The effect of temperature and humidity fluctuations on the liquid water path of non-precipitating closed-cell stratocumulus clouds

2008 ◽  
Vol 134 (631) ◽  
pp. 403-416 ◽  
Author(s):  
Stephan R. de Roode ◽  
Alexander Los
Keyword(s):  
Liquid Water ◽  
Effect Of Temperature ◽  
Liquid Water Path ◽  
Water Path ◽  
Closed Cell ◽  
Temperature And Humidity ◽  
Stratocumulus Clouds

scholarly journals Ground-based observations of cloud and drizzle liquid water path in stratocumulus clouds

2020 ◽  
Vol 13 (3) ◽  
pp. 1485-1499 ◽  
Author(s):  
Maria P. Cadeddu ◽  
Virendra P. Ghate ◽  
Mario Mech
Keyword(s):  
Liquid Water ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Cloud Base ◽  
Radiative Cooling ◽  
Liquid Water Path ◽  
Cell Systems ◽  
Water Path ◽  
Closed Cell ◽  
Stratocumulus Clouds

Abstract. The partition of cloud and drizzle water path in precipitating clouds plays a key role in determining the cloud lifetime and its evolution. A technique to quantify cloud and drizzle water path by combining measurements from a three-channel microwave radiometer (23.8, 30, and 90 GHz) with those from a vertically pointing Doppler cloud radar and a ceilometer is presented. The technique is showcased using 1 d of observations to derive precipitable water vapor, liquid water path, cloud water path, drizzle water path below the cloud base, and drizzle water path above the cloud base in precipitating stratocumulus clouds. The resulting cloud and drizzle water path within the cloud are in good qualitative agreement with the information extracted from the radar Doppler spectra. The technique is then applied to 10 d each of precipitating closed and open cellular marine stratocumuli. In the closed-cell systems only ∼20 % of the available drizzle in the cloud falls below the cloud base, compared to ∼40 % in the open-cell systems. In closed-cell systems precipitation is associated with radiative cooling at the cloud top <-100Wm-2 and a liquid water path >200 g m−2. However, drizzle in the cloud begins to exist at weak radiative cooling and liquid water path >∼150 g m−2. Our results collectively demonstrate that neglecting scattering effects for frequencies at and above 90 GHz leads to overestimation of the total liquid water path of about 10 %–15 %, while their inclusion paves the path for retrieving drizzle properties within the cloud.

scholarly journals Ground-based Observations of Cloud and Drizzle Liquid Water Path in Stratocumulus Clouds

2019 ◽  
Author(s):  
Maria P. Cadeddu ◽  
Virendra P. Ghate ◽  
Mario Mech
Keyword(s):  
Liquid Water ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Cloud Base ◽  
Radiative Cooling ◽  
Liquid Water Path ◽  
Cell Systems ◽  
Water Path ◽  
Closed Cell ◽  
Stratocumulus Clouds

Abstract. The partition of cloud and drizzle liquid water path in precipitating clouds plays a key role in determining the cloud lifetime and its evolution. A technique to quantify cloud and drizzle liquid water path by combining measurements from a three-channel microwave radiometer (23.8, 30, and 90 GHz) with those from a vertically pointing Doppler cloud radar and a ceilometer is presented. The technique is showcased using one-day of observations to derive precipitable water vapor, liquid water path, cloud water path, drizzle water path below the cloud base, and drizzle water path above the cloud base in precipitating stratocumulus clouds. The resulting cloud and drizzle water path within the cloud are in good qualitative agreement with the information extracted from the radar Doppler spectra. The technique is then applied to ten days each of precipitating closed and open cellular marine stratocumuli. In the closed cell systems only ~20% of the available drizzle in the cloud falls below the cloud base, compared to ~40% in the open cell systems. In closed cell systems precipitation is associated with radiative cooling at the cloud top < −100 W/m2 and liquid water path > 200 g/m2. However, drizzle in the cloud begins to exists at weak radiative cooling and liquid water path > ~150 g/m2. Our results collectively demonstrate that neglecting scattering effects for frequencies at and above 90 GHz leads to overestimation of the total liquid water path of about 10–15%, while their inclusion paves the path for retrieving drizzle properties within the cloud.

scholarly journals The Spiderweb Structure of Stratocumulus Clouds

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 730
Author(s):  
Georgios Matheou ◽  
Anthony B. Davis ◽  
João Teixeira
Keyword(s):  
Liquid Water ◽  
Evaporative Cooling ◽  
Liquid Water Content ◽  
Entrainment Rate ◽  
Liquid Water Path ◽  
Integral Boundary ◽  
Water Path ◽  
Large Eddy ◽  
Stratocumulus Clouds ◽  
Distinctive Structure

Stratocumulus clouds have a distinctive structure composed of a combination of lumpy cellular structures and thin elongated regions, resembling canyons or slits. The elongated slits are referred to as “spiderweb” structure to emphasize their interconnected nature. Using very high resolution large-eddy simulations (LES), it is shown that the spiderweb structure is generated by cloud-top evaporative cooling. Analysis of liquid water path (LWP) and cloud liquid water content shows that cloud-top evaporative cooling generates relatively shallow slits near the cloud top. Most of liquid water mass is concentrated near the cloud top, thus cloud-top slits of clear air have a large impact on the entire-column LWP. When evaporative cooling is suppressed in the LES, LWP exhibits cellular lumpy structure without the elongated low-LWP regions. Even though the spiderweb signature on the LWP distribution is negligible, the cloud-top evaporative cooling process significantly affects integral boundary layer quantities, such as the vertically integrated turbulent kinetic energy, mean liquid water path, and entrainment rate. In a pair of simulations driven only by cloud-top radiative cooling, evaporative cooling nearly doubles the entrainment rate.

