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McGrory MR, Shepherd RH, King MD, Davidson N, Pope FD, Watson IM, Grainger RG, Jones AC, Ward AD. Mie scattering from optically levitated mixed sulfuric acid-silica core-shell aerosols: observation of core-shell morphology for atmospheric science. Phys Chem Chem Phys 2022; 24:5813-5822. [PMID: 35226003 DOI: 10.1039/d1cp04068e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sulfuric acid is shown to form a core-shell particle on a micron-sized, optically-trapped spherical silica bead. The refractive indices of the silica and sulfuric acid, along with the shell thickness and bead radius were determined by reproducing Mie scattered optical white light as a function of wavelength in Mie spectroscopy. Micron-sized silica aerosols (silica beads were used as a proxy for atmospheric silica minerals) were levitated in a mist of sulfuric acid particles; continuous collection of Mie spectra throughout the collision of sulfuric acid aerosols with the optically trapped silica aerosol demonstrated that the resulting aerosol particle had a core-shell morphology. Contrastingly, the collision of aqueous sulfuric acid aerosols with optically trapped polystyrene aerosol resulted in a partially coated system. The light scattering from the optically levitated aerosols was successfully modelled to determine the diameter of the core aerosol (±0.003 μm), the shell thickness (±0.0003 μm) and the refractive index (±0.007). The experiment demonstrated that the presence of a thin film rapidly changed the light scattering of the original aerosol. When a 1.964 μm diameter silica aerosol was covered with a film of sulfuric acid 0.287 μm thick, the wavelength dependent Mie peak positions resembled sulfuric acid. Thus mineral aerosol advected into the stratosphere would likely be coated with sulfuric acid, with a core-shell morphology, and its light scattering properties would be effectively indistinguishable from a homogenous sulfuric acid aerosol if the film thickness was greater than a few 100 s of nm for UV-visible wavelengths.
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Affiliation(s)
- Megan R McGrory
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK. .,Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Rosalie H Shepherd
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK. .,Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Martin D King
- Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Nicholas Davidson
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Francis D Pope
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - I Matthew Watson
- School of Earth Science, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ, UK
| | - Roy G Grainger
- National Centre for Earth Observation, Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Anthony C Jones
- Met Office, Fitzroy Road, Exeter, EX1 3PB, UK.,College of Engineering Maths and Physical Sciences, University of Exeter, Exeter, EX4 4PY, UK
| | - Andrew D Ward
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK.
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2
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Hirsch E, Koren I. Record-breaking aerosol levels explained by smoke injection into the stratosphere. Science 2021; 371:1269-1274. [DOI: 10.1126/science.abe1415] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 02/03/2021] [Indexed: 11/02/2022]
Affiliation(s)
- Eitan Hirsch
- Environmental Sciences Division, Israel Institute for Biological Research, Nes-Ziona 7404801, Israel
| | - Ilan Koren
- Department of Earth and Planetary Sciences, Weizmann Institute, Rehovot 76100, Israel
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3
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Fadnavis S, Müller R, Chakraborty T, Sabin TP, Laakso A, Rap A, Griessbach S, Vernier JP, Tilmes S. The role of tropical volcanic eruptions in exacerbating Indian droughts. Sci Rep 2021; 11:2714. [PMID: 33526810 PMCID: PMC7851170 DOI: 10.1038/s41598-021-81566-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 01/06/2021] [Indexed: 01/30/2023] Open
Abstract
The Indian summer monsoon rainfall (ISMR) is vital for the livelihood of millions of people in the Indian region; droughts caused by monsoon failures often resulted in famines. Large volcanic eruptions have been linked with reductions in ISMR, but the responsible mechanisms remain unclear. Here, using 145-year (1871-2016) records of volcanic eruptions and ISMR, we show that ISMR deficits prevail for two years after moderate and large (VEI > 3) tropical volcanic eruptions; this is not the case for extra-tropical eruptions. Moreover, tropical volcanic eruptions strengthen El Niño and weaken La Niña conditions, further enhancing Indian droughts. Using climate-model simulations of the 2011 Nabro volcanic eruption, we show that eruption induced an El Niño like warming in the central Pacific for two consecutive years due to Kelvin wave dissipation triggered by the eruption. This El Niño like warming in the central Pacific led to a precipitation reduction in the Indian region. In addition, solar dimming caused by the volcanic plume in 2011 reduced Indian rainfall.
