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1.
Broadband solar irradiance data obtained in the spectral range 400–940 nm at Kwangju, South Korea from 1999–2000 have been analyzed to investigate the effects of cloud cover and atmospheric optical depth on solar radiation components. Results from measurements indicate that the percentage of direct and diffuse horizontal components of solar irradiance depend largely on total optical depth (TOD) and cloud cover. During summer and spring, the percentages of diffuse solar irradiance relative to the global irradiance were 5.0% and 4.9% as compared to 2.2% and 3.0% during winter and autumn. The diffuse solar irradiance is higher than the direct in spring and summer by 24.2%, and 40.6%, respectively, which may largely be attributed to the attenuation (scattering) of radiation by heavy dust pollution and large cloud amount. In cloud-free conditions with cloud cover ≤2/10, the fraction of the direct and diffuse components were 66.0% and 34.0%, respectively, with a mean daily global irradiance value of 7.92±2.91 MJ m−2 day−1. However, under cloudy conditions (with cloud cover ≥8/10), the diffuse and direct fractions were 97.9% and 2.2% of the global component, respectively. The annual mean TOD under cloudless conditions (cloud cover≤2/10) yields 0.74±0.33 and increased to as much as 3.15±0.67 under cloudy conditions with cloud amount ≥8/10. An empirical formula is derived for estimating the diffuse and direct components of horizontal solar irradiance by considering the total atmospheric optical depth (TOD). Results from statistical models are shown for the estimation of solar irradiance components as a function of TOD with sufficient accuracy as indicated by low standard error for each solar zenith angle (SZA). 相似文献
2.
L. Alados-Arboledas I. Alados I. Foyo-Moreno F. J. Olmo A. Alcntara 《Atmospheric Research》2003,66(4):273-290
The purpose of this study is to examine the effect of clouds on the ultraviolet erythemal irradiance. The study was developed at three stations in the Iberian Peninsula: Madrid and Murcia, using data recorded in the period 2000–2001, and Zaragoza, using data recorded in 2001. In order to determine the cloud effect on ultraviolet erythemal irradiance, we considered a cloud modification factor defined as the ratio between the measured values of ultraviolet erythemal irradiance and the corresponding clear-sky ultraviolet erythemal irradiance, which would be expected for the same time period and atmospheric conditions. The dependence of this cloud modification factor on total cloud amount, cloud type and solar elevation angle was investigated. The results suggest that the effect of cloud on ultraviolet erythemal irradiance can be parameterized in a simple way in terms of the cloud amount. Our results suggest that the same cloud modification factor model can be used at the three analysed locations estimating the ultraviolet erythemal irradiance with mean bias deviation (MBD) in the range of the expected experimental errors. This cloud modification factor is lower than that associated to the whole solar spectral range, indicating that the attenuation for the ultraviolet erythemal irradiance is lower than that associated to other solar spectral ranges. The cloud modification factor for ultraviolet erythemal irradiance presents dependence with solar elevation, with opposite dependencies with solar elevation for overcast and partial cloud cover conditions, a fact that can be explained in terms of the influence of reflection-enhancement of the ultraviolet irradiance in the last case. Concerning the influence of cloud type, a limited study of two cloud categories, low and medium level and high level, indicated that for overcast conditions, lower clouds presents an attenuation of ultraviolet erythemal irradiance 20% greater than that associated to high level clouds. 相似文献
3.
P. M. James 《Climate Dynamics》2006,27(2-3):215-231
The frequency of occurrence of persistent synoptic-scale weather patterns over the European and North-East Atlantic regions is examined in a hierarchy of climate model simulations and compared to observational re-analysed data. A new objective method, employing pattern correlation techniques, has been constructed for classifying daily-mean mean-sea-level pressure and 500 hPa geopotential height fields with respect to a set of 29 European weather regime types, based on the widely known subjective Grosswetterlagen (GWL) system of the German Weather Service. The objective method is described and applied initially to ERA40 and NCEP re-analysis data. While the resulting daily Objective-GWL catalogue shows some systematic differences with respect to the subjectively-derived original GWL series, the method is shown to be sufficiently robust for application to climate model output. Ensemble runs from the most recent development of the Hadley Centre’s Global Environmental model, HadGEM1, in atmosphere-only, coupled and climate change scenario modes are analysed with regards to European synoptic variability. All simulations successfully exhibit a wide spread of GWL occurrences across all regime types, but some systematic differences in mean GWL frequencies are seen in spite of significant levels of interdecadal variability. These differences provide a basis for estimating local anomalies of surface temperature and precipitation over Europe, which would result from circulation changes alone, in each climate simulation. Comparison to observational re-analyses shows a clear and significant improvement in the simulation of realistic European synoptic variability with the development and resolution of the atmosphere-only models. 相似文献
4.
