scholarly journals Experimental Assessment of the Effects of Low-Emissivity Paints as Interior Radiation Control Coatings

2020 ◽  
Vol 10 (3) ◽  
pp. 842 ◽  
Author(s):  
Stefano Fantucci ◽  
Valentina Serra
Keyword(s):  
Short Wave ◽  
Building Envelope ◽  
Wave Radiation ◽  
Radiative Heat Exchange ◽  
Aesthetic Value ◽  
Partition Wall ◽  
Radiation Control ◽  
Thermal Emissivity ◽  
Long Wave ◽  
Building Components

Radiation Control Coatings (RCC) are commonly recognised as paints, in which the long-wave radiation emissivity can be dramatically reduced from 0.9 to below 0.25 due to the dispersion of aluminium flakes inside the base paint. The low emissivity (Low-E) feature makes these materials particularly suitable for reducing the radiative heat exchange in building components and worthy of being used in roof attics, pipes, heat storage tank, etc. However, in the last few years, the application to the indoor surfaces of the building envelope has become quite popular, because the reflective properties can be exploited to increase the thermal comfort and reduce the winter heat losses. Except for aluminium based paint, that, for their strong metallized effect, suffer from some aesthetical limitation, the claimed performance of most of the other commercially available reflective paints are not universally recognized and in most of the cases their properties are misled, referring to visible and short wave infrared reflectivity. In this paper, a new methodology for assessing the long-wave thermal emissivity by using a heat flow meter apparatus is proposed. Moreover, the thermal emissivity of different paint mixtures with reduced metallised effect is assessed. The results allow for affirming that paints with acceptable aesthetic value (limited metallized effect) can reach an emissivity of ~0.60 instead of a typical emissivity of paint between 0.85–0.90. Furthermore, the partition wall of a double climatic chamber apparatus was painted with different low-E paints to evaluate whether an increase of the indoor operative temperature would have been observed. A slight, but not negligible, increase was shown of up to 0.3 °C and 0.6 °C for paint with an emissivity of ~0.6 and ~0.4, respectively.

scholarly journals Evaluating the Effects of Façade Greening on Human Bioclimate in a Complex Urban Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Britta Jänicke ◽  
Fred Meier ◽  
Marie-Therese Hoelscher ◽  
Dieter Scherer
Keyword(s):  
Heat Stress ◽  
Short Wave ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Long Wave ◽  
Building Facades ◽  
Urban Heat ◽  
The Mean ◽  
Human Bioclimate ◽  
Radiant Temperature

The evaluation of the effectiveness of countermeasures for a reduction of urban heat stress, such as façade greening, is challenging due to lacking transferability of results from one location to another. Furthermore, complex variables such as the mean radiant temperature(Tmrt)are necessary to assess outdoor human bioclimate. We observedTmrtin front of a building façade in Berlin, Germany, which is half-greened while the other part is bare.Tmrtwas reduced (mean 2 K) in front of the greened compared to the bare façade. To overcome observational shortcomings, we applied the microscale models ENVI-met, RayMan, and SOLWEIG. We evaluated these models based on observations. Our results show thatTmrt(MD = −1.93 K) and downward short-wave radiation (MD = 14.39 W/m2) were sufficiently simulated in contrast to upward short-wave and long-wave radiation. Finally, we compare the simulated reduction ofTmrtwith the observed one in front of the façade greening, showing that the models were not able to simulate the effects of façade greening with the applied settings. Our results reveal that façade greening contributes only slightly to a reduction of heat stress in front of building façades.

scholarly journals The Influence of Cloudiness on The Net Radiation Balance of A Snow Surface with High Albedo

1974 ◽  
Vol 13 (67) ◽  
pp. 73-84 ◽  
Author(s):  
W. Ambach
Keyword(s):  
Greenland Ice Sheet ◽  
Short Wave ◽  
Mean Value ◽  
Wave Radiation ◽  
Radiation Balance ◽  
Net Radiation ◽  
Long Wave ◽  
Energy Excess ◽  
Overcast Sky ◽  
Long Wave Radiation

The short-wave and long-wave radiant fluxes measured in the accumulation area of the Greenland ice sheet during a mid-summer period are discussed with respect to their dependence on cloudiness. At a cloudiness of 10/10, a mean value of 270 J/cm2 d is obtained for the daily totals of net radiation balance, whereas a mean value of only 75 J/cm2 d is observed at 0/10. The energy excess of the net radiation balance with overcast sky is due to the significant influence of the incoming long-wave radiation and the high albedo of the surface (average of 84%). High values of net radiation balance are therefore correlated with high values of long-wave radiation balance and low values of short-wave radiation balance.

