Characterisation of a stratospheric sulfate plume from the Nabro volcano  using a combination of passive satellite measurements in nadir and limb geometry

Abstract. The eruption of the Nabro volcano (Eritrea), which started on 12 June 2011, caused the introduction of large quantities of SO2 into the lower stratosphere. The subsequently formed sulfate aerosols could be detected for several months following the eruption. It is generally assumed that the formation of sulfate aerosols in the stratosphere is a relatively slow process, but in plumes from explosive eruptions significant amounts of aerosols have been seen to form within a few hours. We show that sulfate aerosols were present in the lower stratosphere within hours of the onset of the eruption of Nabro. Evidence comes from nadir UV Aerosol Index (UVAI) and SO2 measurements by SCIAMACHY, GOME-2 and OMI, and limb aerosol measurements by SCIAMACHY. The sulfate plume displays negative UVAI in the western part of OMI's swath and positive UVAI in the eastern part – an effect that is due to the strong viewing angle dependence of UVAI and can only be caused by a high-altitude (>11 km), non-absorbing (single-scattering albedo >0.97) aerosol plume. For the retrieval of the aerosol profile from limb measurements, the horizontal dimensions and the position of the aerosol plume need to be taken into account, otherwise both extinction and layer height may be underestimated appreciably. By combining nadir SO2 column density and UVAI with limb aerosol profiles, a stratospheric plume from Nabro could be tracked from 13 to 17 June, before the plumes from later, lower-altitude explosions started interfering with the signal. Our findings are in agreement with ground-based lidar and sun-photometer data from an MPLNET/AERONET station in Israel and with data from the satellite-borne CALIOP lidar.

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Characterisation of a stratospheric sulphate plume from the Nabro volcano using a combination of passive satellite measurements in nadir and limb geometry

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-7739-2014 ◽

2014 ◽

Vol 14 (6) ◽

pp. 7739-7775

Author(s):

M. J. M. Penning de Vries ◽

S. Dörner ◽

J. Puķīte ◽

C. Hörmann ◽

M. D. Fromm ◽

...

Keyword(s):

Lower Stratosphere ◽

Single Scattering ◽

Viewing Angle ◽

Satellite Measurements ◽

Lower Altitude ◽

Angle Dependence ◽

Sulphate Aerosols ◽

Ground Based Lidar ◽

Aerosol Index ◽

Aerosol Plume

Abstract. The eruption of the Nabro volcano (Eritrea), which started on 12 June 2011, caused the introduction of large quantities of SO2 into the lower stratosphere. The subsequently formed sulphate aerosols could be detected for several months following the eruption. It is generally assumed that the formation of sulphate aerosols in the stratosphere takes about a month, but in plumes from explosive eruptions significant amounts of aerosols have been seen to form within a few hours. We show that sulphate aerosols were present in the lower stratosphere within hours of the onset of the eruption of Nabro. Evidence comes from nadir UV Aerosol Index (UVAI) and SO2 measurements by SCIAMACHY, GOME-2 and OMI, and limb aerosol measurements by SCIAMACHY. The sulphate plume displays negative UVAI in the western part of OMI's swath and positive UVAI in the eastern part – an effect that is due to the strong viewing angle dependence of UVAI and can only be caused by a high-altitude (>11 km), non-absorbing (single-scattering albedo >0.97) aerosol plume. For the retrieval of the aerosol profile from limb measurements, the horizontal dimensions and the position of the aerosol plume need to be taken into account, otherwise both extinction and layer height may be underestimated appreciably. By combining nadir SO2 column density and UVAI with limb aerosol profiles, a stratospheric plume from Nabro could be tracked from 13 to 17 June, before the plumes from later, lower-altitude explosions started interfering with the signal. Our findings are in agreement with ground-based lidar and sun-photometer data from an MPLNET/AERONET station in Israel and with data from the satellite-borne CALIOP lidar.

