Surface Wind Direction Research Articles

Transverse Aeolian Ridges (TARs) on Mars II: Distributions, orientations, and ages

Transverse Aeolian Ridges (TARs), 10 m scale, ripple-like aeolian bedforms with simple morphology, are widespread on Mars but it is unknown what role they play in Mars’ wider sediment cycle. We present the results of a survey of all Mars Global Surveyor Narrow angle images in a pole-to-pole study area, 45° longitude wide. Following on from the classification scheme and preliminary surveys of Balme et al. (Balme, M.R., Berman, D.C., Bourke, M.C., Zimbelman, J.R. [2008a]. Geomorphology 101, 703–720) and Wilson and Zimbelman (Wilson, S.A., Zimbelman, J.R. [2004]. J. Geophys. Res. 109 (E10). doi: 10.1029/2004JE002247) we searched more than 10,000 images, and found that over 2000 reveal at least 5% areal cover by TARs. The mean TAR areal cover in the study area is about 7% (3% in the northern hemisphere and 11% in the southern hemisphere) but TARs are not homogenously distributed – they are concentrated in the mid-low latitudes and almost absent poleward of 35°N and 55°S. We found no clear correlation between TAR distribution and any of thermal inertia, kilometer-scale roughness, or elevation. We did find that TARs are less common at extremes of elevation. We found that TARs are most common near the equator (especially in the vicinity of Meridiani Planum, in which area they have a distinctive “barchan-like” morphology) and in large southern-hemisphere impact craters. TARs in the equatorial band are usually associated with outcrops of layered terrain or steep slopes, hence their relative absence in the northern hemisphere. TARs in the southern hemisphere are most commonly associated with low albedo, intercrater dune fields. We speculate that the mid-latitude mantling terrain (e.g., Mustard, J.F., Cooper, C.D., Rifkin, M.K. [2001]. Nature 412, 411–414; Kreslavsky, M.A., Head, J.W. [2002]. J. Geophys. Res. 29 (15). doi: 10.1029/2002GL015392) could also play a role in covering TARs or inhibiting saltation. We compared TAR distribution with general circulation model (GCM) climate data for both surface wind shear stress and wind direction. We performed GCM runs at various obliquity values to simulate the effects of changing obliquity on recent Mars climate. We found good general agreement between TAR orientation and GCM wind directions from present day obliquity conditions in many cases, but found no good correlation between wind shear stress and TAR distribution. We performed preliminary high resolution crater count studies of TARs in both equatorial and southern intracrater dunefield settings and compared these to superposition relationships between TARs and large dark dunes. Our results show that TARs near dunefield appear to be younger than TARs in the equatorial regions. We infer that active saltation from the large dunes keeps TARs active, but that TARs are not active under present day condition when distal to large dunes – perhaps supporting the interpretation that TARs are granule ripples. We conclude that local geology, rather than wind strength, controls TAR distribution, but that their orientation matches present-day regional wind patterns in most cases. We suggest that TARs are likely most (perhaps only) active today when they are proximal to large dark dune fields.

Changes in surface wind directions in Estonia during 1966–2008 and their relationships with large-scale atmospheric circulation

Changes in the percentages of eight main surface wind directions at 14 meteorological stations in Estonia, Northeast Europe, were studied during 1966-2008. Long-term changes in wind directions are related to variations in the large-scale atmospheric circulation but partly also to changes in the surroundings of the stations and in wind obstacles. Significant alterations in wind directions were determined, and found to be the strongest in the winter season. The percentages of W and SW winds have clear positive trends, while SE, E and NE winds are characterized by negative tendencies in winter. In conclusion, wind directions have probably been shifted from east to west. Differences in trends between the stations are explained by changes in wind obstacles around the stations. The trends in wind roses in Estonia were caused by the intensification of the westerly circulation over the Atlantic/European sector during the winter season.

