Impact of Breaking Waves on Sea Salt Production and Local Change of Aerosol Optical Properties

Variability of trends observed in Atmospheric Aerosol optical properties over Pune, India

10.5194/egusphere-egu2020-21180 ◽

2020 ◽

Author(s):

Sudeep Das ◽

Govindan Pandithurai

Keyword(s):

Optical Properties ◽

Air Quality ◽

Role Model ◽

Anthropogenic Activities ◽

Sea Salt ◽

Negative Slope ◽

Average Height ◽

Aerosol Optical Properties ◽

The City ◽

Monthly Variations

Long term trends of various aerosol optical properties are observed over the city of Pune, the ninth most populated city in India using ground and satellite based instruments such as AERONET, MODIS (Aqua and Terra), MISR, CALIOP and reanalysis tool MERRA. Annually, the Aerosol Optical Depth is observed to be increasing over all the types of instruments (2004-17) with values of 0.01 to 0.006 yr-1, whereas the Angstrom exponent has a negative slope (AERONET) which suggests that the fine aerosols are decreasing. Single scattering albedo (SSA) is also increasing (0.00657 yr-1), which means the emission of smaller darker particles like soot has decreased over the years. MISR shows that the Absorbing AOD trend is decreasing in the overall study period (-0.0001237 yr-1). All these annual trends are related to anthropogenic activities and show differing trends before and after 2008, the year when various pollution counter measures were introduced mainly in Pune and also in various nearby areas. After 2008, the AOD increasing slope reduces, and the AAOD reverses the trend from positive to a negative slope. The average height till various kinds of aerosols reach and their vertical profile is studied using CALIOP data. Monthly variations of AOD and their vertical distribution also observed and discussed. Aerosol characterization is done using the MERRA tool into dust, sea salt, sulfates, elementary carbon, and organic carbon. Their monthly variations are explained by source characterizations using the HySplit model. In summer, air from the Arabian sea brings in dust and sea salt into the city and in winter, aerosols come from central India dominantly as carbon and sulfates changing the air quality over there. This study lays its stress on the fact that even though aerosols cover over a city is mostly non-local, anthropogenic activities of that area do play a significant role and here the city of Pune is a role model to show how measures can be taken to improve air quality over any urban area.

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Deriving the effect of wind speed on clean maritime aerosol optical properties using the A-Train satellites

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-4599-2011 ◽

2011 ◽

Vol 11 (2) ◽

pp. 4599-4630 ◽

Cited By ~ 4

Author(s):

V. P. Kiliyanpilakkil ◽

N. Meskhidze

Keyword(s):

Optical Properties ◽

Wind Speed ◽

Surface Wind ◽

Surface Wind Speed ◽

Sea Salt ◽

Marine Aerosol ◽

Marine Aerosols ◽

Aerosol Optical Properties ◽

The Mean ◽

532 Nm

Abstract. Relationship between "clean marine" aerosol optical properties and ocean surface wind speed is explored using remotely sensed data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the CALIPSO satellite and the Advanced Microwave Scanning Radiometer (AMSR-E) on board the AQUA satellite. Detailed data analyses are carried out over 15 regions selected to be representative of different areas of the global ocean for the time period from June 2006 to June 2010. Based on remotely sensed optical properties the CALIPSO algorithm is capable of discriminating "clean marine" aerosols from other types often present over the ocean (such as urban/industrial pollution, desert dust and biomass burning). The global mean optical depth of "clean marine" aerosol at 532 nm (AOD532) is found to be 0.052 ± 0.038. The mean layer integrated volume depolarization ratio of marine aerosols is 0.016 ± 0.012, the value representative of sea salt crystals. Integrated attenuated backscatter and color ratio of marine aerosols at 532 nm were obtained to be 0.003 ± 0.002 sr−1 and 0.530 ± 0.149, respectively. A logistic regression between AOD532 and 10-meter surface wind speed (U10) revealed three distinct regions. For surface winds lower than 4 m s−1, the mean CALIPSO-derived AOD532 is found to be 0.02 ± 0.003 with little dependency on the surface wind speed. For surface winds from 4 m s−1 to 12 m s−1, representing the dominant fraction of all available data, marine aerosol optical depth is linearly correlated with the U10, with a slope of 0.0062 s m−1. In this intermediate wind speed region, the AOD532 vs. U10 regression derived here is comparable to previously reported relationships. At very high wind speed values (U10 > 18 m s−1), the AOD532-wind speed relationship showed a tendency toward leveling off, suggesting the existence of some maximum value for maritime AOD. Results of our calculations suggest that considerable improvements to both optical properties of marine aerosols and their production mechanisms can be achieved by discriminating "clean marine" aerosols (or sea salt particles) from all other types of aerosols present over the ocean.

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