This paper focuses on different ways of characterizing the solar radiative regime of a day and the stability of this regime. The days may be stratified in classes of cloud shade, observed total cloud cover amount, daily averaged clearness index, and fractal dimension of the solar global irradiance signal. A new Boolean parameter related to solar irradiance fluctuation is defined, namely the sunshine stability number. The time averaged value of the sunshine stability number is used for the characterization of the radiative regime stability during a given time interval. Ranking the days from the view-point of the stability of their radiative regime is performed by using the daily average value of the sunshine stability number and appropriately defined values of disorder and complexity, respectively. Measurements performed in the Romanian town of Timisoara (latitude 45°46?? N, longitude 21°25?? E and 85?m altitude above mean sea level) are used here. They refer to time series of global and diffuse solar irradiance recorded at 15-s time interval between sunrise and sunset during all the days in 2009. 相似文献
5.
E. J. M. van den Besselaar A. M. G. Klein Tank G. van der Schrier 《Theoretical and Applied Climatology》2010,99(3-4):431-439
The aim of this study is to determine the influence of atmospheric circulation on the recently observed changes in the number of warm days and cold days in Europe. The temperature series for stations in the European Climate Assessment and Data set project and the Grosswetterlagen (GWL) were used here. The temperature series were first adjusted for global warming before determining the indices for cold and warm extremes. The 29 GWLs were grouped in ten circulation types. Then, the number of days a certain circulation type occurred was determined for each winter (December, January and February) and summer (June, July and August). The relation between the circulation type frequencies and the temperature indices was modelled with a multi-regression fit over the period 1947–1974 and tested for the period 1974–2000. The difference between the observed indices and the calculated indices in the second period (using the fit coefficients for the first period) shows a warming effect for both winter and summer and for at least the warm day index, which is unaccounted for by the global warming trend. A simple snow model shows that variations in the European snow cover extent are likely influencing the cold and warm day indices in winter: there is a correlation between the decreasing trend of the snow cover extent in Europe and the increasing (decreasing) trend of the number of warm (cold) days for stations throughout Europe. 相似文献
6.
Summary Two UV-Biometer 501A instruments were used to estimate global erythemal irradiance at two locations in southwest Sweden;
the Earth Sciences Centre, University of G?teborg (57.69° N; 11.92° E) and the island of Nordkoster, 200 km to the north (58.83° N;
10.72° E).
A semi-empirical radiative transfer model was used to calculate the global erythemally effective irradiance under clear skies.
A ratio of the hourly measured to clear-sky modelled irradiance was then derived for zenith angles 35–70°. Subsequent comparisons
were then made with routine measurements of sunshine duration at G?teborg and sunshine duration, cloud cover, type and height
at Nordkoster.
Cloud transmission of UV-B irradiance decreases with increasing solar zenith angle, with cloud attenuation being 8% stronger
at Nordkoster Island for zenith angles >>;60°. Transmission also decreases with increasing cloud cover such that overcast
cloud conditions reduce transmissions by an average of 75%. In addition, cloud type affects the amount of ground incident
irradiant flux. Fractus cloud afforded the least UV-B transmission (0.16), while cirrus filaments afforded the most (0.95).
The spatial and temporal distribution of clouds appears tobe non-random. Under conditions of 1 to 3 octas, sky cover, clouds
appear to be concentrated in line with the sensor and Sun on more occasions than that expected given a random cloud distribution.
The same cloud cover condition also resulted in many instances of ground incident irradiance above clear-sky values. The presence
of cumuliform clouds appears to increase the likelihood of the latter phenomena.
Received January 4, 1998 相似文献
7.
