Kuo Scheme Research Articles

Impacts of Cumulus Parameterization Schemes on the Simulation of Interannual and Interdecadal Variation of Meiyu in the Middle and Lower Reaches of the Yangtze River by Using Regional Climate Model 4

This study has revealed the impacts of cumulus parameterization scheme (CPS) on the simulation of interannual and interdecadal variations of Meiyu in the middle and lower reaches of Yangtze River valley (YangtzeMeiyu) by using a regional climate model. A multiple 55-yr (1955-2009) simulation of YangtzeMeiyu is conducted using RegCM4.6 with different CPSs, including Emanuel scheme, Kuo scheme and Grell scheme. It is found that all the CPSs have good performances and strong convergence in simulating the interannual variation of YangtzeMeiyu rainfall amounts. However, large bias are found in the simulated interdecadal variation of YangtzeMeiyu rainfall amount by the three CPSs. Because the Emanuel CPS has good performance in the simulation of both interannual and interdecadal variations of YangtzeMeiyu, its overall performance in the simulation of total amount of YangtzeMeiyu is the best among the three CPSs. The second best CPS is the Grell scheme, and the worst is the Kuo scheme. The model convergence in simulating the distribution of YangtzeMeiyu shows an obvious characteristic of interdecadal variation. During the years with strong summer monsoon and northward rain belt, the simulated distributions of YangtzeMeiyu by the three CPSs are quite different, and the model convergence is weak. On the contrary, during the years with weak summer monsoon and southward rain belt, the simulated distributions of YangtzeMeiyu by the three CPSs are similar with each other, and the model convergence is strong. As a result, when the well-known interdecadal change happens in the late 1970s, the monsoon changes from strong to weak, whereas the model convergence changes from weak to strong.

Sensitivity studies and comprehensive evaluation of RegCM4.6.1 high-resolution climate simulations over the Tibetan Plateau

This study provides the first comprehensive assessment of Regional Climate Model version 4.6.1 (RegCM4) for the Tibetan Plateau (TP) region. A wide range of model configurations were analyzed with different parameterizations employed to represent cumulus convection (Kuo, Grell, Emanuel, Kain, and Tiedtke), land surface processes (BATS and CLM), planetary boundary layer turbulence (Holtslag and UW PBL), and radiation (CCM3 and RRTM). In addition to the above experiments at a 30-km horizontal resolution, another experiment was conducted based upon the use of a double-nested dynamic downscaling method to construct a simulation at a 10-km resolution to study the sensitivity to the model resolution. We evaluated a 20-year simulation for precipitation, cloud cover, surface radiation budget, 2-m air temperature, and the surface atmospheric circulation against ground and satellite-based observations during the period 1989–2008. Among the factors analyzed regarding sensitivity, precipitation was unsurprisingly found to be sensitive to the cumulus parameterization scheme, and the CLM is found to reduce rainfall compared with BATS, which is satisfactory for both the Emanuel and Tiedtke schemes. Compared with the cumulus convection schemes, the cloud cover and surface radiation budget are sensitive to the land surface, PBL, and radiation schemes. Generally, the CLM is characterized by reduced mean cloud cover and enhanced surface longwave and shortwave radiation compared with BATS. Conversely, the UW PBL and RRTM radiation schemes result in increased cloud cover and less surface radiation compared with the default options in RegCM4. All experiments, except those employing the Kuo scheme, represent the mean 2-m air temperature and regional circulation patterns reasonably well. At the basin scale, the seasonal cycle and interannual variations of precipitation are found to be not well depicted by most model configurations, although the temperature field was well reproduced. Considering all the analyzed variables collectively, the Tiedtke scheme combined with the CLM land surface model is demonstrated to provide the best performance over the TP. However, the higher-resolution version of the model improves the precipitation simulation significantly, particularly in the Brahmaputra river basin, which is located in the north of the Himalayas.

