scholarly journals Comparison of airborne measured and calculated spectral actinic flux and derived photolysis frequencies during the PEM Tropics B mission

2002 ◽  
Vol 108 (D2) ◽  
Author(s):  
R. E. Shetter ◽  
L. Cinquini ◽  
B. L. Lefer ◽  
S. R. Hall ◽  
S. Madronich
Keyword(s):  
Actinic Flux ◽  
Photolysis Frequencies

scholarly journals Estimation of photolysis frequencies from TOMS satellite measurements and routine meteorological observations

2008 ◽  
Vol 26 (7) ◽  
pp. 1965-1975
Author(s):  
C. Topaloglou ◽  
B. Mayer ◽  
S. Kazadzis ◽  
A. F. Bais ◽  
M. Blumthaler
Keyword(s):  
Empirical Method ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Satellite Measurements ◽  
Absolute Level ◽  
Actinic Flux ◽  
Photolysis Frequencies ◽  
Flux Measurements ◽  
Meteorological Observations ◽  
Level Of Agreement

Abstract. A study on the estimation of J(O1D) and J(NO2) photolysis frequencies when limited ground based measurements (or even no measurements at all), are available is presented in this work. Photolysis frequencies can be directly measured by chemical actinometry and filter radiometry or can be calculated from actinic flux measurements. In several meteorological stations, none of the methods above are applicable due to the absence of sophisticated instruments such as actinometers, radiometers or spectroradiometers. In this case, it is possible to calculate photolysis frequencies with reasonable uncertainty using either a) standard meteorological observations, such as ozone, cloud coverage and horizontal visibility, available in various ground based stations, as input for a radiative transfer model or b) satellite observations of solar global irradiance available worldwide, in combination with an empirical method for the conversion of irradiance in photolysis frequencies. Both methods can provide photolysis frequencies with a standard deviation between 20% and 30%. The absolute level of agreement of the retrieved frequencies to those calculated from actual actinic flux measurements, for data from all meteorological conditions, is within ±5% for J(O1D) and less than 1% for J(NO2) for the first method, while for the second method it rises up to 25% for the case of J(O1D) and 12% for J(NO2), reflecting the overestimation of TOMS satellite irradiance when compared to ground based measurements of irradiance for the respective spectral regions. Due to the universality of the methods they can be practically applied to almost any station, thus overcoming problems concerning the availability of instruments measuring photolysis frequencies.

Spectrally resolved actinic flux and photolysis frequencies of key species within an indoor environment

2016 ◽  
Vol 109 ◽  
pp. 50-57 ◽  
Author(s):  
Adrien Gandolfo ◽  
Vladimir Gligorovski ◽  
Vincent Bartolomei ◽  
Sabrine Tlili ◽  
Elena Gómez Alvarez ◽  
...  
Keyword(s):  
Indoor Environment ◽  
Actinic Flux ◽  
Photolysis Frequencies ◽  
Key Species ◽  
Spectrally Resolved

scholarly journals The impact of aerosols on photolysis frequencies and ozone production in urban Beijing during the four-year period 2012–2015

2019 ◽  
Author(s):  
Wenjie Wang ◽  
Min Shao ◽  
Min Hu ◽  
Limin Zeng ◽  
Yusheng Wu
Keyword(s):  
Production Rate ◽  
Ozone Production ◽  
Atmospheric Environment ◽  
Light Extinction ◽  
Parametric Equation ◽  
Actinic Flux ◽  
Photolysis Frequencies ◽  
Depth Analysis ◽  
The Mediterranean ◽  
The Impact

Abstract. During the period 2012–2015, the photolysis frequencies were measured at the Peking University site (PKUERS), a representative site of urban Beijing. We present a study of the effects of aerosols on two key photolysis frequencies, j(O1D) and j(NO2). Both j(O1D) and j(NO2) display significant dependence on AOD with a nonlinear negative correlation. With the increase in AOD, the slopes of photolysis frequencies vs AOD decrease, which indicates that the capacity of aerosols to reduce the actinic flux decreases with AOD. In addition, the slopes are equal to 4.21–6.93 × 10−6 s−1 and 3.20 × 10−3 s−1 per AOD unit for j(O1D) and j(NO2) respectively at SZA of 60°, both of which are larger than those observed in the Mediterranean. This indicates that the aerosols in urban Beijing have a stronger extinction on actinic flux than absorptive dust aerosols in the Mediterranean. Since the photolysis frequencies strongly depended on the AOD and the solar zenith angle (SZA), we established a parametric equation to quantitatively evaluate the effect of aerosols on photolysis frequencies in Beijing. According to the parametric equation, aerosols lead to a decrease in j(NO2) by 24.2 % and 30.4 % for summer and winter, respectively, and the corresponding decrease in j(O1D) by 27.3 % and 32.6 % respectively, compared to an aerosol-free atmosphere. Based on an observation campaign in August 2012, we used the photochemical box model to simulate the ozone production rate (P(O3)). The simulation results shows that the monthly average net ozone production rate is reduced by up to 25 % due to the light extinction of aerosols. Through further in-depth analysis, it was found that particulate matter concentrations maintain high level under the condition of high concentrations of ozone precursors (VOCs and NOx), which inhibits the production of ozone to a large extent. This phenomenon implies a negative feedback mechanism in the atmospheric environment of urban Beijing.

scholarly journals NO<sub>2</sub> and HCHO photolysis frequencies from irradiance measurements in Thessaloniki, Greece

2005 ◽  
Vol 5 (6) ◽  
pp. 1645-1653 ◽  
Author(s):  
C. Topaloglou ◽  
S. Kazadzis ◽  
A. F. Bais ◽  
M. Blumthaler ◽  
B. Schallhart ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Nitrogen Dioxide ◽  
Atmospheric Conditions ◽  
Actinic Flux ◽  
Lower Upper ◽  
Global Irradiance ◽  
Photolysis Frequencies ◽  
Photolysis Frequency ◽  
Flux Measurements

Abstract. An empirical approach for the retrieval of nitrogen dioxide (NO2) and formaldehyde (HCHO) photolysis frequencies from measurements of global irradiance is presented in this work. Four months of synchronous measurements of actinic flux and global irradiance performed in Thessaloniki, Greece by a Bentham spectroradiometer were used to extract polynomials for the conversion of global irradiance to photolysis frequencies [J(NO2) and J(HCHO)]. The comparison of these photolysis frequency values to the corresponding values calculated by spectral actinic flux measurements, showed a ratio very close to unity for all J's with a standard deviation of 12% (2σ) for J(NO2) and 6% (2σ) for J(HCHO). Additional sets of polynomials were also extracted to allow determination of J(NO2) by spectroradiometers with lower upper wavelength limits such as single and double Brewer spectroradiometers within acceptable uncertainty (corresponding ratio was 1 and standard deviation was 12% (2σ) for the method that can be used with double Brewers and 20% for the method that can be used for single Brewers). The validity of the method under different atmospheric conditions was also examined by applying the polynomials to another set of actinic flux and global irradiance measurements performed in May 2004, in Buchhofen, Germany. In this case, comparing J values extracted from the polynomials to those calculated from actinic flux, showed equivalent results, demonstrating that the method can also be applied to other measurement sites.

scholarly journals The impact of aerosols on photolysis frequencies and ozone production in Beijing during the 4-year period 2012–2015

2019 ◽  
Vol 19 (14) ◽  
pp. 9413-9429 ◽  
Author(s):  
Wenjie Wang ◽  
Xin Li ◽  
Min Shao ◽  
Min Hu ◽  
Limin Zeng ◽  
...  
Keyword(s):  
Production Rate ◽  
Ozone Production ◽  
Atmospheric Environment ◽  
Light Extinction ◽  
Parametric Equation ◽  
Actinic Flux ◽  
Photolysis Frequencies ◽  
Depth Analysis ◽  
The Mediterranean ◽  
The Impact

Abstract. During the period 2012–2015, photolysis frequencies were measured at the Peking University site (PKUERS), a site representative of Beijing. We present a study of the effects of aerosols on two key photolysis frequencies, j(O1D) and j(NO2). Both j(O1D) and j(NO2) display significant dependence on aerosol optical depth (AOD; 380 nm) with a non-linear negative correlation. With the increase in AOD, the slopes of photolysis frequencies vs. AOD decrease, which indicates that the capacity of aerosols to reduce the actinic flux decreases with AOD. The absolute values of slopes are equal to 4.2–6.9×10-6 and 3.4×10-3 s−1 per AOD unit for j(O1D) and j(NO2) respectively at a solar zenith angle (SZA) of 60∘ and AOD smaller than 0.7, both of which are larger than those observed in a similar, previous study in the Mediterranean. This indicates that the aerosols in Beijing have a stronger extinction effect on actinic flux than absorptive dust aerosols in the Mediterranean. Since the photolysis frequencies strongly depended on the AOD and the SZA, we established a parametric equation to quantitatively evaluate the effect of aerosols on photolysis frequencies in Beijing. According to the parametric equation, aerosols lead to a decrease in seasonal mean j(NO2) by 24 % and 30 % for summer and winter, respectively, and a corresponding decrease in seasonal mean j(O1D) by 27 % and 33 %, respectively, compared to an aerosol-free atmosphere (AOD =0). Based on an observation campaign in August 2012, we used a photochemical box model to simulate the ozone production rate (P(O3)). The simulation results shows that the monthly mean daytime net ozone production rate is reduced by up to 25 % due to the light extinction of aerosols. Through further in-depth analysis, it was found that particulate matter concentrations maintain a high level under the condition of high concentrations of ozone precursors (volatile organic compounds, VOCs, and NOx), which inhibits the production of ozone to a large extent. This phenomenon implies a negative feedback mechanism in the atmospheric environment of Beijing.

scholarly journals A new actinic flux 4π-spectroradiometer: Instrument design and application to clear sky and broken cloud conditions

2002 ◽  
Vol 2 (6) ◽  
pp. 1939-1977 ◽  
Author(s):  
E. Eckstein ◽  
D. Perner ◽  
Ch. Brühl ◽  
T. Trautmann
Keyword(s):  
Atmospheric Chemistry ◽  
Liquid Water Content ◽  
Angle Of Incidence ◽  
Actinic Flux ◽  
Clear Sky ◽  
Photolysis Frequencies ◽  
New Instrument ◽  
Measured Liquid ◽  
Imaging Spectrograph ◽  
Good Agreement

Abstract. A new 4p-spectroradiometer was developed for measuring actinic flux especially under cloudy conditions based on a fixed grating imaging spectrograph and a CCD-detector leading to a simultaneous measurement of the spectrum. The new instrument incorporates a novel optical head with a 4p-field of view independent of angle of incidence. Comparisons with the actinic flux spectroradiometer of the Institute of Atmospheric Chemistry of Forschungszentrum Jülich showed a very good agreement within the limit of the uncertainties of the two instruments. Our spectroradiometer was applied to investigate the effects of broken clouds on the actinic flux and photolysis frequencies on the ground during the BERLIOZ campaign. Reductions as well as enhancements compared to the clear sky case were seen, both effects are larger in the UV-A than the UV-B spectral region. Furthermore the new instrument was used for simultaneous measurements in different altitudes on a tower to study the transmission and attenuation of actinic flux in low clouds. A correlation of attenuation with the simultaneously measured liquid water content of the cloud was found.

scholarly journals Calibration and evaluation of CCD spectroradiometers for ground-based and airborne measurements of spectral actinic flux densities

2017 ◽  
Vol 10 (9) ◽  
pp. 3151-3174 ◽  
Author(s):  
Birger Bohn ◽  
Insa Lohse
Keyword(s):  
Field Data ◽  
Detection Limits ◽  
Spectral Irradiance ◽  
Stray Light ◽  
Integration Time ◽  
Actinic Flux ◽  
Airborne Measurements ◽  
Dark Noise ◽  
Photolysis Frequencies ◽  
Double Monochromator

