INTRODUCTION

The climatologic studies concerning the long-term series of the actual insolation measurements for the Beskidy Mountains health resorts are very rare (Kaczmarski and Paszyński 1981, Kaczmarski 1982, Koźmiński and Michalska 2004, Krawczyk 2005, Durło 2006). Very sporadic networks of actinometric stations in southern part of Poland, and a lack of synchronous measurement series, hinder a detailed elaboration of this element for a chosen area. However, the interest in solar energy in connection with observed and forecasted climatic changes in Europe becomes larger and larger. Apart from the obvious role played by the direct solar radiation in life of man, there are possibilities of its utilization for the energetic purposes, alternatively to exploitation of natural resources. The increase of insolation, observed in last years, justifies the undertaking of research on the climatic potential of the Krynica Zdrój health resort in the aspect of utilization of solar energy in climatotherapy (Kozłowska 2005). The aim of this study was to determine the variation of the actual insolation in the Krynica Zdrój health resort on the basis of the long-term measurements and observations conducted at meteorological stations situated on this area.

METHODS

The material for this study consisted of results of measurements of the actual insolation gathered at the two meteorological stations of the Institute of Meteorology and Water Management in Krynica Zdrój, as well as results of observations on the cloud cover carried out by the meteorological station of the Agricultural University of Cracow situated in Mochnaczka Wyżna. Detailed data concerning the location of these stations are in Table 1. 

The measurements of the actual insolation were conducted at the station in Krynica Zdrój during 1971-2005 using the Cambell-Stokes heliograph placed 200 cm above the ground. The observations on the cloud cover were conducted at three stations in III observation times. A long-term variation of the actual insolation in the Krynica Zdrój presented in this paper, was calculated on the basis of the diurnal sums of insolation obtained from the Krynica Zdrój station, and mean daily values of the cloud cover from the both meteorological posts. To calculate the actual insolation on the basis of daily values of the cloud cover the values of coefficients according to Koźmiński and Michalska (2000) were used. In order to determine a long-period variation of heliographic conditions the index values for monthly, seasonal, and annual periods were utilized. For calculated indexes the trends, representing a general direction of changes of insolation during the period 1971- 2005, were worked out. The trend testing was based on the model of linear regression, using a variant of the classic least squares method 1MNK. The estimation of quality of the model fitting was accomplished on the basis of the following characteristics:

1. Coefficient of determination R2: look at Fig4a.

2. The F statistic, estimate of linear dependence between variables, testing on the basis of hypotheses: look at Fig4b.

3. Residual standard deviation: look at Fig4c.

4. Ratio of expressiveness w: look at Fig4d.

To estimate the significance of regression coefficients the values of standard errors of parameter estimators were used. Values of the estimators β1 (intersection) and β0 (coefficient of direction) and their errors were determined on the basis of the following formulae: look at Fig4e.

The significance of model parameters were tested on the basis of the statistics tStat determined by the formulae: look at Fig4f.

The statistics has Student’s t-distribution with the df freedom number. Testing of significance of the model parameters was accomplished on the basis of hypotheses: look at Fig4g.

The last estimation of quality of the model fitting was the determination of confidence intervals for  estimators β1 and β0, and comparison of results obtained with values of lower and upper limits of intervals. Confidence intervals were determined according to the following formulae: look at Fig4h.

Besides the estimation of development tendencies the decomposition of time series was made on the basis of mean monthly sums of the actual insolation from the period 1971-2005, using the Winter’s additive model, taking into account linear trends, seasonal components, and a random component. The estimation of fitting of the model exponential smoothing was based on the mean percent absolute error expressed by the formula: look at Fig4i.

Calculations of basic statistical measures, estimation of significance of regression models, and the procedure Census 1 for time series were made in the program STATISTICA 7.1 PL (StatSoft, Inc.2004).

RESULTS

The long-term mean annual sum of the actual insolation in the Krynica Zdrój health resort was 1705 hours with deviation of 199 hours. August and December were the months with the highest and the lowest mean sum of insolation hours: 288 hours with deviation of 44 hours, and 60 hours with deviation of 25 hours respectively (Table 2). The lowest monthly sum of the actual insolation occurred in December 1988, amounting to only 17 hours, while the highest one occurred in August 2003-303 hours, which made 67.0 % of the potential insolation. March, May, and June were characterized by the greatest values of the mean deviations, while November and December by the smallest ones (Fig. 1). The mean sum of the actual insolation in individual seasons was also quite variable (Table 3). During the summer season it was twice as great as in autumn. The sum of the actual insolation in summer was 590 hours with deviation of 80 hours. The greatest seasonal sum of the actual insolation occurred in spring 2000 amounting to 811 hours, at the seasonal average of 567 hours. Also the insolation amplitudes indicated a great diversification of this element within individual seasons. In spring they amounted to over 400 hours, in summer and winter about 340 hours, while in autumn a little below 200 hours (Table 3). Proportion of the actual insolation in autumn in respect of the annual sum was 16.0%, and it was the lowest among all seasons (Fig. 2). Autumn is also the season during which the deviation and amplitude were reaching the smallest values (Table 3). The long-term mean sum of the actual insolation during the growing season was 1252 hours, which made 40% of the potential insolation. The highest sum of the actual insolation during the growing season occurred in 2000, amounting to 1505 hours (Table 3). During 35 years only in two cases, i.e. in 1978 and 1980, the annual sum of the actual insolation was lower than 1000 hours, coming close to 30% of the potential astronomic insolation.

