Decrease In Sunshine Duration Research Articles

Interactive effects of ambient air pollution and sunshine duration on the risk of intrahepatic cholestasis of pregnancy

IntroductionWhile the associations among ambient pollutants and various pregnancy complications are well documented, the effect of ambient pollutants on intrahepatic cholestasis of pregnancy (ICP) has not been examined. This study aimed to explore the effects of ambient pollutants and sunshine duration on ICP. MethodsThe study enrolled 169,971 pregnant women who delivered between 2015 and 2020 in two hospitals. The associations between ICP and exposure to ambient pollutants and sunshine duration, averaged throughout different periods (including the 3 months before conception, 1st trimester and 2nd trimester), were estimated using a generalized linear model. The interaction effects of ambient pollutants and sunshine duration on ICP were estimated. ResultsThe fitted curves for ICP incidence were similar to the temporal trends of PM2.5, PM10, SO2, CO and NO2 but not that of O3. The risk of ICP was significantly elevated following a 10-μg/m3 increase in PM2.5 (aOR [adjusted odds ratio] = 1.057, 95% CI [confidence interval]: 1.017–1.099) and PM10 (aOR = 1.043, 95% CI: 1.013–1.074) and a 1-h decrease in sunshine duration (aOR = 1.039, 95% CI: 1.011–1.068) during the 3 months before conception. In the second trimester, a 1-μg/m3 increase in the concentration of SO2 was associated with an increased risk of ICP (aOR = 1.011, 95% CI: 1.001–1.021). Increased concentrations of PM2.5 and PM10 had interactive effects with reduced sunshine duration during the 3 months before conception on increasing the risk of ICP. ConclusionsExposure to PM2.5 and PM10 during the 3 months before conception and exposure to SO2 in the second trimester were associated with an increased ICP risk. Reduced sunshine duration had an interactive effect with increased concentrations of PM2.5 and PM10 during the 3 months before conception on the occurrence of ICP.

Spatiotemporal pattern of reference crop evapotranspiration and its response to meteorological factors in Northwest China over years 2000-2019.

Agricultural irrigation water in Northwest China accounts for more than 80% of total local water consumption, which is 1.23 times that of China. However, Northwest China is the most water-scarce place in China. Water scarcity in restricts crop growth and production. Reference crop evapotranspiration (ET0) is important for agricultural water management. Understanding the reason for ET0 change is helpful to provide a basis for rational planning of agricultural irrigation systems to conserve water. This study investigated the temporal and spatial variation characteristics of ET0 at 181 meteorological stations in Northwest China from 2000 to 2019. And the sensitive factors and dominant factors affecting ET0 change were quantitatively identified based on sensitivity analysis and contribution rate evaluation. Results showed that (1) a significant increase in maximum and minimum temperature (Tmax and Tmin), a significant decrease in sunshine duration (SD) and relative humidity (RH), and a slight increase in wind speed at 10m height (U10) were observed. (2) Annual ET0 had an insignificant increasing trend. Spring and autumn ET0 contributed greatly to the growth of annual ET0, especially in March, May, September, October, and November. ET0 in HH (Yellow River Basin area) had decreased at annual scale, while other subregions were the opposite trend. Significant differences in monthly and seasonal changes in the spatial distribution of ET0. (3) U10 was the dominating contribution factor related to annual ET0 variability, followed by Tmin, RH, Tmax, and SD. In seasonal time scale, Tmin, SD, U10, and RH were the most dominant factors in spring, summer, autumn, and winter respectively. (4) Spatial distribution for contribution rates of various meteorological factors showed significant diversity among various subregions. The positive contribution of U10 was the major cause of the increase in ET0 in semi-arid grassland area (BGH), the southwest of "Qice line" (QCXXN), and the southeast of "Qice line" (QCXDN); the significant increase in Tmin contributed most in Qaidam Basin (CDM), Hexi inland river basin (HX), the northeast of "Qice line" (QCXDB), and the northwest of "Qice line" (QCXXB), while the contribution of decreasing SD offsets the positive effects of other factors, leading to the decrease in ET0 in HH. Our work illustrates that water management measures should be different at different spatial and temporal scales. The effect of U10 can be offset by covering, to reduce evaporation and maintain water in BGH, QCXXN, and QCXDN. And high-temperature resistant varieties are planted to adapt to temperature growth in CDM, HX, QCXDB, and QCXXB. Agricultural water management strategies should be formulated and selected according to local conditions.