Ting Wei Jian Li Xinyao Rong Wenjie Dong Bingyi Wu Minghu Ding 《Acta Meteorologica Sinica》2018,32(6):881-895
The Chinese Academy of Meteorological Sciences Climate System Model (CAMS-CSM) is a newly developed global climate model that will participate in the Coupled Model Intercomparison Project phase 6. Based on historical simulations (1900?2013), we evaluate the model performance in simulating the observed characteristics of the Arctic climate system, which includes air temperature, precipitation, the Arctic Oscillation (AO), ocean temperature/salinity, the Atlantic meridional overturning circulation (AMOC), snow cover, and sea ice. The model?data comparisons indicate that the CAMS-CSM reproduces spatial patterns of climatological mean air temperature over the Arctic (60°?90°N) and a rapid warming trend from 1979 to 2013. However, the warming trend is overestimated south of the Arctic Circle, implying a subdued Arctic amplification. The distribution of climatological precipitation in the Arctic is broadly captured in the model, whereas it shows limited skills in depicting the overall increasing trend. The AO can be reproduced by the CAMS-CSM in terms of reasonable patterns and variability. Regarding the ocean simulation, the model underestimates the AMOC and zonally averaged ocean temperatures and salinity above a depth of 500 m, and it fails to reproduce the observed increasing trend in the upper ocean heat content in the Arctic. The large-scale distribution of the snow cover extent (SCE) in the Northern Hemisphere and the overall decreasing trend in the spring SCE are captured by the CAMS-CSM, while the biased magnitudes exist. Due to the underestimation of the AMOC and the poor quantification of air–sea interaction, the CAMS-CSM overestimates regional sea ice and underestimates the observed decreasing trend in Arctic sea–ice area in September. Overall, the CAMS-CSM reproduces a climatological distribution of the Arctic climate system and general trends from 1979 to 2013 compared with the observations, but it shows limited skills in modeling local trends and interannual variability. 相似文献
8.
Summary Ground-based measurements of incoming solar irradiance and cloud observations during a 26 year period (1965–1990) at Bergen, Norway were used in conjunction with a comprehensive radiation model to infer the cloud optical depth under completely overcast conditions.Month-to-month and year-to-year (April through October) statistics of the cloud optical depth and observed cloud forms are presented. Some climate-related features, specifically, diurnal and seasonal variabilities in are examined. The effects of local cloudiness are pointed out and discussed. There appears to be a slight trend towards increasing cloud optical depth at noon during the warm period of the year. The possible uncertainties due to unknown size of cloud droplets are analyzed by model simulations. Possible directions for future research are suggested provided more meteorological and/or satellite information is available.With 9 Figures 相似文献
9.
The study examines how regional climate models (RCMs) reproduce the diurnal temperature range (DTR) in their control simulations over Central Europe. We evaluate 30-year runs driven by perfect boundary conditions (the ERA40 reanalysis, 1961–1990) and a global climate model (ECHAM5) of an ensemble of RCMs with 25-km resolution from the ENSEMBLES project. The RCMs’ performance is compared against the dataset gridded from a high-density stations network. We find that all RCMs underestimate DTR in all seasons, notwithstanding whether driven by ERA40 or ECHAM5. Underestimation is largest in summer and smallest in winter in most RCMs. The relationship of the models’ errors to indices of atmospheric circulation and cloud cover is discussed to reveal possible causes of the biases. In all seasons and all simulations driven by ERA40 and ECHAM5, underestimation of DTR is larger under anticyclonic circulation and becomes smaller or negligible for cyclonic circulation. In summer and transition seasons, underestimation tends to be largest for the southeast to south flow associated with warm advection, while in winter it does not depend on flow direction. We show that the biases in DTR, which seem common to all examined RCMs, are also related to cloud cover simulation. However, there is no general tendency to overestimate total cloud amount under anticyclonic conditions in the RCMs, which suggests the large negative bias in DTR for anticyclonic circulation cannot be explained by a bias in cloudiness. Errors in simulating heat and moisture fluxes between land surface and atmosphere probably contribute to the biases in DTR as well. 相似文献
10.
