EXPERIMENT ON DUST FLUX DURING DUST STORM PERIODS OVER SAND DESERT AREA

Based on dust concentration and micrometeorological data obtained during the IOP (Intensive Observation Period) of dust storm over Hunshandake desert area during the spring of 2004, the turbulent exchange coefficients, turbulent fluxes of momentum, heat and dust concentration were calculated. The characteristics of turbulence and dust transport, as well as the dust emission conditions were investigated. The results show that the turbulent exchange of heat is dominant during daytime of non-dusty days over Hunshandake desert area. During dust events, dynamic turbulence increases obviously, the turbulent exchanges of momentum and sensible heat are both important in the surface layer and the sensible heat flux is reduced by different degrees. During the intense dust storm event, the dynamic turbulence even exceeds the thermodynamic turbulence. During dust events, the value of dust flux gradually varies from positive to negative, which indicates the time evolvement of dust storm process. The range of dust flux are ±5 μg/(m2?s), ±30 μg/(m2?s) and -200-300 μg/(m2?s) during non dusty days, blowing dust and dust storm event, respectively. Smaller value of dust flux can be observed during non-dusty days over Hunshandake desert area. The dust emission flux is approximately proportional to the third power of friction velocity over Hunshandake desert area. The threshold values of wind speed and friction velocity are found to be about 6 and 0.4 m/s, respectively.