Spatial Distribution Of Solar Radiation Research Articles

일사 관측 자료에 의한 남한의 태양복사 시공간 분포

이 연구는 남한지역의 시 공간 태양복사 분포를 분석하는 것이다. 2000년 1월부터 2007년 8월 까지 1분 간격으로 저장된 기상청 관할 22개 관측소의 전천일사 관측자료를 이용하였다. 수집한 일사량 관측자료는 시간에 대하여 변화하는 일사계 감도정수에 대한 불확실성을 제거하기 위하여 비교관측 결과와 태양복사 모델을 이용하여 보정을 하였다. 보정을 수행하기 위하여 강릉대학교 전천일사계를 22개 관측소의 일사계와 2007년 8월 동안 비교 관측을 하였다. 과거자료는 맑은 날에 대하여 태양복사 모형을 이용하여 시간에 대해 감소하는 일사계의 감도정수를 토대로 보정하였다. 모든 지점 및 모든 기간에 대한 평균은 13.31 MJ/day이며 보정을 통하여 13.75 MJ/day가 되어 0.44 MJ/day의 차이가 나타났다. 보정된 자료로 계절평균 및 연평균 태양복사 분포를 계산하였으며 전운량, 오존전량, 에어로솔 광학 두께, 지표면 알베도, 가강수량과 관계성을 분석하였다. 가장 큰 영향을 미치는 전운량 자료를 보정된 자료와 비교한 결과 과거(원시)자료보다 일관성이 더 높게 나타났다. This study is to analyze the temporal and spatial distributions of solar radiation in South Korea. Solar radiation data is observed every minute at 22 KMA (Korea Meteorological Administration) stations using pyranometer from January 2000 to August 2007. These data were calibrated using intensive comparative observation and solar radiation model. Intensive comparative observations are accomplished at 22 KMA stations between KNU (Kangnung (Gangneung-Wonju) National University) standard and station instruments during the month of August 2007. The solar radiation of a clear sky mainly is affected by precipitable water, solar altitude and geological height. Also old (raw) data is corrected by the solar radiation model only about clear day and is revised based on the temporal trend of instrument's sensitivity decrease. At all periods and all stations, differences between raw data (13.31 MJ/day) and corrected data (13.75 MJ/day) are 0.44 MJ/ day. So, the spatial distribution of solar radiation is calculated with seasonal and annual mean, and is the relationship with cloud amount is analyzed. The corrected data show a better consistency with the cloud amount than the old data.

Monte Carlo simulation of solar radiation in maize canopies and its visualisation

The spatial distribution of solar radiation casts important influences on eco‐physiological functions of plant canopies. A simulation model of the three‐dimensional (3D) effect of direct and indirect solar radiation in real maize canopies is developed from measured 3D canopy structure meshes. The model includes two procedures: parallel direct light pass and diffusive indirect radiation pass. The former one is based on the Monte Carlo ray tracing algorithm. After enough ray casting, the radiation is obtained. Then, the diffusive indirect radiation pass uses a modified Monte Carlo radiosity model to evaluate the diffusion distribution. Results indicate that simulated sun fleck ratio is significantly consistent with the measured dataset.

Global and diffuse solar irradiances in urban and rural areas in southeast Brazil

The seasonal evolution of daily and hourly values of global and diffuse solar radiation at the surface are compared for the cities of Sao Paulo and Botucatu, both located in Southeast Brazil and representative of urban and rural areas, respectively. The comparisons are based on measurements of global and diffuse solar irradiance carried out at the surface during a six year simultaneous period in these two cities. Despite the similar latitude and altitude, the seasonal evolution of daily values indicate that Sao Paulo receives, during clear sky days, 7.8% less global irradiance in August and 5.1% less in June than Botucatu. On the other hand, Sao Paulo receives, during clear sky days, 3.6% more diffuse irradiance in August and 15.6% more in June than Botucatu. The seasonal variation of the diurnal cycle confirms these differences and indicates that they are more pronounced during the afternoon. The regional differences are related to the distance from the Atlantic Ocean, systematic penetration of the sea breeze and daytime evolution of the particulate matter in Sao Paulo. An important mechanism controlling the spatial distribution of solar radiation, on a regional scale, is the sea breeze penetration in Sao Paulo, bringing moisture and maritime aerosol that in turn further increases the solar radiation scattering due to pollution and further reduces the intensity of the direct component of solar radiation at the surface. Surprisingly, under clear sky conditions the atmospheric attenuation of solar radiation in Botucatu during winter – the biomass burning period due to the sugar cane harvest – is equivalent to that at Sao Paulo City, indicating that the contamination during sugar cane harvest in Southeast Brazil has a large impact in the solar radiation field at the surface.

