Variation in the Stratospheric Aerosol Associated with the North Cyclonic Polar Vortex as Measured by the SAM II Satellite Sensor

Kent, G. S.; Trepte, Charles R.; Farrukh, Usamah O.; McCormick, M. P.

doi:10.1175/1520-0469(1985)042<1536:vitsaa>2.0.co;2

Cited by 71 publications

(42 citation statements)

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“…The apparent bias at low aerosol extinction is primarily driven by events occurring within the Arctic vortex (where matches with SAGE II are unfortunately sparse). Within the vortex, SAGE III typically reports low extinction at all wavelengths which is consistent with observations reported by Kent et al (1985) and Thomason and Poole (1994) (Thomason et al, 2008) and, as a result, good agreement between the three instruments is expected. On the other hand, at 449 nm the fraction of the signal from aerosol is less than 10% and therefore a more challenging measurement.…”

Section: Comparisons With Sage II and Poam Iiisupporting

confidence: 89%

An evaluation of the SAGE III version 4 aerosol extinction coefficient and water vapor data products

et al. 2010

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Abstract. Herein, we provide an assessment of the data quality of Stratospheric Aerosol and Gas Experiment (SAGE III) Version 4 aerosol extinction coefficient and water vapor data products. The evaluation is based on comparisons with data from four instruments: SAGE II, the Polar Ozone and Aerosol Measurement (POAM III), the Halogen Occultation Experiment (HALOE), and the Microwave Limb Sounder (MLS). Since only about half of the SAGE III channels have a direct comparison with measurements by other instruments, we have employed some empirical techniques to evaluate measurements at some wavelengths. We find that the aerosol extinction coefficient measurements at 449, 520, 755, 869, and 1021 nm are reliable with accuracies and precisions on the order of 10% in the mission's primary aerosol target range of 15 to 25 km. We also believe this to be true of the aerosol measurements at 1545 nm though we cannot exclude some positive bias below 15 km. We recommend use of the 385 nm measurements above 16 km where the accuracy is on par with other aerosol channels. The 601 nm measurement is much noisier (∼20%) than other channels and we suggest caution in the use of these data. We believe that the 676 nm data are clearly defective particularly above 20 km (accuracy as poor as 50%) and the precision is also low (∼30%). We suggest excluding this channel under most circumstances. The SAGE III Version 4 water vapor data product appears to be high quality and is recommended for science applications in the stratosphere below 45 km. In this altitude range, the mean differences with all four corroborative data sets are no bigger than 15% and often less than 10% with exceptional agreement with POAM III and MLS. Above 45 km, it seems likely that SAGE III water vapor values are increasingly too large and should be used cautiously or avoided. We believe that SAGE III meets its preflight goal Correspondence to: L. W. Thomason (l.w.thomason@nasa.gov) of 15% accuracy and 10% precision between 15 and 45 km. SAGE III water vapor data does not appear to be affected by aerosol loading in the stratosphere.

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Section: Comparisons With Sage II and Poam Iiisupporting

confidence: 89%

An evaluation of the SAGE III version 4 aerosol extinction coefficient and water vapor data products

et al. 2010

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“…slope --0.465km/week. Thus, the average altitude of the clouds appear to descend at a rate of 0.77mm/sec (in agreement with the downward flux of air in the Arctic polar vortex determined in Kent et al, 1985). This apparent downward trend of PSC's and temperature was also observed in McCormick et al (1981).…”

Section: (C) Duration Prevalence and Location Of Psc'ssupporting

confidence: 87%

“…The downward motion of the clouds could be due to descending air inside the polar vortex, however, as described by Kent et al (1985) or if the particles are larger, a combination of sedimentation and downward mass flow. If we assume, for example, all of the available water substance is incorporated into the PSC particles, they can be as large as approximately 2*m radius (Hamill and McMaster, 1984).…”

Section: Inferred Microscopic Properties Of the Cloud Particlesmentioning

confidence: 99%

Characteristics of Polar Stratospheric Clouds as Observed by SAM II, SAGE, and Lidar