Spatial-temporal variations of terrestrial evapotranspiration across China from 2000 to 2019

Terrestrial evapotranspiration (ET) refers to a key process in the hydrological cycle by which water is transferred from the Earth's surface to lower atmosphere. With spatiotemporal variations, ET plays a crucial role in the global ecosystem and affects vegetation distribution and productivity, climate, and water resources. China features a complex, diverse natural environment, leading to high spatiotemporal heterogeneity in ET and climatic variables. However, past and future ET trends in China remain largely unexplored. Thus, by using MOD16 products and meteorological datasets, this study examined the spatiotemporal variations of ET in China from 2000 to 2019 and analyzed what is behind changes, and explored future ET trends. Climate variation in China from 2000 to 2019 was statistically significant and had a remarkable impact on ET. Average annual ET increased at a rate of 5.3746 mm yr−1 (P < 0.01) during the study period. The main drivers of the trend are increasing precipitation and wind speed. The increase in ET can also be explained to some extent by increasing temperature, decreasing sunshine duration and relative humidity. The zonation results show that the increase in temperature, wind speed, and precipitation and the decrease in relative humidity had large and positive effects on ET growth, and the decrease in sunshine duration had either promoting or inhibiting effects in different agricultural regions. Pixel-based variations in ET exhibited an overall increasing trend and obvious spatial volatility. The Hurst exponent indicates that the future trend of ET in China is characterized by significant anti-persistence, with widely distributed areas expected to experience a decline in ET. These findings improve the understanding of the role of climate variability in hydrological processes, and the ET variability in question will ultimately affect the climate system.

Early sunshine duration and cloud cover records in Coimbra (Portugal) for the period 1891–1950

AbstractThe recovery of early sunshine duration (SD) records is crucial to improve knowledge of the long‐term evolution of incoming solar radiation at the Earth's surface. This work analyses daily SD data digitized from the Meteorological Observatory of Coimbra (Portugal) during 1891–1950. The Coimbra SD records are the earliest series in Portugal and the second one in the whole Iberian Peninsula (i.e., the first being in Madrid, Spain). The analysis shows that SD time series is homogenous except for a break in 1937–1938, which may be likely related to a change of the SD recorder (i.e., Jordan device replaced by a Campbell‐Stokes recorder). Once the temporal inhomogeneity has been corrected, a slightly negative trend of −0.09 ± 0.06 hr per decade is found for the whole 1891–1950 period. It must be highlighted the marked decrease in SD records of −0.51 ± 0.32 hr per decade observed from the beginning of the time series until the 1910s (‘early dimming’) in line with other studies available in the literature. Both trends (whole and ‘early dimming’ periods) are statistically significant at the 95% confidence level. By contrast, from 1920s until 1950 no statistically significant long‐term changes in SD records are found. Additionally, cloud cover data in Coimbra have been also digitized and analysed for the common period. A positive statistically significant trend of 0.13 ± 0.06 tenths per decade is found for the 1891–1950 period which may explain the negative trend of SD records in this same period. Nevertheless, the analysis of SD long‐term trends under cloudless conditions suggests that other atmospheric factors such as the aerosol load could likely also play a relevant role on the SD evolution. The SD and cloud cover data from 1891 to 1950 is made available for the scientific community in digital form.

