Fires and floods were spawned by the same atmospheric event in 2010.
Last year, massive wildfires toasted the taiga in Russia while floods swept away lives and livelihoods in Pakistan. Though separated by 1,500 miles (2,414 km) and of opposite natures, the two disasters were linked by an abnormal change in the currents of atmosphere, called Rossby waves.
NASA researchers used satellite imagery of the air currents over Asia to identify a blockage, known as an Omega blocking event, that slowed the Rossby waves and split the jet stream over Russia. The blockage developed over a high pressure system above Russia.
It was as if a large rock (the Omega blockage) had fallen into a creek (the Rossby wave) and caused the current to split in two.
Normally hot, dry, high pressure systems pass over the area in a few days, but in this case the split jet stream could no longer push the hot, dry air out. For weeks, heat built up over Western Russia and the forests dried out. Eventually, fires broke out and consumed the dry trees.
At the same time, further west and downstream in the Rossby wave, a low pressure system formed in response to the high pressure system above Russia.
“From NASA satellite data and wind analysis, we can clearly see the connection between the two events,” said William Lau, an atmospheric scientist at NASA’s Goddard Space Flight Center in a press release.
“Think of the atmosphere like a loose membrane. If you push one part up, something else has to come down somewhere else. If you produce a high in one region, you produce a corresponding low in another,” Lau said.
The low pressure system sucked cold, dry Siberian air into lower latitudes. This cold Siberian air smashed into warm, moist air flowing north from the Bay of Bengal. The collision occurred above Pakistan and caused monsoon rains to drop before they normally do.
In a normal monsoon year, the rains pass north over India from the sea, and drop in heavy torrents over Northwest India and parts of Pakistan as the warm moist air hits cool air from the Himalayas. Northern Pakistan wasn’t prepared to receive the brunt of the deluge caused by the abnormal atmospheric event over Russia.
Though the NASA satellites were able to reveal what happened and the connections between the two disasters, researchers still don’t know why the blockage occurred in the first place. The study also raises questions about how earth, wind and fire may have interacted to make the phenomenon worse.
The Russian drought itself may have reduced rainfall since there was no water evaporating from the soil to form clouds. When the fires broke out, Lau suggests that dark particulates in the the smoke, called black carbon, may have worked to further shrivel cloud cover and increase the intensity of the drought.
The NASA study was recently published in the journal Hydrometeorology, and was authored by Lau and Kyu-Myong Kim, another NASA scientist.
IMAGE 1: Russian wildfires in August 2010. (Wikimedia Commons)
IMAGE 2: This map shows temperature anomalies from July 20—27, 2010, compared to temperatures for the same dates from 2000 to 2008. The anomalies are based on land surface temperatures observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Areas with above-average temperatures appear in red and orange, and areas with below-average temperatures appear in shades of blue. Oceans and lakes appear in gray. (NASA/Earth Observatory)
IMAGE 3: Flood waters have washed away all ground means to reach the people stranded in the northern areas of the Swat valley in Pakistan, Aug. 11, 2010. (Wikimedia Commons)