Total Net Radiation Research Articles

Thermal radiation components of the energy balance at the ground

This paper reports a study on the thermal radiation components of the energy balance on the ground. The atmospheric radiation was measured and correlated to the cloudiness and to air temperature and humidity at screen level. Hence the net thermal and the net total radiation were estimated in relation to the atmospheric conditions. The long-term averages of the atmospheric, net thermal and net total radiation fluxes, as well as their day-to-day and year-to-year variabilities, were studied and are predicted with data from Lisbon.

Frost risk mapping for landscape planning: A methodology

Minimum air temperatures were measured during three winters with a network of stations in open, undulating terrain. It was observed that the change in minimum air temperature with elevation could be predicted from mean nighttime windspeed, total nighttime net radiation loss and a hill-top reference minimum temperature. It was also found that the deviation of temperatures at individual sites could be predicted from a local terrain parameter which reflects the extent of cold air accumulations. Thus a methodology for frost risk mapping has been developed which is based on regional weather dataand local terrain analysis. This paper describes the model and illustrates the regional weather and terrain effects with three-dimensional block diagrams.

Radiation components over bare and planted soils in a greenhouse

The radiation components that comprise net total radiation, incoming and outgoing solar and longwave radiation were measured over bare and planted soils in a greenhouse at the Solar Energy Research Center, Baghdad, Iraq. Crop albedo values were calculated and net radiation related to solar radiation by regression analysis. This paper shows that the crop albedo was close to 0.25 when the greenhouse floor was completely covered. The crop reflection coefficient decreased markedly with higher solar elevation. Heating coefficient values were consistently positive and ranged between 0.18 and 0.41 during the growing season. The net radiation was strongly correlated to the incoming solar radiation inside the greenhouse. Incorporating albedo in the linear relationship between net and net shortwave radiation was unnecessary.

Relations between radiation fluxes of a greenhouse in semi-arid conditions

Measurements of global radiation, reflected radiation and net total radiation inside and outside the greenhouse were conducted in Fudhiliyah Agrometeorological Research Station during the period from 1 January to 30 April, 1987. From these measurements, several relationships were established. Linear regressions of hourly values of global radiation inside the greenhouse on hourly global radiation outside the greenhouse were fitted for each month of the recording period. The degree of fit was generally good ( r > 0.95). Net short-wave radiation inside the greenhouse showed strong dependence on the global inside radiation ( r = 0.998), also the net total radiation and global radiation inside the greenhouse correlate very strongly. From the above-mentioned relationships, it was found that the global, net short-wave and net total radiation could be successfully predicted when only global outside radiation is available. Using the linear regression equations correlating the above radiation parameters, albedo and heating coefficient were derived. Albedo showed strong dependence on solar altitude angle and period of day (forenoon and afternoon). Heating coefficients were consistently positive and their values varied between 0.10 and 0.393. Monthly average values of mean hourly night-time net long-wave radiation inside the greenhouse were −31, −32, −38 and −42 W m −2 for the months of January, February, March and April, respectively.

Summertime Radiation Balances of Clearcut and Shelterwood Slopes in Southwest Oregon

Abstract Measurements of incoming solar radiation, reflected solar radiation, net radiation, and outgoing longwave radiation were made on three clearcuts and below three shelterwood canopies in southwest Oregon. This dataset was used to characterize the radiation balance of reforestation sites. The fraction of incoming solar energy (K ↓) producing the near surface microclimate (i.e., the net radiation, Q*) was 0.5 ± 0.06 for all sites studied. This value is appreciably lower than commonly measured values of uncut forest (Q*/K ↓ = 0.7 to 0.9). Although Q*/K ↓ is the same for clearcuts and shelterwoods, shelterwood understories have smaller net radiation because the overstory partially intercepts incoming solar radiation. Shelterwood data also exhibit the expected decrease in longwave radiation loss at night. The major factor affecting site albedo in both shelterwoods and clearcuts was slashburning, which decreased albedo to 0.13 as compared to 0.21 for unburned sites. Net radiation for entire sites was estimated with a simple model to sum ground surface net radiation and shelterwood canopy net radiation. Model calculations suggest that harvested sites average a 36% reduction in total net radiation when compared to unharvested stands. Shelterwood understory environments are less harsh than clearcut environments because much of the total site net radiation is dissipated in the overstory canopy. The model is also used to estimate the effect of canopy density on net radiation below the canopy. For. Sci. 32(2):504-516.

