Search results for "BED"

Modeling the outdoor cooling impact of highly radiative “super cool” materials applied on roofs

2021

Abstract Highly reflective “cool materials” are commonly used to reduce temperatures in the urban environment. Recently developed “super cool” materials feature an even higher albedo and emissivity (both above 0.95) than traditional cool materials. To examine the impacts of super cool roofing materials on outdoor air temperature compared to traditional cool roofs and green roofs, we conduct a sensitivity study with the microclimate model ENVI-met. Simulated surface temperature of super cool roofs remained around 6 K below ambient air temperature during high solar irradiation, which is consistent with observations. Super cool roofs – with an averaged street-level air temperature cooling of a…

A new method to retrieve the aerosol layer absorption coefficient from airborne flux density and actinic radiation measurements

2010

A new method is presented to derive the mean value of the spectral absorption coefficient of an aerosol layer from combined airborne measurements of spectral net irradiance and actinic flux density. While the method is based on a theoretical relationship of radiative transfer theory, it is applied to atmospheric radiation measurements for the first time. The data have been collected with the Spectral Modular Airborne Radiation Measurement System (SMARTA¢Â€ÂAlbedometer), the Solar Spectral Flux Radiometer (SSFR), and the Actinic Flux Spectroradiometer (AFSR) during four field campaigns between 2002 and 2008 (the Saharan Mineral Dust Experiment (SAMUM), the Influence of Clouds on the Spectra…

In situ measurements of optical properties at Tinfou (Morocco) during the Saharan Mineral Dust Experiment SAMUM 2006

2009

In situ measurements of optical and physical properties of mineral dust were performed at the outskirts of the Saharan Desert in the framework of the Saharan Mineral Dust Experiment part 1 (SAMUM-1). Goals of the field study were to achieve information on the extent and composition of the dust particle size distribution and the optical properties of dust at the ground. For the particle number size distribution, measured with a DMPS/APS, a size dependent dynamic shape factor was considered. The mean refractive index of the particles in this field study is 1.53–4.1 × 10 -3 i at 537 nm wavelength and 1.53–3.1 × 10 -3 i at 637 nm wavelength derived from measurements of scattering and absorption…

Approximation for the absorption coefficient of airborne atmospheric aerosol particles in terms of measurable bulk properties

1977

The absorption coefficient of airborne atmospheric aerosol particles can be approximated by where λ is the wavelength of radiation, n — ik is the mean complex refractive index, ρ the mean bulk density, and M / V k the mass of the particles per unit volume of air. This approximation gives good results at relative humidities between 0 and 0.95 for the wavelengths of radiation between 0.55 μm and 2.0 μm and between 9.25 μm and 12.0 μm. Basing on this approximation it is possible to determine the single scattering albedo of airborne atmospheric aerosol particles with known measuring techniques. DOI: 10.1111/j.2153-3490.1977.tb00711.x

The Single-Scattering Albedo of Atmospheric Aerosol Particles as a Function of Relative Humidity

1976

The surface shortwave net flux from the scanner for radiation budget (SCARAB)

2002

Abstract Shortwave surface net radiation is usually determined by combining the measurement of insolation with an independent estimate of surface albedo. However, uncertainties associated with each of these quantities may lead to large errors in the value of net surface solar radiation. An alternative approach is to deduce the net solar flux (the term flux is used here as the radiometric quantity flux density) at the surface directly from the budget at the top of the atmosphere, without explicit knowledge of surface albedo. The Satellite Application Facility on Climate Monitoring is a joint project of the German Meteorological Service and other European Meteorological Services dedicated to …

Comparison of AERONET and SKYRAD4.2 inversion products retrieved from a Cimel CE318 sunphotometer

2012

SKYNET is an international research network of ground based sky – sunphotometers for the observation and monitoring of columnar aerosol properties. The algorithm developed by SKYNET is called SKYRAD.pack, and it is used on Prede instruments only. In this study, we have modified the SKYRAD.pack software in order to adapt it to Cimel sunphotometers. A one month database of Cimel data obtained at Burjassot (Valencia, Spain) has been processed with this program and the obtained inversion products have been compared with AERONET retrievals. In general, the differences found were consistent with the individual error assessments for both algorithms. Although the aerosol optical depth com…

Effective cloud optical depth for overcast conditions determined with a UV radiometers

2014

Using a sky camera, episodes characterized by overcast low clouds in the Valencia region of Spain have been selected for analysis. One year of cloud optical depth data have been produced by inverting UV erythemal irradiance measured with a UVB-1 radiometer from Yankee Environmental Systems using the LibRadtran radiative transfer model. Measurement uncertainties, aerosol single scattering albedo and cloud properties are, in order of decreasing importance, the most important factors influencing the accuracy of cloud optical depth retrieval when using UV erythemal radiometers. Statistics for cloud optical depth show a highly skewed frequency distribution best described by a gamma distribution …

Incorporation of aerosol effects in a clear-sky semi-empirical model of UVER radiation for Valencia, Spain

2011

The study develops a simple but physically based model for estimating erythemal irradiance [(UV erythemal radiation (UVER)] for cloudless urban regions with substantial aerosol load, such as that of the Valencia environment in Spain. The model estimates direct and diffuse UVER for cloudless aerosol-free conditions using the LibRadtran model with a DISORT algorithm. Aerosol optical thickness for UVER (τaER) is obtained as a residual term by comparing measured direct UVER against modelled direct UVER in the absence of aerosol load. On average, τaER is 18% higher than τ data extrapolated to 305 nm using the CIMEL CE-318. Comparison of measured direct and diffuse UVER with model estimates provi…

Sensitivity of the atmospheric temperature profile to the aerosol absorption in the presence of dust

2014

Abstract Radiative transfer simulations in the shortwave (SW) and longwave (LW) spectral regions have been carried out to investigate the time evolution of the atmospheric heating/cooling rates and their influence on the temperature profiles under different vertical distributions of the aerosol absorption. The case study is based on measurements made at Rome, Italy, on 20 June 2007, when a dust layer was present above the urban boundary layer (BL) and the column aerosol optical depth at 550 nm was about 0.37. Column-integrated aerosol optical depth and single scattering albedo, as well as vertical profiles of aerosol extinction and meteorological variables have been derived from observation…