SST and circulation trend biases cause an underestimation of European precipitation trends 总被引：2，自引：0，他引：2
Ronald van Haren Geert Jan van Oldenborgh Geert Lenderink Matthew Collins Wilco Hazeleger 《Climate Dynamics》2013,40(1-2):1-20
Clear precipitation trends have been observed in Europe over the past century. In winter, precipitation has increased in north-western Europe. In summer, there has been an increase along many coasts in the same area. Over the second half of the past century precipitation also decreased in southern Europe in winter. An investigation of precipitation trends in two multi-model ensembles including both global and regional climate models shows that these models fail to reproduce the observed trends. In many regions the model spread does not cover the trend in the observations. In contrast, regional climate model (RCM) experiments with observed boundary conditions reproduce the observed precipitation trends much better. The observed trends are largely compatible with the range of uncertainties spanned by the ensemble, indicating that the boundary conditions of RCMs are responsible for large parts of the trend biases. We find that the main factor in setting the trend in winter is atmospheric circulation, for summer sea surface temperature (SST) is important in setting precipitation trends along the North Sea and Atlantic coasts. The causes of the large trends in atmospheric circulation and summer SST are not known. For SST there may be a connection with the well-known ocean circulation biases in low-resolution ocean models. A quantitative understanding of the causes of these trends is needed so that climate model based projections of future climate can be corrected for these precipitation trend biases. 相似文献
11.
J. Luterbacher R. Rickli E. Xoplaki C. Tinguely C. Beck C. Pfister H. Wanner 《Climatic change》2001,49(4):441-462
The Late Maunder Minimum (LMM, 1675–1715) denotes the climax of the `Little Ice Age' in Europe with marked climate variability. Investigations into interannual and interdecadal differences of atmospheric circulation between the LMM and the period 1961–1990 have been performedand undertaken based upon sea level pressure (SLP) difference maps, empiricalorthogonal function (EOF) analysis, and objective classification techniques. Since the SLP during the LMM winterwas significantly higher in northeastern Europe but below normal over the central and western Mediterranean, more frequent blocking situations were connected with cold air outbreaks towards central and eastern Europe. Springs were cold and characterized by a southward shift of the mid-latitude storm tracks. Summers in western, central Europe and northern Europe were wetter and slightly cooler than they are today due to a weakerAzores high and a more southerly position of the mean polar front axes. Autumns showed a significantly higher pressure over northern Europe and a lower pressure over continental Europe and the Mediterranean, an indication of an advanced change from summer to winter circulation. It is suggested that the pressure patterns during parts of the LMM might be attributed to the combination of external forcing factors (solar irradiance and volcanic activity) and internal oscillations and couplings in the North Atlantic. 相似文献
12.
This is a study of ozone profile shapes in the 800 to 100 millibar range obtained with balloonsonde data over Trivandrum (8.5° N) during 1975–76 and possible associations of these shapes to some meteorological parameters.Whereas monotonic ozone profiles were noted with clear weather conditions, those associated with cloud cover show three basic anomalous features. Some bulges of increased values are observed in the range of 800 to 500 mb. In the 500–100 mb range, short range or localized cloud cover or passing weather disturbances are associated with fluctuation patterns in the ozone profile and an average depleted value of ozone. The fluctuations are also associated with changing wind speed and direction at these heights.Possible causative mechanisms are discussed. Lightning associated with thundestorm, producing additional CO and NO are sought to interpret the bulges at lower heights. The decrease in values as well as the fluctuation patterns are suggested as due to possible incursion of water vapour from troposphere to stratosphere in the tropical region and dynamical effects associated with it. 相似文献
13.
