1 / 8

3.5 Changes in Atmospheric Circulation

3.5 Changes in Atmospheric Circulation. Pei-Yu Chueh 2010/7/1. 3.5.1 Surface or Sea Level Pressure. From 1948 to 2005 for DJF found decreases over the Arctic, Antarctic and North Pacific , an increase over the subtropical North Atlantic, southern Europe and North Africa

robyn
Télécharger la présentation

3.5 Changes in Atmospheric Circulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 3.5 Changes in Atmospheric Circulation Pei-Yu Chueh 2010/7/1

  2. 3.5.1 Surface or Sea Level Pressure • From 1948 to 2005 for DJF found decreases over the Arctic, Antarctic and North Pacific, an increase over the subtropical North Atlantic, southern Europe and North Africa • The strength of mid-latitude MSLP gradients and associated westerly circulation appears to have increased in both hemispheres, especially during DJF, since at least the late 1970s.

  3. 3.5.2 Geopotential Height, Winds and the Jet Stream • Nakamura et al. (2002) found a weakening of the North Pacific winter jet since 1987, allowing efficient vertical coupling of upper-level disturbances with the surface temperature gradients.

  4. 3.5.3 Storm Tracks • polewardshift in storm track location • increased storm intensity • decrease in total storm numbers • Significant decreases in cyclone numbers, and increases in mean cyclone radius and depth over the southern extratropicshave been associated with the observed trend in the SAM.

  5. 3.5.4 Blocking • Blocking events, associated with persistent high-latitude ridging and a displacement of mid-latitude westerly winds lasting typically a week or two, are an important component of total circulation variability on intra-seasonal time scales. • Observations show that in the Euro-Atlantic sector, long-lasting (>10 day) blockings are clearly associated with the negative NAO phase. • Wiedenmann et al. (2002) found that blocking events, especially in the North Pacific region, were significantly weaker during El Niño years.

  6. 3.5.5 The Stratosphere • The breaking of vertically propagating waves, originating from the troposphere, decelerates the stratospheric westerlies. • This sometimes triggers ‘sudden warmings’ when the westerly polar vortex breaks down with an accompanying warming of the polar stratosphere, which can quickly reverse the latitudinal temperature gradient (Kodera et al., 2000).

  7. negative NAM anomalies • On average, weak vortex conditions in the stratosphere tend to descend to the troposphere and are followed by negative NAM anomalies at the surface for more than two months.

  8. 3.5.6 Winds, Waves and Surface Fluxes • Visual VOS observations of wind waves for more than a century, often measured as significant wave height(SWH). • Significantly positive almost everywhere in the North Pacific.

More Related