Mesoscale Model Results Research Articles

Coupled mesoscale–microscale modeling of air quality in a polluted city using WRF-LES-Chem

Abstract. To perform realistic high-resolution air quality modeling in a polluted urban area, the Weather Research and Forecasting (WRF) model is used with an embedded large-eddy simulation (LES) module and online chemistry. As an illustration, a numerical experiment is conducted in the megacity of Hong Kong, which is characterized by multi-type inhomogeneous pollution sources and complex topography. The results from the multi-resolution simulations at mesoscale and LES scales are evaluated by comparing them with ozone sounding profiles and surface observations. The comparisons show that both mesoscale and LES simulations reproduce the mean concentrations of the chemical species and their diurnal variations at the background stations well. However, the mesoscale simulations largely underestimate the NOx concentrations and overestimate O3 at the roadside stations due to the coarse representation of the traffic emissions. The LES simulations improve the agreement with the measurements near the road traffic, and the LES with the highest spatial resolution (33.3 m) provides the best results. The large-eddy simulations show more detailed structures in the spatial distributions of chemical species than the mesoscale simulations, highlighting the capability of LES to resolve high-resolution photochemical transformations in urban areas. Compared to the mesoscale model results, the LES simulations show similar evolutions in the profiles of the chemical species as a function of the boundary layer development over a diurnal cycle.

Dynamic response properties of polymer bonded explosives under different excitation by deceleration

Based on the experimental method of projectile penetration into the concrete target, different excitation by deceleration of polymer bonded explosives (PBXs) was achieved by controlling the length of steel pillars behind PBXs. A series of impact tests were conducted to study the mechanical response of PBXs with different initial densities under different excitation by deceleration. A physical model was developed to describe the viscoelastic-plastic deformation of PBXs. The plastic part was added on the basis of the viscoelastic statistical crack mechanical model (Visco-SCRAM) model, and the compaction behavior of charge in different environments was characterized based on the Heckel compaction equation. The model was implemented in LS-DYNA, and the simulation results were verified by the experiments. The dynamic mechanical behavior of PBXs under different excitation by deceleration was studied from the macroscopic and mesoscale aspects. The stress curves, strain curves, the density change and the interaction between particles in deceleration environment were predicted. After comparison and analysis, the dynamic response law of the charge in the penetrating process was obtained. Macroscopic responses along with mesoscale modeling results are significantly important to have a better understanding of deformation mechanisms of PBXs.

Mesoscale numerical modeling and characterization of the effect of reinforcement textile on the elevated temperature and tensile behaviour of carbon textile-reinforced concrete composite

This paper presents both experimental and mesoscale modeling results of the direct tensile behaviour of two carbon TRC composites at elevated temperatures ranging from 25 °C to 600 °C. Two reinforcement carbon textiles were manufactured industrially in the factory with different geometries and treatment products to improve the textile/matrix bond. For the numerical approach, the input data of the numerical models were chosen from the experimental results of TRC component materials (carbon textiles, cementitious matrix). The carbon TRCs gave the strain-hardening behaviour with different phases depending on elevated temperature levels. Furthermore, the numerical model highlighted the failure mode with the transversal cracks on the specimen surface, using the crack damage model for the concrete matrix. The effect of elevated temperature on the TRC behaviour and performance of the TRC was determined and analyzed by comparing it with the results obtained at room temperature. By comparing the experimental results on both carbon TRCs, the effect of the reinforcement textile on the thermomechanical behaviour of TRC composites could also be highlighted and discussed. The numerical results of the carbon TRCs at elevated temperature levels were also compared with experimental results. The good agreement obtained between the experimental and numerical results demonstrated the rationality of this numerical model.

