Search results for "ALBEDO"
showing 10 items of 110 documents
Atmospheric radiative effects of an in-situ measured Saharan dust plume and the role of large particles
2007
This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 μm. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the lar…
Évaluation des effets thermiques des leviers d'action visant à réduire l'îlot de chaleur urbain : l'exemple de Dijon.
2017
Climate Change and Urban Heat Island (UHI) combine their effects and lead to increased frequencies and intensities of heat waves in urban environments. Considering the associated public health issues, several actions are possible: the color of the materials, the development of water surfaces or urban vegetation. In Dijon, a network of 60 stations makes it possible to evaluate the potential of these three actions. Analysis of the warm summer 2016 season reveals that the refreshing role of water only occurs during daytime, the effect of bright surfaces (concrete versus bitumen) on the air temperature is only a few tenths of a degree, while vegetation offers the largest refreshing potential. I…
Performances of neural networks for deriving LAI estimates from existing CYCLOPES and MODIS products
2008
International audience; This paper evaluates the performances of a neural network approach to estimate LAI from CYCLOPES and MODIS nadir normalized reflectance and LAI products. A data base was generated from these products over the BELMANIP sites during the 2001-2003 period. Data were aggregated at 3 km x 3 km, resampled at 1/16 days temporal frequency and filtered to reject outliers. VEGETATION and MODIS reflectances show very consistent values in the red, near infrared and short wave infrared bands. Neural networks were trained over part of this data base for each of the 6 MODIS biome classes to retrieve both MODIS and CYCLOPES LAI products. Results show very good performances of neural …
Assessment of the Trend of Albedo: a Case Study of Palermo
2013
In this paper we propose a case study of urban heat island applied to Palermo. The urban heat island (UHI) is the most studied of the climate effects of settlements. The UHI refers to the generally warm urban temperatures compared to those over surrounding, non-urban, areas. The aim of this paper is to find a connection among the average rise in temperature and the modification of albedo.
A new calibration of the effective scattering albedo and soil roughness parameters in the SMOS SM retrieval algorithm
2017
Abstract This study focuses on the calibration of the effective vegetation scattering albedo (ω) and surface soil roughness parameters (H R , and N Rp , p = H,V) in the Soil Moisture (SM) retrieval from L-band passive microwave observations using the L-band Microwave Emission of the Biosphere (L-MEB) model. In the current Soil Moisture and Ocean Salinity (SMOS) Level 2 (L2), v620, and Level 3 (L3), v300, SM retrieval algorithms, low vegetated areas are parameterized by ω = 0 and H R = 0.1, whereas values of ω = 0.06 − 0.08 and H R = 0.3 are used for forests. Several parameterizations of the vegetation and soil roughness parameters (ω, H R and N Rp , p = H,V) were tested in this study, tre…
SMOS-IC: An Alternative SMOS Soil Moisture and Vegetation Optical Depth Product
2017
© 2017 by the authors. The main goal of the Soil Moisture and Ocean Salinity (SMOS) mission over land surfaces is the production of global maps of soil moisture (SM) and vegetation optical depth (τ) based on multi-angular brightness temperature (TB) measurements at L-band. The operational SMOS Level 2 and Level 3 soil moisture algorithms account for different surface effects, such as vegetation opacity and soil roughness at 4 km resolution, in order to produce global retrievals of SM and τ. In this study, we present an alternative SMOS product that was developed by INRA (Institut National de la Recherche Agronomique) and CESBIO (Centre d'Etudes Spatiales de la BIOsphère). One of the main go…
Enhancing values of roofs albedo for lowering cities’ air temperature and electric demand of buildings: a simple economic evaluation
2019
Abstract In cities vegetated roofs are becoming more popular because they can mitigate Urban Heat Island phenomena by decreasing the outdoor air temperature in summer. This decrease reduces the electric energy demand for climatization of buildings, which, in front of a milder climate, will recur less to mechanical tools for guaranteeing thermal comfort conditions to occupants. Cities can registered another indirect positive effect: the reduced cooling energy demand, limits the heat released by the climatization systems’ external unities toward the urban open spaces, thus lowering the outdoor air temperature. Therefore, the outdoor surface temperature of green, as well as cool roofs, can be …
Solar radiative effects of a Saharan dust plume observed during SAMUM assuming spheroidal model particles
2011
The solar optical properties of Saharan mineral dust observed during the Saharan Mineral Dust Experiment (SAMUM) were explored based on measured size-number distributions and chemical composition. The size-resolved complex refractive index of the dust was derived with real parts of 1.51–1.55 and imaginary parts of 0.0008–0.006 at 550 nm wavelength. At this spectral range a single scattering albedo ω o and an asymmetry parameter g of about 0.8 were derived. These values were largely determined by the presence of coarse particles. Backscatter coefficients and lidar ratios calculated with Mie theory (spherical particles) were not found to be in agreement with independently measured lidar data.…
Termālā stāvokļa modelēšana un zaļās infrastruktūras nozīme Rīgas centrā
2021
Globālo klimatu pārmaiņu rezultātā tiek prognozēti biežāki un ekstremālāki laika apstākļi īpaši pilsētu teritorijās. Ekstrēmāla karstuma parādība un pilsētu karstuma salas ir svarīgi faktori, kas ietekmē sabiedrības veselību un dzīves kvalitāti. Viens no risinājumiem karstuma salas ietekmes mazināšanā ir veģetācija, kas veicina iztvaikošanas un dzesēšanas efektu, taču pilsētās bieži vien to daudzums nav pietiekošs. Maģistra darbā novērtēta zaļās infrastruktūras nozīme karstuma viļņu laikā Rīgas centrā (Brīvības ielā 73, Dzirnavu ielā 91, Lāčplēša ielā 3, Kr. Valdemāra ielā 18 un Aspazijas bulvārī 5), izmantojot modelēšanas metodi. Termālā stāvokļa modelēšanai izmantota programmatūra Envi-me…
Saules radiācijas izkliede un atstarošana dažāda tipa mākoņos virs Latvijas teritorijas 2005. - 2011. gados
2016
Bakalaura darbā “Saules radiācijas izkliede un atstarošana dažāda tipa mākoņos virs Latvijas teritorijas 2005. - 2011. gados” tik pētīta dažāda tipa mākoņu ietekme uz Saules radiācijas izkliedi un atstarošanu, balstoties uz satelītu datu rindām. Pētījuma mērķis ir izvērtēt mākoņu lomu Saules radiācijas izkliedes un atstarošanas procesos. Darbs sastāv no 3 daļām. Tā pirmajā daļā ir apkopota informācija par pētāmām tēmām. Otrajā daļā aprakstītas datu ievākšanas un apstrādes metodes. Trešajā daļā aprakstīti datu apstrādes rezultāti, kuri liecina, ka dažādu mākoņu tipu ietekme uz Saules radiāciju savstarpēji būtiski neatšķiras. Darbs satur 52 lappuses, 4 tabulas, 29 attēlus, 2 pielikumus, 19 bi…