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Top-emission organic light emitting diodes with lower viewing angle dependence

Synthetic Metals ◽

10.1016/j.synthmet.2013.12.020 ◽

2014 ◽

Vol 189 ◽

pp. 57-62 ◽

Cited By ~ 11

Author(s):

Byung Wan Lim ◽

Hyeon Soo Jeon ◽

Min Chul Suh

Keyword(s):

Light Emitting Diodes ◽

Organic Light Emitting Diodes ◽

Viewing Angle ◽

Light Emitting ◽

Angle Dependence ◽

Organic Light

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The high Arctic in extreme winters: vortex, temperature, and MLS and ACE-FTS trace gas evolution

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-505-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 505-522 ◽

Cited By ~ 62

Author(s):

G. L. Manney ◽

W. H. Daffer ◽

K. B. Strawbridge ◽

K. A. Walker ◽

C. D. Boone ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Lower Stratosphere ◽

High Arctic ◽

Trace Gas ◽

Satellite Measurements ◽

Broadband Emission ◽

Gas Measurements ◽

Chemistry Experiment ◽

Very High ◽

Good Agreement

Abstract. The first three Arctic winters of the ACE mission represented two extremes of winter variability: Stratospheric sudden warmings (SSWs) in 2004 and 2006 were among the strongest, most prolonged on record; 2005 was a record cold winter. Canadian Arctic Atmospheric Chemistry Experiment (ACE) Validation Campaigns were conducted at Eureka (80° N, 86° W) during each of these winters. New satellite measurements from ACE-Fourier Transform Spectrometer (ACE-FTS), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), and Aura Microwave Limb Sounder (MLS), along with meteorological analyses and Eureka lidar temperatures, are used to detail the meteorology in these winters, to demonstrate its influence on transport, and to provide a context for interpretation of ACE-FTS and validation campaign observations. During the 2004 and 2006 SSWs, the vortex broke down throughout the stratosphere, reformed quickly in the upper stratosphere, and remained weak in the middle and lower stratosphere. The stratopause reformed at very high altitude, near 75 km. ACE measurements covered both vortex and extra-vortex conditions in each winter, except in late-February through mid-March 2004 and 2006, when the strong, pole-centered vortex that reformed after the SSWs resulted in ACE sampling only inside the vortex in the middle through upper stratosphere. The 2004 and 2006 Eureka campaigns were during the recovery from the SSWs, with the redeveloping vortex over Eureka. 2005 was the coldest winter on record in the lower stratosphere, but with an early final warming in mid-March. The vortex was over Eureka at the start of the 2005 campaign, but moved away as it broke up. Disparate temperature profile structure and vortex evolution resulted in much lower (higher) temperatures in the upper (lower) stratosphere in 2004 and 2006 than in 2005. Satellite temperatures agree well with lidar data up to 50–60 km, and ACE-FTS, MLS and SABER show good agreement in high-latitude temperatures throughout the winters. Consistent with a strong, cold upper stratospheric vortex and enhanced radiative cooling after the SSWs, MLS and ACE-FTS trace gas measurements show strongly enhanced descent in the upper stratospheric vortex in late January through March 2006 compared to that in 2005.

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A Large Annual Cycle in Ozone above the Tropical Tropopause Linked to the Brewer–Dobson Circulation

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2409.1 ◽

2007 ◽

Vol 64 (12) ◽

pp. 4479-4488 ◽

Cited By ~ 111

Author(s):

William J. Randel ◽

Mijeong Park ◽

Fei Wu ◽

Nathaniel Livesey

Keyword(s):

Annual Cycle ◽

Seasonal Cycle ◽

Annual Variation ◽

Lower Stratosphere ◽

Vertical Gradient ◽

Relative Amplitude ◽

Vertical Layer ◽

Satellite Measurements ◽

Tropical Tropopause ◽

Vertical Gradients

Abstract Near-equatorial ozone observations from balloon and satellite measurements reveal a large annual cycle in ozone above the tropical tropopause. The relative amplitude of the annual cycle is large in a narrow vertical layer between ∼16 and 19 km, with approximately a factor of 2 change in ozone between the minimum (during NH winter) and maximum (during NH summer). The annual cycle in ozone occurs over the same altitude region, and is approximately in phase with the well-known annual variation in tropical temperature. This study shows that the large annual variation in ozone occurs primarily because of variations in vertical transport associated with mean upwelling in the lower stratosphere (the Brewer–Dobson circulation); the maximum relative amplitude peak in the lower stratosphere is collocated with the strongest background vertical gradients in ozone. A similar large seasonal cycle is observed in carbon monoxide (CO) above the tropical tropopause, which is approximately out of phase with ozone (associated with an oppositely signed vertical gradient). The observed ozone and CO variations can be used to constrain estimates of the seasonal cycle in tropical upwelling.

