scholarly journals A Density Current Parameterization Coupled with Emanuel’s Convection Scheme. Part II: 1D Simulations

2010 ◽  
Vol 67 (4) ◽  
pp. 898-922 ◽  
Author(s):  
Jean-Yves Grandpeix ◽  
Jean-Philippe Lafore ◽  
Frédérique Cheruy
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Density Current ◽  
Convective Heating ◽  
Convection Scheme ◽  
Case Definitions ◽  
Convective Systems ◽  
Cold Pools ◽  
Single Column ◽  
Basic Parameters

Abstract The density current parameterization coupled with Emanuel’s convection scheme, described in Part I of this series of papers, is tested in a single-column framework for continental and maritime convective systems. The case definitions and reference simulations are provided by cloud-resolving models (CRMs). For both cases, the wake scheme yields cold pools with temperature and humidity differences relative to the environment in reasonable agreement with observations (with wake depth on the order of 2 km over land and 1 km over ocean). The coupling with the convection scheme yields convective heating, drying, and precipitation similar to those simulated by the CRM. Thus, the representation of the action of the wakes on convection in terms of available lifting energy (ALE) and available lifting power (ALP) appears satisfactory. The sensitivity of the wake–convection system to the basic parameters of the parameterization is widely explored. A range of values for each parameter is recommended to help with implementing the scheme in a full-fledged general circulation model.

scholarly journals Dynamical Effects of Convective Momentum Transports on Global Climate Simulations

2008 ◽  
Vol 21 (2) ◽  
pp. 180-194 ◽  
Author(s):  
Xiaoliang Song ◽  
Xiaoqing Wu ◽  
Guang Jun Zhang ◽  
Raymond W. Arritt
Keyword(s):  
General Circulation ◽  
Global Climate ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Convective Heating ◽  
Experimental Setup ◽  
Convection Scheme ◽  
Model Calculations ◽  
Geostrophic Balance ◽  
Climate Simulations

Abstract Dynamical effects of convective momentum transports (CMT) on global climate simulations are investigated using the NCAR Community Climate Model version 3 (CCM3). To isolate the dynamical effects of the CMT, an experimental setup is proposed in which all physical parameterizations except for the deep convection scheme are replaced with idealized forcing. The CMT scheme is incorporated into the convection scheme to calculate the CMT forcing, which is used to force the momentum equations, while convective temperature and moisture tendencies are not passed into the model calculations in order to remove the physical feedback between convective heating and wind fields. Excluding the response of complex physical processes, the model with the experimental setup contains a complete dynamical core and the CMT forcing. Comparison between two sets of 5-yr simulations using this idealized general circulation model (GCM) shows that the Hadley circulation is enhanced when the CMT forcing is included, in agreement with previous studies that used full GCMs. It suggests that dynamical processes make significant contributions to the total response of circulation to CMT forcing in the full GCMs. The momentum budget shows that the Coriolis force, boundary layer friction, and nonlinear interactions of velocity fields affect the responses of zonal wind field, and the adjustment of circulation follows an approximate geostrophic balance. The adjustment mechanism of meridional circulation in response to ageostrophic CMT forcing is examined. It is found that the strengthening of the Hadley circulation is an indirect response of the meridional wind to the zonal CMT forcing through the Coriolis effect, which is required for maintaining near-geostrophic balance.

scholarly journals Variability of Tropical Cyclone Frequency Over the Western North Pacific in 2018–2020

2021 ◽  
Vol 3 ◽  
Author(s):  
Tomomichi Ogata ◽  
Yuya Baba
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Circulation Model ◽  
Atmospheric Variability ◽  
Convection Scheme ◽  
Planetary Scale ◽  
Ensemble Simulations ◽  
Potential Index

In this study, we examine the tropical cyclone (TC) activity over the western North Pacific (WNP) in 2018–2020 and its relationship with planetary scale convection and circulation anomalies, which play an important role for TC genesis. To determine the sea surface temperature (SST)-forced atmospheric variability, atmospheric general circulation model (AGCM) ensemble simulations are executed along with the observed SST. For AGCM experiments, we use two different convection schemes to examine uncertainty in convective parameterization and robustness of simulated atmospheric response. The observed TC activity and genesis potential demonstrated consistent features. In our AGCM ensemble simulations, the updated convection scheme improves the simulation ability of observed genesis potential as well as planetary scale convection and circulation features, e.g., in September–October–November (SON), a considerable increase in the genesis potential index over the WNP in SON 2018, WNP in SON 2019, and South China Sea (SCS) in SON 2020, which were not captured in the Emanuel scheme, have been simulated in the updated convection scheme.

