Publication Abstracts

Miller and Tegen 1998

Miller, R.L., and I. Tegen, 1998: Climate response to soil dust aerosols. J. Climate, 11, 3247-3267, doi:10.1175/1520-0442(1998)011<3247:CRTSDA>2.0.CO;2.

The effect of radiative forcing by soil dust aerosols upon climate is calculated. Two atmospheric GCM (AGCM) simulations are compared, once containing a prescribed seasonally varying concentration of dust aerosols, and the other omitting dust. Each simulation includes a mixed layer ocean model, which allows SST to change in response to the reduction in surface net radiation by dust. Dust aerosols reduce the surface net radiation both by absorbing and reflecting sunlight. For the optical properties of the dust particles assumed here, the reflection of sunlight is largely offset by the trapping of upwelling longwave radiation, so that the perturbation by dust to the net radiation gain at the top of the atmosphere is small in comparison to the surface reduction. Consequently, the radiative effect of soil dust aerosols is to redistribute heating from the surface to within the dust layer.

Beneath the dust layer, surface temperature is reduced on the order of 1 K, typically in regions where deep convection is absent. In contrast, surface temperature remains unperturbed over the Arabian Sea during Northern Hemisphere (NH) summer, even though the dust concentration is highest in this region. It is suggested that the absence of cooling results from the negligible radiative forcing by dust at the top of the atmosphere, along with the frequent occurrence of deep convection, which ties the surface temperature to the unperturbed value of the emitting level.

Where convection is absent, cooling at the surface occurs because radiative forcing by dust reduces the rate of subsidence (and the corresponding mass exchange with the convecting region). Thus, the temperature contrast between these two regions must increase to maintain the original transport of energy, which is unperturbed by dust. It is suggested that cooling over the Arabian Sea during NH winter, despite the much smaller dust loading, is permitted by the absence of convection during this season. Thus, the change in surface temperature forced by dust depends upon the extent of overlap between the dust layer and regions of deep convection, in addition to the magnitude of the radiative forcing.

Surface temperature is also reduced outside of the dust cloud, which is unlikely to result solely from natural variability of the AGCM.

It is suggested that the perturbation by dust to Indian and African monsoon rainfall may depend upon the extent to which ocean dynamical heat transports are altered by dust.

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BibTeX Citation

@article{mi05100g,
  author={Miller, R. L. and Tegen, I.},
  title={Climate response to soil dust aerosols},
  year={1998},
  journal={J. Climate},
  volume={11},
  pages={3247--3267},
  doi={10.1175/1520-0442(1998)011%3C3247%3ACRTSDA%3E2.0.CO;2},
}

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RIS Citation

TY  - JOUR
ID  - mi05100g
AU  - Miller, R. L.
AU  - Tegen, I.
PY  - 1998
TI  - Climate response to soil dust aerosols
JA  - J. Climate
VL  - 11
SP  - 3247
EP  - 3267
DO  - 10.1175/1520-0442(1998)011%3C3247%3ACRTSDA%3E2.0.CO;2
ER  -

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