Infrared absorption by volcanic stratospheric aerosols observed by ISAMS

Grainger, Roy G.; Lambert, A.; Taylor, F. W.; Remedios, J. J.; Rodgers, C. D.; Corney, M.; Kerridge, B. J.

doi:10.1029/93gl00823

Cited by 56 publications

(32 citation statements)

References 17 publications

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“…Examples include the limb viewing SAGE II instrument at visible and near infrared wavelengths (Thomason et al, 1997;Bauman et al, 2003) and CLAES and ISAMS at infrared wavelengths (Rogers et al, 1998;Lambert et al, 1997). While shortwave instruments can measure an increase in aerosols, infrared instruments are sensitive to particle composition and in ISAMS and AT-MOS infrared measurements performed after the Pinatubo eruption, it was possible to unambiguously identify the specific infrared spectral signature of sulfuric acid-water drops (Grainer et al, 1993;Echle et al, 1998;Eldering et al, 2001Eldering et al, , 2004Steele et al, 2006). Nadir observations of sulfuric acid aerosols include the optical depth measurements made by the NOAA/AVHRR sounder (Stowe et al, 1992;Long and Stowe, 1994) ( Ackerman and Strabala, 1994).…”

Section: Sulfuric Acid Dropletsmentioning

confidence: 99%

“…To increase sensitivity, not a global but a local covariance matrix was built, representative for each 10 by 10 degree grid cell. For the calculation of the Jacobian, a choice has to be made for a representative size distribution, temperature and sulfate concentration (Steele and Hamill, 1981;Grainer et al, 1993). A concentration of 75 % H 2 SO 4 was chosen, with droplets following a logarithmic size distribution with an effective radius of 1 µm.…”

Section: Sulfuric Acid Dropletsmentioning

confidence: 99%

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A unified approach to infrared aerosol remote sensing and type specification

et al. 2013

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Atmospheric aerosols impact air quality and global climate. Space based measurements are the best way to observe their spatial and temporal distributions, and can also be used to gain better understanding of their chemical, physical and optical properties. Aerosol composition is the key parameter affecting the refractive index, which determines how much radiation is scattered and absorbed. Composition of aerosols is unfortunately not measured by state of the art satellite remote sounders. Here we use high resolution infrared measurements for aerosol type differentiation, exploiting, in that part of spectrum, the dependency of their refractive index on wavelength. We review existing detection methods and present a unified detection method based on linear discrimination analysis. We demonstrate this method on measurements of the Infrared Atmospheric Sounding Interferometer (IASI) and five different aerosol types, namely volcanic ash, windblown sand, sulfuric acid droplets, ammonium sulfate and smoke particles. We compare these with traditional MODIS AOD measurements. The detection of the last three types is unprecedented in the infrared in nadir mode, but is very promising, especially for sulfuric acid droplets which are detected in the lower troposphere and up to 6 months after injection in the upper troposphere/lower stratosphere

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Section: Sulfuric Acid Dropletsmentioning

confidence: 99%

Section: Sulfuric Acid Dropletsmentioning

confidence: 99%

A unified approach to infrared aerosol remote sensing and type specification

et al. 2013

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“…From a number of complementary measurements the knowledge was established that stratospheric aerosol is composed primarily of sulphuric acid and water during both volcanically active and quiescent periods (e.g. Junge et al, 1961;Rosen, 1971;Hofmann and Rosen, 1961;Deshler et al, 1992;Sheridan et al, 1992;Grainger at al., 1993;Arnold et al, 1998;Murphy et al, 1998). Under background conditions, these originate mainly from the tropospheric source gases carbonyl sulphide (OCS), (an inert sulphur bearing molecule), and SO 2 , and from direct injections of sulphate particles (Crutzen, 1976;Turco et al, 1980;Weisenstein and Bekki, 2006).…”

Section: Introductionmentioning

confidence: 99%

Optimal estimation retrieval of aerosol microphysical properties from SAGE~II satellite observations in the volcanically unperturbed lower stratosphere

