Variability Of Sunshine Duration Research Articles

Atlantyk Północny a klimat Europy. Mechanizmy wpływu. Część 1

The work discusses the mechanisms operating within the climate system leading to variability and changes in the atmospheric climate over Europe. The first part discusses the operation of the main factor regulating the variability of atmospheric circulation, which is the North Atlantic thermohaline circulation (NA THC). The variability of NA THC, through its influence on the shaping of the mid-tropospheric circulation and the distribution of geopotential heights, determines the variability of the lower circulation, and thus the variability of climatic elements over Poland and Europe. The analysis showed that the variability of NA THC largely explains the variability of sunshine duration, air temperature and relative humidity, but does not satisfactorily explain the variability of other climatic elements.

Dual carbon and oxygen isotopes in Siberian tree rings as indicator of millennia sunshine duration changes

The current lack of information on past summer sunshine duration variability from annually resolved palaeoclimatological archives is hindering progress in the understanding and modelling of the earth climate system. We show that a combination of tree-ring carbon and oxygen isotopes from Siberia provides robust information on summer sunshine duration, which we use for an annual 1505-year reconstruction of July sunshine duration variability (1,5K-SIB-JSDR). We found that the Medieval maximum is 56 % higher than the average over 1505 years. Rapid and drastic decreases in sunshine duration up to 60 % correspond to major stratospheric volcanic eruptions. Grand Solar Minima and total sunspot numbers are also well preserved in the 1,5K-SIB-JSDR. Coherency with a global air temperature composite and spring Arctic Oscillation indicate that a large-scale climate signal is retained in our sunshine reconstruction.

Variability of Sunshine Duration in Western Ukraine

The duration of sunshine is a crucial radiation characteristic of climate, serving as an indicator for both regional atmospheric circulation and surface atmospheric pollution variability. Ground observations using a heliograph, spanning a long duration, enable the detection of changes in the impact of climate-forming factors on modern warming. Since the 1980s, more precise, high-resolution CMSAF satellite data has allowed for the determination of spatial variability in sunshine duration over recent decades. From 1371 to 1934 hours of sunshine per year were observed in Western Ukraine during 1961–1990, with the southwestern regions of the Transcarpathian lowland being the sunniest. Some years exceeded 2000 hours, indicative of a Mediterranean climate. Typical latitudinal changes were not found, but instead, a noticeable development of continentality, expressed in an increase in annual sunshine duration from west to east was found. Over the year in 1961–1990, significant differences in sunshine duration exist. Generally, the highest values occur in July, exceeding 250 hours in the southeast, southwest, and even in the northwest. The northwest and other western weather stations show high sunlight variability in June and July, linked to North Atlantic cyclones and increased cloudiness. The lowest seasonally determined total duration of sunshine during 1961–1990 occurred in December (<50 hours), with low values and a high number of days without sunshine (up to 20 days) typical for low-mountain valleys of the Carpathians and the northwest (27–38 hours). The most complex distribution is in autumn and spring, with a well-expressed latitudinal distribution from north to south: an increase in autumn and a decrease in spring due to transformation of seasonal circulation processes. In the last thirty years, changes in sunshine duration in Western Ukraine correspond to pan-European trends associated with global brightening. These changes are generally insignificant throughout the year, except for January and the western part of the region. In July, a slight statistically significant increase in the duration of sunshine was detected only in the west and in the foothills during 1961–2020. We associate these features with the higher frequency of anticyclonic types of weather and therefore with fewer cloudy days. These changes are noticeable in the Prut-Dniester highland and the eastern Podilska highland. The spatial distribution of sunlight duration indicates variability near the Carpathian Mountain system and above the highlands. The manifestation of the barrier function of mountains is manifested in an increase in values in winter due to altitudinal differentiation and a decrease in summer. Disctinctive changes east from the influence of the Carpathians are observed in the summer period. Similar peculiarities on a smaller scale were found over the Khotyn and Podilska highlands. The seasonal distribution of sunshine duration in Chernivtsi from 1991–2020 shows significant variability in spring and autumn. In the first decade of this period, low values corresponded to the low solar activity of the 22nd solar cycle. The last two decades, with significant fluctuations, especially in May, August, and September, and extremely high values in separate years, did not coincide with the least active recent solar cycles. Instead, they indicate the variability of circulation systems, especially in the west of the region. Identifying the impact of this factor, along with the growing atmospheric pollution in recent years, constitutes the perspective of our research. Keywords: sunshine duration, climate variability, regional atmospheric circulation, atmospheric pollution, satellite data.