Influence of cumulus convection schemes on winter North Pacific storm tracks in the regional climate model RegCM4.5

AbstractBased on the regional climate model RegCM4.5 driven by National Centers for Environmental Prediction (NCEP) reanalysis, the influence of cumulus convection schemes (CCSs) on the winter North Pacific storm track (WNPST) is investigated. It is found that the climatology, interannual variation, spatial modes and characteristic indices of the WNPST are extremely sensitive to the choice of CCS. Among the selected CCSs, WNPST climatology and interannual variation in the Kuo scheme are better than in other CCSs, with a smaller root mean square error. The WNPST spatial modes and strength indices in the Kuo and Grell schemes are more consistent with NCEP reanalysis. The Kuo scheme has a stronger ability to simulate the WNPST latitude index and the interannual variation of winter characteristic indices. In addition, we attempt to reveal the possible reasons for the different performances of CCSs from the viewpoint of baroclinic energy conversion (BCEC). It is found that the energy conversion from the mean available potential energy to the eddy available potential energy (BCEC1) has no significant difference among the Kuo, Grell and Emanuel schemes, while energy conversion from the eddy available potential energy to eddy kinetic energy (BCEC2) in the Kuo scheme is obviously better than other CCSs, which means that the differences in BCEC2 among these CCSs may be one of the key reasons affecting the simulation results of the WNPST.

Performance evaluation of land surface models and cumulus convection schemes in the simulation of Indian summer monsoon using a regional climate model

In this study, an attempt has been made to investigate the sensitivity of land surface models (LSM) and cumulus convection schemes (CCS) using a regional climate model, RegCM Version-4.1 in simulating the Indian Summer Monsoon (ISM). Numerical experiments were conducted in seasonal scale (May–September) for three consecutive years: 2007, 2008, 2009 with two LSMs (Biosphere Atmosphere Transfer Scheme (BATS), Community Land Model (CLM 3.5) and five CCSs (MIT, KUO, GRELL, GRELL over land and MIT over ocean (GL_MO), GRELL over ocean and MIT over land (GO_ML)). Important synoptic features are validated using various reanalysis datasets and satellite derived products from TRMM and CRU data. Seasonally averaged surface temperature is reasonably well simulated by the model using both the LSMs along with CCSs namely, MIT, GO_ML and GL_MO schemes. Model simulations reveal slight warm bias using these schemes whereas significant cold bias is seen with KUO and GRELL schemes during all three years. It is noticed that the simulated Somali Jet (SJ) is weak in all simulations except MIT scheme in the simulations with (both BATS and CLM) in which the strength of SJ reasonably well captured. Although the model is able to simulate the Tropical Easterly Jet (TEJ) and Sub-Tropical Westerly Jet (STWJ) with all the CCSs in terms of their location and strength, the performance of MIT scheme seems to be better than the rest of the CCSs. Seasonal rainfall is not well simulated by the model. Significant underestimation of Indian Summer Monsoon Rainfall (ISMR) is observed over Central and North West India. Spatial distribution of seasonal ISMR is comparatively better simulated by the model with MIT followed by GO_ML scheme in combination with CLM although it overestimates rainfall over heavy precipitation zones. On overall statistical analysis, it is noticed that RegCM4 shows better skill in simulating ISM with MIT scheme using CLM.

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.

Sensitivity of the GCM driven summer monsoon simulations to cumulus parameterization schemes in nested RegCM3

The regional climate model (RegCM3) from the Abdus Salam International Centre for Theoretical Physics has been used to simulate the Indian summer monsoon for three different monsoon seasons such as deficit (1987), excess (1988) and normal (1989). Sensitivity to various cumulus parameterization and closure schemes of RegCM3 driven by the National Centre for Medium Range Weather Forecasting global spectral model products has been tested. The model integration of the nested RegCM3 is conducted using 90 and 30-km horizontal resolutions for outer and inner domains, respectively. The India Meteorological Department gridded rainfall (1° × 1°) and National Centre for Environment Prediction (NCEP)–Department of Energy (DOE) reanalysis-2 of 2.5° × 2.5° horizontal resolution data has been used for verification. The RegCM3 forced by NCEP–DOE reanalysis-2 data simulates monsoon seasons of 1987 and 1988 reasonably well, but the monsoon season of 1989 is not represented well in the model simulations. The RegCM3 runs driven by the global model are able to bring out seasonal mean rainfall and circulations well with the use of the Grell and Anthes–Kuo cumulus scheme at 90-km resolution. While the rainfall intensity and distribution is brought out well with the Anthes–Kuo scheme, upper air circulation features are brought out better by the Grell scheme. The simulated rainfall distribution is better with RegCM3 using the MIT-Emanuel cumulus scheme for 30-km resolution. Several statistical analyses, such as correlation coefficient, root mean square error, equitable threat score, confirm that the performance of MIT-Emanuel scheme at 30-km resolution is better in simulating all-India summer monsoon rainfall. The RegCM3 simulated rainfall amount is more and closer to observations than that from the global model. The RegCM3 has corrected its driven GCM in terms of rainfall distribution and magnitude over some parts of India during extreme years. This study brings out several weaknesses of the RegCM model which are documented in this paper.

