Aerosol scattering properties at UV-wavelengths: Implications for dial measurements of tropospheric ozone

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:166535

Voelger, P; Boesenberg, J; Schult, I ^[1]

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1. Max-Planck-Institut fuer Meterologie, Hamburg (Germany)

Aerosol scattering properties are quite important for the application of remote sensing techniques at UV wavelengths. However, little information can be found in the literature. Especially ozone measurements with lidar are biased by scattering of aerosols at the wavelengths used for a Differential Absorption Lidar (DIAL), e.g. 277nm and 313nm. Therefore, to study the influence of aerosols an investigation was started, based on Mie theory and obtainable aerosol properties (size distribution and refractive index). Although the atmosphere is highly variable in space and time we restricted our calculations to four aerosol types which were assumed to be representative for most situations in Central Europe. The calculated extinction coefficients of aerosols in the UV yield approximately the same wavelength dependence as in the visible region. However, the backscatter coefficient shows a completely different behaviour below 350nm which in addition depends on the relative humidity. While {lambda}{sup -1} is a good estimate for the backscatter wavelength dependence in the visible, in the UV, {lambda}{sup o} for a moist atmosphere (i.e. more than 80% relative humidity) and ({lambda}-{lambda}{sub o}){sup +2} for a {open_quotes}standard{close_quotes} atmosphere (i.e. less than 80% relative humidity) are the appropriate relations. The wavelength dependence of aerosol extinction and backscatter is important for the correction of ozone retrievals from DIAL measurements. In regions of inhomogeneous aerosol distribution the correction due to aerosol backscatter can reach the magnitude of the uncorrected ozone density. Therefore, if the relative humidity is unknown the uncertainty in the correction itself can reach 20%.

• OSTI ID: 166535
• Report Number(s): CONF-9510126--
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ACCURACY
AEROSOLS
DISTRIBUTION
HUMIDITY
OPTICAL RADAR
OZONE
REFRACTIVE INDEX
REMOTE SENSING
SCATTERING
TROPOSPHERE
ULTRAVIOLET SPECTRA
WAVELENGTHS