Atmospheric Aerosol Variability Over The Region of San Pedro Martir from Modis Data

 

Mario R. Araiza Quijano and Irene Cruz–González

 

Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70–264, 04510 México, D. F., México (maraizaq@astroscu.unam.mx, irene@astro.unam.mx).

 

Received 2010 June 23
Accepted 2011 August 15

 

RESUMEN

Se presenta un estudio del espesor óptico del aerosol atmosférico (AOT por sus siglas en ingles) en el sitio astronómico de San Pedro Mártir, B. C., México durante el periodo 2000–2008. Las mediciones del AOT se realizaron con el instrumento Moderate Resolution Imaging Spectroradiometer (MODIS), a bordo de los satélites Aqua y Terra de la NASA. Se han identificado valores característicos estacionales que muestran un comportamiento de mayor transparencia atmosférica durante el otoño. Las mejores condiciones de transparencia atmosférica ocurren durante octubre y noviembre. El comportamiento anual durante 2000–2008 del AOT de MODIS da valores promedio de 0.147 ± 0.103, 0.128 ± 0.090, 0.115 ± 0.081, 0.087 ± 0.066 en 4700, 5500, 6600 and 21300 Å, respectivamente. Utilizando estos valores promedio se analizó la dependencia del AOT con la longitud de onda, y se encontró que αOIR ~ 0.31 ± 0.06 y la relación τλ ~ 0.0061λ^–031 para dispersión por aerosoles en el sitio de San Pedro Mártir.

 

ABSTRACT

A study is presented of the atmospheric aerosol optical thickness (AOT) in the astronomical site of San Pedro Mórtir, B. C., Mexico, during the 2000–2008 period. The AOT measurements were made by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrumentation, on board of the NASA Aqua and Terra satellites. Characteristic seasonal values were identified, showing a higher atmospheric transparency in autumn. The best conditions for atmospheric transparency occur in October and November. The annual behavior of MODIS AOT yields average values for SPM during the years 2000–2008 of 0.147 ± 0.103, 0.128 ± 0.090, 0.115 ± 0.081, 0.087 ± 0.066 at 4700, 5500, 6600 and 21300 Å, respectively. We used these mean values to analyze the wavelength dependence and found aerosol scattering slopes αOIR ~ 0.31 ± 0.06 y la relación τλ ~ 0.0061λ^–031, for aerosol scattering over the San Pedro Maórtir location.

Key Words: atmospheric effects — site testing.

 

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ACKNOWLEDGMENTS

We thank the staff at Observatorio Astronómico Nacional (Instituto de Astronomía, Universidad Nacional Autónoma de México), the Solar Radiation Observatory (Instituto de Geofísica, Universidad Nacional Autónoma de México), and the MODIS Aerosol NASA for providing valuable information and data. We thank W. Schuster and L. Parrao for kindly providing their extinction data and for helpful discussions. We also thank A. Leyva Contreras for helpful and valuable advice. We are indebted to A. Muhlia Velázquez for his assistance and personnel at the Coordination of Remote Perception in Conabio (México), specially, to A. Cervera Taboada and to G. López Saldaña, for providing assistance with data processing. M. Araiza Quijano acknowledges Conacyt (México) postdoctoral fellowship, and the Instituto de Astronomía, UNAM for providing the facilities and the academic environment for this work. We also thank the referee for his/her helpful comments.

 

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