scholarly journals Improved modeling of cloudy‐sky actinic flux using satellite cloud retrievals

2017 ◽  
Vol 44 (3) ◽  
pp. 1592-1600 ◽  
Author(s):  
Young‐Hee Ryu ◽  
Alma Hodzic ◽  
Gael Descombes ◽  
Samuel Hall ◽  
Patrick Minnis ◽  
...  
Keyword(s):  
Actinic Flux

scholarly journals Estimation of surface actinic flux from satellite (TOMS) ozone and cloud reflectivity measurements

1998 ◽  
Vol 25 (23) ◽  
pp. 4321-4324 ◽  
Author(s):  
B. Mayer ◽  
C. A. Fischer ◽  
S. Madronich
Keyword(s):  
Actinic Flux

scholarly journals Analysis of actinic flux profiles measured from an ozonesonde balloon

2015 ◽  
Vol 15 (8) ◽  
pp. 4131-4144 ◽  
Author(s):  
P. Wang ◽  
M. Allaart ◽  
W. H. Knap ◽  
P. Stammes
Keyword(s):  
Atmospheric Chemistry ◽  
Low Cost ◽  
Green Light ◽  
Single Layer ◽  
Radiative Transfer Model ◽  
Cloud Base ◽  
Transfer Model ◽  
Actinic Flux ◽  
Clear Sky ◽  
The Impact

Abstract. A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozonesonde balloon. In total, 63 launches with ascending and descending profiles were performed between 2006 and 2010. The measured uncalibrated actinic flux profiles are analysed using the Doubling–Adding KNMI (DAK) radiative transfer model. Values of the cloud optical thickness (COT) along the flight track were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The impact of clouds on the actinic flux profile is evaluated on the basis of the cloud modification factor (CMF) at the cloud top and cloud base, which is the ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact of clouds on the actinic flux is clearly detected: the largest enhancement occurs at the cloud top due to multiple scattering. The actinic flux decreases almost linearly from cloud top to cloud base. Above the cloud top the actinic flux also increases compared to clear-sky scenes. We find that clouds can increase the actinic flux to 2.3 times the clear-sky value at cloud top and decrease it to about 0.05 at cloud base. The relationship between CMF and COT agrees well with DAK simulations, except for a few outliers. Good agreement is found between the DAK-simulated actinic flux profiles and the observations for single-layer clouds in fully overcast scenes. The instrument is suitable for operational balloon measurements because of its simplicity and low cost. It is worth further developing the instrument and launching it together with atmospheric chemistry composition sensors.

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.

scholarly journals The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA

2016 ◽  
Vol 16 (21) ◽  
pp. 13837-13851 ◽  
Author(s):  
Maria Zatko ◽  
Joseph Erbland ◽  
Joel Savarino ◽  
Lei Geng ◽  
Lauren Easley ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Oil And Gas ◽  
Nitrogen Isotopes ◽  
Ground Level ◽  
Anthropogenic Sources ◽  
Reactive Nitrogen ◽  
Actinic Flux ◽  
Nitrogen Fluxes ◽  
Uintah Basin

