Cumulus Convection Parameterization Schemes Research Articles

Evaluation of WRF Performance in Simulating an Extreme Precipitation Event over the South of Minas Gerais, Brazil

Extreme precipitation events are becoming increasingly frequent and intense in southeastern Brazil, leading to socio-economic problems. While it is not possible to control these events, providing accurate weather forecasts can help society be better prepared. In this study, we assess the performance of the Weather Research and Forecasting (WRF) model in simulating a period of extreme precipitation from 31 December 2021 to 2 January 2022 in the southern region of Minas Gerais (SMG) state in southeastern Brazil. We conducted five simulations using two nested grids: a 12 km grid (coarse resolution) and a 3 km grid (high resolution). For the coarse resolution, we tested the performance of five cumulus convection parameterization schemes: Kain–Fritsch, Betts–Miller–Janjic, Grell–Freitas, Grell–Devenyi, and New Tiedke. We evaluated the impact of these simulations on driving the high-resolution simulations. To assess the performance of the simulations, we compared them with satellite estimates, in situ precipitation measurements from thirteen meteorological stations, and other variables from ERA5 reanalysis. Based on the results, we found that the Grell–Freitas scheme has better performance in simulating the spatial pattern and intensity of precipitation for the studied region when compared with the other four analyzed schemes.

WRF ensemble dynamical downscaling of precipitation over China using different cumulus convective schemes

Ensemble dynamical downscaling of precipitation over China was conducted based on simulations of the Weather and Research Forecasting model using both Kain–Fritsch and Grell cumulus convective parameterization schemes. The simulations were driven by ERA-Interim reanalysis data with 25-km horizontal resolution for the period 1980–2015. Results indicated that superior performance was achieved by the ensemble based on the two different schemes because certain observed signals were captured complementarily by each scheme over distinct regions. For climatological mean precipitation, the ensemble improved the annual mean pattern, probability distribution, and seasonal evolution of precipitation. With regard to interannual variation, the ensemble showed the highest skill in representing the series of precipitation anomalies at regional scales for all subregions. Improvement was also evident in the spatial patterns of the dominant precipitation variability modes and the corresponding temporal variations. For extreme precipitation, several indices were selected, and the ensemble was better able to capture the main features with higher spatial pattern correlations and closer magnitudes. The advantages of the ensemble are due to its appropriate regime specific weights derived from the Kain–Fritsch and Grell schemes

Precipitation Simulation from the Cumulus Convection Parameterization Schemes Based on the WRF Model in the Weihe River Basin, china

Two cumulus convection parameterization schemes, i.e., Kain-Fritsch (K-F) and Grell-3 based on the V4.1.2 Weather Research and Forecasting (WRF) model, were used to simulate the summer precipitation in the Weihe River Basin using hourly precipitation data at the resolution of 5 km and 2 km. the precipitation experiment results at different resolution were compared and analyzed. The root square error and correlation coefficient were used to verify and evaluate the simulation results. The results show that in K-F and Grell-3, the two cumulus model simulations with a resolution of 5 km can explain the spatial distribution pattern of precipitation and the diurnal variation process, and the experimental simulation results are consistent with the actual observations. The summer precipitation simulation in June, July, and August is highly sensitive to the two cumulus parameter schemes of K-F and Grell-3. The simulated precipitation value is higher than the actual value, and the root mean square errors (RMSEs) of K-F and Grell-3 schemes are 5.49-13.29 and 5.69-10.88, respectively. In terms of precipitation simulation, Grell-3 scheme is better than K-F scheme, especially in areas with heavy rainfall. When the resolution is increased to 2 km, the regions with heavy precipitation can be displayed more finely. The influence of water vapor flux and vertical velocity changes on precipitation in the Weihe River is analyzed from two aspects, i.e., water conditions and atmospheric instability. From the simulation results by the K-F scheme, the vertical velocity fluctuations are unstable and strong in the convective area, and the convective rainfall is relatively high. From the simulation results by Grell-3, the vertical velocity is large and increased rapidly, which is conducive to the generation of large-scale heavy precipitation. Both schemes are very sensitive to the simulation of water vapor transport and vertical velocity. This study provides a basis for the research on the adaptability of regional precipitation simulation.

