Modeling haboob dust storms in large‐scale weather and climate models

Abstract

Recent field campaigns have shown that haboob dust storms, formed by convective cold pool outflows, contribute a significant fraction of dust uplift over the Sahara and Sahel in summer. However, in situ observations are sparse and haboobs are frequently concealed by clouds in satellite imagery. Furthermore, most large-scale weather and climate models lack haboobs, because they do not explicitly represent convection. Here a 1 year long model run with explicit representation of convection delivers the first full seasonal cycle of haboobs over northern Africa. Using conservative estimates, the model suggests that haboobs contribute one fifth of the annual dust-generating winds over northern Africa, one fourth between May and October, and one third over the western Sahel during this season. A simple parameterization of haboobs has recently been developed for models with parameterized convection, based on the downdraft mass flux of convection schemes. It is applied here to two model runs with different horizontal resolutions and assessed against the explicit run. The parameterization succeeds in capturing the geographical distribution of haboobs and their seasonal cycle over the Sahara and Sahel. It can be tuned to the different horizontal resolutions, and different formulations are discussed with respect to the frequency of extreme events. The results show that the parameterization is reliable and may solve a major and long-standing issue in simulating dust storms in large-scale weather and climate models.

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

“…While Pantillon et al (2016) propose a simple parametrization to represent the climatological effects of haboobs in coarserresolution models, the forecasting of severe events like the one investigated here can hardly be successful without explicit convection. Given the substantial impact of the event and the potential benefit of an early warning, forecasting centres around the world should consider running higherresolution dust forecasts on sufficiently large domains for the most vulnerable regions.…”

“…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).…”

“…Corroborating Marsham et al (2011), they find that approximately 40 % of dust emissions can be linked to CPOs, highlighting the need for convection-permitting resolution modelling. In another in-depth study of CPOs, Pantillon et al (2016) analyse yearlong convection-permitting simulations in the Sahara region. 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.…”

Revised mineral dust emissions in the atmospheric chemistry–climate model EMAC (MESSy 2.52 DU_Astitha1 KKDU2017 patch)

“…The inability of most current global models to resolve convection means that haboobs, which are responsible for a major fraction of the dust emissions (Marsham et al, 2013;Allen et al, 2013Allen et al, , 2015, are not represented at all. Therefore, efforts are made to combine the emission schemes with explicit parameterisations of convective dust storms (Pantillon et al, 2015(Pantillon et al, , 2016.…”

Status and future of Numerical Atmospheric Aerosol Prediction with a focus on data requirements

“…This is also partly related to an underestimation of turbulent 580 dust emission during the day (Klose and Shao, 2012). Another substantial problem is the lack of dust generation related to cold pools (haboobs) associated with moist convection over the Sahel and Sahara (and many other desert areas), a process largely absent in models with parameterized convection (Marsham et al (2011);Heinold et al (2013); Pantillon et al (2015Pantillon et al ( , 2016). This leads to even reanalyses missing the summertime maximum in dust generating winds in the central Sahara 585 (Roberts et al, 2017).…”