DIRECT SOLAR RADIATION AND ATMOSPHERIC TURBIDITY IN MIKOŁAJKI IN THE YEARS 1971–1980 AND 1991–2000

The present study deals with the changing amount of incoming direct solar radiation and the optical state of the atmosphere in Mikołajki in the years 1971–1980 and 1991–2000. The highest level of solar irradiance in these two decades occurred on 23rd June 1977 and amounted to 1043.9 W·m-2. Compared to the first decade analysed, the percentage of the solar constant reaching the Earth in the second decade was higher. The spectral structure of the radiation also changed – the share of the shortest waves (λ<525 nm) increased, whereas the amount of waves with a wavelength of 710 nm or more decreased. In both study periods the annual course of solar extinction (expressed in terms of Linke’s turbidity factor) turned out to have been typical, with the highest values in summer and the lowest in winter. In the years 1991–2000, in all seasons, a lower atmospheric turbidity was observed in comparison with the years 1971–1980. The atmospheric turbidity was also analysed with relation to the air masses. In both decades in question the lowest turbidity occurred in arctic air masses and the highest in tropical air masses. An improved optical state of the atmosphere was observed in all considered air masses, though the biggest decrease in turbidity was found in polar air masses, particularly in the polar maritime old air (TLAM2 dropped by 0.75) and polar continental air (by 0.70).The present study deals with the changing amount of incoming direct solar radiation and the optical state of the atmosphere in Mikołajki in the years 1971–1980 and 1991–2000. The highest level of solar irradiance in these two decades occurred on 23rd June 1977 and amounted to 1043.9 W·m-2. Compared to the first decade analysed, the percentage of the solar constant reaching the Earth in the second decade was higher. The spectral structure of the radiation also changed – the share of the shortest waves (λ<525 nm) increased, whereas the amount of waves with a wavelength of 710 nm or more decreased. In both study periods the annual course of solar extinction (expressed in terms of Linke’s turbidity factor) turned out to have been typical, with the highest values in summer and the lowest in winter. In the years 1991–2000, in all seasons, a lower atmospheric turbidity was observed in comparison with the years 1971–1980. The atmospheric turbidity was also analysed with relation to the air masses. In both decades in question the lowest turbidity occurred in arctic air masses and the highest in tropical air masses. An improved optical state of the atmosphere was observed in all considered air masses, though the biggest decrease in turbidity was found in polar air masses, particularly in the polar maritime old air (TLAM2 dropped by 0.75) and polar continental air (by 0.70)

Solar radiation variability at Koniczynka near Toruń (Central Poland) in the years 2003–2016

The paper presents the variability of global solar radiation (K↓) in the agriculture area (Koniczynka near Toruń) in the years 2003–2016. The variability of K↓ has been analysed with reference to atmospheric circulation. The mean yearly sum of K↓ in the analysed period was 3,816.0 MJ m-2. In an annual course the biggest mean values of K↓ occurred in June (608.3 MJ m-2) and the smallest in December (69.0 MJ m-2).The diurnal course of K↓ was symmetrical with respect to the solar noon.  Only 44.7% of the solar energy on the top of atmosphere reaches the ground. The highest transmittance occurred in spring and summer, and the lowest in December. The observations revealed an increase in the amount of K↓ (trend 13.6 MJm-2 year-1) and its considerable day-to-day and year-to-year variability. Its increase has been attributed to reduced emissions of aerosols in Poland and Europe (global brightening). The changes of K↓ depend on atmospheric circulation (cyclonic and anticyclonic situations), cloudiness and the optical characteristics of incoming air masses.

Comparison of the Linke turbidity factor in Warsaw and in Belsk

The article describes the relationship between direct solar radiation in a city (Warsaw) and in its broadly-defined suburban area (Belsk). The analysis covers the days of 1969-2003 when observations were carried out at both sites. The degree of extinction of solar radiation was expressed by means of Linke’s turbidity factor. Its mean annual value on the selected days of the period under consideration was 3.00± 0.10 at Warsaw and 3.00±0.11 at Belsk. Any differences in the atmospheric turbidity between the Warsaw site and Belsk in individual seasons of the year were marginal and within the error margin of Linke’s factor. The period considered was also divided into two sub-periods (1969-1993 and 1994-2003), in which atmospheric turbidity in Warsaw and in Belsk was compared by individual seasons and whole years. At both analysed sites Linke’s atmospheric turbidity factor decreased in 1994-2003, compared to the values for the earlier sub-period (1969-1993). The differences in atmospheric turbidity between the Warsaw site and Belsk are small and often statistically insignificant. The reason for this is, perhaps, the location of the urban measurement site far from the city centre, even though the site was still situated in a typically urban environment

Conditions influencing incoming global solar radiation in Hornsund (Spitsbergen) in spring 2015

This article analyses the conditions affecting the incoming global solar radiation in Hornsund (Spitsbergen) in spring of 2015. Incoming solar radiation turned out to be average for the season under analysis, as compared with longer-term data. The clearness index (KT) was 0.46, and was mainly determined by the extent of cloudiness. As a result of differences in the length of day, sunshine duration in May was greater than in April. Incoming solar radiation to the earth’s surface is also affected by the atmospheric optical properties. The average value of aerosol optical depth (AOD) at 500 nm in Hornsund in spring of 2015 was 0.087. In the analysed period, increased values of AOD at 500 nm (up to 0.143) were observed, although these are not record values. Over April and May, the greatest part of optical depth was comprised of anthropogenic aerosols (41%), followed by marine aerosols (26%), desert dust (21%) and biomassburning aerosols (12%). This indicates the significant role of the anthropogenic factor in the climatic conditions of Spitsbergen

SPATIAL DIFFERENTIATION OF GLOBAL SOLAR RADIATION IN TORUŃ AND ITS SUBURBAN AREA (CENTRAL POLAND) IN 2012

This article investigates the spatial distribution of global solar radiation (K↓) in Toruń and its suburbs, observed in 2012. Measurements were taken at 12 points (7 within the city and 5 in the suburban area) using CNR4 net radiometers and automatic weather stations (Vantage Pro+). At all locations, the diurnal and annual courses of K↓ were typically related to the Earth’s rotational movement and changes in the sun’s declination over the year, and disturbed by clouds and atmospheric phenomena that enhance the extinction of solar radiation. A substantial spatial diversity of K↓ was observed in Toruń and its suburbs. The annual sum of K↓ at several urban locations accounted for over 70% of the solar radiation in the open space outside the city. The amount of incoming solar radiation in the urban area was more restricted in winter (<50%) than in summer (approx. 70%). The diurnal courses of K↓ were heavily disturbed by local obstacles which cast shadows (causing a considerable decrease of K↓), but there were instances of increases in K↓ (122%) augmented by radiation reflected from roofs, walls and windows surrounding the measurement point. The spatial diversity of K↓ in the urban area is heterogeneous, due to local meteorological conditions (cloudiness, fog, smog and airborne dust) and the obscuring of the horizon