scholarly journals Effects of the Convective Triggering Process in a Cumulus Parameterization Scheme on the Diurnal Variation of Precipitation over East Asia

Atmosphere ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 28 ◽  
Author(s):  
Ji-Young Han ◽  
So-Young Kim ◽  
In-Jin Choi ◽  
Emilia Jin
Keyword(s):  
Diurnal Variation ◽  
East Asia ◽  
Climate Model ◽  
Regional Climate ◽  
Cumulus Parameterization ◽  
Parameterization Scheme ◽  
Cumulus Parameterization Scheme ◽  
Precipitation Frequency ◽  
Convective Initiation ◽  
Triggering Process

Effects of the convective triggering process in a cumulus parameterization scheme on the diurnal variation of precipitation over East Asia are examined using a regional climate model. Based on a cloud-resolving simulation showing the irrelevance of convective inhibition once convection is initiated and the sensitivity experiments to trigger conditions, the triggering process in the simplified Arakawa-Schubert (SAS) convection scheme is modified to use different convective initiation and termination conditions. The diurnal variation of precipitation frequency with the modified triggering process becomes in phase with the observed one, leading to a delayed afternoon peak in precipitation rate that is in better agreement with the observation. However, the bias in the phase of precipitation intensity is not resolved and the bias of excessive precipitation increases, indicating that adequate representation of not only the triggering process but also other moist convective processes that determine the strength of convection is required for further improvement in the simulation of the diurnal variation of precipitation.

Parameter Tuning and Calibration of RegCM3 with MIT–Emanuel Cumulus Parameterization Scheme over CORDEX East Asia Domain

2014 ◽  
Vol 27 (20) ◽  
pp. 7687-7701 ◽  
Author(s):  
Liwei Zou ◽  
Yun Qian ◽  
Tianjun Zhou ◽  
Ben Yang
Keyword(s):  
East Asia ◽  
Regional Climate ◽  
Cumulus Parameterization ◽  
Parameterization Scheme ◽  
Cumulus Parameterization Scheme ◽  
Convection Scheme ◽  
Total Rainfall ◽  
Low Level ◽  
Positive Effects ◽  
Cordex East Asia

Abstract In this study, the authors calibrated the performance of the Regional Climate Model, version 3 (RegCM3), with the Massachusetts Institute of Technology (MIT)–Emanuel cumulus parameterization scheme over the Coordinated Regional Climate Downscaling Experiment (CORDEX) East Asia domain by tuning seven selected parameters based on the multiple very fast simulated annealing (MVFSA) approach. The seven parameters were selected based on previous studies using RegCM3 with the MIT–Emanuel convection scheme. The results show the simulated spatial pattern of rainfall, and the probability density function distribution of daily rainfall rates is significantly improved in the optimal simulation. Sensitivity analysis suggests that the parameter relative humidity criteria (RHC) has the largest effect on the model results. Followed by an increase of RHC, an increase of total rainfall is found over the northern equatorial western Pacific, mainly contributed by the increase of explicit rainfall. The increases of the convergence of low-level water vapor transport and the associated increases in cloud water favor the increase of explicit rainfall. The identified optimal parameters constrained by total rainfall have positive effects on the low-level circulation and surface air temperature. Furthermore, the optimized parameters based on the chosen extreme case are transferable to a normal case and the model’s new version with a mixed convection scheme.

scholarly journals Improved Physical Processes in a Regional Climate Model and Their Impact on the Simulated Summer Monsoon Circulations over East Asia

2008 ◽  
Vol 21 (5) ◽  
pp. 963-979 ◽  
Author(s):  
Yoo-Bin Yhang ◽  
Song-You Hong
Keyword(s):  
Boundary Layer ◽  
Summer Monsoon ◽  
Large Scale ◽  
Climate Model ◽  
Asian Summer Monsoon ◽  
Regional Climate ◽  
Analysis Data ◽  
Cumulus Parameterization ◽  
Intraseasonal Variation ◽  
Thermal Roughness Length

Abstract This paper documents the sensitivity of the modeled evolution of the East Asian summer monsoon (EASM) to physical parameterization using the National Centers for Environmental Prediction (NCEP) Regional Spectral Model (RSM). To this end, perfect boundary condition experiments driven by analysis data are designed for August 2003 to investigate the individual role of the surface processes, boundary layer, and convection parameterization on the simulated monsoon. Also, 10-yr June–August (JJA) simulations from 1996 to 2005 are performed to evaluate the overall impacts of these revisions on the simulated EASM climatology. The one-month simulation for August 2003 reveals that the experiment with a realistic distribution of land use conditions and vegetation and smaller thermal roughness length simulates higher temperature and geopotential height. On the other hand, in the experiment with an improved boundary layer scheme, the rainfall amount is slightly decreased due to reduced vertical mixing. The simulation with revised subgrid-scale processes in the cumulus parameterization scheme reproduces a rainband over the subtropics, which is weakly simulated by the default package. The overall large-scale distribution from the experiment, which includes all three revised physics processes, shows the same direction as that of the revised convection run in the middle and upper troposphere, but is improved further when other newly enhanced processes are combined. These improvements are also achieved in a 10-yr summer simulation. It is distinct that the revised physics package improves the large-scale patterns by strengthening the intensity of the North Pacific high and reducing the intensity of the lower-level jet, which are critical components in the EASM. The general patterns of the interannual and intraseasonal variation of precipitation are also improved, in particular, over land.

scholarly journals Simulation of dust aerosol and its regional feedbacks over East Asia using a regional climate model

2008 ◽  
Vol 8 (2) ◽  
pp. 4625-4667 ◽  
Author(s):  
D. F. Zhang ◽  
A. S. Zakey ◽  
X. J. Gao ◽  
F. Giorgi
Keyword(s):  
East Asia ◽  
Regional Climate Model ◽  
Radiative Forcing ◽  
Climate Model ◽  
Regional Climate ◽  
Surface Cooling ◽  
Near Surface ◽  
Dust Aerosols ◽  
Source Regions ◽  
Mass Load

Abstract. The ICTP regional climate model (RegCM3) coupled with a desert dust model is used to simulate the radiative forcing and related climate effects of dust aerosols over East Asia. Two sets of experiments encompassing the main dust producing months, February to May, for 10 years (1997–2006) are conducted and inter-compared, one without (Exp. 1) and one with (Exp. 2) the radiative effects of dust aerosols. The simulation results are evaluated against ground station and satellite data. The model captures the basic observed climatology over the area of interest. The spatial and temporal variations of near surface concentration, mass load, and emission of dust aerosols from the main source regions are reproduced by model, with the main model deficiency being an overestimate of dust amount over the source regions and underestimate downwind of these source areas. Both the top-of-the-atmosphere (TOA) and surface radiative fluxes are decreased by dust and this causes a surface cooling locally up to −1°C. The inclusion of dust radiative forcing leads to a reduction of dust emission in the East Asia source regions, which is mainly caused by an increase in local stability and a corresponding decrease in dust lifting. Our results indicate that dust effects should be included in the assessment of climate change over East Asia.

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