Regional climate simulations of summer diurnal rainfall variations over East Asia and Southeast China

This study evaluates the performance of RegCM3 (Regional Climate Model Version 3) in simulating the East Asian rainfall, with emphasis on the diurnal variations of rainfall over Southeast China during the 1998–2002 summer (June–August) seasons. The evaluation focuses on the sensitivity of the choice of cumulus parameterizations and model domain. With the right setup, the spatial and temporal evolution of diurnal rainfall over Southeast China, which has not been well simulated by past studies, can be accurately simulated by RegCM3. Results show that the Emanuel cumulus scheme has a more realistic simulation of summer mean rainfall in East Asia, while the GFC (Grell scheme with the Frisch-Chappell convective closure assumption) scheme is better in simulating the diurnal variations of rainfall over Southeast China. The better performance of these two schemes [relative to the other two schemes in RegCM3: the Kuo scheme and the GAS (Grell scheme with the Arakawa–Schubert closure assumption) scheme] can be attributed to the reasonable reproduction of the major formation mechanism of rainfall—the moisture flux convergence—over Southeast China. Furthermore, when the simulation domain covers the entire Tibetan Plateau, the diurnal variations of rainfall over Southeast China are found to exhibit a noticeable improvement without changes in the physics schemes.

Analysis of the impact of rainfall assimilation during LBA atmospheric mesoscale missions in Southwest Amazon

The assimilation of satellite estimated precipitation data can be used as an efficient tool to improve the analysis of rainfall generated by numerical models of weather forecast. The system of data assimilation used in this study is cumulus parameterization inversion based on the Kuo scheme. Reanalysis were performed using the field experiment data of the LBA Project (WETAMC and DRYtoWET-AMC), where it was possible to verify an improvement in the simulations results, since the data assimilation corrects the position and the intensity of rainfall in the numerical model.

Seasonal evaluation of rainfall estimation by four cumulus parameterization schemes and their sensitivity analysis

Sustainable water resources management require scientifically sound information on precipitation, as it plays a key role in hydrological responses in a catchment. In recent years, mesoscale weather models in conjunction with hydrological models have gained great attention as they can provide high-resolution downscaled weather variables. Many cumulus parameterization schemes (CPSs) have been developed and incorporated into three-dimensional Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model 5 (MM5). This study has performed a comprehensive evaluation of four CPSs (the Anthes–Kuo, Grell, Betts–Miller and Kain–Fritsch93 schemes) to identify how their inclusion influences the mesoscale model's precipitation estimation capabilities. The study has also compared these four CPSs in terms of variability in rainfall estimation at various horizontal and vertical levels. For this purpose, the MM5 was nested down to resolution of 81 km for Domain 1 (domain span 21 × 81 km) and 3 km for Domain 4 (domain span 16 × 3 km), respectively, with vertical resolutions at 23, 40 and 53 vertical levels. The study was carried out at the Brue catchment in Southwest England using both the ERA-40 reanalysis data and the land-based observation data. The performances of four CPs were evaluated in terms of their ability to simulate the amount of cumulative rainfall in 4 months in 1995 representing the four seasonal months, namely, January (winter), March (spring), July (summer) and October (autumn). It is observed that the Anthes–Kuo scheme has produced inferior precipitation values during spring and autumn seasons while simulations during winter and summer were consistently good. The Betts–Miller scheme has produced some reasonable results, particularly at the small-scale domain (3 km grid size) during winter and summer. The KF2 scheme was the best scheme for the larger-scale (81 km grid size) domain during winter season at both 23 and 53 vertical levels. This scheme tended to underestimate rainfall for other seasons including the small-scale domain (3 km grid size) in the mesoscale. The Grell scheme was the best scheme in simulating rainfall rates, and was found to be superior to other three schemes with consistently better results in all four seasons and in different domain scales. Copyright © 2011 John Wiley & Sons, Ltd.

