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

2010 ◽  
Vol 115 (D14) ◽  
Author(s):  
Eike Bierwirth ◽  
Manfred Wendisch ◽  
Evelyn Jäkel ◽  
André Ehrlich ◽  
K. Sebastian Schmidt ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Flux Density ◽  
New Method ◽  
Aerosol Layer ◽  
Actinic Radiation ◽  
Radiation Measurements

A New Method to Measure the Absorption Coefficient of the Automotive Driving Room Based on the Sound Pressure Delaying

2011 ◽  
Vol 415-417 ◽  
pp. 1350-1354
Author(s):  
Cong Yun Zhu ◽  
Jian Ru Shi ◽  
Shu Feng Yang
Keyword(s):  
Absorption Coefficient ◽  
Standing Wave ◽  
Sound Pressure ◽  
Measurement Methods ◽  
The Other ◽  
New Method ◽  
Wave Tube ◽  
Absorption Function ◽  
Equal Distance ◽  
Standing Wave Tube

Absorption coefficient is an important parameter of the absorption function of the absorption material. Traditional measurement methods of absorption coefficient are standing wave tube and reverberation which have some shortcomings. In this paper, phase of the sound pressure measured by two equal distance microphones placed in the front of the absorption material is delayed in order to attain the absorption coefficient. At the last, an experiment for one absorption material is carried out, the experiment results compare with the results of the other methods above mentioned that denotes that the theory is correct and practicable.

scholarly journals Year-round stratospheric aerosol backscatter ratios calculated from lidar measurements above northern Norway

2019 ◽  
Vol 12 (7) ◽  
pp. 4065-4076 ◽  
Author(s):  
Arvid Langenbach ◽  
Gerd Baumgarten ◽  
Jens Fiedler ◽  
Franz-Josef Lübken ◽  
Christian von Savigny ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
Stratospheric Aerosol ◽  
New Method ◽  
The Arctic ◽  
Correction Function ◽  
Aerosol Layer ◽  
Radiative Balance ◽  
Northern Norway ◽  
Lidar Measurements ◽  
Aerosol Backscatter

Abstract. We present a new method for calculating backscatter ratios of the stratospheric sulfate aerosol (SSA) layer from daytime and nighttime lidar measurements. Using this new method we show a first year-round dataset of stratospheric aerosol backscatter ratios at high latitudes. The SSA layer is located at altitudes between the tropopause and about 30 km. It is of fundamental importance for the radiative balance of the atmosphere. We use a state-of-the-art Rayleigh–Mie–Raman lidar at the Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) station located in northern Norway (69∘ N, 16∘ E; 380 m a.s.l.). For nighttime measurements the aerosol backscatter ratios are derived using elastic and inelastic backscatter of the emitted laser wavelengths 355, 532 and 1064 nm. The setup of the lidar allows measurements with a resolution of about 5 min in time and 150 m in altitude to be performed in high quality, which enables the identification of multiple sub-layers in the stratospheric aerosol layer of less than 1 km vertical thickness. We introduce a method to extend the dataset throughout the summer when measurements need to be performed under permanent daytime conditions. For that purpose we approximate the backscatter ratios from color ratios of elastic scattering and apply a correction function. We calculate the correction function using the average backscatter ratio profile at 355 nm from about 1700 h of nighttime measurements from the years 2000 to 2018. Using the new method we finally present a year-round dataset based on about 4100 h of measurements during the years 2014 to 2017.

scholarly journals A New Method to Calibrate Shortwave Solar Radiation Measurements

2014 ◽  
Vol 31 (6) ◽  
pp. 1321-1329 ◽  
Author(s):  
Jinhuan Qiu ◽  
Xiangao Xia ◽  
Jianghui Bai ◽  
Pucai Wang ◽  
Xuemei Zong ◽  
...  
Keyword(s):  
New Method ◽  
Radiative Transfer Model ◽  
Maximum Deviation ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Calibration Transfer ◽  
The World ◽  
Potential Applications ◽  
Atmospheric Transmittance ◽  
Radiation Measurements

Abstract A method is proposed to simultaneously calibrate shortwave (0.3–4 μm) global, direct, and scattering solar irradiance (GSI, DSI, and SSI, respectively) measurements. The method uses the World Radiation Reference (WRR) as a calibration standard and on-site radiation measurements as inputs. Two simple but effective techniques are used in the calibration. The first is to scale SSI and GSI detection sensitivities under overcast skies, which is based on the assumption that SSI should be equal to GSI if DSI is completely scattered and absorbed. The second is a new method to retrieve aerosol optical thickness (AOT), using the ratio of horizontal DSI (HDSI) to GSI measurements under clear and clean conditions. Thereafter, retrieved AOTs are used to drive a radiative transfer model to calculate atmospheric transmittance and then a ratio of GSI to the transmittance. Deviation of this ratio to the WRR is regarded as an indicator of GSI uncertainty, and the calibration transfer coefficient is derived as the WRR ratio. The method is applied to calibrate radiation measurements at Xianghe, China, during 2005. It is estimated from the derived transfer coefficients on 36 clear and clean days that uncertainties of DSI, GSI, and SSI measurements are within −4.0% to 2.9%, −5.9% to 2.4%, and −6.1% to 4.9%, respectively. The calibration is further validated based on comparisons of AOT at 750 nm retrieved from HDSI/GSI to Aerosol Robotic Network (AERONET) AOT products. The maximum deviation between two AOT products is 0.026. The unique advantage of this method lies in its potential applications in correcting historic radiation measurements and monitoring radiometer performance.