Cloud effects on surface radiation balance at Helheim and Jakobshavn Glaciers (Greenland) using ground-based observations 

2021 ◽  
Author(s):  
Georges Djoumna ◽  
Sebastian H. Mernild ◽  
David Holland
Keyword(s):  
Short Wave ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Wave Radiation ◽  
Radiation Balance ◽  
Short Wave Radiation ◽  
Radiative Fluxes ◽  
Long Wave ◽  
Transmittance Factor ◽  
Cloud Metrics

<p>The surface radiation budget is an essential component of the total energy exchange between the atmosphere and the Earth’s surface. Measurements of radiative fluxes near/on ice surfaces are sparse in the polar regions, including on the Greenland Ice Sheet (GrIS), and the effects of cloud on radiative fluxes are still poorly studied. In this work, we assess the impacts of cloud on radiative fluxes using two metrics: the longwave-equivalent cloudiness, derived from long-wave radiation measurements, and the cloud transmittance factor, obtained from short-wave radiation. The metrics are applied to radiation data from two automatic weather stations located over the bare ground near the ice front of Helheim (HG) and Jakobshavn Isbræ (JI) on the GrIS. Comparisons of meteorological parameters, surface radiation fluxes, and cloud metrics show significant differences between the two sites. The cloud transmittance factor is higher at HG than at JI, and the incoming short-wave radiation in the summer at HG is 50.0 W m−2 larger than at JI. Cloud metrics derived at the two sites reveal   a high dependency on the wind direction. The total cloud radiative effect (CREnet) generally increases during melt season at the two stations due to long-wave CRE enhancement by cloud fraction.  CREnet decreases from May to June and increases afterward, due to the strengthened short-wave CRE. The annually averaged CREnet were 3.0 ± 7.4 W m-2 and 1.9 ± 15.1 W m−2 at JI and HG.  CREnet estimated from AWS indicates that clouds cool the JI and HG during melt season at different rates.</p>

scholarly journals Prediction of Radiation Frost Using Support Vector Machines Based on Micrometeorological Data

2019 ◽  
Vol 10 (1) ◽  
pp. 283
Author(s):  
Yongzong Lu ◽  
Yongguang Hu ◽  
Pingping Li ◽  
Kyaw Tha Paw U ◽  
Richard L. Snyder
Keyword(s):  
Yangtze River ◽  
Prediction Accuracy ◽  
Short Wave ◽  
Yangtze River Delta ◽  
Wave Radiation ◽  
Support Vector ◽  
Short Wave Radiation ◽  
Long Wave ◽  
Vector Machines ◽  
Long Wave Radiation

Radiation frost happens frequently in the Yangtze River Delta region, which causes high economic loss in agriculture industry. It occurs because of heat losses from the atmosphere, plant and soil in the form of radiant energy, which is strongly associated with the micrometeorological characteristics. Multidimensional and nonlinear micrometeorological data enhances the difficulty in predicting the radiation frost. Support vector machines (SVMs), a type of algorithms, can be supervised learning which widely be employed for classification or regression problems in research of precision agriculture. This paper is the first attempt of using SVMs to build prediction models for radiation frost. Thirty-two kinds of micrometeorological parameters, such as daily mean temperature at six heights (Tmean0.5, Tmean1.5, Tmean2.0, Tmean3.0, Tmean4.5 and Tmean6.0), daily maximum and minimum temperatures at six heights (Tmax0.5, Tmax1.5, Tmax2.0, Tmax3.0, Tmax4.5 and Tmax6.0, and Tmin0.5, Tmin1.5, Tmin2.0, Tmin3.0, Tmin4.5 and Tmin6.0), daily mean relative humidity at six heights (RH0.5, RH1.5, RH2.0, RH3.0, RH4.5 and RH6.0), net radiation (Rn), downward short-wave radiation (Rsd), downward long-wave radiation (Rld), upward long-wave radiation (Rlu), upward short-wave radiation (Rsu), soil temperature (Tsoil) and soil heat flux (G) and daily average wind speed (u) were collected from November 2016 to July 2018. Six combinations inputs were used as the basis dataset for testing and training. Three types of kernel functions, such as linear kernel, radial basis function kernel and polynomial kernel function were used to develop the SVMs models. Five-fold cross validation was conducted for model fitting on training dataset to alleviate over-fitting and make prediction results more reliable. The results showed that an SVM with the radial basis function kernel (SVM-BRF) model with all the 32 micrometeorological data obtained high prediction accuracy in training and testing sets. When the single type of data (temperature, humidity and radiation data) was used for the SVM without any functions, prediction accuracy was better than that with functions. The SVM-BRF model had the best prediction accuracy when using the multidimensional and nonlinear micrometeorological data. Considering the complexity level of the model and the accuracy of prediction, micrometeorological data at the canopy height with the SVM-BRF model has been recommended for radiation frost prediction in Yangtze River Delta and probably could be applied in elsewhere with the similar terrains and micro-climates.

