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1.
The relationship between monsoon cloud cover and incoming solar radiation in the Arabian Sea is examined utilising the available observations of daily mean total cloud amount and solar radiation collected during the summer monsoon. With these data sets, various cloud correction formulae are evaluated. For the estimation of solar radiation, the formulation of Laevastu (1960) is best, with a minimum error of -4%. A multiple polynomial regression equation based on cloud cover and noon altitude of the sun is developed for estimation of daily radiation. The error between estimated and observed radiation is -2%.  相似文献   

2.
Over the 10?years following the planting of Eucalyptus globulus on an area of 320?ha in 1998, air temperature was measured in the middle of a power line corridor and compared with temperatures recorded at meteorological stations located 11.2 and 35.7?km away. At these reference stations, the annual means of both daily minimum and daily maximum temperature remained approximately constant. In the power line corridor, annual mean daily minimum temperature also remained approximately constant, but annual mean daily maximum temperature fell by about 3.6°C; in particular, between years 4 and 7 the cooling rate was on average about 0.7°C per year. The resulting sigmoid time course of annual mean daily temperature range may partly reflect the evolution of evapotranspiration from the plantation, but seems to be mainly attributable to the shading of the power line corridor by the growing trees, being closely correlated with solar irradiance at the center of the corridor as estimated from tree growth data using sun charts and standard formulae for clear-sky solar irradiance.  相似文献   

3.
Running variance analysis and maximum entropy spectral analysis applied to Mount Wilson rotation data yield arguments in favor of a connection between variations in the Sun's rotation rate, energetic X-ray flares, and impulses of the torque (IOT) in the Sun's irregular motion about the barycenter of the planetary system. Such IOT, that have been shown to be related to the secular cycle of solar activity and excursions of the Maunder minimum type, also seem to be linked to outstanding peaks in geomagnetic activity, maxima in ozone concentration, incidence of blocking type circulation, as well as rainfall over Central Europe, England/Wales, eastern United States, and India. Statistical tests, that confirm these links, additionally point to IOT connection with temperature in Central Europe and the number of icebergs that pass south of latitude 48° N. IOT relationship with X-ray flares and strong geomagnetic storms was tested in successful long range forecasts.Glossary of Abbreviated Terms A c Equatorial angular sidereal solar rotation rate corrected for scattered light and averaged over respective Carrington rotations. - c-events See JU-CM-CSc. - CM Center of mass of the solar system. - CS Center of the Sun. - L Change of angular momentum L in the Sun's orbital motion about CM caused by an impulse of the torque (IOT). This change is measured by the time integral of the torque . - df Degrees of freedom. - g-events See JU-CM-CSg. - IOT Impulse of the torque in the Sun's irregular orbital motion about the center of mass of the solar system CM. The intensity of IOT is measured by the change in angular momentum L effected by the impulse. - JU-CM-CS Solar system constellation that is formed when the center of mass CM, the Sun's center CS and the giant planet Jupiter (JU) are in line. JU-CM-CS events initiate impulses of the torque IOT in the Sun's irregular revolution about CM. - JU-CM-CSc JU-CM-CS event that is accompanied with a sharp increase in orbital angular momentum and centrifugal motion of the Sun away from CM. - JU-CM-CSg JU-CM-CS event that goes along with a steep decrease in orbital angular momentum L and centripetal motion of the Sun toward CM due to prevailing gravitation. - L Angular momentum of the Sun's orbital motion around CM. - T Torque, the varying rotary force applied to the Sun in its orbital motion about CM that is equal to the time rate of change of the angular momentum L. - v Running variance: the smoothing technique of running means over two or more consecutive readings is applied to variance, the square of the standard deviation.  相似文献   