Use of scatterometer based surface vorticity fields in forecasting genesis of tropical cyclones over the north Indian Ocean

Utilizing surface vorticity fields computed with the ocean surface wind speed and direction data obtained from QuikSCAT, a study has been undertaken to investigate the increase in surface vorticity during the genesis phase of tropical cyclones over the north Indian Ocean. Six named tropical cyclones; Agni, Hibaru, Mala, Akash, Nargis and Phyan which formed over the region during 2004-2009 have been selected for this purpose. It has been found that there was a steep rise in scatterometer based surface vorticity before the formation of a cyclone in the cyclogenesis region. The peak surface vorticity in the genesis region was observed on the day of intensification of the vortex to the depression stage or a day earlier. However, the rising trend in the genesis region begins a few days before the formation of the system. Thus, the surface vorticity fields derived on the basis of scatterometer data can provide predictive indication of the genesis of tropical cyclones over the Bay of Bengal and Arabian Sea with a lead time of 2-3 days. Using this technique it is possible to increase the lead time of pre-cyclone watch period over the north Indian Ocean.No relationship was found between the peak surface vorticity anomaly during the genesis phase and the surface vorticity anomaly at the time of peak intensity of the system during its life cycle. In other words, the peak surface vorticity anomaly during genesis phase does not provide any indication of future maximum intensity of the cyclone.

Use of scatterometer based surface vorticity fields in forecasting genesis of tropical cyclones over the north Indian Ocean

. Utilizing surface vorticity fields computed with the ocean surface wind speed and direction dataobtained from QuikSCAT, a study has been undertaken to investigate the increase in surface vorticity during the genesisphase of tropical cyclones over the north Indian Ocean. Six named tropical cyclones; Agni, Hibaru, Mala, Akash, Nargisand Phyan which formed over the region during 2004-2009 have been selected for this purpose. It has been found thatthere was a steep rise in scatterometer based surface vorticity before the formation of a cyclone in the cyclogenesisregion. The peak surface vorticity in the genesis region was observed on the day of intensification of the vortex to thedepression stage or a day earlier. However, the rising trend in the genesis region begins a few days before the formationof the system. Thus, the surface vorticity fields derived on the basis of scatterometer data can provide predictiveindication of the genesis of tropical cyclones over the Bay of Bengal and Arabian Sea with a lead time of 2-3 days. Usingthis technique it is possible to increase the lead time of pre-cyclone watch period over the north Indian Ocean.
 No relationship was found between the peak surface vorticity anomaly during the genesis phase and the surfacevorticity anomaly at the time of peak intensity of the system during its life cycle. In other words, the peak surfacevorticity anomaly during genesis phase does not provide any indication of future maximum intensity of the cyclone.

A new research on sea surface wind direction retrieval of synthetic aperture radar image

A new method to retrieve sea surface wind direction using synthetic aperture radar image is presented. Some pretreatment steps such as suppressing noise, down sampling and dividing into several sub-images are presented first. The method of two-dimensional numerical differentiation based on Tikhonov regularization is introduced to compute the gradient direction in the sub-image intensity of every point. The distance weighted objective function is used to compute the overall gradient direction in the sub-images. The retrieved wind direction is orthogonal to the overall gradient. When adding 10% of random errors, numerical simulations show that the result of numerical differentiation is better than that from the Sobel operator which is based on the finite difference method: the former error is 0.7293 , and the latter error is 13.5069 . Finally, an experiment based on real SAR data shows that the wind direction deviates from the overall direction determined by the method of Sobel operator, and the direction determined by the method of numerical differentiation is consistent well with the overall wind direction. Comparing the ship board wind direction and the corresponding location wind direction retrieved from the synthetic aperture radar sub-images with the two methods, the average result error of Sobel operator method is 9.0331, while that of numerical differentiation method is 1.1148. This new method is an effective and high accurate method to retrieve the sea surface wind direction of synthetic aperture radar image.

Aeolian scours as putative signatures of wind erosion and sediment transport direction on Mars

Obstacle marks, specifically current crescents (scours) formed by aeolian erosion, have not been previously identified on Mars from orbit. However, recent Mars Reconnaissance Orbiter images of an unnamed intracrater dune field within the Hellespontus region have shown innumerable meter-scale scours around fine and medium grade blocks. The types, relative numbers, and distributions of scour features served to determine, by proxy, the modes of surface wind direction and pathways of sediment transport across the crater floor. The orientations of scours of U-type morphology as well as the facing directions of leeward slopes for crescentic dunes (barchans and barchanoids) and megaripples were examined by statistical methods to determine their reference directions and dispersion of modal classes. We showed that although the dune field has evolved primarily under the influence of winds from the southwest, U-type scours have developed predominantly from a significant northwesterly wind direction. These data suggest that the dune field has evolved under the influence of a bimodal wind regime. Furthermore, such an aeolian system may help to explain the intermediary morphology between crescentic and linear for the central part of the dune field, in which the dunes appear to have undergone longitudinal as well as lateral sediment transport. In the absence of direct measurements of wind directions and strengths, current crescents offer detailed data from which planetary air flow at the surface–air interface can be better interpreted for the many intracrater settings across Mars.