The influence of atmospheric circulation over Central Europe on the long-term variability of sunshine duration and air temperature in Poland

The aim of this study is to analyse the influence of atmospheric circulation over Central Europe on the long-term variability of relative sunshine duration (RSD) and air temperature in Poland. The analysis of data from 23 stations located in different parts of the country has made it possible to indicate to what extent the trends of these two climate elements are related to atmospheric circulation and whether they occur throughout the year or only in certain months. To this end, the author's own classification of circulation types was used, which relies on a set of indices related to the velocity and direction of geostrophic flow, as well as total shear vorticity, calculated using a gridded data set of sea-level pressures. The results of the research showed that atmospheric circulation over Central Europe has a significant impact on RSD and air temperature in Poland, but not on their upward trends in recent decades. The increase in the average annual values of both these climate elements was marked in almost every circulation type. This contradicts the assumption of classical synoptic climatology, which assumes that circulation types themselves are usually considered to be constant, i.e. that changes in air temperature can be related only to an increase or decrease in the incidence of the circulation types.

Spatiotemporal variability of sunshine duration and influential climatic factors in mainland China during 1959–2017

AbstractSunshine duration (SD) is a key index with which to quantitatively measure the intensity and duration of solar radiation. The exploration of spatiotemporal characteristics and potential influential factors for SD could help us better understand solar radiation variability. In this study, we first explore the spatiotemporal variability of SD across mainland China during 1959–2017, then identify the predominant influential climatic factors and detect their relative influence of temporal dynamic on SD, and finally discuss the relative influential rates of climatic factors and detect the dominating climatic factor on a spatial scale. The results show that: Firstly, the annual and seasonal SD gradually decreased from the northwest to southeast across mainland China; a significant decreasing trend (p < .05) was detected for annual SD at a rate of −2.7 h⋅a–1, a turning point significantly occurred in 1986 (p < .05) in the year SD series, and oscillation periods of 2.4–3.8 years existed in mainland China and most sub‐regions. Secondly, the significant (p < .05) decrease of wind speed (Win), increase of precipitation (Pre), and increase of vapour pressure (Vp) were responsible for the decreasing trend of SD with relative influential rates of 39.9, 30.6, and 29.5%, respectively. Thirdly, temporally, the relative influential rate of each climatic variable changed over time; spatially, Win dominated most areas of mainland China (55.9%) during 1959–2017, followed by Pre (24.9%) and Vp (19.2%).

Sunshine duration in Poland from ground‐ and satellite‐based data

AbstractThe aim of the study is to characterise the spatial variability of sunshine duration in Poland. The study used ground‐based and satellite‐based data from 1983 to 2018 multi‐annual period, from the territory of Poland. The ground‐based data include daily sums of sunshine duration from 29 Institute of Meteorology and Water Management—National Research Institute stations and two stations of the Jagiellonian University. Satellite‐based data from the product “SDU ‐ Sunshine Duration, v003” were used with a resolution of 0.05° × 0.05°, coming from the nearest pixel of a given meteorological station. These values were obtained from the SARAH‐2.1 database, published by The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT). It was found that the mean annual sums of sunshine duration calculated on the basis of ground‐based data in Poland range from about 1,460–1,500 hr in the south and south‐west of the country (mountain areas) to 1,800–1,830 hr in the north—the region of the eastern Baltic coast. Satellite‐based data are in line with ground‐based data in relation to the dependence of sunshine duration on latitude, that is, the increase in sunshine duration from the south to the north in the summer and in the spring, and the decrease in the winter. In the autumn, the spatial variability based on satellite data is more latitudinal than in the case of ground‐based data. Moreover, in the autumn and winter, the sums of sunshine duration based on satellite data are overestimated and, in the summer, especially since the turn of the 20th and 21st century, they have been underestimated. The performed analysis has shown that there is some conformity of the results, but the accuracy of matching satellite‐based data and ground‐based data depends on the location of the station and is subject to fluctuations in the annual and multi‐annual cycle.

