Global Brightening Research Articles

Yield predictions for photovoltaic power plants: empirical validation, recent advances and remaining uncertainties

AbstractYield predictions are performed to predict the solar resource, the performance and the energy production over the expected lifetime of a photovoltaic (PV) system. In this study, we compare yield predictions and monitored data for 26 PV power plants located in southern Germany and Spain. The monitoring data include in‐plane irradiance for comparison with the estimated solar resource and energy yield for comparison with predicted performance. The results show that because of increased irradiance in recent years (‘global brightening’) the yield predictions systematically underestimate the energy yield of PV systems by about 5%. Because common irradiance databases and averaging times were used for the yield predictions analysed in this paper, it is concluded that yield predictions for areas where the global brightening effect occurred in general underestimated the energy yield by the same magnitude. Using recent satellite‐derived irradiance time series avoids this underestimation. The observed performance ratio of the analysed systems decreases by 0.5%/year in average with a relatively high spread between individual systems. This decrease is a main factor for the combined uncertainty of yield predictions. It is attributed to non‐reversible degradation of PV cells or modules and to reversible effects, like soiling. Based on the results of the validation, the combined uncertainty of state of the art yield predictions using recent solar irradiance data is estimated to about 8%. Copyright © 2015 John Wiley & Sons, Ltd.

The cause of solar dimming and brightening at the Earth's surface during the last half century: Evidence from measurements of sunshine duration

Analysis of the Angstrom-Prescott relationship between normalized values of global radiation and sunshine duration measured during the last 50 years made at five sites with a wide range of climate and aerosol emissions showed few significant differences in atmospheric transmissivity under clear or cloud-covered skies between years when global dimming occurred and years when global brightening was measured, nor in most cases were there any significant changes in the parameters or in their relationships to annual rates of fossil fuel combustion in the surrounding 1° cells. It is concluded that at the sites studied changes in cloud cover rather than anthropogenic aerosols emissions played the major role in determining solar dimming and brightening during the last half century and that there are reasons to suppose that these findings may have wider relevance.

Effects of global brightening on primary production and hypoxia in Ise Bay, Japan

In many parts of the world, annual mean surface solar radiation (SSR) has undergone significant decadal changes; however, its effect on the coastal water environment has not been investigated. This study investigates the effects of changes in the SSR on hypoxia and the primary production of phytoplankton in a eutrophic bay in Japan (Ise Bay), where the annual SSR increased by 13.3% from 1980 to 2010. We numerically simulated the hydrodynamics and ecosystem of 2010 using a three-dimensional model (case O). We used this model to simulate the case where SSR was reduced by 10% (case A) and estimated the effect of an increase in SSR from the difference between case O and case A. With the 10% increase in SSR, the primary production in the bay increased by only 2.8%. This limited increase was the result of the negative effects by the nonlinearity of the light limitation function (including the photoinhibition) and the limitation in PO4–P availability and a significant positive effect by the increased water temperature. Similarly, the overall volume of hypoxic water increased, and in August, it increased by 5.8%. This is because water temperature and biomass such as phytoplankton increased with the increase in SSR; consequently, all oxygen consumption terms such as biological respiration also increased. These results imply that recent global brightening has the potential to amplify the primary production and hypoxia in a eutrophic bay.