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Affiliation(s)
| | - Rolf Müller
- Forschungszentrum Jülich GmbH, IEK7, Jülich, Germany
| | | | - T P Sabin
- Indian Institute of Tropical Meteorology, MoES, Pune, India
| | - Anton Laakso
- Finnish Meteorological Institute, Kuopio, Finland
| | - Alexandru Rap
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - Sabine Griessbach
- Forschungszentrum Jülich GmbH, Jülich Supercomputing Center, Jülich, Germany
| | - Jean-Paul Vernier
- National Institute of Aerospace, Hampton, VA, USA
- NASA Langley Research Center, Hampton, VA, USA
| | - Simone Tilmes
- National Center for Atmospheric Research, Boulder, USA
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4
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A Decadal Global Climatology of Ice Cloud Fraction with Their Microphysical and Optical Properties Inferred from the CALIPSO and Reanalysis Data. REMOTE SENSING 2020. [DOI: 10.3390/rs12223795] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the present study, the spatiotemporal and vertical distributions of ice cloud properties and their association with meteorological variables are analyzed for the period 2007–2016 using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Modern Era Retrospective-Analysis for Research (MERRA-2) reanalysis observations. The distribution of ice cloud fraction (ICF) with its peak does not overlap with that of the ice water content (IWC) peak during daytime and nighttime due to the sampling bias. Moreover, the vertical distributions of mean IWC exhibited a vaguely “sharp thorn” at an altitude of ~4 km in all seasons at the location of about ±40°, which can be caused by the artifacts. Furthermore, it is noted that different ice cloud optical depth (ICOD) presents significant changes observed in their diurnal variations in the heights of peaks. The maximum diurnal difference of ice cloud properties occurs in the tropical regions of the North Hemisphere (NH) during summer. We also investigated the relation between ICOD and the meteorological variables and found that the ICOD values are dependent on the meteorological parameters.
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5
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Kozun MN, Bourassa AE, Degenstein DA, Loewen PR. A multi-spectral polarimetric imager for atmospheric profiling of aerosol and thin cloud: Prototype design and sub-orbital performance. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:103106. [PMID: 33138590 DOI: 10.1063/5.0016129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 09/23/2020] [Indexed: 06/11/2023]
Abstract
We report on the development of a novel multi-spectral polarimetric imager for atmospheric remote sensing of aerosol and cloud properties. The instrument concept, called the Aerosol Limb Imager (ALI), is ultimately intended for satellite measurements from a low Earth orbit. It utilizes a coupling of a dual transducer acousto-optic tunable filter and a liquid crystal rotator to provide dual linear polarization observations over a wide spectral range covering 600 nm-1500 nm. In the limb, or side-viewing, geometry, these measurements provide the capability to resolve vertical and horizontal distributions of aerosol and cloud properties such as extinction coefficient, optical depth, and particle distribution parameters. Here, we present the design and performance of an ALI prototype. Lab characterization of the instrument is used to develop a mathematical instrument model to predict signal levels under various atmospheric conditions. Results from a sub-orbital flight of the ALI prototype on a stabilized high-altitude stratospheric balloon gondola are presented that show the first known polarimetric, multi-spectral images of the limb radiance. The signal levels obtained agree reasonably well with those predicted by the instrument model using radiative transfer calculations for typical atmospheric conditions.
