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SPATIAL BORA VARIATIONS IN RELATION TO COLD AIR OUTBREAK AND SURFACE PRESSURE GRADIENT
Alica Bajić
; Hydrometeorological Institute of Croatia,Zagreb
Sažetak
Bora wind on the northern Adriatic is associated with an upstream cold air outbreak although the most pronounced outbreaks are not always connecled with the strongest bora slorms.
During the cold season between 1973 - 1982 in Zagreb only 3 strong cold air outbreaks were associated with severe bora in the northern Adriatic. ln these cases bora onset is almost simultaneous along the entire northern Adriatic coast, it lasts 1 - 2 days and its strength is nearly equal at all considered meteorological stations.
The cut-off processes and blocking circulation pattern connected with the less pronounced long lasting cold air outbreak resulted with the longest bora duration.
ln 12 considered severe bora situations a drop of temperature due to cold air outbreaks is followed by the characteristic mesoscale pressure field with low pressure area along the coast and islands and higher pressure in the upstream bora region.
The estimated correlation coefficient between the cross mountain sea level pressure difference Δp and mean hourly bora velocity Vs show the stohastic significancy in all 12 severe bora cases. The relationship between Δp and Vs is stronger using Senj data than data measured at Omišalj and Pula what is a consequence of Senj's specific location in relation to the mountain barrier. ln 3 most pronounced cold air outbreak situations the constants in the correlation expression obtained using Senj data are almost the same. Thay enable us to estimate the mean hourly bora wind speed in Senj for predicted Zagreb - Senj pressure differences in similar weather situations.
Ključne riječi
severe bora wind; the northern Adriatic; surface pressure difference
Hrčak ID:
69041
URI
Datum izdavanja:
10.12.1990.
Posjeta: 724 *