Why is the moist adiabatic lapse rate typically lower than the dry adiabatic lapse rate?

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Multiple Choice

Why is the moist adiabatic lapse rate typically lower than the dry adiabatic lapse rate?

Latent heat release during condensation warms the rising air, reducing the lapse rate. When a parcel rises and expands, it cools. If it is saturated, water vapor condenses and releases latent heat into the parcel. That added heat offsets part of the cooling from expansion, so the temperature drops more slowly with height than in the dry case. That slower cooling is the moist adiabatic lapse rate, which is typically around 4–7°C per kilometer (and varies with moisture and temperature), always lower than the dry rate (about 9.8°C per kilometer). If the air isn’t saturated, condensation doesn’t occur and the lapse rate stays near the dry value.

Latent heat release during condensation warms the rising air, reducing the lapse rate. When a parcel rises and expands, it cools. If it is saturated, water vapor condenses and releases latent heat into the parcel. That added heat offsets part of the cooling from expansion, so the temperature drops more slowly with height than in the dry case. That slower cooling is the moist adiabatic lapse rate, which is typically around 4–7°C per kilometer (and varies with moisture and temperature), always lower than the dry rate (about 9.8°C per kilometer). If the air isn’t saturated, condensation doesn’t occur and the lapse rate stays near the dry value.

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