Long-term patterns of solar irradiance forcing in model experiments and proxy based surface temperature reconstructions 总被引：3，自引：0，他引：3
Comparisons are made of long-term empirical and model-estimated patterns of solar irradiance forcing during a 200-year period (1650-1850), which precedes any apparent anthropogenic influence on climate. This interval encompasses a considerable range (approximately 4 W/m2) of estimated variation in solar output, including the "Maunder" and "Dalton" Minima of solar irradiance, and an intervening interval of relatively high values of irradiance, but does not encroach into the industrial era wherein it is difficult to separate solar and anthropogenic influences. Particular emphasis is placed on comparing empirical and modeled patterns of forced surface temperature variation. The empirical patterns bear a greater similarity to the pattern of forced response of a coupled ocean-atmosphere general circulation model (AOGCM) than with an independent model simulation result using an ocean with specified heat transport, both in terms of the spatial pattern of response and implied global mean sensitivity to forcing. Heightened sensitivity in the western Pacific warm pool apparent in the empirical response pattern, is not observed in the forced response of the coupled model. It is possible that this pattern is the result of feedback processes not currently reproduced in course-resolution coupled models. The greatest empirical response is found at the multidecadal-to-century (> 40 year period) time scale, for which the forcing is dominated by the roughly 90-year Gleissberg Cycle of irradiance. This indicates a global-mean sensitivity (approximately 0.3 K/W/m2), which is close to the coupled model result (approximately 0.4 K/W/m2). At decadal time scales (8-25 year period), for which the forcing is dominated by the 11-year and 22-year period solar cycles), the temperature sensitivity is moderately reduced, and its spatial pattern of response is dominated by an apparent resonance with known decadal modes of climate variability. 相似文献
14.
根据太阳总辐射估算模型Q=Q0（a＋bS1）按月确定了博州地区邻近站伊宁的a、b系数,将其对应于博州地区4个站点1961～2006年逐月太阳辐射的计算,据此分析了全地区太阳总辐射的时空分布状况,并对太阳能资源按行业标准进行了评估。结果表明,46a来博州地区的太阳总辐射呈明显下降趋势,整体上冬季减少的贡献率最大;太阳总辐射与总、低云量、相对湿度、雨雪日数具有较好的相关性;造成博州地区太阳总辐射呈下降趋势的重要气候原因是：平均总、低云量,相对湿度,雨雪日数增加的综合作用;博州地区的太阳能资源较丰富,其开发利用的．综合条件较好。 相似文献
15.
Jeffrey C. Rogers 《Climate Dynamics》2013,40(1-2):341-352
Portions of the southern and southeastern United States, primarily Mississippi, Alabama, and Georgia, have experienced century-long (1895–2007) downward air temperature trends that occur in all seasons. Superimposed on them are shifts in mean temperatures on decadal scales characterized by alternating warm (1930s–1940s, 1990s) and cold (1900s; 1960s–1970s) regimes. Regional atmospheric circulation and SST teleconnection indices, station-based cloud cover and soil moisture (Palmer drought severity index) data are used in stepwise multiple linear regression models. These models identify predictors linked to observed winter, summer, and annual Southeastern air temperature variability, the observed variance (r2) they explain, and the resulting prediction and residual time series. Long-term variations and trends in tropical Pacific sea temperatures, cloud cover, soil moisture and the North Atlantic and Arctic oscillations account for much of the air temperature downtrends. Soil moisture and cloud cover are the primary predictors of 59.6 % of the observed summer temperature variance. While the teleconnections, cloud cover and moisture data account for some of the annual and summer Southeastern cooling trend, large significant downward trending residuals remain in winter and summer. Comparison is made to the northeastern United States where large twentieth century upward air temperature trends are driven by cloud cover increases and Atlantic Multidecadal Oscillation (AMO) variability. Differences between the Northeastern warming and the Southeastern cooling trends in summer are attributable in part to the differing roles of cloud cover, soil moisture, the Arctic Oscillation and the AMO on air temperatures of the 2 regions. 相似文献
16.
17.
连山地区云量的影响因子分析 总被引：6，自引：1，他引：5
利用祁连山区4个测站1961~2000年1~12月平均总云量资料,采用合成分析、相关分析和功率谱分析等方法,分析了40年来祁连山区云量与大环流变化的关系。结果表明:祁连山区云量主要受副热带高压、中纬度经(纬)向环流、高原季风和太阳变动影响。当副高面积增大,向北扩展,中纬度纬向环流增强,促使副热带高空锋区北移,冷暖空气在祁连山区交绥次数减少,造成祁连山区云量减少,反之云量增多;高原夏季风强(弱),造成祁连山区云量偏多(少);当太阳活动强烈时,高原近地面大气层易出现热低压,祁连山湿润下垫面和热低压结合,促使对流云增多。 相似文献
18.
