Meteorological Aspects of Dust Storms

Knippertz, Peter

doi:10.1007/978-94-017-8978-3_6

Cited by 44 publications

(29 citation statements)

References 149 publications

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“…The underestimation of AOD in the source regions can also partly stem from underestimation of the dust emission flux in these areas. For instance, dust storms caused by convective systems and cold pools substantially contribute to emissions in southern Sahara, where convective organization is supported by shear underneath a midlevel jet (see, e.g., Knippertz, , and references therein). These frequent events are not resolved in the model configuration used in this study.…”

Section: Resultsmentioning

confidence: 99%

Effects of Particle Nonsphericity on Dust Optical Properties in a Forecast System: Implications for Model‐Observation Comparison

et al. 2019

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Mineral dust is a key player in the Earth system that affects the weather and climate through absorbing and scattering the radiation. Such effects strongly depend on the optical properties of the particles that are in turn affected by the particle shape. For simplicity, dust particles are usually assumed to be spherical. But this assumption can lead to large errors in modeling and remote sensing applications. This study investigates the impact of dust particle shape on its direct radiative effect in a next‐generation atmospheric modeling system ICON‐ART (ICOsahedral Nonhydrostatic weather and climate model with Aerosols and Reactive Trace gases) to verify if accounting for nonsphericity enhances the model‐observation agreement. Two sets of numerical experiments are conducted by changing the optical shape of the particles: one assuming spherical particles and the other one assuming a mixture of 35 randomly oriented triaxial ellipsoids. The simulations are compared to MISR (Multiangle Imaging Spectroradiometer), AERONET (Aerosol Robotic Network), and CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations (with focus on North Africa). The results show that consideration of particle nonsphericity increases the dust AOD (Aerosol Optical Depth) at 550 nm by up to 28% and leads to slight enhancement of the agreement between modeled and measured AOD. However, the model performance varies significantly when focusing on specific regions in North Africa. These differences stem from the uncertainties associated with particle size distribution and emission mechanisms in the model configuration. Regarding the attenuated backscatter, the simulated profile assuming nonsphericity differs by a factor of 2 to 5 from the experiment assuming spherical dust and is in a better agreement with the CALIPSO observations.

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Section: Resultsmentioning

confidence: 99%

Effects of Particle Nonsphericity on Dust Optical Properties in a Forecast System: Implications for Model‐Observation Comparison

et al. 2019

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“…It is therefore interesting to see how much these rare events contribute to interannual variations in DUP. These could be tied to single synoptic‐scale weather events such as Mediterranean cyclones [ Alpert and Ziv , ; Trigo et al , ] or to some longer‐lasting identifiable meteorological regime, as, for example, a shift of the Azores High into northwestern Africa or a strengthening of the Libyan High [ Knippertz , ].…”

Section: Resultsmentioning

confidence: 99%

The importance of rare, high‐wind events for dust uplift in northern Africa

Cowie

Marsham

Knippertz

2015

Geophysical Research Letters

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Dust uplift is a nonlinear thresholded function of wind speed and therefore particularly sensitive to the long tails of observed wind speed probability density functions. This suggests that a few rare high‐wind events can contribute substantially to annual dust emission. Here we quantify the relative roles of different wind speeds to dust‐generating winds using surface synoptic observations of dust emission and wind from northern Africa. The results show that winds between 2 and 5 m s−1 above the threshold cause the most emission. Of the dust‐generating winds, 25% is produced by very rare events occurring only at 0.1 to 1.4% of the time, depending on the region. Dust‐producing winds are underestimated in ERA‐I, since it misses the long tail found in observations. ERA‐I overpredicts (underpredicts) the frequency of emission strength winds in the southern (northern) regions. These problems cannot be solved by simple tunings. Finally, we show that rare events make the largest contribution to interannual variability in dust‐generating winds and that ERA severely underestimates this interannual variability.

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“…They conclude that in this region the contribution of convective CPOs to dust uplift potential is on the order of one-fifth of the annual budget, with substantially higher proportions of up to one-third over the summer months. In summary, CPOs have been identified as important systems contributing to dust emission (Knippertz et al, 2007;Marsham et al, 2011;Heinold et al, 2013;Pantillon et al, 2016), and their occurrence has been documented for all major dust source regions worldwide (Knippertz, 2014).…”

Section: Introductionmentioning

confidence: 99%

Revealing the meteorological drivers of the September 2015 severe dust event in the Eastern Mediterranean

et al. 2017

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Abstract. In September 2015 one of the severest and most unusual dust events on record occurred in the Eastern Mediterranean. Surprisingly, operational dust transport models were unable to forecast the event. This study details the reasons for this failure and presents simulations of the event at convection-permitting resolution using the modelling system ICON-ART. The results allow for an in-depth analysis of the influence of the synoptic situation, the complex interaction of multiple driving atmospheric systems and the mineral dust radiative effect on the dust event. A comparison of the results with observations reveals the quality of the simulation results with respect to structure and timing of the dust transport. The forecast of the dust event is improved decisively. The event is triggered by the unusually early occurrence of an active Red Sea trough situation with an easterly axis over Mesopotamia. The connected sustained organized mesoscale convection produces multiple cold-pool outflows responsible for intense dust emissions. Complexity is added by the interaction with an intense heat low, the inland-penetrating Eastern Mediterranean sea breeze and the widespread occurrence of supercritical flow conditions and subsequent hydraulic jumps in the vicinity of the Dead Sea Rift Valley. The newly implemented mineral dust radiation interaction leads to systematically more intense and faster propagating coldpool outflows.

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Meteorological Aspects of Dust Storms

Cited by 44 publications

References 149 publications

Effects of Particle Nonsphericity on Dust Optical Properties in a Forecast System: Implications for Model‐Observation Comparison

Effects of Particle Nonsphericity on Dust Optical Properties in a Forecast System: Implications for Model‐Observation Comparison

The importance of rare, high‐wind events for dust uplift in northern Africa

Revealing the meteorological drivers of the September 2015 severe dust event in the Eastern Mediterranean

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