Scenario 1 If the atmospheric temperature decreases more rapidly with altitude than ALR because of unusual meteorological circumstances, then any parcel of air released near ground level and warmer than its surroundings will rise indefinitely into the upper atmosphere This is because as it cools at the alr, it will always be warmer and thereby less dense, than the surrounding air This unstable condition is obviously desirable because it leads to good vertical mixing and a relatively pollution-free lower atmosphereScenario 1 If the atmospheric temperature decreases more rapidly with altitude than ALR because of unusual meteorological circumstances, then any parcel of air released near ground level and warmer than its surroundings will rise indefinitely into the upper atmosphere. This is because as it cools at the ALR, it will always be warmer, and thereby less dense, than the surrounding air. This unstable condition is obviously desirable because it leads to good vertical mixing and a relatively pollution-free lower atmosphere