Sunshine Duration Analysis as a First Step to Estimate Solar Resource for Photovoltaic Electricity Production in Middle Latitudes

This paper analyzes the spatio-temporal variability of sunshine duration in the south of the Pampeana region as a first approach to solar climatic analysis, main input for the use of this resource. Hourly sunshine duration records from 1991 to 2015 in eight Argentine cities were analyzed using statistics and geospatial techniques. In addition, we analyzed the frequency of clear sky and overcast days in order to relate it to the sunshine duration variability. Sunshine duration in the Pampeana region presented a linear gradient increasing in an east-west direction. An inverse relationship between the mean sunshine duration and coefficients of variation was found in all the cities. The highest mean values of sunshine duration were recorded located between 62°W and 65°W, where the lowest variability was also registered. The city of Mar del Plata showed the lowest mean values of sunshine duration (4.5 h) and the highest percentage of variability (78.1%), whereas Rio Colorado recorded the highest mean values of sunshine duration (7.5 h) and the lowest variability (51.1%) over the observation period. During the warm season, it was recorded a difference of 3.7 h in the mean SD values between the stations Rio Colorado and Mar del Plata. The spatial distribution of the solar resource in the Pampena region is markedly affected by weather systems playing at the regional scale of South America. In the cold season, the west-east movement of the high pressure cells promotes the occurrence of Sudestadas, which explain the variability of sunshine duration over the coastal areas.

Sunshine Duration Variability in Haihe River Basin, China, during 1966–2015

Sunshine can have a profound impact on the systematic change in climate elements, such as temperature and wind speed, and in turn affects many aspects of the human society. In recent years, there has been a substantial interest in the variation of sunshine duration due to the dramatic global climate change. Hence, there is a need to better understand the variation of sunshine duration in order to cope with climate change. This study aimed to analyze the variation of sunshine duration in Haihe River basin, China, and its relationship with temperature, wind speed and low-level cloudiness. The annual, seasonal and monthly changes of sunshine duration were analyzed based on the data collected from 33 meteorological stations over the Haihe River basin during 1966–2015. It is evident that the annual, seasonal and monthly sunshine duration shows a decreasing trend over time. In addition, the annual sunshine duration is lower with a higher climate tendency rate in the southern and eastern coastal regions than that in the northwestern regions. It is negatively correlated with temperature (r = −0.50) and low-level cloudiness (r = −0.29), but positively with wind speed (r = 0.61). Wind speed may be one of the important causes of the decrease of sunshine duration in the Haihe River basin during 1966–2015. These changes may have significant implications for the hydrological cycle in the area.

Interannual and Decadal Variations of Surface Solar Radiation over East China in the First Half of the 20th Century

AbstractVariability and long-term trends of sunshine duration (SSD) and total cloud cover (TCC) were studied based on surface observations from 10 meteorological stations over East China in the first half of the 20th century. The correlation coefficients between SSD and diurnal temperature range (DTR), as well as TCC, were analyzed. SSD experienced a significant increasing trend (0.16 h d−1 per decade) from 1908 to 1936, and the maximum brightening was in autumn (0.33 h d−1 per decade). The good agreement between the variability of SSD and DTR, supported by the correlation coefficient between them of 0.72, implies that the SSD measurements were reliable. TCC showed a decreasing trend (-0.93% per decade) and was significantly inversely related to SSD (-0.74), indicating the variation of SSD was attributable to changes in cloud cover. The result was obviously different to that since the 1960s, when clouds could not account for the decadal trend of surface solar radiation in China.

