Info

Fig. 6. The same as Fig. 4, except for TKE in the case of Ax = 4 km with subgrid-scale updraft acceleration.

Fig. 6. The same as Fig. 4, except for TKE in the case of Ax = 4 km with subgrid-scale updraft acceleration.

Fig. 7. Temporal variation of the maximum updraft in the domain for the cases of 100 m grid, 4-km grid, and 4-km grid with subgrid-scale updraft acceleration.

Fig. 7. Temporal variation of the maximum updraft in the domain for the cases of 100 m grid, 4-km grid, and 4-km grid with subgrid-scale updraft acceleration.

The temporal variation of the maximum upward velocity in the computational domain is compared in Fig. 7. Although the velocity in the 4-km grid run with SUA is weaker than that in the 100-m grid case, adding the forcing term overall improves the velocity variation as compared with the 4-km run without the parameterization. Furthermore, the distribution of the frequency of surface wind speed (not shown) indicated that the feature seen in the 100-m grid case was better captured in the case of 4-km grid with SUA than without the parameterization.

With the boundary-layer development and associated surface wind variation being better represented with the SUA parameterization, the convective dust transport therefore is better reproduced as shown in Fig. 8 (compare with Fig. 4(e)). The diurnal evolution of vertical dust transport with SUA compares well with the control case as shown in Fig. 3: the initial development and gradual increase of dust content is better represented with the parameterization than without it. The column dust content at the end of the simulation period is 0.72 g m~2; this value also compares well with the estimate by the control simulation.

In this way, the simple formulation of Eq. (1) seems to be a plausible candidate for parameterizing both shallow and deep convection under the present meteorological setting and for representing the associated convective dust transport. However, a proper choice of t remains to be determined. We consider that t should be determined from a characteristic timescale for convective motion with a scale of O (1km). A typical velocity for this motion is on the order of 1ms-1, and thus the equivalent timescale becomes ~ 1000 s. Therefore, the present choice of t = 10min

Fig. 8. The same as Fig. 3, except for the case of Ax = 4 km with subgrid-scale updraft acceleration.

Fig. 8. The same as Fig. 3, except for the case of Ax = 4 km with subgrid-scale updraft acceleration.

is considered to be reasonable. Overall, introducing the parameterization seems to improve the development and evolution of dust transport.

Was this article helpful?

0 0
Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook


Post a comment