scholarly journals Effect of shallow cumulus convection on the eastern Pacific climate in a coupled model

2006 ◽  
Vol 33 (17) ◽  
Author(s):  
Simon P. de Szoeke ◽  
Yuqing Wang ◽  
Shang-Ping Xie ◽  
Toru Miyama
Keyword(s):  
Coupled Model ◽  
Eastern Pacific ◽  
Cumulus Convection ◽  
Shallow Cumulus

scholarly journals The Environment of Precipitating Shallow Cumulus Convection

2009 ◽  
Vol 66 (7) ◽  
pp. 1962-1979 ◽  
Author(s):  
Louise Nuijens ◽  
Bjorn Stevens ◽  
A. Pier Siebesma
Keyword(s):  
Surface Flux ◽  
Airborne Lidar ◽  
Trade Wind ◽  
Lidar Data ◽  
Cumulus Convection ◽  
Total Precipitation ◽  
Quantitative Estimates ◽  
Shallow Cumulus ◽  
Reflectivity Data ◽  
Airborne Lidar Data

Abstract Quantitative estimates of precipitation in a typical undisturbed trade wind region are derived from 2 months of radar reflectivity data and compared to the meteorological environment determined from soundings, surface flux, and airborne-lidar data. Shallow precipitation was ubiquitous, covering on average about 2% of the region and contributing to at least half of the total precipitation. Echo fractions on the scale of the radar domain range between 0% and 10% and vary greatly within a period from a few hours to a day. Variability in precipitation relates most strongly to variability in humidity and the zonal wind speed, although greater inversion heights and deeper clouds are also evident at times of more rain. The analysis herein suggests that subtle fluctuations in both the strength of the easterlies and in subsidence play a major role in regulating humidity and hence precipitation, even within a given meteorological regime (here, the undisturbed trades).

Responses of Shallow Cumulus Convection to Large-Scale Temperature and Moisture Perturbations: A Comparison of Large-Eddy Simulations and a Convective Parameterization Based on Stochastically Entraining Parcels

2012 ◽  
Vol 69 (6) ◽  
pp. 1936-1956 ◽  
Author(s):  
Ji Nie ◽  
Zhiming Kuang
Keyword(s):  
Large Scale ◽  
Potential Temperature ◽  
Large Eddy Simulations ◽  
Cumulus Parameterization ◽  
Temperature Perturbation ◽  
Cumulus Convection ◽  
Positive Temperature ◽  
Shallow Cumulus ◽  
Scale Temperature ◽  
Large Eddy

Abstract Responses of shallow cumuli to large-scale temperature/moisture perturbations are examined through diagnostics of large-eddy simulations (LESs) of the undisturbed Barbados Oceanographic and Meteorological Experiment (BOMEX) case and a stochastic parcel model. The perturbations are added instantaneously and allowed to evolve freely afterward. The parcel model reproduces most of the changes in the LES-simulated cloudy updraft statistics in response to the perturbations. Analyses of parcel histories show that a positive temperature perturbation forms a buoyancy barrier, which preferentially eliminates parcels that start with lower equivalent potential temperature or have experienced heavy entrainment. Besides the amount of entrainment, the height at which parcels entrain is also important in determining their fate. Parcels entraining at higher altitudes are more likely to overcome the buoyancy barrier than those entraining at lower altitudes. Stochastic entrainment is key for the parcel model to reproduce the LES results. Responses to environmental moisture perturbations are quite small compared to those to temperature perturbations because changing environmental moisture is ineffective in modifying buoyancy in the BOMEX shallow cumulus case. The second part of the paper further explores the feasibility of a stochastic parcel–based cumulus parameterization. Air parcels are released from the surface layer and temperature/moisture fluxes effected by the parcels are used to calculate heating/moistening tendencies due to both cumulus convection and boundary layer turbulence. Initial results show that this conceptually simple parameterization produces realistic convective tendencies and also reproduces the LES-simulated mean and variance of cloudy updraft properties, as well as the response of convection to temperature/moisture perturbations.

An eddy-diffusivity/mass-flux parametrization for dry and shallow cumulus convection

2004 ◽  
Vol 130 (604) ◽  
pp. 3365-3383 ◽  
Author(s):  
P.M.M. Soares ◽  
P.M.A. Miranda ◽  
A.P. Siebesma ◽  
J. Teixeira
Keyword(s):  
Mass Flux ◽  
Eddy Diffusivity ◽  
Cumulus Convection ◽  
Shallow Cumulus

scholarly journals A Multiparcel Model for Shallow Cumulus Convection

2002 ◽  
Vol 59 (10) ◽  
pp. 1655-1668 ◽  
Author(s):  
R. A. J. Neggers ◽  
A. P. Siebesma ◽  
H. J. J. Jonker
Keyword(s):  
Cumulus Convection ◽  
Shallow Cumulus

