China's smog problem explained

A thick haze has this week smothered Beijing and surrounding areas, with tens of millions of people in northern China under severe pollution warnings.

Examining how Mei-yu precipitation responds to climate change

Mei-yu (i.e., plume rain) is a distinct weather phenomenon in East Asia during summer, which is generally characterized by persistent rainy and cloudy weather in the middle-lower Yangtze River valley (hereinafter referred ...

How wildfires and weather affect Portugal's public health

The past few decades have passed in a smoke-filled haze as severe wildfires have blazed across forests and tundras on multiple continents, frequently turning skies orange and triggering air quality alerts. These fires often ...

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Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture, called the Absolute humidity. In everyday usage, it commonly refers to relative humidity, expressed as a percent in weather forecasts and on household humidistats; it is so called because it measures the current absolute humidity relative to the maximum. Specific humidity is a ratio of the water vapor content of the mixture to the total air content (on a mass basis). The water vapor content of the mixture can be measured either as mass per volume or as a partial pressure, depending on the usage.

In meteorology, humidity indicates the likelihood of precipitation, dew, or fog. High relative 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, used during summer weather.

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