近50年来中国地面太阳辐射变化及其空间分布研究

PDF HTML阅读 XML下载 导出引用 引用提醒 近50年来中国地面太阳辐射变化及其空间分布 DOI: 10.5846/stxb201303130409 作者: 作者单位: 西南大学地理科学学院;中国气象科学研究院;青海师范大学生物与地理科学学院,中国气象科学研究院,西南大学地理科学学院,中国气象科学研究院,青海师范大学生物与地理科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 全球变化重大专项(973)项目(2010CB951300); 中加国际合作项项目(2009DFA91900) Variation and spatial distribution of surface solar radiation in China over recent 50 years Author: Affiliation: School of Geographical Sciences,Southwest University;China;Institute of Eco-environment and Agro-meteorology,Chinese Academy of Meteorological Sciences;China;School of life and geographic science,Qinghai normal University;China,Institute of Eco-environment and Agro-meteorology,Chinese Academy of Meteorological Sciences,School of Geographical Sciences,Southwest University,Institute of Eco-environment and Agro-meteorology,Chinese Academy of Meteorological Sciences,School of life and geographic science,Qinghai normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:基于国内外有关地面太阳辐射研究,并根据中国大气气溶胶的有关研究,综合分析了近50年中国地面太阳辐射变化特征,并分析了我国各个地区、不同城市间地面太阳辐射的变化差异.结果表明:与全球大部分地区类似,中国的地面太阳辐射经历了一个从减少到增多的过程,即所谓的地球由"变暗"到"变亮";中国各个地区发生相同的变化过程,大致以 1990 年为界,之前以减少趋势为主,之后逐渐增加,不同地区太阳辐射变化幅度有所差异;分析了城市类型和气溶胶厚度对太阳辐射变化的影响,多数大城市和工业城市的太阳辐射下降幅度大于中小型非工业城市, 气溶胶光学厚度的分布与太阳辐射下降趋势呈相似分布特征,说明城市工业化及其产生的气溶胶污染对太阳辐射的下降起着重要作用. Abstract:Under the background of global warming, the gross radiation intensity on the ground changes obviously, most of Earth's surface energy is from solar, and the change of surface solar radiation could profoundly affect the global climate and eco-environment, thus the effects of the natural and human factors on solar radiation have become a hot issue. Based on the review of previous studies, this paper analyzed the long term variation characteristics of the surface solar radiation, using methods of a linear-trend estimation, regression analysis and correlation analysis, and analyzed the relationship between the surface solar radiation variations and the atmospheric aerosol distribution. The characteristics of variation and spatial distribution of surface solar radiation was analyzed during past nearly 50 years in China. The results showed as followed: (1) Similar with most parts of the world, China's surface solar radiation have experienced an earlier decreased and later raised process, which known as that the earth changed from ‘global dimming’ to ‘global brightening’; The surface solar radiation has been decreasing tendencies in recent 50 years in China, but the trends of surface solar radiation roughly divided into two phases in recent 50 years, the surface solar radiation and direct solar radiation had a decreasing trend over 1960-1990 and an increasing trend since 1991. The scattered radiation had a increasing trend over 1960-1990 and an decreasing trend since 1991. So in China, the reducing trend of surface solar radiation did not persist after the 1990, instead, an increasing trend had been observed since the late 1980s, and the trend and turning points of surface solar radiation in China are consistent with the global trend. (2) The relationships between city's industry type, city size and aerosol thickness distribution and surface solar radiation trends were analyzed. It showed that surface solar radiation declined more sharply in most big cities with intensive industry than the small or medium-sized city with less industry. In provincial capital, whether north or south of the Qinling Mountain-Huai River, the surface solar radiation of industrial cities had a decreasing tendency. The surface solar radiation in most of small cities showed insignificantly changing trends. It indicated that the change trend of surface solar radiation could be associated with air pollution in the process of quick urbanization and fast industrialization. On the whole, compared with south of Qinling Mountain-Huai River, the region in north of the Qinling Mountain-Huai River had a higher percentage of stations showed a downward trend. Compared with the small cities, the provincial capital cities had a higher percentage of the downward trend in surface solar radiation. As spatial variation, the surface solar radiation value is relatively higher in North China, Central China, Eastern China and South China, Sichuan basin, and relatively lower in other areas. The surface solar radiation in Eastern China, Central China and part of North China decreased even more sharply than west of China. Thicker aerosol optical depth was with larger trend of the surface solar radiation decrease, it indicated that aerosol pollution plays an important role in the decline of surface solar radiation. 参考文献 相似文献 引证文献

