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1.
Photosynthetically active radiation (Q p ) is a key variable in models of net primary productivity and carbon cycle modelling. The relationship between broadband global solar radiation (R s) and Q p is investigated using 6?years of radiation data collected at 9 sites in arid and semi-arid regions of China. The dependence of Q p /R S on aerosol optical depth (AOD) and water vapour content are also discussed. A simple and efficient all-weather empirically derived model is developed to estimate Q p from R s. The annual average daily Q p in arid and semi-arid areas is 29.9?±?11.7 and 27.3?±?10.1?mol?m-2 d-1, respectively. The highest value (31.9?±?11.3?mol?m-2 d-1) appears at Linze in the arid area. The lowest value (24.3?±?9.7?mol?m-2 d-1) appears at Ansai in the semi-arid area. The results show that the monthly variation of the Q p /R s ratio ranges from 1.69?±?0.19?mol?MJ-1 in Aksu to 1.91?±?0.08?mol?MJ-1 in Fukang. There is a small decreasing trend of the ratio of Q p to R s (PAR fraction) in arid and semi-arid regions because of the recent increase in fine aerosols. A simple and efficient empirically model suit for all-weather condition was developed to estimate Q p from R s. The slope a and intercept b of the regression line between estimated and measured values is close to 1 and zero, respectively. The application of the model to data collected from different locations also results in reasonable estimates of Q p .  相似文献   

2.
Integrated observations were made of solar irradiance (including photosynthetically active radiation (PAR), visible radiation (VIS), global radiation (G), etc.), and meteorological parameters at 4 stations in North China between September, 2004 and October, 2006. The ratios of hourly sum of PAR to G (H PAR/H), VIS to G (H VIS/H), and PAR to VIS (H PAR/H VIS) varied smoothly but exhibited significant diurnal, daily, seasonal variations, and were influenced by several factors, such as water vapor, cloud, haze, etc. The objective of this paper is to develop empirical formulas for estimation of hourly and daily sums of PAR and VIS and their relationship under all sky conditions in North China. The calculated PAR and VIS were in agreement with measured values, the relative biases were 13.0?% and 12.4?% for hourly sums, 9.9?% and 9.0?% for daily values, respectively.  相似文献   

3.
Results from the radiation components of seven different human thermal exchange models/methods are compared. These include the Burt, COMFA, MENEX, OUT_SET* and RayMan models, the six-directional method and the new Park and Tuller model employing projected area factors (f p) and effective radiation area factors (f eff) determined from a sample of normal- and over-weight Canadian Caucasian adults. Input data include solar and longwave radiation measured during a clear summer day in southern Ontario. Variations between models came from differences in f p and f eff and different estimates of longwave radiation from the open sky. The ranges between models for absorbed solar, net longwave and net all-wave radiation were 164, 31 and 187?W?m?2, respectively. These differentials between models can be significant in total human thermal exchange. Therefore, proper f p and f eff values should be used to make accurate estimation of radiation on the human body surface.  相似文献   

4.
The measurements of the photosynthetic photon flux density (Qp) and other solar components have been in Beijing for 2-year period. The Qp, broadband solar radiation (Rs) and the PAR fraction (Qp / Rs) showed similar seasonal features that peaked in value during the Summer and reached their lowest value during the Winter. The PAR fraction ranged from 1.68 E M J− 1 (Winter) to 1.98 E M J− 1 (Summer) with an annual mean value of 1.83 E M J− 1. The analysis of the hourly values also revealed a diurnal pattern, with higher values of Qp and Rs being observed around noon. The PAR fraction increased from 1.78 to 1.89 μE J− 1 (hourly values), as the sky conditions changed from clear to cloudy. The monthly mean hourly PAR fraction also revealed a diurnal variation, however, with lower values being observed around noon during most months. In November, the diurnal variations showed an opposite feature in comparison with other months. This is mainly attributed to the diurnal variations in the water vapor concentration.Two models were developed to estimate Qp from Rs. The models consisted of atmospheric parameters that were found to cause substantial changes to the PAR fraction, such as sky clearness, brightness and path length. The estimated Qp obtained via different equations was much closer to the observed values, with relative errors below 20% in Beijing. The Qp and Rs data collected at three stations with featuring different climate types from within Beijing were used for verifying the transferability of the models. The correlation coefficients between the measured and estimated Qp values decreased at these stations, and the relative error increased. This indicates that the estimation models need to be modified accordingly for the local climatic conditions.  相似文献   

