Large-eddy simulations of the diurnal cycle of shallow convection and cloudiness over the tropical Indian Ocean

2008 ◽  
Vol 134 (632) ◽  
pp. 643-661 ◽  
Author(s):  
Hailong Wang ◽  
Greg M. McFarquhar
Keyword(s):  
Indian Ocean ◽  
Diurnal Cycle ◽  
Tropical Indian Ocean ◽  
Large Eddy Simulations ◽  
Shallow Convection ◽  
Large Eddy

Covariability of trade-wind cloudiness and environmental conditions in large-eddy simulations and observations

2021 ◽  
Author(s):  
Hauke Schulz ◽  
Ryan Eastman ◽  
Bjorn Stevens
Keyword(s):  
Environmental Conditions ◽  
Large Eddy Simulations ◽  
Trade Wind ◽  
Shallow Convection ◽  
First Case ◽  
Large Eddy ◽  
Cloud Radiative Effects ◽  
Weak Winds ◽  
Cloud Patterns ◽  
Lifting Condensation Level

<p>Shallow convection in the downwind trades occurs in form of different cloud patterns with characteristic cloud arrangements at the meso-scale. The four most dominant patterns were previously named Sugar, Gravel, Flowers and Fish and have been identified to be associated with different net cloud radiative effects.</p><p>By using long-term observations, we reveal that these differences can be mainly attributed to the stratiform cloud component that varies in extent across the patterns as opposed to the cloudiness at the lifting condensation level that is fairly constant independent of the patterns.</p><p>The observations reveal further, that each pattern is associated with a different environmental condition whose characteristics originate not soley from within the trades. Sugar air-masses are characterized by weak winds and of tropical origin, while Fish are driven by convergence lines originating from synoptical disturbances. Gravel and Flowers are most native to the trades, but distinguish themselves with slightly stronger winds and stronger subsidence in the first case and greater stability in the latter.</p><p>How well this covariability of cloudiness and environmental conditions is represented in simulations is important to project the occurrence of the patterns in a warmer climate and evaluated by realistic large-eddy simulations of the recent EUREC4A field campaign.</p>

scholarly journals Turbulence effects on warm-rain formation in precipitating shallow convection revisited

2016 ◽  
Vol 16 (18) ◽  
pp. 12127-12141 ◽  
Author(s):  
Axel Seifert ◽  
Ryo Onishi
Keyword(s):  
Isotropic Turbulence ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Shallow Convection ◽  
Surface Precipitation ◽  
Considerable Uncertainty ◽  
Warm Rain ◽  
Large Eddy ◽  
Turbulence Effects ◽  
Rain Formation

Abstract. Two different collection kernels which include turbulence effects on the collision rate of liquid droplets are used as a basis to develop a parameterization of the warm-rain processes autoconversion, accretion, and self-collection. The new parameterization is tested and validated with the help of a 1-D bin microphysics model. Large-eddy simulations of the rain formation in shallow cumulus clouds confirm previous results that turbulence effects can significantly enhance the development of rainwater in clouds and the occurrence and amount of surface precipitation. The detailed behavior differs significantly for the two turbulence models, revealing a considerable uncertainty in our understanding of such effects. In addition, the large-eddy simulations show a pronounced sensitivity to grid resolution, which suggests that besides the effect of sub-grid small-scale isotropic turbulence which is parameterized as part of the collection kernel also the larger turbulent eddies play an important role for the formation of rain in shallow clouds.

scholarly journals Extracting Microphysical Impacts in Large-Eddy Simulations of Shallow Convection

2014 ◽  
Vol 71 (12) ◽  
pp. 4493-4499 ◽  
Author(s):  
Wojciech W. Grabowski
Keyword(s):  
Traditional Approach ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Natural Variability ◽  
Large Eddy Simulations ◽  
Shallow Convection ◽  
Liquid Water Path ◽  
Large Eddy ◽  
The Mean ◽  
The Impact