Seasonal Climate Forecast For The Alcântara Launch Center - Brazil

This work analyzed the performance of three cumulus convection parameterization schemes (Kain-Fritsch, Emanuel and Grell/Emanuel) in forecasting the seasonal climate during the transition from rainy to dry period (June to July 2017) in Alcântara Launch Center (ALC) located in Maranhão State-Brazil. For this reason, the outputs from the global NCEP climate forecast system (CFSv2) were used as initial and boundary conditions in the Regional Climate Model (RegCM4.4). The results also focused on the vertical wind profile in the lower atmosphere in the ALC. The forecasts of this variable were validated with data from the wind profile registered by a micrometeorological tower in ALC. The forecasts had better skill in represent the intensity wind in June/July on average and the better convective scheme was Grell Convection Scheme (the Land)/Emanuel convection Scheme (the Ocean).

Impact of different cumulus convective parameterization schemes on the simulation of precipitation over China

The impact of two cumulus convective schemes on the simulation of the precipitation over China is investigated using the Weather Research and Forecasting (WRF) model. Simulations for the period of 1982–2004 are performed at a horizontal resolution of 30 km and forced by NCEP Reanalysis II data. Results show precipitation simulated with the WRF model is quite sensitive to the choice of Kain–Fritsch and Grell cumulus schemes. Both the schemes have distinct skills in predicting the seasonal mean pattern, annual cycle and interannual variation in precipitation. The results show that the Kain–Fritsch scheme tends to overestimate the magnitude of the summer and annual mean precipitation over the main rain-belts, while the Grell scheme tends to underestimate these effects, particularly the simulation of the summer extreme precipitation. However, the Kain–Fritsch scheme is more skilful in capturing the seasonal mean pattern and annual cycle with higher spatial correlations in the main rain-belts. The Grell scheme shows some advantages for northern China and the Tibetan Plateau, especially in representing the interannual variation. The optimal ensemble approach is used to determine the best combination of the two schemes, with the results giving a better overall performance than the individual schemes alone in predicting summer precipitation. The temporal correlation coefficient of precipitation for the ensemble is significantly higher, while the root mean square error of extreme precipitation is reduced compared with the Kain–Fritsch and Grell results. This shows that the ensemble approach based on the optimal ensemble weight combines the advantages of the two cumulus schemes efficiently.

Impacts of Cumulus Convective Parameterization Schemes on Precipitation at Grey-Zone Resolutions: A Case Study over Complex Terrain in upper Northern Thailand

Impacts of Cumulus Convective Parameterization Schemes on Precipitation at Grey-Zone Resolutions: A Case Study over Complex Terrain in upper Northern Thailand

Customization of regional climate model (RegCM4) over Indian region

The regional climate model (RegCM4) is customized for 10-year climate simulation over Indian region through sensitivity studies on cumulus convection and land surface parameterization schemes. The model is configured over 30° E–120° E and 15° S–45° N at 30-km horizontal resolution with 23 vertical levels. Six 10-year (1991–2000) simulations are conducted with the combinations of two land surface schemes (BATS, CLM3.5) and three cumulus convection schemes (Kuo, Grell, MIT). The simulated annual and seasonal climatology of surface temperature and precipitation are compared with CRU observations. The interannual variability of these two parameters is also analyzed. The results indicate that the model simulated climatology is sensitive to the convection as well as land surface parameterization. The analysis of surface temperature (precipitation) climatology indicates that the model with CLM produces warmer (dryer) climatology, particularly over India. The warmer (dryer) climatology is due to the higher sensible heat flux (lower evapotranspiration) in CLM. The model with MIT convection scheme simulated wetter and warmer climatology (higher precipitation and temperature) with smaller Bowen ratio over southern India compared to that with the Grell and Kuo schemes. This indicates that a land surface scheme produces warmer but drier climatology with sensible heating contributing to warming where as a convection scheme warmer but wetter climatology with latent heat contributing to warming. The climatology of surface temperature over India is better simulated by the model with BATS land surface model in combination with MIT convection scheme while the precipitation climatology is better simulated with BATS land surface model in combination with Grell convection scheme. Overall, the modeling system with the combination of Grell convection and BATS land surface scheme provides better climate simulation over the Indian region.

Impact of Different Convective Parameterization on Simulation of Precipitation for the Heihe River Basin

In order to examine sensitivity of cumulus convective parameterization scheme in climate simulating over the Heihe River Basin( HRB),three cumulus parameterization schemes in Regional Integrated Environmental Model System for HRB( RIEMS-Heihe) with 3km resoultion,Grell,Bett-Miller( BM) and NON were compared and analyzed in precipitation simulation over HRB. The analysis results showed the following: ①BNU daily precipitation in the whole of the HRB was underestimated than the observed precipitation. ②Either cumulus convective parameterization schemes,model could simulate the spatial distribution and temporal evolution of daily precipitation in different regions of HRB,and the correlation coefficient between the simulated and observed daily precipitation reached a significance level of 1%. ③For the HRB,RIEMS-Heihewith the Grellcumulus convective parameterizationscheme than the other two schemes in term of evolution of daily precipitationis was closer to that of the observation,and the correlation coefficient between the simulated and observed daily precipitation reached a significance level of 1%.

