MM5 Modeling System Research Articles

Evaluating the performance of an integrated CALPUFF-MM5 modeling system for predicting SO2 emission from a refinery

Oil refineries are one of the proven sources of environmental pollution as they emit more than 100 chemicals into the atmosphere including sulfur dioxide (SO2). The dispersion patterns of SO2 from emissions of Sohar refinery was simulated by employing California Puff (CALPUFF) model integrated with state of the art meteorological Mesoscale Model (MM5). The results of this simulation were used to quantify the ground level concentrations of SO2 in and around the refinery. The evaluation of the CALPUFF and MM5 modeling system was carried out by comparing the estimated results with that of observed data of the same area. The predicted concentrations of SO2 agreed well with the observed data, with minor differences in magnitudes. In addition, the ambient air quality of the area was checked by comparing the model results with the regulatory limits for SO2 set by the Ministry of Environment and Climate Affairs (MECA) in Oman. From the analysis of results, it was found that the concentration of SO2 in the nearby communities of Sohar refinery is well within the regulatory limits specified by MECA. Based on these results, it was concluded that no health risk, due to SO2 emissions, is present in areas adjacent to the refinery.

Regional climate simulations for the European Alpine Region—sensitivity of precipitation to large-scale flow conditions of driving input data

The MM5 modelling system has been used to perform regional climate simulations over Western Europe on a 45-km grid for the years 1971 to 2000. We focus our analysis on the impact of the driving input data on simulated precipitation in the Alpine area. Using ERA40 reanalysis data, the MM5 climatology of precipitation compares reasonably well with an observational climatology for the Alpine region. Switching to an ECHAM5 climate simulation as driving data induces excessive overprediction by up to 80% in the colder seasons there, primarily over the Alpine slopes. The large-scale flow provided by the global datasets revealed moderate differences indicating an increased number of low-pressure systems travelling from the Atlantic into the Alpine region for ECHAM5 compared with ERA40. Mean seasonal 700-hPa wind speeds correspondingly showed higher values for the ECHAM5 driven simulation in the central Alps. Partitioning three-hourly 700-hPa winds according to direction and speed in the central Alps specifically revealed a distinct shift to stronger westerly and north-westerly winds. Furthermore, aggregating three-hourly rainfall amounts to the same wind direction and wind speed intervals as for the wind statistics revealed strongly intensified precipitation due to the overly intense westerly winds, implying too intense orographic precipitation enhancement.

On the relationship between soil, vegetation and severe convective storms: Hungarian case studies

The effects of soil hydraulic parameter and stomatal functioning parameterization changes upon the precipitation fields of storms were compared and analyzed. The analysis was performed using results from the Penn State-NCAR MM5 Modeling System. Two sets of soil hydraulic parameters, from the USA and Hungary, were used. Stomatal functioning is parameterized as simply as possible using Jarvis' approach. The days chosen for analysis (18th April 2005 and 7th August 2006) seemed to be favourable for local storms to form when the land-surface/air interaction is the strongest. Both days were wet, however, the prevailing moisture was somewhat larger on 18th April 2005. Precipitation fields were statistically analyzed in details. First, the simulated and observed fields were compared. The observed fields were estimated from rain-gauge data applying the ordinary block kriging interpolation technique. The agreement between the simulated and observed fields was estimated using categorical and continuous verification indices. Significance tests were done to estimate how large the obtained differences were. The results obtained indicate that precipitation fields are at least as sensitive to changes in soil hydraulic parameters as to changes in stomatal functioning parameterization. The simple Student t-test hypothesis was applied to estimate how large the precipitation differences obtained were. According to the estimates, the TSS differences obtained by soil parameter and stomatal functioning parameterization changes are significant on the 10% level. The acquired differences do not depend on the initialization of soil moisture. The results suggest that all weather and climate models used for regional purposes should prefer local soil data instead of some common globally used soil datasets. This is at least as important as the parameterization of stomatal functioning.