Major Cold-Season Precipitation Events at Iqaluit, Nunavut

This study focuses on cold-season (October-April) precipitation events at Iqaluit, Nunavut, that exceed the 97th percentile of daily corrected precipitation accumulation. This corresponds to a threshold of 9.5 mm. The characteristics of 194 major precipitation events are described for the 1955 - 96 period. On the basis of NCEP-NCAR and NARR reanalysis data, these events were classified into four storm tracks: south, west, Atlantic, and other. South- and Atlantic-originating systems tended to be associated with the most severe events. The duration and precipitation rate of the events, rather than the speed of motion, were critical factors influencing precipitation accumulation. Snow was the dominant precipitation type. Surface warm frontal passage was a common tropospheric feature, and the topography was important in terms of altering surface wind direction during the events. No significant trend in the occurrence of major precipitation is evident.

Passive and Active L-Band Microwave Observations and Modeling of Ocean Surface Winds

L-band microwave backscatter and brightness temperature of sea surfaces acquired using the Passive/Active L-band Sensor during the High Ocean Wind campaign are reported in terms of their dependence on ocean surface wind speed and direction. We find that the L-band VV, HH, and HV radar backscatter data increase by 6-7 dB from 5 to 25 m/s wind speed at a 45° incidence angle. The data suggest the validity of Phased Array type L-band Synthetic Aperture Radar (PALSAR) HH model function between 5 and 15 m/s wind speeds, but show that the extrapolation of PALSAR model at above 20 m/s wind speeds overpredicts <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> coefficients. There is wind direction dependence in the radar backscatter with about 4 dB differences between upwind and crosswind observations at 24 m/s wind speed for VV and HH. The passive brightness temperatures show about a 5-K change for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub> and a 7-K change for <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> for a wind speed increasing from 5 to 25 m/s. Circle flight data suggest a wind direction response of about 1-2 K in <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</sub> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> at 14 and 24 m/s wind speeds. The L-band microwave data show excellent linear correlation with the surface wind speed with a correlation better than 0.95. The results support the use of L-band radar data for estimating the wind-driven excess brightness temperature of sea surfaces. The data also support the applications of L-band microwave signals for high-resolution (kilometer scale) observation of ocean surface winds under high wind conditions (10-28 m/s).

Directional Stability and Conservation of Scattering (DiSCS)-Based Directional-Ambiguity Removal Algorithm for Improving Wind Fields From Scatterometer: A QuikSCAT Example

A new directional-ambiguity removal algorithm has been developed for improving the wind fields derived from a scatterometer. Exploiting the natural spatial variability of ocean surface wind directions and invoking the conservation of backscattering, a new directional stability-weighted low-pass filter has been designed to complement the circular median filtering. It improves the directional-ambiguity removal by reducing the directional noise while retaining the natural wind flow. On the basis of analysis, which will be described later, indicating the lower spatial stability (conversely, the variability) of the wind direction and the lower direction-retrieval skills of the scatterometer-derived winds at low-intensity winds (<; 3 m/s) as compared to those for winds above 3 m/s, the ambiguity removal has been performed separately for these two wind regimes. The proposed Directional Stability and Conservation of Scattering (DiSCS) algorithm is applicable to the full swath of the scatterometer. Using the DiSCS algorithm, the wind fields derived from QuikSCAT Level-2A backscatter data over global oceans for 57 orbits during July 1-4, 2005, have been compared with the winds from the National Centers for Environmental Predictions and European Centre for Medium-Range Weather Forecasts models. Similar comparisons of QuikSCAT Level-2B finished products “direction interval retrieval with thresholded nudging” winds (referred to hereinafter as FP) with the winds from these two models have been performed. The QuikSCAT-derived winds are found to be closer to the model winds as compared to those QuikSCAT FP winds.

