Spectral density of cloud liquid water content at high frequencies

Aircraft measurements of liquid water content (LWC) made at sampling freque ncies of 1 and 2 kHz with a particle volume monitor (PVM) probe from horizo ntal traverses in stratocumulus clouds during the Southern Ocean Cloud Expe riment and cumulus clouds during the Small Cumulus Microphysics Study are d escribed. The spectral density of the LWC measurements is calculated and co mpared to the -5/3 scaling law. The effect of PVM sampling noise is found t o be small in most cases. Most measurements follow approximately the -5/3 l aw until cloud scales decrease below about 5 m in length. Below this length LWC variance can exceed that predicted by the -5/3 law. It is suggested th at the enhanced LWC variance at small scales is related to entrainment of e nvironmental air into the clouds, which changes primarily the droplet conce ntration.