Mechanism of the Double peaked El Nino

2020 ◽  
Author(s):  
Na-Yeon Shin ◽  
Jong-Seong Kug ◽  
Felicity S. McCormack ◽  
Neil J. Holbrook
Keyword(s):  
General Circulation ◽  
Heat Budget ◽  
Coupled Model ◽  
General Circulation Models ◽  
Warm Pool ◽  
Eastern Pacific ◽  
Dynamical Analysis ◽  
Cold Tongue ◽  
Central Pacific ◽  
Sst Anomalies

<p>   In the past decades, our understanding of the ENSO phenomenon increased steadily. Especially, one of the most interesting topics was the El Niño type because of the different global impacts. The classic classification is the two types of the El Niño and there are various terms to refer this. The conventional El Niño is called the Cold tongue El Niño or the Eastern pacific El Niño. And the other type of the El Niño is called the Warm pool El Niño, the Central pacific El Niño, the El Niño Modoki or the dateline El Niño. However, in Coupled Model Intercomparison Project version 5 (CMIP5) Coupled General Circulation Models (CGCMs) results, those have been shown the Double peaked El Niño events which are the new type of the El Niño due to the climatological cold tongue bias. Double peaked El Niño events are defined as a positive sea surface temperature anomalies are separated into two centers (in Western and Eastern Pacific) and grow individually and simultaneously, and the peak of SST anomalies exceeds the threshold.</p><p>   Double peaked El Niño events are found in not only the models, but also the observations. But there are no dynamical analysis of observations. In this study, the mechanism giving rise to Double peaked El Niño in observation is examined by analyzing the mixed layer heat budget equation and comparing with the Warm Pool El Niño and Cold tongue El Niño.</p><p>   The warm SST anomalies of the western peak and the eastern peak are caused by different dynamic mechanism. Western peaks of Double peaked El Niño are similar to the Warm Pool El Niño. Those can be developed by Zonal advection feedback terms and negative anomalous wind speed, whereas eastern peaks of Double peaked El Niño are different from Warm pool El Niño. Thermocline feedback term considerably contribute to the occurrence of eastern peak. Differences of intensity of the precipitation(4-8N, 195-225E) derive other significant differences of the zonal wind stress(5S-5N, 170-200E), sea level(5S-5N, 230-250E) and zonal current(5S-5N, 230-250E). Thus, the process above can induce the eastern peak of the Double peaked El Niño.</p>

scholarly journals The role of 1-D and 3-D radiative heating in the organization of shallow cumulus convection and the formation of cloud streets

2017 ◽  
Vol 17 (21) ◽  
pp. 13317-13327 ◽  
Author(s):  
Fabian Jakub ◽  
Bernhard Mayer
Keyword(s):  
Radiative Transfer ◽  
Surface Heat ◽  
Surface Fluxes ◽  
Radiative Heating ◽  
Horizontal Wind ◽  
Parameter Study ◽  
Cumulus Convection ◽  
Radiative Feedback ◽  
Wind Speeds ◽  
Shallow Cumulus

Abstract. The formation of shallow cumulus cloud streets was historically attributed primarily to dynamics. Here, we focus on the interaction between radiatively induced surface heterogeneities and the resulting patterns in the flow. Our results suggest that solar radiative heating has the potential to organize clouds perpendicular to the sun's incidence angle. To quantify the extent of organization, we performed a high-resolution large-eddy simulation (LES) parameter study. We varied the horizontal wind speed, the surface heat capacity, the solar zenith and azimuth angles, and radiative transfer parameterizations (1-D and 3-D). As a quantitative measure we introduce a simple algorithm that provides a scalar quantity for the degree of organization and the alignment. We find that, even in the absence of a horizontal wind, 3-D radiative transfer produces cloud streets perpendicular to the sun's incident direction, whereas the 1-D approximation or constant surface fluxes produce randomly positioned circular clouds. Our reasoning for the enhancement or reduction of organization is the geometric position of the cloud's shadow and its corresponding surface fluxes. Furthermore, when increasing horizontal wind speeds to 5 or 10 m s−1, we observe the development of dynamically induced cloud streets. If, in addition, solar radiation illuminates the surface beneath the cloud, i.e., when the sun is positioned orthogonally to the mean wind field and the solar zenith angle is larger than 20°, the cloud-radiative feedback has the potential to significantly enhance the tendency to organize in cloud streets. In contrast, in the case of the 1-D approximation (or overhead sun), the tendency to organize is weaker or even prohibited because the shadow is cast directly beneath the cloud. In a land-surface-type situation, we find the organization of convection happening on a timescale of half an hour. The radiative feedback, which creates surface heterogeneities, is generally diminished for large surface heat capacities. We therefore expect radiative feedbacks to be strongest over land surfaces and weaker over the ocean. Given the results of this study we expect that simulations including shallow cumulus convection will have difficulties producing cloud streets if they employ 1-D radiative transfer solvers or may need unrealistically high wind speeds to excite cloud street organization.

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