scholarly journals Geographical distribution and interseasonal variability of tropical deep convection: UARS MLS observations and analyses

2004 ◽  
Vol 109 (D3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jonathan H. Jiang ◽  
Bin Wang ◽  
Kenshi Goya ◽  
Klemens Hocke ◽  
Stephen D. Eckermann ◽  
...  
Keyword(s):  
Geographical Distribution ◽  
Deep Convection ◽  
Tropical Deep Convection ◽  
Interseasonal Variability

Impacts of mineral dust on ice clouds in tropical deep convection systems

2014 ◽  
Vol 143 ◽  
pp. 64-72 ◽  
Author(s):  
Q.-L. Min ◽  
R. Li ◽  
B. Lin ◽  
E. Joseph ◽  
V. Morris ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Deep Convection ◽  
Ice Clouds ◽  
Tropical Deep Convection

Effect of Surface Fluxes versus Radiative Heating on Tropical Deep Convection

2015 ◽  
Vol 72 (9) ◽  
pp. 3378-3388 ◽  
Author(s):  
Usama Anber ◽  
Shuguang Wang ◽  
Adam Sobel
Keyword(s):  
Large Scale ◽  
Multiple Equilibria ◽  
Initial Conditions ◽  
Deep Convection ◽  
Surface Fluxes ◽  
Radiative Heating ◽  
Net Energy ◽  
Wide Range ◽  
Tropical Deep Convection ◽  
Gross Moist Stability

Abstract The effects of turbulent surface fluxes and radiative heating on tropical deep convection are compared in a series of idealized cloud-system-resolving simulations with parameterized large-scale dynamics. Two methods of parameterizing the large-scale dynamics are used: the weak temperature gradient (WTG) approximation and the damped gravity wave (DGW) method. Both surface fluxes and radiative heating are specified, with radiative heating taken as constant in the vertical in the troposphere. All simulations are run to statistical equilibrium. In the precipitating equilibria, which result from sufficiently moist initial conditions, an increment in surface fluxes produces more precipitation than an equal increment of column-integrated radiative heating. This is straightforwardly understood in terms of the column-integrated moist static energy budget with constant normalized gross moist stability. Under both large-scale parameterizations, the gross moist stability does in fact remain close to constant over a wide range of forcings, and the small variations that occur are similar for equal increments of surface flux and radiative heating. With completely dry initial conditions, the WTG simulations exhibit hysteresis, maintaining a dry state with no precipitation for a wide range of net energy inputs to the atmospheric column. The same boundary conditions and forcings admit a rainy state also (for moist initial conditions), and thus multiple equilibria exist under WTG. When the net forcing (surface fluxes minus radiative heating) is increased enough that simulations that begin dry eventually develop precipitation, the dry state persists longer after initialization when the surface fluxes are increased than when radiative heating is increased. The DGW method, however, shows no multiple equilibria in any of the simulations.

scholarly journals Initial Tendencies of Cloud Regimes in the Met Office Unified Model

2008 ◽  
Vol 21 (4) ◽  
pp. 833-840 ◽  
Author(s):  
K. D. Williams ◽  
M. E. Brooks
Keyword(s):  
Initial Temperature ◽  
Climate Model ◽  
Deep Convection ◽  
Weather Prediction ◽  
Horizontal Resolution ◽  
Systematic Bias ◽  
Cloud Regime ◽  
Tropical Deep Convection ◽  
Cloud Regimes ◽  
Temperature Tendency

Abstract The Met Office unified forecast–climate model is used to compare the properties of simulated climatological cloud regimes with those produced in short-range forecasts initialized from operational analyses. The regimes are defined as principal clusters of joint cloud-top pressure–optical depth histograms. In general, the cloud regime properties are found to be similar at all forecast times, including the climatological mean. This suggests that weaknesses in the representation of fast local processes are responsible for errors in the simulation of the cloud regimes. The increased horizontal resolution of the model used for numerical weather prediction generally has little impact on the cloud regimes, although the simulation of tropical shallow cumulus is improved, while the relative frequency of tropical deep convection and cirrus compare less favorably with observations. Analysis of the initial temperature tendency profiles for each cloud regime indicates that some of the initial temperature tendency, which leads to a systematic bias in the model climatology, is associated with a particular cloud regime.