Characteristics of total solar radiation in an urban tropical environment

The maximum total solar radiation in Ibadan (7.38° N, 3.93° E), Nigeria occurred around 13 and 14 h local time (LT) and it varied from an average value of 584.3±10.9 Wm-2 in the wet season (April to October) to 642.5±10.8 Wm-2 in the dry season (November to March) throughout the period of 1997 to 2001. Maximum total solar radiation had two peaks, one in March/April/May with value 750.3±41 Wm-2 and the other in October/November with value 633.1±63.5 Wm-2. The minimum was in July/August with the value 404.8±54 Wm-2. Diurnal total solar radiation had a similar variation with mean day total solar radiation; the latter had its maxima and minimum values to be 564.7±19, 488±36 and 308.4±40 respectively. The annual trend of solar radiation was positive throughout the period considered, which revealed global brightening. The values of total solar radiation observed in Ibadan compared well with those obtained at Ife (7.55° N, 4.56° E) a nearby tropical station. A time lag of about 3 h between the peak of the diurnal temperature and solar radiation was observed. During the month of July or August as the case may be, there was little or no time lag between the time of maximum total solar radiation and maximum diurnal temperature. Significant intra-annual solar radiation cycles (at 0.05 significant level) of 360 to 370 days (1 per year); 180 to 200 days (2 per year), 90 to 121 days (3 per year), 45 to 70days (5 per year); 20 to 35 days (10 per year), 4 to 16 days (20 per year) were obtained for all the years (1997 to 2001). Key words: Total solar radiation, lag, intra-annual solar radiation cycles, global brightening.

Aerosol retrievals from channel-1 and -2 AVHRR radiances: Long-term trends updated and revisited

The nominal Global Aerosol Climatology Project (GACP) record of aerosol optical thickness (AOT) and Ångström exponent (AE) over the oceans is extended by 6 months to cover the period from August 1981 through December 2005. The most recent 4-year segment reveals no significant short-term tendencies in globally and hemispherically averaged AOTs and AEs. This finding is consistent with contemporaneous MODIS and MISR results and the accumulating evidence of a gradual transition from global brightening to global dimming. We also analyze the retrieval implications of allowing the imaginary part of the aerosols refractive index Im(m) to change over the duration of the GACP record. Our sensitivity study shows that increasing Im(m) from 0.003 during the 4-year pre-Pinatubo period up to 0.007 during the most recent 4-year segment of GACP data eliminates the previously identified long-term decreasing AOT trend. Should this long-term trend in Im(m) be real then it would cause the global absorption AOT over the oceans to more than double and the global single-scattering albedo to decrease from ∼0.95 to ∼0.88. Such changes could make tropospheric aerosols significant contributors to the recent surface temperature increase.

全天日射量の増加が伊勢湾での一次生産と貧酸素水塊に与える影響

The solar radiation has been increasing globally since the 1990s (global brightening). This is the first paper that examined the effect of increasing solar radiation on primary production and hypoxic water in coastal area. We performed a numerical experiment using 3D hydrodynamics and ecosystem model in Ise Bay, where the annual solar radiation had increased by 13.3% from 1980 to 2010. The model results reveal that both the annual mean primary production and the hypoxic water area decreased by reducing solar radiation (10%) from the 2010 level. Our results illustrate how elevating solar radiation influences the coastal environment, particularly hypoxic water area, by using the numerical experiment.

Observed Mass Balance of Mountain Glaciers and Greenland Ice Sheet in the 20th Century and the Present Trends

