Apr 5, 2012
Bidimensional Diagnostics, Variability, and Trends of Northern Hemisphere Blocking
by
,
American Meteorological Society
- Analyzes Northern Hemisphere winter blocking through the introduction of a set of new bidimensional diagnostics based on geopotential height that provide information about the occurrence, the duration, the intensity, and the wave breaking associated with the blocking
- Performs analysis with different reanalysis datasets in order to evaluate the sensitivity of the index and the diagnostics adopted
- Defines a new category of blocking placed at low latitudes that is similar to midlatitude blocking in terms of the introduced diagnostics but is unable to divert or block the flow
- Finds that over the Euro-Atlantic sector it is possible to phenomenologically distinguish between high-latitude blocking occurring over Greenland, north of the jet stream and dominated by cyclonic wave breaking, and the traditional midlatitude blocking localized over Europe and driven by anticyclonic wave breaking
- Finds these latter events are uniformly present in a band ranging from the Azores up to Scandinavia
- Finds a similar distinction cannot be pointed out over the Pacific basin where the blocking activity is dominated by high-latitude blocking occurring over eastern Siberia
- Analyzes the variability and the trend, considering the large impact that blocking may have on the Northern Hemisphere
- Results show a significant increase of Atlantic low-latitude blocking frequency and an eastward displacement of the strongest blocking events over both the Atlantic and Pacific Oceans