Can mechanical energy of a moving particle be negative

Yes mechanical energy can be negative.

You cannot have negative energy;

You can have a certain quantity of energy or none at all but it is impossible in reality to have negative energy;

In terms of equations however, you can have a positive or negative sign, this tells us whether energy is gained or lost

the results is a decrease in air temperature with an increase of altitude.

explanation:

a longitudinal wave moves energy that is to the direction of the wave’s movement. - true