应用RegCM4模拟汉江流域降水和气温

本文使用动力降尺度方法模拟汉江流域气象因素，将大尺度气象观测值转化到流域上，得到流域站点降水和气候模拟值。使用RegCM4区域气候模式，嵌套ERA40再分析资料，分别采用Grell方案、Kuo方案、Emanuel方案和Tiedtke方案等积云对流方案，对汉江流域进行了10年(1991~2000年)模拟试验，重点分析了RegCM4对汉江流域地表气温和降水的模拟结果。结果表明，模式对汉江流域地表气温温度值和变化趋势具有较好的模拟能力。月平均温度模拟值与实测值误差小于2℃，但存在系统性的“冷偏差”。该模式对降水的模拟精度比温度模拟要差。对年降雨量的模拟，不同积云对流方案模拟结果相差较大；在几种对流方案比较中，Emanuel方案对月平均降水量相对模拟效果最好；然而RegCM4对不同站点的插值模拟效果差异比较大，表明模式对降水的空间分布还有待改进。 This work simulated climate factors in Hanjiang Basin by using dynamical downscaling method, transforming large scale observed climate variables into station precipitation and temperature. A 10-year (1991-2000) numerical integration simulation of climate over Hanjiang Basin was conducted with the latest version of a regional climate model RegCM4 nested in one-way ERA40 Re-analysis data. The Grell, AnthesKuo, MIT-Emanuel and Tiedtke cumulus convection parameterization schemes were applied in the running of RegCM4 to test their capability in simulating precipitation and temperature of Hanjiang Basin. The results demonstrated that RegCM4 was capable of well simulating the values and the changing trend of ground temperature during a year. In most cases, the error between simulated mean monthly temperature and observation was within 2°C, but there existed systematic “cold bias”. However, the simulation accuracy of precipitation is not as optimal as that of temperature. Different cumulus convection parameterization schemes displayed different capability in simulating annual precipitation. Among all 4 cumulus convection parameterization schemes, the MIT-Emanuel scheme had been proven to be the most accurate in simulating monthly precipitation. The accuracy of the scheme also showed great difference in simulated station interpolation of precipitation, which urges the improvement for the simulation capability of spatial distribution of precipitation.

天气预报模式WRFV3.3在三峡库区的应用及参数敏感性试验研究

为实现长江三峡库区的高精度降水预报，利用新一代天气预报模式WRFV3.3对三峡库区两场典型降水过程进行模拟试验，并采用TS评分与极差分析法分析其不同参数化方案组合对降水模拟的影响，以评估WRF模式在三峡库区的区域适用性以及物理过程参数敏感性。结果表明，WRFV3.3能够较好地模拟三峡库区典型降水过程，且当WRF模式中微物理过程为Lin et al.方案、积云对流参数化方案为Simplified Arakawa-Schubert方案时，比其他参数化方案组合能得到更好的模拟效果；通过极差分析法比较发现，对于小雨和暴雨量级的降水，微物理过程方案和积云对流参数化方案的影响度接近，但对于中雨和大雨量级的降水，微物理过程方案的影响占主导地位。 In order to achieve high accuracy for precipitation forecast in the Three Gorges Reservoir area, a new generation of numerical weather model WRFV3.3 was applied to simulate two typical precipitation events in the Three Gorges Reservoir area, for evaluating WRF’s applicability in the research area. The im-pacts of different parameterization schemes combination on precipitation simulation were studied by adopt-ing TS and variance analysis, for analyzing sensitivity of the physical process parameterization schemes. The results indicate that WRFV3.3 can simulate typical precipitation events well in the Three Gorges Reservoir area. When the micro-physical process scheme is Lin et al. and the cumulus convective parameterization scheme is Simplified Arakawa-Schubert, the simulation of WRF is better than other parameterization scheme combinations. Comparison of variance analysis shows that the impact of the micro-physical process parame-terization schemes on precipitation is similar as the cumulus convective parameterization schemes when rain grade is 0.1 mm and 50 mm, while impact of the micro-physical process parameterization schemes is domi-nating when rain grade is 10 mm and 25 mm.

Impacts of cumulus convective parameterization schemes on summer monsoon precipitation simulation over China

By using the Betts-Miller-Janjic, Grell-Devenyi, and Kain-Fritsch cumulus convective parameterization schemes in theWeather Research and Forecasting (WRF) model, long time simulations from 2000 to 2009 are conducted to investigate the impacts of different cumulus convective parameterization schemes on summer monsoon precipitation simulation over China. The results show that all the schemes have the capability to reasonably reproduce the spatial and temporal distributions of summer monsoon precipitation and the corresponding background circulation. The observed north-south shift of monsoon rain belt is also well simulated by the three schemes. Detailed comparison indicates that the Grell-Devenyi scheme gives a better performance than the others. Deficiency in simulated water vapor transport is one possible reason for the precipitation simulation bias.

Effects of convective parameterization schemes on estimation of the annual wet deposition over Northeast Asia

Abstract This paper presents technique used to estimate annual total wet depositions of NO3− and SO42−, and describes their sensitivities arising from various convective parameterization schemes over Northeast Asia. The representative synoptic meteorological conditions for the precipitation were identified by employing a cluster analysis technique, and four cumulus convective parameterization schemes, the Anthes–Kuo (AK), Betts–Miller (BM), Grell (GR), and Kain–Fritsch 2 (KF2) schemes, were applied to estimate annual wet deposition simulations. The four convective parameterization schemes were found to reproduce the overall observed precipitation band for each of the classified synoptic patterns. When cluster analysis was used with these four schemes, the estimated annual total wet depositions of SO42− and NO3− over South Korea were found to reach 184–197 and 277–337 kton year−1, respectively, with the highest estimation found with the KF2 scheme. These estimates were higher than the results of the continuous full year-long simulations by three dimensional comprehensive acid deposition model, which found values of 130 kton year−1 for SO42− and 270 kton year−1 for NO3−. There was a 15.2% variability in the annual total precipitation from the use of the different convective parameterizations of the four schemes, but the annual total wet depositions of the four cloud parameterization schemes were in good agreement, with estimated variabilities of approximately 9.1 and 8.8% for SO42− and NO3−, respectively. At less than ∼10%, these variations were small and negligible in an estimation of the long-term depositions over the region of Korean Peninsula.

An analysis of Typhoon Chanthu in June 2004 with focus on the impact on Thailand

In this paper, the influence of Typhoon Chanthu on Thailand during June 2004 was studied. Several major features have been revealed. (1) Chanthu formed and developed in favorable large-scale conditions. A continental high-pressure system covered most of China and merged with the West Pacific Subtropical High to become a west-east oriented high-pressure band, which was responsible for the westward movement of the typhoon. (2) There existed a stationary and active ITCZ, which was the preferred formation area of the typhoon. The ITCZ extended from the Bay of Bengal, through the Indo-China Peninsula and the South China Sea, to the western Pacific. Chanthu formed in the ITCZ and moved almost directly along it. (3) The moisture sources differed during the various stages of development. In the earlier stages, water vapor came largely from the South China Sea but in later stages, the source was mainly from the Bay of Bengal. The rich water vapor supply explains the long-lived effects of Chanthu and its remnants after landfall. (4) Cyclonic circulation remained following the landfall of Chanthu, as did a weak warm core in the upper-middle troposphere, which was likely caused by the release of latent heat from convective condensation. Due to the ample moisture supply from the ITCZ, convective activity was still very active after landfall. (5) Subgrid-scale convective systems played an important role in the kinetic energy budget. In addition, numerical simulations show that, among various cumulus convective parameterization schemes, the Betts-Miller-Janjic scheme seemed to be the best in the summer season.

Sensitivity of ITCZ configuration to cumulus convective parameterizations on an aqua planet

This paper examines the performances of various cumulus convective parameterization schemes in the tropical atmosphere using an aqua-planet atmospheric General Circulation Model forced by zonally symmetric but latitudinally varying sea surface temperature (SST) and solar angle. The intertropical convergence zone (ITCZ) is represented by intense precipitation. The assigned Control experiment with a specific SST distribution, as designated by the Aqua Planet Experiment, yields a single ITCZ when Zhang’s scheme or Manabe’s scheme is employed, whereas a double ITCZ occurs when Tiedtke’s scheme is used. The key to the occurrence of a double ITCZ is latitudinal variation in evaporation within the boundary layer. Such variation is induced mainly by latitudinal variation in the zonal wind speed, with the existence of a calm belt at the equator and a maximum wind speed located off the equator, arising from the evaporation–wind feedback (EWF) mechanism. The latitudinal distribution of evaporation results in a decrease in the height of the lifting condensation level in areas off the equator and an increase at the equator. The occurrence of a single ITCZ in Zhang’s scheme is attributed to the use of a Convective Available Potential Energy criterion by which convection occurs more readily at the equator. As a result, a precipitation maximum is maintained at the equator via a prevailing Conditional Instability of the Second Kind mechanism.