Spatiotemporal trends in reference evapotranspiration and its driving factors in Bangladesh

This research investigates spatiotemporal variations in ETo and the controlling factor of those variations using the modified Mann-Kendall test, empirical Bayesian kriging model, Morlet wavelet analysis (MWA), and cross-wavelet transform (XWT) model relying on daily climate data sets obtained from 18 meteorological stations for the period 1980–2017. Additionally, the stepwise linear regression analysis and partial correlation coefficient (PCC) were employed to determine the variables driving the changes in ETo. The investigation exhibited a decline in annual for −1.19 mm year−1 and seasonal (−0.40 mm decade−1 during pre-monsoon, −0.47 mm decade−1 during post-monsoon, −0.50 mm decade−1 during winter) ETo, which indicates the existence of “evapotranspiration paradox” in Bangladesh, similar to many regions across the globe. The trend test depicted that despite the increase in mean temperature (MT), a noteworthy decrease in sunshine duration (SD), and wind speed (WS) are the main reasons for the reduction in ETo. Spatial analysis of ETo revealed the highest annual values in the southwest while the lowest in the northwest. Two cycles, 1–3 and 3–5 years were found significant in the annual and seasonal ETo. The outcomes revealed coherence among ETo with meteorological factors at different time-frequency bands, which is noteworthy. Stepwise regression and PCC showed that the impact of meteorological factors on ETo varies on the annual and seasonal scales where MT, RH, and SD are the major factors responsible for the variations of ETo in both annual and seasonal scales. These outcomes of the research can be advantageous for designing irrigation and management of sustainable water resources to mitigate climate change impacts as well as controlling anthropogenic activities.

Reduction in Sunshine Duration and Related Factors over Mainland China during 1961–2016

As a kind of renewable energy, the development and utilization of solar energy is valued by many countries. Sunshine duration (SD), as an important factor to measure solar energy, has also been widely discussed as relevant in terms of distribution and variation. The spatial patterns and variation trends in SD and related factors (wind speed, precipitation, relative humidity, mean temperature and elevation) over mainland China have been studied based on data from 569 meteorological stations during 1961–2016. The results indicated that annual SD decreased significantly at the rate of −40.7 h/10a over mainland China and the decline trend was the most pronounced in the 1980s. Seasonally, the decline rate in SD was the largest in summer (−16.8 h/10a), followed by winter (−9.9 h/10a), autumn (−9.5 h/10a) and spring (−4.5 h/10a), respectively. Spatially, the decline trend in SD was significantly higher in the eastern region than in the western region during 1961–2016, especially in North China. SD was positively correlated with wind speed (R = 0.76); however, it was negatively correlated with mean temperature (R = −0.60) and precipitation (R = −0.41). Moreover, altitude and population density may affect the values and variations of annual SD over mainland China. This study provides a new perspective for the reduction of SD in mainland of China. The drastic changes in SD, such as abrupt changes and sudden decreases, were closely related to volcanic eruptions. Among them, the mean mutation and sudden decrease of SD in the 1980s were due to the long-time weakening of the aerosol accumulated by multiple volcanic eruptions. After the volcanic eruptions in the early 1990s, volcanic aerosols were gradually dissipating, resulting in a small rebound in SD.

Effects of urbanization on the decrease in sunshine duration over eastern China

As an important indicator of sunlight conditions, sunshine duration (SSD) has a close relationship with human health, socio-economic activity, ecosystems, and the environment. This paper examines the long-term changes in SSD over eastern China and evaluates the possible urbanization effect on these changes based on a dynamic classification of urban and rural stations using time-varying land use/land cover maps. Daily SSD observations at nearly 2000 stations during 1961–2014 are collected and analyzed. Results show that SSD in eastern China declines throughout the year at an annual rate of −0.132 h/day per decade, with the largest trend in summer (i.e., −0.218 h/day per decade) and most moderate in spring (−0.066 h/day per decade). The dimming trend is even more profound in the highly urbanized and densely populated areas, such as the North China Plain and the Yangtze River Delta. A significant correlation of −0.48 also exists in the SSD trend and urban area fraction around the station. These results demonstrate an essential influence of local urbanization on SSD changes. It is also estimated that urbanization induces an additional decreasing trend of 0.065 h/day per decade for SSD, contributing to 35.3% of the total dimming trend in eastern China.