Glacier mass balance and secular changes in mountain glaciers and ice caps are evaluated from the annual net balance of 137 glaciers from 17 glacierized regions of the world. Further, the winter and summer balances for 35 glaciers in 11 glacierized regions are analyzed. The global means are calculated by weighting glacier and regional surface areas. The area-weighted global mean net balance for the period 1960–2000 is −270 ± 34 mm a−1 w.e. (water equivalent, in mm per year) or (−149 ± 19 km3 a−1 w.e.), with a winter balance of 890 ± 24 mm a−1 w.e. (490 ± 13 km3 a−1 w.e.) and a summer balance of −1,175 ± 24 mm a−1 w.e. (−647 ± 13 km3 a−1 w.e.). The linear-fitted global net balance is accelerating at a rate of −9 ± 2.1 mm a−2. The main driving force behind this change is the summer balance with an acceleration of −10 ± 2.0 mm a−2. The decadal balance, however, shows significant fluctuations: summer melt reached its peak around 1945, followed by a decrease. The negative trend in the annual net balance is interrupted by a period of stagnation from 1960s to 1980s. Some regions experienced a period of positive net balance during this time, for example, Europe. The balance has become strongly negative since the early 1990s. These decadal fluctuations correspond to periods of global dimming (for smaller melt) and global brightening (for larger melt). The total radiation at the surface changed as a result of an imbalance between steadily increasing greenhouse gases and fluctuating aerosol emissions. The mass balance of the Greenland ice sheet and the surrounding small glaciers, averaged for the period of 1950–2000, is negative at −74 ± 10 mm a−1 w.e. (−128 ± 18 km3 a−1 w.e.) with an accumulation of 297 ± 33 mm a−1 w.e. (519 ± 58 km3 a−1 w.e.), melt ablation −169 ± 18 mm a−1 w.e. (−296 ± 31 km3 a−1 w.e.), calving ablation −181 ± 19 mm a−1 w.e. (−316 ± 33 km3 a−1 w.e.) and the bottom melt-21 ± 2 mm a−1 w.e. (−35 ± 4 km3 a−1 w.e.). Almost half (−60 ± 3 km3 a−1) of the net mass loss comes from mountain glaciers and ice caps around the ice sheet. At present, it is difficult to detect any statistically significant trends for these components. The total mass balance of the Antarctic ice sheet is considered to be too premature to evaluate. The estimated sea-level contributions in the twentieth Century are 5.7 ± 0.5 cm by mountain glaciers and ice caps outside Antarctica, 1.9 ± 0.5 cm by the Greenland ice sheet, and 2 cm by ocean thermal expansion. The difference of 7 cm between these components and the estimated value with tide-gage networks (17 cm) must result from other sources such as the mass balance of glaciers of Antarctica, especially small glaciers separated from the ice sheet.

Long-term record and analysis of soil temperatures and soil heat fluxes in a grassland area, The Netherlands

A 27-year soil temperature record at five depths and soil heat flux record at one depth were analyzed for a grassland area in The Netherlands. The annual mean soil temperature of the last 23 years of soil measurements (no data gaps) showed a statistically significant increase of about 1.0 °C, consistent with the observed air temperature increase of about 1.3 °C for the same period. This positive trend correlates well with global brightening of 5.3 W m −2 per decade. The 10-day mean soil temperature varied smoothly throughout the year with relatively small inter-annual variability. The deeper the measurement depth, the smoother the annual cycle and the smaller the variability. In February and at the end of the year the variability appears to be somewhat larger. A Fast Fourier Transform was applied to the measurements and revealed an annual and daily damping depth of 1.80 m and 0.10 m, respectively. An example of the usefulness of this data is provided for agriculture, where an aggressive root-knot nematode is affected by the mean soil temperature increase. It appears that the 600 degree day life-cycle threshold is reached 16 days earlier, which may lead to a potential serious increase in agriculture crop damage.

Consistency of global satellite‐derived aerosol and cloud data sets with recent brightening observations

Solar radiation at the Earth surface has increased over land and ocean since about 1990 (‘global brightening’). An analysis of various global (ocean only) aerosol and (global) cloud data sets from geostationary and polar orbiting satellites is performed to determine whether changes in these quantities have occurred in accordance with ‘global brightening’, and to analyse the global distribution of these changes. Change‐point detection and trend analysis are employed in the analysis. In a period from the mid‐1980s to the mid‐2000s, aerosol optical depth is found to have started declining in the early 1990s, while cloud data sets do not agree on trends. Ångström exponent data seem to suggest changes in pollution.