Abstract A simple methodology is proposed to extract impacts of cloud microphysics on macrophysical cloud-field properties in large-eddy simulations of shallow convection. These impacts are typically difficult to assess because of natural variability of the simulated cloud field. The idea is to use two sets of thermodynamic variables driven by different microphysical schemes or by a single scheme with different parameters as applied here. The first set is coupled to the dynamics as in the standard model, and the second set is applied diagnostically—that is, driven by the flow but without the feedback on the flow dynamics. Having the two schemes operating in the same flow pattern allows for extracting the impact with high confidence. For illustration, the method is applied to simulations of precipitating shallow convection applying a simple bulk representation of warm-rain processes. Because of natural variability, the traditional approach provides an uncertain estimate of the impact of cloud droplet concentration on the mean cloud-field rainfall even with an ensemble of simulations. In contrast, the impact is well constrained while applying the new methodology. The method can even detect minuscule changes of the mean cloud cover and liquid water path despite their large temporal fluctuations and different evolutions within the ensemble.

scholarly journals Turbulence effects on warm rain formation in precipitating shallow convection revisited

2016 ◽  
Author(s):  
Axel Seifert ◽  
Ryo Onishi
Keyword(s):  
Isotropic Turbulence ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Shallow Convection ◽  
Surface Precipitation ◽  
Considerable Uncertainty ◽  
Warm Rain ◽  
Large Eddy ◽  
Turbulence Effects ◽  
Rain Formation

Abstract. Two different collection kernels which include turbulence effects on the collision rate of liquid droplets are used as a basis to develop a parameterization of the warm rain processes autoconversion, accretion and selfcollection. The new parameterization is tested and validated with help of a 1D bin microphysics model. Large-eddy simulations of the rain formation in shallow cumulus clouds confirm previous results that turbulence effects can significantly enhance the development of rain water in clouds and the occurrence and amount of surface precipitation. The detailed behavior differs significantly for the two turbulence models revealing a considerable uncertainty in our understanding of such effects. In addition, the large-eddy simulations show a pronounced sensitivity to grid resolution which suggests that besides the effect of sub-grid small scale isotropic turbulence which is parameterized as part of the collection kernel also the larger turbulent eddies play an important role for the formation of rain in shallow clouds.

scholarly journals Role of Diurnal Warm Layers in the Diurnal Cycle of Convection over the Tropical Indian Ocean during MISMO

2010 ◽  
Vol 138 (6) ◽  
pp. 2426-2433 ◽  
Author(s):  
H. Bellenger ◽  
Y. N. Takayabu ◽  
T. Ushiyama ◽  
K. Yoneyama
Keyword(s):  
Indian Ocean ◽  
Diurnal Cycle ◽  
Tropical Indian Ocean ◽  
Early Morning ◽  
Heat Fluxes ◽  
Surface Heat Fluxes ◽  
Boundary Layer Processes ◽  
Early Afternoon

Abstract The role of air–sea interaction in the diurnal variations of convective activity during the suppressed and developing stages of an intraseasonal convective event is analyzed using in situ observations from the Mirai Indian Ocean cruise for the Study of the Madden–Julian oscillation (MJO)-convection Onset (MISMO) experiment. For the whole period, convection shows a clear average diurnal cycle with a primary maximum in the early morning and a secondary one in the afternoon. Episodes of large diurnal sea surface temperature (SST) variations are observed because of diurnal warm layer (DWL) formation. When no DWL is observed, convection exhibits a diurnal cycle characterized by a maximum in the early morning, whereas when DWL forms, convection increases around noon and peaks in the afternoon. Boundary layer processes are found to control the diurnal evolution of convection. In particular, when DWL forms, the change in surface heat fluxes can explain the decrease of convective inhibition and the intensification of the convection during the early afternoon.

scholarly journals Effects of the diurnal cycle in solar radiation on the tropical Indian Ocean mixed layer variability during wintertime Madden-Julian Oscillations

2013 ◽  
Vol 118 (10) ◽  
pp. 4945-4964 ◽  
Author(s):  
Yuanlong Li ◽  
Weiqing Han ◽  
Toshiaki Shinoda ◽  
Chunzai Wang ◽  
Ren-Chieh Lien ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Solar Radiation ◽  
Mixed Layer ◽  
Diurnal Cycle ◽  
Tropical Indian Ocean ◽  
Ocean Mixed Layer
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