Simulation of south Asian physical environment using various cumulus parameterization schemes of MM5

AbstractThe objective of this study was to compare the effect of a selected convective parameterized scheme in a mesoscale model on the predicted precipitation using the fifth‐generation Mesoscale Model (MM5). Four cumulus parameterization schemes in MM5, the Grell scheme, the Kain–Fritsch scheme, the Anthes–Kuo scheme and the Betts–Miller scheme were tested to predict the monthly accumulated precipitation in a south Asian region of complex topography during the summer monsoon season (July and August) for the years 1998 and 2001. The simulated results of precipitation were compared with the satellite‐derived data of the Tropical Rainfall Measuring Mission (TRMM). Comparison of simulated precipitation patterns revealed that the Grell scheme realistically captured the rainfall patterns over the southern plain areas of the region which receive lesser precipitation throughout the year. This scheme was also in good agreement with the TRMM data for lesser amounts of precipitation over northern mountainous areas, though it showed underestimated results for heavy precipitation over the region. The rainfall patterns over the northern mountainous areas were captured well by the Kain–Fritsch scheme for heavy precipitation while this scheme slightly over predicted the precipitation trends in the southern plain areas. The Anthes–Kuo and the Betts–Miller schemes were not able to simulate the rainfall for this complex terrain satisfactorily. The set of physical options used in MM5 for precipitation in this study was also tested for some other meteorological parameters such as ambient temperature, potential temperature, relative humidity and the moist static energy and the results were validated against the Reanalysis data of US National Centre for Environmental Prediction (NCEP). It was found that the scheme that successfully simulated precipitation also predicted these other parameters well. Copyright © 2011 Royal Meteorological Society

The Impact of Three Different Cumulus Parameterization Schemes on the Indian Summer Monsoon Circulation

In the present paper, the regional model (MM5) has been used to evaluate the performance of three cumulus parameterization schemes (CPSs, namely, the Anthes-Kuo, Bette-Miller and Grell) over the Indian summer monsoon season of 1998. The model was integrated at 90 km horizontal resolution for the peak monsoon period of July, 1998. The initial and boundary conditions were taken from the National Center for Environmental Prediction (NCEP) reanalysis available at 2.5° horizontal resolution. The performance of these CPSs has been examined using precipitation, wind, surface air temperature and heat – moisture data. Features of the Indian summer monsoon are found to be fairly well simulated by these three schemes; however, some differences are found in the typical features of the Indian summer monsoon. The strength of low level westerly jet, the cross equatorial flow, and the tropical easterly Jet have emerged clearly in the simulation using Grell compared to other CPSs. The Grell cumulus convection scheme shows ascending motion over whole tropical monsoon region and descending motion in mid latitude and is found to show close resemblance with the reanalysis data. The model simulation with Kuo cumulus scheme shows descending motion over tropical region, which is found to be unrealistic during monsoon and provide under estimation of rainfall over the Indian region. Strong upward motion over oceanic region by the model using Betts-Miller and Kuo schemes is also found to be unrealistic. The simulation of heat and moisture budget, and distribution of rainfall during monsoon period over Indian subcontinent are found to be improved considerably using Grell scheme as compared to other CPSs, whereas using Kuo scheme, rainfall is found to be underestimated over Indian subcontinent.

Role of cumulus parameterization schemes in simulating heavy rainfall episodes off the coast of Maharashtra state during 28 June–4 July 2007

Indian summer monsoon gives on an average 250 cm of rainfall due to mesoscale/synoptic scale systems over west coast of India; now-a-days, MM5 model plays a very crucial role in simulating such heavy rainfall episodes like Mumbai (India) on 26 July 2005, which caused devastation through flash floods. The main aim of this study is to simulate such heavy rainfall episodes using three different cumulus parameterization schemes (CPS) namely Kain–Fritsch-1, Anthes–Kuo and Grell and to compare their relative merits in identifying the characteristics of mesoscale systems over 14 stations in coastal Maharashtra state during 28 June–4 July 2007. MM5 control experiment results are analysed for the fields of mean sea level pressure, wind, geopotential height at 850 hPa and rainfall with the above schemes. It is interesting to note that Kain–Fritsch-1 scheme simulates heavy rainfall amount of 48 cm for an observed rainfall of 51 cm in 24 h. The Grell scheme underestimates heavy rainfall episodes, while the Anthes–Kuo scheme is found to over predict rainfall on both temporal and spatial scales. The reason for better performance of KF-1 scheme may be due to inclusion of updrafts and downdrafts. Later the simulated rainfall quantities at 14 stations over study region are validated with both 3B42RT and observed rain gauge data of India Meteorological Department (IMD) and the results are promising. Finally, for the heavy rainfall prediction cases, the best threat score is at 0.25 mm threshold for three CPSs. Thus, this study is a breakthrough in pointing out that the KF-1 experiment has the best skill in predicting heavy rainfall episodes.

