8 research outputs found
Multi-sensor remote sensing parameterization of heat fluxes over heterogeneous land surfaces
No full textThe parameterization of heat transfer by remote sensing, and based on SEBS scheme for turbulent heat fluxes retrieval, already proved to be very convenient for estimating evapotranspiration (ET) over homogeneous land surfaces. However, the use of such a method over heterogeneous landscapes (e.g. semi-arid regions or agricultural land) becomes more difficult, since the principle of similarity theory is compromised by the presence of different heat sources with various heights. This thesis aims at first to propose and evaluate some models based on vegetation geometry for retrieving the surface roughness length for momentum transfer (z0m), which is a key parameter in the characterization of heat transfer. Such an investigation can only be led at a small scale with very-high resolution remote sensing data, for a precise description of the land surface. Therefore, the second aspect of this work is to determine how to address the characterization of heat transfer for regional studies. Then, the reliability of SEBS for estimating turbulent heat fluxes at large spatial and temporal scales has been evaluated. To do so, the Multi-Scale SEBS approach (MSSEBS) has been implemented for a 2.4 million km2 area including the Tibetan Plateau and the headwaters of the major rivers of East and South Asia. The addition of gap-filled hourly FY-2 LST data to advanced daily averaged net radiation and land surface parameters, allows to compute time-series of land surface ET over the Tibetan Plateau during the period 2008-2010, and on a daily basis.Geoscience and Remote SensingCivil Engineering and Geoscience
Observing at-surface irradiance and albedo from space: The Tibet experiment
No full textMonitoring the solar radiation budget on a daily basis is a prerequisite to study land surface processes, especially in climatology and hydrology, and in derived applications like drought early warning. Current space-born radiometers can provide daily observations to derive surface radiative fluxes at a spatial resolution of one square kilometer at best, which is not enough to properly take into account surface heterogeneity in many regions of the globe. As part of a major scientific initiative to study the hydrology of the Tibetan Plateau -especially known for its rough topography- this thesis focuses on developing a method to adequately estimate at-surface daily solar radiation budget over this particular area. Following a first effort to produce a time series of the radiative budget from existing satellite data products, it appeared that it is necessary to consider terrain and clouds spatial variability at the sub-pixel level when working over heterogeneous areas such as the Tibetan Plateau. Thus, the impact of spatial and temporal variability of clouds on solar radiation was investigated through a case study conducted on the field whose results demonstrate that the surface irradiance estimation would benefit from using cloud distribution instead of cloud fraction to account for the cloud cover. Furthermore, a high temporal resolution cloud cover leads to a better temporal average of the radiative fluxes. Regarding the effects of the terrain, a new sub-pixel topographic correction method is proposed and applied. It demonstrates that the integration of the sub-pixel topographic effects using high resolution DEM improves the irradiance as well as the albedo retrieval. The temporal resolution of the latter is also to consider and the use of geostationary satellite allows to increase the retrieval frequency. Based on multi-source and multi-resolution remote sensing data, the developed method provides a usable solar radiation budget dataset. Combined with the outcomes of the in-depth researches on clouds and topography, it paves the way for a new operational methodology which adequately accounts for sub-pixel heterogeneity when producing large area time series of solar radiation budget at the surface.Geoscience and Remote SensingCivil Engineering and Geoscience
Improved Surface Reflectance from Remote Sensing Data with Sub-Pixel Topographic Information
No full textSeveral methods currently exist to efficiently correct topographic effects on the radiance measured by satellites. Most of those methods use topographic information and satellite data at the same spatial resolution. In this study, the 30 m spatial resolution data of the Digital Elevation Model (DEM) from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) are used to account for those topographic effects when retrieving land surface reflectance from satellite data at lower spatial resolution (e.g., 1 km). The methodology integrates the effects of sub-pixel topography on the estimation of the total irradiance received at the surface considering direct, diffuse and terrain irradiance. The corrected total irradiance is then used to compute the topographically corrected surface reflectance. The proposed method has been developed to be applied on various kilometric pixel size satellite data. In this study, it was tested and validated with synthetic Landsat data aggregated at 1 km. The results obtained after a sub-pixel topographic correction are compared with the ones obtained after a pixel level topographic correction and show that in rough terrain, the sub-pixel topography correction method provides better results even if it tends to slightly overestimate the retrieved land surface reflectance in some cases.Geoscience & Remote SensingCivil Engineering and Geoscience
Correction of sub-pixel topographical effects on land surface albedo retrieved from geostationary satellite (FengYun-2D) observations
Full text linkThe Qinghai-Tibetan Plateau is characterised by a very strong relief which affects albedo retrieval from satellite data. The objective of this study is to highlight the effects of subpixel topography and to account for those effects when retrieving land surface albedo from geostationary satellite FengYun-2D (FY-2D) data with 1.25km spatial resolution using the high spatial resolution (30 m) data of the Digital Elevation Model (DEM) from ASTER. The methodology integrates the effects of sub-pixel topography on the estimation of the total irradiance received at the surface, allowing the computation of the topographically corrected surface reflectance. Furthermore, surface albedo is estimated by applying the parametric BRDF (Bidirectional Reflectance Distribution Function) model called RPV (Rahman-Pinty-Verstraete) to the terrain corrected surface reflectance. The results, evaluated against ground measurements collected over several experimental sites on the Qinghai-Tibetan Plateau, document the advantage of integrating the sub-pixel topography effects in the land surface reflectance at 1km resolution to estimate the land surface albedo. The results obtained after using sub-pixel topographic correction are compared with the ones obtained after using pixel level topographic correction. The preliminary results imply that, in highly rugged terrain, the sub-pixel topography correction method gives more accurate results. The pixel level correction tends to overestimate surface albedo.Geoscience & EngineeringCivil Engineering and Geoscience
'Conventions are conventions.....’: Some thoughts about the techniques of direction and misdirection – with particular reference to genre features - in the novels of Vladimir Nabokov, and an assessment of their intentions and effects.