5.
The main goal of this work is to describe the anthropogenic energy flux (Q F) in the city of S?o Paulo, Brazil. The hourly, monthly, and annual values of the anthropogenic energy flux are estimated using the inventory method, and the contributions of vehicular, stationary, and human metabolism sources from 2004 to 2007 are considered. The vehicular and stationary sources are evaluated using the primary consumption of energy based on fossil fuel, bio fuel, and electricity usage by the population. The diurnal evolution of the anthropogenic energy flux shows three relative maxima, with the largest maxima occurring early in the morning (??19.9 Wm?2) and in the late afternoon (??20.3 Wm?2). The relative maximum that occurs around noontime (??19.6 Wm?2) reflects the diurnal pattern of vehicle traffic that seems to be specific to S?o Paulo. With respect to diurnal evolution, the energy flux released by vehicular sources (Q FV) contributes approximately 50% of the total anthropogenic energy flux. Stationary sources (Q FS) and human metabolism (Q FM) represent about 41% and 9% of the anthropogenic energy flux, respectively. For 2007, the monthly values of Q FV, Q FS, Q FM, and Q F are, respectively, 16.8?±?0.25, 14.3?±?0.16, 3.5?±?0.03, and 34.6?±?0.41?MJ?m?2?month?1. The seasonal evolution monthly values of Q FV, Q FS, Q FM, and Q F show a relative minimum during the summer and winter vacations and a systematic and progressive increase associated with the seasonal evolution of the economic activity in S?o Paulo. The annual evolution of Q F indicates that the city of S?o Paulo released 355.2?MJ?m?2?year?1 in 2004 and 415.5?MJ?m?2?year?1 in 2007 in association with an annual rate of increase of 19.6?MJ?m?2?year?1 (from 2004 to 2006) and 30.5?MJ?m?2?year?1 (from 2006 to 2007). The anthropogenic energy flux corresponds to about 9% of the net radiation at the surface in the summer and 15% in the winter. The amplitude of seasonal variation of the maximum hourly value of the diurnal variation increases exponentially with latitude.  相似文献   

6.
Summary ?The relationship between global photosynthetically active radiation (PAR) and global solar radiation is studied with a 2-year data archive of hourly values HPAR and HSW of these irradiances obtained at Athalassa, Cyprus. These data are used to determine the temporal variability of HPAR and its dependence on sky conditions. The seasonal variation of the ratio HPAR/HSW obtained from daily data ranges from 0.456 (during summer) to 0.451 (during winter) with an annual mean value of 0.454. The ratio increases from 0.454 to 0.467 (daily values) or from 0.460 to 0.501 (hourly values), as sky conditions change from clear to overcast. Finally, the effect of aerosol content on the HPAR/HSW ratio is found to incur substantial changes in the PAR fraction. Received June 27, 2001; revised April 17, 2002; accepted May 18, 2002  相似文献   