Abstract. Reactive nitrogen (Nr  =  NO, NO2, HONO) and volatile organic carbon emissions from oil and gas extraction activities play a major role in wintertime ground-level ozone exceedance events of up to 140 ppb in the Uintah Basin in eastern Utah. Such events occur only when the ground is snow covered, due to the impacts of snow on the stability and depth of the boundary layer and ultraviolet actinic flux at the surface. Recycling of reactive nitrogen from the photolysis of snow nitrate has been observed in polar and mid-latitude snow, but snow-sourced reactive nitrogen fluxes in mid-latitude regions have not yet been quantified in the field. Here we present vertical profiles of snow nitrate concentration and nitrogen isotopes (δ15N) collected during the Uintah Basin Winter Ozone Study 2014 (UBWOS 2014), along with observations of insoluble light-absorbing impurities, radiation equivalent mean ice grain radii, and snow density that determine snow optical properties. We use the snow optical properties and nitrate concentrations to calculate ultraviolet actinic flux in snow and the production of Nr from the photolysis of snow nitrate. The observed δ15N(NO3−) is used to constrain modeled fractional loss of snow nitrate in a snow chemistry column model, and thus the source of Nr to the overlying boundary layer. Snow-surface δ15N(NO3−) measurements range from −5 to 10 ‰ and suggest that the local nitrate burden in the Uintah Basin is dominated by primary emissions from anthropogenic sources, except during fresh snowfall events, where remote NOx sources from beyond the basin are dominant. Modeled daily averaged snow-sourced Nr fluxes range from 5.6 to 71  ×  107 molec cm−2 s−1 over the course of the field campaign, with a maximum noontime value of 3.1  ×  109 molec cm−2 s−1. The top-down emission estimate of primary, anthropogenic NOx in Uintah and Duchesne counties is at least 300 times higher than the estimated snow NOx emissions presented in this study. Our results suggest that snow-sourced reactive nitrogen fluxes are minor contributors to the Nr boundary layer budget in the highly polluted Uintah Basin boundary layer during winter 2014.

scholarly journals The magnitude of the snow-sourced reactive nitrogen flux to the boundary layer in the Uintah Basin, Utah, USA

2016 ◽  
Author(s):  
Maria Zatko ◽  
Joseph Erbland ◽  
Joel Savarino ◽  
Lei Geng ◽  
Lauren Easley ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Oil And Gas ◽  
Nitrogen Isotopes ◽  
Ground Level ◽  
Anthropogenic Sources ◽  
Reactive Nitrogen ◽  
Actinic Flux ◽  
Nitrogen Fluxes ◽  
Uintah Basin

Abstract. Reactive nitrogen (Nr = NO, NO2, HONO) and volatile organic carbon emissions from oil and gas extraction activities play a major role in wintertime ground-level ozone exceedance events of up to 140 ppb in the Uintah Basin in eastern Utah. Such events occur only when the ground is snow covered, due to the impacts of snow on the stability and depth of the boundary layer and ultraviolet actinic flux at the surface. Recycling of reactive nitrogen from the photolysis of snow nitrate has been observed in polar and mid-latitude snow, but snow-sourced reactive nitrogen fluxes in mid-latitude regions have not yet been quantified in the field. Here we present vertical profiles of snow nitrate concentration and nitrogen isotopes (δ15N) collected during the Uintah Basin Winter Ozone Study 2014 (UBWOS 2014), along with observations of insoluble light-absorbing impurities, radiation equivalent mean ice grain radii, and snow density that determine snow optical properties. We use the snow optical properties and nitrate concentrations to calculate ultraviolet actinic flux in snow and the production of Nr from the photolysis of snow nitrate. The observed δ15N(NO3−) is used to constrain modeled fractional loss of snow nitrate in a snow chemistry column model, and thus the source of snow-sourced Nr to the overlying boundary layer. Snow-surface δ15N(NO3−) measurements range from −5 ‰ to 10 ‰ and suggest that the local nitrate burden in the Uintah Basin is dominated by primary emissions from anthropogenic sources, except during fresh snowfall events, where remote NOx sources from beyond the basin are dominant. Modeled daily-averaged snow-sourced Nr fluxes range from 5.6−71 × 107 molec cm−2 s−1 over the course of the field campaign, with a maximum noon-time value of 3.1 × 109 molec cm−2 s−1. The top-down emission estimate of primary, anthropogenic NOx in the Uintah and Duchesne counties is at least 300 times higher than the estimated snow NOx emissions presented in this study. Our results suggest that snow-sourced reactive nitrogen fluxes are minor contributors to the Nr boundary layer budget in the highly-polluted Uintah Basin boundary layer during winter 2014.

scholarly journals Investigation of the 3-D actinic flux field in mountainous terrain

2011 ◽  
Vol 102 (3) ◽  
pp. 300-310 ◽  
Author(s):  
J.E. Wagner ◽  
F. Angelini ◽  
M. Blumthaler ◽  
M. Fitzka ◽  
G.P. Gobbi ◽  
...  
Keyword(s):  
Mountainous Terrain ◽  
Actinic Flux
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