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Increasingly frequent poleward excursions by the Himalayan subtropical jet
  • Uday Thapa,
  • Scott St. George,
  • Valerie Trouet
Uday Thapa
University of Minnesota

Corresponding Author:thapa037@umn.edu

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Scott St. George
University of Minnesota
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Valerie Trouet
University of Arizona
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Since the 1980s, the subtropical jet stream has generally moved poleward, but its behavior varies strongly by region and season. Here we examine the interannual variability and trends in the latitudinal position of the spring subtropical jet over the Himalayas. During the modern period (1948 to 2018), the jet is typically anchored immediately south of the Himalayas, but in four springs (1956, 1971, 1984 and 1999), it moved poleward to pass over Kyrgyzstan and north-west China. A tree-ring-based reconstruction of the interannual variability in spring Himalayan jet latitude indicates that, relative to the past four centuries, such poleward excursions have been more common in the latter half of the 20 century. These new insights into the behavior of the Himalayan subtropical jet can improve spring weather forecasts for the region and provide a real-world target for climate simulations to test whether recent excursions can be attributed to anthropogenic warming.