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Construction of the RSS V3.2 Lower-Tropospheric Temperature Dataset from the MSU and AMSU Microwave Sounders

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2009jtecha1237.1 ◽

2009 ◽

Vol 26 (8) ◽

pp. 1493-1509 ◽

Cited By ~ 52

Author(s):

Carl A. Mears ◽

Frank J. Wentz

Keyword(s):

Lower Stratosphere ◽

Weighting Function ◽

Lower Troposphere ◽

Weighted Average ◽

Atmospheric Temperature ◽

Tropospheric Temperature ◽

Satellite Measurements ◽

Microwave Sounding Unit ◽

Different Types ◽

Microwave Sounding

Abstract Measurements made by microwave sounding instruments provide a multidecadal record of atmospheric temperature in several thick atmospheric layers. Satellite measurements began in late 1978 with the launch of the first Microwave Sounding Unit (MSU) and have continued to the present via the use of measurements from the follow-on series of instruments, the Advanced Microwave Sounding Unit (AMSU). The weighting function for MSU channel 2 is centered in the middle troposphere but contains significant weight in the lower stratosphere. To obtain an estimate of tropospheric temperature change that is free from stratospheric effects, a weighted average of MSU channel 2 measurements made at different local zenith angles is used to extrapolate the measurements toward the surface, which results in a measurement of changes in the lower troposphere. In this paper, a description is provided of methods that were used to extend the MSU method to the newer AMSU channel 5 measurements and to intercalibrate the results from the different types of satellites. Then, satellite measurements are compared to results from homogenized radiosonde datasets. The results are found to be in excellent agreement with the radiosonde results in the northern extratropics, where the majority of the radiosonde stations are located.

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Direct radiative effect of the Russian wildfires and its impact on air temperature and atmospheric dynamics during August 2010

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-1999-2014 ◽

2014 ◽

Vol 14 (4) ◽

pp. 1999-2013 ◽

Cited By ~ 34

Author(s):

J. C. Péré ◽

B. Bessagnet ◽

M. Mallet ◽

F. Waquet ◽

I. Chiapello ◽

...

Keyword(s):

