Modeling coarse and giant desert dust particles
Modeling coarse and giant desert dust particles
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DOI：
10.5194/acp-22-12727-2022
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发表时间：
2022-09-29
影响因子：
6.3
通讯作者：
Katsafados, Petros
中科院分区：
文献类型：
--
作者：
Drakaki, Eleni;Amiridis, Vassilis;Katsafados, Petros
经常观察到直径大于20微米的尘埃颗粒在远距离迁移过程中保持在空气中。在这项工作中，我们修改的参数化的矿物尘埃循环的GOCART-AFWA灰尘计划的WRFV4.2.1，也包括这样的粗和巨大的颗粒，我们进一步讨论了潜在的歪曲的物理机制，阻碍了模型充分再现的粗和巨大的矿物颗粒的运输。初始粒径分布受到沙漠沙尘源观测的约束。此外，斯托克斯阻力系数已更新，以考虑到实际的尘埃颗粒尺寸（Re < 10（5））。2015年8月，新代码被应用于模拟卡波维德上空的粉尘输送（AER-D活动）。对空气中的灰尘测量和CALIPSO-LIVAS纯粉尘产品的模型结果进行了评价。结果表明，模拟的寿命较粗的颗粒比观察到的短。通过人工降低颗粒的沉降速度来进行几次灵敏度试验，以补偿相关参数化方案中代表性不足的机制，例如非球形空气动力学。我们的模拟显示，在沉降速度降低80%的假设下（UR 80），直径为5.5-17和40-100 μ m的颗粒更好地代表，而尺寸在17和40 μ m之间的颗粒在沉降速度降低60%的假设下（UR 60）更好地代表。总体统计分析表明，在沉降速度（UR 40）降低40%的情况下，与顺风（卡波佛得角）的机载原位测量结果最一致。此外，UR 80实验提高了代表性的灰尘层的垂直结构，因为那些被捕获的CALIPSO-LIVAS垂直分辨纯灰尘观测。目前的研究强调，有必要升级现有的灰尘生命周期组成部分的模型参数化计划，以改善对地球-大气系统内与灰尘有关的影响的评估。
Dust particles larger than 20 mu m in diameter have been regularly observed to remain airborne during long-range transport. In this work, we modify the parameterization of the mineral dust cycle in the GOCART-AFWA dust scheme of WRFV4.2.1 to also include such coarse and giant particles, and we further discuss the underlying misrepresented physical mechanisms which hamper the model in reproducing adequately the transport of the coarse and giant mineral particles. The initial particle size distribution is constrained by observations over desert dust sources. Furthermore, the Stokes drag coefficient has been updated to account for realistic dust particle sizes (Re < 10(5)). The new code was applied to simulate dust transport over Cabo Verde in August 2015 (AER-D campaign). Model results are evaluated against airborne dust measurements and the CALIPSO-LIVAS pure dust product. The results show that the modeled lifetimes of the coarser particles are shorter than those observed. Several sensitivity runs are performed by reducing artificially the particles' settling velocities in order to compensate underrepresented mechanisms, such as the non-spherical aerodynamics, in the relevant parameterization schemes. Our simulations reveal that particles with diameters of 5.5-17 and 40-100 mu m are better represented under the assumption of an 80 % reduction in the settling velocity (UR80), while particles with sizes ranging between 17 and 40 mu m are better represented in a 60 % reduction in settling velocity (UR60) scenario. The overall statistical analysis indicates that the best agreement with airborne in situ measurements downwind (Cabo Verde) is achieved with a 40 % reduction in settling velocity (UR40). Moreover, the UR80 experiment improves the representation of the vertical structure of the dust layers as those are captured by the CALIPSO-LIVAS vertically resolved pure dust observations. The current study highlights the necessity of upgrading the existing model parameterization schemes of the dust life-cycle components towards improving the assessment of the dust-related impacts within the Earth-atmosphere system.