scholarly journals Contribution of sea-salt to aerosol optical depth over the Arabian Sea derived from MODIS observations

2006 ◽  
Vol 33 (3) ◽  
Author(s):  
S. K. Satheesh ◽  
J. Srinivasan ◽  
K. Krishna Moorthy
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Arabian Sea ◽  
Sea Salt

scholarly journals Modelling of nitrate and ammonium-containing aerosols in presence of sea salt

2006 ◽  
Vol 6 (12) ◽  
pp. 4809-4821 ◽  
Author(s):  
G. Myhre ◽  
A. Grini ◽  
S. Metzger
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Transport Model ◽  
Meteorological Condition ◽  
Global Scale ◽  
Sea Salt ◽  
Aerosol Composition ◽  
Fine Mode ◽  
High Concentrations

Abstract. A thermodynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on nitrate partitioning to the aerosol phase and if particulate nitrate is expected to form in fine or coarse mode aerosols. Modelling of the formation of fine mode nitrate particles is complicated since it depends on other aerosol components and aerosol precursors as well as meteorological condition. The surface concentrations from the model are compared to observed surface concentrations at around 20 sites around Europe for nitrate and ammonium. The agreement for nitrate is good but the modelled values are somewhat underestimated compared to observations at high concentrations, whereas for ammonium the agreement is very good. However, we underscore that such a comparison is not of large importance for the aerosol optical depth of particulate nitrate since the vertical profile of aerosol components and their precursors are so important. Fine mode nitrate formation depends on vertical profiles of both ammonia/ammonium and sulphate. The model results show that fine mode particulate nitrate play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of fine mode nitrate is relatively small due to limited availability of ammonia and loss to larger sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of fine mode nitrate by 25% on a global scale but with large regional variations.

scholarly journals Relationship between wind speed and aerosol optical depth over remote ocean

2010 ◽  
Vol 10 (13) ◽  
pp. 5943-5950 ◽  
Author(s):  
H. Huang ◽  
G. E. Thomas ◽  
R. G. Grainger
Keyword(s):  
Wind Speed ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Observation ◽  
Sea Salt ◽  
High Wind Speed ◽  
Sea Salt Aerosol ◽  
Linear Relationships ◽  
Speed Range ◽  
Highly Correlated

Abstract. The effect of wind speed on aerosol optical depth (AOD) at 0.55 μm over remote ocean regions is investigated. Remote ocean regions are defined by the combination of AOD from satellite observation and wind direction from ECMWF. According to our definition, many ocean regions cannot be taken as remote ocean regions due to long-range transportation of aerosol from continents. Highly correlated linear relationships are found in remote ocean regions with a wind speed range of 0–20 ms−1. The enhancement of AOD at high wind speed is explained as the increase of sea salt aerosol production.

scholarly journals Validation of MODIS derived aerosol optical depth and an investigation on aerosol transport over the South East Arabian Sea during ARMEX-II

2009 ◽  
Vol 27 (6) ◽  
pp. 2285-2296 ◽  
Author(s):  
M. Aloysius ◽  
M. Mohan ◽  
S. Suresh Babu ◽  
K. Parameswaran ◽  
K. Krishna Moorthy
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mass Concentration ◽  
Arabian Sea ◽  
Second Phase ◽  
The South ◽  
Monsoon Period ◽  
Lower Altitude ◽  
The North ◽  
Coarse Mode

Abstract. The influence of wind and humidity on aerosol optical depth (AOD) over the Arabian sea is being investigated using MODIS (Moderate Resolution Imaging Spectroradiometer) Level 3 (Collection-5) and NCEP (National Centres for Environmental Prediction) reanalysis data for the second phase of the Arabian Sea Monsoon Experiment (ARMEX-II) over the South East Arabian Sea (SEAS) in the pre-monsoon period (14 March–10 April 2003). In order to qualify MODIS data for this study, MODIS aerosol parameters were first compared with ship borne Microtops measurements. This showed correlations 0.96–0.97 in the case of spectral AODs and a correlation 0.72 for the angstrom exponents. The daily AOD data from MODIS and winds from NCEP reveal that the ship observed episodic enhancement and decay of AOD at the TSL (Time Series Location) during 23 March–6 April 2003 was caused by the southward drift of an aerosol pocket driven by an intensification and reduction of surface pressure in the North Western Arabian Sea with a low altitude convergence prevailing over SEAS. The AOD increase coincided with a decrease in the Angstrom exponent and the fine mode fraction suggesting the pocket being dominated by coarse mode particles. A partial correlation analysis reveals that the lower altitude wind convergence is the most influential atmospheric variable in modulating AOD over the ARMEX-II domain during the TSL period. However, surface winds at a distant zone in the north/north west upwind direction also had a moderate influence, though with a lag of two days. But this effect was minor since the winds were not strong enough to produce marine aerosols matching with the high AODs over the ARMEX-II domain. These findings and the similarity between MODIS column mass concentration and the ship borne QCM (Quartz Crystal Microbalance) measured coarse mode mass concentration, suggest that the aerosol pocket was mostly composed of coarse mode mineral dust in the lower atmospheric altitudes transported from the Arabian deserts.

