Hal Moseley was a Human scientist on Penthara IV.

In 2368, he enlisted the help of the USS Enterprise-D when the planet was threatened by environmental changes caused by an asteroid that hit an uninhabited part of the planet. A nuclear winter was a possibility. Geordi La Forge and Data tried to help with the problem. At first the Enterprise-D used phasers to release gas into the atmosphere to counter the effects of the nuclear winter. However, this only caused more damage, as the planet was hit with a series of earthquakes.

Moseley and La Forge decided on a solution that would either solve the problem or kill everyone on the planet. They initiated a chain reaction in the atmosphere that solved the problem. (TNG: "A Matter of Time")

Hal Moseley was played by Stefan Gierasch.
His first name comes from the script.
According to the script, Hal Moseley was a meteorologist.