Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw

Atmospheric Chemistry and Physics (ACP), Vol. 11. N° 3. Zieger P.; Weingartner E.; Henzing J.; et al. - Copernicus GmbH, 2011

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30–40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties – especially the aerosol light scattering – are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol ...

English

[article] 

Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw

  Available online: http://dx.doi.org/10.5194/acp-11-2603-2011

P. Zieger ; E. Weingartner ; J. Henzing ; M. Moerman ; G. de Leeuw ; J. Mikkilä ; M. Ehn ; T. Petäjä ; K. Clémer ; M. van Roozendael ; S. Yilmaz ; U. Frieß ; H. Irie ; T. Wagner ; R. Shaiganfar ; S. Beirle ; A. Apituley ; K. Wilson ; U. Baltensperger

in Atmospheric Chemistry and Physics (ACP) > Vol. 11. N° 3 [03/01/2011] . - p.2603-2624

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30–40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties – especially the aerosol light scattering – are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol scattering coefficient σsp(λ) was measured dry and at various, predefined RH conditions between 20 and 95% with a humidified nephelometer. The scattering enhancement factor f(RH,λ) is the key parameter to describe the effect of RH on σsp(λ) and is defined as σsp(RH,λ) measured at a certain RH divided by the dry σsp(dry,λ). The measurement of f(RH,λ) together with the dry absorption measurement (assumed not to change with RH) allows the determination of the actual extinction coefficient σep(RH,λ) at ambient RH. In addition, a wide range of other aerosol properties were measured in parallel. The measurements were used to characterize the effects of RH on the aerosol optical properties. A closure study showed the consistency of the aerosol in-situ measurements. Due to the large variability of air mass origin (and thus aerosol composition) a simple parameterization of f(RH,λ) could not be established. If f(RH,λ) needs to be predicted, the chemical composition and size distribution need to be known. Measurements of four MAX-DOAS (multi-axis differential optical absorption spectroscopy) instruments were used to retrieve vertical profiles of σep(λ). The values of the lowest layer were compared to the in-situ values after conversion of the latter ones to ambient RH. The comparison showed a good correlation of R2 = 0.62–0.78, but the extinction coefficients from MAX-DOAS were a factor of 1.5–3.4 larger than the in-situ values. Best agreement is achieved for a few cases characterized by low aerosol optical depths and low planetary boundary layer heights. Differences were shown to be dependent on the applied MAX-DOAS retrieval algorithm. The comparison of the in-situ extinction data to a Raman LIDAR (light detection and ranging) showed a good correlation and higher values measured by the LIDAR (R2 = 0.82−0.85, slope of 1.69–1.76) if the Raman retrieved profile was used to extrapolate the directly measured extinction coefficient to the ground. The comparison improved if only nighttime measurements were used in the comparison (R2 = 0.96, slope of 1.12).

Language(s): English

Format: Digital (Free)

Tags: Aerosols ; Atmosphere ; Air pollution Add tag

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SO2 and BrO observation in the plume of the Eyjafjallajökull volcano 2010: CARIBIC and GOME-2 retrievals

Atmospheric Chemistry and Physics (ACP), Vol. 11. N° 3. Heue K.-P.; Brenninkmeijer C.A.M.; Baker A.K.; et al. - Copernicus GmbH, 2011

The ash cloud of the Eyjafjallajökull (also referred to as: Eyjafjalla (e.g. Schumann et al., 2011), Eyjafjöll or Eyjafjoll (e.g. Ansmann et al., 2010)) volcano on Iceland caused closure of large parts of European airspace in April and May 2010. For the validation and improvement of the European volcanic ash forecast models several research flights were performed. Also the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flying laboratory, which routinely measures at cruise altitude (≈11 km) performed three dedicated measurements flights ...

English

[article] 

SO2 and BrO observation in the plume of the Eyjafjallajökull volcano 2010: CARIBIC and GOME-2 retrievals

  Available online: http://dx.doi.org/10.5194/acp-11-2973-2011

K.-P. Heue ; C.A.M. Brenninkmeijer ; A.K. Baker ; A. Rauthe-Schöch ; D. Walter ; T. Wagner ; C. Hörmann ; H. Sihler ; B. Dix ; U. Frieß ; U. Platt ; B.G. Martinsson ; P.F.J. van Velthoven ; A. Zahn ; R. Ebinghaus

in Atmospheric Chemistry and Physics (ACP) > Vol. 11. N° 3 [03/01/2011] . - p.2973-2989