7.
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8.
The environmental impact of aerosols is currently a hot issue that has received worldwide attention. Lacking simultaneous observations of aerosols and carbon flux, the understanding of the aerosol radiative effect of urban agglomeration on the net ecosystem carbon exchange(NEE) is restricted. In 2009-2010, an observation of the aerosol optical property and CO_2 flux was carried out at the Dongguan Meteorological Bureau Station(DMBS) using a sun photometer and eddy covariance systems. The different components of photosynthetically active radiation(PAR),including global PAR(GPAR), direct PAR(DPAR), and scattered PAR(FPAR), were calculated using the Santa Barbara DISORT Atmospheric Radiative Transfer(SBDART) model. The effects of PAR on the NEE between land-atmosphere systems were investigated. The results demonstrated that during the study period the aerosol optical depth(AOD)reduced the DPAR by 519.28±232.89 μmol photons · m~(-2)s~(-1);, but increased the FPAR by 324.93±169.85μmol photons ·m~(-2)s~(-1);, ultimately leading to 194.34±92.62 μmol photons · m~(-2)s~(-1); decrease in the GPAR. All the PARs(including GPAR,DPAR, and FPAR) resulted in increases in the NEE(improved carbon absorption), but the FPAR has the strongest effect with the light use efficiency(LUE) being 1.12 times the values for the DPAR. The absorption of DPAR by the vegetation exhibited photo-inhibition in the radiation intensity 600 photons · m~(-2)s~(-1); in contrast, the absorptions of FPAR did not exhibit apparent photo-inhibition. Compared with the FPAR caused by aerosols, the DPAR was not the primary factor affecting the NEE. On the contrary, the increase in AOD significantly increased the FPAR, enhancing the LUE of vegetation ecosystems and finally promoting the photosynthetic CO_2 absorption.  相似文献   

9.
As photosynthetically active radiation (PAR) variability and PAR estimating methods play an important role in climate change and ecological process research, PAR variation trends and broadband global solar radiation (R s ) ratios (PAR/R s ) in the North China Plain (NCP) are examined using in situ PAR and R s observed data for 2005 to 2011. The annual average PAR value found in the NCP is 22.9 mol m?2 d?1. The highest and lowest values were recorded at Changwu and Luancheng sites, respectively. The highest PAR/R s value was found in Jiaozhouwan due to large water vapor volumes present in this area. PAR/R s levels have increased in the NCP due to a decrease in fine aerosols and increase in water vapor concentration. From these analysis results, a parameterization model that can be applied to all sky conditions was checked. Empirical estimation model comparisons for obtaining PAR values indicate that model was least accurate when R s was used independently. When the model included R s, the clearness index (K s) and the solar zenith angle, the model estimated PAR values with acceptable accuracy. A parameterization model was constructed by considering K s and attenuation factors of PAR under clear weather conditions (ρ clear). The improved parameterization model more accurately predicts values for local sites and for various observation sites.  相似文献   

10.
This study describes the results of artificial neural network (ANN) models to estimate net radiation (R n), at surface. Three ANN models were developed based on meteorological data such as wind velocity and direction, surface and air temperature, relative humidity, and soil moisture and temperature. A comparison has been made between the R n estimates provided by the neural models and two linear models (LM) that need solar incoming shortwave radiation measurements as input parameter. Both ANN and LM results were tested against in situ measured R n. For the LM ones, the estimations showed a root mean square error (RMSE) between 34.10 and 39.48?W?m?2 and correlation coefficient (R 2) between 0.96 and 0.97 considering both the developing and the testing phases of calculations. The estimates obtained by the ANN models showed RMSEs between 6.54 and 48.75?W?m?2 and R 2 between 0.92 and 0.98 considering both the training and the testing phases. The ANN estimates are shown to be similar or even better, in some cases, than those given by the LMs. According to the authors?? knowledge, the use of ANNs to estimate R n has not been discussed earlier, and based on the results obtained, it represents a formidable potential tool for R n prediction using commonly measured meteorological parameters.  相似文献   

