scholarly journals Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface

2017 ◽  
Vol 9 (8) ◽  
pp. 3069-3081 ◽  
Author(s):  
Zhiyuan Zheng ◽  
Zhigang Wei ◽  
Zhiping Wen ◽  
Wenjie Dong ◽  
Zhenchao Li ◽  
...  
Keyword(s):  
Land Surface ◽  
Surface Albedo ◽  
Elevation Angle ◽  
Soil Surface ◽  
Bare Soil ◽  
Solar Elevation ◽  
Solar Elevation Angle

scholarly journals Multi-temporal analysis of radiometric changes in satellite images of forest edges to infer selective-logging areas in the Amazon forest

2015 ◽  
Vol 45 (1) ◽  
pp. 35-44 ◽  
Author(s):  
Paulo Maurício Lima de Alencastro GRAÇA ◽  
Francisco Dario MALDONADO ◽  
João Roberto dos SANTOS ◽  
Edwin Willem Hermanus KEIZER
Keyword(s):  
Satellite Images ◽  
Near Infrared ◽  
Elevation Angle ◽  
Temporal Analysis ◽  
Selective Logging ◽  
Amazon Forest ◽  
Forest Edges ◽  
Solar Elevation ◽  
Multi Temporal ◽  
Solar Elevation Angle

Radiometric changes observed in multi-temporal optical satellite images have an important role in efforts to characterize selective-logging areas. The aim of this study was to analyze the multi-temporal behavior of spectral-mixture responses in satellite images in simulated selective-logging areas in the Amazon forest, considering red/near-infrared spectral relationships. Forest edges were used to infer the selective-logging infrastructure using differently oriented edges in the transition between forest and deforested areas in satellite images. TM/Landsat-5 images acquired at three dates with different solar-illumination geometries were used in this analysis. The method assumed that the radiometric responses between forest with selective-logging effects and forest edges in contact with recent clear-cuts are related. The spatial frequency attributes of red/near infrared bands for edge areas were analyzed. Analysis of dispersion diagrams showed two groups of pixels that represent selective-logging areas. The attributes for size and radiometric distance representing these two groups were related to solar-elevation angle. The results suggest that detection of timber exploitation areas is limited because of the complexity of the selective-logging radiometric response. Thus, the accuracy of detecting selective logging can be influenced by the solar-elevation angle at the time of image acquisition. We conclude that images with lower solar-elevation angles are less reliable for delineation of selecting logging.

Movement of Water Across Soils (Erosion)

1999 ◽  
Author(s):  
Robert F. Keefer
Keyword(s):  
Land Surface ◽  
Grand Canyon ◽  
Soil Surface ◽  
Bare Soil ◽  
Surface Flow ◽  
Running Water ◽  
Soil Particles ◽  
The Moment ◽  
New Location ◽  
Sheet Erosion

Erosion is the physical wearing away of the land surface by running water, wind, or ice. Soil or rock is initially detached by falling water, running water, wind, ice or freezing conditions, or gravity. Movement of the rock or soil may follow. Erosion is the combination of detachment and movement of soil or rock. Water erosion can be subdivided into either natural or man-made. Natural or geologic erosion does not require the presence of man. This process has been going on from the moment that land masses were uplifted. An example of geologic erosion is the Grand Canyon in Arizona. Man-made erosion is also called “accelerated erosion” as it is more rapid than natural erosion. Changes that man or animals have made to the soil by cultivation, construction, or any movement of earth often result in loss of soil by erosion. Accelerated erosion involves raindrop erosion, sheet erosion, surface flow, and landscapes. For raindrop erosion to occur, there must be detachment of soil particles followed by either transportation or compaction. Sheet erosion is the slow wearing away of the surface of soil. Surface flow occurs when sufficient water collects to run downhill, resulting in small soil cuts (rills) that often develop into large ruts (gullies). Landslides or slips occur when large chunks of soil move as a unit downhill, often resulting in drops of several feet or more. As rain falls, the drops strike the soil surface moving the soil particles with energy being expended in three kinds of ways: (a) detachment— soil particles are broken into smaller pieces, (b) transportation— small soil grains are moved to a new location as they splash into the air; movement can be downward, to sides, or up eventually acting as a smoothing agent, or (c) compaction—raindrops compact soil surface on bare soil forming a crust, resulting in running the soil particles together (puddling) so that air and water can no longer enter the soil. This causes loss of infiltration and results in runoff.

