2010 heat wave in Russia and floods in Pakistan, associated with the same air flow anomalies

August 31, 2011 MOSCOW
— Two of the most devastating natural disasters of 2010 were closely linked by a single meteorological conditions, even if they occurred 1,500 miles (2.414 km) of each other and were completely different characters, a new NASA study shows. Study finds that the same large-scale meteorological conditions — abnormal Rossby wave — caused heat and persistent wildfires in Russia as well as unusual downstream wind patterns, precipitation has changed in the Indian monsoon region and increased severe flooding in Pakistan. The atmosphere, gaseous and transparent, may not seem like a liquid, but it is like a thin layer of air shell of the planet behaves. As the Earth rotates on its axis, huge rivers of air — scientists call them Rossby waves — meander around the world to the west. The currents in the center of these waves form the air flow, fast-moving columns of air, then weather systems from west to east. Rossby waves are not uniform. They tend to bend, and troughs and ridges. Areas of low pressure are usually developed in the trough wave, while the high-pressure areas form in their ridges. Parcels of warm air from the tropics and cool air from the Poles circling low and high pressure part of the wave, creating a complex tapestry of warm and cold fronts meet and communicate constantly. Clashes between the warm and cold fronts produce storms and precipitation. Under normal summer conditions, the water stream pushes weather fronts across Eurasia in four or five days, but something unusual happened in July 2010. Scale,
stagnant weather pattern known as Omega blocking event — developed over a high-pressure ridge over western Russia. This blocking event, into which the water flow, 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 area of high pressure that had been created in Russia and trapped in a hot, dry air mass. How high lingered, the land surface, dried and 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 locking scheme has created unusual downstream wind patterns in Pakistan. Zone of low pressure to the edge of the Rossby wave formed in response to high, pulled cold, dry Siberian air into lower latitudes. This cold air from Siberia collided with warm, moist air coming over Pakistan from the Bay of Bengal. Nothing strange moisture moving north over India in the Himalayas. This is a normal part of the monsoon. However, in this case, the unusual nature of the winds associated with the blocking high brought upper level air traffic further south than usual, which helped shift the entire monsoon system north and west. Shift brought heavy monsoon rains just above the northern part of Pakistan. —Space Daily

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