Mass Balance of Glaciers and Ice Sheets during the Observational Period and Climate Change

Glacier mass balance and secular changes in mountain glaciers and ice caps are evaluated from the annual net balance of 161 glaciers from 17 glacierized regions of the world. Further, the annual net balance is split into winter and summer balances for 35 glaciers of 11 glacierized regions. The global means are calculated by weighting glacier and regional surface areas. The area-weighted global mean net balance for the period 1960 to 2000 is -250 mma-1w.e. (-138 km3a-1w.e.), with seasonal components of 1470 mma-1w.e. (810 km3a-1w.e.) for winter and -1725 mma-1w.e. (-950 km3a-1w.e.) for summer balances. The linear-fitted global net balance is accelerating at a rate of -11 mma-2. The main driving force behind this change is the summer balance with a rate of -12 mma-2. The decadal balance, however, shows significant fluctuations: melt reached its peak around 1945, followed by a decrease. The annual net balance, although negative for the global mean, approached equilibrium from the 1960s to 1980s. Some regions experienced a period of positive balance during this time, for example, Europe. The balance has become strongly negative since the early 1990s. These decadal changes correspond to periods of global dimming (for smaller melt) and global brightening (for larger melt). The total radiation at the surface changed as a result of an imbalance between steadily increasing greenhouse gases and fluctuating aerosol emissions. The mass balance of the Greenland ice sheet and the surrounding smaller glaciers is negative at -74 mma-1 with an accumulation of 297 mma-1w.e. (519 km3a-1w.e.), melt ablation -169 mma-1w.e. (-296 km3a-1w.e.), calving ablation -181 mma-1w.e. (-316 km3a-1 w.e.) and the bottom melt -21 mma-1w.e. (-35 km3a-1w.e.). At present, it is difficult to detect any statistically significant trends for these components. The total mass balance of the Antarctic ice sheet is considered to be too premature to evaluate. The estimated sea-level contributions in the 20th Century are 3.7 cm by mountain glaciers and ice caps, 3.5 cm by Greenland, 2 cm by ocean thermal expansion. The difference of 8 cm between these components and the estimated value with tide-gage networks (17 cm) must be caused by the mass balance of Antarctica and other sources that were not considered in the present work, for example, the melt of permafrost.

Temporal trend in anthropogenic sulfur aerosol transport from central and eastern Europe to Israel

Decrease of sulfur emissions in central and eastern Europe over the past 3 decades is well documented and linked to changes in economic activity, use of different fuels, addition of pollution controls, etc. These changes result in a decreasing trend of sulfate aerosol and aerosol forcing over the source region, but also at a receptor site located in southern Israel, thousands of kilometers downwind of the original source. A combination of several independent observations, namely, satellite and ground‐based remote sensing, in situ aerosol sampling, and backward trajectory analysis, was implemented to show significant downward trends in fine particle aerosol optical thickness (AOT), in general, and sulfur aerosol, in particular, between 1995 and 2007. For the study years, MODIS‐Terra observations over central and eastern Europe show 38% reduction of fine AOT. At the reception site in southern Israel, 43% reduction of fine AOT was observed by a ground‐based sun/sky photometer and 25% reduction of sampled fine aerosols was obtained. During the corresponding observation periods, the coarse mode AOT has remained constant. The majority of the backward trajectories, where meaningful sulfur events were observed at the receptor site, are originated from eastern and central Europe. The aerosol radiative effect at top of the atmosphere has become less negative during the past decade, decreasing by 30% in Europe and 67% in Israel. The decrease in negative cloud‐free aerosol forcing is consistent with observations of “global brightening” reported since 1990.

A NEW MINIMALLY INVASIVE TREATMENT FOR MALE STRESS URINARY INCONTINENCE: THE ADVANCE® MALE SLING, ONE YEAR DATA FROM A MULTICENTER PROSPECTIVE STUDY