Abstract. The properties and performance of charge-coupled device (CCD) array spectroradiometers for the measurement of atmospheric spectral actinic flux densities (280–650 nm) and photolysis frequencies were investigated. These instruments are widely used in atmospheric research and are suitable for aircraft applications because of high time resolutions and high sensitivities in the UV range. The laboratory characterization included instrument-specific properties like the wavelength accuracy, dark signal, dark noise and signal-to-noise ratio (SNR). Spectral sensitivities were derived from measurements with spectral irradiance standards. The calibration procedure is described in detail, and a straightforward method to minimize the influence of stray light on spectral sensitivities is introduced. From instrument dark noise, minimum detection limits  ≈  1  ×  1010 cm−2 s−1 nm−1 were derived for spectral actinic flux densities at wavelengths around 300 nm (1 s integration time). As a prerequisite for the determination of stray light under field conditions, atmospheric cutoff wavelengths were defined using radiative transfer calculations as a function of the solar zenith angle (SZA) and total ozone column (TOC). The recommended analysis of field data relies on these cutoff wavelengths and is also described in detail taking data from a research flight on HALO (High Altitude and Long Range Research Aircraft) as an example. An evaluation of field data was performed by ground-based comparisons with a double-monochromator-based, highly sensitive reference spectroradiometer. Spectral actinic flux densities were compared as well as photolysis frequencies j(NO2) and j(O1D), representing UV-A and UV-B ranges, respectively. The spectra expectedly revealed increased daytime levels of stray-light-induced signals and noise below atmospheric cutoff wavelengths. The influence of instrument noise and stray-light-induced noise was found to be insignificant for j(NO2) and rather limited for j(O1D), resulting in estimated detection limits of 5  ×  10−7 and 1  ×  10−7 s−1, respectively, derived from nighttime measurements on the ground (0.3 s integration time, 10 s averages). For j(O1D) the detection limit could be further reduced by setting spectral actinic flux densities to zero below atmospheric cutoff wavelengths. The accuracies of photolysis frequencies were determined from linear regressions with data from the double-monochromator reference instrument. The agreement was typically within ±5 %. Because optical-receiver aspects are not specific for the CCD spectroradiometers, they were widely excluded in this work and will be treated in a separate paper, in particular with regard to airborne applications.

scholarly journals Actinic flux and O<sup>1</sup>D photolysis frequencies retrieved from spectral measurements of irradiance at Thessaloniki, Greece

2004 ◽  
Vol 4 (8) ◽  
pp. 2215-2226 ◽  
Author(s):  
S. Kazadzis ◽  
C. Topaloglou ◽  
A. F. Bais ◽  
M. Blumthaler ◽  
D. Balis ◽  
...  
Keyword(s):  
Empirical Method ◽  
Data Sets ◽  
Spectral Measurements ◽  
Model Uncertainties ◽  
Actinic Flux ◽  
Global Irradiance ◽  
Photolysis Frequencies ◽  
Process Studies ◽  
Spectrometer Data ◽  
Method Show

Abstract. The results of two methods retrieving actinic flux and ozone photolysis frequencies (JO1D), from measurements of irradiance with a Brewer MKIII spectroradiometer are investigated in this paper. The first method uses actinic flux retrieved from irradiance measurements by the use of known formulas while the second is an empirical method converting irradiance to JO1D through polynomials extracted from a study of synchronous actinic flux and irradiance measurements. When examining the actinic fluxes derived from the first method to those measured by an actinic flux spectrometer data agree within ±10% for solar zenith angles lower than 75° for the UV-B and the UV-A wavelength band. Also, the actinic to global irradiance ratio derived, deviates within ±6% for solar zenith angles lower than 70° compared with cloudless sky calculations of the TUV model. For both cases the deviations are in the order of the magnitude of the measurement or model uncertainties. Values of JO1D calculated by the second method show a mean ratio of 0.99±0.10 (1σ) and 0.98±0.06 for all data and for cloudless skies respectively when compared with values of JO1D derived by a Bentham actinic flux spectroradiometer. Finally, the agreement of the two methods is within ±5% comparing two years' data of JO1D retrieved from irradiance measurements at Thessaloniki, Greece. The use of such methods on extensive data sets of global irradiance can provide JO1D values with acceptable uncertainty, a parameter of particular importance for chemical process studies.

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