11.
华北地区光合有效辐射的计算方法研究   总被引：6，自引：0，他引：6       下载免费PDF全文
2004年9月—2006年10月,选择华北地区的4个观测站开展了太阳辐射（光合有效辐射PAR、可见光辐射VIS、总辐射Q等）、气象参数等的综合测量,得到了PAR、VIS等的变化特征,结果表明：PAR/Q、VIS/Q、PAR/VIS相对稳定,有明显的日、逐日和季节变化,并受到水汽、散射因子、云等因素的影响。2004—2006年禹城、栾城、香河、兴隆地区VIS/Q,PAR/Q和PAR/VIS的平均值分别为0.39,1.95 mol/MJ和4.97 mol/MJ;0.39,1.94 mol/MJ和4.95 mol/MJ;0.43,2.16 mol/MJ和4.97 mol/MJ;0.42,2.03 mol/MJ和4.89 mol/MJ。建立了计算华北地区实际天气PAR、VIS小时累计值的经验公式及PAR与VIS转换关系式,计算值与观测值符合得都比较好。考虑水汽和散射因子时,PAR、VIS计算值与观测值的相对偏差分别为13.0%、12.4%。由于某些站点可能缺少直接或散射辐射,也可以只考虑水汽因子,此时,PAR、VIS的相对偏差分别为13.2%、12.8%。对于PAR、VIS的传输和计算来说,水汽因子的作用最为重要;散射因子的作用虽弱于水汽因子,但也不应该忽视。  相似文献   

12.
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   

13.
The solar and longwave environmental irradiance geometry (SOLWEIG) model simulates spatial variations of 3-D radiation fluxes and mean radiant temperature (T mrt) as well as shadow patterns in complex urban settings. In this paper, a new vegetation scheme is included in SOLWEIG and evaluated. The new shadow casting algorithm for complex vegetation structures makes it possible to obtain continuous images of shadow patterns and sky view factors taking both buildings and vegetation into account. For the calculation of 3-D radiation fluxes and T mrt, SOLWEIG only requires a limited number of inputs, such as global shortwave radiation, air temperature, relative humidity, geographical information (latitude, longitude and elevation) and urban geometry represented by high-resolution ground and building digital elevation models (DEM). Trees and bushes are represented by separate DEMs. The model is evaluated using 5?days of integral radiation measurements at two sites within a square surrounded by low-rise buildings and vegetation in G?teborg, Sweden (57°N). There is good agreement between modelled and observed values of T mrt, with an overall correspondence of R 2?=?0.91 (p?<?0.01, RMSE?=?3.1?K). A small overestimation of T mrt is found at locations shadowed by vegetation. Given this good performance a number of suggestions for future development are identified for applications which include for human comfort, building design, planning and evaluation of instrument exposure.  相似文献   

14.
利用2005年7月-2006年10月在山东禹城对太阳辐射（包括光合有效辐射PAR、可见光辐射VIS、总辐射Q等）、气象要素等进行的4次综合观测资料,初步得到了朋R,VIS的日、季节变化特征并对其进行了分析,结果表明：各辐射的小时累计之比vIS／Q,PAR／Q,PAR／VIS相对稳定,其平均值分别为0．39,1．95（mol／MJ）,4．97（mol／MJ）,但它们均有明显的日、逐日、季节变化,并受水汽、气溶胶、云等因素的影响。同时建立了实际天气PAR,VIS的小时累计经验公式及其转换关系,计算值与观测值均比较接近。当考虑水汽和散射因子时,PAR,VIS的计算值与观测值的相对偏差分别为11．1％,10．6％。限于实际情况,可以只考虑水汽因子的作用来计算PAR和VIS的小时累计值,它们的相对偏差分别为13．3％,12．6％。水汽因子对于PAR,VIS的传输和计算具有重要作用。  相似文献   