4.
山东禹城紫外辐射变化特征及其估测方程的建立   总被引：1，自引：0，他引：1  
刘慧  胡波  王跃思  王式功 《大气科学》2015,39(3):503-512
本文对2005～2011年山东禹城地区观测得到的紫外辐射的时间变化特征及紫外辐射与总辐射比值的变化特征进行了分析, 并结合气温、降水和露点温度资料建立了禹城地区的紫外辐射估测方程。结果表明:紫外辐射日累计值的变化范围为0.10～1.20 MJ m-2 d-1, 年平均值为0.468 MJ m-2 d-1;紫外辐射日、季节变化规律与总辐射一致, 季节变化都表现为冬季小夏季大, 最小值出现在1月, 最大值出现在6月, 日变化则呈现早晚小中午大的特征;紫外辐射与总辐射的比值范围为0.023～0.046, 其季节变化特征也是冬季小夏季大, 该比值随晴空指数的增大而减小, 而在晴空指数大于0.5时比较稳定。利用温度日较差(日最高气温与最低气温的差值)建立了紫外辐射估测方程, 决定系数R2达0.80, 平均相对误差为0.19, 估测紫外线等级与实测紫外线等级相差不大于1的数据占95%, 该方法可以较好地进行紫外辐射等级的估测。  相似文献   

5.
The characteristics of net radiation (Rn)(0.3--10 μm) in Lhasa and Haibei in the Tibetan Plateau were analyzed based on long-term in-situ measurements of surface radiation data. The monthly average of daily Rn reached a minimum during the winter period followed by an increase until May and then a decline until January. This variation is consistent with solar activity. The annual mean daily total Rn values were 0.92 MJ m-2 d-1 and 0.66 MJ m-2d-1 in Lhasa and Haibei, respectively. A relationship between Rn and broadband solar radiation (Rs) was demonstrated by a good linear correlation at the two sites. Rn can be an accurate estimate from Rs. The estimated Rn values were similar to the observed values, and the relative deviations between the estimates and measurements of Rn were 2.8% and 3.8% in Lhasa and Haibei, respectively. The application of the Rn estimating model to other locations showed that it could provide acceptable estimated Rn values from the Rs data. Furthermore, we analyzed the influence of clouds on Rn by different clear index (Ks), defined as the ratio of Rs to the extraterrestrial solar irradiance on a horizontal surface. The results indicate that more accurate results are associated with increased cloudy conditions. The influence of the albedo was also considered, but its inclusion in the model resulted in only a slight improvement. Because surface albedo is not usually measured, an expression based solely on global solar radiation could be of more extensive use.  相似文献   

6.
Summary The annual and monthly mean diurnal variations of the diffuse fraction of global solar irradiance arriving on the ground at a tropical station in Sub-Sahel Africa is here been reported. The monthly mean hourly values of the diffuse fraction (K d ) for such clear-sky months as February, March and November at this location, which approach a minimum at about local noon, are observed to lie generally below 0.50 during the period from 11:00 to 15:00 hrs (LST). Consequently, solar concentrators utilising parabolic mirrors are expected to have high performance during these months in this region. Like the mainly-cloudy and wet months (June to August) in which monthly mean hourly values of K d higher than 0.62 have been recorded, the corresponding diffuse fraction for dust-haze months (mostly December and January) with high turbidity coefficients were generally above 0.50. Monthly mean hourly values of K d for less cloudy months (April, May, September and October) ranged between 0.48 and 0.77 during the period from 11:00 to 15:00 hrs (LST). The effects of atmospheric dust-haze, clouds and albedo on the monthly mean diurnal variation of the diffuse fraction has been discussed. Also reported are the characteristic values of K d for sets of months with relatively similar atmospheric and sky conditions at this location. The annual variations of the monthly mean daily values of K d which exhibit strong seasonal dependence showed a peak in August for both years. Except for the months of February and March, the monthly mean daily totals of K d exhibited similar annual marches during both years. The major discrepancy in the values of the monthly mean daily totals of K d in both years were recorded in the months of February, November and December, with the corresponding K d values for these months in both years agreeing only to within 32.9% in February, 15.4% in November and 16.2% in December. Apart from the aforementioned months, the corresponding monthly mean daily totals of K d for the remaining nine months in both years agreed mostly to within less than 8.4%. The least monthly mean daily ratios of K d were obtained in the relatively clear month of November for both years being 0.43 in 1993 and 0.49 in 1994. On an annual average, the diffuse component was found to constitute 59.6% of the global solar irradiance arriving on the ground at this region in 1993 and 60.9% in 1994. The results been reported here have been compared with a few others emanating from other tropical stations. Received February 5, 1998 Revised May 12, 1998  相似文献   