Rossby wave dynamics of the North Pacific extra-tropical response to El Niño: importance of the basic state in coupled GCMs

The extra-tropical response to El Niño in a “low” horizontal resolution coupled climate model, typical of the Intergovernmental Panel on Climate Change fourth assessment report simulations, is shown to have serious systematic errors. A high resolution configuration of the same model has a much improved response that is similar to observations. The errors in the low resolution model are traced to an incorrect representation of the atmospheric teleconnection mechanism that controls the extra-tropical sea surface temperatures (SSTs) during El Niño. This is due to an unrealistic atmospheric mean state, which changes the propagation characteristics of Rossby waves. These erroneous upper tropospheric circulation anomalies then induce erroneous surface circulation features over the North Pacific. The associated surface wind speed and direction errors create erroneous surface flux and upwelling anomalies which finally lead to the incorrect extra-tropical SST response to El Niño in the low resolution model. This highlights the sensitivity of the climate response to a single link in a chain of complex climatic processes. The correct representation of these processes in the high resolution model indicates the importance of horizontal resolution in resolving such processes.

Simulating wind channelling over Frobisher Bay and its interaction with downslope winds during the 7–8 November 2006 wind event

Previous observational studies have identified wind channelling over Frobisher Bay induced by pressure fields associated with cyclones as the main cause for the occurrence of strong and sustained surface winds at Iqaluit. The wind event of 7–8 November 2006, when a surface cyclone moved over the Labrador Sea, is representative of many such occurrences. Our simulations of the event with the Global Environmental Multiscale – Limited Area Model (GEM‐LAM 2.5 km) show an almost simultaneous development of wind channelling over Frobisher Bay and of downslope winds over the lee slopes of Hall Peninsula, as well as their interaction. The winds are caused by the passage of the same cyclone, but they advect different air masses. The channelled wind is initiated by a barrier jet generated as a result of the low‐level blocking of northeasterly winds by steep orography near the head of the bay. Later, it intensifies, while being driven primarily by large‐scale pressure gradients. The cross‐bay development of the channelled wind against the downslope wind over the lee slopes of Hall Peninsula explains the shift in surface wind direction and the high surface wind speeds recorded at Iqaluit. Some of the findings are also supported by data from radiosondes launched at Iqaluit. A short sensitivity study shows the beneficial effect of a distributed orographic drag parametrization on the near‐surface winds. The impact of using a modified Lenderink‐Holtslag mixing length and of increasing the vertical resolution near the surface are also addressed.

On the climatology of surface wind direction frequencies for the central Chilean coast

On the climatology of surface wind direction frequencies for the central Chilean coast

Bias Correction and Bayesian Model Averaging for Ensemble Forecasts of Surface Wind Direction

Abstract Wind direction is an angular variable, as opposed to weather quantities such as temperature, quantitative precipitation, or wind speed, which are linear variables. Consequently, traditional model output statistics and ensemble postprocessing methods become ineffective, or do not apply at all. This paper proposes an effective bias correction technique for wind direction forecasts from numerical weather prediction models, which is based on a state-of-the-art circular–circular regression approach. To calibrate forecast ensembles, a Bayesian model averaging scheme for directional variables is introduced, where the component distributions are von Mises densities centered at the individually bias-corrected ensemble member forecasts. These techniques are applied to 48-h forecasts of surface wind direction over the Pacific Northwest, using the University of Washington mesoscale ensemble, where they yield consistent improvements in forecast performance.

Assessing sensitivity of source term estimation

Source term estimation algorithms compute unknown atmospheric transport and dispersion modeling variables from concentration observations made by sensors in the field. Insufficient spatial and temporal resolution in the meteorological data as well as inherent uncertainty in the wind field data make source term estimation and the prediction of subsequent transport and dispersion extremely difficult. This work addresses the question: how many sensors are necessary in order to successfully estimate the source term and meteorological variables required for atmospheric transport and dispersion modeling? The source term estimation system presented here uses a robust optimization technique – a genetic algorithm (GA) – to find the combination of source location, source height, source strength, surface wind direction, surface wind speed, and time of release that produces a concentration field that best matches the sensor observations. The approach is validated using the Gaussian puff as the dispersion model in identical twin numerical experiments. The limits of the system are tested by incorporating additive and multiplicative noise into the synthetic data. The minimum requirements for data quantity and quality are determined by an extensive grid sensitivity analysis. Finally, a metric is developed for quantifying the minimum number of sensors necessary to accurately estimate the source term and to obtain the relevant wind information.

