Russia — A single meteorological event might have led to two of the most destructive natural disasters of 2010 that occurred 1,500 miles apart – the extreme Russian fires and the heavy Pakistan floods – a new NASA study has suggested.
The research found that the same large-scale meteorological event – an abnormal Rossby wave – sparked extreme heat and persistent wildfires in Russia as well as unusual downstream wind patterns that shifted rainfall in the Indian monsoon region and fuelled heavy flooding in Pakistan.
As Earth spins on its axis, huge rivers of air, scientists call them Rossby waves, meander around the globe in a westerly direction.
Currents in the centre of these waves form the jet streams, fast-moving columns of air that push weather systems from west to east.
Under normal summertime conditions, the jet stream pushes weather fronts through Eurasia in four or five days, but something unusual happened in July of 2010.
A large-scale, stagnant weather pattern – known as an Omega blocking event – developed over a high-pressure ridge above western Russia.
This blocking event, which divided the jet stream, had the effect of slowing the Rossby wave and prevented the normal progression of weather systems from west to east.
As a result, a large region of high pressure formed over Russia and trapped a hot, dry air mass.
As the high lingered, the land surface dried and the normal transfer of moisture from the soil to the atmosphere slowed. Precipitation ceased, vegetation dried out, and the region became a taiga tinderbox.
Meanwhile, the blocking pattern created unusual downstream wind patterns over Pakistan. Areas of low pressure on the leading edge of the Rossby wave formed in response to the high that pulled cold dry Siberian air into lower latitudes.
“From NASA satellite data and wind analysis, we can clearly see the connection between the two events,” said William Lau, who authored the study with Kyu-Myong Kim, both atmospheric scientists at NASA’s Goddard Space Flight Centre in Greenbelt, Md.
The study was published in August in the Journal of Hydrometeorology. (ANI)