7.
Surface solar radiation measurements have been made at many meteorological sites for long periods. These data potentially provide higher temporal resolution cloud amount information than traditional estimations of cloud amount recorded in eighths of the sky obscured (oktas). To utilise existing solar radiation datasets for this, two quantities are derived from the surface measurements of global (G) and diffuse (D) solar irradiance, and top of atmosphere solar irradiance (E) — the Diffuse Fraction (DF = D/G) and the Opaqueness (Op = 1 - G/E). These are compared with subjective cloud observations made at Reading daily during 1997 to 2006. This shows that DF measurements are sensitive to cloud amount, particularly for low and moderate cloud coverage. Complimentary information is available in Op, which is particularly sensitive to cloud amount in moderate to overcast cloud coverage. In overcast conditions, DF = 1, during which Op provides a measure of overcast cloud thickness. As well as cloud amount, the variability in DF and Op provides a basis for discriminating between cumuliform and stratiform cloud: large variability indicates convective cloud whereas only small variability occurs under stratiform cloud.  相似文献   

8.
Summary This work describes a new algorithm to characterize sky condition in intervals of 5 min using four categories of sun exposition: apparent sun with cloud reflection effects; apparent sun without cloud effects; sun partially concealed by clouds; and sun totally concealed by clouds. The algorithm can also be applied to estimate hourly and daily sky condition in terms of the traditional three categories: clear, partially cloudy and cloudy day. It identifies sky conditions within a confidence interval of 95% by minimizing local climate and measurement effects. This is accomplished by using a logistic cumulative probability function to characterize clear sky and Weibull cumulative probability function to represent cloudy sky. Both probability functions are derived from frequency distributions of clearness index, based on 5 minutes-averaged values of global solar irradiance observed at the surface during a period of 6 years in Botucatu, Southeastern of Brazil. The relative sunshine estimated from the new algorithm is statistically comparable to the one derived from Campbell-Stocks sunshine recorder for both daily and monthly values. The new method indicates that the highest frequency of clear sky days occurs in Botucatu during winter (66%) and the lowest during the summer (38%). Partially cloudy condition is the dominant feature during all months of the year.  相似文献   

9.
A mean meridional circulation model of the stratosphere, incorporating radiative heating and photochemistry of the oxygen‐hydrogen‐nitrogen atmosphere, is used to simulate the meridional distributions of O3, HOX, N2O,NOX, temperature and the three components of mean motion for the summer and winter seasons under steady‐state conditions. The results are generally in good agreement with the available observations in the normal stratosphere. The model has been applied to assess the effects of water vapour and nitrogen oxide perturbations resulting from aircraft emissions in the stratosphere. It is found that a fleet of 500 Boeing‐type sst's, flying at 20 km and 45°N in the summer hemisphere and inserting NOx at a rate of 1.8 megatons per year, has the effect of reducing the global total ozone by 14.7%. Similar calculations for 342 Concorde/TU‐114's, cruising at 17 km and injecting NOx at a rate of 0.35 megatons per year, show a global‐average total‐ozone reduction of 1.85%. Although water vapour is considered important, because of its ability to convert NO2 into HNO3, the direct effect on global‐average total‐ozone reduction resulting from the 100% increase in the stratospheric water content is less than 1%. The changes in the chemical structure (HO^NO^), temperature, and mean motions associated with the ozone reduction are also investigated in the case of the 1.8‐megaton‐per‐year NOX perturbation. It is shown that the reduced meridional temperature gradient in the middle and upper stratosphere resulting from the NOx perturbation leads to the weakening of the tropical easterly jet in the summer hemisphere and mid‐latitude westerlies in the winter season.