Topoclimatic Studies of a High Arctic Plateau Ice Cap

AbstractMeteorological observations on and around a small, exposed plateau ice cap on north-eastern Ellesmere Island, N.W.T., Canada, were carried out in the northern summers of 1982 and 1983. The objective was to assess the effect of the ice cap on local climate as the melt season progressed. In 1982, seasonal net radiation totals were lowest on the ice cap and greatest at the site farthest from the ice cap. The ice-cap site received only 35% of net radiation totals on the surrounding tundra. This reflects a gradient in albedo; albedo changed most markedly away from the ice cap as the summer progressed. A thermal gradient was observed along a transect perpendicular to the ice-cap edge; this gradient was greatest at low levels (15 cm) and was maximized under cloud-free conditions. The “cooling effect” of the ice cap was less at the start of the ablation season than later. Low-level inversions occurred more frequently over the ice cap than over the snow-free tundra. Overall, melting degree days on the ice cap were only 40–65% of those on the adjacent tundra. A model of interactions between the atmosphere and a snow and ice cover, or a snow-free tundra/felsenmeer surface is proposed. Observations indicate that the ice cap has a cooling effect on the lower atmosphere relative to the adjacent snow-free tundra; this effect is absent when snow cover is extensive (as in 1983).

Topoclimatic Studies of a High Arctic Plateau Ice Cap

AbstractMeteorological observations on and around a small, exposed plateau ice cap on north-eastern Ellesmere Island, N.W.T., Canada, were carried out in the northern summers of 1982 and 1983. The objective was to assess the effect of the ice cap on local climate as the melt season progressed. In 1982, seasonal net radiation totals were lowest on the ice cap and greatest at the site farthest from the ice cap. The ice-cap site received only 35% of net radiation totals on the surrounding tundra. This reflects a gradient in albedo; albedo changed most markedly away from the ice cap as the summer progressed. A thermal gradient was observed along a transect perpendicular to the ice-cap edge; this gradient was greatest at low levels (15 cm) and was maximized under cloud-free conditions. The “cooling effect” of the ice cap was less at the start of the ablation season than later. Low-level inversions occurred more frequently over the ice cap than over the snow-free tundra. Overall, melting degree days on the ice cap were only 40–65% of those on the adjacent tundra. A model of interactions between the atmosphere and a snow and ice cover, or a snow-free tundra/felsenmeer surface is proposed. Observations indicate that the ice cap has a cooling effect on the lower atmosphere relative to the adjacent snow-free tundra; this effect is absent when snow cover is extensive (as in 1983).

Surface Radiation Budget from Satellites

In this paper, a brief summary is presented of ongoing work dealing with the derivation of the Surface Radiation Budget (SRB) from satellite observations. The discussion will focus on the description of: (1) a model for deriving downwelling global solar radiation, (2) regression techniques for inferring the total net radiation from planetary net radiation, and (3) the possibility for comparing the planetary and surface radiation budgets over the Tibetan Plateau.