The Effects of SST-Induced Surface Wind Speed and Direction Gradients on Midlatitude Surface Vorticity and Divergence

Abstract The effects of surface wind speed and direction gradients on midlatitude surface vorticity and divergence fields associated with mesoscale sea surface temperature (SST) variability having spatial scales of 100–1000 km are investigated using vector wind observations from the SeaWinds scatterometer on the Quick Scatterometer (QuikSCAT) satellite and SST from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) Aqua satellite. The wind–SST coupling is analyzed over the period June 2002–August 2008, corresponding to the first 6+ years of the AMSR-E mission. Previous studies have shown that strong wind speed gradients develop in response to persistent mesoscale SST features associated with the Kuroshio Extension, Gulf Stream, South Atlantic, and Agulhas Return Current regions. Midlatitude SST fronts also significantly modify surface wind direction; the surface wind speed and direction responses to typical SST differences of about 2°–4°C are, on average, about 1–2 m s−1 and 4°–8°, respectively, over all four regions. Wind speed perturbations are positively correlated and very nearly collocated spatially with the SST perturbations. Wind direction perturbations, however, are displaced meridionally from the SST perturbations, with cyclonic flow poleward of warm SST and anticyclonic flow poleward of cool SST. Previous observational analyses have shown that small-scale perturbations in the surface vorticity and divergence fields are related linearly to the crosswind and downwind components of the SST gradient, respectively. When the vorticity and divergence fields are analyzed in curvilinear natural coordinates, the wind speed contributions to the SST-induced vorticity and divergence depend equally on the crosswind and downwind SST gradients, respectively. SST-induced wind direction gradients also significantly modify the vorticity and divergence fields, weakening the vorticity response to crosswind SST gradients while enhancing the divergence response to downwind SST gradients.

Impact of satellite surface-wind data on weather prediction

One of the important applications of satellite surface wind observations is to increase the accuracy of weather analyses and forecasts. The first satellite to measure surface wind over the oceans was Seasat in 1978. On board was a scatterometer, which measured radar backscatter from centimeter-scale capillary waves, from which surface wind speed and direction could be deduced. In more recent years, passive microwave remote sensing of the ocean surface has provided extensive observations of surface wind speed, and advanced scatterometers have been providing surface wind velocity data over the oceans. The initial impact of satellite surface wind data on weather analysis and forecasting was very small, but extensive research has been conducted since the early days of Seasat to improve the data accuracy and the utilization of these data in atmospheric models. Current satellite surface wind data are used to improve the detection of intense storms over the ocean, as well as to improve the overall representation of the wind field in numerical weather prediction models. As a result, these data are contributing to improved warnings for ships at sea and to improved global weather forecasts. Recent experiments conducted with data from the SeaWinds scatterometers aboard both Quikscat and ADEOS 2 indicate that increased coverage of scatterometer data can lead to even larger impacts than are routinely obtained now.

Estimation of the Surface Wind Speeds and Directions at Arbitrary Locations - A Spatial Interpolation Method for Flat Surface -

Estimation of the Surface Wind Speeds and Directions at Arbitrary Locations - A Spatial Interpolation Method for Flat Surface -