scholarly journals Essential Ingredients to the Dynamics of Westerly Wind Bursts

2019 ◽  
Vol 32 (17) ◽  
pp. 5549-5565 ◽  
Author(s):  
Minmin Fu ◽  
Eli Tziperman
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Basic Mechanism ◽  
Surface Heat ◽  
Convective Heating ◽  
Short Time Scale ◽  
Westerly Wind ◽  
Atmospheric Phenomena ◽  
Wind Bursts ◽  
Westerly Wind Bursts

Abstract Westerly wind bursts (WWBs) are brief, anomalously westerly winds in the tropical Pacific that play a role in the dynamics of ENSO through their forcing of ocean Kelvin waves. They have been associated with atmospheric phenomena such as tropical cyclones, the MJO, and convectively coupled Rossby waves, yet their basic mechanism is not yet well understood. We study WWBs using an aquaplanet general circulation model, and find that eastward-propagating convective heating plays a key role in the generation of model WWBs, consistent with previous studies. Furthermore, wind-induced surface heat exchange (WISHE) acts on a short time scale of about two days to dramatically amplify the model WWB winds near the peak of the event. On the other hand, it is found that radiation feedbacks (i.e., changes in the net radiative anomalies accompanying westerly wind bursts) are not essential for the development of WWBs, and act as a weak negative feedback on WWBs and their associated convection. Similarly, sensible surface heat flux anomalies are not found to have an effect on the development of model WWBs.

scholarly journals The E3SM version 1 single-column model

2020 ◽  
Vol 13 (9) ◽  
pp. 4443-4458
Author(s):  
Peter A. Bogenschutz ◽  
Shuaiqi Tang ◽  
Peter M. Caldwell ◽  
Shaocheng Xie ◽  
Wuyin Lin ◽  
...  
Keyword(s):  
General Circulation ◽  
Model Development ◽  
Circulation Model ◽  
System Model ◽  
Earth System ◽  
Efficient Tool ◽  
Column Model ◽  
Community Atmosphere Model ◽  
Single Column ◽  
Single Column Model

Abstract. The single-column model (SCM) functionality of the Energy Exascale Earth System Model version 1 (E3SMv1) is described in this paper. The E3SM SCM was adopted from the SCM used in the Community Atmosphere Model (CAM) but has evolved significantly since then. We describe changes made to the aerosol specification in the SCM, idealizations, and developments made so that the SCM uses the same dynamical core as the full general circulation model (GCM) component. Based on these changes, we describe and demonstrate the seamless capability to “replay” a GCM column using the SCM. We give an overview of the E3SM case library and briefly describe which cases may serve as useful proxies for replicating and investigate some long-standing biases in the full GCM runs while demonstrating that the E3SM SCM is an efficient tool for both model development and evaluation.

Using the Stochastic Multicloud Model to Improve Tropical Convective Parameterization: A Paradigm Example

2012 ◽  
Vol 69 (3) ◽  
pp. 1080-1105 ◽  
Author(s):  
Yevgeniy Frenkel ◽  
Andrew J. Majda ◽  
Boualem Khouider
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Tropical Convection ◽  
Convective Parameterization ◽  
Convective Systems ◽  
Squall Lines ◽  
Walker Cell ◽  
Single Column ◽  
Mesoscale Convective ◽  
Coarse Grids

Abstract Despite recent advances in supercomputing, current general circulation models (GCMs) poorly represent the variability associated with organized tropical convection. A stochastic multicloud convective parameterization based on three cloud types (congestus, deep, and stratiform), introduced recently by Khouider, Biello, and Majda in the context of a single column model, is used here to study flows above the equator without rotation effects. The stochastic model dramatically improves the variability of tropical convection compared to the conventional moderate- and coarse-resolution paradigm GCM parameterizations. This increase in variability comes from intermittent coherent structures such as synoptic and mesoscale convective systems, analogs of squall lines and convectively coupled waves seen in nature whose representation is improved by the stochastic parameterization. Furthermore, simulations with a sea surface temperature (SST) gradient yield realistic mean Walker cell circulation with plausible high variability. An additional feature of the present stochastic parameterization is a natural scaling of the model from moderate to coarse grids that preserves the variability and statistical structure of the coherent features. These results systematically illustrate, in a paradigm model, the benefits of using the stochastic multicloud framework to improve deterministic parameterizations with clear deficiencies.

A Second-Order Closure Turbulence Model: New Heat Flux Equations and No Critical Richardson Number

2020 ◽  
Vol 77 (8) ◽  
pp. 2743-2759
Author(s):  
Y. Cheng ◽  
V. M. Canuto ◽  
A. M. Howard ◽  
A. S. Ackerman ◽  
M. Kelley ◽  
...  
Keyword(s):  
Heat Flux ◽  
Turbulence Model ◽  
Richardson Number ◽  
General Circulation ◽  
Circulation Model ◽  
Second Order ◽  
Boundary Layer Height ◽  
Stable Conditions ◽  
Single Column ◽  
Critical Richardson Number

Abstract We formulate a new second-order closure turbulence model by employing a recent closure for the pressure–temperature correlation at the equation level. As a result, we obtain new heat flux equations that avoid the long-standing issue of a finite critical Richardson number. The new, structurally simpler model improves on the Mellor–Yamada and Galperin et al. models; a key feature includes enhanced mixing under stable conditions facilitating agreement with observational, experimental, and high-resolution numerical datasets. The model predicts a planetary boundary layer height deeper than predicted by models with low critical Richardson numbers, as demonstrated in single-column model runs of the GISS ModelE general circulation model.

scholarly journals Influences of the Pacific–Japan Teleconnection Pattern on Synoptic-Scale Variability in the Western North Pacific

2014 ◽  
Vol 27 (1) ◽  
pp. 140-154 ◽  
Author(s):  
Richard C. Y. Li ◽  
Wen Zhou ◽  
Tim Li
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Western North Pacific ◽  
Wave Train ◽  
Circulation Model ◽  
Environmental Parameters ◽  
Teleconnection Pattern ◽  
Convective Heating ◽  
Synoptic Scale ◽  
The Pacific

Abstract This study investigates the influences of the Pacific–Japan (PJ) teleconnection pattern on synoptic-scale variability (SSV) in the western North Pacific (WNP). The PJ pattern exhibits salient intraseasonal variations, with a dominant peak at 10–50 days. During positive PJ phases, strengthened SSV is found in the WNP, with a much stronger and better organized synoptic wave train structure. Such a synoptic-scale wave train, however, is greatly weakened during negative PJ phases. Examination of the vertical profiles of the observational data suggests that environmental parameters are generally more (less) favorable for the growth of synoptic disturbances under positive (negative) PJ conditions. Observational results are further verified with an anomaly atmospheric general circulation model, which reveals faster (slower) growth of the synoptic-scale wave train when the environmental anomalies associated with positive (negative) PJ phases are incorporated into the summer mean state of the model. In addition, sensitivity experiments indicate that thermodynamic parameters of the planetary boundary layer (PBL) play a determining role in controlling the development of synoptic disturbances in the WNP. The increase (decrease) in background PBL moisture during positive (negative) PJ phases enhances (suppresses) perturbation moisture convergence and thus the convective heating associated with SSV, leading to strengthened (weakened) synoptic-scale activity in the WNP. Serving as potential seed disturbances for cyclogenesis, the strengthened (weakened) synoptic-scale activity may also contribute to the enhancement (suppression) in intraseasonal TC frequency during positive (negative) PJ phases.

scholarly journals Deep Convection Triggering by Boundary Layer Thermals. Part II: Stochastic Triggering Parameterization for the LMDZ GCM

2014 ◽  
Vol 71 (2) ◽  
pp. 515-538 ◽  
Author(s):  
Nicolas Rochetin ◽  
Jean-Yves Grandpeix ◽  
Catherine Rio ◽  
Fleur Couvreux
Keyword(s):  
General Circulation ◽  
Deep Convection ◽  
Circulation Model ◽  
Cloud Base ◽  
Trade Wind ◽  
Shallow Convection ◽  
Model Framework ◽  
Main Hypothesis ◽  
Single Column ◽  
The Impact

Abstract This paper presents a stochastic triggering parameterization for deep convection and its implementation in the latest standard version of the Laboratoire de Météorologie Dynamique–Zoom (LMDZ) general circulation model: LMDZ5B. The derivation of the formulation of this parameterization and the justification, based on large-eddy simulation results, for the main hypothesis was proposed in Part I of this study. Whereas the standard triggering formulation in LMDZ5B relies on the maximum vertical velocity within a mean bulk thermal, the new formulation presented here (i) considers a thermal size distribution instead of a bulk thermal, (ii) provides a statistical lifting energy at cloud base, (iii) proposes a three-step trigger (appearance of clouds, inhibition crossing, and exceeding of a cross-section threshold), and (iv) includes a stochastic component. Here the complete implementation is presented, with its coupling to the thermal model used to treat shallow convection in LMDZ5B. The parameterization is tested over various cases in a single-column model framework. A sensitivity study to each parameter introduced is also carried out. The impact of the new triggering is then evaluated in the single-column version of LMDZ on several case studies and in full 3D simulations. It is found that the new triggering (i) delays deep convection triggering, (ii) suppresses it over oceanic trade wind cumulus zones, (iii) increases the low-level cloudiness, and (iv) increases the convective variability. The scale-aware nature of this parameterization is also discussed.