scholarly journals Relationship between drizzle rate, liquid water path and droplet concentration at the scale of a stratocumulus cloud system

2008 ◽  
Vol 8 (16) ◽  
pp. 4641-4654 ◽  
Author(s):  
O. Geoffroy ◽  
J.-L. Brenguier ◽  
I. Sandu
Keyword(s):  
Liquid Water ◽  
Field Experiments ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Data Set ◽  
Water Path ◽  
Droplet Concentration ◽  
Stratocumulus Clouds ◽  
Shallow Clouds ◽  
The One

Abstract. The recent ACE-2, EPIC and DYCOMS-II field experiments showed that the drizzle precipitation rate of marine stratocumulus scales with the cloud geometrical thickness or liquid water path, and the droplet concentration, when averaged over a domain typical of a GCM grid. This feature is replicated here with large-eddy-simulations using state-of-the-art bulk parameterizations of precipitation formation in stratocumulus clouds. The set of numerical simulations shows scaling relationships similar to the ones derived from the field experiments, especially the one derived from the DYCOMS-II data set. This result suggests that the empirical relationships were not fortuitous and that they reflect the mean effect of cloud physical processes. Such relationships might be more suited to GCM parameterizations of precipitation from shallow clouds than bulk parameterizations of autoconversion, that were initially developed for cloud resolving models.

scholarly journals Comparison of a global-climate model to a cloud-system resolving model for the long-term response of thin stratocumulus clouds to preindustrial and present-day aerosol conditions

2009 ◽  
Vol 9 (5) ◽  
pp. 21317-21369 ◽  
Author(s):  
S. S. Lee ◽  
J. E. Penner
Keyword(s):  
Liquid Water ◽  
Environmental Conditions ◽  
General Circulation ◽  
Global Climate Model ◽  
Cloud System ◽  
Percentage Increase ◽  
Liquid Water Path ◽  
Cumulus Clouds ◽  
Water Path ◽  
Stratocumulus Clouds

Abstract. The response of a case of thin, warm marine-boundary-layer (MBL) clouds to preindustrial (PI) and present-day (PD) conditions is simulated by a cloud-system resolving model (CSRM). Here, both the aerosol conditions and environmental conditions match those of a general circulation model (GCM). The environmental conditions are characterized by the initial condition and the large-scale forcings of humidity and temperature, as well as the surface fluxes. The response of the CSRM is compared to that simulated by GCM. The percentage increase of liquid-water path (LWP) due to a change from the PI to PD conditions is ~3 times larger in the CSRM than that in the GCM due to the formation of cumulus clouds. The formation of cumulus clouds is controlled by a larger increase in the surface latent-heat (LH) flux in the PD environment than in the PI environment rather than by the change in aerosols. However, the aerosol increase from the PI to PD level determines the LWP response in the stratocumulus clouds, while the impacts of changes in environmental conditions are negligible for stratocumulus clouds. The conversion of cloud liquid to rain through autoconversion and accretion plays a negligible role in the CSRM in the response to aerosols, whereas it plays a role that is as important as condensation in the GCM. Supplementary simulations show that increasing aerosols increase the sensitivity of the cloud responses to the PI and PD environmental conditions and that aerosol effects on clouds depend on the cloud type; the liquid water path (LWP) of warm cumulus clouds is more sensitive to aerosols than the LWP of stratocumulus clouds.

scholarly journals Liquid Water Path Steady States in Stratocumulus: Insights from Process-Level Emulation and Mixed-Layer Theory

2020 ◽  
Vol 77 (6) ◽  
pp. 2203-2215 ◽  
Author(s):  
Fabian Hoffmann ◽  
Franziska Glassmeier ◽  
Takanobu Yamaguchi ◽  
Graham Feingold
Keyword(s):  
Steady State ◽  
Mixed Layer ◽  
Liquid Water ◽  
Global Radiation ◽  
Steady States ◽  
Radiation Budget ◽  
Liquid Water Path ◽  
Water Path ◽  
Entrainment Velocity ◽  
Stratocumulus Clouds

Abstract Stratocumulus clouds constitute one of the largest negative climate forcings in the global radiation budget. This forcing is determined, inter alia, by the cloud liquid water path (LWP), which we analyze using a combination of Gaussian process emulation and mixed-layer theory. For nocturnal, nonprecipitating stratocumuli, we show that LWP steady states constitute an equilibrium primarily between radiative cooling and entrainment warming and drying. These steady states are approached from lower LWPs due to reduced entrainment, while higher LWPs are depleted by stronger entrainment. An analytical solution for the LWP steady state reveals not only the environmental conditions in which a stratocumulus cloud can be maintained, but also distinct analytical properties of the entrainment velocity that are required for a stable LWP steady state that opposes perturbations. In particular, the results highlight the importance of an entrainment velocity that increases strictly monotonically with the LWP if stratocumuli are to attain a stable LWP steady state. This is demonstrated through analysis of two commonly used mixed-layer entrainment parameterizations.

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