CALIOPE-Urban v1.0: coupling R-LINE with a mesoscale air quality modelling system for urban air quality forecasts over Barcelona city (Spain)

Abstract. The NO2 annual air quality limit value is systematically exceeded in many European cities. In this context, understanding human exposure, improving policy and planning, and providing forecasts requires the development of accurate air quality models at the urban (street level) scale. We describe CALIOPE-Urban, a system coupling CALIOPE – an operational mesoscale air quality forecast system based on the HERMES (emissions), WRF (meteorology) and CMAQ (chemistry) models – with the urban roadway dispersion model R-LINE. Our developments have focused on Barcelona city (Spain), but the methodology may be replicated for other cities in the future. WRF drives pollutant dispersion and CMAQ provides background concentrations to R-LINE. Key features of our system include the adaptation of R-LINE to street canyons, the use of a new methodology that considers upwind grid cells in CMAQ to avoid double counting traffic emissions, a new method to estimate local surface roughness within street canyons, and a vertical mixing parameterisation that considers urban geometry and atmospheric stability to calculate surface level background concentrations. We show that the latter is critical to correct the night-time overestimations in our system. Both CALIOPE and CALIOPE-Urban are evaluated using two sets of observations. The temporal variability is evaluated against measurements from five traffic sites and one urban background site for April–May 2013. While both systems show a fairly good agreement at the urban background site, CALIOPE-Urban shows a better agreement at traffic sites. The spatial variability is evaluated using 182 passive dosimeters that were distributed across Barcelona during 2 weeks for February–March 2017. In this case, the coupled system also shows a more realistic distribution than the mesoscale system, which systematically underpredicts NO2 close to traffic emission sources. Overall CALIOPE-Urban improves mesoscale model results, demonstrating that the combination of both scales provides a more realistic representation of NO2 spatio-temporal variability in Barcelona.

Diurnal Cycle of Surface Winds in the Maritime Continent Observed through Satellite Scatterometry

AbstractThe diurnal cycle of surface winds throughout the Maritime Continent plays a significant role in the formation of precipitation over the islands of the region and over the surrounding seas. This study investigates the connection between the diurnal cycles of surface wind and offshore precipitation using data from four satellite scatterometer instruments and two satellite precipitation radar instruments. For the first time, data from three scatterometer instruments are combined to yield a more temporally complete picture of the surface wind diurnal cycles over the Maritime Continent’s surrounding seas. The results indicate that land–sea breezes typically propagate over 400 km offshore, produce mean wind perturbations of between 1 and 5 m s−1, and propagate as gravity waves at 25–30 m s−1. Diurnal precipitation cycles are affected through gravity wave propagation processes associated with the land–sea breezes, and through the convergence of land breezes from nearby islands. These observational results are then compared with previous mesoscale modeling results. It is shown that land–sea breezes occur too early, and are too intense in these modeling results, and this may partly explain why these modeling results also exhibit an early, overly intense diurnal precipitation cycle. This study also investigates variations in the diurnal cycle of surface winds at seasonal and intraseasonal time scales. Previous work has suggested that seasonal and intraseasonal variations in surface heating affect the land–sea breeze circulation and diurnal precipitation cycles; we argue that variations in background winds also play a defining role in modulating coastally influenced local winds.

Waterspout Forecasting Method Over the Eastern Adriatic Using a High-Resolution Numerical Weather Model

In this study, a synoptic and mesoscale analysis was performed and Szilagyi’s waterspout forecasting method was tested on ten waterspout events in the period of 2013–2016. Data regarding waterspout occurrences were collected from weather stations, an online survey at the official website of the National Meteorological and Hydrological Service of Croatia and eyewitness reports from newspapers and the internet. Synoptic weather conditions were analyzed using surface pressure fields, 500 hPa level synoptic charts, SYNOP reports and atmospheric soundings. For all observed waterspout events, a synoptic type was determined using the 500 hPa geopotential height chart. The occurrence of lightning activity was determined from the LINET lightning database, and waterspouts were divided into thunderstorm-related and “fair weather” ones. Mesoscale characteristics (with a focus on thermodynamic instability indices) were determined using the high-resolution (500 m grid length) mesoscale numerical weather model and model results were compared with the available observations. Because thermodynamic instability indices are usually insufficient for forecasting waterspout activity, the performance of the Szilagyi Waterspout Index (SWI) was tested using vertical atmospheric profiles provided by the mesoscale numerical model. The SWI successfully forecasted all waterspout events, even the winter events. This indicates that the Szilagyi’s waterspout prognostic method could be used as a valid prognostic tool for the eastern Adriatic.