Extracting icebergs freeboard from the shadows in Landsat-8 panchromatic images

2020 ◽  
Author(s):  
Zhenfu Guan ◽  
Yan Liu
Keyword(s):  
Large Scale ◽  
Accuracy Assessment ◽  
Elevation Angle ◽  
Absolute Error ◽  
Landsat 8 ◽  
High Precision Measurement ◽  
Solar Elevation ◽  
The Mean ◽  
The Antarctic ◽  
Solar Elevation Angle

<p><strong>Abstract:</strong> The iceberg freeboard is an important geometric parameter for measuring the thickness of the iceberg and then estimating its volume. Based on the fact that the iceberg can cast elongated shadow on the surface of sea ice in winter, this paper proposes a method to measure the iceberg freeboard using shadow length and the predefined or estimated solar elevation angle. Three Landsat-8 panchromatic images are selected to test our method, with center solar elevation angle of respectively 5.43°, 7.49°and 11.01° on August 29, September 7, and 16 September in 2016. Shadow lengths of five isolated tabular icebergs are automatically extracted to calculate the freeboard height. For the accuracy assessment, we use the matching points at the different time as cross validation. The results show that the measurement error of shadow length is less than one pixel. When the sun elevation angle is lower than 11.01°, the Root Mean Square Error (RMSE) of the iceberg freeboard from the panchromatic 15 m image is less than 2.0 m, and the Mean Absolute Error (MAE) is less than 1.5 m. Such experiment shows that: under the angle of low solar elevation in winter, the landsat-8 panchromatic 15 m image can be used for high-precision measurement of the iceberg freeboard, and has the potential to measure the Antarctic iceberg freeboard in large scale.</p><p><strong>Key </strong><strong>words:</strong> Antarctic, icebergs, freeboard, shadow altimetry, Landsat-8</p><p> </p>

Solar elevation angle probability distribution

Solar Energy ◽  
1980 ◽  
Vol 24 (4) ◽  
pp. 417-420 ◽  
Author(s):  
D.C. Larson ◽  
C.R. Acquista
Keyword(s):  
Probability Distribution ◽  
Elevation Angle ◽  
Solar Elevation ◽  
Solar Elevation Angle

scholarly journals Latitude and Weather Influences on Sun Light Quality and the Relationship to Tree Growth

Forests ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 610 ◽  
Author(s):  
Camilo Chiang ◽  
Jorunn E. Olsen ◽  
David Basler ◽  
Daniel Bånkestad ◽  
Günter Hoch
Keyword(s):  
Light Quality ◽  
Elevation Angle ◽  
Spectral Composition ◽  
Weather Conditions ◽  
Seasonal Adjustment ◽  
Light Climate ◽  
Solar Elevation ◽  
Light Quantity ◽  
R:Fr Ratio ◽  
Solar Elevation Angle