The Cassini spacecraft Ultraviolet Imaging Spectrograph (UVIS) obtained observations of Jupiter's auroral emissions in H2 band systems and H Lyman-α from day 275 of 2000 (October 1), to day 81 of 2001 (March 22). Much of the globally integrated auroral variability measured with UVIS can be explained simply in terms of the rotation of Jupiter's main auroral arcs with the planet. These arcs were also imaged by the Space Telescope Imaging Spectrograph (STIS) on Hubble Space Telescope (HST). However, several brightening events were seen by UVIS in which the global auroral output increased by a factor of 2–4. These events persisted over a number of hours and in one case can clearly be tied to a large solar coronal mass ejection event. The auroral UV emissions from these bursts also correspond to hectometric radio emission (0.5–16 MHz) increases reported by the Galileo Plasma Wave Spectrometer (PWS) and Cassini Radio and Plasma Wave Spectrometer (RPWS) experiments. In general, the hectometric radio data vary differently with longitude than the UV data because of radio wave beaming effects. The 2 largest events in the UVIS data were on 2000 day 280 (October 6) and on 2000 days 325–326 (November 20–21). The global brightening events on November 20–21 are compared with corresponding data on the interplanetary magnetic field, solar wind conditions, and energetic particle environment. ACE (Advanced Composition Explorer) solar wind data was numerically propagated from the Earth to Jupiter with an MHD code and compared to the observed event. A second class of brief auroral brightening events seen in HST (and probably UVIS) data that last for ∼2 min is associated with auroral flares inside the main auroral ovals. On January 8, 2001, from 18:45–19:35 UT UVIS H2 band emissions from the north polar region varied quasiperiodically. The varying emissions, probably due to auroral flares inside the main auroral oval, are correlated with low-frequency quasiperiodic radio bursts in the 0.6–5 kHz Galileo PWS data.

Global dimming and global brightening—an analysis of surface radiation and cloud cover data in northern Europe

AbstractIn the present study, surface solar radiation data from 11 stations in northwestern Europe and the European Arctic are presented in the context of the ongoing discussion on global dimming and global brightening. The surface solar radiation records are compared to records of cloud cover, and to qualitative information on aerosol concentrations and atmospheric circulation patterns, in order to explain the temporal variations.Through simple statistical analyses, we examine annual trends as well as trends for individual months, and compare the results between the stations. Comparisons are also made between different time periods within the records. We find that surface solar radiation changes in the region considered, even at the remote arctic stations, correspond well with trends found in global studies, with a significant decrease from the 1950s to the 1980s, followed by a slight increase in recent years. At stations that stand out from the general pattern, the deviations can be explained by variations in cloud cover in most cases.There has been a general tendency to attribute the majority of the observed surface solar radiation trends to aerosol changes caused by changes in anthropogenic emissions. This study stresses the importance of the contribution of clouds and the atmospheric circulation to global dimming and global brightening. Copyright © 2008 Royal Meteorological Society

Long-term solar UV radiation reconstructed by ANN modelling with emphasis on spatial characteristics of input data

Abstract. Artificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Special emphasis will be given to the discussion of small-scale characteristics of input data to the ANN model. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980/1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions.

Multi year changes of Aerosol Optical Depth in the monsoon region of the Indian Ocean since 1986 as seen in the AVHRR and TOMS data

Abstract. Aerosol Optical Depth (AOD) data based on AVHRR and TOMS was analyzed to find out the changes in the Indian Ocean from 1981 to 2004. Four regions covering Indian Ocean north of 10° S were studied in detail. The results strongly suggest that the mean value of AOD in these regions decreased from 1986–1990 to 1995–1999. The Arabian Sea and Bay of Bengal show increase thereafter whereas in the equatorial part it decreased further, during 2000–2004. The drop in AOD from the first to second period is evident in AVHRR and TOMS in the case of the Arabian Sea (North West Indian Ocean). The decrease in this case is prominent in summer. These results in general agree with the recently reported global decrease in AOD, "global brightening" and also the reversal of trend in some of the anthropogenic emissions.

Comment on “A perspective on global warming, dimming, and brightening”

In his 30 January 2007 Eos Forum article, Stanhill [2007] writes about “…the challenge that recently reported changes in solar radiation at the Earth's surface…pose to the consensus explanation of climate change,” referring to the “consensus” assessment reports of the Intergovernmental Panel on Climate Change. Here we offer an alternative perspective on this issue.