Effects of multicumulus convective ensemble on East Asian summer monsoon rainfall simulation

Simulating the Asian summer monsoon is one of the most challenging tasks in climate modeling. In particular, monsoon simulations strongly depend on the cumulus parameterization scheme being used, as attested by many modeling studies. In this paper, the performances of a “unified multicumulus convective ensemble scheme” (or unified scheme), Kuo, simplified Arakawa‐Schubert, Zhang and McFarlane convective parameterization schemes and moist convective adjustment in simulating the East Asian summer monsoon in a coupled General Circulation Model (GCM) are assessed. In the unified scheme, the latter four individual parameterizations are run in parallel without any modification. Simple average of outputs from each parameterization is then incorporated to the atmospheric model at every time step. Simulations based on these convection schemes during the boreal summer season are compared with observations, focusing on the formation and seasonal evolution of the Meiyu‐Changma‐Baiu rainband. It is found that the East Asian summer monsoon evolution in the GCM is sensitive to the convective parameterization being used. While the Kuo scheme is able to capture a reasonably strong subtropical front, its mean onset time is about two to three pentads earlier than the observed. Simulations based on the simplified Arakawa‐Schubert scheme give a more realistic onset date. However, the model subtropical rainband tends to be confined over land near the coastal region of East Asia. The unified scheme is able to reproduce a prominent East Asian subtropical rainband. Moreover, the seasonal evolution of the rainband is also well captured in the unified scheme simulations. Further diagnostics are carried out to elucidate the role of various circulation elements in the Meiyu‐Changma‐Baiu front formation. In the western part of the front over land regions, there is robust precursor signal in incoming shortwave radiation before monsoon onset in observations as well as model simulations. Comparison between performances of different convective parameterizations suggests that sensitivity to low‐level vorticity can be crucial for the northward migration of the subtropical front and its extension into the open ocean east of southern Japan.

Improved Forecasts of the Diurnal Cycle in the Tropics Using Multiple Global Models. Part I: Precipitation

Abstract The Tropical Rainfall Measuring Mission (TRMM) satellite supplemented with the Defense Meteorological Satellites Program (DMSP) microwave dataset provides accurate rain-rate estimates. Furthermore, infrared radiances from the geostationary satellites provide the possibility for mapping the diurnal change of tropical rainfall. Modeling of the phase and amplitude of the tropical rainfall is the theme of this paper. The present study utilizes a suite of global multimodels that are identical in all respects except for their cumulus parameterization algorithms. Six different cumulus parameterizations are tested in this study. These include the Florida State University (FSU) Modified Kuo Scheme (KUO), Goddard Space Flight Center (GSFC) Relaxed Arakawa–Schubert Scheme (RAS1), Naval Research Laboratory–Navy Operational Global Atmospheric Prediction System (NRL–NOGAPS) Relaxed Arakawa–Schubert Scheme (RAS2), NCEP Simplified Arakawa–Schubert Scheme (SAS), NCAR Zhang–McFarlane Scheme (ZM), and NRL–NOGAPS Emanuel Scheme (ECS). The authors carried out nearly 600 experiments with these six versions of the T170 Florida State University global spectral model. These are 5-day NWP experiments where the diurnal change datasets were archived at 3-hourly intervals. This study includes the estimation of skills of the phase and amplitudes of the diurnal rain using these member models, their ensemble mean, a multimodel superensemble, and those from a single unified model. Test results are presented for the global tropics and for some specific regions where the member models show difficulty in predicting the diurnal change of rainfall. The main contribution is the considerable improvement of the modeling of diurnal rain by deploying a multimodel superensemble and by constructing a single unified model. The authors also present a comparison of these findings on the modeling of diurnal rain from another suite of multimodels that utilized different versions of cloud radiation algorithms (instead of different cumulus parameterization schemes) toward defining the suite of multimodels. The principal result is that the superensemble does provide a future forecast for the total daily rain and for the diurnal change of rain through day 5 that is superior to forecasts provided by the best model. The training of the superensemble with good observed estimates of rain, such as those from TRMM, is necessary for such forecasts.