scholarly journals Precipitation in Boreal Summer Simulated by a GCM with Two Convective Parameterization Schemes: Implications of the Intraseasonal Oscillation for Dynamic Seasonal Prediction

2010 ◽  
Vol 23 (10) ◽  
pp. 2801-2816 ◽  
Author(s):  
Suhee Park ◽  
Song-You Hong ◽  
Young-Hwa Byun
Keyword(s):  
General Circulation ◽  
Intraseasonal Oscillation ◽  
Circulation Model ◽  
Seasonal Prediction ◽  
Boreal Summer ◽  
Convection Scheme ◽  
Seasonal Predictability ◽  
Model Framework ◽  
Wave Characteristics ◽  
Skill Scores

Abstract In this paper, the intraseasonal oscillation (ISO) and its possible link to dynamical seasonal predictability within a general circulation model framework is investigated. Two experiments with different convection scheme algorithms, namely, the simplified Arakawa–Schubert (SAS) and the relaxed Arakawa–Schubert (RAS) convection algorithms, were designed to compare seasonal simulations from 1979 to 2002 on a seasonal model intercomparison project (SMIP)-type simulation test bed. Furthermore, the wave characteristics (wave intensity, period, and propagation) of the simulated ISO signal provided by the model with two different convection schemes for extended boreal summers from 1997 to 2004 were compared to the observational ISO signal. Precipitation in the boreal summer was fairly well simulated by the model irrespective of the convection scheme used, but the RAS run outperformed the SAS run with respect to tabulated skill scores. Decomposition of the interannual variability of boreal summer precipitation based on observations and model results demonstrates that the seasonal predictability of precipitation is dominated by the intraseasonal component over the warm pool area and the SST-forced signal over the equatorial Pacific Ocean, implying that the seasonal mean anomalies are more predictable under active ISO conditions as well as strong ENSO conditions. Comparison of the ISO simulations with the observations revealed that the main features, such as the intensity of precipitation variance in the intraseasonal time scale and the evolution of propagating ISOs, were reproduced fairly well by the model; however, the wave characteristics associated with the ISO signals were better captured by the experiment with the RAS scheme than the SAS scheme. This study further suggests that accurate simulation of the ISO can improve the seasonal predictability of dynamical seasonal prediction systems.

Do Planetary Wave Dynamics Contribute to Equable Climates?

2011 ◽  
Vol 24 (9) ◽  
pp. 2391-2404 ◽  
Author(s):  
Sukyoung Lee ◽  
Steven Feldstein ◽  
David Pollard ◽  
Tim White
Keyword(s):  
High Latitude ◽  
General Circulation ◽  
Rossby Waves ◽  
Circulation Model ◽  
Warm Pool ◽  
The Arctic ◽  
Convective Heating ◽  
Co2 Level ◽  
Early Cenozoic ◽  
Arctic Surface

Abstract Viable explanations for equable climates of the Cretaceous and early Cenozoic (from about 145 to 50 million years ago), especially for the above-freezing temperatures detected for high-latitude continental winters, have been a long-standing challenge. In this study, the authors suggest that enhanced and localized tropical convection, associated with a strengthened paleo–warm pool, may contribute toward high-latitude warming through the excitation of poleward-propagating Rossby waves. This warming takes place through the poleward heat flux and an overturning circulation that accompany the Rossby waves. This mechanism is tested with an atmosphere–mixed layer ocean general circulation model (GCM) by imposing idealized localized heating and compensating cooling, a heating structure that mimics the effect of warm-pool convective heating. The localized tropical heating is indeed found to contribute to a warming of the Arctic during the winter. Within the range of 0–150 W m−2 for the heating intensity, the average rate for the zonal mean Arctic surface warming is 0.8°C per (10 W m−2) increase in the heating for the runs with an atmospheric CO2 level of 4 × PAL (Preindustrial Atmospheric Level, 1 PAL = 280 ppmv), the Cretaceous and early Cenozoic values considered for this study. This rate of warming for the Arctic is lower in model runs with 1 × PAL CO2, which show an increase of 0.3°C per (10 W m−2). Further increase of the heating intensity beyond 150 W m−2 produces little change in the Arctic surface air temperature. This saturation behavior is interpreted as being a result of nonlinear wave–wave interaction, which leads to equatorward wave refraction. Under the 4 × PAL CO2 level, raising the heating from 120 W m−2 (estimated warm-pool convective heating value for the present-day climate) to 150 and 180 W m −2 (estimated values for the Cretaceous and early Cenozoic) produces a warming of 4°–8°C over northern Siberia and the adjacent Arctic Ocean. Relative to the warming caused by a quadrupling of CO2 alone, this temperature increase accounts for about 30% of the warming over this region. The possible influence of warm-pool convective heating on the present-day Arctic is also discussed.

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