15.
Accurate estimates of photosynthetically active radiation (PAR) are critical for the development of realistic models of plant productivity. However, in many areas such as the vast Amazon region of South America, there have been few empirical studies of PAR. Here, we analyzed the relationship between PAR and broadband solar irradiance (R s) and formulated models to estimate PAR in two experimental sites (pasture and forest) in the Brazilian Amazon. Three different models of increasing complexity were developed based on information from R s (model 1), R s and clearness index (k t; model 2), and R s, k t, and water vapor pressure (model 3). Estimates of PAR were generated for each season and for the entire year. All models had very high determination coefficients and indices of agreement for both pasture and forest sites. This strongly supports the use of R s and k t to produce robust estimates of PAR. The results obtained by annual models were close than that found by seasonal models, demonstrating that a single annual model is able to estimate PAR, albeit with lower accuracy.  相似文献   

16.
Measurements of the broadband global solar radiation (R S) and total ultraviolet radiation (the sum of UV-A and UV-B) were conducted from 2005 to 2010 at 9 sites in arid and semi-arid regions of China. These data were used to determine the temporal variability of UV and UV/R S and their dependence on the water vapor content and clearness index. The dependence of UV/R S on aerosol optical depth (AOD) and water vapor content was also investigated. In addition, a simple and efficient empirically model suited for all-weather conditions was developed to estimate UV from R s. The annual average daily UV level in arid and semi-arid areas is 0.61 and 0.59 MJ m?2 d?1, respectively. The highest value (0.66?±?0.25 MJ m?2 d?1) was recorded at an arid area at Linze. The lowest value (0.53?±?0.22 MJ m?2 d?1) was recorded at a semi-arid area at Ansai. The highest daily value of UV radiation was measured in May, whereas the lowest value was measured in December. The monthly variation of the UV/R s ratio ranged from 0.41 in Aksu to 0.35 in Qira. The monthly mean value of UV/R s gradually increased from November and then decreased in August. A small decreasing trend of UV/R s was observed in the arid and semi-arid regions due to recently increasing amounts of fine aerosol. A simple and efficient empirically model suit for all-weather condition was developed to estimate UV from R s. The slope a and intercept b of the regression line between the estimated and measured values were close to 1 and zero, respectively. The relative error between the estimated and measured values was less than 11.5%. Application of the model to data collected from different locations in this region also resulted in reasonable estimates of UV.  相似文献   

17.
Emissions of biogenic volatile organic compounds (BVOC) were measured using a relaxed eddy accumulation (REA) technique on an above-canopy tower in a temperate forest (Changbai Mountain, Jilin province, China) during the 2010 and 2011 summer seasons. Solar global radiation and photosynthetically active radiation (PAR) were also measured. Based on PAR energy dynamic balance, an empirical BVOC emission and PAR transfer model was developed that includes the processes of BVOC emissions and PAR transfer above the canopy level, including PAR absorption and consumption, and scattering by gases, liquids, and particles (GLPs). Simulated emissions of isoprene and monoterpenes were in agreement with observations. The averages of the relative estimator biases for the flux were 39.3 % for isoprene, and 27.1 % for monoterpenes in the 2010 and 2011 growing seasons, with NMSE (normalized mean square error) values of 0.133 and 0.101, respectively. The observed and simulated mean diurnal variations of isoprene and monoterpenes in the 2010 and 2011 growing seasons were evaluated for the validation of the empirical model. Under observed atmospheric conditions, the sensitivity analysis showed that emissions of isoprene and monoterpenes were more sensitive to changes in PAR than to water vapor content or to the magnitude of the scattering factor. The emissions of isoprene and monoterpenes in the 2010 and 2011 growing seasons (from June to September) were estimated using this empirical model along with hourly observational data, with mean hourly emissions of 1.71 and 1.55 mg m?2 h?1 for isoprene, and 0.48 and 0.47 mg m?2 h?1 for monoterpenes in 2010 and 2011, respectively. As formaldehyde (HCHO) is considered as the main oxidation product of isoprene and monoterpenes, it is necessary to investigate the link between HCHO and BVOC emissions. GOME-2 HCHO vertical column densities (VCDs) can be used to estimate BVOC emission fluxes in the Changbai Mountain temperate forest.  相似文献   

