Advertisement

Boundary-Layer Meteorology

, Volume 170, Issue 1, pp 161–181 | Cite as

Influence of Relative Humidity, Mixed-Layer Height, and Mesoscale Vertical-Velocity Variations on Column and Surface Aerosol Characteristics Over an Urban Region

  • S. RamachandranEmail author
  • T. A. Rajesh
  • Sumita Kedia
Research Article
  • 217 Downloads

Abstract

Investigations into the influence of variations in relative humidity, mixed-layer height, and mesoscale vertical velocity on column and surface aerosol characteristics over urban regions are quite rare. Here we report on a comprehensive investigation that was conducted over Ahmedabad, an urban location in western India, during December 2006. In this campaign columnar and surface aerosol characteristics were measured and compared to relative humidity, mixed-layer height, and mesoscale vertical velocity to examine their influence on urban aerosol characteristics. The 500-nm aerosol optical depth was found to be approximately 0.8 between 24 and 26 December while on a cleaner day such as 7 and 18 December the aerosol optical depth was 0.1. Aerosol optical depths based on Moderate Resolution Imaging Spectroradiometer (MODIS) level-2 and level-3 data, and on in situ Sun photometer measurements, show good agreement. The scattering coefficient (\(\beta _{\mathrm{sca}}\)) and absorption coefficient (\(\beta _{\mathrm{abs}}\)) increased by a factor of 5–10 on 26 December compared to 7 December (a normal day). This latter date was characterized by a clear atmosphere, a lower mixed-layer height (\(\approx \)1650 m), positive vertical velocity and higher aerosol scale height (>3 km), while 26 December was marked with hazy and smoky conditions, a larger mixed-layer height (\(\approx \)2500 m), negative vertical velocity and smaller aerosol scale height (\(\approx \)1 km). These atmospheric conditions lead to lower and higher values of surface and columnar aerosol concentrations on 7 and 26 December respectively. A measure of spectral aerosol absorption, \(\alpha '_{\mathrm{abs}}\) > 2, indicating the dominance of carbonaceous aerosols from biomass/biofuel emissions (open biomass burning), is rather surprising as fossil-fuel emissions that produce strongly light absorbing carbonaceous particles usually dominate urban regions. The single-scattering albedo on both days is 0.56 and 0.67 respectively, while monthly mean hemispheric backscatter fraction b and asymmetry parameter g values are 0.16 and 0.53 respectively. Higher b and lower g values on 7 December, and lower b and higher g values on 26 December, provide the relative scale of variation in the amount of sub-micron aerosols that dominate on a normal/clear day vis-à-vis a smoky/perturbed day. Lower single-scattering albedo indicates the dominance of absorbing aerosols above Ahmedabad, and higher b and lower g values suggest the abundance of fine mode particles in aerosol size distribution. The in-depth results serve as representative inputs to modelling the column and surface characteristics, and the resultant radiative forcing of urban aerosols influenced by variations in relative humidity, mixed-layer height, and mesoscale vertical velocity.

Keywords

Aerosol Dynamics Boundary-layer height Scale height Urban 

Notes

Acknowledgements

We thank ISRO-GBP, ISRO Headquarters, Bengaluru for partial funding support. Daily mean temperature and wind speed data are obtained from NOAA, NESDIS National Climatic Data Center, USA. Diurnal relative humidity data over Ahmedabad are downloaded from http://www.wunderground.com. MODIS level-3 aerosol optical depths are downloaded using NASA Goddard Earth Sciences Data and Information Services Center’s Interactive Online Visualization and Analysis Infrastructure. MODIS level-2 aerosol optical depth data are acquired from LAADS-DAAC located in the GSFC (https://ladsweb.nascom.nasa.gov). Vertical velocity for December 2006 was obtained from the NOAA-ESRL Physical Sciences Division, Boulder, Colorado from their web site at http://www.cdc.noaa.gov/. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and READY website (http://www.ready.noaa.gov) used in this publication.