Large‐scale heat exchange and ice production in the central Arctic

The arctic ice pack is a mixture of ice of many different thicknesses. Ice growth and heat exchange are strongly influenced by thickness, particularly when the ice is thin. For this reason measurements at a particular location do not necessarily represent conditions elsewhere within the region. Large‐scale heat exchange estimates must take into account contributions made by different thicknesses of ice. This requires information on the relative area covered by ice of any given thickness and on how each flux varies with thickness. Strain histories derived from the motions of several buoy and drifting station arrays were combined with climatological data on air temperatures and incoming radiation to estimate time dependent changes in the distribution of ice thickness in the Central Arctic. Thermodynamic ice models were used to determine the dependence of heat exchange and ice production on ice thickness. Large‐scale fluxes were then obtained by summing the area weighted contributions made by each ice thickness category. Differences between the large‐scale fluxes and those based on local measurements over perennial ice were due almost entirely to the effects of young ice less than a meter in thickness. Net annual ice production in areas of thin ice totaled about 1 m when averaged over the entire area of the strain array. In contrast to the very small annual values measured over multiyear ice, large‐scale turbulent heat losses were close to 200 MJ m−2 year−1, similar in magnitude to the net radiation. Absorption of shortwave radiation by summer leads resulted in annual net radiation totals for the region which were more than double those over the ice. Solar energy absorbed in the water played a major role in the mass balance of the ice cover. Intermediate thicknesses (0.2–0.8 m) of young ice, rather than open leads, exerted the greatest influence on ice production, heat input to the atmosphere, and salt input to the ocean. Monthly and annual heat flux totals obtained with different strain histories showed little correlation with the average divergence, suggesting that the variability of the strain field may be more important than the long‐term average of the strain components.

The Radiation Budget At Mizuho Station, Antarctica, 1979

Radiation budget measurements were made at Mizuho station (70°42'S, 44"20'E, 2 230 m a. s.1.), East Antarctica, in 1979, within the framework of the Japanese POLEX-South programme. Global, and reflected short-wave and downward and upward long-wave radiat i on fluxes were measured at the snow surface and at the top of a 30 m tower. Direct solar radiation was also measured at the snow surface. Seasonal variations of net radiation and net short-wave and net long-wave radiation are presented. Daily variation of net radiation is also presented with the daily value of meteorological elements. The monthly amounts of net radiation in winter months had very large negative values of about -80 MJ m−2 month−1. (-2 kly month−1). Daily totals of net radiation for clear skies were negative even i n summer, and were always smaller than those for cloudy skies. Monthly amounts of net radiation in summer months (about -1 MJ m−2 month−1 in December) were the smallest among the several Antarctic stations compared, and whether the balance was negative or positive depended on the ratio of clear and cloudy days. Comparison of seasonal variations of radiation components was made and the dominant cause of the radiation balance was discussed.

The Radiation Budget At Mizuho Station, Antarctica, 1979

Radiation budget measurements were made at Mizuho station (70°42'S, 44"20'E, 2 230 m a. s.1.), East Antarctica, in 1979, within the framework of the Japanese POLEX-South programme. Global, and reflected short-wave and downward and upward long-wave radiat i on fluxes were measured at the snow surface and at the top of a 30 m tower. Direct solar radiation was also measured at the snow surface.Seasonal variations of net radiation and net short-wave and net long-wave radiation are presented. Daily variation of net radiation is also presented with the daily value of meteorological elements. The monthly amounts of net radiation in winter months had very large negative values of about -80 MJ m−2 month−1. (-2 kly month−1). Daily totals of net radiation for clear skies were negative even i n summer, and were always smaller than those for cloudy skies. Monthly amounts of net radiation in summer months (about -1 MJ m−2 month−1 in December) were the smallest among the several Antarctic stations compared, and whether the balance was negative or positive depended on the ratio of clear and cloudy days. Comparison of seasonal variations of radiation components was made and the dominant cause of the radiation balance was discussed.

A model for the net total radiation flux at the surfaces of a building

A model is presented for the net total radiation flux at the surfaces of a particular building (in the shape of a U) which can be adjusted to other building shapes. The first step in deriving this model consists in the calculation of the various shape factors under which each surface sees the adjacent surfaces or the sky. Then the net solar and infra-red radiations as a function of the spatial organisation of the surfaces of the building, their physical characteristics and the radiative conditions on a free and horizontal reference surface are determined. Comparisons between experimental and theoretical results show that the assumptions introduced in the model lead to a satisfactory determination of the field of the surface temperatures and net total radiation at the surfaces of a building. The experimental study provides information about the amount of reflected solar and infra-red radiations at the proximity of vertical walls facing the sun.

