Whois & Analysis for weather-atlas.com

The ultraviolet index or UV Index is an international standard measurement of the strength of sunburn-producing ultraviolet (UV) radiation at a particular place and time.

The scale was developed by Canadian scientists in 1992, then adopted and standardized by the UN's World Health Organization and World Meteorological Organization in 1994.

It is primarily used in daily forecasts aimed at the general public, and is increasingly available as an hourly forecast as well.

Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location.

Human beings have attempted to predict the weather informally for millennia, and formally since the nineteenth century.

Weather forecasts are made by collecting quantitative data about the current state of the atmosphere at a given place and using scientific understanding of atmospheric processes to project how the atmosphere will change.

Humidity is the amount of water vapor present in the air.

Water vapor is the gaseous state of water and is invisible.

Humidity indicates the likelihood of precipitation, dew, or fog.

Higher humidity reduces the effectiveness of sweating in cooling the body by reducing the rate of evaporation of moisture from the skin.

This effect is calculated in a heat index table or humidex.

The amount of water vapor that is needed to achieve saturation increases as the temperature increases.

As the temperature of a parcel of water becomes lower it will eventually not reach the point of saturation without adding or losing water mass.

The differences in the amount of water vapor in a parcel of air can be quite large.

For example, a parcel of air that is near saturation may contain 28 grams of water per cubic meter of air at 30 °C, but only 8 grams of water per cubic meter of air at 8 °C.

Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light.

On Earth, sunlight is filtered through Earth's atmosphere, and is obvious as daylight when the Sun is above the horizon.

When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat.

When it is blocked by clouds or reflects off other objects, it is experienced as diffused light.

The World Meteorological Organization uses the term "sunshine duration" to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter.

Other sources indicate an "Average over the entire earth" of "164 Watts per square meter over a 24 hour day".

Snow pertains to frozen crystalline water throughout its life cycle, starting when it precipitates from clouds and accumulates on surfaces, then metamorphoses in place, and ultimately melts, slides or sublimates away.

Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air.

Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals.

Snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime.

As snow accumulates into a snowpack, it may blow into drifts.

Over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw.

Where the climate is cold enough for year-to-year accumulation, a glacier may form.

Otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater.