Optical characteristics of desert dust as used in LOWTRAN: Mojave desert dust versus the LOWTRAN 7 dust model

Philip L. Walker; Larry A. Mathews

doi:10.1117/12.211933

15 June 1995 Optical characteristics of desert dust as used in LOWTRAN: Mojave desert dust versus the LOWTRAN 7 dust model

Philip L. Walker, Larry A. Mathews

Author Affiliations +

Proceedings Volume 2471, Atmospheric Propagation and Remote Sensing IV; (1995) https://doi.org/10.1117/12.211933
Event: SPIE's 1995 Symposium on OE/Aerospace Sensing and Dual Use Photonics, 1995, Orlando, FL, United States

Abstract

As previously reported aerosol size and composition and meteorological data were collected at three sites (Tehachapi Pass and Rogers and China Lake dry lake beds) in the western Mojave Desert in the summer of 1990. Aerosol size distributions exhibit the usual accumulation and wind speed dependent dust modes. The dust mode aerosols are illite clay. Their composition is wind speed independent for speeds up to 10 m/s, i.e. there is no silicate mode. Dust mass is wind speed independent up to 7 m/s. Beyond that, dust mass is exponentially related to wind speed by m equals 0.55 exp (0.59 u). Dust mass computed from the measured size distributions also exhibits the 7 m/s threshold. These characteristics are significantly different from the dust model used in LOWTRAN7/MODTRAN (based on Sahara data) which uses a large particle silicate mode in placed of the dust mode. It needs to be determined whether the optical properties of the two dust models are different enough to warrant changing the model in LOWTRAN. Their optical properties (extinction, albedo and asymmetry factor) from 2 to 12 (mu) are compared and used in LOWTRAN 7 for a variety of geometries and wind speeds. Perhaps two desert dust models should be used, one for an old desert such as the Sahara and another one for young deserts.

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Philip L. Walker and Larry A. Mathews "Optical characteristics of desert dust as used in LOWTRAN: Mojave desert dust versus the LOWTRAN 7 dust model", Proc. SPIE 2471, Atmospheric Propagation and Remote Sensing IV, (15 June 1995); https://doi.org/10.1117/12.211933

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