Studies on Dew

The present paper deals with the characters of dew under winter-dry climate in southwest region of Taiwan (represented by Pingtung area). The dew amount was measured by means of weighing method with acrylic plate, and the time of dew formation start and dissipation were recorded by an improved Taylor type dew duration recorder. Records were analyzed for quantity and duration of dew and the dew amount were compared with precipitation and class A-pan evaporation. From November 1977 to May 1978 and October 1978 to May 1979, the observed records of dew were summarized as follows:(1) From November to May, the total number of dewy days were 149 in 1977 and 155 in 1978, while in the same periods the total dew amount were 25.9mm in 1977 and 26.2mm in 1978. The monthly average frequency of dewy day was 71%.(2) The maximum dew amount records were 4.2mg cm-2 hr-1, 43mg cm-2 day-1 and 6.57mm cm-2 month-1. The maximum value of duration was 13 hours and the average of that was 8.2 hours.(3) The daily dew amount can be calculated from the following equation with meteorological data, Y=9.3304X1+0.2358X2-0.1348X3+0.4167X4-20.3038, where, Y is the dew amount (mg cm-2 day-1), X1 the nocturnal cooling rate of air temperature in screen (°Chr-1), X2 the nocturnal relative humidity in screen (%), X3 the nocturnal wind speed at 1.5m height (cm s-1) and X4 the total nocturnal net radiation (ly).The proportion of calculated dew amount from regression equation was 79% to observed dew amount.(4) During the rainless month in winter season the dew amount was more than precipitation. The monthly average of dew amount was amount to 7% of precipitation and 4% of pan evaporation in normal year. The daily proportion of dew amount to pan evaporation which more than 10% was about 17% in total dewy days during the winter season.

Studies on Dew

The present paper deals with the characters of dew under winter-dry climate in southwest region of Taiwan (represented by Pingtung area). The dew amount was measured by means of weighing method with acrylic plate, and the time of dew formation start and dissipation were recorded by an improved Taylor type dew duration recorder. Records were analyzed for quantity and duration of dew and the dew amount were compared with precipitation and class A-pan evaporation. From November 1977 to May 1978 and October 1978 to May 1979, the observed records of dew were summarized as follows:(1) From November to May, the total number of dewy days were 149 in 1977 and 155 in 1978, while in the same periods the total dew amount were 25.9mm in 1977 and 26.2mm in 1978. The monthly average frequency of dewy day was 71%.(2) The maximum dew amount records were 4.2mg cm-2 hr-1, 43mg cm-2 day-1 and 6.57mm cm-2 month-1. The maximum value of duration was 13 hours and the average of that was 8.2 hours.(3) The daily dew amount can be calculated from the following equation with meteorological data, Y=9.3304X1+0.2358X2-0.1348X3+0.4167X4-20.3038, where, Y is the dew amount (mg cm-2 day-1), X1 the nocturnal cooling rate of air temperature in screen (°Chr-1), X2 the nocturnal relative humidity in screen (%), X3 the nocturnal wind speed at 1.5m height (cm s-1) and X4 the total nocturnal net radiation (ly).The proportion of calculated dew amount from regression equation was 79% to observed dew amount.(4) During the rainless month in winter season the dew amount was more than precipitation. The monthly average of dew amount was amount to 7% of precipitation and 4% of pan evaporation in normal year. The daily proportion of dew amount to pan evaporation which more than 10% was about 17% in total dewy days during the winter season.