Climatology and trends of air and soil surface temperatures in the temperate steppe region of North China

ABSTRACTWe analysed observations of daily maximum and minimum air and soil surface temperatures collected between 1965 and 2007 in the temperate steppe region of North China to understand the climatology and trends of the diurnal temperature range. Sunshine duration and precipitation records were also analysed for their relationships with the changes in temperatures. In general, the daily maximum soil surface temperatures (SSTmax) are generally much higher than the daily maximum air temperature (Tmax), and the daily minimum soil surface temperature (SSTmin) are slightly lower than the daily minimum air temperature (Tmin) throughout the year. Consequently, the soil surface diurnal temperature range (SSDTR) is much higher than diurnal temperature range of air temperatures (DTR). As with air temperatures, soil surface temperatures have warmed significantly over the study period at most stations, increasing by 0.62 °C per decade for SSTmax and 0.64 °C per decade for SSTmin for the region overall. Annual and seasonal SSTmax and SSTmin have increased faster than Tmax and Tmin, except for SSTmax in winter. Declines in air DTR have been commonly observed, but in our study SSDTR decreases only in winter, driven by a steep decline after 2000, mostly resulting from strong increases in SSTmin and slight decreases in SSTmax. Both annual and seasonal calculations indicate that the decline in air DTR mainly coincided with a period of rapid decrease in sunshine duration before 1990. Total cloud amount decreased during this period, so the changes in total cloud amount could not be the cause for decrease in sunshine duration and DTR before 1990. SSDTR shows a different pattern: the rapid decrease of SSDTR in winter season since the end of 1990 coincides with a decrease in sunshine duration and an increase in total cloud amount, which may have contributed to the decrease in winter SSDTR in the new millennium.

Evaluation of recent hydro-climatic changes in four tributaries of the Niger River Basin (West Africa)

ABSTRACTWest Africa experienced severe drought during the 1970s and 1980s, posing a threat to water resources. A wetter climate more recently suggests recovery from the drought. The Mann-Kendall trend and Theil-Sen’s slope estimator were applied to detect probable trends in weather elements in four sub-basins of the Niger River Basin between 1970 and 2010. The cross-entropy method was used to detect breakpoints in rainfall and runoff, Spearman’s rank test for correlation between the two, and cross-correlation analysis for possible lags. Results showed an overall increase in rainfall and runoff and a decrease in sunshine duration. Spearman’s coefficients suggest significant (5%) moderate to strong rainfall–runoff correlation for three sub-basins. A significant lower runoff was observed around 1979, with a rainfall break around 1992, indicating possible cessation of the drought. Temperatures increased significantly, at 0.02–0.05°C year-1, with a negative wind speed trend for most stations. Half of the stations exhibited an increase in potential evapotranspiration.EDITOR M.C. AcremanASSOCIATE EDITOR Not assigned

Aerosols over continental Portugal (1978–1993): their sources and an impact on the regional climate

Abstract. Understanding of aerosol sources that affect climate is an ongoing problem facing scientists as well as policymakers. The role of aerosols in local climate variability depends on a balance between light absorbing and scattering particles as well as on variability of environmental conditions. In this paper we investigate variability of aerosol content (both absorbing and scattering ultraviolet radiation) over continental Portugal in connection with aerosol sources (volcanic eruptions, dust events, wildfires and anthropogenic pollution). The effect of the aerosol on the climate is studied analyzing their contribution to variations of temperature, pressure, sunshine duration and precipitation over Portuguese regions. The present analysis is based on a developed modern multiple regression technique allowing us to build the statistical correlation models to determine both the main local aerosol sources and aerosol's influence on the climate of continental Portugal during 1978–1993. The analysis allows us to conclude that the main sources driving the variations of the aerosol content over studied locations are wildfires, mineral dust intrusions and anthropogenic pollution. The relations between the aerosol content variations and the atmospheric parameters depend on the level of urbanization of the studied region, the type of aerosol and the season. The most significant finding is the decrease of the daily maximum temperature (and diurnal temperature range) related to the decrease of sunshine duration observed during the summer periods of increased content of the absorbing aerosols in the atmosphere.