The Impacts of Convective Parameterization and Moisture Triggering on AGCM-Simulated Convectively Coupled Equatorial Waves

Abstract This study examines the impacts of convective parameterization and moisture convective trigger on convectively coupled equatorial waves simulated by the Seoul National University (SNU) atmospheric general circulation model (AGCM). Three different convection schemes are used, including the simplified Arakawa–Schubert (SAS) scheme, the Kuo (1974) scheme, and the moist convective adjustment (MCA) scheme, and a moisture convective trigger with variable strength is added to each scheme. The authors also conduct a “no convection” experiment with deep convection schemes turned off. Space–time spectral analysis is used to obtain the variance and phase speed of dominant convectively coupled equatorial waves, including the Madden–Julian oscillation (MJO), Kelvin, equatorial Rossby (ER), mixed Rossby–gravity (MRG), and eastward inertio-gravity (EIG) and westward inertio-gravity (WIG) waves. The results show that both convective parameterization and the moisture convective trigger have significant impacts on AGCM-simulated, convectively coupled equatorial waves. The MCA scheme generally produces larger variances of convectively coupled equatorial waves including the MJO, more coherent eastward propagation of the MJO, and a more prominent MJO spectral peak than the Kuo and SAS schemes. Increasing the strength of the moisture trigger significantly enhances the variances and slows down the phase speeds of all wave modes except the MJO, and usually improves the eastward propagation of the MJO for the Kuo and SAS schemes, but the effect for the MCA scheme is small. The no convection experiment always produces one of the best signals of convectively coupled equatorial waves and the MJO.

Estudo numérico do papel dos esquemas de convecção na simulação de um evento severo nos extratrópicos do Brasil

A comparison study of the Kuo and Grell cumulus parameterizations schemes (CPSs), was conducted using the Brazilian Regional Modeling System (BRAMS), for to evaluate this role in severe storms simulation. In this context, we analyzed a cold front case on Brazil south region, occurred on December 11, 2003. The experiments are identical, except from the CPSs difference: the SCKUO experiment uses the Kuo scheme and the SCGRELL experiment uses the Grell scheme. The evaluation of the simulated precipitation focuses on comparison of two aspects: Intensity and areal coverage. Also we analyzed the convective parameters simulation conceived to identify atmospheric environments favorable for the severe convection. The accumulated precipitation simulated from SCKUO underestimated the observed data, but better represented the areal coverage. The accumulated precipitation simulated from SCGRELL better represented the rain intensity, but overestimated the observed data. Therefore, the better option, for this convection case, is the Grell Parameterization. Both experiments simulated the convective parameters with good approximation, with emphasis in Grell scheme. This result showed that the mesoscale model is a useful tool in the identification of atmospheric environments favorable for the development of severe convective storms, with great CPSs contribution.

An Evaluation of a Mass-Flux Cumulus Parameterization Scheme in the KMA Global Forecast System

A mass-flux type cumulus parameterization scheme is evaluated in the Korea Meteorological Administration (KMA)’s Global Data Assimilation and Prediction System (GDAPS). Two sets of parallel assimilation runs, with a horizontal resolution corresponding to the spectral truncation of T213, approximately 50 km, are designed, one with the operational Kuo convection scheme, and another with a simplified Arakawa-Schubert (SAS) convection scheme, for the month of July 2001, which was a typical summer monsoon period in Korea. An additional sensitivity experiment, that excludes the moist downdrafts in the SAS scheme, is conducted. A 10-day forecast cycle is run, within a data assimilation window, beginning at every 1200 UTC in July 2001. A heavy rainfall event, that occurred in the Korean peninsula on 14-15 July 2001, is investigated in detail.For the heavy rainfall case, the SAS scheme tends to reduce the precipitation amount, as compared to the Kuo scheme. It is found that the exclusion of moist downdrafts in the SAS scheme, increases drying and heating rates, resulting in enhanced rainfall, as shown in the Kuo scheme. The monthly verification demonstrates that the systematic warm bias in the lower troposphere in the operational model is nearly absent when the SAS scheme is employed. In terms of statistical measure of the skill for the predicted sea-level pressure, and that for the upper level patterns, the experiment with the SAS (Kuo) scheme out-performs in the northern (southern) hemisphere. In the case of precipitation forecasts, the SAS scheme effectively corrects the spurious excessive precipitation over the tropical land area, due to the inclusion of moist downdrafts. However, the reduction in precipitation in the SAS scheme, deteriorates the forecast skill for high precipitation categories.

