Cloudiness and sunshine in cracow, 1861-1980, and its contemporary tendencies
✍ Scribed by Morawska-horawska, Maria
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1985
- Weight
- 587 KB
- Volume
- 5
- Category
- Article
- ISSN
- 2314-6214
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✦ Synopsis
The averages of daytime cloudiness for each year from 1861-1980, smoothed by taking 11-year consecutive averages (in view of the 11-year cycle of the sun's activity), closely resemble a sinusoid with minimum values occurring from 1903-1906. Sunshine values, likewise smoothed, can also be compared to a sinusoid, that is a descending sinusoid. It is worth noting the coincidence of the descending tendency of both graphs in the last 25 years.
The correlations between relative sunspot numbers and cloudiness showed a positive dependence with a time-lag of 5 7 years, and the strongest correlation, expressed by r = 0.32 (significance level 0-OOl), occurs with a lag of 6 years after the maximum sunspot number.
Sunshine and relative sunspot number show a negative correlation with time-lags of 6-11 years, and the strongest correlations occur with a lag of 8 years after the maximum sunspot number, and are expressed by the value r = -0.34 (significance level 0.001).
A harmonic analysis of detrended data for various periods of time in the space of 122 years, showed two periodicities of cloudiness: 14.3 and 3.6 years respectively. The first is very close to the known periodicity of precipitation and temperature in Cracow. As regards sunshine, the significant periodicities are as follows: 22.2, 10.3 and 3-6 years, respectively. The first two seem to be associated with the 11-year cycle of solar activity. The 3-6-year periodicity is probably connected with the identical periodicity in cloudiness.
On the basis of the results obtained for Cracow, it cannot be ascertained whether the recorded cycle of sunshine and cloudiness is a regional phenomenon or one of wider consequence.
A decline in cloudiness over the past 25 years is connected with rapid growth of Cracow which took place in that time. This caused the drying up of the air, and a decline in cloudiness.
Despite the decline in cloudiness (at its highest at noon), there persists in Cracow a decline in sunshine which has existed since 1890 and which has steadily increased over the past 30 years. It has been caused by the industrialization of Cracow which took place after 1950, and is connected with increase in air pollution.