NDVI and vegetation phenology dynamics under the influence of sunshine duration on the Tibetan plateau

ABSTRACTClimate change has significantly influenced vegetation dynamics on the Tibetan Plateau (TP). Past research mainly focused on vegetation responses to temperature variation and water stress, but the influence of sunshine duration on NDVI and vegetation phenology on the TP is not well understood. In this study, NDVI time series from 1982–2008 were used to retrieve spatiotemporal vegetation dynamics on the TP. Empirical orthogonal function (EOF) analysis was conducted to understand the spatiotemporal variations of NDVI. The Start of Season (SOS) was estimated from NDVI time series with a local threshold method. The first EOF, accounting for 35.1% of NDVI variations on the TP, indicates that NDVI variations are larger in areas with shorter sunshine duration. The needle‐leaved forest and shrub in the southeastern TP are more sensitive to sunshine duration anomalies (p &lt; 0.01) than broad‐leaved forest, steppe, and meadow due to spatial and altitudinal distribution of sunshine duration and vegetation types. The decrease in sunshine duration for the growing season on the TP has resulted in a decreased NDVI trend in some areas of southeastern TP (p ranging from 0.32‐0.05 with threshold ranging from 0.05 to 0.25) in spite of the overall NDVI increase. SOS dynamics in most parts of the TP were mainly related to temperature variability, with precipitation and sunshine duration playing a role in a few regions. This study enhances our understanding of vegetation responses to climatic change on the TP.

Decadal variability of clouds, solar radiation and temperature at a high-latitude coastal site in Norway

The observed variability of shortwave (SW) irradiance, clouds and temperature and the potential connections between them is studied for the subarctic site Bergen (60.4°N, 5.3°E), located on the Norwegian west coast. Focusing on the quality and spatial representativity of the data, we compare observations from independent instruments and neighbouring measurement sites. The observations indicate that the decrease of sunshine duration and SW irradiance during the 1970s and 80s in Bergen is associated with the increasing frequency of clouds, in particular clouds of low base heights. We argue that the observed cloud changes are indicative of increased frequencies of storms in northern Europe. The annual mean observational time series show an increase in SW irradiance since 1990, which is not accompanied by a cloud cover (NN) decrease. This implies the influence of factors other than clouds, for example, decreasing aerosol emissions. Calculations of the aerosol optical depth (AOD) based on irradiance observations for hours when the sun is unobscured by clouds confirm a decreasing aerosol load after 1990, from 0.15 to 0.10 AOD which corresponds to 2–6 Wm−2 of brightening. At the same time, a seasonal analysis reveals opposite changes in SW irradiance and NN during the months of strongest changes – March, April and August – also during the recent period of increasing SW irradiance. We conclude that the seasonally decreasing NN also contributes to the recent changes in SW irradiance. Finally, we address the relationship between temperature, SW irradiance and clouds. In winter (December–February), the surface air temperature in Bergen is statistically linked to the warming influence of clouds. In all other seasons, the North Atlantic sea surface temperature variability has a more dominant influence on the air temperature in Bergen compared to local cloud and SW irradiance variability.

