Tropospheric aerosol observations in São Paulo, Brazil using a compact lidar system

A backscattering light detection and ranging (lidar) system, the first of this kind in the country, has been set up in a suburban area in the city of São Paulo, Brazil (23°33′ S, 46°44′ W) to provide the vertical profile of the aerosol backscatter and extinction coefficients at 532 nm and up to 4–5 km height above sea level (asl). The measurements have been carried out during the second half of the so‐called Brazilian dry season, September and October in the year of 2001. When possible, the lidar measurements were complemented with aerosol optical thickness measurements obtained by a CIMEL Sun‐tracking photometer in the visible spectral region, not only to validate the lidar data, but also to provide an input value of the so‐called extinction‐to‐backscatter ratio (lidar ratio). The lidar data were also used to retrieve the Planetary Boundary Layer (PBL) height and low troposphere structural features over the city of São Paulo. Three‐dimensional air mass back trajectory analysis was also conducted to determine the source regions of aerosols observed during this study. These first lidar measurements over the city of São Paulo during the second half of the dry season showed a significant variability of the aerosol optical thickness (AOT) in the lower troposphere (0.5–5 km) at 532 nm. It was also found that the aerosol load is maximized in the 1–3 km height region and this load represents about 20–25% of the lower tropospheric aerosol.

[1]  S. H. Melfi,et al.  Lidar observations of vertically organized convection in the planetary boundary layer over the ocean , 1985 .

[2]  L. Lyons,et al.  Predictions of substorms following northward turnings of the interplanetary magnetic field , 2000 .

[3]  Gottfried Hänel,et al.  The Properties of Atmospheric Aerosol Particles as Functions of the Relative Humidity at Thermodynamic Equilibrium with the Surrounding Moist Air , 1976 .

[4]  F. G. Fernald.  Analysis of atmospheric lidar observations: some comments. , 1984, Applied optics.

[5]  J. Ackermann.  The Extinction-to-Backscatter Ratio of Tropospheric Aerosol: A Numerical Study , 1998 .

[6]  A. Papayannis,et al.  Analysis of the receiver response for a noncoaxial lidar system with fiber-optic output. , 2002, Applied optics.

[7]  Edwin W. Eloranta,et al.  Coincident Lidar and Aircraft Observations of Entrainment into Thermals and Mixed Layers , 1987 .

[8]  Alexandros Papayannis,et al.  Characterization of the vertical structure of Saharan dust export to the Mediterranean basin , 1999 .

[9]  J. Klett.  Lidar inversion with variable backscatter/extinction ratios. , 1985, Applied optics.

[10]  S. Freitas,et al.  A convective kinematic trajectory technique for low‐resolution atmospheric models , 2000 .

[11]  T. Eck,et al.  Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements , 2000 .

[12]  A. Ångström.  The parameters of atmospheric turbidity , 1964 .

[13]  Lidar Observations of Banded Convection during BLX83 , 1991 .

[14]  R. Pielke,et al.  A Climate Version of the Regional Atmospheric Modeling System , 2000 .

[15]  R. Stull.  An Introduction to Boundary Layer Meteorology , 1988 .

[16]  R. Pielke,et al.  A comprehensive meteorological modeling system—RAMS , 1992 .

[17]  J. Seinfeld,et al.  Dynamics of Tropospheric Aerosols , 1995 .

[18]  R. Harriss,et al.  Ozone and aerosol distributions over the Amazon Basin during the wet season , 1990 .

[19]  U. Panne.  Laser remote sensing , 1998 .

[20]  M. King,et al.  Acute effects of inhalable particles on the frog palate mucociliary epithelium. , 1999, Environmental health perspectives.

[21]  M. Wendisch,et al.  Optical and microphysical characterization of biomass‐ burning and industrial‐pollution aerosols from‐ multiwavelength lidar and aircraft measurements , 2002 .

[22]  Y Sasano,et al.  Tropospheric aerosol optical properties derived from lidar, sun photometer, and optical particle counter measurements. , 1994, Applied optics.

[23]  D. Dockery,et al.  Air pollution and mortality in elderly people: a time-series study in Sao Paulo, Brazil. , 1995, Archives of environmental health.

[24]  Eric P. Shettle,et al.  Atmospheric Aerosols: Global Climatology and Radiative Characteristics , 1991 .

[25]  T. Eck,et al.  Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols , 1999 .

[26]  A. Bais,et al.  Optical properties of tropospheric aerosols determined by lidar and spectrophotometric measurements (Photochemical Activity and Solar Ultraviolet Radiation campaign). , 1997, Applied optics.

[27]  C. D. Alonso,et al.  São Paulo aerosol characterization study. , 1997, Journal of the Air & Waste Management Association.

[28]  T. Eck,et al.  An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET , 2001 .

[29]  Ellsworth J. Welton,et al.  Measurements of aerosol vertical profiles and optical properties during INDOEX 1999 using micropulse lidars , 2002 .

[30]  Alexandros Papayannis,et al.  Study of the structure of the lower troposphere over Athens using a backscattering lidar during the MEDCAPOT-TRACE experiment: measurements over a suburban area , 1998 .

[31]  Michael D. King,et al.  A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements , 2000 .

[32]  B. Clemesha,et al.  The stratospheric scattering profile at 23° South , 1971 .

[33]  Albert Ansmann,et al.  Vertical profiling of optical and physical particle properties over the tropical Indian Ocean with six‐wavelength lidar: 2. Case studies , 2001 .

[34]  EARLINET : the European Aerosol Lidar Network , 2005 .

[35]  Alexandros Papayannis,et al.  The EOLE Project: A multiwavelength laser remote sensing (lidar) system for ozone and aerosol measurements in the troposphere and the lower stratosphere. Part II: Aerosol measurements over Athens, Greece , 2002 .

[36]  C. Flamant,et al.  Urban boundary-layer height determination from lidar measurements over the paris area. , 1999, Applied optics.

[37]  A. Ansmann,et al.  Retrieval of physical particle properties from lidar observations of extinction and backscatter at multiple wavelengths. , 1998, Applied optics.

[38]  Christos Zerefos,et al.  Tropospheric LIDAR aerosol measurements and sun photometric observations at Thessaloniki, Greece , 2000 .

[39]  Y Sasano,et al.  Geometrical form factor in the laser radar equation: an experimental determination. , 1979, Applied optics.

[40]  J. Bösenberg,et al.  EARLINET: A European Aerosol Research Lidar Network to Establish an Aerosol Climatology , 2003 .

[41]  Multiwavelength lidar for ozone measurements in the troposphere and the lower stratosphere. , 1990, Applied optics.

[42]  Hermann E. Gerber,et al.  Aerosols and Their Climatic Effects , 1985 .

[43]  A. Ansmann,et al.  Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar. , 1992, Applied optics.

[44]  Mark J. Rood,et al.  In situ measurement of the aerosol extinction‐to‐backscatter ratio at a polluted continental site , 2000 .

[45]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .