Planetary frontal zone

FIGURE 5.17 Pearson correlation coefficient (R) between the WIBIX and 360° zonally averaged winter anomalies (JFM) in the air temperature derived from (WCP, 1987) for slices of five degrees between 15°N and 85°N during of the last continental climate mode (1951-1986) vertical hues mark the 95% confidence level (/-distribution) while the box indicates the averaged belt of the planetary frontal zone with imbedded westerlies note the increasing poleward correlation due to the increasing effect of the AO. 

FIGURE 5.18 Winter season (JFM) overall difference of westerly wi nds ((7) at the sea level between the actual maritime climate mode starting in 1988 and a great part of the preceding continental mode (1948-1987) as derived from (NOAA, 2006) positive values (gray coloured) indicate increasing westerlies within the belt of the planetary frontal zone (40°-60°N) during the last 18 years. 

Triggered by planetary pressure gradients, large-scale transfers of air masses occur which differ in terms of their energy or humidity content. When they collide, this creates frontal zones as the warmer, hghter (or even more humid) air rises above the colder air. This process can result in condensation and longer-lasting precipitation (Fig. 2b). 

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