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1.
In order to study energy and water cycles in the Huaihe River Basin, micrometeorological measurements were carried out in Shouxian County, Anhui Province, during HUBEX/IOP (May to August 1998 and June to July 1999). The employed techniques included Bowen Ratio-Energy Balance (BREB) and Eddy Covariance (EC) methods. In this paper, the basic characteristics of the energy balance components in the district are analyzed. Furthermore, the results are compared with those from other regions of China.The main results are as follows: (1) There was a consistency between the available energy (Rn-G) and the sum of sensible (H) and latent (E) heat fluxes measured by the EC method (H+E)ec, but Ebr was slightly larger (about 10%) than Eec; (2) Most of the net radiation (Rn) was used to evaporate water from the surface. During HUBEX/IOP in 1998 and 1999, the mean daily amounts of Rn were 13.89 MJ m-2 d-1 and 11.83 MJ m-2 d-1, and the mean Bowen Ratios (β) were 0.14 (over ruderal) and 0.06 (over paddy) respectively; (3) The diurnal variation characteristic of β was larger and unsteady at sunrise and sunset, and smaller and steady during the rest of the daytime. Local advection appeared in the afternoon over paddy areas in 1999; (4) In comparison with the results from other regions of China, the nean β was the lowest (0.06) over paddy areas in the Huaihe River Basin and the highest (0.57) during June-August 1998 in Inner Mongolia grassland. The Bowen Ratio β is mainly related to the soil humidity.  相似文献   

2.
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   

3.
Summary  Surface radiative fluxes play a major role in the energy exchange process between the atmosphere and earth surface and are thus very crucial to climatic processes within the atmospheric boundary layer. Based on four years REKLIP (REgio-KLIma-Project) data set of measured radiative fluxes and additional supporting meteorological variables, the surface radiation regime for selected lowland site (Bremgarten 212 m a.s.l.) and mountain sites (Geiersnest at 870 m a.s.l.; Feldberg 1489 m a.s.l.) in the southern Upper Rhine valley region (south-west Germany) has been reported. Time series of radiative fluxes and surface albedo showed significant inter-site differences. Possible reasons for the observed differences have been made. Downward atmospheric radiation A l at the study sites was parameterised in terms of air temperature, vapour pressure and cloud amount, all of which strongly govern the variation of A l . Effective terrestrial radiation amounted to about 50% of absorbed shortwave radiation at the study sites annually. During clear sky conditions, global solar irradiance G s constituted about 76.0% of the incident extraterrestrial solar irradiance at Feldberg mountain site but only 68.5% of that at Bremgarten lowland site. Annual cumulative of net radiative flux R n amounted to 1722 MJm−2 yr−1 at the lowland site, while that at Geiersnest and Feldberg mountain sites constituted 84% and 73% respectively of the corresponding magnitude for the lowland site. In the same vein, annual mean of radiation efficiency (defined here as R n /G s ) amounted to 0.32 in Feldberg, 0.37 in Geiersnest and 0.41 in Bremgarten. Consequently the annual available energy, of which net radiative flux is representative, was smaller at the mountain ous sites relative to the lowland site during the study period. Inter-annual variability of net radiative flux, its constituent variables and derivatives at the study sites were generally below 10%, with longwave fluxes showing the lowest fluctuation. This renders the measured data quite suitable for modelling purposes. In winter, mean daily sums of R n showed a slow rise with cloud amount N at the lowland site but a sharp rise with N at Feldberg mountain site. In summer however, mean daily sums of R n declined significantly with N as well as Linke turbidity factor at the study sites. Received June 24, 1999 Revised November 2, 2000  相似文献   