scholarly journals The European aerosol budget in 2006

2010 ◽  
Vol 10 (9) ◽  
pp. 21391-21437 ◽  
Author(s):  
J. M. J. Aan de Brugh ◽  
M. Schaap ◽  
E. Vignati ◽  
F. Dentener ◽  
M. Kahnert ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Ground Level ◽  
Sea Salt ◽  
Optical Measurements ◽  
Aerosol Size Distribution ◽  
Anthropogenic Aerosols ◽  
Removal Rates ◽  
Wet Removal

Abstract. This paper presents the aerosol budget over Europe in 2006 calculated with the global transport model TM5 coupled to the size-resolved aerosol module M7. Comparison with ground observations indicates that the model reproduces the observed concentrations quite well with an expected slight underestimation of PM10 due to missing emissions (e.g. resuspension). We observe that a little less than half of the anthropogenic aerosols emitted in Europe are exported and the rest is removed by deposition. The anthropogenic aerosols are removed mostly by rain (95%) and only 5% is removed by dry deposition. For the larger natural aerosols, especially sea salt, a larger fraction is removed by dry processes (sea salt: 70%, mineral dust: 35%). We observe transport of aerosols in the jet stream in the higher atmosphere and an import of Sahara dust from the south at high altitudes. Comparison with optical measurements shows that the model reproduces the Ångström parameter very well, which indicates a correct simulation of the aerosol size distribution. However, we observe an underestimation of the aerosol optical depth. Because the surface concentrations are close to the observations, the shortage of aerosol in the model is probably at higher altitudes. We show that the discrepancies are mainly caused by an overestimation of wet-removal rates. To match the observations, the wet-removal rates have to be scaled down by a factor of about 5. In that case the modelled ground-level concentrations of sulphate and sea salt increase by 50% (which deteriorates the match), while other components stay roughly the same. Finally, it is shown that in particular events, improved fire emission estimates may significantly improve the ability of the model to simulate the aerosol optical depth. We stress that discrepancies in aerosol models can be adequately analysed if all models would provide (regional) aerosol budgets, as presented in the current study.

scholarly journals Aerosol Optical Depth of the Main Aerosol Species over Italian Cities Based on the NASA/MERRA-2 Model Reanalysis

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 709 ◽  
Author(s):  
Umberto Rizza ◽  
Enrico Mancinelli ◽  
Mauro Morichetti ◽  
Giorgio Passerini ◽  
Simone Virgili
Keyword(s):  
Air Quality ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Urban Air Pollution ◽  
Sea Salt ◽  
Anthropogenic Aerosols ◽  
National Scale ◽  
Global Coverage ◽  
Modern Era

The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) provides data at 0.5° × 0.625° resolution covering a period from 1 January 1980 to the present. Natural and anthropogenic aerosols are simulated in MERRA-2, considering the Goddard chemistry, aerosol, radiation, and transport model. This model simulates the sources, sinks, and chemistry of mixed aerosol tracers: dust, sea salt, hydrophobic and hydrophilic black carbon and organic carbon, and sulfate. MERRA-2 aerosol reanalysis is a pioneering tool for investigating air quality issues, noteworthy for its global coverage and its distinction of aerosol speciation expressed in the form of aerosol optical depth (AOD). The aim of this work was to use the MERRA-2 reanalysis to study urban air pollution at a national scale by analyzing the AOD. AOD trends were evaluated for a 30-year period (1987–2017) over five Italian cities (Milan, Rome, Cagliari, Taranto, and Palermo) in order to investigate the impacts of urbanization, industrialization, air quality regulations, and regional transport on urban aerosol load. AOD evolution predicted by the MERRA-2 model in the period 2002–2017 showed a generalized decreasing trend over the selected cities. The anthropogenic signature on total AOD was between 50% and 80%, with the largest contribution deriving from sulfate.

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