Determination of chloromethane and dichloromethane in a tropical terrestrial mangrove forest in Brazil by measurements and modelling

Chloromethane (CH3Cl) and dichloromethane (CH2Cl2) are known to have both natural and anthropogenic sources to the atmosphere. From recent studies it is known that tropical and sub tropical plants are primary sources of CH3Cl in the atmosphere. In order to quantify the biogenic emissions of CH3Cl and CH2Cl2 from mangroves, field measurement were conducted in a tropical mangrove forest on the coast of Brazil. To the best of our knowledge these field measurements were the first of its kind conducted in the tropical mangrove ecosystem of Braganca. A mesoscale atmospheric model, MEsoscale TRAnsport and fluid (Stream) model (METRAS), was used to simulate passive tracers concentrations and to study the dependency of concentrations on type of emission function and meteorology. Model simulated concentrations were normalized using the observed field data. With the help of the mesoscale model results and the observed data the mangrove emissions were estimated at the local scale. By using this bottom-up approach the global emissions of CH3Cl and CH2Cl2 from mangroves were quantified. The emission range obtained with different emission functions and different meteorology are 4–7 Gg yr−1 for CH3Cl and 1–2 Gg yr2 for CH2Cl2. Based on the present study the mangroves contribute 0.3 percent of CH2Cl2 and 0.2 percent of CH3Cl in the global emission budget. This study corroborates the study by Manley et al. (2007) which estimated that mangroves produce 0.3 percent of CH3Cl in the global emission budget. Although they contribute a small percentage in the global budget, their long lifetime enables them to contribute to the destruction of ozone in the stratosphere. From the detailed analyses of the model results it can be concluded that meteorology has a larger influence on the variability of concentrations than the temporal variability of the emission function.

Reconstruction of Atmospheric Properties from Mars Science Laboratory Entry, Descent, and Landing

The successful Mars Science Laboratory entry, descent, and landing returned a wealth of in situ data that, when combined with orbiter remote sensing data and numerical modeling results, can be used to determine the state of the atmosphere. The entry atmosphere reconstruction included data from several sources: 1) temperature and pressure data from the Mars Reconnaissance Orbiter and Mars Climate Sounder instrument, 2) density derived from the Mars entry, descent, and landing instrument suite, 3) density derived from the vehicle’s inertial measurement unit and knowledge of the vehicle aerodynamics, and 4) numerical mesoscale model results. No single data set is sufficient to understand the atmospheric state along the path flown by the spacecraft. Rather, the reconstructed profile of density is pieced together from the available data, along with some assumptions and inferences. The strategy used to combine the various data sets required a clear understanding of each source’s strengths and weaknesses. The various data sets appear consistent and reinforce each other. From these data sets, a novel approach to anchoring reconstructed pressure data in the upper altitudes to observed data near the Gale Crater landing site is presented. The paper also describes how the anchoring technique, along with using postflight adjustments to mesoscale model data and in situ measurements are used to reconstruct the atmospheric state along the trajectory. The final reconstructed profile is compared with preflight predictions and implications of the new approach and lessons learned are also discussed.

Offshore winds mapped from satellite remote sensing

Around 2000 wind turbines in 58 offshore wind farms produce wind energy in the Northern European seas and many new wind farms are foreseen. The wind resource assessment is costly to observe using traditional meteorological masts and therefore atmospheric modeling is state of the art. However, to reduce the uncertainty on the model results on the offshore wind resource, it is necessary to compare model results with observations. Observations from ground‐based wind lidar and satellite remote sensing are the two main technologies that can provide new types of offshore wind data at relatively low cost. The advantages of microwave satellite remote sensing are (1) horizontal spatial coverage, (2) long data archives, and (3) high spatial detail both in the coastal zone and of far‐field wind farm wake. Passive microwave ocean wind speed data are available since 1987 with up to six observations per day with near‐global coverage. The data are particularly useful for investigation of long‐term wind conditions. Scatterometer ocean surface wind vectors provide a continuous series since 1999 with twice‐daily near‐global coverage. Both types of data have grid cells around 25 km. In contrast, synthetic aperture radar (SAR) wind maps can be retrieved at 1‐km grid resolution. SAR‐based wind maps have been used for wind resource assessment far offshore and in the coastal zones with good results when compared to e.g., meteorological data and mesoscale model results. High‐resolution SAR data show very long far‐field wind farm wakes. Thus wind farm wake loss is foreseen in wind farm clusters. WIREs Energy Environ 2014, 3:594–603. doi: 10.1002/wene.123This article is categorized under: Wind Power > Science and Materials