Sunshine duration variability and trends in Italy from homogenized instrumental time series (1936–2013)

AbstractA data set of quality checked daily sunshine duration measurements was collected from 104 Italian sites over the 1936 to 2013 period. Monthly mean values were homogenized, projected onto a grid, and subjected to principle component analysis, which identified two significantly different regions: North and South. Sunshine duration temporal evolution is presented, and possible reasons for differences between the two regions are discussed in the light of a comparison with the trends found in observations of total cloud cover and with results from two neighboring regions: the Alps and Spain. In addition, trends for irradiance records, estimated from sunshine duration records using the Ångström‐Prescott formula, are presented too. The major feature of the trends, an increase in sunshine duration from the mid‐1980s, was common to both northern and southern Italy; the decrease in the preceding 30 year period was not, as northern Italy had a lower rate of decrease than southern Italy. The few records available during the earliest period of the data set indicate that sunshine duration in Italy increased from the mid‐1930s to the mid‐1950s. The further steps needed to identify and quantify the mechanisms giving rise to the observed trends and to the reported regional differences in dimming and brightening are outlined.

Relationship between sunshine duration and air temperature and contemporary global warming

The purpose of this paper is to describe the variability of sunshine duration and air temperature and to assess the relationship between these variables. The paper is based on daily means of air temperature and daily sunshine duration totals from the 1884–2012 period. The variability analyses of these variables for the whole period is supplemented by additional trend analyses for two separate time periods described in the literature as dimming (1958–1985) and brightening (1985–2012). All the data come from the Jagiellonian University Research Station in Krakow. In Krakow, there is a decrease in the number of sunshine hours in the 1950s to 1980s period followed by an increase in the last two decades of the 20th century. The long-term course of air temperature in Krakow confirms the results obtained in other places in the world and exhibits increasing warming of the climate. The temperature increase is visible in each month but is highest in winter (exceeding 1.5 °C per 100 years). Therefore, it may be assumed that the increase in air temperature, which has been particularly strong since the 1980s, showed the full effect of global warming in the brightening period that was previously masked by global dimming as shown in the sunshine duration records. The time course of air temperature for the whole study period (1884–2012) shows a statistically significant positive linear trend. The present warming is influenced probably by the air-quality improvement (brightening period) and an increase in sunshine duration in the years 1980–2012.

Multi annual variability and climatic signal analysis of sunshine duration at a large urban area of Mediterranean (Athens)

This study analyses the interannual variability of sunshine duration (SDU) at the urban area of Athens from 1897 to 2011. Observations of total cloud cover (TCC) are also used for a better interpretation of SDU variations. The annual SDU in Athens has increased by +8% (+19h/decade) over the past century, mainly due to increase in the summer and spring SDU, however, distinct sub periods with decreasing and increasing trends are also discerned. SDU in Athens has undergone an abrupt increase during 1940s with early 1950s being the brightest period of the record. For long periods the course of SDU mirrors TCC, indicating a strong negative correlation between the two variables, nevertheless during the last three decades, both variables reveal trends of the same sign (more evident in spring). Under all-sky conditions, annual SDU decreased by approximately 7% from 1950s to 1980s and increased by 3% thereafter. Under clear sky conditions, the increase of SDU after 1980s is larger, amounting to 9%. Singular spectrum analysis and Continuous Wavelet Transform indicated significant non-linear trends of SDU and an intermittent oscillation, centered at 2.9–3.0yrs.

From brightening to dimming in sunshine duration over the eastern and central Tibetan Plateau (1961–2005)

