A first intercomparison of JNO2 measurements by actinic flux spectroradiometry (SR) and chemical actinometry (CA) was performed in summer 1997 in Jülich, Germany. During this experiment (JCOM97) a ...large set of data was collected with a time resolution of ∼ 1 min, showing a high linear correlation (R = 0.998) in JNO2. Linear regression indicates a good absolute agreement with the CA being 6% higher than SR if the quantum yield recommended by NASA/JPL (1997) and recently published data of the NO2 absorption spectrum (σNO2) is used for the evaluation of the SR‐data. The influence of using previously published σNO2 data is discussed. Overall the comparison suggests that JNO2 can be measured by either CA or SR with an accuracy of better than 10%.
Ye et al. have determined a maximum nitrous acid (HONO) yield of 3% for the reaction HO2·H2O + NO2, which is much lower than the yield used in our work. This finding, however, does not affect our ...main result that HONO in the investigated Po Valley region is mainly from a gas-phase source that consumes nitrogen oxides.
A first intercomparison of
J
NO
2
measurements by actinic flux spectroradiometry (SR) and chemical actinometry (CA) was performed in summer 1997 in Jülich, Germany. During this experiment (JCOM97) a ...large set of data was collected with a time resolution of ∼ 1 min, showing a high linear correlation (R = 0.998) in
J
NO
2
. Linear regression indicates a good absolute agreement with the CA being 6% higher than SR if the quantum yield recommended by NASA/JPL (1997) and recently published data of the NO
2
absorption spectrum (σ
NO
2
) is used for the evaluation of the SR‐data. The influence of using previously published σ
NO
2
data is discussed. Overall the comparison suggests that
J
NO
2
can be measured by either CA or SR with an accuracy of better than 10%.
A first intercomparison of J sub(N) sub(O) sub(2) measurements by actinic flux spectroradiometry (SR) and chemical actinometry (CA) was performed in summer 1997 in Julich, Germany. During this ...experiment (JCOM97) a large set of data was collected with a time resolution of similar to 1 min, showing a high linear correlation (R = 0.998) in J sub(N) sub(O) sub(2) . Linear regression indicates a good absolute agreement with the CA being 6% higher than SR if the quantum yield recommended by NASA/JPL (1997) and recently published data of the NO sub(2) absorption spectrum ( sigma sub(N) sub(O) sub(2) ) is used for the evaluation of the SR-data. The influence of using previously published sigma sub(N) sub(O) sub(2) data is discussed. Overall the comparison suggests that J sub(N) sub(O) sub(2) can be measured by either CA or SR with an accuracy of better than 10%.
This paper presents the measurements of OH and HO
2
radical concentrations as well as photolysis frequencies of different molecules during the Berliner Ozone (BERLIOZ) field experiment in July/August ...1998 at the rural site Pabstthum about 50 km NW of Berlin. Radical concentrations were measured using laser‐induced fluorescence (LIF) spectroscopy, while filter radiometers and a scanning spectroradiometer were used to obtain photolysis frequencies. The radical data set covers the time period from 20 July to 6 August and consists of more than 6000 simultaneous measurements of OH and HO
2
with a typical time resolution of about 90 s. The maximum OH and HO
2
daytime concentrations were 8 × 10
6
and 8 × 10
8
cm
−3
, respectively. While nighttime values of OH were usually below the detection limit of our instrument (3.5 × 10
5
cm
−3
), HO
2
did show significant concentrations throughout most of the nights (on average 3 × 10
7
cm
−3
). The OH concentration was mainly controlled by solar UV radiation and showed a high linear correlation with J(O
1
D). A deviation from this general behavior was observed around dawn and dusk, when OH concentrations well above the detection limit were observed, although J(O
1
D) was essentially zero. A comparison with data sets from previous campaigns revealed that even though the linear correlation is found in other environments as well the slope OH/J(O
1
D) differs significantly. The diurnal cycles of HO
2
were less dependent on the solar actinic flux but were predominantly influenced by NO. During episodes of high NO, HO
2
remained below the detection limit (1 × 10
7
cm
−3
) but started to rise rapidly as soon as NO started to decrease.
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