Spatial Distribution of Solar Radiation and Its Effects on Vine Phenology and Grape Ripening in an Alpine Environment

Climate, soil, and vineyard performance were characterized in the northern Italian alpine valley of Valtellina to develop an ecophysiological model for zoning viticultural aptitude of the district. Based on a representative sample of 54 small, steep-sloped terraced vineyards planted with the late-ripening red cv. Nebbiolo, the model included three-year (1998 to 2000) data sets for phenology, maturity curves, yield, vigor, and grape assays, with appropriate indices to manage these sets. Soils were characterized by pedological description and climate by annual values of potential photosynthetically active radiation (PPAR) and estimated thermal fields expressed as growing degree days (GDD) using base 10°C. PPAR ranged from 2700 to 3200 MJm^-2year^-1 and GDD ranged from 1100 to 1800. Vineyards showed a 12-day range in phenological timing, with early sites having the highest technological maturity and medium sites having the highest phenolic maturity. Elevation and PPAR were the main environmental factors affecting vine budbreak and bloom date; veraison was also affected by crop load and its interaction with PPAR availability. Technological maturity was affected by elevation; phenolic maturity by crop load, PPAR, and its interaction with crop load and elevation. The highest phenolic maturity was recorded in low-cropping vineyards at low elevation and PPAR.

East African climate change and orbital forcing during the last 175 kyr BP

Variations in the temporal and spatial distribution of solar radiation caused by orbital changes provide a partial explanation for the observed long-term fluctuations in African lake levels. The understanding of such relationships is essential for designing climate-prediction models for the tropics. Our assessment of the nature and timing of East African climate change is based on lake-level fluctuations of Lake Naivasha in the Central Kenya Rift (0°55′S 36°20′E), inferred from sediment characteristics, diatoms, authigenic mineral assemblages and 17 single-crystal 40Ar/ 39Ar age determinations. Assuming that these fluctuations reflect climate changes, the Lake Naivasha record demonstrates that periods of increased humidity in East Africa mainly followed maximum equatorial solar radiation in March or September. Interestingly, the most dramatic change in the Naivasha Basin occurred as early as 146 kyr BP and the highest lake level was recorded at about 139–133 kyr BP. This is consistent with other well-dated low-latitude climate records, but does not correspond to peaks in Northern Hemisphere summer insolation as the trigger for the ice-age cycles. The Naivasha record therefore provides evidence for low-latitude forcing of the ice-age climate cycles.

ESTIMATING TRANSPIRATION OF APPLE TREE BRANCHES FROM LEAF STOMATAL CONDUCTANCE MEASUREMENTS - A FIRST ASSESSMENT OF RATP MODEL ON APPLE TREES

The aim of this study was to estimate water flux of apple tree branches, from measurements of transpiration and stomatal conductance, made at the leaf scale. For this purpose, we used the model RATP (Radiation Absorption, Transpiration and Photosynthesis) which simulates the spatial distribution of solar radiation and leaf-gas exchange within tree crowns as a function of canopy structure, microclimate within the canopy and physical and physiological leaf properties. In the present application, the model was used to estimate the transpiration of branches, at one-hour time steps and model outputs were compared with field measurements. Field measurements were carried out on six-year-old trees of 'Fuji'. Two trees were digitised and, on each tree, two branches were selected in eastern and western parts of the crown, respectively. Their transpiration was measured at ten minute intervals with sapflow sensors. Stomatal conductance was measured with a portable photosynthesis system LICOR 6200, on leaves sampled on similar trees of the same plot. Global and diffuse radiation were collected in the field while temperature and relative humidity were recorded at a near by meteorological station. At the branch scale, the measured transpiration was highly correlated to air temperature and air vapour pressure deficit (VPD). On the contrary, a poor correlation was found between the stomatal conductance of individual leaves and these climatic factors. A first assessment of RATP, was done by comparing estimated and measured transpiration rates on one tree, for three successive days with differing climatic conditions. The transpiration rates, estimated at one hour time steps, were consistent with the climatic conditions and followed the variations of PAR. But, the model over-estimated transpiration, in particular during the morning and for the most sunny days. These results appear to indicate a weakness of the sub-model for modelling stomatal regulation of apple tree and in the climatic data measurements.