18.
兴隆地区光合有效辐射计算方法   总被引：1，自引：0，他引：1  
白建辉  王庚辰 《气象科技》2009,37(4):472-477
2005年9月11日至2006年9月2日,在河北省兴隆县对太阳辐射（光合有效辐射SPAN、可见光辐射SVIS、总辐射Q等）、气象参数进行了4次综合观测,初步得到了SAR、SVIS等的变化特征。小时累计之比SPAN／Q、SVIS／Q、SPAR／SVIS。相对稳定,其平均值分别为2．03mol／MJ、0．42、4．89mol／MJ,同时它们都表现出明显的日、逐日、季节变化特征,并受到水汽、气溶胶、云等因素的影响。建立了实际天气计算SPAR、SVIS的经验公式及SPAR与SVIS转换关系式,计算值与观测值符合得较好。在考虑水汽和散射因子时,SPAR、SVIS计算值与观测值的相对偏差分别为13．3％、12．1％。限于实际情况,也可以只考虑水汽因子,此时,SPAR和SVIS的相对偏差分别为13．8％、12．4％。对于SPAR、SVIS的传输和计算来说,水汽因子具有重要作用,气溶胶因子的作用虽弱于水汽因子,但仍需考虑。  相似文献   

19.
The present study deals with the aerosol optical properties which are assessed during the period 2007 to 2009 over Mohal (31.9oN, 77.12oE) in the northwestern Indian Himalaya, using ground-based measurements and multi-satellite data. The daily average value of aerosol optical depth (AOD) at 500?nm, ?ngstr?m exponent and turbidity coefficient are 0.24?±?0.08, 1.02?±?0.34 and 0.13?±?0.05, respectively. The comparative study of satellite and ground-based measurements reveals that the percentage retrieval for daily AOD at 550?nm over Mohal within the expected accuracy (???? p?? ?=?±0.05?±?0.15?? p?? ) is around 87%, with a significant correlation coefficient of 0.76. The present study suggests that the retrieval of AOD through satellite data is able to characterise the distribution of AOD over Mohal. However, further efforts are needed in order to eliminate systematic errors in the existing Moderate Resolution Imaging Spectroradiometer (MODIS) algorithm. The transport of desert dust and anthropogenic aerosol during high aerosol loading days caused a significant reduction in surface-reaching solar radiation by 149 and 117%, respectively. This large reduction in surface-reaching solar radiation increased the atmospheric heating rate by 0.93 and 0.72?K?day?1, respectively. This study indicates significant climatic implications due to the transport of aerosols in the northwestern Indian Himalaya.  相似文献   

20.
Measurements of broadband global solar and ultraviolet radiation (UV-KZ) by a Kipp & Zonen radiometer from 2005 to 2011 at three sites in the background region over Northeast China were used to investigate the characteristics of the temporal variability of UV-KZ radiation in Northeast China. The highest annual mean daily values of UV-KZ (0.53 MJ m?2 d?1) were observed at Sanjiang and Changbai Mountain. The lowest value (0.49 MJ m?2 d?1) was measured at Hailun due to the high aerosol burden and the long path of solar radiation. The diurnal variation in UV-KZ radiation on four clear days near the equinoxes and solstices exhibited bell-shaped curves, with a maximum at approximately noon. There was little difference in UV-KZ radiation between representative spring and autumn days except that the amount of UV-KZ radiation during the spring was higher than that during the autumn. The relationship between the maximum values of UV-KZ radiation and clearness index can be accurately demonstrated with three polynomial equations. An empirical estimation model suited for all weather conditions was developed using measurements collected at Hailun. The slope of the linear regression between the measured and modeled UV-KZ radiation was approximately 1, the intercept of the linear regression equation was near zero, and the relative error of the equation was less than 8.5 %. These validation results suggest that this model can accurately estimate the UV-KZ radiation based on more conventional measured radiation data. The empirical estimation model can also serve as a valuable method for the study of ecological processes in other regions.  相似文献   

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