4.
Global radiation is an important parameter necessary for most ecological models. However, in situ data barely meets the needs of modelling mountainous ecosystems since most field stations are located in flat areas. Consequently, it is usually necessary to extrapolate radiation measurements obtained from an adjacent flat area to the complex terrain of concern. The distribution of radiation in complex terrain depends upon two factors: the local atmospheric conditions, which determine the radiation potentially available to a supposed flat surface in a given location, and the topographic effects on this possible radiation. The latter have been included in detail in most radiation models for complex terrain, but the former are often only simply treated as constant or estimated by over-simplified empirical algorithms. In this paper we propose a novel model that uses a parametric atmospheric model to calculate the potential radiation for a supposed flat surface in a given location, and then account for topographic effects. Direct radiation, diffuse radiation and reflected radiation are calculated separately in the model due to the distinctive characteristics of and the effects by topography. Based on the parametric model, this paper has investigated the relationship between radiation transmittance, clearness indices and altitude under a series of water vapour content and turbidity conditions. This combines three ratios, R b, R d, and R r, defined as the direct radiation, diffuse radiation and reflected radiation received by the arbitrary surface, respectively, to their counterparts in the horizontal surface, to estimate the global radiation for any given location. The model has been validated with data from measurements in National Park Berchtesgaden, Germany, where six measurement sites with various altitudes and topographic characteristics have been deployed. The r 2 of modelled and measured hourly global radiation are greater than 0.90 in all six sites, with RMSE varies from 16 to 100 W m−2. Sensitivity analysis revealed that the model was not sensitive to change in water vapour content, which suggests the possibility to use an exponential algorithm of water vapour content when there is no in situ water vapour content information in complex terrains. The NRMSE was only reduced by 0.04, on average, in five of the six sites when water vapour content information was calculated from the in situ air temperature and relative humidity measurements.  相似文献   

5.
Summary  Net ecosystem CO2 exchange was measured over a mountain birch forest in northern Finland throughout the growing season. The maximal net CO2 uptake rate of about − 0.5 mg(CO2) m−2 s−1 was observed at the end of July. The highest nocturnal respiration rates in early August were 0.2 mg(CO2) m−2 s−1. The daily CO2 balances during the time of maximal photosynthesis were about −15 g(CO2) m−2 d−1. The mountain birch forest acted as a net sink of CO2 from 30 June to 28 August. During that period the net CO2 balance was −448 g(CO2)m−2. The interannual representativeness of the observed balances was studied using a simplified daily balance model, with daily mean global radiation and air temperature as the input parameters. The year-to-year variation in the phenological development was parameterised as a function of the cumulative effective temperature sum. The daily balance model was used for estimating the variability in the seasonal CO2 balances due to the timing of spring and meteorological factors. The sink term of CO2 in 1996 was lower than the 15-year mean, mainly due to the relatively late emergence of the leaves. Received October 11, 1999 Revised April 25, 2000  相似文献   

6.
Previous measurements of urban energy balances generally have been limited to densely built, central city sites and older suburban locations with mature tree canopies that are higher than the height of the buildings. In contrast, few data are available for the extensive, open vegetated types typical of low-density residential areas that have been newly converted from rural land use. We made direct measurements of surface energy fluxes using the eddy-covariance technique at Greenwood, a recently developed exurban neighbourhood near Kansas City, Missouri, USA, during an intensive field campaign in August 2004. Energy partitioning was dominated by the latent heat flux under both cloudy and near clear-sky conditions. The mean daytime Bowen ratio (β) values were 0.46, 0.48, and 0.47 respectively for the cloudy, near clear-sky and all-sky conditions. Net radiation (R n ) increased rapidly from dawn (−34 and −58W m−2) during the night to reach a maximum (423 and 630W m−2) after midday for cloudy and near clear-sky conditions respectively. Mean daytime values were 253 and 370W m−2, respectively for the cloudy and near clear-sky conditions, while mean daily values were 114 for cloudy and 171W m−2 for near clear-sky conditions, respectively. Midday surface albedo values were 0.25 and 0.24 for the cloudy and near clear-sky conditions, respectively. The site exhibited an angular dependence on the solar elevation angle, in contrast to previous observations over urban and suburban areas, but similar to vegetated surfaces. The latent heat flux (Q E ), sensible heat flux (Q H ), and the residual heat storage ΔQ s terms accounted for between 46–58%, 21–23%, and 18–31% of R n , respectively, for all-sky conditions and time averages. The observed albedo, R n , and Q E values are higher than the values that have been reported for suburban areas with high summer evapotranspiration rates in North America. These results suggest that the rapidly growing residential areas at the exurban fringe of large metropolitan areas have a surface energy balance that is more similar to the rural areas from which they were developed than it is to the older suburbs and city centres that make up the urban fabric to which they are being joined.  相似文献   