The ash cloud of the Eyjafjallajökull (also referred to as: Eyjafjalla (e.g. Schumann et al., 2011), Eyjafjöll or Eyjafjoll (e.g. Ansmann et al., 2010)) volcano on Iceland caused closure of large parts of European airspace in April and May 2010. For the validation and improvement of the European volcanic ash forecast models several research flights were performed. Also the CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) flying laboratory, which routinely measures at cruise altitude (≈11 km) performed three dedicated measurements flights through sections of the ash plume. Although the focus of these flights was on the detection and quantification of the volcanic ash, we report here on sulphur dioxide (SO2) and bromine monoxide (BrO) measurements with the CARIBIC DOAS (Differential Optical Absorption Spectroscopy) instrument during the second of these special flights on 16 May 2010. As the BrO and the SO2 observations coincide, we assume the BrO to have been formed inside the volcanic plume. Average SO2 and BrO mixing ratios of ≈40 ppb and ≈5 ppt respectively are retrieved inside the plume. The BrO to SO2 ratio retrieved from the CARIBIC observation is ≈1.3×10−4. Both SO2 and BrO observations agree well with simultaneous satellite (GOME-2) observations. SO2 column densities retrieved from satellite observations are often used as an indicator for volcanic ash. As the CARIBIC O4 column densities changed rapidly during the plume observation, we conclude that the aerosol and the SO2 plume are collocated. For SO2 some additional information on the local distribution can be derived from a comparison of forward and back scan GOME-2 data. More details on the local plume size and position are retrieved by combining CARIBIC and GOME-2 data.

Language(s): English

Format: Digital (Free)

Tags: Aviation ; Airborne ash ; Volcanic Eruption ; Natural hazards ; Iceland Add tag

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Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw

Atmospheric Chemistry and Physics (ACP), Vol. 11. N° 3. Zieger P.; Weingartner E.; Henzing J.; et al. - Copernicus GmbH, 2011

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30–40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties – especially the aerosol light scattering – are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol ...

English

[article] 

Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw

  Available online: http://dx.doi.org/10.5194/acp-11-2603-2011

P. Zieger ; E. Weingartner ; J. Henzing ; M. Moerman ; G. de Leeuw ; J. Mikkilä ; M. Ehn ; T. Petäjä ; K. Clémer ; M. van Roozendael ; S. Yilmaz ; U. Frieß ; H. Irie ; T. Wagner ; R. Shaiganfar ; S. Beirle ; A. Apituley ; K. Wilson ; U. Baltensperger

in Atmospheric Chemistry and Physics (ACP) > Vol. 11. N° 3 [03/01/2011] . - p.2603-2624

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30–40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties – especially the aerosol light scattering – are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol scattering coefficient σsp(λ) was measured dry and at various, predefined RH conditions between 20 and 95% with a humidified nephelometer. The scattering enhancement factor f(RH,λ) is the key parameter to describe the effect of RH on σsp(λ) and is defined as σsp(RH,λ) measured at a certain RH divided by the dry σsp(dry,λ). The measurement of f(RH,λ) together with the dry absorption measurement (assumed not to change with RH) allows the determination of the actual extinction coefficient σep(RH,λ) at ambient RH. In addition, a wide range of other aerosol properties were measured in parallel. The measurements were used to characterize the effects of RH on the aerosol optical properties. A closure study showed the consistency of the aerosol in-situ measurements. Due to the large variability of air mass origin (and thus aerosol composition) a simple parameterization of f(RH,λ) could not be established. If f(RH,λ) needs to be predicted, the chemical composition and size distribution need to be known. Measurements of four MAX-DOAS (multi-axis differential optical absorption spectroscopy) instruments were used to retrieve vertical profiles of σep(λ). The values of the lowest layer were compared to the in-situ values after conversion of the latter ones to ambient RH. The comparison showed a good correlation of R2 = 0.62–0.78, but the extinction coefficients from MAX-DOAS were a factor of 1.5–3.4 larger than the in-situ values. Best agreement is achieved for a few cases characterized by low aerosol optical depths and low planetary boundary layer heights. Differences were shown to be dependent on the applied MAX-DOAS retrieval algorithm. The comparison of the in-situ extinction data to a Raman LIDAR (light detection and ranging) showed a good correlation and higher values measured by the LIDAR (R2 = 0.82−0.85, slope of 1.69–1.76) if the Raman retrieved profile was used to extrapolate the directly measured extinction coefficient to the ground. The comparison improved if only nighttime measurements were used in the comparison (R2 = 0.96, slope of 1.12).

Language(s): English

Format: Digital (Free)

Tags: Aerosols ; Atmosphere ; Air pollution Add tag

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