Numerical experiments have been carried out with a two-dimensional sector averaged global climate model in order to assess the potential impact of solar variability on the Earth's surface temperature from 1700 to 1992. This was done by investigating the model response to the variations in solar radiation caused by the changes in the Earth's orbital elements, as well as by the changes intrinsic to the Sun. In the absence of a full physical theory able to explain the origin of the observed total solar irradiance variations, three different total solar irradiance reconstructions have been used. A total solar irradiance change due to the photospheric effects incorporated in the Willson and Hudson (1988) parameterization, and the newly reconstructed solar total irradiance variations from the solar models of Hoyt and Schatten (1993) and Lean et al. (1995). Our results indicate that while the influence of the orbital forcing on the annual and global mean surface temperature is negligible at the century time scale, the monthly mean response to this forcing can be quite different from one month to another. The modelled global warming due to the three investigated total solar irradiance reconstructions is insufficient to reproduce the observed 20th century warming. Nevertheless, our simulated surface temperature response to the changes in the Sun's radiant energy output suggests that the Gleissberg cycle (88 years) solar forcing should not be neglected in explaining the century-scale climate variations. Finally, spectral analysis seems to point out that the 10- to 12-year oscillations found in the recorded Northern Hemisphere temperature variations from 1700 to 1992 could be unrelated to the solar forcing. Such a result could indicate that the eleven-year period which is frequently found in climate data might be related to oscillations in the atmosphere or oceans, internal to the climate system. 相似文献
19.
Summary The Indian summer monsoon, one of the earth's most vigorous and energetic seasonally occurring weather events, influences the global atmospheric circulation. Its onset, duration, and intensity are governed by large- and meso-scale geophysical processes, such as surface solar heating and air-sea interactions. In this paper, using innovative combinations of satellite sensor data, we investigate some of these fundamental processes which are closely tied to clouds and control the monsoon system's evolution. The study, which focuses on the monsoon period of June, 1979, examines the low-frequency variability of clouds and their effects on air-sea processes through an analysis of the complex influence clouds play on the surface heat and water budgets. First, the effects of clouds on both the solar and longwave components of the surface radiation budget are assessed using a cloud radiative forcing parameter. While the effects of clouds on the long-wave irradiance act in a manner opposite to their effects on the shortwave irradiance, only a partial compensation is found to take place and the net effect results in a maximum cloud forcing of 60 Wm–2 in the southwestern Arabian Sea. Second, employing satellite-derived precipitation and evaporation estimates, the paper analyzes the net surface fresh water budget variability around the monsoon onset. This budget is important in that fresh water affects the upper ocean density distribution and, consequently, the thermohaline circulation. Two regions are found to dominate the analysis: the western Arabian Sea, where evaporation is dominant by more than 10 mm day–1, and the eastern Arabian Sea, where precipitation is dominant by more than 10 mm day–1. Thus, a strong zonal gradient of fresh water at the surface is established during the monsoon. The last topic investigated is the intraseasonal variability of convection as analyzed using a cloud parameter indicative of deep convection. Cloud oscillations of 30–50 days, associated with the different phases of the monsoon, are found to propagate northward in the eastern Indian Ocean and eastward in the Bay of Bengal. Our analysis not only supports the hypothesis that the 30–50-day oscillation is driven by deep convection but also, and more importantly, suggests that the ocean thermal forcing is modulated by 30–50-day oscillations through cloud-induced surface radiative forcing. Although the results presented are limited in scope and preliminary because of the diffculty in quantifying the accuracy of the parameters examined, they do demonstrate: 1) the role of clouds in modulating the surface heat and water budgets, 2) the advantage of using combinations of multi-sensor and multi-platform satellite observations to quantify interrelated surface heat/water budget processes, and 3) the potential to examine the intraseasonal variability of air-sea interaction processes associated with the monsoon, even though these processes are not directly measurable from space.With 6 FiguresB. DiJulio passed away in September 1990. 相似文献
20.
春季低温连阴雨天气的热带环流和总云量分布 总被引：4，自引：0，他引：4
本文根据长江中下游六省一市3—5月气温与降水资料,确定低温连阴雨天气过程。发现连阴雨及连晴过程所对应的热带环流及波谱特征有明显差异,热带太平洋156°E、180°剖面上总云量分布特征有显著不同,厄尔尼诺年与长江中下游连阴雨天气的关系十分密切。 相似文献