7.
Esmaiel Malek   《Atmospheric Research》2008,88(3-4):367-380
An automated-ventilated radiation station has been set up in a mountainous valley at the Logan Airport in northern Utah, USA, since mid-1995, to evaluate the daily and annual radiation budget components, and develop an algorithm to study cloudiness and its contribution to the daily and annual radiation. This radiation station (composed of pyranometers, pyrgeometers and a net radiometer) provides continuous measurements of downward and upward shortwave, longwave and net radiation throughout the year. The surface temperature and pressure, the 2-m air temperature and humidity, precipitation, and wind at this station were also measured. A heated rain gauge provided precipitation information. Using air temperature and moisture and measured downward longwave (atmospheric) radiation, appropriate formula (among four approaches) was chosen for computation of cloudless-skies atmospheric emissivity. Considering the additional longwave radiation during the cloudy skies coming from the cloud in the waveband which the gaseous emission lacks (from 8–13 μm), an algorithm was developed which provides continuous 20-min cloud information (cloud base height, cloud base temperature, percent of skies covered by cloud, and cloud contribution to the radiation budget) over the area during day and night. On the partly-cloudy day of 3 February, 2003, for instance, cloud contributed 1.34 MJ m− 2 d− 1 out of 26.92 MJ m− 2 d− 1 to the daily atmospheric radiation. On the overcast day of 18 December, 2003, this contribution was 5.77 MJ m− 2 d− 1 out of 29.38 MJ m− 2 d− 1. The same contribution for the year 2003 amounted to 402.85 MJ m− 2 y− 1 out of 9976.08 MJ m− 2 y− 1. Observations (fog which yielded a zero cloud base height and satellite cloud imaging data) throughout the year confirmed the validity of the computed data. The nearby Bowen ratio station provided the downward radiation and net radiation data. If necessary, these data could be substituted for the missing data at the radiation station. While the automated surface observing systems (ASOS) ceilometer at the Logan airport provides only the overhead cloud information, the proposed algorithm provides this information over the valley. The proposed algorithm is a promising approach for evaluation of the cloud base temperature, cloud base height, percent of skies covered by cloud, and cloud contribution to the daily and annual radiation budget at local and regional scales.  相似文献   

8.
Rainfall variability and kinetic energy in Southern Nigeria   总被引：1，自引：1，他引：0  
A decreasing trend of rainfall has been observed in West Africa, where rainfall erosivity is also considered to be high. Therefore, this study was carried out to evaluate the variability of rainfall and its erosivity in two contrasting zones in southern Nigeria between 1977 and 1999 to understand the implications of climate variability on rainfall erosivity. The study sites were Ibadan, a sub-humid zone, and Port-Harcourt, a humid zone. Time of occurrence of rainfall, rainfall amount (A), intensity (I 15 and I 30), kinetic energy (E) and rainfall erosivity factor (R), were evaluated. Kinetic energy was estimated with Brown–Foster (BF) equation, making the rainfall erosivity (product of kinetic energy and intensity) to be designated as EI 30-BF and EI 15-BF. The frequency of rainfall during daylight (06:00–18:00 h) was 48% for Ibadan and 69% for Port-Harcourt. There were time-specific differences in daily rainfall occurrence between the zones, suggesting a strong influence of local effects on rainfall generation, such as, relief in Ibadan and proximity to the sea in Port-Harcourt. Annual E was 213 MJ ha−1for Ibadan and 361 MJ ha−1 for Port-Harcourt. Ibadan had a significantly higher daily E than Port-Harcourt because of higher intensity while Port-Harcourt had significantly higher annual E than Ibadan because of higher annual rainfall amount. Annual erosivity at Ibadan using the EI 30-BF was 9,742 MJ mm ha−1 h−1 whereas it was 15,752 MJ mm ha−1 h−1 at Port-Harcourt. Using the EI 15-BF, Ibadan had an annual value of 14,806 MJ mm ha−1 h−1 while Port-Harcourt had 20,583 MJ mm ha−1 h−1. Thus, annual rainfall erosivity was significantly higher in the humid than the sub-humid zone because of higher amount of rainfall but the reverse was the case with daily erosivity because of higher intensities in the sub-humid zone. Rainfall intensity was, therefore, a key measure of erosivity. There was a strong positive relationship between rainfall erosivity and rainfall amount. Between 1977 and 1988, 50–88% of the 12 years had rainfall erosivity which exceeded the long-term average but rainfall erosivity was less than the long-term average between 1989 and 1999. This suggested a decreasing trend in erosivity due to the decreasing trend in rainfall amount in West Africa. However, the trend did not imply lesser soil erosion and environmental degradation risks.  相似文献   