Observational Study of Wind Channeling within the St. Lawrence River Valley

Abstract The presence of orography can lead to thermally and dynamically induced mesoscale wind fields. The phenomenon of channeling refers to the tendency for the winds within a valley to blow more or less parallel to the valley axis for a variety of wind directions above ridge height. Channeling of surface winds has been observed in several regions of the world, including the upper Rhine Valley of Germany, the mountainous terrain near Basel, Switzerland, and the Tennessee and Hudson River Valleys in the United States. The St. Lawrence River valley (SLRV) is a primary topographic feature of eastern Canada, extending in a southwest–northeast direction from Lake Ontario, past Montreal (YUL) and Quebec City (YQB), and terminating in the Gulf of St. Lawrence. In this study the authors examine the long-term surface wind climatology of the SLRV and Lake Champlain Valley (LCV) as represented by hourly surface winds at Montreal, Quebec City, and Burlington, Vermont (BTV). Surface wind channeling is found to be prominent at all three locations with strong bidirectionalities that vary seasonally. To assess the importance of the various channeling mechanisms the authors compared the joint frequency distributions of surface wind directions versus 925-hPa geostrophic wind directions with those obtained from conceptual models. At YUL, downward momentum transport is important for geostrophic wind directions ranging from 240° to 340°. Pressure-driven channeling is the dominant mechanism producing northeasterly surface winds at YUL. These northeasterlies are most prominent in the winter, spring, and autumn seasons. At YQB, pressure-driven channeling is the dominant physical mechanism producing channeling of surface winds throughout all seasons. Of particular importance, both YUL and YQB exhibit countercurrents whereby the velocity component of the wind within the valley is opposite to the component above the valley. Forced channeling was found to be prominent at BTV, with evidence of diurnal thermal forcing during the summer season. Reasons for the predominance of pressure-driven channeling at YUL and YQB and forced channeling at BTV are discussed.

Comparisons of WRF/Chem simulations in Mexico City with ground-based RAMA measurements during the 2006-MILAGRO

Abstract. Simulations using the fully coupled WRF/Chem (Weather Research and Forecasting – Chemistry) model at 3-km resolution in Mexico City have been performed to examine the temperature, relative humidity, wind, and gaseous criteria pollutants (CO, O3, NO, NO2, and NOy) during the MCMA-2006/MILAGRO field campaign. Comparison of the model simulations with measurements from the ground-based air quality monitoring network (RAMA) is presented. The model resolves reasonably well the observed surface temperature, relative humidity and wind speed; however, large discrepancies are identified between the simulated and the observed surface wind direction for wind speeds below 2 m s−1. The simulated chemical species concentrations (CO, O3, NO, NO2, and NOy) compare favorably with the observations. Simulated O3 concentrations agree especially well with the observations. The simulated 10 VOC species compare generally favorably with the observations at the T0 supersite although lower correlation coefficients and larger biases exist for propene, acetone and propanal, isoprene, and c10-aromatics when compared to the other VOC species. The model performs much better during daytime than nighttime for both chemical species and meteorological variables, although the model tends to underestimate daytime temperature and relative humidity. Simulations using combinations of the available PBL schemes and land surface models (LSMs) do not show a preferred combination in reproducing the observations. The simulated meteorological fields under the O3-South, O3-North and EI Norte weather episodes exhibit similar correlation coefficients and biases for the same variable. However, the model performs well for the O3-South episode but inferiorly for the El Norte events in resolving the observed chemical species.

Model Representation of Local Air Quality Characteristics

Abstract Daily (24 h) and hourly air quality data at several sites are used to examine the performance of the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5)–Community Multiscale Air Quality Model (CMAQ) system over a 3-month period in 2003. A coarse (36 km) model grid was expected to provide relatively poor performance for ozone and comparatively better performance for fine particles, especially the more regional sulfate and carbonaceous aerosols. However, results were different from this expectation. Modeling showed significant skill for ozone at several locations but very little skill for particulate species. Modeling did poorly identifying surface wind directions associated with the highest and lowest pollutant exposures at most sites, although results varied widely by location. Model skill appeared to be better for ozone when spatial–temporal (S–T) patterns were examined, due in part to the ability of the model to reproduce much of the temporal variance associated with the diurnal photochemical cycle. At some sites the modeling even performed well in replicating the directional variability of hourly ozone despite relatively low spatial resolution. MM5–CMAQ spatial (directional) representation of 24-h-average particulate data was not good in most cases, but model skill improved somewhat when hourly data were examined. Modeling exhibited skill for sulfate at only one of nine sites using 24-h data averaged by daily resultant wind direction, at two of six sites when hourly data were averaged by direction, and at four of six sites when the combined spatial and temporal variance of sulfate was examined. Results were generally poorer for total carbon aerosol mass and total mass of particulate matter with diameter of less than 2.5 μm (PM2.5). The primary result of this study is that an S–T analysis of pollutant patterns reveals model performance insights that cannot be realized by only examining model error statistics as is typically done for regulatory applications. Use of this S–T analysis technique is recommended for better understanding model performance during longer simulation periods, especially when using grids of finer spatial resolution for applications supporting local air quality management studies. Of course, using this approach will require measuring semicontinuous fine particle data at more sites and for longer periods.