References

  1. Anderson TL, Ogren JA (1998) Determining aerosol radiative properties using the TSI 3563 integrating nephelometer. Aerosol Sci Technol 29:57–69CrossRefGoogle Scholar
  2. Anderson TL, Covert DS, Marshall SF, Laucks ML, Charlson RJ, Waggoner AP, Ogren JA, Caldow R, Holm RJ, Quant FR, Sem GJ, Wiedensohler A, Ahlquist NA, Bates TS (1996) Performance characteristics of a high-sensitivity, three-wavelength total scatter/backscatter nephelometer. J Atmos Ocean Technol 13:967–986CrossRefGoogle Scholar
  3. Andrews E, Sheridan PJ, Fiebig M, McComiskey A, Ogren JA, Arnott P, Covert D, Elleman R, Gaspirini R, Collins D, Jonsson H, Schmid B, Wang J (2006) Comparison of methods for deriving aerosol asymmetry parameter. J Geophys Res 111:D5CrossRefGoogle Scholar
  4. Bapna M, Sunder Raman R, Ramachandran S, Rajesh TA (2013) Airborne black carbon concentrations over an urban region in western India—temporal variability, effects of meteorology, and source regions. Environ Sci Pollut Res 20:1617–1631CrossRefGoogle Scholar
  5. Bodhaine BA (1995) Aerosol absorption measurements at Barrow, Mauna Loa and the south pole. J Geophys Res 100:8967–8975CrossRefGoogle Scholar
  6. Charlson RJ, Covert DS, Larson TV (1984) Observation of the effect of relative humidity on light scattering by aerosols. In: Ruhnke LH, Deepak A (eds) Hygroscopic aerosols. Deepak Publishing, Hampton, pp 35–44Google Scholar
  7. Clarke AD, Howell S, Quinn PK, Bates TS, Ogren JA, Andrews E, Jefferson A, Massling A, Mayol-Bracero O, Maring H, Savoie D, Cass G (2002) INDOEX aerosol: a comparison and summary of chemical, microphysical, and optical properties observed from land, ship, and aircraft. J Geophys Res 107:8033CrossRefGoogle Scholar
  8. Draxler R, Hess GD (1998) An overview of the HYSPLIT-4 modeling system for trajectories, dispersion and deposition. Aust Meteorol Mag 47:295–308Google Scholar
  9. Hegg DA, Covert DS, Rood MJ, Hobbs PV (1996) Measurements of aerosol optical properties in marine air. J Geophys Res 101:12893–12903CrossRefGoogle Scholar
  10. Hess M, Koepke P, Schult I (1998) Optical properties of aerosols and clouds: the software package OPAC. Bull Am Meteorol Soc 79:831–844CrossRefGoogle Scholar
  11. Kalnay E, Kanamitsu M, Kistler R, Collins W, Deaven D, Gandin L, Iredell M, Saha S, White G, Woollen J, Zhu Y, Chelliah M, Ebisuzaki W, Higgins W, Janowiak J, Mo KC, Ropelewski C, Wang J, Leetmaa A, Reynolds R, Jenne R, Joseph D (1996) The NCEP/NCAR 40-year reanalysis project. Bull Amer Meteorol Soc 77:437–471CrossRefGoogle Scholar
  12. Kedia S, Ramachandran S (2011) Seasonal variations in aerosol characteristics over an urban location and a remote site in western India. Atmos Environ 45:2120–2128CrossRefGoogle Scholar
  13. Kirchstetter TW, Novakov T, Hobbs PV (2004) Evidence that the spectral dependence of light absorption by aerosols is affected by organic carbon. J Geophys Res 109:D21208CrossRefGoogle Scholar
  14. Kotchenruther RA, Hobbs PV (1998) Humidification factors of aerosols from biomass burning in Brazil. J Geophys Res 103:32081–32089CrossRefGoogle Scholar
  15. Pasricha PK, Gera BS, Shastri S, Maini HK, Ghosh AB, Tiwari MK, Garg SC (2003) Role of the water vapor greenhouse effect in the forecasting of fog occurrence. Boundary Layer Meteorol 107:469–482CrossRefGoogle Scholar
  16. Ramachandran S, Kedia S (2010) Black carbon aerosols over an urban region: radiative forcing and climate impact. J Geophys Res Atmos 115:D10CrossRefGoogle Scholar
  17. Ramachandran S, Kedia S (2011) Aerosol radiative effects over an urban location and a remote site in western India: seasonal variability. Atmos Environ 45:7415–7422CrossRefGoogle Scholar
  18. Ramachandran S, Rajesh TA (2007) Black carbon aerosol mass concentrations over Ahmedabad, an urban location in western India: comparison with urban sites in Asia, Europe, Canada and USA. J Geophys Res 112:D06211Google Scholar
  19. Ramachandran S, Rengarajan R, Jayaraman A, Sarin MM, Das SK (2006) Aerosol radiative forcing during clear, hazy and foggy conditions over a continental polluted location in north India. J Geophys Res 111:D20214CrossRefGoogle Scholar
  20. Remer LA, Kleidman RG, Levy RC, Kaufman YJ, Tanré D, Mattoo S, Martins V, Ichoku C, Koren I, Yu H, Holben BN (2008) Global aerosol climatology from the MODIS satellite sensors. J Geophys Res 113:D14S07CrossRefGoogle Scholar
  21. Sheridan PJ, Delene DJ, Ogren JA (2001) Four years of continuous surface aerosol measurements from the Department of Energy’s Atmospheric Radiation Measurement Program Southern Great Plains Cloud and Radiation Testbed site. J Geophys Res 106:20735–20747CrossRefGoogle Scholar
  22. Stull RB (1988) An introduction to boundary layer meteorology. Kluwer, DordrechtCrossRefGoogle Scholar
  23. Wiscombe WJ, Grams G (1976) The backscattered fraction in two-stream approximations. J Atmos Sci 33:2440–2451CrossRefGoogle Scholar

Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  1. 1.Space and Atmospheric Sciences DivisionPhysical Research LaboratoryAhmedabadIndia
  2. 2.Centre for Development of Advanced ComputingPuneIndia

Personalised recommendations