et al. 2010

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Abstract. Stratospheric aerosol particles under non-volcanic conditions are typically smaller than 0.1 µm. Due to fundamental limitations of the scattering theory in the Rayleigh limit, these tiny particles are hard to measure by satellite instruments. As a consequence, current estimates of global aerosol properties retrieved from spectral aerosol extinction measurements tend to be strongly biased. Aerosol surface area densities, for instance, are observed to be about 40% smaller than those derived from correlative in situ measurements . An accurate knowledge of the global distribution of aerosol properties is, however, essential to better understand and quantify the role they play in atmospheric chemistry, dynamics, radiation and climate.To address this need a new retrieval algorithm was developed, which employs a nonlinear Optimal Estimation (OE) method to iteratively solve for the monomodal size distribution parameters which are statistically most consistent with both the satellite-measured multi-wavelength aerosol extinction data and a priori information. By thus combining spectral extinction measurements (at visible to near infrared wavelengths) with prior knowledge of aerosol properties at background level, even the smallest particles are taken into account which are practically invisible to optical remote sensing instruments.The performance of the OE retrieval algorithm was assessed based on synthetic spectral extinction data generated from both monomodal and small-mode-dominant bimodal sulphuric acid aerosol size distributions. For monomodal background aerosol, the new algorithm was shown to fairly Correspondence to: D. Wurl (daniela wurl@yahoo.de) accurately retrieve the particle sizes and associated integrated properties (surface area and volume densities), even in the presence of large extinction uncertainty. The associated retrieved uncertainties are a good estimate of the true errors. In the case of bimodal background aerosol, where the retrieved (monomodal) size distributions naturally differ from the correct bimodal values, the associated surface area (A) and volume densities (V ) are, nevertheless, fairly accurately retrieved, except at values larger than 1.0 µm 2 cm −3 (A) and 0.05 µm 3 cm −3 (V ), where they tend to underestimate the true bimodal values. Due to the limited information content in the SAGE II spectral extinction measurements this kind of forward model error cannot be avoided here. Nevertheless, the retrieved uncertainties are a good estimate of the true errors in the retrieved integrated properties, except where the surface area density exceeds the 1.0 µm 2 cm −3 threshold.When applied to near-global SAGE II satellite extinction measured in 1999 the retrieved OE surface area and volume densities are observed to be larger by, respectively, 20-50% and 10-40% compared to those estimates obtained by the SAGE II operational retrieval algorithm. An examination of the OE algorithm biases with in situ data indicates that the new OE aerosol property estimates tend to be more realistic tha...

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“…The circulation in the lower atmosphere can be affected by short term stratospheric perturbations, for example, ozone changes (Rind et al, 1992;Grainger et al, 1993;Kodera, 1994;Randel et al, 1995;Timmreck et al, 2003). It is thus interesting to explore the various ways in which the stratospheric perturbations can influence the tropospheric circulation.…”

Section: Introductionmentioning

confidence: 99%

Simulation of the climate impact of Mt. Pinatubo eruption using ECHAM5 – Part 1: Sensitivity to the modes of atmospheric circulation and boundary conditions

et al. 2009

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Abstract. The eruption of Mt. Pinatubo in the Philippines in June 1991 was one of the strongest volcanic eruptions in the 20th century and this well observed eruption can serve as an important case study to understand the subsequent weather and climate changes. In this paper, the most comprehensive simulations to date of the climate impact of Mt. Pinatubo eruption are carried out with prescribed volcanic aerosols including observed SSTs, QBO and volcanically induced ozone anomalies. This is also the first attempt to include all the known factors for the simulation of such an experiment. Here, the climate response is evaluated under different boundary conditions including one at a time, thereby, investigating the radiative and dynamical responses to individual and combined forcings by observed SSTs, QBO and volcanic effects. Two ensembles of ten members each, for unperturbed and volcanically perturbed conditions were carried out using the middle atmosphere configuration of ECHAM5 general circulation model. Our results show that the simulated climate response that may arise solely from aerosol forcing in lower stratospheric temperature is insensitive to the boundary conditions in the tropics and does not show some observed features such as the temperature signature of the QBO phases. Also, statistically significant positive anomalies in the high latitudes in NH winter of 1991/92 seen in our model simulations with prescribed observed SST and QBO phases as boundary conditions are consistent with the observations. To simulate realistically the lower stratospheric temperature response, one must include all the known factors. The pure QBO and ocean signatures in lower stratospheric temperature are simulated conCorrespondence to: M. A. Thomas (manu.thomas@zmaw.de) sistently with earlier studies. The indirect effect of the volcanic aerosols manifested as the winter warming pattern is not simulated in the ensemble mean of the experiments. Our analysis also shows that the response to El Niño conditions is very strong in the model and that it partially masks the effects due to volcanic forcing.

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Infrared absorption by volcanic stratospheric aerosols observed by ISAMS

Cited by 56 publications

References 17 publications

A unified approach to infrared aerosol remote sensing and type specification

A unified approach to infrared aerosol remote sensing and type specification

Optimal estimation retrieval of aerosol microphysical properties from SAGE~II satellite observations in the volcanically unperturbed lower stratosphere

Simulation of the climate impact of Mt. Pinatubo eruption using ECHAM5 – Part 1: Sensitivity to the modes of atmospheric circulation and boundary conditions

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