Atmospheric rivers are extensive channels of moisture that can deliver significant precipitation, including rain and snow, across various regions.
Origins of Atmospheric Rivers
Typically, atmospheric rivers develop in tropical areas. Here, warm temperatures enable water vapor to ascend into the atmosphere. Once airborne, winds transport this moisture to different latitudes worldwide.
Impact on Precipitation
- Atmospheric rivers are critical for the West Coast of the United States.
- They contribute 30% to 50% of the region’s annual precipitation.
- While beneficial for water supplies, they also pose risks, including flooding and mudslides.
Characteristics of Atmospheric Rivers
These phenomena are formed by winds associated with cyclones. In size, they typically range from 250 to 375 miles (400 to 600 kilometers) wide. While many events are relatively weak, the more intense atmospheric rivers can transport immense quantities of moisture.
Moisture Capacity
Research from the U.S. Geological Survey indicates that these powerful systems can carry between seven and 15 times the average daily water flow of the Mississippi River. Furthermore, studies suggest that atmospheric rivers are increasing in size and frequency due to global warming.
Effects on Landfall
When atmospheric rivers encounter land, particularly mountainous regions like the Sierra Nevada, the moisture-laden air rises and cools. This process often results in heavy precipitation as rain or snow.
Seasonal Implications
Unlike traditional cold winter storms, which originate from the North Pacific, atmospheric rivers are generally warmer. While snowfall may still occur at higher altitudes, substantial rain often falls on lower elevations, leading to rapid snowpack melting and potential flooding.
The Pineapple Express
A specific type of atmospheric river known as the “Pineapple Express” originates near Hawaii in the tropical Pacific. This term highlights its strength and impact on weather patterns.
Historical Context
The term “atmospheric river” was coined in the 1990s through the research of scientists Yong Zhu and Reginald E. Newell from the Massachusetts Institute of Technology. Atmospheric rivers are commonly abbreviated as ARs.
Understanding atmospheric rivers is crucial for managing water resources and preparing for extreme weather events in affected areas.
