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 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−2 K−1 which 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 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.

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.

Transmission of the Total and the Infrared Component of Solar Radiation Through a Smoky Atmosphere

1943 ◽  
Vol 24 (5) ◽  
pp. 201-204 ◽  
Author(s):  
Irving F. Hand
Keyword(s):  
Solar Radiation ◽  
Forest Fires ◽  
Solar Spectrum ◽  
Normal Incidence ◽  
Wave Radiation ◽  
Free Atmosphere ◽  
Simultaneous Measurements ◽  
Long Wave ◽  
Minute Period ◽  
Long Wave Radiation

SUMMARY Immediately before and during the passage of a smoke cloud from forest fires, simultaneous measurements were made of total normal incidence solar radiation and that portion of the solar spectrum longer than 0.7μ. Calculations made of the relative amount of radiation that should be received for both the total and limited components checked closely with the ratios between measurements with a smoke-free atmosphere but showed variance with ratios obtained in the presence of smoke. The range between the maximum and minimum values of total radiation during a ten-minute period in the presence of smoke was 2.3 times as great as the range between the maximum and minimum values of infrared radiation; from which we conclude, as theory implies, that long-wave radiation passes much more freely through an atmosphere containing particles slightly less than one micron in diameter than does the shorter, or visible and ultraviolet radiation.

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.

The Meteorological Impact to the Air Temperature on a Sub-Tropical City

2014 ◽  
Vol 905 ◽  
pp. 374-378
Author(s):  
Chih Hong Huang ◽  
John Cua Aganda
Keyword(s):  
Air Temperature ◽  
Minimum Temperature ◽  
Wave Radiation ◽  
Urban Air ◽  
Temperature Pattern ◽  
Long Wave ◽  
The Difference ◽  
Meteorological Impact ◽  
The City ◽  
Long Wave Radiation

This study will center on the meteorological impact of clouds and its influence to the urban air temperature. Quantitative assessment over the behavior and temperature pattern was done using a five-year data of meteorological parameters obtain from the local weather and climate bureau. Urban heat island (UHI) is defined as the increased air temperature of the city over its surrounding sub-urban and rural areas and in this case of a five-year summer period of Taipei, Taiwan were heat temperatures are higher and can go beyond 39°C, acting dominant meteorological cloud cover factor is observe for its effect in temperature pattern. Analysis of local heat characteristics suggests the possibility of the believed theory Urban-scaled greenhouse effect that maybe affecting the patterns of the urban air temperature. An urban-scaled greenhouse effect is a theory that implies; when dense cloud covers the city, most of the supposed released long wave radiation or heat energy is trapped and reflected back by the dense clouds, creating a body of conserved heat that is prolonged in the area. The duration of conserved heat (DCH) is measured by the difference of the diurnal maximum and minimum temperature. To assess the value of the theory the daily cloud amount (CA) and its relationship with the DCH was tested with regression analysis. Calm days with the complete cycle of maximum and minimum temperature accordingly were selected and tested. The five-year average (2008 – 2012) resulted in a regression value of R2 = 0.072. Although the years 2011 & 2012 showed a higher regression value of R2 = 0.265 and R2 = 0.104 respectively, certainly enough the data of years 2011 and 2012 revealed a higher ratio of days with less combination of high wind speed and rainfall which created less fluctuations. Trend pattern for the five summers showed similarities. Some days showed fluctuation but no negative trend of correlation was detected. The heat intensity (HI) is another type of temperature pattern that was observed against CA and DCH, it is characterized by the difference of maximum and minimum diurnal temperature. Suggestive with our analysis, all five-year summertime data of HI showed negative correlation with the CA and DCH, attesting a faster release of long wave radiation when clouds are less.

The radiation balance of an apple tree

1972 ◽  
Vol 50 (8) ◽  
pp. 1731-1740 ◽  
Author(s):  
J. T. A. Proctor ◽  
W. J. Kyle ◽  
J. A. Davies
Keyword(s):  
Reflection Coefficient ◽  
Apple Tree ◽  
Short Wave ◽  
Wave Radiation ◽  
Radiation Balance ◽  
Net Radiation ◽  
Short Wave Radiation ◽  
Radiative Processes ◽  
Long Wave ◽  
Long Wave Radiation

Measurements of radiation balance components over an apple tree on 7 days during the growing season showed that 17% of the short-wave radiation was reflected, 17% was lost as long-wave radiation and net radiation amounted to 66%. The reflection coefficient exhibited a characteristic diurnal variation, demonstrating its dependence on solar zenith angle, and varied little over the season. Within the orchard, surfaces ranked in order of increasing reflection coefficient as tree, dry orchard grass, and intertree space.Correlation coefficients relating hourly values of net radiation to incoming short-wave radiation and net short-wave radiation, and net long-wave radiation to net short-wave radiation were highly significant. The heating coefficient was positive and decreased slightly at the end of the season. The long-wave exchange coefficient was negative and exhibited no seasonal trend. This coefficient was closely correlated with screen temperature and may provide a basis for interpretation of surface radiative processes.

scholarly journals Seasonal and Interannual Variation in Energy Balance in the Semiarid Grassland Area of China

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Qun’ou Jiang ◽  
Enjun Ma ◽  
Jinyan Zhan ◽  
Nana Shi
Keyword(s):  
Climate Change ◽  
Energy Balance ◽  
Land Cover ◽  
Interannual Variation ◽  
Short Wave ◽  
Wave Radiation ◽  
Short Wave Radiation ◽  
Semiarid Grassland ◽  
Long Wave ◽  
Long Wave Radiation

Near surface energy budget changes have been proved to be induced by the land cover conversion through changing the surface physical properties, which can further impact the regional climate change. This study applies the DLS model to simulate the land cover under the business as usual (BAU) scenario and then analyses the seasonal and interannual variation of energy balance in the semiarid grassland area of China based on the simulated land cover with the Weather Research and Forecasting (WRF) model. The results indicate that the grassland will show a growing trend under the BAU scenario. Downward long wave radiation and downward short wave radiation will all have small-scale increase with time going by, while the surface net radiation will decrease from 2030 to 2050. However, there is obvious seasonal variation. Summer has the highest downward long wave radiation and downward short wave radiation, followed by spring and autumn. The lowest are in winter. As for the net surface radiation, there is obvious decrease in southeast of study area due to returning cropland to grassland. Those research conclusions can offer valuable information for the land use planning and relieving the effects of land cover change on climate change at the semiarid grassland area.

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