Evaluation of the atmospheric transport in a GCM using radon measurements: sensitivity to cumulus convection parameterization

Abstract. The radioactive species radon (222Rn) has long been used as a test tracer for the numerical simulation of large scale transport processes. In this study, radon transport experiments are carried out using an atmospheric GCM with a finite-difference dynamical core, the van Leer type FFSL advection algorithm, and two state-of-the-art cumulus convection parameterization schemes. Measurements of surface concentration and vertical distribution of radon collected from the literature are used as references in model evaluation. The simulated radon concentrations using both convection schemes turn out to be consistent with earlier studies with many other models. Comparison with measurements indicates that at the locations where significant seasonal variations are observed in reality, the model can reproduce both the monthly mean surface radon concentration and the annual cycle quite well. At those sites where the seasonal variation is not large, the model is able to give a correct magnitude of the annual mean. In East Asia, where radon simulations are rarely reported in the literature, detailed analysis shows that our results compare reasonably well with the observations. The most evident changes caused by the use of a different convection scheme are found in the vertical distribution of the tracer. The scheme associated with weaker upward transport gives higher radon concentration up to about 6 km above the surface, and lower values in higher altitudes. In the lower part of the atmosphere results from this scheme does not agree as well with the measurements as the other scheme. Differences from 6 km to the model top are even larger, although we are not yet able to tell which simulation is better due to the lack of observations at such high altitudes.

A Study on the Impact of Parameterization of Physical Processes on Prediction of Tropical Cyclones over the Bay of Bengal With NCAR/PSU Mesoscale Model

Prediction of the track and intensity of tropical cyclones is one of the most challenging problems in numerical weather prediction (NWP). The chief objective of this study is to investigate the performance of different cumulus convection and planetary boundary layer (PBL) parameterization schemes in the simulation of tropical cyclones over the Bay of Bengal. For this purpose, two severe cyclonic storms are simulated with two PBL and four convection schemes using non-hydrostatic version of MM5 modeling system. Several important model simulated fields including sea level pressure, horizontal wind and precipitation are compared with the corresponding verification analysis/observation. The track of the cyclones in the simulation and analysis are compared with the best-fit track provided by India Meteorological Department (IMD). The Hong-Pan PBL scheme (as implemented in NCAR Medium Range Forecast (MRF) model) in combination with Grell (or Betts-Miller) cumulus convection scheme is found to perform better than the other combinations of schemes used in this study. Though it is expected that radiative processes may not have pronounced effect in short-range forecasts, an attempt is made to calibrate the model with respect to the two radiation parameterization schemes used in the study. And the results indicate that radiation parameterization has noticeable impact on the simulation of tropical cyclones.

Radiative‐convective model with an explicit hydrologic cycle: 2. Sensitivity to large changes in solar forcing

The one‐dimensional radiative‐connective equilibrium model with an explicit hydrologic cycle introduced in part 1 is used to study the sensitivity of the model's atmosphere to large changes in the solar forcing, when various cumulus convection parameterizations are used. As shown by Simpson [1927], by Komabayasi [1967], and by Ingersoll [1969] when the concentration of the absorbing gas in the atmosphere is temperature dependent, equilibrium is impossible for values of the solar forcing larger than a critical value. This result is referred to as a runaway greenhouse. The cumulus convection parameterization schemes currently in use in global climate models (GCMs) employ different assumptions about moistening. This causes the critical solar forcing above which a runaway greenhouse occurs to be very sensitive to the cumulus convection scheme employed. Furthermore, using the microphysically based cumulus convection scheme proposed by Emanuel [1991], we show that the sensitivity of the equilibrium temperature to changes in the solar forcing depends crucially on the microphysics of cumulus convection. For fixed cloud conditions, the critical solar forcing for a runaway greenhouse to occur is between approximately 1.22 and 1.49 times the global mean value for the Earth, and for clear sky conditions, it is a few percent lower. The runaway greenhouse in the experiments with the mass flux schemes generally occurs more rapidly than in the experiments with the adjustment schemes. In addition, the inability of the hard convective adjustment scheme to produce an efficient vertical transport of moisture, together with the saturation requirement for convection to occur, leads to the breakdown of the radiative‐convective equilibria when other processes are not available to provide the necessary vertical transport of water vapor.