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 Description of the Baseline Surface Radiation Network (BSRN) station at the Izaña Observatory (2009–2017): measurements and quality control/assurance procedures

2019 ◽  
Vol 8 (1) ◽  
pp. 77-96 ◽  
Author(s):  
Rosa Delia García ◽  
Emilio Cuevas ◽  
Ramón Ramos ◽  
Victoria Eugenia Cachorro ◽  
Alberto Redondas ◽  
...  
Keyword(s):  
Quality Control ◽  
Research Programme ◽  
Surface Radiation ◽  
Shortwave Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
High Mountain ◽  
Total Column Ozone ◽  
The World ◽  
Instantaneous Values

Abstract. The Baseline Surface Radiation Network (BSRN) was implemented by the World Climate Research Programme (WCRP) starting observations with nine stations in 1992, under the auspices of the World Meteorological Organization (WMO). Currently, 59 BSRN stations submit their data to the WCRP. One of these stations is the Izaña station (station IZA, no. 61) that enrolled in this network in 2009. This is a high-mountain station located in Tenerife (Canary Islands, Spain, at 28.3∘ N, 16.5∘ W; 2373 m a.s.l.) and is a representative site of the subtropical North Atlantic free troposphere. It contributes with basic-BSRN radiation measurements, such as global shortwave radiation (SWD), direct radiation (DIR), diffuse radiation (DIF) and longwave downward radiation (LWD), and extended-BSRN measurements, including ultraviolet ranges (UV-A and UV-B), shortwave upward radiation (SWU) and longwave upward radiation (LWU), and other ancillary measurements, such as vertical profiles of temperature, humidity and wind obtained from radiosonde profiles (WMO station no. 60018) and total column ozone from the Brewer spectrophotometer. The IZA measurements present high-quality standards since more than 98 % of the data are within the limits recommended by the BSRN. There is an excellent agreement in the comparison between SWD, DIR and DIF (instantaneous and daily) measurements with simulations obtained with the LibRadtran radiative transfer model. The root mean square error (RMSE) for SWD is 2.28 % for instantaneous values and 1.58 % for daily values, while the RMSE for DIR is 2.00 % for instantaneous values and 2.07 % for daily values. IZA is a unique station that provides very accurate solar radiation data in very contrasting scenarios: most of the time under pristine sky conditions and periodically under the effects of the Saharan air layer characterized by a high content of mineral dust. A detailed description of the BSRN program at IZA, including quality control and quality assurance activities, is given in this work.

scholarly journals Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements

2003 ◽  
Vol 3 (2) ◽  
pp. 377-385 ◽  
Author(s):  
A. Kylling ◽  
T. Danielsen ◽  
M. Blumthaler ◽  
J. Schreder ◽  
B. Johnsen
Keyword(s):  
State Of The Art ◽  
Spectral Characteristics ◽  
Calibration Procedure ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Balloon Flight ◽  
Center Wavelength ◽  
Model Simulations ◽  
Stratospheric Balloon ◽  
Radiation Measurements

Abstract. A new ligthweight multichannel moderate bandwidth filter instrument designed to be flown on balloons, is described. The instrument measures the radiation field within the short UV (center wavelength at 312 nm) and long UV (center wavelength at 340 nm). The angular and spectral characteristics of the instrument are discussed and the calibration procedure outlined. Measurements made during a stratospheric balloon flight at twilight conditions from Gap-Tallard, France, are presented and compared with state-of-the-art radiative transfer model simulations. The model simulations and the measurements agree within ±10% (±20%) for solar zenith angles smaller than 93° (90°) for the 340 (312) nm channel. Based on the model simulations of the measured radiation, actinic flux spectra are reconstructed. These are used to calculate various photodissociation rates.

scholarly journals Aerosol retrievals from the EKO MS-711 spectral direct irradiance measurements and corrections of the circumsolar radiation

2020 ◽  
Vol 13 (5) ◽  
pp. 2601-2621
Author(s):  
Rosa Delia García-Cabrera ◽  
Emilio Cuevas-Agulló ◽  
África Barreto ◽  
Victoria Eugenia Cachorro ◽  
Mario Pó ◽  
...  
Keyword(s):  
Field Of View ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Mean Square ◽  
Aerosol Scattering ◽  
The World ◽  
Uv Visible ◽  
Sun Photometer ◽  
Comparison Of The Results ◽  
Uv Range