The sensitivity of the model solutions to an alternate choice of input parameters (diffusion coefficients and solar photodissociation data) is tested and the main deficiency of the model is pointed out.  相似文献   

10.
Meteorological observations in the city of Cádiz are acknowledged as having been made from the middle of the 18th century onwards although they were only recorded and preserved in documentary form from 1789 onwards. Data readings were taken at the new Naval Observatory in San Fernando, ten kilometres from Cádiz, from 1797 onwards. Continuous series for temperature and atmospheric pressure at a daily resolution have been compiled and constructed from 1817 until 1996. The data series is composed of thrice daily observations made at Cádiz (1821–1880) by local observers and hourly data from Naval Observatory at San Fernando (1870–1996).  相似文献   

11.
Spectra and co-spectra of the streamwise (u) and normal or vertical (w) velocity fluctuations have been measured in the inner region of a large Reynolds number laboratory boundary layer over a rough wall. There is reasonable evidence of ak 1 –1 range in theu spectrum (wherek 1 is the streamwise wavenumber). Such a range results from an overlap between a spectral region dominated by largescale, inactive motion, which scales on the boundary-layer thickness, and a region dominated by smaller-scale, active motion which scales on the distance from the wall. Spectra ofw, anduw cospectra, scale in a manner consistent with the dominance by active motion. The present spectral data do not support local isotropy over the inertial subrange. A comparison between measuredw spectra and calculations based on isotropy indicates that the inertial subrange anisotropy is only slightly affected by the magnitude of the non-dimensional mean shear.  相似文献   

12.
Abstract

Observations of the motion of ocean surface drifters are used to evaluate numerical simulations of surface currents in the region of Queen Charlotte Sound on the West Coast of Canada. More than 30 surface Argos drifters were deployed in the spring and summer of 1995, revealing daily average currents of 10 to 40 cm s–1 near the coast of Vancouver Island in summer, and less than 10 cm s–1 in mid‐sound. Wind observations in this region are provided by a network of weather buoys. Comparison of daily average drifter velocities and winds shows that the drifters moved at 2 to 3% of the wind speed, and at about 30 degrees to the right of the wind.

A complex transfer function is computed between daily wind and drifter vectors using least squares techniques. The ratio of variance in the least squares residual currents to the variance of observed drifter currents is denoted γ2. A percent goodness‐of‐fit is defined as g(γ2) = 100(1 – γ2), and is 42% for the case of daily winds and drifter currents. Drifter‐measured currents are compared with two numerical simulations of surface currents: Fundy5, a steadystate baroclinic model based on historical water property measurements in summer, and the Princeton Ocean Model (POM), a prognostic, baroclinic model forced by the measured winds. Fundy5 by itself provides a goodness‐of‐fit of only 3%, whereas POM has g(γ2) = 42%. The combination of Fundy5 plus daily wind gives g(γ2) = 43%. Although the prognostic model performs only as well as the winds by themselves, it simulates the near shore currents more accurately and reproduces the speeds and veering in the surface Ekman layer on average without bias. Residual currents unexplained by POM are likely due to advection of water masses into this region and horizontal inhomogeneities in the density field that are not input to the model, as well as to Stokes drift of wind waves and to net Lagrangian tidal motion not represented by the model.  相似文献   

13.
Summary Variability of atmospheric turbidity calculated from direct beam solar radiation measurements and the transverse coherence length,r 0, derived from differential image motion of stellar sources show pronounced fluctuations on the order of a few minutes under convectively unstable conditions in a desert environment. The quiescent periods, neutral events, when local near surface adiabatic conditions occur show substantial reductions in the fluctuations of the same quantities. Image motion results for nighttime (stable) conditions display slowing varying patterns with reduced short term (few minutes) variations.The measurements were taken using a suite of instrumentation probing the same volume of atmosphere. The instrumentation used includes a pyrheliometer, Atmospheric Turbulence Measurement and Observation System (ATMOS), a sodar, a scintillometer, and tower- mounted sensors. A time-height display of sodar data calibrated for the refractive index structure parameter,C n 2 , coupled with scintillometer measurements show the diurnal evolution of the boundary layer responding to the local heating-cooling cycle and drainage flows from the surrounding mountains. Several atmospheric features are seen and discussed in these results as they affect the nature of the patterns of turbidity andr 0. Of particular interests are the development of convection, changes in the capping inversion, thermal plume structures, neutral events, and wave-turbulence interactions. Sinusoidal oscillations, identified as internal gravity waves, are seen in the nighttime laminated structures.With 10 Figures  相似文献   

