What should be recorded in column 9 if blowing dust is reducing visibility to 5/8 statute mile?

In situations where blowing dust affects visibility, the appropriate code to record is "DS," which stands for dust storm. This designation is specifically used when dust is raised by the wind, leading to significant reductions in visibility, as is the case when visibility drops to 5/8 statute mile.

This code effectively communicates to meteorologists and pilots that the weather condition is specifically due to suspended dust particles, which is critical for safety and operational considerations. The context provided by the visibility condition (5/8 statute mile) confirms that the impact is more than trivial, warranting the classification of a visibility reduction due to dust.

Other choices may refer to different weather phenomena or intensity levels, but "DS" is the correct term for documenting conditions where visibility is markedly impaired by blowing dust.