Natural changes in photoperiod, light quantity, and quality play a key role in plant signaling, enabling daily and seasonal adjustment of growth and development. Growing concern about the global climate crisis together with scattered reports about the interactive effects of temperature and light parameters on plants necessitates more detailed information about these effects. Furthermore, the actual light emitting diode (LED) lighting technology allows mimicking of light climate scenarios more similar to natural conditions, but to fully exploit this in plant cultivation, easy-to-apply knowledge about the natural variation in light quantity and spectral distribution is required. Here, we aimed to provide detailed information about short and long-term variation in the natural light climate, by recording the light quantity and quality at an open site in Switzerland every minute for a whole year, and to analyze its relationship to a set of previous tree seedling growth experiments. Changes in the spectral composition as a function of solar elevation angle and weather conditions were analyzed. At a solar elevation angle lower than 20°, the weather conditions have a significant effect on the proportions of blue (B) and red (R) light, whereas the proportion of green (G) light is almost constant. At a low solar elevation, the red to far red (R:FR) ratio fluctuates between 0.8 in cloudy conditions and 1.3 on sunny days. As the duration of periods with low solar angles increases with increasing latitude, an analysis of previous experiments on tree seedlings shows that the effect of the R:FR ratio correlates with the responses of plants from different latitudes to light quality. We suggest an evolutionary adaptation where growth in seedlings of selected tree species from high latitudes is more dependent on detection of light quantity of specific light qualities than in such seedlings originating from lower latitudes.

scholarly journals Radiation balance diversity on NW Spitsbergen in 2010–2014

2017 ◽  
Vol 38 (1) ◽  
pp. 61-82 ◽  
Author(s):  
Marek Kejna ◽  
Marion Maturilli ◽  
Andrzej Araźny ◽  
Ireneusz Sobota
Keyword(s):  
Elevation Angle ◽  
Radiation Balance ◽  
The Sun ◽  
Net Income ◽  
Annual Variations ◽  
Solar Elevation ◽  
Diurnal Course ◽  
Polar Day ◽  
Solar Elevation Angle ◽  
North Western

AbstractThis article presents the results of observations of selected fluxes of the radiation balance in north-western Spitsbergen in the years from 2010 to 2014. Measurements were taken in Ny-Ålesund and in the area of Kaffiøyra, on different surface types occurring in the Polar zone: moraine, tundra, snow and ice. Substantial differences in the radiation balance among the various types of surface were observed. The observations carried out in the summer seasons of 2010–2014 in the area of Kaffiøyra demonstrated that the considerable reflection of solar radiation on the Waldemar Glacier (albedo 55%) resulted in a smaller solar energy net income. During the polar day, a diurnal course of the components of the radiation balance was apparently related to the solar elevation angle. When the sun was low over the horizon, the radiation balance became negative, especially on the glacier. Diurnal, annual and multi-annual variations in the radiation balance have a significant influence on the functioning of the environment in polar conditions.

scholarly journals Some practical notes on the land surface modeling in the Tibetan Plateau

2009 ◽  
Vol 6 (1) ◽  
pp. 1291-1320 ◽  
Author(s):  
K. Yang ◽  
Y.-Y. Chen ◽  
J. Qin
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Land Surface ◽  
Soil Surface ◽  
Bare Soil ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Central Plateau ◽  
Alpine Meadows ◽  
Common Land Model

Abstract. The Tibetan Plateau is a key region of land-atmosphere interactions, as it provides an elevated heat source to the middle-troposphere. The Plateau surfaces are typically characterized by alpine meadows and grasslands in the central and eastern part while by alpine deserts in the western part. This study evaluates performance of three state-of-the-art land surface models (LSMs) for the Plateau typical land surfaces. The LSMs of interest are SiB2 (the Simple Biosphere), CoLM (Common Land Model), and Noah. They are run with default parameters at typical alpine meadow sites in the central Plateau and typical alpine desert sites in the western Plateau. The recognized key processes and modeling issues are as follows. First, soil stratification is a typical phenomenon beneath the alpine meadows, with dense roots and soil organic matters within the topsoil, and it controls the profile of soil moisture in the central and eastern Plateau; all models significantly under-estimate the soil moisture within the topsoil. Second, a soil surface resistance controls the surface evaporation from the alpine deserts but it has not been reasonably modeled in LSMs; a new scheme is proposed to determine this resistance from soil water content. Third, an excess resistance controls sensible heat fluxes from dry bare-soil or sparsely vegetated surfaces, and all LSMs significantly under-predict the ground-air temperature difference in the daytime. A parameterization scheme for this resistance has been shown effective to remove this bias.

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