Abstract. Spectral direct UV–visible normal solar irradiance (DNI) has been measured with an EKO MS-711 grating spectroradiometer, which has a spectral range of 300–1100 nm, and 0.4 nm step, at the Izaña Atmospheric Observatory (IZO, Spain). It has been used to determine aerosol optical depth (AOD) at several wavelengths (340, 380, 440, 500, 675, and 870 nm) between April and September 2019, which has been compared with synchronous AOD measurements from a reference Cimel and Aerosol RObotic NETwork (AERONET) sun photometer. The EKO MS-711 has been calibrated at the Izaña Atmospheric Observatory by using the Langley plot method during the study period. Although this instrument has been designed for spectral solar DNI measurements, and therefore has a field of view (FOV) of 5∘ that is twice the recommended amount in solar photometry for AOD determination, the AOD differences compared to the AERONET–Cimel reference instrument (FOV ∼1.2∘) are fairly small. A comparison of the results from the Cimel AOD and EKO MS-711 AOD presents a root mean square (rms) of 0.013 (24.6 %) at 340 and 380 nm, and 0.029 (19.5 %) for longer wavelengths (440, 500, 675, and 870 nm). However, under relatively high AOD, near-forward aerosol scattering might be significant because of the relatively large circumsolar radiation (CSR) due to the large EKO MS-711 FOV, which results in a small but significant AOD underestimation in the UV range. The AOD differences decrease considerably when CSR corrections, estimated from libRadtran radiative transfer model simulations, are performed and obtain an rms of 0.006 (14.9 %) at 340 and 380 nm, and 0.005 (11.1 %) for longer wavelengths. The percentage of 2 min synchronous EKO AOD–Cimel AOD differences within the World Meteorological Organization (WMO) traceability limits were ≥96 % at 500, 675, and 870 nm with no CSR corrections. After applying the CSR corrections, the percentage of AOD differences within the WMO traceability limits increased to >95 % for 380, 440, 500, 675, and 870 nm, while for 340 nm the percentage of AOD differences showed a poorer increase from 67 % to a modest 86 %.

scholarly journals Description of the Baseline Surface Radiation Network (BSRN) station at the Izaña Observatory (2009–2017): measurements and quality control/assurance procedures

2018 ◽  
Author(s):  
Rosa Delia García ◽  
Emilio Cuevas ◽  
Ramón Ramos ◽  
Victoria Eugenia Cachorro ◽  
Alberto Redondas ◽  
...  
Keyword(s):  
Quality Control ◽  
Research Programme ◽  
Surface Radiation ◽  
Shortwave Radiation ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
High Mountain ◽  
Total Column Ozone ◽  
The World ◽  
Instantaneous Values

Abstract. The Baseline Surface Radiation Network (BSRN) was implemented by the World Climate Research Programme (WRCP) starting observations with 9 stations in 1992, under the auspices of the World Meteorological Organization (WMO). Currently, 59 BSRN stations submit their data to the WRCP. One of these stations is the Izaña station (Station: IZA, #61) that enrolled in this network in 2009. This is a high-mountain station located in Tenerife (Canary Islands, Spain; at 28.3° N, 16.5° W, 2373 m a.s.l.) and is a representative site of the subtropical North Atlantic free troposphere. It contributes with basic-BSRN radiation measurements, such as, global shortwave radiation (SWD), direct radiation (DIR), diffuse radiation (DIF) and longwave downward radiation (LWD) and extended-BSRN measurements, including ultraviolet ranges (UV-A and UV-B), shortwave upward radiation (SWU) and longwave upward radiation (LWU) and other ancillary measurements, such as vertical profiles of temperature, humidity and wind obtained from radiosonde (WMO, station #60018) and total column ozone from Brewer spectrophotometer. The IZA measurements present high quality standards since more than 98 % of the data are within the limits recommended by the BSRN. There is an excellent agreement in the comparison between SWD, DIR and DIF (instantaneous and daily) measurements with simulations obtained with the LibRadtran radiative transfer model. The root mean square error (RMSE) for SWD is 2.28 % for instantaneous values and 1.58 % for daily values, while the RMSE for DIR is 2.00 % for instantaneous values and 2.07 % for daily values. IZA is a unique station that provides very accurate solar radiation data in very contrasting scenarios: most of the time under pristine sky conditions, and periodically under the effects of the Saharan Air Layer characterized by a high content of mineral dust. A detailed description of the BSRN program at IZA, including quality control and quality assurance activities, is given in this work.