Human Impact on Direct and Diffuse Solar Radiation during the Industrial Era

AbstractIn this study the direct and diffuse solar radiation changes are estimated, and they contribute to the understanding of the observed global dimming and the more recent global brightening during the industrial era. Using a multistream radiative transfer model, the authors calculate the impact of changes in ozone, NO2, water vapor, CH4, CO2, direct and indirect aerosol effects, contrails, and aviation-induced cirrus on solar irradiances at the surface. The results show that dimming is most pronounced in central Africa, Southeast Asia, Europe, and northeast America. Human activity during the industrial era is calculated and accounts for a decrease in direct solar radiation at the surface of up to 30 W m−2 (30%–40%) and an increase in diffuse solar radiation of up to 20 W m−2. The physical processes that lead to the changes in direct and diffuse solar radiation are found to be remarkably different and the authors explain which mechanisms are responsible for the observed changes.

Long-term change of mass balance and the role of radiation

AbstractThe effect of climate change in the 20th century is investigated based on measured mass-balance data. Annual, winter and summer mass balances on Claridenfirn, Switzerland, (since 1914/15) Storglaciären, Sweden, (since 1945/46) Storbreen, Norway, (since 1948/49) Glacier de Sarennes, France, (since 1948/49) and Vernagtferner, Austria, (since 1965/66) are studied with air temperature at high-altitude stations and the longest records of solar global radiation in Europe. The mean mass balances of these glaciers during the 20th century were mostly negative except for the first two decades. The fluctuating mass balance reaches the minimum (largest loss) and maximum (almost equilibrium) around 1940 and 1980, respectively, with a drastic loss in the last 15 years. These variations are mostly steered by the variation in summer mass balance. The change in the summer mass balance is determined to 72% by temperature and the remaining 28% by solar radiation. During the colder period (e.g. 1960–80), the reduction in solar radiation counteracted the warming trend due to the greenhouse effect. Since 1990 the greenhouse effect of terrestrial radiation and the global brightening effect of solar radiation have both been acting to accelerate the melt, resulting in the unprecedented mass loss of the observational era. The glacier mass balance during the 20th century clearly reacted towards temperature and solar radiation changes, which reflected the greenhouse effect and aerosol and cloud variations.

Cassini UVIS observations of Jupiter's auroral variability

The Cassini spacecraft Ultraviolet Imaging Spectrograph (UVIS) obtained observations of Jupiter's auroral emissions in H 2 band systems and H Lyman- α from day 275 of 2000 (October 1), to day 81 of 2001 (March 22). Much of the globally integrated auroral variability measured with UVIS can be explained simply in terms of the rotation of Jupiter's main auroral arcs with the planet. These arcs were also imaged by the Space Telescope Imaging Spectrograph (STIS) on Hubble Space Telescope (HST). However, several brightening events were seen by UVIS in which the global auroral output increased by a factor of 2–4. These events persisted over a number of hours and in one case can clearly be tied to a large solar coronal mass ejection event. The auroral UV emissions from these bursts also correspond to hectometric radio emission (0.5–16 MHz) increases reported by the Galileo Plasma Wave Spectrometer (PWS) and Cassini Radio and Plasma Wave Spectrometer (RPWS) experiments. In general, the hectometric radio data vary differently with longitude than the UV data because of radio wave beaming effects. The 2 largest events in the UVIS data were on 2000 day 280 (October 6) and on 2000 days 325–326 (November 20–21). The global brightening events on November 20–21 are compared with corresponding data on the interplanetary magnetic field, solar wind conditions, and energetic particle environment. ACE (Advanced Composition Explorer) solar wind data was numerically propagated from the Earth to Jupiter with an MHD code and compared to the observed event. A second class of brief auroral brightening events seen in HST (and probably UVIS) data that last for ∼2 min is associated with auroral flares inside the main auroral ovals. On January 8, 2001, from 18:45–19:35 UT UVIS H 2 band emissions from the north polar region varied quasiperiodically. The varying emissions, probably due to auroral flares inside the main auroral oval, are correlated with low-frequency quasiperiodic radio bursts in the 0.6–5 kHz Galileo PWS data.