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Affiliation(s)
- M N Kozun
- Institute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - A E Bourassa
- Institute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - D A Degenstein
- Institute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - P R Loewen
- Institute for Space and Atmospheric Studies, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
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6
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Sandvik OS, Friberg J, Martinsson BG, van Velthoven PFJ, Hermann M, Zahn A. Intercomparison of in-situ aircraft and satellite aerosol measurements in the stratosphere. Sci Rep 2019; 9:15576. [PMID: 31666595 PMCID: PMC6821816 DOI: 10.1038/s41598-019-52089-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 10/10/2019] [Indexed: 11/18/2022] Open
Abstract
Aerosol composition and optical scattering from particles in the lowermost stratosphere (LMS) have been studied by comparing in-situ aerosol samples from the IAGOS-CARIBIC passenger aircraft with vertical profiles of aerosol backscattering obtained from the CALIOP lidar aboard the CALIPSO satellite. Concentrations of the dominating fractions of the stratospheric aerosol, being sulphur and carbon, have been obtained from post-flight analysis of IAGOS-CARIBIC aerosol samples. This information together with literature data on black carbon concentrations were used to calculate the aerosol backscattering which subsequently is compared with measurements by CALIOP. Vertical optical profiles were taken in an altitude range of several kilometres from and above the northern hemispheric extratropical tropopause for the years 2006-2014. We find that the two vastly different measurement platforms yield different aerosol backscattering, especially close to the tropopause where the influence from tropospheric aerosol is strong. The best agreement is found when the LMS is affected by volcanism, i.e., at elevated aerosol loadings. At background conditions, best agreement is obtained some distance (>2 km) above the tropopause in winter and spring, i.e., at likewise elevated aerosol loadings from subsiding aerosol-rich stratospheric air. This is to our knowledge the first time the CALIPSO lidar measurements have been compared to in-situ long-term aerosol measurements.
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Affiliation(s)
| | - Johan Friberg
- Division of Nuclear Physics, Lund University, Lund, Sweden
| | | | | | - Markus Hermann
- Leibniz Institute for Tropospheric Research, Leipzig, Germany
| | - Andreas Zahn
- Institute of Meteorology and Climate Research, Institute of Technology, Karlsruhe, Germany
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7
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Peterson DA, Campbell JR, Hyer EJ, Fromm MD, Kablick GP, Cossuth JH, DeLand MT. Wildfire-driven thunderstorms cause a volcano-like stratospheric injection of smoke. NPJ CLIMATE AND ATMOSPHERIC SCIENCE 2018; 1:10.1038/s41612-018-0039-3. [PMID: 31360778 PMCID: PMC6662724 DOI: 10.1038/s41612-018-0039-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 06/21/2018] [Accepted: 07/13/2018] [Indexed: 06/02/2023]
Abstract
Intense heating by wildfires can generate deep, smoke-infused thunderstorms, known as pyrocumulonimbus (pyroCb), which can release a large quantity of smoke particles above jet aircraft cruising altitudes. Injections of pyroCb smoke into the lower stratosphere have gained increasing attention over the past 15 years due to the rapid proliferation of satellite remote sensing tools. Impacts from volcanic eruptions and other troposphere-to-stratosphere exchange processes on stratospheric radiative and chemical equilibrium are well recognized and monitored. However, the role of pyroCb smoke in the climate system has yet to be acknowledged. Here, we show that the mass of smoke aerosol particles injected into the lower stratosphere from five near-simultaneous intense pyroCbs occurring in western North America on 12 August 2017 was comparable to that of a moderate volcanic eruption, and an order of magnitude larger than previous benchmarks for extreme pyroCb activity. The resulting stratospheric plume encircled the Northern Hemisphere over several months. By characterizing this event, we conclude that pyroCb activity, considered as either large singular events, or a full fire season inventory, significantly perturb the lower stratosphere in a manner comparable with infrequent volcanic intrusions.
