Australia: The Land Where Time Began

A biography of the Australian continent 

Trends in the Global Jet Stream Characteristics Observed in the Latter Half of the 20^th Century

It is proposed in this paper that a new method, that is based on the detection of jet cores, aims  at a description of climatological features of the jet streams, as well as to estimate their latitudinal, altitudinal and velocity in the 20^th century reanalysis data of the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR). According to Pena-Ortiz et al., the use of s single grid point to define the position of jet cores in their method allows their results to reveal a more accurate picture of the split flow configurations and double jet structures. They believe the first multiseasonal and global trend analysis of jet streams, based on a daily-resolution 3-D algorithm, is provided by their method. Over the periods 1958-2000, and during the period when satellite technology was available, 1979-2008, the trends have been analysed. The results obtained by Pena-Ortiz et al. found that, in general, jet velocity trends and latitudes have been faster for the Southern Hemisphere jets, especially in the southern polar front jet, which has the fastest velocity increase, as well as shift poleward, over 1979-2000 during the austral summer and autumn. An acceleration and a poleward shift  of the northern and southern subtropical jets over 1979-2008 are shown by the results presented in this paper to occur at a faster rate and over larger zonally extended regions during the latter period than during the 1958-2008 period.

Sources & Further reading

1. Pena-Ortiz, C., D. Gallego, P. Ribera, P. Ordonez and M. D. C. Alvarez-Castro (2013). "Observed trends in the global jet stream characteristics during the second half of the 20th century." Journal of Geophysical Research: Atmospheres: n/a-n/a.