这种方法是直接根据沙尘监测图像目测划分的吗?

肯定有可能用客观方法，但先要有个定义。推荐一篇文献：Dusty cloud properties and radiative forcing over dust source and remote regions derived from CERES/CALIPSO during PACDEX文章里:
Dusty clouds are defined as clouds that exist in a dust plume environment (i.e., dust aerosols observed within 50 km of the cloud), while pure clouds are clouds in a dust-free environment.
就是用遥感卫星可以把沙尘云定义为: 云 50 公里内观察到沙尘。
这是你想要的东西？
地面观察网就不知道了。