Changes in Climate Factors and Extreme Climate Events in South China during 1961–2010

Daily climate data at 110 stations during 1961–2010 were selected to examine the changing characteristics of climate factors and extreme climate events in South China. The annual mean surface air temperature has increased significantly by 0.16°C per decade, most notably in the Pearl River Delta and in winter. The increase rate of the annual extreme minimum temperature (0.48°C per decade) is over twice that of the annual extreme maximum temperature (0.20°C per decade), and the increase of the mean temperature is mainly the result of the increase of the extreme minimum temperature. The increase rate of high-temperature days (1.1 d per decade) is close to the decrease rate of low-temperature days (–1.3 d per decade). The rainfall has not shown any significant trend, but the number of rainy days has decreased and the rain intensity has increased. The regional mean sunshine duration has a significant decreasing trend of –40.9 h per decade, and the number of hazy days has a significant increasing trend of 6.3 d per decade. The decrease of sunshine duration is mainly caused by the increase of total cloud, not by the increase of hazy days in South China. Both the regional mean pan evaporation and mean wind speed have significant decreasing trends of –65.9 mm per decade and –0.11 m s−1per decade, respectively. The decrease of both sunshine duration and mean wind speed plays an important role in the decrease of pan evaporation. The number of landing tropical cyclones has an insignificant decreasing trend of –0.6 per decade, but their intensities show a weak increasing trend. The formation location of tropical cyclones landing in South China has converged towards 10–19°N, and the landing position has shown a northward trend. The date of the first landfall tropical cyclone postpones 1.8 d per decade, and the date of the last landfall advances 3.6 d per decade, resulting in reduction of the typhoon season by 5.4 d per decade. CitationDu, Y.-D., H. Ai, H.-L. Duan, et al., 2013: Changes in climate factors and extreme climate events in South China during 1961–2010. Adv. Clim. Change Res.,4(1), doi: 10.3724/SP.J.1248.2013.001. Editor’s notesThe Working Group (WG) Reports and Synthesis Report of the IPCC Fifth Assessment Report (AR5) will be completed in 2013/2014. In order to address climate change, China Meteorological Administration (CMA) has launched climate change assessment reports since August 2008 for East China, South China, Central China, North China, Northeast China, Northwest China, Southwest China, and Xinjiang Uygur autonomous region. This is the first effort addressing climate change at a regional scale in China and among the first efforts globally. In order to ensure the quality of the report, CMA has organized hundreds of experts from CMA, colleges and universities, and the Chinese Academy of Sciences, and used a workflow similar to that of the IPCC AR5. The methods of field observation, data analysis, forecasting models and literature review have been used in these reports. Until now, eight regional assessment reports are being published. This journal will continuously publish the studies in three repeating sessions: climate change facts, impact assessment and adaptation, and mitigation, in order to provide the readers with this reference.

Trends in Annual and Seasonal Pan Evaporation in the Lower Yellow River Basin from 1961 to 2010

The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961–2010 are analyzed. The causes for the changes in annual and seasonal pan evaporation are also discussed. The results suggest that, despite the 1.15°C increasing in annual mean surface air temperature over the past 50 years (0.23°C per decade), the annual pan evaporation has steadily declined by an average rate of −7.65 mm per year. By comparison, this change is greater than those previously reported in China. Significant decreasing trends in annual pan evaporation have been observed at almost all stations. As a whole, seasonal pan evaporation decreased significantly, especially in summer, whereas seasonal temperature increased significantly, except in summer. Thus, the pan evaporation paradox exists in the lower Yellow River Basin. The trend analysis of other meteorological factors indicates significant decrease in sunshine duration and wind speed, but no significant variations in precipitation and relative humidity at annual and seasonal time scales. By examining the relationship between precipitation and pan evaporation, it did not show a concurrent decrease in pan evaporation and increase in precipitation. The partial correlation analysis discovered that the primary cause of decrease in annual and seasonal pan evaporation is the decrease in wind speed. A further examination using a stepwise regression shows that decrease in wind speed and sunshine duration, and increase in mean temperature are likely to be the main meteorological factors affecting the annual and seasonal pan evaporation in the lower Yellow River Basin over the past 50 years. CitationJi, X.-J., J.-J. Wang, W.-L. Gu, et al., 2012: Trends in annual and seasonal pan evaporation in the lower Yellow River Basin from 1961 to 2010. Adv. Clim. Change Res.,3(4), doi: 10.3724/SP.J.1248.2012.00195.

