Remote sensing of volcanic ash and sulfur dioxide - Volcanism and Global Environmental Change - page 105

(a) (b)

(c) (d)

Figure 7.3 (a) MODIS 11 μ m brightness temperature image. (b) MODIS 12 μ m

- μ

brightness temperature image. (c) MODIS 11 m brightness temperature differ-

ence image. (d) Ash mass-loading retrieval based on the MODIS brightness tem-
perature data. The MODIS/Terra image was acquired on 8 May 2010 at 11:55 UT.

12

where τ is the IR optical depth, r e is the effective particle radius, ρ is the density

of the ash, Q ext is the extinction ef is the wavelength. It is possible

to simplify further by assuming that the optical depth is equal at the two IR
wavelengths used; then we may write,

ciency and λ