What are the effects of atmospheric rivers on global weather patterns?

Atmospheric rivers (ARs) are relatively narrow regions in the atmosphere that are responsible for the transport of large amounts of water vapor across the globe. ARs are typically several hundred kilometers wide, and a few thousand kilometers long. They are capable of transporting an amount of water vapor equivalent to 15-20 times the average flow of liquid water at the mouth of the Mississippi River.

ARs are most commonly associated with the formation of extreme weather events, such as heavy rain and snowfall, floods, and droughts. These events can cause significant damage to infrastructure and ecosystems, and can affect global weather patterns.

ARs play an important role in global climate patterns, as they are the main source of moisture for the mid-latitude storm systems that drive the majority of weather in the Northern and Southern Hemispheres. ARs also play a role in the global water cycle, as they transport large amounts of water vapor from the tropics to the mid-latitudes, where it can be deposited as rain and snow.

ARs can also influence climate patterns over short time scales, such as the El Niño-Southern Oscillation (ENSO). During El Niño events, ARs bring warm, moist air to the eastern Pacific, leading to higher than average rainfall in the region. This can lead to droughts in the western Pacific, and increased hurricane activity in the eastern Pacific.

ARs can also affect global temperatures, as they transport large amounts of heat from the tropics to the poles. This can lead to warmer temperatures in the polar regions, which can have a significant impact on global climate patterns.

In addition to their effects on global weather patterns, ARs can also affect air quality and visibility. During heavy rainfall events, high levels of pollutants can be washed out of the atmosphere, leading to improved air quality. However, during dry periods, ARs can transport large amounts of dust and pollutants, leading to reduced visibility and increased air pollution.