Final answer:
An unsaturated air parcel starting at a temperature of 0°C at 3000 meters would warm at a lapse rate of 6.5 K per kilometer as it descends. Therefore, when it reaches sea level, the temperature of the air parcel would be 19.5°C.
Step-by-step explanation:
The question asks about the temperature change of an unsaturated parcel of air as it descends from 3000 meters to sea level. According to the adiabatic process in a neutral atmosphere, temperature changes at a rate referred to as the lapse rate, which is approximately 6.5 K per kilometer. Assuming the lapse rate is constant and that the parcel of air does not exchange heat with its surroundings, the temperature would increase by 6.5 K for every kilometer it descends.
If the air parcel started at 0°C at 3000 meters, descending to sea level, which is 3000 meters below, the temperature increase would be 6.5 K/km × 3 km = 19.5 K. This increase in temperature should be added to the initial temperature, resulting in the parcel of air having a temperature of 19.5°C at sea level.