Tuesday, February 27

They identify a new type of storm, slow and with a high concentration of water vapor: this is what “atmospheric lakes” are like.

The catalog of meteorological phenomena adds a new actor. During the Advancing Earth and Space Science Fall Meeting (AGU), Brian Mapes, from the University of Miami, presented a type of storm that his colleagues had not identified to date and that he has dubbed “Atmospheric lake”. It resembles atmospheric rivers (AR), narrow bands of humidity that carry water vapor – well known to meteorologists -; but they are smaller, their movement is also slower and they end up separating from the system that generates them.

Unlike most storms, formed by a vortex, the new phenomenon recorded by Mapes is characterized by the water vapor concentration, which generates the rain. In fact, it begins as streams of steam that flow from the western side of the South Asian monsoon and float through the oceanic and coastal regions at the equator with little wind. The AGU itself refers to them as “compact pools of moisture” originating in the Indo-Pacific. Like the humid and rainy air currents of the RA –precise scientific society-, atmospheric lakes originate as filaments of water vapor in the West Indian Ocean.

They occur several times a year

“These bodies of steam sometimes drift towards West Africa, bringing rain to that semi-arid area. In contrast to atmospheric rivers of steam that contain rain, which are contiguous from source to shore, we call these disconnected and drifting bodies of water ‘atmospheric lakes’ ”, detail those responsible for the study in his presentation to the AGU.

For the conclusions reached by Mapes, throughout the same year several episodes of atmospheric lakes can be recorded, which in turn go on for days. If all the water vapor they contain were liquefied, a puddle a couple of centimeters thick and about a thousand kilometers wide could form, an especially interesting source of water for the dry lowlands of East African countries. “It is a place that is dry on average, so when these atmospheric lakes occur, they are surely very important”, recognize.

Atmospheric lakes begin as filaments of water vapor in the Indo-Pacific and eventually separate from other systems. Credit: Brian Mapes / NOAA ERA-Interim Reanalysis Data Set.

For his research, the University of Miami professor analyzed the satellite data collected over five years. Thanks to them, it detected 17 atmospheric lakes that lasted more than six days and were located within ten degrees of the equator. The AGU specifies in any case that lakes more distant from the equator can also be found and that, on occasions, they end up becoming tropical cyclones. Now Mapes delves into its studies to better understand how they behave and to what extent they could be affected by climate change.

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The researchers explain that although the climatology of the semi-arid lands of the east coast of Africa is well studied on a monthly scale —with the two wet seasons that they present—, the new type of storm they have just identified, characterized by steam, “may have been overlooked ”. “Traditional meteorology tends to focus more on the characteristics of wind fields and disturbances as long-lived meteorological entities”, Reflects Maps.

Cover image | javier ruiz77 (Flickr)