Diurnal variations of the low-level jet over peninsular India during the onset of Asian summer monsoon

The evidence for diurnal variation of monsoon low-level jet (MLLJ) over the southern tip of India is illustrated from observations, a mesoscale model results, and long-term reanalysis products. This illustration showed that MLLJ has a diurnal variation in its strength and location of maxima. Diurnal signature of MLLJ is not found to be location-specific. Stronger jets are formed at a lower elevation during the nighttime, and the jets are weaker during the day but are higher elevated. During the daytime, a secondary jet is also observed along with the MLLJ. Both the jets were numerically simulated during the onset phase of southwest monsoon over the southwest coast of India. Thirty-year climatological analysis from Modern Era Retrospective analysis for Research and Applications (MERRA) showed that the secondary jet is shallow and weak during the pre-onset phase of monsoon. With the progress of monsoon, the MLLJ gets stronger with increased wind speed and elevated location of its core. In occasions where the jet is strong before the onset, the strongest jets proceed after the onset. Daytime MLLJ is higher elevated compared to the nocturnal MLLJ due to the frictional decoupling.

Are global wind power resource estimates overstated?

Estimates of the global wind power resource over land range from 56 to 400 TW. Most estimates have implicitly assumed that extraction of wind energy does not alter large-scale winds enough to significantly limit wind power production. Estimates that ignore the effect of wind turbine drag on local winds have assumed that wind power production of 2–4 W m−2 can be sustained over large areas. New results from a mesoscale model suggest that wind power production is limited to about 1 W m−2 at wind farm scales larger than about 100 km2. We find that the mesoscale model results are quantitatively consistent with results from global models that simulated the climate response to much larger wind power capacities. Wind resource estimates that ignore the effect of wind turbines in slowing large-scale winds may therefore substantially overestimate the wind power resource.

Coupling micro and meso-scale combustion models of AP/HTPB propellants

Combustion simulations at the micro and meso-scales are coupled to give a more theoretically based and accurate description of AP (ammonium perchlorate)/HTPB (hydroxyl-terminated polybutadiene) composite propellant combustion. One and two-dimensional micro-scale combustion models of AP and AP/HTPB, which include detailed kinetics and species transport, are utilized to define semi-global kinetics for a meso-scale propellant combustion model capable of representing the complex morphology of an actual propellant. The AP/HTPB flame structure predicted with the micro-scale models is separated into four flames. Each flame is represented with a single reaction, thus a new four-step kinetic mechanism is implemented into the meso-scale model. Physical and kinetic parameters are determined with the micro-scale models. The meso-scale model is calibrated and validated with the micro-scale models to ensure the correct flame structure, as a function of pressure and AP particle sizes, is recreated with the four-step mechanism. The primary focus of this work is to outline the methodology used to couple the two numerical scales. Results of the meso-scale model are compared with the previous empirically-parameterized meso-scale model results and experimental data. Predictions are within 10% of experimental values for a range of AP/HTPB propellants.

Performance of Regional Integrated Environment Modeling System (RIEMS) in the Simulation of Surface Air Temperature over East Asia

Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs). These advantages have drawn signifi...

Atmospheric boundary layer wind profile at a flat coastal site – wind speed lidar measurements and mesoscale modeling results

Abstract. Wind profiles up to 600 m height are investigated. Measurements of mean wind speed profiles were obtained from a novel wind lidar and compared to model simulations from a mesoscale model (WRF-ARW v3.1). It is found that WRF is able to predict the mean wind profile rather well and typically within 1–2 m s−1 to the individual measured values. WRF underpredicts the normalized wind profile, especially for stable conditions. The effect of baroclinicity on the upper part of the wind profile is discussed.

