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Impact of Revised Trigger and Closure of the Double-Plume convective parameterization on Precipitation Simulations over East Asia

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Advances in Atmospheric Sciences 2023年第7期40卷 1225-1243页

作者： Xiaohan LI Yi ZHANG Yanluan LIN Xindong PENG Baiquan ZHOU Panmao ZHAI Jian LI State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China 2035 Future Laboratory PIESAT Information Technology Co Ltd.Beijing 100195China Department of Earth System Science Ministry of Education Key Laboratory for Earth System ModelingInstitute for Global Change StudiesTsinghua UniversityBeijing 100084China CMA Earth System modeling and Prediction Center Beijing 100081China

A double-plume convective parameterization scheme is revised to improve the precipitation simulation of a global model(Global-to-Regional Integrated Forecast System;GRIST).The improvement is achieved by considering the effects of large-scale dynamic processes on the trigger of deep *** closure,based on dynamic CAPE,is improved accordingly to allow other processes to consume CAPE under the more restricted convective trigger *** revised convective parameterization is evaluated with a variable-resolution model setup(110–35 km,refined over East Asia).The Atmospheric Model Intercomparison Project(AMIP)simulations demonstrate that the revised convective parameterization substantially delays the daytime precipitation peaks over most land areas,leading to an improved simulated diurnal cycle,evidenced by delayed and less frequent afternoon ***,changes to the threshold of the trigger function yield a small impact on the diurnal amplitude of precipitation because of the consistent setting of dCAPE-based trigger and *** simulated mean precipitation remains reasonable,with some improvements evident along the southern slopes of the Tibetan *** revised scheme increases convective precipitation at the lower levels of the windward slope and reduces the large-scale precipitation over the upper slope,ultimately shifting the rainfall peak southward,which is in better agreement with the observations.

关键词： convective parameterization diurnal cycle of precipitation East Asia variable-resolution modeling

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Implementation and Evaluation of a Double-Plume convective parameterization in NCAR CAM5

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JOURNAL OF CLIMATE 2022年第2期35卷 617-637页

作者： Chu, Wenchao Lin, Yanluan Zhao, Ming Tsinghua Univ Inst Global Change Studies Dept Earth Syst Sci Minist EducKey Lab Earth Syst Modeling Beijing Peoples R China NOAA GFDL Princeton NJ USA

Performance of global climate models (GCMs) is strongly affected by the cumulus parameterization (CP) used. Similar to the approach in GFDL AM4, a double-plume CP, which unifies the deep and shallow convection in one framework, is implemented and tested in the NCAR Community Atmospheric Model version 5 (CAM5). Based on the University of Washington (UW) shallow convection scheme, an additional plume was added to represent the deep convection. The shallow and deep plumes share the same cloud model, but use different triggers, fractional mixing rates, and closures. The scheme was tested in single-column, short-term hindcast, and AMIP simulations. Compared with the default combination of the Zhang-McFarlane scheme and UW scheme in CAM5, the new scheme tends to produce a top-heavy mass flux profile during the active monsoon period in the single-column simulations. The scheme increases the intensity of tropical precipitation, closer to TRMM observations. The new scheme increased subtropical marine boundary layer clouds and high clouds over the deep tropics, both in better agreement with observations. Sensitivity tests indicate that regime-dependent fractional entrainment rates of the deep plume are desired to improve tropical precipitation distribution and upper troposphere temperature. This study suggests that a double-plume approach is a promising way to combine shallow and deep convections in a unified framework.

关键词： Model evaluation/performance Climate models convective parameterization

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Understanding and Improving the Scale Dependence of Trigger Functions for convective parameterization Using Cloud-Resolving Model Data

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JOURNAL OF CLIMATE 2018年第18期31卷 7385-7399页

作者： Song, Fengfei Zhang, Guang J. Univ Calif San Diego Scripps Inst Oceanog San Diego CA 92103 USA Pacific Northwest Natl Lab Atmospher Sci & Global Change Div Richland WA 99352 USA