The Tibetan Plateau (TP) with an average elevation of over 4,000 m asl is the highest and most extensive highland in the world. We used monthly mean sunshine duration from the Chinese Meteorological Administration to examine the spatial and temporal variability of sunshine duration at 71 stations with elevations above 2,000 m asl in the eastern and central TP during the 1961–2005 period. The temporal evolution of the mean annual sunshine duration series shows a significant increase from 1961 to 1982 at a rate of 49.8 h/decade, followed by a decrease from 1983 to 2005 at a rate of −65.1 h/decade, with an overall significant decrease at a rate of −20.6 h/decade during the whole 1961–2005 period, which is mainly due to the summer and spring seasons. This confirms the evidence that sunshine duration in the TP ranges from brightening to dimming in accordance with sunshine duration trends in the rest of China. The surface solar radiation downwards from ERA-40 reanalysis data in the same region confirms the brightening/dimming phenomenon shown by the sunshine duration before/after the 1980s. Otherwise, additional climatic variables such as low cloud amount, total cloud amount, precipitation, relative humidity and water vapor pressure, in most cases, exhibit significant negative correlation with sunshine duration in the TP on an annual and seasonal basis before and after 1982, respectively. The trends of these variables suggest that changes in some of them might be related to the brightening and dimming detected with the use of sunshine duration measurements over the TP. We also hypothesize that the impact of anthropogenic aerosols upon the climatic variables analyzed cannot be rejected, especially in the significant increase in low cloud cover since approximately 1980.

Spatial and Temporal Trends in Sunshine Duration over Western Europe (1938–2004)

Abstract This work analyzes sunshine duration variability in the western part of Europe (WEU) over the 1938–2004 period. A principal component analysis is applied to cluster the original series from 79 sites into 6 regions, and then annual and seasonal mean series are constructed on regional and also for the whole WEU scales. Over the entire period studied here, the linear trend of annual sunshine duration is found to be nonsignificant. However, annual sunshine duration shows an overall decrease since the 1950s until the early 1980s, followed by a subsequent recovery during the last two decades. This behavior is in good agreement with the dimming and brightening phenomena described in previous literature. From the seasonal analysis, the most remarkable result is the similarity between spring and annual series, although the spring series has a negative trend; and the clear significant increase found for the whole WEU winter series, being especially large since the 1970s. The behavior of the major synoptic patterns for two seasons is investigated, resulting in some indications that sunshine duration evolution may be partially explained by changes in the frequency of some of them.

Spatial interpolation of sunshine duration in Slovenia

AbstractThe objective of the present study is the calculation of the spatial distribution of sunshine duration in the territory of Slovenia. Four maps at 1 km resolution were prepared to present the spatial distribution of sunshine duration for winter, spring, summer and autumn. The values on all four maps are 30‐year mean seasonal sunshine duration, calculated from measurements from 43 meteorological stations in the period 1971–2000. The seasonal presentation was chosen due to the high inter‐seasonal variability in spatial distribution of sunshine duration. The values on the maps were calculated on a mathematical horizon, to avoid the influence of geographical, urban and vegetation distortions. The interpolation model is a combination of a multivariate regression model, residual kriging and simple mathematical models. Geographical variables (altitude, latitude and longitude) are used in models to explain the spatial variability of sunshine duration. For each season, regionalisation is performed based on sunshine duration data, derived geographical data and radio‐sounding data. The interpolation models are developed for each region separately and afterwards the calculated layers are merged using GIS techniques. Copyright © 2006 John Wiley & Sons, Ltd.

Comparison of sunshine records and synoptic cloud observations: a case study for Ireland

We compare the trends and inter-annual variability of sunshine duration and synoptic cloud data for three sites in Ireland. Our results suggest that, although observers are usually consistent in their synoptic cloud estimates, they can show a significant personal bias which makes it difficult, if not impossible, to extract meaningful information on long term trends in synoptic cloud cover. A study of the frequency of totally clear skies, however, suggests that this parameter may be less affected by bias and could indicate meaningful trends in total cloud factor. It is concluded that sunshine measurements are likely to provide the most reliable indicators of long term trends in cloudiness.

