Algorithm developed to measure wind uses water vapour movement data

New Delhi, Apr 15 (PTI) Atmospheric scientists have developed a new way of measuring wind by creating an algorithm that uses water vapour movement data, that could help predict extreme events such as hurricanes and storms.

The researchers from University of Arizona, US, got the water vapour data from the two operational satellites of the National Oceanic and Atmospheric Administration, or NOAA, which recorded the data through infrared radiation.

NOAA is the US federal agency for weather forecasting.

Wind influences cloud formation by bring water vapour together, thereby, providing clues for forecasting weather patterns.

The study, published in the journal Geophysical Research Letters, provides data on the vertical distribution of horizontal winds over the tropics and mid-latitudes.

Wind brings everything else in the atmosphere together, including clouds, aerosols, water vapour, precipitation and radiation, said Xubin Zeng, co-author of the study and the director of the Climate Dynamics and Hydrometeorology Collaborative at University of Arizona.

"We never knew the wind very well. I mean, that's the last frontier. That's why I'm excited," Zeng said.

Employing more advanced algorithms, the researchers were able to estimate horizontal winds not just at one altitude, but at multiple altitudes at the same location, which Zeng said had not been possible a decade ago.

Nowadays, Zeng said, to study topics like air quality and volcano ash dispersion, which are directly influenced by wind, experts use weather forecasting models to ingest measurements from different sources rather than using direct measurements of wind.

But model outputs are not good enough when there is rainfall, Zeng said.

Lead author Amir Ouyed, a member of Zeng's research group, used machine-learning algorithms that do better image processing to track water vapour than human eyes can, they said.

"For decades, people were saying, 'You have to move the cloud top or water vapours enough so that you can see the difference of the pattern.' But now, we don't need to do that," Zeng said.

"The resolution of the data is coarse, with a pixel size of 100 kilometers. It's a demonstration of the feasibility for our future satellite mission we are pursuing where we hope to provide the 10-kilometer resolution," Zeng said.

Conventional methods of measuring winds included using radiosonde, an instrumental package suspended below a 6-foot-wide balloon, or studying cloud top, which is the height at which the upper visible part of the cloud is located.

While radiosondes proved to be expensive, the downside to studying cloud top was that wind information is not usually available between 2 and 4 1/2 miles above Earth's surface, because cloud tops exist most of the time below 2 miles or above 4 1/2 miles depending on whether the clouds are low or high.

Light detection and ranging, or lidar, provides good data but is limited in that its measurements can be acquired only in one vertical "curtain," with measured wind typically in the east-west direction, the researchers said.

Zeng and his collaborators at other institutions are planning to pursue a new satellite wind mission in which they envision combining water vapour movement data and measurements from wind lidar to provide better wind measurements overall. PTI KRS KRS KRS