14.
We report on field observations in January 2009 (austral summer) of atmospheric dust devils in the northern part of the Atacama Desert in South America (≈20◦S). An extremely high level of dust-devil activity over the study site has been observed, dependent on local meteorological conditions. We found a high correlation between the dust-devil frequency of occurrence and the Obukhov length scale, L, calculated from meteorological gradient measurements, with a clear tendency for this frequency to increase with decreasing −L. The upper threshold values of −L ≈ 20–30 m, and the 2-m mean wind speed, V 2 ≈ 8m s−1, for dust-devil occurrence have been found, but the minimal V 2 threshold was not observed. Parallel routine meteorological measurements enabled us to calculate the main constituents of the surface energy balance, to obtain direct estimates of the surface albedo (α ≈ 0.21 at the solar noon) and to summarize the local conditions.  相似文献   

15.
Summary The mean daily march of pressure (hourly values) for each month of the 96 year period 1894–1989 in Athens, Greece is studied using Fourier analysis. The annual variation of the harmonic parameters (amplitude, time of maximum,x andy-components) is examined. The globally excited 2nd and 3rd harmonics show in general the same behaviour as in other places of the Earth. Similar features show the corresponding parameters of the daily solar radiation march. The first harmonic displays some local characteristics. The long period fluctuations study revealed statistically significant trends in most parameters of the 2nd harmonic, most strikingly the 0.5 h shift in the time of its maximum during the 20th century. Power spectrum analysis showed the existence of a biennial oscillation inB 1, thex-component of the first harmonic, but this oscillation is mainly confined to the second half of the entire period. A periodicity of about 6 years which could be associated to the Southern Oscillation was also found inB 1 while inA 1, they-component, a periodicity close to the 11-year solar cycle and another one close to the nutation of the Earth's axis are present. The lunar tides are too small to be detected by the same methods. However the semilunar tide was revealed to be 10–20 times smaller than the semisolar.With 8 Figures  相似文献   

16.
利用2005~2011年的太阳辐射观测资料分析三江平原地区光合有效辐射(Qp)的时间变化特征及其与总辐射(Rs)比值(Qp/Rs)的变化规律,结果表明,Qp与Rs具有相同的季节变化特征;Qp日累计值的变化范围为60.47~0.11 mol m-2 d-1,年均值为23.76 mol m-2 d-1。Qp/Rs的变化范围为1.52~2.07 mol MJ-1,年均值为1.91 mol MJ-1。Qp/Rs和Qp季节变化一致,两者都是夏季最大,春秋次之,冬季最小。通过利用2011年的Qp观测数据、大气质量数与晴空指数的相互关系,建立了适合于估量三江地区Qp的经验方程,估算值与观测值的相对误差在5.7%以内。  相似文献   

17.
Parameterization and mapping of solar radiation in data sparse regions   总被引：1，自引：0，他引：1  
Knowledge of temporal and spatial variation of solar radiation is essential for many applications. In this work, a simple and feasible procedure is conducted to map the daily solar radiation for Liaoning province, one of the most important agricultural areas in China, but with sparsely measured solar radiation data. The daily sunshine duration are interpolated to the whole area, subsequently, solar radiation are calculated by ?ngstr?m-Prescott model, the generic parameters of which are determined by least square to minimize the overall fitting residual between the ratio of actual to potential sunshine duration and the ratio of actual to extra-terrestrial solar radiation of the sites where solar radiation are available. In other local regions with sparse data, mapping of the solar radiation could be done following the simple procedure. In the present study area, using the interpolated daily sunshine duration data by ANUSPLIN, ?ngstr?m-Prescott model with the generic parameters (a = 0.505, and b = 0.204) returns reasonable results, with the overall RMSE of 2.255 MJ m?2, and RRMSE of 16.54%. The daily solar radiation varies between 5.26 in December and 22.74 MJ m?2 in May, and shows an obviously spatial variation which is mainly contributed to the climate and topography. The substitution of solar radiation from nearby station is preferred to estimation by ?ngstr?m-Prescott model if the distance between the stations falls below the threshold of 135 ± 15 km. The RMSE of such substitution increases by approximately 0.157 MJ m?2 per 10 km.  相似文献   