SMOKE 모델의 입력 모듈 변경에 따른 영향 분석

Emission input modules was developed to produce emission input data and change some profiles for Sparse Matrix Operator Kernel Emissions (SMOKE) using Clean Air Policy Support System (CAPSS)`s activities and previous studies. Specially, this study was focused to improve chemical speciation and temporal allocation profiles of SMOKE. At first, SCC cord mapping was done. 579 SCC cords of CAPSS were matched with EPA`s one. Temporal allocation profiles were changed using CAPSS monthly activities. And Chemical speciation profiles were substituted using Kang et al. (2000) and Lee et al. (2005) studies and Kim et al. (2005) study. Simulation in Seoul Metropolitan Area (Seoul, Incheon, Gyeonggi) using MM5, SMOKE and CMAQ modeling system was done for effect analysis of changed input modules of SMOKE. Emission model results adjusted with new input modules were slightly changed as compared to using EPA`s default modules. SMOKE outputs shows that aldehyde emissions were decreased 4.78% after changing chemical profiles, increased 0.85% after implementing new temporal profiles. Toluene emissions were decreased 18.56% by changing chemical speciation profiles, increased 0.67% by replacing temporal profiles as well. Simulated results of air quality were also slightly elevated by using new input modules. Continuous accumulation of domestic data and studies to develop input system for air quality modeling would produce more improved results of air quality prediction.

Evaluation of Proposed Winter PM Concentration Reduction Strategies Using the MM5 and CAMx4 Modelling System - Christchurch, New Zealand, 2005-2013

Mesoscale Model (MM5) and Eulerian Comprehensive Air quality Model (CAMx4) were used to evaluate dispersion of particulate matter (PM) generated by ”Total” emissions for Christchurch (New Zealand) for winter 2005. ”Total” emissions consist of the ”Domestic”, ”Transport” and ”Industry” emissions. A composite chemical scenario generated from transport-related (day-time) and domestic-related (night-time) chemical scenarios was shown to be an optimal chemical split of input gridded emissions for predicting PM concentrations with minimal error when compared with ambient data. Reduction of gridded emissions of fine (PM2.5) and total (PM10) aerosol from domestic and transport sources can be achieved by linear reduction of the PM emissions in the emissions groups, as well as by non-linear reduction in the groups by varying the percentage of each chemical component of the scenario used to chemically split the PM input gridded emissions. Results of comparison of the linear and non-linear reduction for winter 2005 heavy smog episodes support the reliability of the 1999 inventory. The predicted linear and non-linear reduced PM values belong to the same population with correlation coefficients of 0.88 to 0.98. Based on these results, a sequence of experiments has been conducted to evaluate the potential decrease of PM winter concentrations over the 2005-2013 time period, using proposed reduction of PM winter emissions (in both the ”Domestic” and ”Transport” groups) using the linear reduction scheme. Two different abatement strategies outlined by the New Zealand Ministry for the Environment (MfE) to reduce aerosol concentrations and to achieve compliance with the PM reduction plan (target year 2013) were studied numerically using proposed aerosol emissions reductions.

The impact of the PBL scheme and the vertical distribution of model layers on simulations of Alpine foehn

This paper investigates the influence of the planetary boundary-layer (PBL) parameterization and the vertical distribution of model layers on simulations of an Alpine foehn case that was observed during the Mesoscale Alpine Programme (MAP) in autumn 1999. The study is based on the PSU/NCAR MM5 modelling system and combines five different PBL schemes with three model layer settings, which mainly differ in the height above ground of the lowest model level (z1). Specifically, z1 takes values of about 7 m, 22 m and 36 m, and the experiments with z1 = 7 m are set up such that the second model level is located at z = 36 m. To assess if the different model setups have a systematic impact on the model performance, the simulation results are compared against wind lidar, radiosonde and surface measurements gathered along the Austrian Wipp Valley. Moreover, the dependence of the simulated wind and temperature fields at a given height (36 m above ground) on z1 is examined for several different regions.

