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2007 | 7 |
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Cechy solarne klimatu Łodzi

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The objective of the study was the characterization of solar regime of Łódź and the
surroundings e.g. the daily, the annual, the long-term variability of sunshine duration and total
and UV solar radiation, the structure of sunshine duration with a special consideration of
sunless and very sunny days, the relationship between solar components of climate, the
influences of clouds on solar radiation income to an active surfaces, etc. The experimental
materials for the study constituted of the daily totals of actual and relative sunshine duration
in the period 1951-2000, the daily sums of total solar radiation in the period 1991-2002,
measured in the Łódź-Lublinek station (S-W part of the city), 5-year data series of 10-minutes
averages of intensity (in Wm-2) of total (305-2800 nm) and UV (290-400 nm) solar radiation
in the period 1997-2001, registered in the city center of Łódź. The long-term tendencies of sunshine duration were analyzed by means of linear regression
method and sequential version of the non-parametric Mann-Kendall test. All months excluding
March, June and September are distinguished by a growing tendency of actual and relative
sunshine duration. The number of sunny hours increases in spring, summer and winter, and
decreases in autumn. An increase of annual sunshine duration totals (3.5h/year) within the
50-year period was stated. Transformation of the annual course of sunshine duration within 50-year period was
detected. The annual maximum of sunshine duration during the first 25-year period occurred
in June and September. The second 25-year period was characterized by increase of the
number of sunny hour in May and August and by decrease of sunshine duration in June and
September. The time of registration of sunshine duration extended in the morning hours and
before the Sun set as a consequences of low cloudiness negative trend. The structure of sunshine duration in Łódź was presented in 5 classes of possible sunshine
duration (0 - sunless days, 0.1-25% - cloudy days, 25.1-50% - moderately sunny days,
50.1-75% - sunny days, > 75% - very sunny days). Only very sunny days were distinguished
by a positive annual totals trend, on average 4 days per 10 years.
The tendencies of sunshine duration recorded in Łódź within fifty last years are representative
for Poland and result from the macroscale factor (atmospheric circulation) not only
from the influences of local (anthropogenic) conditions.
The regular fluctuations in the time series of sunshine duration and solar radiation were
investigated by Blackman-Tukey classical spectral analysis method.
The weak periodicity (statistical insignificance) amounted 8.3, 2.5, 2.8, 3.8 years and the
significance short oscillations amounted 182.5, 91.2, 73 days were detected in sunshine duration
time series. The total and UV solar radiation time series were characterized by 182.5, 121.7, 73
days significance periodicities.
The values of transmission coefficient of total and UV solar radiation were investigated.
The daily values of transmission coefficient varied from 25% (total radiation) and 14% (UV)
in December to 50% (total radiation) and 26% (UV) in May.
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Publication order reference
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