9.
Summary  Turbulent fluxes of CO2 were continuously measured by eddy correlation for three months in 1997 over a gramineous fen in a high-arctic environment at Zackenberg (74°28′12″N, 20°34′23″W) in NE-Greenland. The measurements started on 1 June, when there was still a 1–2 m cover of dry snow, and ended 26 August at a time that corresponds to late autumn at this high-arctic site. During the 20-day period with snow cover, fluxes of CO2 to the atmosphere were small, typically 0.005 mg CO2 m−2 s−1 (0.41 g CO2 m−2 d−1), wheres during the thawed period, the fluxes displayed a clear diurnal variation. During the snow-free period, before the onset of vegetation growth, fluxes of CO2 to the atmosphere were typically 0.1 mg CO2 m−2 s−1 in the afternoon, and daily sums reached values up to almost 9 g CO2 m−2 d−1. After 4 July, downward fluxes of CO2 increased, and on sunny days in the middle of the growing season, the net ecosystem exchange rates attained typical values of about −0.23 mg m−2 s−1 at midday and max values of daily sums of −12 g CO2 m−2 d−1. Throughout the measured period the fen ecosystem acted as a net-sink of 130 g CO2 m−2. Modelling the ecosystem respiration during the season corresponded well with eddy correlation and chamber measurements. On the basis of the eddy correlation data and the predicted respiration effluxes, an estimate of the annual CO2 balance the calender year 1997 was calculated to be a net-sink of 20 g CO2 m−2 yr−1. Received October 6, 1999 Revised May 2, 2000  相似文献   

10.
利用1981、1996和2001年逐日南京站太阳总辐射和日照时数观测资料,建立了基于支持向量机(support vector machine,SVM)方法的太阳总辐射推算模型,预测了1982、1997和2002年的太阳总辐射,并把推算结果和采用线性的气候学方法所得到的推算结果分别与实测值进行对比。采用线性方法得到的1982、1997和2002年的太阳总辐射预测值与实测值间基于1:1线的决定系数(R~2)分别为0.800、0.859和0.838,均方根误差(RMSE)分别为3.250、2.649和2.925 MJ·m~(-2)·d~(-1)。采用SVM方法得到的1982、1997和2002年的R~2分别为0.894、0.938和0.936,RMSE分别为2.353、1.726和1.804 MJ·m~(-2)·d~(-1)。SVM方法得到的太阳总辐射预测值与实测值之间的误差较小,预测精度高于线性方法,更适用于实际太阳总辐射的计算。  相似文献   

11.
Ultraviolet （UV） solar radiation has a significant influence on human health, the environment and climate. A series of measurements, including UV radiation （290 400 nm） and global solar radiation （Rs）, were continuously recorded from August 2004 at the Lhasa and Haibei sites on the Tibetan Plateau. Both observation sites＇ altitudes are above 3000 m and have similar meteorological conditions. The data from 2005 2006 was used to identify the varying characteristics of UV radiation. It＇s relation to the clearness index Ks, the relative optical mass mr, and Rs were established. The annual mean values of total daily UV radiation are 0.92 and 0.67 MJ m^-2 at Lhasa and Haibei, respectively. The UV radiation in Lhasa represented 4.6% of the global solar radiation while in Haibei this percentage was 4.2%. In the case of clear days （Ks 〉 0.8）, these percentages ranged between 4.0% and 4.5% in Lhasa and between 5.1% and 5.5% in Haibei. In the case of cloudy days （Ks 〈 0.4）, these percentages ranged from 4.4% to 6.8% in Lhasa and from 5.1% to 5.5% in Haibei. The maximum values of UV radiation for each relative optical mass diminished exponentially with mr. Thus, for Lhasa and Haibei, UV=46.25mr-129, and UV=51.76mr-142, respectively. The results of this study can be used to obtain more UV radiation data for the study of UV climate characteristics, the effects of UV on ecological processes and the feedback of the thinning of the stratospheric ozone, from more routine measurements Rs data.  相似文献   

