Angular Illumination and Truncation of Three Different Integrating Nephelometers: Implications for Empirical, Size-Based Corrections

Figures & data

TABLE 1 Nephelometer models and specifications

Manufacturer	Model	Number of units	Light source	Wave-length	Bandwidth FWHM	Angular integration range
TSI St. Paul, MN USA	3563	15 3/15 for illumination	Incandescent quartz-halogen, opal glass diffuser	450, 550, 700 nm	40 nm	7° to 170°
Radiance Research Seattle, WA USA	M903	2	Xenon flash lamp, opal glass diffuser	540 nm*	40 nm	10° to 170°
Ecotech Knoxfield, VIC Australia	9003	3	7 LED tuned array, ground glass diffuser	525 nm	60 nm	12° to 165°

FIG. 1 Schematic of the goniometer used to measure the angular illumination function of the nephelometer light sources in WCCAP2007.

FIG. 2 Angular intensity function, f(θ), including forward and backward truncation, for the TSI 3563, Radiance Research M903 and Ecotech 9003 nephelometers at green wavelengths. For comparison purposes, each function has been normalized to the area under the reference sine curve over the truncation angle range of the TSI instrument, 7 to 170 degrees.

FIG. 3 Calculated generic correction factor, C _ts , vs. D _gv for three models of nephelometers accounting for truncation and angular illumination function of the light sources. The result of Anderson and Ogren (1998) from the previous illumination function for the same aerosol parameters is shown for comparison.

FIG. 4 Calculated generic correction factor, C _ts , versus Ångström exponent for the TSI 3563, Radiance Research M903 and Ecotech 9003 nephelometers based on the WCCAP2007 angular illumination function. Results based on Anderson and Ogren (1998) are shown for comparison. The horizontal bars show ranges of Ångström exponent from several regions of the globe as measured with a TSI three wavelength nephelometer (Andrews 2004; Carrico 2000; Doherty 2005; Quinn 2000; Sierau 2006).

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