Optical Properties ◽

Wind Speed ◽

Eastern Europe ◽

Air Temperature ◽

Air Entrainment ◽

Atmospheric Dynamics ◽

Horizontal Wind ◽

Satellite Measurements ◽

Near Surface ◽

Aerosol Plume

Abstract. In this study, we investigate the shortwave aerosol direct radiative forcing (ADRF) and its feedback on air temperature and atmospheric dynamics during a major fire event that occurred in Russia during August 2010. The methodology is based on an offline coupling between the CHIMERE chemistry-transport and the Weather Research and Forecasting (WRF) models. First, simulations for the period 5–12 August 2010 have been evaluated by using AERONET (AErosol RObotic NETwork) and satellite measurements of the POLarization and Directionality of the Earth's Reflectance (POLDER) and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) sensors. During this period, elevated POLDER aerosol optical thickness (AOT) is found over a large part of eastern Europe, with values above 2 (at 550 nm) in the aerosol plume. According to CALIOP observations, particles remain confined to the first five kilometres of the atmospheric layer. Comparisons with satellite measurements show the ability of CHIMERE to reproduce the regional and vertical distribution of aerosols during their transport from the source region. Over Moscow, AERONET measurements indicate an important increase of AOT (340 nm) from 0.7 on 5 August to 2–4 between 6 and 10 August when the aerosol plume was advected over the city. Particles are mainly observed in the fine size mode (radius in the range 0.2–0.4 μm) and are characterized by elevated single-scattering albedo (SSA) (0.95–0.96 between 440 and 1020 nm). Comparisons of simulations with AERONET measurements show that aerosol physical–optical properties (size distribution, AOT, SSA) have been well simulated over Moscow in terms of intensity and/or spectral dependence. Secondly, modelled aerosol optical properties have been used as input in the radiative transfer code of WRF to evaluate their direct radiative impact. Simulations indicate a significant reduction of solar radiation at the ground (up to 80–150 W m−2 in diurnal averages over a large part of eastern Europe due to the presence of the aerosol plume. This ADRF causes an important reduction of the near-surface air temperature between 0.2 and 2.6° on a regional scale. Moscow has been affected by the aerosol plume, especially between 6 and 10 August. During this period, aerosol causes a significant reduction of surface shortwave radiation (up to 70–84 W m−2 in diurnal averages) with a moderate part (20–30%) due to solar absorption within the aerosol layer. The resulting feedbacks lead to a cooling of the air up to 1.6° at the surface and 0.1° at an altitude of 1500–2000 m (in diurnal averages), that contribute to stabilize the atmospheric boundary layer (ABL). Indeed, a reduction of the ABL height of 13 to 65% has been simulated during daytime in presence of aerosols. This decrease is the result of a lower air entrainment as the vertical wind speed in the ABL is shown to be reduced by 5 to 80% (at midday) when the feedback of the ADRF is taken into account. However, the ADRF is shown to have a lower impact on the horizontal wind speed, suggesting that the dilution of particles would be mainly affected by the weakening of the ABL development and associated vertical entrainment. Indeed, CHIMERE simulations driven by the WRF meteorological fields including this ADRF feedback result in a large increase in the modelled near-surface PM10 concentrations (up to 99%). This is due to their lower vertical dilution in the ABL, which tend to reduce model biases with the ground PM10 values observed over Moscow during this specific period.

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Impact of the Christmas 2018 Mount Etna Eruption on the Regional Air Quality

10.5194/egusphere-egu21-2167 ◽

2021 ◽

Author(s):

Claire Lamotte ◽

Jonathan Guth ◽

Virginie Marécal ◽

Giuseppe Salerno ◽

Nicolas Theys ◽

...

Keyword(s):

Air Quality ◽

Regional Scale ◽

Volcanic Eruptions ◽

Mount Etna ◽

Surface Measurement ◽

Volcanic Plume ◽

Observation Data ◽

Sulfate Aerosols ◽

Lower Altitude ◽

The Impact

Volcanic eruptions are events that can eject several tons of material into the atmosphere. Among these emissions, sulfur dioxide is the main sulfurous volcanic gas. It can form sulfate aerosols that are harmful to health or, being highly soluble, it can condense in water particles and form acid rain. Thus, volcanic eruptions can have an environmental impact on a regional scale.The Mediterranean region is very interesting from this point of view because it is a densely populated region with a strong anthropogenic activity, therefore polluted, in which Mount Etna is also located. Mount Etna is the largest passive SO2 emitter in Europe, but it can also sporadically produce strong eruptive events. It is then likely that the additional input of sulfur compounds into the atmosphere by volcanic emissions may have effects on the regional atmospheric sulfur composition.We are particularly investigating the eruption of Mount Etna on December 24, 2018 [Corradini et al, 2020]. This eruption took place along a 2 km long breach on the side of the volcano, thus at a lower altitude than its main crater. About 100 kt of SO2 and 35 kt of ash were released in total, between December 24 and 30. With the exception of the 24th, the quantities of ash were always lower than the SO2.The availability of the TROPOMI SO2column estimates, at fine spatial resolution (7 km x 3.5 km at nadir) and associated averaging kernels, during this eruptive period made it also an excellent case study. It allows us to follow the evolution of SO2 in the volcanic plume over several days.Using the CNRM MOCAGE chemistry-transport model (CTM), we aim to quantify the impact of this volcanic eruption on atmospheric composition, sulfur deposition and air quality at the regional scale. The comparison of the model with the TROPOMI observation data allows us to assess the ability of the model to properly represent the plume. In spite of a particular meteorological situation, leading to a complex plume transport, MOCAGE shows a good agreement with TROPOMI observations. Thus, from the MOCAGE simulation, we can evaluate the impact of the eruption on the regional concentrations of SO2 and sulfate aerosols, but also analyse the quantities of dry and wet deposition, and compare it to surface measurement stations.

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