scholarly journals Some Observations on the Climate of Lewis Glacier, Mount Kenya, During the Rainy Season

1966 ◽  
Vol 6 (44) ◽  
pp. 267-287 ◽  
Author(s):  
C. M. Platt
Keyword(s):  
Heat Balance ◽  
Rainy Season ◽  
Short Wave ◽  
Turbulent Exchange ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Long Wave ◽  
Meteorological Observations ◽  
The Heat Balance ◽  
Long Wave Radiation

AbstractMeteorological observations were made on Lewis Glacier, Mount Kenya, during the “long rains” in April 1960. General meteorological observations indicated rather similar conditions to those found in other months. Ablation occurred on each day but amounts were generally small. Rather more accumulation occurred than is expected during the dry season, but again amounts were small. The net accumulation over a to day period was only 0.38 cm. water-equivalent, although about 30 cm. new snow (about 10 cm. water-equivalent) was lying when the expedition arrived. Detailed observations of short-wave radiation, temperature, wind and humidity with estimates of long-wave radiation were used to calculate the heat balance at the surface of the upper ablation region. Agreement between calculated and measured ablation was reasonably good. Over the periods considered, radiation accounted for 89.5 per cent of ablation, turbulent exchange from the air for 8.0 per cent and evaporation for 2.5 per cent. Subsurface melting was taken into account and the formation of ice bands in terms of such melting is discussed.

scholarly journals Radiation measurement at Lewis Glacier, Mount Kenya, Kenya

1980 ◽  
Vol 25 (93) ◽  
pp. 439-444 ◽  
Author(s):  
Stefan Hastenrath ◽  
J. K. Patnaik
Keyword(s):  
Global Radiation ◽  
Short Wave ◽  
Steep Slope ◽  
Horizontal Component ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Glacier Surface ◽  
Rock Face ◽  
Long Wave ◽  
Long Wave Radiation

AbstractShort- and long-wave radiation on variously oriented vertical surfaces, direct solar radiation, global radiation, and long–wave radiation on a horizontal surface were measured on Lewis Glacier, Mount Kenya, at 4800 m. For the orientation of vertical surfaces, the following azimuths were selected: 45°, facing the steep slope of the upper glacier; 135°, facing a rock ridge and some glacier surface in the foreground; 225°, facing down–glacier towards the Teleki valley with open sky occupying much of the view; and 315°, directed towards the steep south-east face of the Nelion peak.The horizontal components of diffuse short-wave radiation reach a magnitude comparable to those of direct radiation. As a result of contrastingly different albedos of natural surfaces, the horizontal component of diffuse short–wave radiation is particularly large from the direction of the upper glacier, with values around 330–500 W m−2, and smallest from the direction of the rock face of Nelion peak, where values are around 150–330 W m−2. Long–wave radiation seems enhanced from the direction of the Nelion face, and reduced from the azimuth of the upper glacier, thus apparently reflecting differences in emissivity and temperature.

scholarly journals The Radiation Budget At Mizuho Station, Antarctica, 1979

1982 ◽  
Vol 3 ◽  
pp. 327-332
Author(s):  
Takashi Yamanouchi ◽  
Makoto Wada ◽  
Shinji Mae ◽  
Sadao Kawaguchi ◽  
Kou Kusunoki
Keyword(s):  
Seasonal Variations ◽  
Daily Variation ◽  
Short Wave ◽  
Radiation Budget ◽  
Wave Radiation ◽  
Radiation Balance ◽  
Snow Surface ◽  
Net Radiation ◽  
Long Wave ◽  
Meteorological Elements

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.

scholarly journals Meteorological Conditions and Cloud Effects on Surface Radiation Balance Near Helheim Glacier and Jakobshavn Isbræ (Greenland) Using Ground-Based Observations

2021 ◽  
Vol 8 ◽  
Author(s):  
G. Djoumna ◽  
S. H. Mernild ◽  
D. M. Holland
Keyword(s):  
Short Wave ◽  
Surface Radiation ◽  
Radiation Budget ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Radiative Fluxes ◽  
Radiation Data ◽  
Long Wave ◽  
Transmittance Factor ◽  
Cloud Metrics

