Abstract
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.