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Affiliation(s)
- David A. Peterson
- Naval Research Laboratory, 7 Grace Hopper Avenue, Monterey, CA 93943, USA
| | - James R. Campbell
- Naval Research Laboratory, 7 Grace Hopper Avenue, Monterey, CA 93943, USA
| | - Edward J. Hyer
- Naval Research Laboratory, 7 Grace Hopper Avenue, Monterey, CA 93943, USA
| | - Michael D. Fromm
- Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA
| | - George P. Kablick
- Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA
| | - Joshua H. Cossuth
- Naval Research Laboratory, 7 Grace Hopper Avenue, Monterey, CA 93943, USA
| | - Matthew T. DeLand
- Science Systems and Applications, Inc. (SSAI), 10210 Greenbelt Road, Suite 600, Lanham, MD 20706, USA
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8
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Millar RJ, Friedlingstein P. The utility of the historical record for assessing the transient climate response to cumulative emissions. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2016.0449. [PMID: 29610381 PMCID: PMC5897822 DOI: 10.1098/rsta.2016.0449] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 01/19/2018] [Indexed: 06/08/2023]
Abstract
The historical observational record offers a way to constrain the relationship between cumulative carbon dioxide emissions and global mean warming. We use a standard detection and attribution technique, along with observational uncertainties to estimate the all-forcing or 'effective' transient climate response to cumulative emissions (TCRE) from the observational record. Accounting for observational uncertainty and uncertainty in historical non-CO2 radiative forcing gives a best-estimate from the historical record of 1.84°C/TtC (1.43-2.37°C/TtC 5-95% uncertainty) for the effective TCRE and 1.31°C/TtC (0.88-2.60°C/TtC 5-95% uncertainty) for the CO2-only TCRE. While the best-estimate TCRE lies in the lower half of the IPCC likely range, the high upper bound is associated with the not-ruled-out possibility of a strongly negative aerosol forcing. Earth System Models have a higher effective TCRE range when compared like-for-like with the observations over the historical period, associated in part with a slight underestimate of diagnosed cumulative emissions relative to the observational best-estimate, a larger ensemble mean-simulated CO2-induced warming, and rapid post-2000 non-CO2 warming in some ensemble members.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.
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Affiliation(s)
- Richard J Millar
- College of Engineering, Mathematical and Physical Sciences, University of Exeter, Exeter, UK
- Environmental Change Institute, University of Oxford, Oxford, UK
| | - Pierre Friedlingstein
- College of Engineering, Mathematical and Physical Sciences, University of Exeter, Exeter, UK
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9
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Medhaug I, Stolpe MB, Fischer EM, Knutti R. Reconciling controversies about the 'global warming hiatus'. Nature 2017; 545:41-47. [PMID: 28470193 DOI: 10.1038/nature22315] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 03/28/2017] [Indexed: 11/09/2022]
Abstract
Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the 'global warming hiatus', caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of 'hiatus' and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.
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Affiliation(s)
- Iselin Medhaug
- Institute for Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
| | - Martin B Stolpe
- Institute for Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
| | - Erich M Fischer
- Institute for Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
| | - Reto Knutti
- Institute for Atmospheric and Climate Science, ETH Zürich, 8092 Zürich, Switzerland
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10
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Efficient transport of tropospheric aerosol into the stratosphere via the Asian summer monsoon anticyclone. Proc Natl Acad Sci U S A 2017. [PMID: 28630285 DOI: 10.1073/pnas.1701170114] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An enhanced aerosol layer near the tropopause over Asia during the June-September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance. The in situ measurements revealed a robust enhancement in aerosol concentration that extended up to 2 km above the tropopause. A climate model simulation demonstrates that the abundant anthropogenic aerosol precursor emissions from Asia coupled with rapid vertical transport associated with monsoon convection leads to significant particle formation in the upper troposphere within the ASM anticyclone. These particles subsequently spread throughout the entire Northern Hemispheric (NH) lower stratosphere and contribute significantly (∼15%) to the NH stratospheric column aerosol surface area on an annual basis. This contribution is comparable to that from the sum of small volcanic eruptions in the period between 2000 and 2015. Although the ASM contribution is smaller than that from tropical upwelling (∼35%), we find that this region is about three times as efficient per unit area and time in populating the NH stratosphere with aerosol. With a substantial amount of organic and sulfur emissions in Asia, the ASM anticyclone serves as an efficient smokestack venting aerosols to the upper troposphere and lower stratosphere. As economic growth continues in Asia, the relative importance of Asian emissions to stratospheric aerosol is likely to increase.