Evaluation of long‐term changes of solar radiation in India

AbstractTemporal and spatial variability in annually averaged global irradiance, diffuse irradiance, and bright sunshine duration over twelve stations of solar radiation network of India Meteorological Department (IMD) were evaluated for the period 1971–2005. Annually averaged all‐sky global irradiance decreased between 0.1% (0.3 Wm−2) and 3.6% (9.0 Wm−2) per decade at the stations. The decrease in sunshine duration was concomitant with the decrease in global solar irradiance. The long‐term trends in diffuse irradiance differed markedly between the twelve stations. Significant increasing trend in diffuse irradiance were found at the four stations under all‐sky conditions, while seven stations showed increasing trend under clear sky conditions. The two most probable causes of long‐term trends in radiation are changes in aerosol loading and cloud cover. Trend analyses of Angstrom's turbidity coefficient measured at three stations of IMD during the last three decades indicate that total column aerosol has increased significantly. Trend analysis of bright sunshine duration suggests long‐term decrease at all the stations. Reduction in bright sunshine hours varied from 0.0 to 0.5 h per decade. There is a strong northwest‐northeast gradient in sunshine duration which contributes to the spatial trends in global and diffuse solar irradiance. This paper examines the trends of global irradiance, diffuse irradiance and sunshine duration over India in all‐sky conditions as well as cloud‐free skies so the effect of cloud cover can be examined. Copyright © 2011 Royal Meteorological Society

Trend in pan evaporation and its attribution over the past 50 years in China

Trends in pan evaporation are widely relevant to the hydrological community as indicators of hydrological and climate change. Pan evaporation has been decreasing in the past few decades over many large areas with differing climates globally. This study analyzes pan evaporation data from 671 stations in China over the past 50 years in order to reveal the trends of it and the corresponding trend attribution. Mann-Kendall test shows a significant declining trend in pan evaporation for most stations, with an average decrease of 17.2 mm/10a in China as a whole, the rate of decline was the steepest in the humid region (29.7 mm/10a), and was 17.6 mm/10a and 5.5 mm/10a in the semi-humid/semi-arid region and arid region, respectively. Complete correlation coefficients of pan evaporation with 7 climate factors were computed, and decreases in diurnal temperature range (DTR), SD (sunshine duration) and wind speed were found to be the main attributing factors in the pan evaporation declines. Decrease in DTR and SD may relate to the increase of clouds and aerosol as well as the other pollutants, and decrease in wind speed to weakening of the Asian winter and summer monsoons under global climate warming.

Sunshine duration climatology and trends in association with other climatic factors over India for 1970-2006

Changes in sunshine duration in association with total cloud amount, rainy days and good visibility days over India were examined for 1970-2006. Climatologically, annual total sunshine duration over west Rajasthan and adjoining Gujarat is more than 3100 hours which is ideal for harnessing solar energy over these regions. The trend analysis indicates significant decrease in sunshine duration over the country for all months (except June) and the maximum decrease has taken place in January (-0.44 hour/decade) followed by December (-0.39 hour/decade). Seasonally, decline in sunshine hours is highest in winter and post monsoon (4% per decade) and lowest in monsoon (3% per decade). Decadal variations indicate maximum decrease in sunshine over the Indo-Gangetic plains and south peninsula during 1990-1999. Spatially, the decreasing trends in sunshine hours are highest in Indo-Gangetic plains and south peninsula while regions over Rajasthan and Gujarat have lowest decrease. Out of 40 stations under study, the maximum decrease in sunshine has occurred at New Delhi (winter at 13% per decade and post monsoon at 10% per decade) and Varanasi (summer and monsoon at 7% per decade). Correlation analysis of sunshine duration with total cloud amount, rainy days and good visibility days indicates regional and seasonal variations in factors explaining the long term trends in sunshine duration over the country.