As the resolution of global climate model increases, whether trigger functions in current convective parameterization schemes still work remains unknown. In this study, the scale dependence of undilute and dilute dCAPE, Bechtold, and heated condensation framework (HCF) triggers is evaluated using the cloud-resolving model (CRM) data. It is found that all these trigger functions are scale dependent, especially for dCAPE-type triggers, with skill scores dropping from similar to 0.6 at the lower resolutions (128, 64, and 32 km) to only similar to 0.1 at 4 km. The average convection frequency decreases from 14.1% at 128 km to 2.3% at 4 km in the CRM data, but it increases rapidly in the dCAPE-type triggers and is almost unchanged in the Bechtold and HCF triggers across resolutions, all leading to large overpredictions at higher resolutions. In the dCAPE-type triggers, the increased frequency is due to the increased rate of dCAPE greater than the threshold (65 J kg(-1) h(-1)) at higher resolutions. The box-and-whisker plots show that the main body of dCAPE in the correct prediction and overprediction can be separated from each other in most resolutions. Moreover, the underprediction is found to be corresponding to the decaying phase of convection. Hence, two modifications are proposed to improve the scale dependence of the undilute dCAPE trigger: 1) increasing the dCAPE threshold and 2) considering convection history, which checks whether there is convection prior to the current time. With these modifications, the skill at 16 km, 8 km, and 4 km can be increased from 0.50, 0.27, and 0.15 to 0.70, 0.61, and 0.53, respectively.

关键词： convective-scale processes Deep convection convective parameterization

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Imprint of the convective parameterization and sea-surface temperature on large-scale convective self-aggregation

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JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS 2017年第2期9卷 1488-1505页

作者： Becker, Tobias Stevens, Bjorn Hohenegger, Cathy Max Planck Inst Meteorol Hamburg Germany

Radiative-convective equilibrium simulations with the general circulation model ECHAM6 are used to explore to what extent the dependence of large-scale convective self-aggregation on sea-surface temperature (SST) is driven by the convective parameterization. Within the convective parameterization, we concentrate on the entrainment parameter and show that large-scale convective self-aggregation is independent of SST when the entrainment rate for deep convection is set to zero or when the convective parameterization is removed from the model. In the former case, convection always aggregates very weakly, whereas in the latter case, convection always aggregates very strongly. With a nontrivial representation of convective entrainment, large-scale convective self-aggregation depends nonmonotonically on SST. For SSTs below 295 K, convection is more aggregated the smaller the SST because large-scale moisture convergence is relatively small, constraining convective activity to regions with high wind-induced surface moisture fluxes. For SSTs above 295 K, convection is more aggregated the higher the SST because entrainment is most efficient in decreasing updraft buoyancy at high SSTs, amplifying the moisture-convection feedback. When halving the entrainment rate, convection is less efficient in reducing updraft buoyancy, and convection is less aggregated, in particular at high SSTs. Despite most early work on self-aggregation highlighted the role of nonconvective processes, we conclude that convective self-aggregation and the global climate state are sensitive to the convective parameterization.

关键词： convection large-scale circulation radiative-convective equilibrium convective self-aggregation convective parameterization entrainment rate

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Improving Trigger Functions for convective parameterization Schemes Using GOAmazon Observations

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JOURNAL OF CLIMATE 2017年第21期30卷 8711-8726页

作者： Song, Fengfei Zhang, Guang J. Univ Calif San Diego Scripps Inst Oceanog La Jolla CA 92093 USA

Using observations from the Green Ocean Amazon (GOAmazon) field campaign, this study aims to improve trigger functions of convection schemes. Results show that the CAPE generation rate (dCAPE)-type triggers are the first tier and that the Bechtold and heated condensation framework (HCF) triggers are a distant second tier. The composite analysis reveals that the undilute dCAPE trigger underpredicts convection when there is bottom-heavy upward motion but overpredicts convection with low-level downward and upperlevel upward motions. The empirical orthogonal function (EOF) analysis on vertical velocity shows that EOF1 (62.65%) exhibits upward motion throughout the troposphere and that EOF2 (28.05%) has lower-level upward motion and upper-level downward motion. Both of them have close relationships with precipitation, indicating the role of vertical velocity in triggering convection. The skill sensitivity analysis shows that the inclusion of 700-hPa upward motion significantly enhances the undilute dCAPE trigger. For the dilute dCAPE trigger, entrainment rate and dCAPE threshold are optimized to improve it. Opposite to dCAPEtype triggers, the Bechtold trigger overemphasizes the low-level vertical velocity and underpredicts the mature and decaying phases of long-lasting convection events. The HCF trigger overemphasizes the nearsurface moist static energy and overlooks the vertical velocity. The performance of dCAPE-type triggers on various convective systems over the Amazon region is examined. The eastward-propagating systems are best represented, with only a few underpredictions in their decaying stages. The weak locally occurring systems and marginal phases of westward-propagating systems are easy to underpredict. The revised dCAPE-type triggers perform better on different convection systems and the diurnal cycle of convection.