scholarly journals Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements

2002 ◽  
Vol 2 (3) ◽  
pp. 715-738
Author(s):  
A. Kylling ◽  
T. Danielsen ◽  
M. Blumthaler ◽  
J. Schreder ◽  
B. Johnsen
Keyword(s):  
State Of The Art ◽  
Spectral Characteristics ◽  
Calibration Procedure ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Balloon Flight ◽  
Center Wavelength ◽  
Model Simulations ◽  
Stratospheric Balloon ◽  
Radiation Measurements

Abstract. A new ligthweight multichannel moderate bandwidth filter instrument designed to be flown on balloons, is described. The instrument measures the radiation field within the short UV (center wavelength at 312nm) and long UV (center wavelength at 340nm). The angular and spectral characteristics of the instrument are discussed and the calibration procedure outlined. Measurements made during a stratospheric balloon flight at twilight conditions from Gap-Tallard, France, are presented and compared with state-of-the-art radiative transfer model simulations. The model simulations and the measurements agree within ±10% (±20%) for solar zenith angles smaller than 93° (90°) for the 340 (312)nm channel. Based on the model simulations of the measured radiation, actinic flux spectra are reconstructed. These are used to calculate various photodissociation rates.

scholarly journals Assessment and Validation of i-Skyradiometer Retrievals Using Broadband Flux and MODIS Data

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
S. Dipu ◽  
G. Pandithurai ◽  
A. S. Panicker ◽  
T. Takamura ◽  
Dong-In Lee ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Climate Models ◽  
Surface Radiation ◽  
Combination Method ◽  
New Combination ◽  
Radiative Transfer Model ◽  
Retrieval Algorithm ◽  
Transfer Model ◽  
Cloud Parameters ◽  
Radiation Measurements

Ground-based network of cloud measurements is presently limited and there exists uncertainty in the cloud microphysical parameters derived from ground-based measurements. Bias in the i-skyradiometer derived cloud optical depth (τc) and droplet effective radius (Reff) and the importance of these parameters in the parameterization of clouds in climate models have made us intend to develop a possible method for improving these parameters. A new combination method, which uses zenith sky transmittance and surface radiation measurements, has been proposed in the present study to improve the retrievals. The i-skyradiometer derived parametersτcandReffhave been provided as a first guess to a radiative transfer model (SBDART) and a new retrieval algorithm has been implemented to obtain the best combination ofτcandReffhaving minimum bias (−0.09 and −2.5) between the simulated global and diffuse fluxes at the surface with the collocated surface radiation measurements. The new retrieval method has improvedτcandReffvalues compared to those derived using the transmittance only method and are in good agreement with the MODIS satellite retrievals. The study therefore suggests a possible improvement of the i-skyradiometer derived cloud parameters using observed radiation fluxes and a radiative transfer model.

scholarly journals Characterization of an EKO MS-711 spectroradiometer: aerosol retrieval from spectral direct irradiance measurements and corrections of the circumsolar radiation

2019 ◽  
Author(s):  
Rosa Delia García-Cabrera ◽  
Emilio Cuevas-Agulló ◽  
África Barreto ◽  
Victoria Eugenia Cachorro ◽  
Mario Pó ◽  
...  
Keyword(s):  
Field Of View ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Aerosol Retrieval ◽  
Aerosol Scattering ◽  
Comparison Results ◽  
The World ◽  
Uv Visible ◽  
Uv Range

Abstract. Spectral direct UV-Visible normal solar irradiance (DNI) measured with an EKO MS-711 spectroradiometer at the Izaña Atmospheric Observatory (IZO, Spain) has been used to determine aerosol optical depth (AOD) at several wavelengths (340, 380, 440, 500, 675 and 870 nm) between April and September 2019 that have been compared with synchronous AOD measurements from a reference Cimel-AERONET (Aerosol RObotic NETwork) sunphotometer. The EKO MS-711 has been calibrated at Izaña Observatory using the Langley-Plot method during the study period. Although this instrument has been designed for spectral solar DNI measurements, and therefore has a field of view (FOV) of 5° that is twice that recommended in solar photometry for AOD determination, the AOD differences compared against the AERONET Cimel reference instrument (FOV ∼ 1.2°), are fairly small. The comparison results between AOD Cimel and EKO MS-711 present a root mean square (RMS) of 0.013 (24.6 %) at 340, and 380 nm, and 0.029 (19.5 %) for longer wavelengths (440, 500, 675 and 870 nm). However, under relatively high AOD, near forward aerosol scattering might be significant because of the relatively large circumsolar radiation (CSR) due to the large EKO MS-711 FOV, resulting in a small but significant AOD underestimation in the UV range. The AOD differences decrease considerably when CSR corrections, estimated from LibRadtran radiative transfer model simulations, are performed, obtaining RMS of 0.006 (14.9 %) at 340 and 380 nm, and 0.005 (11.1 %) for longer wavelengths. The percentage of 2-minute synchronous EKO AOD–Cimel AOD differences within the World Meteorological Organization (WMO) traceability limits were ≥ 96 % at 500 nm, 675 nm and 870 nm with no CSR corrections. After applying the CSR corrections, the percentage of AOD differences within the WMO traceability limits increased to > 95 % for 380, 440, 500, 675 and 870 nm, while for 340 nm the percentage of AOD differences showed a poorer increase from 67 % to a modest 86 %.