The Implication of Heat and Water Balance Changes in a Lake Basin on the Tibetan Plateau

The numerous lakes found throughout the Tibetan Plateau have a large effect on evaporation from the plateau. We analyzed variation in the water cycle in Yamdrok Yumtso Lake basin under the temperature increase of 1.13°C during the 45 years from 1961�2005. Both vapor pressure and relative humidity increased by approximately 17%, resulting in a 13.7% increase in longwave radiation flux and a smaller daily range of surface air temperature. A 5.7% decrease in sunshine duration caused solar radiation flux to decrease by 3%. Heat and water balances were simulated over land and the lake. The lake covers 10% of the total basin area. Evaporation from the lake was larger than that from land, with lake evaporation making up 26% of the basin total. Evaporation from the lake decreased 7% (May� September) over the study period, and observed small pan evaporation also decreased. This trend was not found in the evaporation from land and from precipitation. With water vapor in the air increasing and evaporation from the ground surface (lake and land) decreasing, the water vapor may have come from areas outside the basin and possibly even beyond the plateau.

Characteristics of climate change in the “significant impact zone” affected by aerosols over eastern China in warm seasons

Through analysis of the distribution pattern and changing characteristics of atmospheric aerosols over the East Asia region during warm seasons in recent 20 a and beyond as well as their possible interactive relationship with a variety of meteorological elements, it is found that the high-value zone of aerosol optical depth derived from the Total Ozone Mapping Spectrometer (TOMS), its significant negative correlation zones in terms of sunshine duration (SD) and surface air temperature (SAT) and its significant positive correlation zones with low-level cloud amount (LCC) are co-located in the South China region during warm periods. Based on this finding, the region is referred to as a “significant impact zone” (SI zone) affected by aerosols. Then, a comparative analysis is made on variation differences of observed SAT, SD and LCC, etc. in different regions. It is also found that the LCC is increased and the SD is decreased within the “SI zone” over eastern China during the warm season. These characteristics are more evident than those beyond the zone, while the warming trend within the zone is evidently weaker than that outside it. Studies show that since recent 20 a, under the influence of aerosols, the LCC tend to increase substantially with a clear decrease of SD and an unnoticeable warming trend within the “SI zone”. Comparing with the climate change beyond the zone, the difference is significant. Therefore, the effects of atmospheric aerosols on climate is possibly one of the contributions to the difference of climate change existed between the southern and northern parts of the Eastern China during a warm season.

Recent spatial and temporal variability and trends of sunshine duration over the Iberian Peninsula from a homogenized data set

This paper describes the construction of a new data set of sunshine duration over the Iberian Peninsula (IP), based upon 72 monthly instrumental series covering the 1931–2004 period. Particular emphasis is placed upon the quality control, gap filling, and homogenization procedures. We also produced a gridded version (1° × 1° resolution, latitude, and longitude) of the homogenized data set covering the whole IP with 84 cells. We subsequently analyzed sunshine duration data in search of temporal variability, long‐term trends, and spatial differences over the IP. The analyses were carried out on the mean series calculated for the whole IP and for four subregions, at annual, seasonal, and monthly resolution. We defined the subregions using a principal component analysis applied to the sunshine duration data. The temporal evolution of the mean annual series for the whole IP shows a decrease in sunshine duration from the 1950s to the early 1980s, followed by a positive trend up to the end of the 20th century, which matches the “global dimming” and the subsequent and recent “brightening” described for other regions in international scientific literature. The most interesting seasonal significant trend for the IP series was found for summer (−0.9% per decade, over the 1951–2004 period); this trend is influenced by the months of July and August in two subregions. In addition, important trends ranging from +2.8 to +3.8% per decade were observed for the March series for all Mediterranean climate subregions.