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Modelling of atmospheric optical thickness from spectroradiometer measurements in Penang Island

Modelling of atmospheric optical thickness from spectroradiometer measurements in Penang Island

H. S. Lim
School of Physics
Universiti Sains Malaysia
Minden 11800 Penang, Malaysia.
Tel: +604-6577888, Fax: +604-6579150
[email protected]

M. Z. MatJafri
School of Physics
Universiti Sains Malaysia
Minden 11800 Penang, Malaysia.
Tel: +604-6577888, Fax: +604-6579150
[email protected]

K. Abdullah
School of Physics
Universiti Sains Malaysia
Minden 11800 Penang, Malaysia.
Tel: +604-6577888, Fax: +604-6579150
[email protected]

N. M. Saleh
School of Physics
Universiti Sains Malaysia
Minden 11800 Penang, Malaysia.
Tel: +604-6577888, Fax: +604-6579150

C. J. Wong
School of Physics
Universiti Sains Malaysia
Minden 11800 Penang, Malaysia.
Tel: +604-6577888, Fax: +604-6579150

Sultan AlSultan
Remote Sensing Center of Envir. Counsultant
ISPRS, commission 7 WG VII/7, Middle East Coordinator
Malaz, Al Nurii St., P.O.Box.92038
Riaydh City 11653, Saudi Arabia.
Tel: +966504890977 Fax: +96614767828
[email protected]

ABSTRACT

A study has been carried out for the estimation of aerosol optical thickness (AOT) using a handheld spectroradiometer measurements over Penang Island, Malaysia. The AOT values were retrieved from the atmospheric transmittance measurements in the spectral region centred at 550nm. The concentrations of particulate matters of less than 10 micron (PM10) were measured simultaneously with the atmospheric transmittance measurements using a DustTrak Aerosol Monitor 8520 at several selected locations around Penang Island. The AOT is calculated using the expression given by the Beer-Lambert-Bouguer law. Its locations determined with a Global Positioning System (GPS) receiver. The relation between AOT and PM10 has been investigated in this study. Finally, a PM10 map was generated using Kriging interpolation technique. This study proposed an alternative method for the retrieval of AOT values with a reasonable accuracy.

INTRODUCTION
Aerosols perturb the earth’s energy budget directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei and in doing so changing cloud properties. Their effects on temperature, hence atmospheric stratification, further influence clouds. The overall cooling by anthropogenic aerosols may be comparable to the warming of 2.43 Wm-2 by greenhouse gases [1].

A study was performed by using handheld spectroradiometer measurements for AOT mapping. The spectroradiometer was used to measure the atmospheric transmittances. The well known Beer-Lambert law was used in this study to retrieve AOT values from the measured transmittance values. The PM10 measurements were also collected simultaneously during the acquisition of the atmospheric transmittance measurements using DustTrak Aerosol Monitor 8520. In this study, we found a linear relationship between AOT and PM10. Finally, a PM10 map was generated using Kriging interpolation technique.

STUDY AREA
The study area is the Penang Island, Malaysia which is situated within latitudes 5o 12′ N to 5o 30′ N and longitudes 100o 09′ E to 100o 26′ E (Figure 1). The corresponding PM10 measurements were collected at the several selected locations.


Figure 1. The location of the study area