Studies on the Microclimate of the Mulched Row Surface

The purpose of this paper was to investigate the effect of mulching by black polyethylene film (0.04mm thick) with planting holes (5.5cm diameter) and by soybean canopy on the microclimate near the row surface.Four experimental plots were designed as follow: No. 1 plot was not planted and not mulched, No. 2 plot was planted and not mulched, No. 3 plot was not planted and mulched, and No. 4 plot was planted and mulched. Medium maturing soybean, named ‘Ohsodefuri’, was used in this experiment. The observation was performed from April to August in 1979.1) Sum of the latent and sensible heat fluxes on the row surface of the mulched plot (No. 3) at night was remarkably increased by about 3.7 times that of unmulched plot (No. 1).When the plant cover was still small (June 4), it did not much affect the soil heat flux regardless of mulched or not. But, on July 26 (LAI, No. 2: 2.56, No. 4: 3.92) the vegetation lessened the ratio of soil heat flux to the daily amount of total net radiation, and these values were 3-4% both in mulching and unmulching.2) The plant canopy and film mulching controlled the rising of maximum temperature and the falling of minimum temperature, namely they lessened the diurnal range of soil temperature. Their effects could be called the buffer action.3) Mulching effect on soil temperature can be also showed by the ratio of diurnal range of temperature (daily range in treated plot/that in the not-treated one). The effect of film mulching (daily range of No. 3/that of No. 1) was reduced with the increase of daily insolation amount. When the amount came to 486cal cm-2day-1 the mulching effect disappeared.4) When transmissivities of solar radiation (above 40%) or the thickness of growth were same, the ratio of diurnal range of soil temperature in mulched plot (No. 4/No. 3) was greater than that of unmulched plot (No. 2/No. 1). This shows the difference in effects of soybean canopy between the case of mulching and not mulching. The ratio of No. 4/No. 1, which indicates the total effect of plant canopy and film mulching, was less than that of only plant plots (No. 4/No. 3) in early season.

Water use, energy balance and growth of gero millet at samaru, northern Nigeria

Energy and water budget of photo-insensitive millet crop grown in a dry sub-humid climate of northern Nigeria were assessed and related to crop performance. The pattern of crop water requirement during crop growth was well matched to the pattern of crop water availability. The period of maximum water requirement by the crop occurred when the leaf area index was greater than 1.8 and coincided with the period when the amount and frequency of rainfall was greatest. The total water used by the crop during 85 days from sowing to harvest was 330 mm, equivalent to water-use efficiency of 148 and 863 g water per gramme dry matter for total dry weight and grain dry weight, respectively. The crop yielded 22,519 kg ha −1 of total dry matter and 3,828 kg ha −1 of grain. The seasonal efficiency of energy conversion was 2.47% of the total incident radiation and 3.97% of the total net radiation. Evapotranspiration accounted for 88% of the net radiation, soil heat flux 5.5% and air heat flux 3%.

Shade‐cloth Microclimate of Soybeans1

AbstractA shade cloth tent was erected over a crop of soybeans [Glycine max (L.) Merr.], in a micrometeorological CO2 enrichment experiment, to restrict eddy diffusivity and vertical turbulent transport. This barrier was tried because earlier studies had shown that CO2 released in crops under natural conditions was rapidly dispersed by turbulence. The objectives were to evaluate plant response to the modified microclimate and the effectiveness of the shade cloth tent in reducing losses of applied CO2. Profiles of air temperature, CO2 concentration, water vapor concentration, and wind were measured both above and below the shade cloth and in an adjacent open field. Total solar, visible, and net radiation were also measured.Less light reached the shaded crop, but the plants grew larger and gave about the same dry‐matter yield. However the shaded crop lodged severely. Soil water was extracted at a slower rate by the shaded crop for two reasons: a) because less radiation reached the crop to supply energy for evapotranspiration and b) because a “humidity blanket” developed under the cloth barrier giving a smaller leaf‐to‐air vapor pressure gradient. The “humidity blanket” resulted from lower turbulent transport under the shade cloth. The shade cloth wind screen decreased water stress and water use, increased the amount and improved the distribution of diffuse irradiance, and increased the diffuse to direct‐beam irradiance ratio. Therefore shade culture might have potential beyond present‐day tobacco (Nicotiana tubacum L.) culture, for high value crops with low light saturation of photosynthesis, especially in arid climates with high solar radiation.Eddy diffusivity was reduced to about 16% at the height of the shade cloth, but CO2 concentration increases at the crop's top during releases were only about twice as large with the shade cloth in place as they were with the shade cloth removed. Therefore the shade cloth was moderately effective in trapping released CO2 but much still escaped.

An empirical method for estimating sunshine from total cloud amount

A new empirical method has been developed for computing sunshine S from total cloud amount. The equation used is of the form S = 1 − f 1 + f 2, where f 1 and f 2 are, respectively, functions of total cloud amount and latitude correction. The results obtained with this equation are compared with observed values and are found to be in good agreement. Tables 1 and 2 present these results. Assuming extreme conditions, the maximum possible deviations of total solar radiation, net radiation and evaporation (or potential evapotranspiration), using the formulae of Reddy[1–4] are discussed for the case where calculated values of S deviate 0·10 from observed values of S. The formula can be usefully employed with considerable accuracy in water and energy budget studies.

Radiation Climate of Barrow Alaska, 1962–66

Observations of the radiation climate near Point Barrow, Alaska, were conducted during a five-year period between 1962 and 1966. Data on incoming shortwave radiation, albedo, incoming longwave radiation, and net total radiation are summarized in the form of monthly and annual averages. Due to the prevalence of summer clouds, incident shortwave radiation (Q) reaches a peak in early June with maximum flux values in excess of 50 mW cm−3. Increasing cloud cover throughout the snow-free period results in a distribution for Q which is asymmetric about the summer solstice. Atmospheric transmissivity averages vary between 34% in late summer and 69% in late winter, the annual average being 51%. The albedo regime exhibits four distinctly different parts: 1) a winter stationary period, 2) a spring transitional period, 3) a summer stationary period, and 4) an autumn transitional period. Incoming longwave radiation (E) averages 24 mW cm−2 for the year with a seasonal variation of around 7 mW cm−2 year−1. On an annual basis, the surface receives more than twice as much longwave as shortwave radiation (744 vs 320 kJ cm−1). The data indicate that E can be calculated from the empirical relationship.where T is the air temperature at screen height and G is the cloudiness in tenths. Using this formula, the standard deviation of the percent difference between the observed and predicted values of E is 9%. Net total radiation (B) over the tundra averages 45 kJ cm−2 year−1; the annual total is critically dependent upon the date of snow melt. Bemuse of the lower summer albedos, the numerous lakes in the region have annual B values which are 25% larger than those over the tundra, resulting in an integrated average for the Barrow area of about 50 kJ cm−2 year−1. On the basis of this study it appears that with routine data from the Barrow Weather Station, together with supplemental snow cover data, the components of the radiation balance along the coastal portions. of the Alaskan North Slope can be estimated with an accuracy that may be sufficient for many biological and engineering applications.

A Three-Year Study of Net Radiation at St. Paul, Minnesota

This study is based upon net radiation measurements made with a Suomi-type ventilated net radiometer. The average annual net radiation was 36,247 ly for the study period 1 April 1964–31 March 1967. April–October showed positive net radiation totals, November–February negative net radiation totals, and March had positive net radiation totals in two of the three years studied. Only fourteen days with all negative net radiation and two days with all positive net radiation occurred in the three-year period. Average daily time of positive net radiation ranged from 244 min in January to 749 min in June. Although positive net radiation exceeded negative net radiation an average of 36,247 ly per year, negative or null net radiation was recorded 63% of the time. The ratio of net radiation to incoming solar radiation varied widely during the year. However, from May–August the ratio ranged only from 0.45–0.54 for any one month during the three years and averaged 0.50. Monthly net radiation values calculated by the method described by Sellers were within 10% or less of the measured values for all but two months. Budyko's calculated annual value of ∼35,000 ly also agreed favorably with the average measured value.