Full text linkThe thesis deals with the development of Nabokov's treatment of a number of the more common routes and courses which are traditionally supplied by the author to ease the passage of the reader through fiction. It attempts to show how these marked paths and familiar signposts - 'melodrama,' 'totalitarian novel,' 'biography,' 'erotic confession,' 'critical edition,' 'family chronicle, 'mystery story,' and 'autobiographical confession' - emerge in the books as equally misguiding and misguided. The satisfactory application of such labels is demonstrated as becoming progressively more difficult as the novels proceed, with a rising degree of sophistication, to incorporate distinctive combinations of genre features usually considered as mutually exclusive. Further inquiries into the manner of fictional orientation and location encouraged by this regular disappointment of apparently familiar leads and landmarks, however, is increasingly seen to disclose the underlying procedures and desires of the reader to place and confine narrative. The manner in which Nabokov's reader is repeatedly obliged to return to a non-metaphorical 'first base' by way of these false trails, which seemingly point towards an authoritative text, and there to re-examine his own imaginative input is also traced..... Dull work recounting all this bores me to death. But yearn as I may to reach the crucial point quickly, a few preliminary explanations seem necessary
Modelling and observation of heat losses from buildings: The impact of geometric detail on 3D heat flux modelling
No full textThe impact of 3D geometry complexity on the accuracy of simulating radiative, convective and conductive fluxes in an urban canyon was explored. The research involved the collection of meteorological data in an urban canyon in the city of Strasbourg, France, for input into a 3D model called LASER/F, which simulates the aforementioned fluxes. The key input into LASER/F is a 3D geometric model representing the scene (urban canyon). It was hypothesized that more geometric detail in the model would lead to improved accuracy in the simulation but increased computing time. To test this, seven geometry scenarios were prepared with different complexities and test run in LASER/F. The results were validated with thermal images of two facades collected during the field campaign in Strasbourg. The results show that LASER/F systematically underestimates facade surface temperatures possibly due to various model assumptions and input geometry. One of those is the oversimplified 1D parameterization of the vertical wind profile and was demonstrated by comparing it with a vertical wind profile extracted from a CFD model. It was concluded that the most complex 3D geometry does not necessarily improve simulation accuracy, especially during warming periods of the day, but does affect simulation time. The inclusion of balconies on the facades is influential and should be used for future simulation experiments when it is a significant feature of a facade. This implies that 3D simulations for the management of urban heat at canyon scale will need to consider the particularities of facades on a case-by-case basis when determining level of detail required for the input geometry. Further research is required to better understand canyon geometry effects such as canyon orientation, aspect ratio and the volumetric influence on internal heat storage in buildings. The investigation was carried out in association with ICube Laboratory (UMR 7357 CNRS-Université de Strasbourg), for the 2012 Geomatics Synthesis Project.Geoscience & Remote SensingCivil Engineering and Geoscience
Sosialisasi Pemanfaatan Digital Marketing Pada (UMKM) Toko Baju Tulip Bengkulu
Full text linkThis proposal outlines a socialization plan for the use of digital marketing at Toko Baju Tulip in Bengkulu. The main objective is to improve the knowledge and skills of the store owner and employees in using digital platforms to promote and sell their products. With this training, the store is expected to increase sales and expand market reach. This research uses a descriptive qualitative method. The power needed as a research knife is primary data which the author obtained by observation and interviews with parties related to this research. Secondary data is obtained from various books, journal articles, and other supporting literature. While the results of this study are in the form of: first, based on the opinions of MSME business owners who improve their performance through digital marketing only by creating interesting content and easy for people to remember. Second, based on the opinions of MSME enthusiasts and customers, “Toko Baju Tulip” can reduce costs and can be a strong competitor for those who do not use digital marketing. Third, based on the opinion of the general public, MSMEs do need increased work in terms of digital marketing to introduce the product identity and corporate identity of MSMEs in an era that uses the internet
Angular Normalization of Land Surface Temperature and Emissivity Using Multiangular Middle and Thermal Infrared Data
No full textThis paper aimed at the case of nonisothermal pixels and proposed a daytime temperature-independent spectral indices (TISI) method to retrieve directional emissivity and effective temperature from daytime multiangular observed images in both middle and thermal infrared (MIR and TIR) channels by combining the kernel-driven bidirectional reflectance distribution function (BRDF) model and the TISI method. Four groups of angular observations and two groups of MIR and TIR channels with narrow and broad bandwidths were used to investigate the influence of angular observations and bandwidth on the retrieval accuracy. Model sensitivity analysis indicated that the new method can generally obtain directional emissivity and temperature with an error less than 0.015 and 1.5 K if the noise included in the measured directional brightness temperature (DBT) and atmospheric data was no more than 1.0 K and 10%, respectively. The analysis also indicated that 1) large-angle intervals among the angular observations and a larger viewing zenith angle, with respect to nadir direction, can improve the retrieval accuracy because those angle conditions can result in significant difference for components' fractions and DBT under different viewing directions; 2) narrow channels can produce better results than broad channels. The new method was finally applied to a multiangular MIR and TIR data set acquired by an airborne system, and a modified kernel-driven BRDF model was used for angular normalization to the surface temperature for the first time. The difference of the retrieved emissivity and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) emissivity was found to be approximately 0.012 in the study area.Geochemistry & GeophysicsEngineering, Electrical & ElectronicRemote SensingImaging Science & Photographic TechnologySCI(E)[email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