关键词： Convection Vertical motion CAPE Empirical orthogonal functions convective parameterization Field experiments

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An Improved convective Ice parameterization for the NASA GISS Global Climate Model and Impacts on Cloud Ice Simulation

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JOURNAL OF CLIMATE 2017年第1期30卷 317-336页

作者： Elsaesser, Gregory S. Del Genio, Anthony D. Jiang, Jonathan H. Van Lier-Walqui, Marcus Columbia Univ Dept Appl Phys & Math New York NY USA NASA Goddard Inst Space Studies 2880 Broadway New York NY 10025 USA CALTECH Jet Prop Lab Pasadena CA USA Columbia Univ Ctr Climate Syst Res New York NY USA

Partitioning of convective ice into precipitating and detrained condensate presents a challenge for GCMs since partitioning depends on the strength and microphysics of the convective updraft. It is an important issue because detrainment of ice from updrafts influences the development of stratiform anvils, impacts radiation, and can affect GCM climate sensitivity. Recent studies have shown that the CMIP5 configurations of the Goddard Institute for Space Studies (GISS) GCM simulated upper-tropospheric ice water content (IWC) that exceeded an estimated upper bound by a factor of 2. Partly in response to this bias, a new GCM parameterization of convective cloud ice has been developed that incorporates new ice particle fall speeds and convective outflow particle size distributions (PSDs) from the NASA African Monsoon Multidisciplinary Analyses (NAMMA), NASA Tropical Composition, Cloud and Climate Coupling (TC4), DOE ARM-NASA Midlatitude Continental convective Clouds Experiment (MC3E), and DOE ARM Small Particles in Cirrus (SPARTICUS) field campaigns. The new parameterization assumes a normalized gamma PSD with two novel developments: no explicit assumption for particle habit in the calculation of mass distributions, and a formulation for translating ice particle fall speeds as a function of maximum diameter into fall speeds as a function of melted-equivalent diameter. Two parameters (particle volume-and projected area-weighted equivalent diameter) are diagnosed as a function of temperature and IWC in the convective plume, and these parameters constrain the shape and scale of the normalized gamma PSD. The diagnosed fall speeds and PSDs are combined with the GCM's parameterized convective updraft vertical velocity to partition convective updraft condensate into precipitating and detrained components. A 5-yr prescribed sea surface temperature GCM simulation shows a 30%-50% decrease in upper-tropospheric deep convective IWC, bringing the tropical and global mean ice water pa

关键词： Cloud microphysics Aircraft observations Climate models Cloud parameterizations convective parameterization Model evaluation/performance

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A Dynamically Computed convective Time Scale for the Kain-Fritsch convective parameterization Scheme

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MONTHLY WEATHER REVIEW 2015年第6期143卷 2105-2120页

作者： Bullock, O. Russell, Jr. Alapaty, Kiran Herwehe, Jerold A. Kain, John S. US EPA Natl Exposure Res Lab Res Triangle Pk NC 27711 USA NOAA Natl Severe Storms Lab Norman OK 73069 USA

Many convective parameterization schemes define a convective adjustment time scale tau as the time allowed for dissipation of convective available potential energy (CAPE). The Kain-Fritsch scheme defines tau based on an estimate of the advective time period for deep convective clouds within a grid cell, with limits of 1800 and 3600 s, based on practical cloud-lifetime considerations. In simulations from the Weather Research and Forecasting (WRF) Model using 12-km grid spacing, the value of tau often defaults to the lower limit, resulting in relatively rapid thermodynamics adjustments and high precipitation rates. Herein, a new computation for tau in the Kain-Fritsch scheme is implemented based on the depth of the buoyant layer and the convective velocity scale. This new tau formulation is applied using 12- and 36-km model grid spacing in conjunction with a previous modification that takes into account the radiation effects of parameterized convective clouds. The dynamically computed convective adjustment time scale is shown to reduce the precipitation bias by approximately 15% while also providing improved simulations of inland rainfall from tropical storms.

关键词： convective parameterization Mesoscale models Model evaluation/performance Numerical analysis/modeling Numerical weather prediction/forecasting Subgrid-scale processes

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Sea-Breeze Dynamics and Convection Initiation: The Influence of convective parameterization in Weather and Climate Model Biases

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JOURNAL OF CLIMATE 2015年第20期28卷 8093-8108页

作者： Birch, Cathryn E. Roberts, Malcolm J. Garcia-Carreras, Luis Ackerley, Duncan Reeder, Michael J. Lock, Adrian P. Schiemann, Reinhard Univ Leeds Met Off Leeds Leeds LS2 9JT W Yorkshire England Met Off Exeter Devon England Univ Leeds Sch Earth & Environm Leeds LS2 9JT W Yorkshire England Monash Univ Sch Earth Atmosphere & Environm Clayton Vic Australia Monash Univ Ctr Excellence Climate Syst Sci Clayton Vic Australia Univ Reading Dept Meteorol Natl Ctr Atmospher Sci Reading Berks England