Assessing uncertainties in dust emission in the Aral Sea region caused by meteorological fields predicted with a mesoscale model

This study investigates how the choice of the planetary boundary layer (PBL) parameterization and dust emission scheme affects the prediction of dust entrainment simulated with a regional mesoscale model. For this analysis we consider a representative dust episode which occurred on April 2001 in the Aral Sea region. The meteorological fields were simulated using the PSU/NCAR MM5 modeling system considering two different boundary layer parameterizations. In each case, emitted dust fluxes were computed off-line by incorporating MM5 meteorological fields into the dust module DuMo. Several dust emission schemes with a prescribed erodible fraction and fixed threshold wind speed were the subject of our analysis. Implications to assessment of the anthropogenic fraction of dust emitted in the Aral region were investigated by conducting the full, half, and no lake modeling experiments. Our results show that the discrepancies in dust fluxes between the two different PBLs are much higher compared to the discrepancy associated with the use of considered dust production schemes. Furthermore, the choice of the PBL affects the timing and duration of a modeled dust event. We demonstrate that different combinations of the PBL parameterization and wind- or friction velocity-driven dust emission schemes can result in up to about a 50% difference in predicted dust mass caused by the Aral Sea desiccation. We found that the drying-up of the Aral cannot only affect the dust emission by expanding the source area, but also by affecting atmospheric characteristics, especially winds. These competitive factors add further complexity to quantification of the anthropogenic dust fraction in the region.

A regional climate study of Central America using the MM5 modeling system: results and comparison to observations

The Mesoscale Modeling system, version 3.6 (MM5) regional modeling system has been applied to Central America and has been evaluated against National Oceanic and Atmospheric Administration/National Climatic Data Center (NOAA/NCDC) daily observations and the Global Precipitation Climatology Project (GPCP) precipitation data. We compare model results and observations for 1997 and evaluate various climate parameters (temperature, wind speed, precipitation and water vapor mixing ratio), emphasizing the differences within the context of the station dependent geographical features and the land use (LU) categories. At 9 of the 16 analyzed stations the modeled temperature, wind speed and vapor mixing ratio are in agreement with observations with average model-observation differences consistently lower than 25%. MM5 has better performance at stations strongly impacted by monsoon systems, regions typified by low topography in coastal areas and areas characterized by evergreen, broad-leaf and shrub land vegetation types. At four stations the model precipitation is about a factor of 3–5 higher than the observations, while the simulated wind is roughly twice what is observed. These stations include two inland stations characterized by croplands close to water bodies; one coastal station in El Salvador adjacent to a mountain-based cropland area and one station at sea-level. This suggests that the model does not adequately represent the influence of topographic features and water bodies close to these stations. In general, the model agrees reasonably well with measurements and therefore provides an acceptable description of regional climate. The simulations in this study use only two seasonal maps of land cover. The main model discrepancies are likely attributable to the actual annual cycle of land–atmosphere vapor and energy exchange that has a temporal scale of days to weeks. These fluxes are impacted by surface moisture availability, albedo and thermal inertia parameters. Copyright © 2006 Royal Meteorological Society.

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.

Circulation characteristics of a monsoon depression during BOBMEX-99 using high-resolution analysis

The skill and efficiency of a numerical model mostly varies with the quality of initial values, accuracy on parameterization of physical processes and horizontal and vertical resolution of the model. Commonly used low-resolution reanalyses are hardly able to capture the prominent features associated with organized convective processes in a monsoon depression. The objective is to prepare improved high-resolution analysis by the use of MM5 modelling system developed by the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR). It requires the objective comparison of high and low-resolution analysis datasets in assessing the specific convective features of a monsoon depression. For this purpose, reanalysis datasets of NCAR/NCEP (National Center for Atmospheric Research/National Centers for Environmental Prediction) at a horizontal resolution of 2.5‡ (latitude/longitude) have been used as first guess in the objective analysis scheme. The additional asynoptic datasets obtained during BOBMEX-99 are utilized within the assimilation process. Cloud Motion Wind (CMW) data of METEOSAT satellite and SSM/I surface wind data are included for the improvement of derived analysis. The multiquadric (MQD) interpolation technique is selected and applied for meteorological objective analysis at a horizontal resolution of 30 km. After a successful inclusion of additional data, the resulting reanalysis is able to produce the structure of convective organization as well as prominent synoptic features associated with monsoon depression. Comparison and error verifications have been done with the help of available upper-air station data. The objective verification reveals the efficiency of the analysis scheme.

Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part II: Preliminary Model Validation

A number of short-term numerical experiments conducted by the Penn State‐NCAR fifth-generation Mesoscale Model (MM5) coupled with an advanced land surface model, alongside the simulations coupled with a simple slab model, are verified with observations. For clear sky day cases, the MM5 model gives reasonable estimates of radiation forcing at the surface with solar radiation being slightly overestimated probably due to the lack of aerosol treatment in the current MM5 radiation scheme. The improvements in the calculation of surface latent and sensible heat fluxes with the new land surface model (LSM) are very apparent, and more importantly, the new LSM captures the correct Bowen ratio. Evaporation obtained from the simple slab model is significantly lower than observations. Having time-varying soil moisture is important for capturing even short-term evolution of evaporation. Due to the more reasonable diurnal cycle of surface heat fluxes in the MM5‐LSM, its nearsurface temperature and humidity are closer to the FIFE observations. In particular, the MM5‐slab model has a systematic warm bias in 2-m temperature. Both the slab model and the new LSM were coupled with the nonlocal Medium-Range Forecast model PBL parameterization scheme and they reproduced the depth of the morning surface inversion in the stable boundary layer well. The observed mixed layer in the late morning deepens faster than both models, despite the fact that both models have high bias in surface sensible heat fluxes. Presumably, such a rapid development of convective mixed layer is due to some effects induced by small-scale heterogeneity or large-scale advection that the MM5 failed to capture. Both surface models reasonably reproduce the daytime convective PBL growth and, in general, the temperature difference between the two models and observations is less than 28. The simulations of two rainfall events are not conclusive. Both models produce a good forecast of rainfall for 24 June 1997 and have similar problems for the event of 4 July 1997, although the simulations with the new LSM have slightly improved results in some 3-h rainfall accumulations. It seems that the new LSM does not have unexpected influences in situations for which the land surface processes are secondary, but that it may have subtle, though complex, effects on the model behavior because of heterogeneity introduced by soil moisture, vegetation effects, and soil type, which are all lacking in the slab model.

Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity

This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted here is that the land surface model should be able to provide not only reasonable diurnal variations of surface heat fluxes as surface boundary conditions for coupled models, but also correct seasonal evolutions of soil moisture in the context of a long-term data assimilation system. In a similar way to that in which the modified Oregon State University land surface model (LSM) has been used in the NCEP global and regional forecast models, it is implemented in MM5 to facilitate the initialization of soil moisture. Also, 1-km resolution vegetation and soil texture maps are introduced in the coupled MM5–LSM system to help identify vegetation/water/soil characteristics at fine scales and capture the feedback of these land surface forcings. A monthly varying climatological 0.15° × 0.15° green vegetation fraction is utilized to represent the annual control of vegetation on the surface evaporation. Specification of various vegetation and soil parameters is discussed, and the available water capacity in the LSM is extended to account for subgrid-scale heterogeneity. The coupling of the LSM to MM5 is also sensitive to the treatment of the surface layer, especially the calculation of the roughness length for heat/moisture. Including the effect of the molecular sublayer can improve the simulation of surface heat flux. It is shown that the soil thermal and hydraulic conductivities and the surface energy balance are very sensitive to soil moisture changes. Hence, it is necessary to establish an appropriate soil moisture data assimilation system to improve the soil moisture initialization at fine scales.

Numerical Simulations of an Observed Narrow Cold-Frontal Rainband

Abstract A cold-frontal rainband, which occurred during the afternoon of 28 December 1988, is numerically simulated using the Penn State–NCAR three-dimensional MM5 modeling system. This case is characterized by a line of severe convection that has a gravity current–like structure along the leading edge of a strong surface cold front. The authors test whether this gravity current–like structure is associated with the cold-air outflow boundary generated by the evaporation of hydrometeors from the postfrontal precipitation system. It is found that the neglect of moist processes in the model did not significantly affect the gravity current–like structure of the front. PBL (planetary boundary layer) frictional processes, which produce cross-frontal low-level wind shear (uz), play an important role. The role of this cross-frontal low-level wind shear is to generate low-level convergence and to steepen the frontal slope. Thus, the observed intense NCFR (narrow cold-frontal rainband) is closely related to frictio...