During the period investigated, 1997 was the most sunny year, when the total time of a direct solar radiation was 2145 hours. The least sunny year was 1978 and 1980, when the actual insolation was 1363 hours (Fig. 2).

Characteristics of linear trends, calculated on the basis of data from the period 1971-2005, indicated a significant increasing trend of the actual insolation in January, but a low value of the sharpness index indicated that forecasting on the basis of the development equation is uncertain (Table 4). In the remaining cases the trend equations yielded results statistically insignificant. A general annual trend of the actual insolation in the Krynica Zdrój health resort is positive, but statistically insignificant. The analysis of time series carried out using the Census1 method, and based on the centered moving averages indicated a positive increasing trend of the actual insolation in the Krynica Zdrój, but its statistical estimation is insignificant (Fig. 3).

A 10-year forecast for the period 2006-2015, made using the Winter’s method, on the basis of a 35-year series of data, showed a growing trend. However, the additive Winter’s model, along with a linear trend and seasonal as well as random fluctuations, did not fit to empirical data with a required accuracy. The mean absolute error was nearly 30%, and this indicated a low accuracy of the forecast.

RECAPITULATION

The actual insolation in the Krynica Zdrój health resort is characterized by a high variation in respect of time and space. This character results in the first place from a strong relationship between the duration of a direct solar radiation and the cloud cover as well as the orographic conditions. In temperate warm climatic zone (Hess 1965) including areas situated on slopes, summits and on mountain ridges the diversification of insolation in individual months was reaching as much as even 20 hours. The annual sum of insolation varied from about 1600 hours in Krynica Zdrój to over 1850 hours on ridges. General solar qualities of the Krynica Zdrój Community belong to very favorable ones. The comparison of results of this study with results of studies carried out during 1950-1970 indicated a visible improvement of solar conditions, especially in spring, i.e. April and May (Boniecka-Żółcik 1966, Baranowska et al. 1978). High annual sums of insolation in 2000 and 2003 affected the value of the coefficient of direction of the long-term trend. However, they do not provide the basis for conclusion about a steady insolation tendency in this part of the Beskid Sądecki Mts.

CONCLUSIONS

1. The highest long-term mean monthly sum of the actual insolation in the Krynica Zdrój health resort falls on August, amounting to 208 hours, and the lowest falls on December – 60 hours.

2. The highest sums of insolation occured on upper part of temperate warm climatic zone 737 m a.s.l., and they reached 1845 hours (Góra Parkowa).

3. In comparison with measurement series of insolation for the period 1950-1979 an improvement of solar conditions may be observed, especially in the moderately warm climatic zone at 500-700 m in elevation.

4. On the basis of the forecast of the actual insolation in the Krynica Zdrój Community made on the basis of data for the period 1971-005 no conclusion about a directional change of this element may be made with a required accuracy.

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REFERENCES

1.    Baranowska, M., Gurba, A., Boniecka-Żółcik, H. 1978: Bioklimat Krynicy [W:] Jankowiak J. red. Bioklimat uzdrowisk polskich. Wyd. WKiŁ, Warszawa, 1, 12, 183-204.

2.    Boniecka-Żółcik, H. 1966: Bioklimat Krynicy Zdroju. Wiad. Uzdrow. 1, 1-16.

3.    Cebulak, E., Czekierda, D., Falarz, M., Limanówka, D., Niedźwiedź, T., Ustrnul, Z. 1996: Climate variability in Poland during last 45 years. (In:) Obrębska-Starklowa B., Niedźwiedź T. (Eds.). Zesz. Nauk. UJ. Prac. Geogr., 102, 395-402.

4.    Kaczmarski, M., Paszyński, J. 1981: Zmienność dobowa i sezonowa usłonecznienia w Polsce. Przegl. Geogr., 53, 780-791.

5.    Kaczmarski, M.1982: Usłonecznienie w Polsce w okresie 1961-1970. Czas. Geogr., 53, 149-157.

6.    Koźmiński, Cz., Michalska, B. 2004. Zmienność usłonecznienia rzeczywistego w Polsce. Acta Agrophis., 2, 291-305.

7.    Krawczyk, B. Specyficzne cechy bioklimatu Krynicy Zdroju. Baln. Pol. 67, 3, 101-105.

8.    Michna, E., Paczos, S. 1969: Zachmurzenie, usłonecznienie i promieniowanie słoneczne w Bieszczadach Zachodnich. Ann. UMCS, sec. B, 23, 25-39.

9.    Niedźwiedź, T. 1981: Sytuacje synoptyczne i ich wpływ na zróżnicowanie przestrzenne wybranych elementów klimatu w dorzeczu Górnej Wisły. Rozpr. hab. 58, UJ, Kraków.

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Adres autora:

nldurlo@cyf-kr.cdn.pl

Wpłynęło: 29. 01. 2007 r.
Zakceptowano: 28. 02. 2007 r.