M. A. J. Harrison

Publications (5)0 Total impact

• Article: Observations and modelling of the solar and terrestrial radiative effects of Saharan dust: a radiative closure case-study over oceans during the GERBILS campaign

  J. M. Haywood, B. T. Johnson, S. R. Osborne, J. Mulcahy, M. E. Brooks, M. A. J. Harrison, S. F. Milton, H. E. Brindley
  Quarterly Journal of the Royal Meteorological Society. 01/2011; 137(658):1211-1226.
• Source

  Available from: atmos-chem-phys-discuss.net

  Article: Using aircraft measurements to determine the refractive index of Saharan dust during the DODO Experiments

  C. L. McConnell, Formenti P, E. J. Highwood, M. A. J. Harrison
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  ABSTRACT: Much uncertainty in the value of the imaginary part of the refractive index of mineral dust contributes to uncertainty in the radiative effect of mineral dust in the atmosphere. A synthesis of optical, chemical and physical in-situ aircraft measurements from the DODO experiments during February and August 2006 are used to calculate the refractive index mineral dust encountered over West Africa. Radiative transfer modeling and measurements of broadband shortwave irradiance at a range of altitudes are used to test and validate these calculations for a specific dust event on 23 August 2006 over Mauritania. Two techniques are used to determine the refractive index: firstly a method combining measurements of scattering, absorption, size distributions and Mie code simulations, and secondly a method using composition measured on filter samples to apportion the content of internally mixed quartz, calcite and iron oxide-clay aggregates, where the iron oxide is represented by either hematite or goethite and clay by either illite or kaolinite. The imaginary part of the refractive index at 550 nm (ni550) is found to range between 0.0001 i to 0.0046 i, and where filter samples are available, agreement between methods is found depending on mineral combination assumed. The refractive indices are also found to agree well with AERONET data where comparisons are possible. ni550 is found to vary with dust source, which is investigated with the NAME model for each case. The relationship between both size distribution and ni550 on the accumulation mode single scattering albedo at 550 nm (ω0550) are examined and size distribution is found to have no correlation to ω0550, while ni550 shows a strong linear relationship with ω0550. Radiative transfer modeling was performed with different models (Mie-derived refractive indices, but also filter sampling composition assuming both internal and external mixing). Our calculations indicate that Mie-derived values of ni550 and the externally mixed dust where the iron oxide-clay aggregate corresponds to the goethite-kaolinite combination result in the best agreement with irradiance measurements. The radiative effect of the dust is found to be very sensitive to the mineral combination (and hence refractive index) assumed, and to whether the dust is assumed to be internally or externally mixed.
  Atmospheric Chemistry and Physics. 01/2010;
• Article: The development of a new dust uplift scheme in the Met Office Unified Model™

  D. Ackerley, E. J. Highwood, M. A. J. Harrison, C. L. McConnell, M. M. Joshi, D. N. Walters, S. F. Milton, G. Greed, M. E. Brooks
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  ABSTRACT: Aeolian mineral dust aerosol is an important consideration in the Earth's radiation budget as well as a source of nutrients to oceanic and land biota. The modelling of aeolian mineral dust has been improving consistently despite the relatively sparse observations to constrain them. This study documents the development of a new dust emissions scheme in the Met Office Unified Model™ (MetUM) based on the Dust Entrainment and Deposition (DEAD) module. Four separate case studies are used to test and constrain the model output. Initial testing was undertaken on a large dust event over North Africa in March 2006 with the model constrained using AERONET data. The second case study involved testing the capability of the model to represent dust events in the Middle East without being re-tuned from the March 2006 case in the Sahara. While the model is unable to capture some of the daytime variation in AERONET AOD there is good agreement between the model and observed dust events. In the final two case studies new observations from in situ aircraft data during the Dust Outflow and Deposition to the Ocean (DODO) campaigns in February and August 2006 were used. These recent observations provided further data on dust size distributions and vertical profiles to constrain the model. The modelled DODO cases were also compared to AERONET data to make sure the radiative properties of the dust were comparable to observations. Copyright © 2009 Royal Meteorological Society and Crown Copyright
  Meteorological Applications 11/2009; 16(4):445 - 460.
• Article: Physical and optical properties of mineral dust aerosol during the Dust and Biomass-burning Experiment

  S. R. Osborne, B.T. Johnson, J. M. Haywood, A.J. Baran, M. A. J. Harrison, C. L. McConnell
• Article: Seasonal variations of the physical and optical characteristics of Saharan Dust: Results from the Dust outflow and Deposition to the Ocean (DODO) experiment

  C. L. McConnell, E. J. Highwood, H. Coe, P. Formenti, B Anderson, S. Osborne, S Nava, K Desboeufs, G Chen, M. A. J. Harrison