scholarly journals Ship-based aerosol optical depth measurements in the Atlantic Ocean: Comparison with satellite retrievals and GOCART model

2006 ◽  
Vol 33 (14) ◽  
Author(s):  
A. Smirnov ◽  
B. N. Holben ◽  
S. M. Sakerin ◽  
D. M. Kabanov ◽  
I. Slutsker ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Retrievals ◽  
Gocart Model

scholarly journals Intercomparison of satellite retrieved aerosol optical depth over ocean during the period September 1997 to December 2000

2004 ◽  
Vol 4 (6) ◽  
pp. 8201-8244 ◽  
Author(s):  
G. Myhre ◽  
F. Stordal ◽  
M. Johnsrud ◽  
D. J. Diner ◽  
I. V. Geogdzhayev ◽  
...  
Keyword(s):  
Spatial Correlation ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Entire Period ◽  
Coastal Regions ◽  
Satellite Retrievals ◽  
Field Campaigns ◽  
Good Agreement ◽  
Satellite Instruments

Abstract. Monthly mean aerosol optical depth (AOD) over ocean is compared from a total of 9 aerosol retrievals during a 40 months period. Comparisons of AOD have been made both for the entire period and sub periods. We identify regions where there is large disagreement and good agreement between the aerosol satellite retrievals. Significant differences in AOD have been identified in most of the oceanic regions. Several analyses are performed including spatial correlation between the retrievals as well as comparison with AERONET data. During the 40 months period studied there have been several major aerosol field campaigns as well as events of high aerosol content. It is studied how the aerosol retrievals compare during such circumstances. The differences found in this study are larger than found in a previous study where 5 aerosol retrievals over an 8 months period were compared. However, results in coastal regions are promising especially for aerosol retrievals from satellite instruments dedicated for aerosol research. In depth analyses explaining the differences between AOD obtained in different retrievals are clearly needed. We limit this study to identify differences and similarities and indicate possible sources that affect the quality of the retrievals. This is a necessary first step towards understanding the differences and improving the retrievals.

scholarly journals Annual cycle of global distributions of aerosol optical depth from integration of MODIS retrievals and GOCART model simulations

2003 ◽  
Vol 108 (D3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Hongbin Yu ◽  
R. E. Dickinson ◽  
M. Chin ◽  
Y. J. Kaufman ◽  
B. N. Holben ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Annual Cycle ◽  
Model Simulations ◽  
Gocart Model

scholarly journals Relationship between low-cloud presence and the amount of overlying aerosols

2016 ◽  
Author(s):  
Chul E. Chung ◽  
Anna Lewinschal ◽  
Eric Wilcox
Keyword(s):  
Pacific Ocean ◽  
Atlantic Ocean ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Observations ◽  
Wide Spread ◽  
Clear Sky ◽  
Northeastern Pacific ◽  
Low Cloud ◽  
Southeastern Atlantic

Abstract. Aerosols are often advected above cloud decks, and the amount of aerosols over cloud has been assumed to be similar to those at the same heights in nearby clear sky. In this assumption, cloud and aerosol above cloud top height are considered randomly located with respect to each other. The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are analyzed here to investigate this assumption on global scales. The CALIPSO data reveal that the aerosol optical depth (AOD) above low cloud tends to be smaller than in nearby clear sky during the daytime and the opposite is true during the nighttime. In particular, over oceanic regions with wide-spread low cloud, such as the tropical southeastern Atlantic Ocean and northeastern Pacific Ocean, the daytime AOD above low cloud is often 40 % smaller than in surrounding clear skies.

scholarly journals Some implications of sampling choices on comparisons between satellite and model aerosol optical depth fields

2010 ◽  
Vol 10 (7) ◽  
pp. 17789-17814
Author(s):  
A. M. Sayer ◽  
G. E. Thomas ◽  
P. I. Palmer ◽  
R. G. Grainger
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Grid Cell ◽  
Point Sources ◽  
Clear Sky ◽  
Model Aerosol ◽  
Satellite Retrievals ◽  
Along Track ◽  
The Impact