Local Time- and Space Scales of Organized Tropical Deep Convection

2002 ◽  
Vol 15 (19) ◽  
pp. 2775-2790 ◽  
Author(s):  
Lucrezia Ricciardulli ◽  
Prashant D. Sardeshmukh
Keyword(s):  
Local Time ◽  
Deep Convection ◽  
Time And Space ◽  
Tropical Deep Convection

scholarly journals Entrainment versus Dilution in Tropical Deep Convection

2017 ◽  
Vol 74 (11) ◽  
pp. 3725-3747 ◽  
Author(s):  
Walter M. Hannah
Keyword(s):  
Thermal Model ◽  
Deep Convection ◽  
Negative Relationship ◽  
Tropical Environment ◽  
Moist Air ◽  
Convective Parameterization ◽  
The Core ◽  
Tropical Deep Convection ◽  
Source Sink

Abstract The distinction between entrainment and dilution is investigated with cloud-resolving simulations of deep convection in a tropical environment. A method for estimating the rate of dilution by entrainment and detrainment is presented and calculated for a series of bubble simulations with a range of initial radii. Entrainment generally corresponds to dilution of convection, but the two quantities are not well correlated. Core dilution by entrainment is significantly reduced by the presence of a shell of moist air around the core. Dilution by entrainment also increases with increasing updraft velocity but only for sufficiently strong updrafts. Entrainment contributes significantly to the total net dilution, but detrainment and the various source/sink terms play large roles depending on the variable in question. Detrainment has a concentrating effect on average that balances out the dilution by entrainment. The experiments are also used to examine whether entrainment or dilution scale with cloud radius. The results support a weak negative relationship for dilution but not for entrainment. The sensitivity to resolution is briefly discussed. A toy Lagrangian thermal model is used to demonstrate the importance of the cloud shell as a thermodynamic buffer to reduce the dilution of the core by entrainment. The results suggest that explicit cloud heterogeneity may be a useful consideration for future convective parameterization development.

scholarly journals Tropical deep convection and density current signature in surface pressure: comparison between WRF model simulations and infrasound measurements

2013 ◽  
Vol 13 (6) ◽  
pp. 15993-16046 ◽  
Author(s):  
L. Costantino ◽  
P. Heinrich
Keyword(s):  
Wind Speed ◽  
Surface Pressure ◽  
High Frequency ◽  
Ivory Coast ◽  
Deep Convection ◽  
Real Case ◽  
Density Current ◽  
Model Simulations ◽  
Tropical Deep Convection

Abstract. Deep convection is a major atmospheric transport process in the tropics, affecting the global weather and the climate system. In the framework of the ARISE (Atmospheric dynamics Research InfraStructure in Europe) project, we combine model simulations of tropical deep convection with in-situ ground measurements, from a IMS (International Monitoring System) infrasound station in Ivory Coast, to analyse the effects of density current propagation. The WRF (Weather Research and Forecasting) model is firstly run in a simplified (referred to as "idealized case") and highly resolved configuration, to explicitly account for convective dynamics. Then, a coarser threedimensional simulation (referred to as "real") is nudged towards meteorological re-analysis data, to compare the real case with the idealized model and in-situ observations. In the 2-D run, the evolution of a deep convective cloud generates a density current, that moves outward up to 30 km away from storm center. The increase in surface density (up to 18 g m−3 larger than surrounding air) is mostly due to the sudden temperature decrease (down to −2 °C, with respect to domain averaged value), from diabatic cooling by rain evaporation near ground level. It is accompanied by a dramatic decrease in relative humidity (down to −50%), buoyancy (down to −0.08 m s−2), equivalent potential temperature (25 °C lower than the PBL) and the rapid enhancement of horizontal wind speed (up to 15 m s−2). If temperature and density changes are strong enough, surface pressure gets largely affected and high frequency disturbances (up to several tens of Pa) can be detected, at the leading edges of density current. The moister and warmer air of subcloud layer is lifted up and replaced by a more stable flow. The resulting thermodynamical instabilities are shown to play a key role in triggering new convection. If the initial environment is sufficiently unstable, they can give rise to continuous updrafts that may lead to the transition from single-cell to multi-cell cloud systems, even without the presence of an initial wind shear. The overall consistence and similarity between idealized and real simulation, and the good agreement of real case with in-situ retrievals of temperature, pressure, wind speed and direction, seem to confirm the ability of 2-D and 3-D model to well reproduce convective dynamics. Surface pressure disturbances, simulated in both idealized and real cases as a consequence of cold pool propagation, are very similar to those recorded in Ivory Coast. Present results stress the direct link between mesoscale convective system activity and high-frequency surface pressure variations, suggesting the possibility of developing a new method for real-time rainstorm tracking, based on the ground-based infrasound monitoring of pressure field.

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