There are some long-established biases in atmospheric models that originate from the representation of tropical convection. Previously, it has been difficult to separate cause and effect because errors are often the result of a number of interacting biases. Recently, researchers have gained the ability to run multiyear global climate model simulations with grid spacings small enough to switch the convective parameterization off, which permits the convection to develop explicitly. There are clear improvements to the initiation of convective storms and the diurnal cycle of rainfall in the convection-permitting simulations, which enables a new process-study approach to model bias identification. In this study, multiyear global atmosphere-only climate simulations with and without convective parameterization are undertaken with the Met Office Unified Model and are analyzed over the Maritime Continent region, where convergence from sea-breeze circulations is key for convection initiation. The analysis shows that, although the simulation with parameterized convection is able to reproduce the key rain-forming sea-breeze circulation, the parameterization is not able to respond realistically to the circulation. A feedback of errors also occurs: the convective parameterization causes rain to fall in the early morning, which cools and wets the boundary layer, reducing the land-sea temperature contrast and weakening the sea breeze. This is, however, an effect of the convective bias, rather than a cause of it. Improvements to how and when convection schemes trigger convection will improve both the timing and location of tropical rainfall and representation of sea-breeze circulations.

关键词： Geographic location entity Maritime Continent Atm Ocean Structure Phenomena Precipitation Sea breezes Models and modeling convective parameterization General circulation models Variability Diurnal effects

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Toward a Generalized Understanding of the Role of convective Available Potential Energy (CAPE) Removal and Entrainment Rate in convective parameterizations on the Diurnal Cycle of Tropical Precipitation

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WEATHER AND FORECASTING 2025年第1期40卷 37-53页

作者： Murata, Akihiko Fukui, Shin Nosaka, Masaya Ushiyama, Tomoki Acierto, Ralph allen Meteorol Res Inst Tsukuba Ibaraki Japan Publ Works Res Inst Int Ctr Water Hazard & Risk Management Tsukuba Japan

The diurnal rainfall cycle is a key factor affecting tropical precipitation variability. However, the diurnal cycle is not sufficiently represented in numerical models, which can be associated with convective parameterization in the models. This study presents the sensitivity of simulated precipitation over Java Island, Indonesia, to adjust two parameters in parameterization schemes. These two parameters are related to convective available potential energy (CAPE) removal and entrainment of environmental air into cumulus convection. Using a climate model, we conducted sensitivity experiments by perturbing the parameters in two plume-type convective parameterization schemes, Kain-Fritsch and Grell. Our results show a delayed phase of the diurnal cycle of the simulated precipitation over land, although this phase delay was not found over the oceanic areas. Sensitivity tests demonstrated that the phase delay of precipitation over land depends on the values of these two parameters. The timing of precipitation was improved by enhancing the degree of elimination of the vertical instability and reducing the entrainment rate. Further analyses by dividing simulated precipitation into parameterized and nonparameterized precipitation demonstrate that enhancing the degree of elimination of vertical instability can produce adequate amount of precipitation and that the reduced entrainment rate can increase the cloud top, improving precipitation timing. These results apply to both the convective parameterization schemes. Therefore, the results obtained in this study can be generalized to a range of convective parameterizations using the plume model.

关键词： Tropics Entrainment Precipitation convective parameterization Diurnal effects

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Effects of convective Microphysics parameterization on Large-Scale Cloud Hydrological Cycle and Radiative Budget in Tropical and Midlatitude convective Regions

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JOURNAL OF CLIMATE 2015年第23期28卷 9277-9297页

作者： Storer, Rachel L. Zhang, Guang J. Song, Xiaoliang Scripps Inst Oceanog La Jolla CA 92037 USA

A two-moment microphysics scheme for deep convection was previously implemented in the NCAR Community Atmosphere Model version 5 (CAM5) by Song et al. The new scheme improved hydrometeor profiles in deep convective clouds and increased deep convective detrainment, reducing the negative biases in low and midlevel cloud fraction and liquid water path compared to observations. Here, the authors examine in more detail the impacts of this improved microphysical representation on regional-scale water and radiation budgets. As a primary source of cloud water for stratiform clouds is detrainment from deep and shallow convection, the enhanced detrainment leads to larger stratiform cloud fractions, higher cloud water content, and more stratiform precipitation over the ocean, particularly in the subtropics where convective frequency is also increased. This leads to increased net cloud radiative forcing. Over land regions, cloud amounts are reduced as a result of lower relative humidity, leading to weaker cloud forcing and increased OLR. Comparing the water budgets to cloud-resolving model simulations shows improvement in the partitioning between convective and stratiform precipitation, though the deep convection is still too active in the GCM. The addition of convective microphysics leads to an overall improvement in the regional cloud water budgets.

关键词： Physical Meteorology and Climatology Cloud microphysics Models and modeling Climate models convective parameterization

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