If one studies the second day of God’s creation in Genesis 1:6-8, one will notice there were waters below the sky (i.e., oceans) and waters above the sky. The idea is that a water vapor once existed above our atmosphere. Many believe that same water vapor came down on the earth when the great flood happened.
If such a water vapor in the sky still existed today, ultraviolet rays (which is what causes our bodies to age) would have a minimal effect on our bodies. I don't know how much of this concept the author understood. I just suspect he understood the world was a better place before the waters that were above the earth “fell out of the sky” with the flood.
In the first part of verse 3, the point is simply that the author understood that God had “upper chambers of water” above our atmosphere as stated in Genesis 1:6. The psalmist is praising God for His intention of how He desires us to live in a world uncorrupted by sin.
Think of it this way. Sin causes us to age in the first place. In effect, God allowed ultraviolet rays to age us so we wouldn’t have to live forever in this world that is again, corrupted by sin. Think of aging as form of “mercy killing” by God.
[3b] who maketh the clouds His chariot: who walketh upon the wings of the wind:
 Who maketh His angels spirits; His ministers a flaming fire:
It may help to know that in the Hebrew language, the word for “spirit” and the word for “wind” is the same word.
Jesus once made a pun on the fact that “wind” and “spirit” are the same word. Jesus said in effect, ‘We don’t know which way the wind blows and we also don’t know how the Spirit of God works in people’s lives.’ (paraphrase of John 3:8.)
Verses 3 and 4 are making a similar comment. The Spirit of God “hovers” over the created world in a way for us to appreciate it. The idea in effect is that God did not create our world in a haphazard, or random format. He created it for the specific purpose to sustain and support the growth of life.
The Spirit of God was part of the creation of this world and it was made in a way for us to appreciate how it was made. The last part of verse 3 says God makes the clouds His chariots to ride upon, this is a poetic way of expressing that God’s Spirit created this world in a way for us to appreciate.
The last part of verse 4 mentions “a flaming fire”. This is another poetic way of describing how the world was made and how God’s Spirit was involved in that creation process.
These verses are a commentary on Genesis 1:2b that reads, “And the Spirit of God moved upon the face of the waters.” Verses 2-4 are expanding on that thought.