Quantifying global dust devil occurrence from meteorological analyses

Abstract

Dust devils and nonrotating dusty plumes are effective uplift mechanisms for fine particles, but their contribution to the global dust budget is uncertain. By applying known bulk thermodynamic criteria to European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses, we provide the first global hourly climatology of potential dust devil and dusty plume (PDDP) occurrence. In agreement with observations, activity is highest from late morning into the afternoon. Combining PDDP frequencies with dust source maps and typical emission values gives the best estimate of global contributions of 3.4% (uncertainty 0.9-31%), 1 order of magnitude lower than the only estimate previously published. Total global hours of dust uplift by dry convection are ∼0.002% of the dust-lifting winds resolved by ECMWF, consistent with dry convection making a small contribution to global uplift. Reducing uncertainty requires better knowledge of factors controlling PDDP occurrence, source regions, and dust fluxes induced by dry convection.

Key points: Global potential dust devil occurrence quantified from meteorological analyses Climatology shows realistic diurnal cycle and geographical distribution Best estimate of global contribution of 3.4% is 10 times smaller than the previous estimate.

Keywords: climatology; dry convection; dust devils; dust emission; dusty plumes; vortices.

Figure 1

Global PDDP_hours (mean of 2012 and 2013) using different w_*/u_* and lapse rate criteria showing (a) diurnal cycle and (b) cumulative distribution as a percentage for the corresponding results in Figure 1a. In Figure 1b, values in parentheses are for w_*/u_* > 6.3.

Figure 2

Climatology of PDDP_hours (mean of 2012 and 2013) using w_*/u_* > 5.0 [Lyons et al., 2008] and 8.5 K m⁻¹ near-surface lapse rate [Ansmann et al., 2009] criteria for (a) annual total and (b–e) seasonal totals.

Figure 3

(a) Dust source fraction from Ginoux et al. [2001]. Dust uplift from DDPs using w_*/u_* > 5.0 [Lyons et al., 2008] and 8.5 K m⁻¹ near-surface lapse rate [Ansmann et al., 2009] criteria for regions (b) Northern Hemisphere dust belt, (c) Namib and Kalahari Deserts of southern Africa, (d) North America, (e) Atacama and Sechura Deserts of South America, and (f) Australia.