Influence of the North Atlantic Oscillation on spatial distribution of moisture characteristics
Valery N. Khokhlov, Odessa State Environmental University, Odessa, Ukraine
Using GDAAC dataset the spatial structure of total precipitation (TP), surface evapora-tion (SE), total cloud fraction (CF) and precipitable water (PW) is considered in context of negative and positive phases of the North Atlantic Oscillation (NAO) during winters of 1980-1993. Analyzed geographical area is bounded with 20 N - 80 N latitudinally and 80 W - 40 E longitudinally. Considered period is characterized by winter positive phases of the NAO. During this 14-year interval, a substantial negative phase of the pattern appeared only twice, in winters of 1984-85 and 1986-87. The seasonal NAO indexes were obtained from http://www.cgd.ucar.edu/~jhurrell/nao.html.
According to a location of north-south dipole the North Atlantic have been divided into two approximately equal parts. An analysis has shown that the sharp changes of above char-acteristics (except for the PW) in a northern part were observed during winters of 1987-1990 when they have decreased at first and then have enlarged. At the same time in a southern part the changes were smother. Let's note that strongest (for above period) positive phase of the NAO (index was equaled 3.4) was registered in the winter of 1988-89.
Spatial distribution of above quantities is considered for winters of 1983-84 and 1984-85 during which the strong positive phase of the NAO has been changed with strong negative one. Also, similar analysis is carried out for winters of 1987-1988 and 1988-1989 that have been characterized with small-negative-to-large-positive phase change of the NAO. Spatial distribution of PW depends poorly on fluctuations of the NAO indices and has a kind of a ridge with an axis that is directed from the Gulf of Mexico toward the British Isles. During winter-to-winter decrease of the NAO indices the reduction of TP, SE and CF is registered over Danish Strait and increase of TP is observed over Azores. On the contrary, when the NAO indices reach the maximum, the zone of significant TP, SE and CF is stated over Ice-land.
Thus, the fluctuations of the NAO indices, i.e. circulating conditions over North Atlan-tic, have an effect for spatial structure of some moisture characteristics.
Extended Abstract (1.2M)
Joint Poster Session 1, Spatial and Temporal Variability (Joint with the Symposium on Observing and Understanding the Variability of Water in Weather and Climate and the 17th Conference on Hydrology)
Monday, 10 February 2003, 2:30 PM-2:30 PM
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