scholarly journals Modeling the Reflectance of the Lunar Regolith by a New Method Combining Monte Carlo Ray Tracing and Hapke’s Model with Application to Chang’E-1 IIM Data

2014 ◽  
Vol 2014 ◽  
pp. 1-14
Author(s):  
Un-Hong Wong ◽  
Yunzhao Wu ◽  
Hon-Cheng Wong ◽  
Yanyan Liang ◽  
Zesheng Tang
Keyword(s):  
Monte Carlo ◽  
Ray Tracing ◽  
Large Scale ◽  
Scale Effects ◽  
Lunar Regolith ◽  
Lunar Soil ◽  
New Method ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Composition Of Minerals

In this paper, we model the reflectance of the lunar regolith by a new method combining Monte Carlo ray tracing and Hapke’s model. The existing modeling methods exploit either a radiative transfer model or a geometric optical model. However, the measured data from an Interference Imaging spectrometer (IIM) on an orbiter were affected not only by the composition of minerals but also by the environmental factors. These factors cannot be well addressed by a single model alone. Our method implemented Monte Carlo ray tracing for simulating the large-scale effects such as the reflection of topography of the lunar soil and Hapke’s model for calculating the reflection intensity of the internal scattering effects of particles of the lunar soil. Therefore, both the large-scale and microscale effects are considered in our method, providing a more accurate modeling of the reflectance of the lunar regolith. Simulation results using the Lunar Soil Characterization Consortium (LSCC) data and Chang’E-1 elevation map show that our method is effective and useful. We have also applied our method to Chang’E-1 IIM data for removing the influence of lunar topography to the reflectance of the lunar soil and to generate more realistic visualizations of the lunar surface.

scholarly journals A New Method to Retrieve Thin Cloud Optical Thickness from a Ratio of Scattering to Global Solar Irradiance

2014 ◽  
Vol 71 (4) ◽  
pp. 1521-1528 ◽  
Author(s):  
Jinhuan Qiu ◽  
Xuemei Zong
Keyword(s):  
Optical Thickness ◽  
New Method ◽  
Radiative Transfer Model ◽  
Mean Deviation ◽  
Transfer Model ◽  
Thin Cloud ◽  
Scattering Phase ◽  
Cloud Optical Thickness ◽  
The Difference ◽  
Scattering Phase Function

Abstract Three kinds of “visible” cloud optical thickness τ—matching shortwave direct, global, and scattering solar irradiances (Ids, Igs and Iss)—are defined, which are marked as τd, τg, and τs, respectively. It is found from radiation calculations that a ratio of Iss to Igs in the small-τ case has a unique characteristic: strong sensitivity to τ but weak sensitivity to the cloud scattering phase function. On the basis of this characteristic, a method to retrieve Iss-equivalent τs from the ratio is proposed. This method is validated by way of simulation and application tests, in which the Discrete Ordinate Radiative Transfer model (DISORT) is used to calculate irradiances. As shown in simulations with τ < 2, there may be unrealistically negative or grossly overestimated τ values from Igs, owing to the difference between τs and τd, while the new method can lead to a very good agreement of τs retrieval with its input. Furthermore, this method is used to retrieve small τ from the pyrheliometer and pyranometer measurements in Lhasa during 2006. It is found that τ retrieved from Igs was often negative because of cloud inhomogeneity, while the application of the new method resulted in stable yet reasonable τs values. The Iss calculations using 1293 sets of τs retrievals fit well into the Iss determinations from pyrheliometer and pyranometer measurements with an annual-mean deviation of 0.18%, but the deviation was raised to 46.4% when using τg retrievals.

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