The surface radiation budget is an essential component of the total energy exchange between the atmosphere and the Earth’s surface. Measurements of radiative fluxes near/on ice surfaces are sparse in the polar regions, including on the Greenland Ice Sheet (GrIS), and the effects of cloud on radiative fluxes are still poorly studied. In this work, we assess the impacts of cloud on radiative fluxes using two metrics: the longwave-equivalent cloudiness, derived from long-wave radiation measurements, and the cloud transmittance factor, obtained from short-wave radiation data. The metrics are applied to radiation data from two automatic weather stations located over the bare ground near the ice front of Helheim (HG, 66.3290°N, 38.1460°W) and Jakobshavn Isbræ(JI, 69.2220°N, 49.8150°W) on the GrIS. Comparisons of meteorological parameters, surface radiation fluxes, and cloud metrics show significant differences between the two sites. The cloud transmittance factor is higher at HG than at JI, and the incoming short-wave radiation in the summer at HG is about 50.0 W m−2 larger than at JI. Cloud metrics derived at the two sites reveal partly cloudy conditions were frequent (42 and 65% of the period at HG and JI) with a high dependency on the wind direction. The total cloud radiative effect (CREnet) generally increases during melt season at the two stations due to long-wave CRE enhancement by cloud fraction. CREnet decreases from May to June and increases afterward, due to the strengthened short-wave CRE. The annually averaged CREnet were 3.0 ± 7.4 W m−2 and 1.9±15.1 W m−2 at JI and HG. CREnet estimated from AWS indicates that clouds cool the JI and HG during melt season at different rates.

Micro-Meteorological Conditions for Snow Melt

1987 ◽  
Vol 33 (113) ◽  
pp. 24-26 ◽  
Author(s):  
M. Kuhn
Keyword(s):  
Boundary Layer ◽  
Transfer Coefficient ◽  
Air Temperature ◽  
Short Wave ◽  
Wave Radiation ◽  
Free Atmosphere ◽  
Alpine Glacier ◽  
Long Wave ◽  
Air Temperatures ◽  
Long Wave Radiation

AbstractThe energy budget of a snow or ice surface is determined by atmospheric variables like solar and atmospheric long-wave radiation, air temperature, and humidity; the transfer of energy from the free atmosphere to the surface depends on the stability of the atmospheric boundary layer, where vertical profiles of wind speed and temperature determine stability, and on surface conditions like surface temperature (and thus surface humidity), roughness, and albedo.This paper investigates the conditions exactly at the onset or the end of melting using air temperature, humidity, and as the radiation term the sum of global and reflected short-wave plus downward long-wave radiation. For the turbulent exchange in the boundary layer, examples are computed with a transfer coefficient of 18.5 W m−2K−1which corresponds to the average over the ablation period on an Alpine glacier. Ways to estimate the transfer coefficient for various degrees of stability are indicated in the Appendix.It appears from such calculations that snow may melt at air temperatures as low as –10°C and may stay frozen at +10°C.

scholarly journals Radiation and Cloud Observations on a High Arctic Plateau Ice Cap

1987 ◽  
Vol 33 (114) ◽  
pp. 162-168 ◽  
Author(s):  
M.C. Serreze ◽  
R.S. Bradley
Keyword(s):  
Surface Albedo ◽  
High Surface ◽  
High Arctic ◽  
Short Wave ◽  
Wave Radiation ◽  
Net Radiation ◽  
Short Wave Radiation ◽  
Ice Cap ◽  
Long Wave ◽  
Long Wave Radiation

AbstractHourly measurements of incoming short-wave and long-wave radiation, surface albedo, and net radiation were made on and around a plateau ice cap on north-eastern Ellesmere Island during the summers of 1982 and 1983. These data were stratified by cloud type and amount. All cloud types increased incoming long-wave radiation, especially low dense clouds, fog, and clouds associated with snowfall. Relative transmission of incoming short-wave radiation, expressed as a percentage of clear-sky radiation receipts, was high for all cloud types compared to clouds at lower latitudes. With high surface albedo (≥0.75), net radiation was strongly and positively correlated with net long-wave radiation but showed little relationship to net short-wave radiation. By contrast, with low surface albedo (≤0.20) net radiation was negatively correlated with net long-wave radiation but positively correlated with net short-wave radiation. Under high-albedo conditions, an increase in cloudiness led to higher values of net radiation but under low-albedo conditions net radiation decreased as cloud cover increased. Survival of a snow cover would seem to be favoured if the seasonal decline in albedo is accompanied by a corresponding increase in cloudiness.

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