Fluctuation of sunshine duration in central and South‐Eastern Europe

AbstractSunshine duration fluctuation in this century is studied from annual values for 26 stations in central and south‐eastern Europe. Possible sources of inhomogeneity are identified: ageing of the glass ball in the sunshine recorder, changes in instruments, the recording tape and its evaluation, and location of the station, and exposure to air pollution. Long‐term changes of annual sunshine duration are presented using a smoothed Gauss filter and principal component analysis. The main feature of sunshine duration fluctuation in this century is its sharp decrease after a maximum at the end of the 1940s. Principal component 1 shows, with small exceptions, positive loadings for the year and its seasons (for the period of 1931–1985). Principal component 2 divides the region studied into two parts, with positive loadings in the western and northern parts of central Europe and negative loadings over the rest of area analysed. A contradictory situation occurs only in autumn. Statistically significant cycles occur at intervals of about 2.3–2.4 years (western Germany), 3 years (Greece), 3.5–3.7 years (central Europe and Bucharest) and 3.7–4.0 years (Bulgaria). Some of the stations used indicate longer cycles (44–110 years). Comparison of coldest (1901–1920) and warmest (1934–1953) 20–year periods in the Northern Hemisphere shows for the warmest period an important increase in sunshine duration, with the exception of Athens and Bucharest and some other stations in winter. In the warmer period sunshine duration variability is generally higher in spring and winter and less in summer and autumn.

REGIONALITY OF CLIMATE IN HOKKAIDO CHARACTERIZED BY SUNSHINE DURATION AND DAILY MEAN TEMPERATURE VARIATIONS

In order to clarify climatic regionality in relation to synoptic meteorological phenomena, the daily duration of sunshine and the daily mean temperatures at about 140 sites in Hokkaido are analysed with time variation (day-to-day variation). Both principal compo-nent analysis and cluster analysis using factor loadings are applied. The values of the factor loadings correspond to the correlation coefficients between the principal component and the climatic element of each point, and also indicate the time coefficients between them. The daily data for 1978_??_1980 were used in this study. Each datum was converted into a deviation from the areal mean for each day. The data for 1978 were mainly used for the analysis, although the results were compared with those for other years to examine the propriety of the results. The first three dominant patterns of the daily variability of sunshine duration account for more than 50% of the total variance. The first eigenvector (24.8% of the total vari-ance) depicts the area of positive (negative) departure to the northwestern side of Ho-kkaido with the area of negative (positive) departure to the southeastern side (Fig. 2-a). The positive pattern (i, e., the total duration of sunshine over the area with a positive sign is relatively greater than that of the area with a negative sign) prevails in summer. This is due to the reduction of sunshine in the southeastern side as is influenced by cyclon-es passing through the southeast of Hokkaido or by sea fogs which are caused when southeasterly warm monsoons blows over the cool Chishima Current. In winter the nega-tive pattern prevails; it reflects the diminution of sunshine in the northwestern region as is influenced by snow clouds accompanying winter monsoons. The second eigenvector (17.2% of the total variance) indicates the contrast between the northeastern side (Okhotsk side) and the southwestern side (Donan side) of Hokkaido (Fig. 2-c). Each of these positive or negative patterns is formed with the influence of both the front and the passage of cyclones in the warm season. The pattern of the third eigenvector (9.3 % of the total variance) describes three areas, i. e., one positive area which extends from the northeast to southwest with two negative areas on either side (Fig. 2-e). This positive pattern appears clearly in summer. It is formed with the influence of both the sea fog mentioned above and cyclones passing over the north of Hokkaido. Furthermore, this pattern tends to appear at the same time as the first component of the sunshine duration has a dominant positive value. On the other hand, the negative pattern, which is caused with the influence of fronts passing over the center of Hokkaido, does not turn out clearly. From these results, four regions with different time variation types of sunshine duration are pointed out. These are the Pacific side type, the Japan Sea side type, the Sea of Okhotsk side type, and the Donan side type (Fig. 8). Especially, the southeastern side of Hokkaido which is belonging to the Pacific side type has fairly specific regional properties of the sunshine duration in comparison to other regions. The first three eigenvectors of daily mean temperature variations account for 43.1%, 14.4%, and 10.6% of the total variance, respectively (i. e., cumulative for 68.1% of the total variance). The pattern of the first eigenvector which distinguishes the inland area from the coastal area is caused by the land-sea heating contrast (Fig. 4-a). The distribution pattern of the second eigenvector closely resembles that of the first eigenvector of the sunshine duration (Fig. 4-c). Both positive and negative patterns prevail in early summer and winter, whose causes are explained by the cooled or warmed wind over the sea in each season.