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11
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Kim MH, Omar AH, Vaughan MA, Winker DM, Trepte CR, Hu Y, Liu Z, Kim SW. Quantifying the low bias of CALIPSO's column aerosol optical depth due to undetected aerosol layers. JOURNAL OF GEOPHYSICAL RESEARCH. ATMOSPHERES : JGR 2017; 122:1098-1113. [PMID: 31534879 PMCID: PMC6749610 DOI: 10.1002/2016jd025797] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The CALIOP data processing scheme only retrieves extinction profiles in those portions of the return signal where cloud or aerosol layers have been identified by the CALIOP layer detection scheme. In this study we use two years of CALIOP and MODIS data to quantify the aerosol optical depth of undetected weakly backscattering layers. Aerosol extinction and column-averaged lidar ratio is retrieved from CALIOP Level 1B (Version 4) profile using MODIS AOD as a constraint over oceans from March 2013 to February 2015. To quantify the undetected layer AOD (ULA), an unconstrained retrieval is applied globally using a lidar ratio of 28.75 sr estimated from constrained retrievals during the daytime over the ocean. We find a global mean ULA of 0.031 ± 0.052. There is no significant difference in ULA between land and ocean. However, the fraction of undetected aerosol layers rises considerably during daytime, when the large amount of solar background noise lowers the signal to noise ratio (SNR). For this reason, there is a difference in ULA between day (0.036 ± 0.066) and night (0.025 ± 0.021). ULA is larger in the northern hemisphere and relatively larger at high latitudes. Large ULA for the Polar Regions is strongly related to the cases where the CALIOP Level 2 Product reports zero AOD. This study provides an estimate of the complement of AOD that is not detected by lidar, and bounds the CALIOP AOD uncertainty to provide corrections for science studies that employ the CALIOP Level 2 AOD.
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Affiliation(s)
- Man-Hae Kim
- NASA Langley Research Center, Hampton, VA, USA
- Universities Space Research Association, Columbia, Maryland, USA
| | - Ali H. Omar
- NASA Langley Research Center, Hampton, VA, USA
| | | | | | | | | | - Zhaoyan Liu
- NASA Langley Research Center, Hampton, VA, USA
- Science Systems and Applications, Inc., Hampton, VA, USA
| | - Sang-Woo Kim
- School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea
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12
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Vernier J, Fairlie TD, Deshler T, Natarajan M, Knepp T, Foster K, Wienhold FG, Bedka KM, Thomason L, Trepte C. In situ and space-based observations of the Kelud volcanic plume: The persistence of ash in the lower stratosphere. JOURNAL OF GEOPHYSICAL RESEARCH. ATMOSPHERES : JGR 2016; 121:11104-11118. [PMID: 29082118 PMCID: PMC5646265 DOI: 10.1002/2016jd025344] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 08/29/2016] [Accepted: 09/01/2016] [Indexed: 06/07/2023]
Abstract
Volcanic eruptions are important causes of natural variability in the climate system at all time scales. Assessments of the climate impact of volcanic eruptions by climate models almost universally assume that sulfate aerosol is the only radiatively active volcanic material. We report satellite observations from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite after the eruption of Mount Kelud (Indonesia) on 13 February 2014 of volcanic materials in the lower stratosphere. Using these observations along with in situ measurements with the Compact Optical Backscatter AerosoL Detector (COBALD) backscatter sondes and optical particle counters (OPCs) made during a balloon field campaign in northern Australia, we find that fine ash particles with a radius below 0.3 µm likely represented between 20 and 28% of the total volcanic cloud aerosol optical depth 3 months after the eruption. A separation of 1.5-2 km between the ash and sulfate plumes is observed in the CALIOP extinction profiles as well as in the aerosol number concentration measurements of the OPC after 3 months. The settling velocity of fine ash with a radius of 0.3 µm in the tropical lower stratosphere is reduced by 50% due to the upward motion of the Brewer-Dobson circulation resulting a doubling of its lifetime. Three months after the eruption, we find a mean tropical clear-sky radiative forcing at the top of the atmosphere from the Kelud plume near -0.08 W/m2 after including the presence of ash; a value ~20% higher than if sulfate alone is considered. Thus, surface cooling following volcanic eruptions could be affected by the persistence of ash and should be considered in climate simulations.
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Affiliation(s)
- Jean‐Paul Vernier
- Science Systems and Applications, Inc.HamptonUSA
- NASA Langley Research CenterHamptonVirginiaUSA
| | | | - Terry Deshler
- Department of Atmospheric ScienceUniversity of WyomingLaramieWyomingUSA
| | | | - Travis Knepp
- Science Systems and Applications, Inc.HamptonUSA
- NASA Langley Research CenterHamptonVirginiaUSA
| | - Katie Foster
- Department of Atmospheric ScienceUniversity of WyomingLaramieWyomingUSA
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