Techno rainbird

NASA develops computer model to track origins of rain

Published: Saturday 15 June 2002

a new computer model by National Aeronautical and Space Administration (NASA) can now indicate exactly where rain or snow originate across the world. The model simulates water movement in the atmosphere around the world and traces it from the places where it evaporates to the places where it falls back to the Earth.

"If I see rain or snow in the central US, I can now tell you how much of the moisture came from the Gulf of Mexico, how much came from the tropical Atlantic Ocean and so on," said meteorologist Mike Bosilovich from NASA's data assimilation office.

According to NASA scientists, their 'water vapour tracer' model can be used for improving rainfall and drought forecasts. "The model gives us a much clearer picture of how moisture moves in the atmosphere than we ever had before," said Bosilovich. The model can pinpoint individual regional sources of atmospheric moisture, instead of combining them. Due to this, accurate regional forecast can be made.

More importantly, the model can be utilised for gaining a deeper understanding of climate change. According to Bosilovich, by using the model, scientists can understand how geographic sources of atmospheric moisture fluctuate from year to year. As a result of this, they can have a clearer picture of how the climate changes in the long-term.

The researchers demonstrated the model's capabilities by analysing the atmospheric water cycles over India and North America. They chose to analyse the cycles during the summer months over a period of six years, since both the regions experience monsoons from June through August, and provide a great deal of moisture to track. They found that while precipitation in India often comes directly from the ocean, much of what falls on the US in the summertime is 'recycled' moisture -- it is the water from previous storms that evaporates from the ground and then falls again quickly nearby.

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