Wyniki wyszukiwania - BazTech

Ograniczanie wyników

1 Przegląd Geofizyczny

1 2002

Znaleziono wyników: 1

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: gradient TPO

Sortuj według:

Ogranicz wyniki do:

Związki początku termicznego okresu wegetacyjnego w Polsce z anomaliami temperatury powierzchni wody na Atlantyku Północnym (problem prognozy długoterminowej)

Marsz A. A., Żmudzka E.

Przegląd Geofizyczny

2002

Z. 3-4

165-201

The paper presents the results of the inquiry into the relations between the dates of the beginning of the meteorological growing season in Poland and the thermal state of the surface of the Northern Atlantic. The variability of this state (the magnitude of the streams of heat flowing from the ocean to the atmosphere, and the distribution of the areas in which the heat transmission is greater or smaller than on the average) conditions the variability of the atmospheric circulation within the reach of influence of the Northern Atlantic, which, in turn, shapes the variability of the beginning of the growing season in Poland. The properties of the distribution of the anomalies of water temperature in the Northern Atlantic were characterised with 10 representative fields, the ,,grids", while the beginning of the growing season was characterised with the sequences of dates (being the numbers of the day in a year corresponding to the instance of passage of the average daily air temperature through the value of 5°C) from 34 weather stations located in Poland (except for the mountainous areas) in the years 1970-1998. The basic method applied in the study is the correlation analysis. The quasi-synchronous relations were analysed (the dates of the beginning of the growing season were correlated with the monthly anomalies of the SST in the particular grids for the same year), as well as the synchronous ones (the shift of the series analysed by one year: the SST from the feth year, the beginning of the growing season - from the k + 1st year). Dependence of the date of the beginning of the growing season on the SST anomalies in some reference grids was established. The dependencies identified are in their majority the asynchronous correlations, and the spatial distribution of the isocorrelates is specific for a definite grid. It was also stated that a more important role in the shaping of the beginning of the growing season is played not so much by the thermal conditions within the particular water areas as by the meridional water temperature gradients between these areas either in a given month or on the average for a period of several months. Attention should be paid to the conformity of the signs of the correlation coefficients for the beginning of the growing season and the SST anomalies appearing a year before, observed synchronously and preceding by 2-3 months the starting instance of the season, and to the distinct spatial and temporal order in the distribution of the SST anomalies, which influence strongly the dates of the beginning of the growing season. The most frequent are the associations with the thermal conditions in the water areas of the Western part of the Northern Atlantic (the Sargasso Sea and the areas to the north of the Gulf Stream delta), with the precedence of the date of the beginning of the growing season amounting to between 11 and 14 months. As time passes, the influence of these water areas fades away and the correlations appear indicating a smaller time precedence (4 to 9 months), concerning the ocean areas located in the moderate latitudes of the central and Eastern parts of the Atlantic Ocean. The article offers, as well, an attempt of a physical interpretation of the results obtained. The paper presents the results of the study aiming at elaboration of the method allowing for the long-term forecasting of the beginning of the growing season for the lowland and upland Poland on the basis of water temperature anomalies of the surface of the Northern Atlantic (their values and spatial distribution). The analysis was carried out with respect to the series shifted by one year: the STT anomalies for the year k, and the beginning of the growing season for the year k + 1. Th study of the nature of relations made it possible to establish that the interdependencies appearing can be described sufficiently precisely with a multivariate linear regression model. In the regression analysis, which was limited - in view of the stability of the regression coefficients - to three independent variables, attention was paid to the relations, which can be physically explained and to those, which simultaneously explain more than 50% of variance of the beginning of the growing season over a broader area, and at least 60% in the zone of the strongest influence. The respective equation has, as well, to satisfy in the zone of appearance of the strongest influence the criterion ofp < 0.001, and the statistical significance of all the three estimates of the directional coefficients of the equation atp < 0.05. Resulting from the multivariate analysis conducted were two prediction equations, fulfilling the prerequisites set. Each of the two equations is proper for a definite part of Poland: 1. Western and Central Poland, 2. Northern and Eastern Poland. These equations contain both the raw data (not normalised monthly averages of the values of the SST anomalies) and the combined variables (like the averages of the values of SST anomalies for the definite water areas from the time periods longer than one month, and the differences of the anomalies between the definite water areas, describing the magnitude of the meridional water temperature gradients, as well as differences of the anomalies for the same water areas between appropriate time intervals). Both equations point out that the primary role from the point of view of the influence exerted by individual ocean areas on the dates of the beginning of the growing season in Poland is played by the heat resources of the Sargasso Sea, which control to a large extent the variations of the thermal conditions over the remaining ocean areas. A simplified verification of the prediction equations was also carried out, having shown that their parameters obtained from the 27-year observation series are stable. In view of the fact that the latest SST anomalies entering the equations date from September, the forecast for the beginning of the growing season in the subsequent year can be formulated already in October.