18.
The use of sodars in the study of stably stratified flows influenced by terrain is reviewed. We start with the equations of motion governing flow over inclined slopes and describe the relation between acoustic backscatter and local Richardson number. We then discuss sodar observations taken over the east Antarctic ice sheet and in a variety of complex terrain studies. These diverse observations reveal the influence of waves at periods from minutes to hours, the effects of ambient winds aiding and opposing drainage flows, complex phenomena in basin topography, and the breakup of the valley inversions with the onset of solar insolation.  相似文献   

19.
Summary The broadband solar absorptivity concept is employed to parameterize the aerosol absorption effect. The solar radiation model developed by Liou and his associates was modified to incorporate the parameterization of solar radiative transfer in an aerosol layer. Comparison of the results from this method with other schemes exhibits close agreement. A Sahara dust storm case was also chosen to test the performance of the present model, and the computed heating rate profiles agree well with calculations based on optical properties derived from observations for both clear and dust cases. In general, enhanced heating due to aerosol absorption of solar flux occurs particularly in the lower troposphere (below 5 km). The heating rate is independent of the scattering partition factor (), but the planetary albedo increases with . Further study shows that the aerosol heating is sensitive to the surface albedo (r s ) and to the cosine of the solar zenith angle (µ 0). The decrease inr s and/or increase inµ 0 lower the solar heating rate, the planetary albedo and the atmospheric absorptivity, but raise the surface absorptivity due to reduced multiple reflection between the atmosphere and surface.With 9 Figures  相似文献   

20.
Simulated impacts of global and regional climate change, induced by an enhanced greenhouse effect and by Amazonian deforestation, on the phenology and yield of two grain corn cultivars in Venezuela (CENIAP PB-8 and OBREGON) are reported. Three sites were selected:Turén, Barinas andYaritagua, representing two important agricultural regions in the country. The CERES-Maize model, a mechanistic process-based model, in theDecision Support System for Agrotechnology Transfer (DSSAT) was used for the crop simulations. These simulations assume non-limiting nutrients, no pest damage and no damage from excess water; therefore, the results indicate only the difference between baseline and perturbed climatic conditions, when other conditions remain the same. Four greenhouse-induced global climate change scenarios, covering different sensitivity levels, and one deforestation-induced regional climate change scenario were used. The greenhouse scenarios assume increased air temperature, increased rainfall and decreased incoming solar radiation, as derived from atmospheric GCMs for doubled CO2 conditions. The deforestation scenarios assume increased air temperature, increased incoming solar radiation and decreased rainfall, as predicted by coupled atmosphere-biosphere models for extensive deforestation of a portion of the Amazon basin. Two baseline climate years for each site were selected, one year with average precipitation and another with lower than average rainfall. Scenarios associated with the greenhouse effect cause a decrease in yield of both cultivars at all three sites, while the deforestation scenarios produce small changes. Sensitivity tests revealed the reasons for these responses. Increasing temperatures, especially daily maximum temperatures, reduce yield by reducing the duration of the phenological phases of both cultivars, as expected from CERES-Maize. The reduction of the duration of the kernel filling phase has the largest effect on yield. Increases of precipitation associated with greenhouse warming have no effects on yield, because these sites already have adequate precipitation; however, the crop model used here does not simulate potential negative effects of excess water, which could have important consequences in terms of soil erosion and nutrient leaching. Increases in solar radiation increased yields, according to the non-saturating light response of the photosynthesis rate of a C4 plant like corn, compensating for reduced yields from increased temperatures in deforestation scenarios. In the greenhouse scenarios, reduced insolation (due to increased cloud cover) and increased temperatures combine to reduce yields; a combination of temperature increase with a reduction in solar radiation produces fewer and lighter kernels.A report of thePAN-EARTH Project, Venezuela Case Study.  相似文献   

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