California offshore wind energy potential

This study combines multi-year mesoscale modeling results, validated using offshore buoys with high-resolution bathymetry to create a wind energy resource assessment for offshore California (CA). The siting of an offshore wind farm is limited by water depth, with shallow water being generally preferable economically. Acceptable depths for offshore wind farms are divided into three categories: ≤20 m depth for monopile turbine foundations, ≤50 m depth for multi-leg turbine foundations, and ≤200 m depth for deep water floating turbines. The CA coast was further divided into three logical areas for analysis: Northern, Central, and Southern CA. A mesoscale meteorological model was then used at high horizontal resolution (5 and 1.67 km) to calculate annual 80 m wind speeds (turbine hub height) for each area, based on the average of the seasonal months January, April, July, and October of 2005/2006 and the entirety of 2007 (12 months). A 5 MW offshore wind turbine was used to create a preliminary resource assessment for offshore CA. Each geographical region was then characterized by its coastal transmission access, water depth, wind turbine development potential, and average 80 m wind speed. Initial estimates show that 1.4–2.3 GW, 4.4–8.3 GW, and 52.8–64.9 GW of deliverable power could be harnessed from offshore CA using monopile, multi-leg, and floating turbine foundations, respectively. A single proposed wind farm near Cape Mendocino could deliver an average 800 MW of gross renewable power and reduce CA's current carbon emitting electricity generation 4% on an energy basis. Unlike most of California's land based wind farms which peak at night, the offshore winds near Cape Mendocino are consistently fast throughout the day and night during all four seasons.

Simulation of Atmospheric Dispersion of Elevated Releases from Point Sources in Mississippi Gulf Coast with Different Meteorological Data

Atmospheric dispersion calculations are made using the HYSPLIT Particle Dispersion Model for studying the transport and dispersion of air-borne releases from point elevated sources in the Mississippi Gulf coastal region. Simulations are performed separately with three meteorological data sets having different spatial and temporal resolution for a typical summer period in 1–3 June 2006 representing a weak synoptic condition. The first two data are the NCEP global and regional analyses (FNL, EDAS) while the third is a meso-scale simulation generated using the Weather Research and Forecasting model with nested domains at a fine resolution of 4 km. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of the combined influences of the land-sea breeze circulation, the large scale flow field and diurnal alteration in the mixing depth across the coast. The model predicted SO2 concentrations showed that the trajectory and the concentration distribution varied in the three cases of input data. While calculations with FNL data show an overall higher correlation, there is a significant positive bias during daytime and negative bias during night time. Calculations with EDAS fields are significantly below the observations during both daytime and night time though plume behavior follows the coastal circulation. The diurnal plume behavior and its distribution are better simulated using the mesoscale WRF meteorological fields in the coastal environment suggesting its suitability for pollution dispersion impact assessment in the local scale. Results of different cases of simulation, comparison with observations, correlation and bias in each case are presented.

Some Observational and Modeling Studies of the Atmospheric Boundary Layer at Mississippi Gulf Coast for Air Pollution Dispersion Assessment

Coastal atmospheric conditions widely vary from those over inland due to the land-sea interface, temperature contrast and the consequent development of local circulations. In this study a field meteorological experiment was conducted to measure vertical structure of boundary layer during the period 25-29 June, 2007 at three locations Seabee base, Harrison and Wiggins sites in the Mississippi coast. A GPS Sonde along with slow ascent helium balloon and automated weather stations equipped with slow and fast response sensors were used in the experiment. GPS sonde were launched at three specific times (0700 LT, 1300 LT and 1800 LT) during the experiment days. The observations indicate shallow boundary layer near the coast which gradually develops inland. The weather research and forecasting (WRF) meso-scale atmospheric model and a Lagrangian particle dispersion model (HYSPLIT) are used to simulate the lower atmospheric flow and dispersion in a range of 100 km from the coast for 28-30 June, 2007. The simulated meteorological parameters were compared with the experimental observations. The meso-scale model results show significant temporal and spatial variations in the meteorological fields as a result of development of sea breeze flow, its coupling with the large scale flow field and the ensuing alteration in the mixing depth across the coast. Simulated ground-level concentrations of SO2 from four elevated point sources located along the coast indicate diurnal variation and impact of the local sea-land breeze on the direction of the plume. Model concentration levels were highest during the stable morning condition and during the sea-breeze time in the afternoon. The highest concentrations were found up to 40 km inland during sea breeze time. The study illustrates the application of field meteorological observations for the validation of WRF which is coupled to HYSPLIT for dispersion assessment in the coastal region.