scholarly journals Influence of clouds on the spectral actinic flux density in the lower troposphere (INSPECTRO): overview of the field campaigns

2008 ◽  
Vol 8 (6) ◽  
pp. 1789-1812 ◽  
Author(s):  
S. Thiel ◽  
L. Ammannato ◽  
A. Bais ◽  
B. Bandy ◽  
M. Blumthaler ◽  
...  
Keyword(s):  
Flux Density ◽  
Radiation Field ◽  
Radiation Transfer ◽  
Three Dimensional ◽  
Transfer Model ◽  
Model Calculations ◽  
Actinic Flux ◽  
Airborne Measurements ◽  
Actinic Radiation ◽  
Radiation Transfer Model

Abstract. Ultraviolet radiation is the key factor driving tropospheric photochemistry. It is strongly modulated by clouds and aerosols. A quantitative understanding of the radiation field and its effect on photochemistry is thus only possible with a detailed knowledge of the interaction between clouds and radiation. The overall objective of the project INSPECTRO was the characterization of the three-dimensional actinic radiation field under cloudy conditions. This was achieved during two measurement campaigns in Norfolk (East Anglia, UK) and Lower Bavaria (Germany) combining space-based, aircraft and ground-based measurements as well as simulations with the one-dimensional radiation transfer model UVSPEC and the three-dimensional radiation transfer model MYSTIC. During both campaigns the spectral actinic flux density was measured at several locations at ground level and in the air by up to four different aircraft. This allows the comparison of measured and simulated actinic radiation profiles. In addition satellite data were used to complete the information of the three dimensional input data set for the simulation. A three-dimensional simulation of actinic flux density data under cloudy sky conditions requires a realistic simulation of the cloud field to be used as an input for the 3-D radiation transfer model calculations. Two different approaches were applied, to derive high- and low-resolution data sets, with a grid resolution of about 100 m and 1 km, respectively. The results of the measured and simulated radiation profiles as well as the results of the ground based measurements are presented in terms of photolysis rate profiles for ozone and nitrogen dioxide. During both campaigns all spectroradiometer systems agreed within ±10% if mandatory corrections e.g. stray light correction were applied. Stability changes of the systems were below 5% over the 4 week campaign periods and negligible over a few days. The J(O1D) data of the single monochromator systems can be evaluated for zenith angles less than 70°, which was satisfied by nearly all airborne measurements during both campaigns. The comparison of the airborne measurements with corresponding simulations is presented for the total, downward and upward flux during selected clear sky periods of both campaigns. The compliance between the measured (from three aircraft) and simulated downward and total flux profiles lies in the range of ±15%.

scholarly journals Inference of the microwave absorption coefficient from stray radiation measurements in Wendelstein 7-X

2016 ◽  
Vol 57 (3) ◽  
pp. 036013 ◽  
Author(s):  
D. Moseev ◽  
H.P. Laqua ◽  
S. Marsen ◽  
N. Marushchenko ◽  
T. Stange ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Microwave Absorption ◽  
Stray Radiation ◽  
Radiation Measurements

The Simulation of Apparent Directional Emissivity in a Three-Dimensional Non-Isothermal Medium by the DRESOR Method

2011 ◽  
Author(s):  
Qiang Cheng ◽  
Xiang-Yu Zhang ◽  
Zhi-Chao Wang ◽  
Huai-Chun Zhou ◽  
Lv-Bin Wu
Keyword(s):  
Absorption Coefficient ◽  
Glass Melting ◽  
Three Dimensional ◽  
Heating Furnace ◽  
New Method ◽  
Scattering Coefficient ◽  
New Approach ◽  
Isothermal Medium ◽  
Directional Emissivity ◽  
Industrial Heating

The emissivity as a thermal property plays an important role required for heat transfer calculations and temperature measurement. In an isothermal purely absorption medium, the emissivity can be calculated by the formula, but no general formula for the emissivity will suit the system with scattering of medium and reflection of walls in a coal-fired boiler or an industrial heating furnace. In this study, a new approach was proposed to scale the apparent field directional emissivity by DRESOR method combined with two-color method in a three-dimensional non-isothermal participating medium with reflection of walls. The results obtained by the new method were compared with those calculated by the formula to verify the validity and accuracy of new method in an isothermal purely absorption medium. Then the new method was extended to examine the effect of absorption coefficient, scattering coefficient and reflection of walls on the apparent directional emissivity in the isothermal and non-isothermal cases. It is found that when there is scattering in the medium, the emissivity cannot be equal to the entity, even if the medium is optically thick. In the condition of walls with cold or low temperature, such as in the case of a coal-fired boiler, the apparent emissivity increases with the increase of absorption coefficient and reflectivity of walls, because radiation from hot media plays a dominated role in emissivity in this situation; Meanwhile, in the case of walls with high temperature, such as in the case of an industrial heating furnace in metallurgy or glass melting industry, the apparent emissivity decreases with the increase of absorption coefficient, because the emissivity is mainly determined by the wall radiation in this situation. And when scattering coefficient increases, the apparent emissivity decreases for all isothermal and non-isothermal cases.

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