Northern Hemisphere gross circulation types. Climatic change and temperature distribution

Abstract

In this work the atmospheric circulation patterns over the N Hemisphere are objectively revealed and discussed, applying Factor Analysis, T-mode, on monthly grid point data of surface pressure. The analysis has been effected for January and February on the one hand and for July and August on the other. The results were similar in adjacent months in almost every respect. Using the Monte-Carlo technique, up to 6 circulation types (factors) were found statistically significant (at 0.05 level) during the high winter months, in the 100 year period 1890-1989, but 2 of them comprise very few years only. The first pattern refers mainly to Europe and Asia, the second to the Atlantic, the Pacific and the adjacent coasts, the third to the whole N Hemisphere and the fourth (5 cases only) mainly to the N Pacific. For the high summer months, only two factors were found, affecting mainly the polar regions. In the first, a polar low appears and in the second a polar high. For the remaining regions worth mentioning pressure anomalies appear over NW Europe only. The time series of patterns indicates a climatic change in atmospheric summer circulation, leading to corresponding changes also in other meteorological parameters (e.g., precipitation). Finally, using 1000-500 hPa thickness data for the post-war years, the temperature distribution of the revealed patterns is shown to be in accordance with the prevailing wind field.

Keywords

• atmospheric
• surface pressure
• climatic change
• wind field
• topography
• atmosphärisch
• bodendruck
• klimawandel
• windfeld
• topographie