12.
Long-term comparisons of net radiation calculation schemes   总被引：1，自引：0，他引：1  
Six commonly used models for calculating daily net radiation were tested against measured net radiation. Meteorological data from 32 and 7 consecutive years obtained at two temperate sites were used. The extensive duration of the datasets ensured that all weather conditions and extreme events were captured. A set of statistical procedures was used to evaluate the performance of the models. The mean bias errors ranged from 0.0 W m−2 to 24.8 W m−2 and 0.1–24.7 W m−2 and root mean square error from 11.0 W m−2 to 28.1 W m−2 and 10.0–27.9 W m−2 at the two sites respectively, for days without snow cover on the ground. The best agreement was found when locally calibrated model coefficients were used. Only negligible differences in model performances were found between the two sites and the differences were lower than the inaccuracies of the net radiation instruments used. Including days with snow cover in the analysis lead to a slight increase in the bias and scatter of the predictions. Model performances were in general better during summertime than wintertime. Altered albedo values during winter caused by generally low sun angles were likely the cause of this. Analysis showed that at least 5 years of data were needed to obtain stable calibration coefficients for local calibration of the models. Based on the results from this study, and due to their physical background, two physical based models were recommended for calculating daily values of net radiation under temperate climate regimes. A simple adjustment of the calibration coefficients based on climate regime was suggested for these models.  相似文献   

13.
上海地区地面太阳紫外辐射的观测和分析   总被引：21，自引：0，他引：21  
通过对上海地区2001～2003年地面太阳总辐射和紫外辐射观测资料的分析表明：（1）上海地区太阳辐射和紫外辐射年总量分别为4487．1MJ／m^2和149．6MJ/m^2。（2）紫外辐射的季节变化特征十分明显，夏半年（4-9月）各月极大紫外辐射强度远大于冬半年（10月～次年3月），7月份最强，12月份最弱。（3）不同天气条件下，紫外辐射日变化显示出明显的差异，晴天强且稳定，多云天气波动较大，阴天则次之。（4）紫外辐射占总辐射的比例（η）也显示冬半年低，夏半年高的分布特征。（5）影响上海地区到达地面紫外辐射的主要因子有：太阳高度角的大小大致决定了到达地面紫外辐射的强弱，两者具有相近的年变化趋势；云、雨等天气类型是影响紫外辐射的重要因子；大气能见度对紫外辐射也有比较明显的影响。  相似文献   

14.
拉萨紫外辐射特征分析及估算公式的建立   总被引：2，自引：1，他引：1  
本文利用2005~2010年的辐射观测资料对拉萨地区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,结果表明,紫外辐射与太阳总辐射的变化规律基本一致,日变化表现为正午大、早晚小;季变化特征是夏季6月最大,冬季1月最小.紫外辐射日累积值6年平均为0.87 MJ·m-2·d-1;紫外辐射有逐年递减的趋势.紫外辐射与总辐射比值也存在着明显日变化,表现为正午大、早晚小的规律;其季节变化也是夏季最大,冬季最小.紫外辐射与总辐射比值6年平均为0.0418;紫外辐射与总辐射比值也呈现逐年递减的趋势.利用2010年大气质量数和晴空指数,建立了适合于拉萨紫外辐射估量的公式,估算值的瞬时值与观测值的平均相对误差最大为8.66%,紫外辐射日累积重构值与观测值平均相对误差仅为5.5%.  相似文献   