McCormick

Hamill

Farrukh³

1985

Journal of the Meteorological Society of Japan

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The discovery of polar stratospheric clouds (PSC's) in the Arctic and Antarctic stratosphere during winter is described, and the directly observed and implied properties of these clouds are discussed.It is proposed that the more familiar "mother-of-pearl" or "nacreous" clouds are a special subset of PSC's. The size, location, prevalence and temperature dependence of the clouds as measured by the SAM II and SAGE satellite systems are outlined. Airborne lidar measurements have recently demonstrated that the PSC phenomenon is most probably associated with an extended stratospheric cloud bank existing within the cold polar vortex region during the winter period with the PSC's bounded by a 188K temperature isotherm.The PSC's probably exist at a 50 percent frequency within the 193K isotherm. Using the observed information on the cloud extinction and change in location with time we consider possible formation mechanisms, the size of the cloud particles, and show the descending motion of the cloud during wintertime.

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“…In the past (ASAP, CCMI), the temporal window was simply expanded and interpolations 30 across gaps as large as 6 months were permitted. However, the winter poles are generally low (relative to mid latitudes) in aerosol (in the absence of PSCs) due to their isolation from mid-latitudes and the diabatic subsidence within the polar vortex (Kent et al, 1985). As a result, the polar vortex, particularly in the northern hemisphere where SAGE II sampling is strongly affected by temporal/spatial sampling, is poorly represented in these earlier data sets.…”

Section: Filling the Gaps: High Latitudesmentioning

confidence: 90%

A global, space-based stratospheric aerosol climatology: 1979 to 2016

Thomason¹,

Vernier²,

Bourassa³

et al. 2017

Preprint

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We describe the construction of a continuous 38-year record of stratospheric aerosol optical properties. The Global Space-based Stratospheric Aerosol Climatology, or GloSSAC, provided the input data to the 15 construction of the Climate Model Intercomparison Project stratospheric aerosol forcing data set (1979 to 2014) and we have extended it through 2016 following an identical process. GloSSAC focuses on the Stratospheric Aerosol and Gas Experiment (SAGE) series of instruments through mid-2005 and on the Optical Spectrograph and InfraRed Imager System (OSIRIS) and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data thereafter. We also use data from other space 20 instruments and from ground-based, air and balloon borne instruments to fill in key gaps in the data set. The end result is a global and gap-free data set focused on aerosol extinction coefficient at 525 and 1020 nm and other parameters on an 'as available' basis. For the primary data sets, we developed a new method for filling the post-Pinatubo eruption data gap for 1991 to 1993 based on data from the Cryogenic Limb Array Etalon Spectrometer. In addition, we developed a new method for populating wintertime high 25 latitudes during the SAGE period employing a latitude-equivalent latitude conversion process that greatly improves the depiction of aerosol at high latitudes compared to earlier similar efforts. We report data in the troposphere only when and where it is available. This is primarily during the SAGE II period except the most enhanced part of the Pinatubo period. It is likely that the upper troposphere during Pinatubo was greatly enhanced over non-volcanic periods and that domain remains substantially under characterized. 30We note that aerosol levels during the OSIRIS/CALIPSO period in the lower stratosphere at mid and high latitudes is routinely higher than what we observed during the SAGE II period. While this period had nearly continuous low-level volcanic activity, it is possible that the enhancement in part reflects deficiencies in the data set. We also expended substantial effort to quality assess the data set and the product is by far the best we have produced. GloSSAC version 1.0 is available in netCDF format at the NASA Atmospheric 35 Data Center at https://eosweb.larc.nasa.gov/. GloSSAC users should cite this paper and the data set DOI

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Variation in the Stratospheric Aerosol Associated with the North Cyclonic Polar Vortex as Measured by the SAM II Satellite Sensor

Cited by 71 publications

References 0 publications

An evaluation of the SAGE III version 4 aerosol extinction coefficient and water vapor data products

An evaluation of the SAGE III version 4 aerosol extinction coefficient and water vapor data products

Characteristics of Polar Stratospheric Clouds as Observed by SAM II, SAGE, and Lidar

A global, space-based stratospheric aerosol climatology: 1979 to 2016

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