Response of the East African climate to orbital forcing during the last interglacial (130–117 ka) and the early last glacial (117–60 ka)

Variations in the temporal and spatial distribution of solar radiation caused by changes in Earth9s orbit provide a partial explanation for observed long-term fluctuations in African lake levels. The understanding of causal links between insolation changes and lake- level fluctuations is essential for the design of models predicting future changes in the hydrological budgets and water supply in Africa. Here we present a record of climate change in East Africa between 175 and 60 ka. This time span includes the last interglacial (the Eemian, 130–117 ka), which may provide the closest analogue to the present interglacial. Assessments of the nature and timing of East African climate changes are based on lake-level fluctuations of Lake Naivasha (Kenya) inferred from sediment characteristics, diatom assemblages, and 40 Ar/ 39 Ar dating. Our results show dramatic alternation between deep, freshwater and shallow, highly alkaline lake conditions. The Lake Naivasha record demonstrates that periods of increased humidity in East Africa mainly follow precessional insolation forcing in spring, causing more intense April–May rains every 23 k.y.

Technical note On the development of spatial⧸temporal solar radiation maps: a Brazilian case study

This work summarizes recently published information on the solar resource of Brazil. We describe the spatial distribution of solar radiation and its relationship with climatic and geographical conditions. In order to harmonize the information in terms of type of instruments, time recording period and data processing methods, a careful selection of records from the data base was made. Density of recording stations is reasonable in the south, southeast and northeast regions of the country, while in the west center and north regions the density of stations is rather poor. The procedure to elaborate the maps of daily solar radiation, monthly and annual average is described. Consideration of the measuring period of the monthly averages, used to elaborate the contour maps, shows that they meet the requirement that 90% of averages are inside the strip of ±7.5%, centralized on the average of very long period measurements. We present one map with the localization of the recording stations and one annual and 12 monthly contour maps, describing daily solar radiation levels over the whole territory. Spacing among the contour lines is (±2 MJ⧸m 2 day). Annual average of solar radiation lies within the interval of ((18±2) MJ⧸m 2 day), except in the northeast region where values higher than (20 MJ⧸m 2 day) are found. Two regions with levels of (16 MJ⧸m 2 day) are also observed. The highest monthly average values (24 MJ⧸m 2 day) are observed in the state of Rio Grande do Sul, southern end of the country, in the summer season (December and January). The lowest values in the country (8 MJ⧸m 2 day) are observed in June and July (winter in the southern hemisphere), on the extreme south coastline of the same state, Rio Grande do Sul, below 32° south latitude.

NEW APPROACH TO ESTIMATING SOLAR RADIATION FROM SATELLITE IMAGERY∗

A significantly less expensive but comparatively accurate means of estimating solar radiation from satellite imagery is demonstrated. Opaque cloud cover is visually extracted from nondigitized, photographic forms of GOES satellite imagery and solar radiation is estimated using this information as input into a relatively simple solar model. Daily root mean square, mean absolute and mean bias errors were 13.2, 8.6 and 1.1 percent, respectively. Maps of the spatial distribution of solar radiation for Arizona are included.

The estimation of daily, clear sky, solar radiation intercepted by a tilted surface

The amount of solar energy that is intercepted by surfaces of any orientation is estimated from a new model of the clear sky, spatial distribution of solar radiation. The model was developed from measurements made during clear sky conditions and uses direct, isotropic reflected, and anisotropic diffuse radiation. The effects of azimuth, tilt, season, latitude, atmospheric turbidity, and reflectivity of the surroundings were computed using hourly measurements of normal beam and horizontal total radiation at four stations in the United States. A transformation of the co-ordinates of orientation produced a general relationship between orientation and intercepted energy. The general relationship was tested against measurements from six locations in the Northern Hemisphere and was found to be valid. The model is also a better estimator of energy intercepted by a tilted surface than are the more commonly used models.