15.
Analysis of solar radiation over Egypt   总被引：1，自引：0，他引：1  
Summary  The database utilized in this analysis consisted of daily sunshine duration and hourly global and diffuse radiation on a horizontal surface (for Matruh Cairo, and Aswan), and normal incidence beam radiation (for Cairo and Aswan only). Monthly-average hourly and daily values are reported for each of these three types of measured radiation, together with the calculated monthly-average daily values for the components of global radiation, horizontal beam and diffuse radiation. The monthly-average hourly and daily clearsky index values have also been calculated and analyzed. Monthly-average daily frequency distributions of the clearsky index values are reported for each month. The annual-average daily global irradiation values are 19.4, 18.67, and 21.78 MJ/m2 and for diffuse irradiation they are 6.34, 6.65 and 6.23 MJ/m2 for Matruh, Cairo and Aswan, respectively. For the normal incidence beam irradiation the annual-average daily values are 16.94 and 24.46 MJ/m2 for Cairo and Aswan, respectively. The annual-average daily fractions of the direct component of horizontal global radiation are 0.70, 0.61 and 0.72 for the three stations, respectively. The annual-average daily values for the clearsky index are 0.585, 0.566, and 0.648, and the average frequency of clear days annually are 67.3, 42.3 and 77.6% respectively. The annual variations and trend analysis were analyzed for daily global, direct, and diffuse radiation on a horizontal surface, daily sunshine duration, and for the daily ratios G/G0, and D/G for the stations Matruh, Cairo and Aswan. The distribution of these components of radiation and their ratios over the study stations in Egypt is also discussed. The results show that Egypt is characterized by relatively high average-daily radiation rates, both global and direct, and a relatively high frequency of clear days. Cairo, due to its urbanization and high pollution, has relatively low average-daily radiation rates, particularly in direct radiation, and the frequency of clear days. Received February 26, 1998 Revised February 4, 1999  相似文献   

16.
The formation of dew, deposition of frost and accumulation of snow mainly on the upper domes of a non-ventilated net radiometer seriously affect the measurement of available energy (net radiation). Net radiometers measure radiation, and energy balances and are widely used for estimation of evapotranspiration throughout the world. To study the effects of dew, frost, and snow on a non-ventilated net radiometer, a radiation station was set up which uses 2 CM21 Kipp & Zonen pyranometers (one inverted), 2 CG1 Kipp & Zonen pyrgeometers (one inverted), along with a Q7.1 net radiometer (Radiation & Energy Balance Systems, Inc.; REBS) in a semi-arid mountainous valley in Logan, Utah, U.S.A. The pyranometers and pyrgeometers were ventilated using 4 CV2 Kipp & Zonen ventilation systems. The net radiometer was not ventilated. The ventilation of pyranometers and pyrgeometers prevents dew and frost deposition and snow accumulation which otherwise would disturb measurements. All sensors were installed at about 3.0 m above the ground, which was covered with natural vegetation during the growing season (May–September). The incoming and outgoing solar or shortwave radiation, the incoming (atmospheric) and outgoing (terrestrial) longwave radiation, and the net radiation have been continuously measured by pyranometers, pyrgeometers and a net radiometer, respectively, since 1995. These parameters have been measured every 2 s and averaged into 20 min. To evaluate the effects of dew, frost, and snow, three days were chosen: 26 April 2004 with early morning dew, 6 January 2005 with an early morning frost, and the snowy day of 24 February 2005. Dew formation, frost deposition, and snow accumulation occurred mainly on the upper dome of the non-ventilated Q7.1 net radiometer on the related days, while the ventilated Kipp & Zonen system was free of dew, frost and snow. Net radiation measured by the non-ventilated net radiometer Rn,unvent. during dew and frost periods of the above-mentioned days was greater than ventilated ones Rn,vent. (− 0.2 MJ m− 2 vs. − 0.8 MJ m− 2 during almost 4 h on 26 April 2004, and − 0.2 MJ m− 2 vs. − 0.7 MJ m− 2 during almost 6.5 h on 6 January 2005). The reason for higher reading by the non-ventilated net radiometer during dew and frost periods was due to emission of additional longwave radiation from water and ice crystals formed mainly on the upper dome of the Q7.1 net radiometer. In contrast, during the snowy day of 24 February 2005, the Rn,unvent. was less than Rn,vent. (− 4.00 MJ m− 2 vs. 0.77 MJ m− 2, mainly from sunrise to sunset). The extremely low Rn,unvent. measured by the non-ventilated net radiometer on 24 February 2005 is due to blocking of the incoming solar radiation (mainly diffuse radiation) by the snow-covered upper dome.  相似文献   