Mesoscale modelling of water vapour in the tropical UTLS: two case studies from the HIBISCUS campaign

Abstract. In this study, we evaluate the ability of the BRAMS (Brazilian Regional Atmospheric Modeling System) mesoscale model compared to ECMWF global analysis to simulate the observed vertical variations of water vapour in the tropical upper troposphere and lower stratosphere (UTLS). The observations are balloon-borne measurements of water vapour mixing ratio and temperature from micro-SDLA (Tunable Diode Laser Spectrometer) instrument. Data from two balloon flights performed during the 2004 HIBISCUS field campaign are used to compare with the mesoscale simulations and to the ECMWF analysis. The observations exhibit fine scale vertical structures of water vapour of a few hundred meters height. The ECMWF vertical resolution (~1 km) is too coarse to capture these vertical structures in the UTLS. With a vertical resolution similar to ECMWF, the mesoscale model performs better than ECMWF analysis for water vapour in the upper troposphere and similarly or slightly worse for temperature. The BRAMS model with 250 m vertical resolution is able to capture more of the observed fine scale vertical variations of water vapour compared to runs with a coarser vertical resolution. This is mainly related to: (i) the enhanced vertical resolution in the UTLS and (ii) to the more detailed microphysical parameterization providing ice supersaturations as in the observations. In near saturated or supersaturated layers, the mesoscale model predicted relative humidity with respect to ice saturation is close to observations provided that the temperature profile is realistic. For temperature, the ECMWF analysis gives good results partly attributed to data assimilation. The analysis of the mesoscale model results showed that the vertical variations of the water vapour profile depends on the dynamics in unsaturated layer while the microphysical processes play a major role in saturated/supersaturated layers. In the lower stratosphere, the ECMWF model and the BRAMS model give very similar water vapour profiles that are significantly drier than micro-SDLA measurements. This similarity comes from the fact that BRAMS is initialised using ECMWF analysis and that no mesoscale process acts in the stratosphere leading to no modification of the BRAMS results with respect to ECMWF analysis.

Examination of the Bouchet–Morton Complementary Relationship Using a Mesoscale Climate Model and Observations under a Progressive Irrigation Scenario

AbstractThe complementary relationship between actual and potential evaporation over southeastern Turkey was examined using a mesoscale climate model and field data. Model simulations of both actual and potential evaporation produce realistic temporal patterns in comparison to those estimated from field data; as evaporation from the surface increases with increasing irrigation, potential evaporation decreases. This is in accordance with the Bouchet–Morton complementary relationship and suggests that actual evapotranspiration can be readily computed from routine meteorological observations. The driving mechanisms behind irrigation-related changes in actual and potential evaporation include reduced wind velocities, increased atmospheric stability, and depressed humidity deficits. The relative role of each in preserving the complementary relation is assessed by fitting a potential evaporation model to pan evaporation data. The importance of reduced wind velocity in maintaining complementarity was unexpected, and thus examined further using a set of perturbation simulation experiments with changing roughness parameters (reflecting growing cotton crops), changing moisture conditions (reflecting irrigation), and both. Three potential causes of wind velocity reduction associated with irrigation may be increased surface roughness, decreased thermal convection that influences momentum transfer, and the development of anomalous high pressure that counteracts the background wind field. All three are evident in the mesoscale model results, but the primary cause is the pressure-induced local wind system. The apparent necessity of capturing mesoscale dynamical feedbacks in maintaining complementarity between potential and actual evaporation suggests that a theory more complicated than current descriptions (which are based on feedbacks between actual evaporation and temperature and/or humidity gradients) is required to explain the complementary relationship.

On the Influences of Vertical Wind Shear on Symmetric Tropical Cyclone Structure Derived from AMSU

Abstract Axisymmetric temperatures and gradient-balanced winds associated with tropical cyclones derived from the Advanced Microwave Sounding Unit are stratified by the 24-h averaged vector difference of the horizontal wind between 200 and 850 hPa (or vertical wind shear). Using 186 total cases that are limited to tropical cyclones with intensities greater than 33 m s−1 (or mature) and are located over sea surface temperatures greater than 26.4°C, vertical wind shear–based composites are created. Results show that as the vertical wind shear increased, the upper-level warm-core structure associated with the tropical cyclone descended, resulting in a shallower balanced vortex. These observationally based results are presented in the context of recent mesoscale modeling results of the effect of shear on tropical cyclone structure.