A new type of weather condition has been observed that exists primarily in one part of the world: compact, slow-moving, moisture-rich pools that researchers call “atmospheric lake”.
This unique type of storm occurs over the western Indian Ocean & moves towards Africa. Unlike most storms, created by a vortex, lakes are produced by concentrations of water vapor that dense enough to produce rain.
These atmospheric lakes similar to atmospheric rivers, narrow bands of dense moisture, but the new type of meteorological phenomena are smaller, move more slowly, and are detached from weather system that creates them.
“These bodies of vapor sometimes drift west over the east coast of Africa, bringing rain to this semi-arid area,” explains a summary of the research presented at the American Geophysical Union’s of 2021 fall meeting.
“By contrast to the rain-bearing ‘atmospheric rivers’ made up of vapor that are contiguous from source to cost-line at instant, we call these dis-connected & drifting water bodies ‘atmospheric lakes’.
Brian Mapes/NOAA ERA-Interim reanalysis data set
Existing as they do in equatorial region where the wind speed is often very low or even negligible, these atmospheric lakes are in no hurry. In a five-year analysis of meteorological data, the long lasting storm has been in the air for a total of 27 days.
During the 5 years, 17 atmospheric lakes lasting-longer more than 6 days were discovered, within 10 degrees of equator. It seems that these lakes can also occur in other regions, where they sometimes turn in-to tropical cyclones.
A team is being set up to carry out an in-depth study of the phenomenon. One of the questions the researchers will address is why atmospheric lakes separate themselves from river lake patterns they form – possibly because of general patterns of atmospheric winds, or perhaps because of self-propelled winds produced inter-nally.
“The winds that carry these things ashore are so tantalizingly, delicate near zero (wind speed), that they could affect them all,” says one of researchers, atmospheric researcher Brian Mapes of the University of Miami.
“Then you need to know if they are self-propelled or if they are powered by large scale wind patterns that can change with climate change.”
The angle of climate change is important, because if rising temperatures somehow affect the formation & movement of atmospheric lakes, it could impact rainfall that reaches east coast of Africa. , where they are absolutely necessary.
According to Mapes, if all the water in a year’s atmospheric lakes were liquefied at once, it would create a puddle a few inches deep but one kilometer (0.62 mile) wide. This is a significant amount of precipitation.
The next step is to collect more data, including more localized & detailed readings. This is a part of the world where rain & water vapor tend to be studied month-to-month rather than day-to-day, according to Mapes, which is why these lakes have been lost so far.
“It’s a medium dry place, so when these [atmospheric lakes] do happen, they’re definitely very important,” Mapes explains.
“I look forward to learning more about them, in this region of venerable & fascinating nautical history where careful sailors coined the word monsoon for wind-pattern, and surely noticed these occasional rain-storms too.
