Dynamics and Chemistry of Marine Stratocumulus (DYCOMS) Experiment

Abstract

A combined atmospheric chemistry-meteorology experiment, the Dynamics and Chemistry of the Marine Stratocumulus (DYCOMS), was carried out during the summer of 1985 over the eastern Pacific Ocean using the NCAR Electra aircraft. The objectives were to 1) study the budgets of several trace reactive species in a relatively pristine, steadystate, horizontally homogeneous, well-mixed boundary layer capped by a strong inversion and 2) study the formation, maintenance and dissipation of marine stratocumulus that persists off the California coast (as well as similar regions elsewhere) in summer. We obtained both mean and turbulence measurements of meteorological variables within and above the cloud-capped boundary layer that is typical of this region. Ozone was used successfully as a tracer for estimating entrainment rate. We found, however, that horizontal variability was large enough for ozone that a correction needs to be included in the ozone budget for the horizontal displacement due to turns even though the airplane was allowed to drift with the wind. The time rate-of-change term was significant in both the ozone and radon budgets; as a result, a considerably longer time interval than the two hours used between sets of flight legs would be desirable to improve the measurement accuracy of this term.

Relationship between Low Stratiform Cloud Amount and Estimated Inversion Strength in the Lower Troposphere over the Global Ocean in Terms of Cloud Types

“…On the other hand, using long-term soundings at several ocean weather stations, Norris (1998a) presented the composite potential temperature profiles for which the same low cloud condition had been reported: Sc typically occurred in a well-mixed MBL under a capping inversion, as observed by many field campaigns in the subtropical oceans (e.g., Albrecht et al 1988;Lenschow et al 1988;Albrecht et al 1995a;Stevens et al 2003;Bretherton et al 2004Bretherton et al , 2010; St occurred with a moderate stable condition throughout the MBL or in a very shallow layer near the surface; and FOG often occurred with a surface-based inversion. These results imply the existence of temperature inversions at the heights consistent with the morphology of each LSC type.…”

Physics of Stratocumulus Top (POST): turbulence characteristics

“…Several airborne research campaigns were aimed at investigating stratocumulus cloud top dynamics and thus the properties of the EIL, such as DYCOMS (Lenschow et al, 1988) and DYCOMS II (Stevens et al, 2003). The results (see, e.g., Lenschow et al, 2000;Gerber et al, 2005;Haman et al, 2007) indicate the presence of turbulence in the EIL, including inversion capping the STBL.…”

Physics of Stratocumulus Top (POST): turbulent mixing across capping inversion

“…Exchange processes between stratocumulus (Sc) clouds and the free troposphere (FT) above them have been intensively investigated in many research campaigns (e.g., Albrecht et al, 1988;Lenschow et al, 1988;Stevens et al, 2003;Bretherton et al, 2004). Despite the fact that marine stratocumulus is a relatively simple system -plane-parallel, warm cloud occupying the upper part of the well-mixed boundary layer above a homogeneous flat surface, and under an almost "rigid lid" temperature inversion of ∼ 10 K -the understanding of entrainment into the stratocumulus-topped boundary layer (STBL) from the free troposphere is limited.…”