17.
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   

18.
Global solar radiation (GSR) is essential for agricultural and plant growth modelling, air and water heating analyses, and solar electric power systems. However, GSR gauging stations are scarce compared with stations for monitoring common meteorological variables such as air temperature and relative humidity. In this study, one power function, three linear regression, and three non-linear models based on an artificial neural network (ANN) are developed to extend short records of daily GSR for meteorological stations where predictors (i.e., temperature and/or relative humidity) are available. The seven models are then applied to 19 meteorological stations located across the province of Quebec (Canada). On average, the root-mean-square errors (RMSEs) for ANN-based models are 0.33–0.54?MJ?m?2?d?1 smaller than those for the power function and linear regression models for the same input variables, indicating that the non-linear ANN-based models are more efficient in simulating daily GSR. Regionalization potential of the seven models is also evaluated for ungauged stations where predictors are available. The power function and the three linear regression models are tested by interpolating spatially correlated at-site coefficients using universal kriging or by applying a leave-one-out calibration procedure for spatially uncorrelated at-site coefficients. Regional ANN-based models are also developed by training the model based on the leave-one-out procedure. The RMSEs for regional ANN models are 0.08–0.46?MJ?m?2?d?1 smaller than for other models using the same input conditions. However, the regional ANN-based models are more sensitive to new station input values compared with the other models. Maps of interpolated coefficients and regional equations of the power function and the linear regression models are provided for direct application to the study area.  相似文献   

19.
利用2005~2011年共7年的太阳辐射观测资料对三江平原紫外辐射的时间变化规律及紫外辐射与总辐射比值的变化特征进行了分析,结果表明紫外辐射与总辐射的变化规律一致,日变化为正午大、早晚小;季节变化规律是夏季高、冬季低。紫外辐射日累积值的7年年平均值为0.53 MJ m–2 d–1。紫外辐射与总辐射比值存在着明显日、季节变化特征,日变化特征为正午大、早晚小,而季节变化与紫外辐射的季节变化一致也是夏季大、冬季小。紫外辐射与总辐射比值7年平均为0.0433。利用2011年观测的总辐射、紫外辐射数据,通过紫外辐射与总辐射比值和大气质量数与晴空指数的相互依赖关系,建立了适合于三江地区紫外辐射估算的方程。利用建立的估算方程估算的紫外辐射瞬时值和日累积值与观测值之间的平均相对误差最大分别为8.5%和6.1%。  相似文献   

20.
Aerosol and rain samples were collected between 48°N and 55°S during the KH-08-2 and MR08-06 cruises conducted over the North and South Pacific Ocean in 2008 and 2009, to estimate dry and wet deposition fluxes of atmospheric inorganic nitrogen (N). Inorganic N in aerosols was composed of ~68% NH4+ and ~32% NO3– (median values for all data), with ~81% and ~45% of each species being present on fine mode aerosol, respectively. Concentrations of NH4+ and NO3− in rainwater ranged from 1.7–55 μmol L−1 and 0.16–18 μmol L−1, respectively, accounting for ~87% by NH4+ and ~13% by NO3− of total inorganic N (median values for all data). A significant correlation (r = 0.74, p < 0.05, n = 10) between NH4+ and methanesulfonic acid (MSA) was found in rainwater samples collected over the South Pacific, whereas no significant correlations were found between NH4+ and MSA in rainwater collected over the subarctic (r = 0.42, p > 0.1, n = 6) and subtropical (r = 0.33, p > 0.5, n = 6) western North Pacific, suggesting that emissions of ammonia (NH3) by marine biological activity from the ocean could become a significant source of NH4+ over the South Pacific. While NO3− was the dominant inorganic N species in dry deposition, inorganic N supplied to surface waters by wet deposition was predominantly by NH4+ (42–99% of the wet deposition fluxes for total inorganic N). We estimated mean total (dry + wet) deposition fluxes of atmospheric total inorganic N in the Pacific Ocean to be 32–64 μmol m−2 d−1, with 66–99% of this by wet deposition, indicating that wet deposition plays a more important role in the supply of atmospheric inorganic N than dry deposition.  相似文献   

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