87th AMS Annual Meeting

Monday, 15 January 2007
Blocking in the Northern and Southern Hemisphere: An update to include 2000 - 2006
Exhibit Hall C (Henry B. Gonzalez Convention Center)
Joseph V. Clark, Univ. of Missouri, Columbia, MO; and K. M. Mihalka and A. R. Lupo
Detailed climatologies of blocking events have been previously published, and these include not only an examination of the occurrence and duration of blocking, but these include the block intensity as well. The goal of the present work is to update these climatologies which have published the characteristics of blocking occurrence up to about the year 2000. This work will examine the occurrence of blocking into the early part of the 21st century, with one goal being to develop a continuous archive of blocking events. There are such archives available currently for other types of events such as hurricanes or tornadoes, but no available list of individual blocking events exist. Also, there is no climatological information that extends into the current year or month. Additionally, this work will examine some of the conclusions of earlier studies. One topic explores the well-known decrease in the occurrence of Southern Hemisphere blocking events found in the late 20th century. It is apparent that early in the 21st century, blocking events are on the increase again. Finally, these data will provide for a longer archive than previously published and as such these strengthen the conclusions of earlier studies regarding ENSO variability. A longer data set will finally allow for a meaningful investigation of the interdecadal variability of blocking as well. This study used the NCEP re-analyses in order to be consistent with the data used by earlier studies.

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