air is also affected by pressure, which changes the way that air moves and affects evaporation. Humidity is measured using a device called a hygrometer.

The humidity is highest in areas close to the equator and coastal regions. For example, Darwin and the cities of Houston, Miami and Osaka all experience very high humid periods during their summers.

Relative humidity is a function of both temperature and moisture content (or density). Humidity is higher when the air is hotter, because the molecules in the air move faster at higher temperatures. Relative humidity also depends on how much water vapor is already in the air, which can be determined by looking at the amount of water in the plants and soil near you.

Climate change and urbanization are projected to cause dangerously high levels of urban humid heat in five ‘hotspot’ regions by the 2090s — Central America/Caribbean, Western Africa, Middle East, Southern Asia and Southeast Asia (figure 1). This is due to an intersection of increased climate hazard and population growth, but the impact of climate change is larger than that from urbanization.

Wind

Wind is a result of differences in air pressure. As the sun heats Earth’s surface, warm air rises and moves away from the equator toward the poles, where cooler, denser air moves in to replace it. The force that causes this movement is known as the pressure gradient. The more difference in pressure, the stronger the wind.

Winds can also move objects over long distances. This includes dust, sand, and other particles from desert regions that spread to coastal areas or across the ocean. Wind also helps drive ocean surface currents, such as the Gulf Stream that brings warm water from the Gulf of Mexico up to Northern Europe.

The direction and intensity of wind depends on many factors, including temperature and moisture levels. Wind can transport warm or cold air masses, change temperatures, influence precipitation, and facilitate the spread of pollutants.

Prevailing winds are influenced by the Coriolis effect, an offshoot of Earth’s rotation. Winds moving near the equator tend to blow east-west rather than north-south. As they reach higher latitudes, however, the effect bends them so that they blow toward the Poles. These winds are called polar easterlies. The prevailing westerlies in the United States originate in the tropics and then curve, moving westward as they move up into mid-latitudes.

Rain

Rain is the water that falls from clouds in the sky. It is part of the water cycle and it helps to provide freshwater for plants, animals and humans. It is also a source of energy for hydroelectric power and it allows for crop irrigation. The rain also provides nutrients to soil and is important for the health of forests.

Some places get a lot of rain while others do not. Heavy rain can cause floods and landslides. Rain may also create a greenhouse effect that warms the environment and causes drought.

Air turbulence and convection carry the day’s water vapor from the oceans and lakes to the skies. As the atmosphere cools, the water vapors condense into liquid water droplets that form the rain clouds. These droplets build up until they are too heavy for gravity to keep them floating in the sky and they fall to Earth. Rain is also called precipitation and it includes any kind of water that falls from the sky, such as hail and sleet.

The chance of rain is increased by the presence of organic and inorganic particles that can serve as cloud condensation nuclei (CCN). Normally, these are dust particles from the landscape, but they can also be chemicals from automobile exhaust and industrial pollution.