Abstract. The comparison of satellite and model aerosol optical depth (AOD) fields provides useful information on the strengths and weaknesses of both. However, the sampling of satellite and models is very different and some subjective decisions about data selection and aggregation must be made in order to perform such comparisons. This work examines some implications of these decisions, using GlobAerosol AOD retrievals at 550 nm from Advanced Along-Track Scanning Radiometer (AATSR) measurements, and aerosol fields from the GEOS-Chem chemistry transport model. It is recommended to sample the model only where the satellite flies over on a particular day; neglecting this can cause regional differences in model AOD of up to 0.1 on monthly and annual timescales. The comparison is observed to depend strongly upon thresholds for sparsity of satellite retrievals in the model grid cells. Requiring at least 25% coverage of the model grid cell by satellite data decreases the observed difference between the two by approximately half over land. The impact over ocean is smaller. In both model and satellite datasets, there is an anticorrelation between the proportion p of a model grid cell covered by satellite retrievals and the AOD. This is attributed to small p typically occuring due to high cloud cover and lower AODs being found in large clear-sky regions. Daily median AATSR AODs were found to be closer to GEOS-Chem AODs than daily means (with the root mean squared difference being approximately 0.05 smaller). This is due to the decreased sensitivity of medians to outliers such as cloud-contaminated retrievals, or aerosol point sources not included in the model.

scholarly journals Intercomparison of satellite retrieved aerosol optical depth over ocean during the period September 1997 to December 2000

2005 ◽  
Vol 5 (6) ◽  
pp. 1697-1719 ◽  
Author(s):  
G. Myhre ◽  
F. Stordal ◽  
M. Johnsrud ◽  
D. J. Diner ◽  
I. V. Geogdzhayev ◽  
...  
Keyword(s):  
Spatial Correlation ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Entire Period ◽  
Coastal Regions ◽  
Satellite Retrievals ◽  
Field Campaigns ◽  
Good Agreement ◽  
Satellite Instruments

Abstract. Monthly mean aerosol optical depth (AOD) over ocean is compared from a total of 9 aerosol retrievals during a 40 months period. Comparisons of AOD have been made both for the entire period and sub periods. We identify regions where there is large disagreement and good agreement between the aerosol satellite retrievals. Significant differences in AOD have been identified in most of the oceanic regions. Several analyses are performed including spatial correlation between the retrievals as well as comparison with AERONET data. During the 40 months period studied there have been several major aerosol field campaigns as well as events of high aerosol content. It is studied how the aerosol retrievals compare during such circumstances. The differences found in this study are larger than found in a previous study where 5 aerosol retrievals over an 8 months period were compared. Part of the differences can be explained by limitations and deficiencies in some of the aerosol retrievals. In particular, results in coastal regions are promising especially for aerosol retrievals from satellite instruments particularly suited for aerosol research. In depth analyses explaining the differences between AOD obtained in different retrievals are clearly needed. We limit this study to identifying differences and similarities and indicating possible sources that affect the quality of the retrievals. This is a necessary first step towards understanding the differences and improving the retrievals.

scholarly journals AERONET-based microphysical and optical properties of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

2013 ◽  
Vol 13 (9) ◽  
pp. 25013-25065 ◽  
Author(s):  
A. M. Sayer ◽  
N. C. Hsu ◽  
T. F. Eck ◽  
A. Smirnov ◽  
B. N. Holben
Keyword(s):  
Optical Properties ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Biomass Burning ◽  
Source Regions ◽  
Satellite Retrievals ◽  
Retrieval Algorithms ◽  
Aerosol Particle Size ◽  
Fine Mode ◽  
Single Scatter

Abstract. Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad ''families'' of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA ∼0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA ∼0.88–0.9 in the midvisible). The strongest absorption is seen in southern African savannah at Mongu (Zambia), with average SSA ∼0.85 in the midvisible. These can serve as candidate sets of aerosol microphysical/optical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

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