Inter-comparison of 10-year precipitation simulated by several RCMs for Asia

In phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia, the regional climate has been simulated for July 1988 through December 1998 by five regional climate models and one global variable resolution model. Comparison of the 10-year simulated precipitation with the observations was carried out. The results show that most models have the capacity to reproduce the basic spatial pattern of precipitation for Asia, and the main rainbelt can be reproduced by most models, but there are distinctions in the location and the intensity. Most models overestimate the precipitation over most continental regions. Interannual variability of the precipitation can also be basically simulated, while differences exist between various models and the observations. The biases in the stream field are important reasons behind the simulation errors of the Regional Climate Models (RCMs). The cumulus scheme and land surface process have large influences on the precipitation simulation. Generally, the Grell cumulus scheme produces more precipitation than the Kuo scheme.

A comparison of cumulus parameterization schemes in a numerical weather prediction model for a monsoon rainfall event

In order to evaluate cumulus parameterization (CP) schemes for hydrological applications, the Pennsylvania State University–National Center for Atmospheric Research's fifth-generation mesoscale model (MM5) was used to simulate a summer monsoon in east China. The performances of five CP schemes (Anthes–Kuo, Betts–Miller, Fritsch–Chappell, Kain–Fritsch, and Grell) were evaluated in terms of their ability to simulate amount of rainfall during the heavy, moderate, and light phases of the event. The Grell scheme was found to be the most robust, performing well at all rainfall intensity and spatial scales. The Betts–Miller scheme also performed well, particularly at larger scales, but its assumptions may make it inapplicable to non-tropical environments and at smaller scales. The Kain–Fritsch scheme was the best at simulating moderate rainfall rates, and was found to be superior to the Fritsch–Chappell scheme on which it was based. The Anthes–Kuo scheme was found to underpredict precipitation consistently at the mesoscale. Simulation performance was found to improve when schemes that included downdrafts were used in conjunction with schemes that did not include downdrafts. Copyright © 2005 John Wiley & Sons, Ltd.

Comparison of Cumulus Parameterizations and Entrainment Using Domain-Mean Wind Divergence in a Regional Model

Several different cumulus parameterizations are compared in a 10-day regional model simulation over the tropical Americas in northern summer. A simple bulk diagnostic test is devised, comparing the model's preferred domain-mean wind divergence profile with “observed” drivergence. The latter is obtained by a line integral of the normal wind component at the model's outer boundary, from the ECMWF reanalysis data used as lateral boundary conditions. The former is obtained from a line integral one grid point in from the boundary, a perimeter that encloses almost exactly the same region. Even though the model fields near the boundary are strongly nudged toward the ECMWF values, the difference is distinct, and indicative of systematic errors in the model's heating field throughout the interior of the domain. Heating reflects the effects of the convection scheme, both direct and indirect (e.g., through its impact on resolved condensation). A useful axis along which to characterize schemes appears to be overactive versus underactive. Underactive convective schemes tend to produce too little low-level convergence and upper-level divergence, while overactive schemes produce too much. This categorization is also reflected in rainfall fields, as overactive schemes produce widespread light convective rain while underactive schemes produce sparse occasional storms. For example, the Kain–Fritsch scheme is overactive with its default entraining-plume radius of 1500 m, a value optimized for midlatitudes over land. A value of 750 m makes the regional divergence magnitude about right, but makes the upper-tropospheric outflow altitude too low, illustrating a classic dilemma of entraining-plume models of convection. Schemes with other conceptual structures give widely varying divergence errors. The largest errors are found with the Anthes–Kuo scheme, while the smallest errors are found with the Betts–Miller–Janjic scheme, which has no consistent divergence bias over time. Diagnosis of other North American monsoon simulations supports the general underactive/ overactive characterization, but shows that the best scheme and parameters may depend on weather regime.