Problems in separating aerosol and cloud in the Stratospheric Aerosol and Gas Experiment (SAGE) II data set under conditions of lofted dust: Application to the Asian deserts

Kent, G. S.; Trepte, Charles R.; Wang, P.‐H.; Lucker, Patricia L.

doi:10.1029/2002jd002412

Cited by 13 publications

(10 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Conversely, during low aerosol loading periods it is challenging to extricate the aerosol signature at infrared wavelengths because the signal is dominated by absorption of gaseous species [ Thomason , ]. Identifying the presence of clouds in all these observations is often difficult or ambiguous [ Kent et al , ].…”

Section: Measurements Of Stratospheric Aerosolmentioning

confidence: 99%

Stratospheric aerosol-Observations, processes, and impact on climate

et al. 2016

View full text Add to dashboard Cite

Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes.

show abstract

Section: Measurements Of Stratospheric Aerosolmentioning

confidence: 99%

Stratospheric aerosol-Observations, processes, and impact on climate

et al. 2016

View full text Add to dashboard Cite

show abstract

“…A global climatology of stratospheric aerosol radiative properties has been compiled from SAGE II multiwavelength extinction measurements [ Thomason et al , 1997]. Although SAGE II was initially designed for detecting stratospheric aerosols, its 1.02 μ m aerosol extinction coefficient profiles have actually been retrieved reaching down to the boundary layer [ Wang et al , 1999; Thomason and Taha , 2003; Kent et al , 2003]. Sufficient tropospheric data have been accumulated under cloudless conditions after long observation period.…”

Section: Model and Datamentioning

confidence: 99%

Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

Zhu¹,

Ramanathan²,

Li³

et al. 2007

J. Geophys. Res.

188

141

View full text Add to dashboard Cite

[1] Multiple satellite data sets in conjunction with the Monte Carlo Aerosol-CloudRadiation (MACR) model are employed to determine climatological distributions and radiative impacts of dust plumes over the Pacific, Indian, and Atlantic oceans. Three target regions, namely the Yellow Sea (YS), Arabian Sea (AS), and Saharan Coast (SC), are examined for quantitative comparisons of dust properties and their impacts on climate. Twenty year averaged Advanced Very High Resolution Radiometer (AVHRR) aerosol optical depth (AOD) data clearly show the peak dust season for the three target regions, March-April-May for YS and June-July-August for AS and SC. Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) modeled dust AOD fraction and Moderate Imaging Spectroradiometer (MODIS) large-mode AOD ratio are adopted to evaluate the dust fraction estimate. Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction coefficient data are used to define the vertical distribution of dust. The elevated dust plumes are detected by subtracting the non-dust-season values from dust season values of SAGE II data, showing extinction peak around $4 km over AS and SC. Over YS, dust plumes are found presenting multilayered structure. The shortwave (SW) forcing of dust, although moderated by the longwave (LW) effect, dominates the net effects (SW + LW) of dust plumes. Under clear-sky (i.e., cloudless) conditions, dust plumes reduce about 5.9 W m À2 , 17.8 W m À2 , and 14.2 W m À2 regional and seasonal mean radiative flux reaching the surface over YS, AS, and SC, respectively. Of the three regions, dust plumes over AS have the largest effect on atmospheric heating owing to a lower single-scattering albedo and the relatively large dust loading. The maximum SW heating occurs over AS with the value around +0.5 K/day inside the dust layer at $4 km. The LW effect results in strong cooling throughout the dust layer and moderate heating below the dust layer, and dust plumes over SC exert the maximum LW effect on heating rates, with up to À0.5 K/day LW cooling in the free troposphere and about +0.3 K/day warming in the boundary layer. As the sum of the SW and the LW heating rates, net heating rate shows a more complex pattern. Over SC, large LW cooling inside the dust layer offsets up to 80% SW heating and results in about À0.1 K/day net heating rate change at the height $5 km over SC. Over AS the net heating rate change is dominated by SW heating because the maximum LW cooling is less than 60% of the SW heating, which leads to +0.3 K/day net heating inside the dust layer and moderate heating below the dust base. The net heating rate change over YS is the smallest among the three regions, with magnitude within 0.1 K/day.

show abstract

“…We also exclude any observations in which we infer the presence of non-opaque clouds. We identify these clouds using the method described by Thomason and Vernier (2013) (a revision of an algorithm 25 developed by Kent et al (2003)) and exclude those points from the analysis. We infer cloud presence almost exclusively in the troposphere; however, we occasionally infer the presence of clouds in the lower tropical stratosphere.…”

Section: The Sage II Era Data Set (October 1984 To August 2005)mentioning

confidence: 99%

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

Thomason¹,

Vernier²,

Bourassa³

et al. 2017

Preprint

View full text Add to dashboard Cite

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

show abstract

Problems in separating aerosol and cloud in the Stratospheric Aerosol and Gas Experiment (SAGE) II data set under conditions of lofted dust: Application to the Asian deserts

Cited by 13 publications

References 18 publications

Stratospheric aerosol-Observations, processes, and impact on climate

Stratospheric aerosol-Observations, processes, and impact on climate

Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

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

Contact Info

Product

Resources

About