Movie: Meteorological and Ozone Data for the Eastern US

Description:

A nine panel movie presenting meteorological and AIRS ozone data for selected time periods.
Top Left Panel: Three day back trajectories from 20 receptor sites evenly distributed over the Eastern US. The transport path of each receptor airmass is depicted by three trajectories. Each set of trajectories is distinguishedfrom each other by their color.
Middle Left Panel: Wind vector at 150, 900, and 2000 m above the ground level.
Lower Left Panel: Isopleths of precipitationdata
Top Middle Panel: Atmospheric flow simulation at the lowest 500 m of the atmosphere.
Middle Panel: A 24 hour moving average of the temperature at 150 m above the ground level.
Lower Middle Panel: The regional average daily maximum AIRS ozone concentrations (ppb) over a New England (NE), Atlantic (AT), South Central (SC), and Upper Midwest (UM) region.
Top Right Panel: Contoured AIRS ozone that has been linearly interpolated (morphed) between the 2:00 PM ozone concentrations
Middle Right Panel: The Raw AIRS ozone spatially interpolated between monitoring sites (contoured)
Lower Right Panel: The Raw AIRS ozone

Purpose:

These movies are designed to provide meteorological context for the qualitative interpretation and analysis of the AIRS ozone data, as well as other air quality data.

Method:

All meteorological data came from the National Meteorological Centers Nested Grid Model (NGM) with a grid resolution of ~180 km. All ozone data came from EPA's AIRS database. The method for which each panel was created is described below.

Back Trajectories: Calculated using the CAPITA Monte Carlo model by releasing three particles from each receptor site at two hour time increments and tracked backwards for three days.
Wind Vector: The wind vectors from the NGM data at approximately 150, 900, and 2000 m above the ground level for every other grid point (~360 m) in the meteorological grid. The length of each wind vector is proportional to its speed, while the arrow points in the direction of air flow.
Precipitation data: The precipitation as estimated by the NGM model.
Flow Simulation: The atmospheric flow simulation was created using the CAPITA Monte Carlo model. Particles were released from sources uniformly distributed over the Eastern US. Three particles were released from each source every two hours, and were tracked for seven days. Only the particles at the lowest 500 m of the atmosphere are displayed.
Temperature: The temperature data from the NGM model at the lowest layer, approximately 150 m above the ground level. At each time step the temperature was average from 11 hours before the time to 12 hours after, creating a 24 hour moving average.
Regionally Average Daily Maximum AIRS Ozone: For each day, the maximum ozone concentrations were averaged together for all location within the defined regions of New England (NE), Atlantic (AT), South Central (SC), and Upper Midwest (UM) (LINK to MAP of regions!!!).
Contoured AIRS Ozone: The raw AIRS ozone spatially interpolated between monitoring sites (contoured)
Morphed AIRS Ozone: Created by linearly interpolating (morphing) between the 2:00 PM contoured ozone concentrations.

Interpretation:

These movie provides meteorological information that can be used to begin to assess the roles of transport and kinetic processes influencing air quality. Atmospheric transport is directly represented by the back trajectories, flow simulation, and wind vectors. The temperature and morphed ozone provide indirect evidence of transport. The temperature and precipitation provide some information towards the kinetic processes influencing ozone concentrations. The means by which each panel can be used to access the transport and kinetics processes is further described below.

Back Trajectories: Indicate the pathway of airmasses prior to their impact upon the receptors. Their length and shape also identify whether the airmass is stagnating, recirculating (short curved trajectories), or part of a well defined flow (long straight trajectories) .
Wind Vector: Identify the direction and speed of the airflow at an instant in time. The varied directions and lengths of the wind vectors for a given location and time depict the degree of wind shear and veer in the atmosphere. It is the shear and veer which cause the regional scale dispersion and mixing of pollutants from distant sources.
Flow Simulation: The flow in the lowest 500 m of the atmosphere is visualized by the movement of tracer particles. The continuos release of particles from the uniformly distributed sources allows for the particle density to be used to identify regional scale features of the transport. The movement of a front is visualized by the low density of particles where the front has passed by, while stagnating and recirculating airmasses allow the particle to accumulate leading to high particle density.
Temperature: The 24 hour moving average removes the diurnal cycling of temperature which can obscure the spatial and temporal patterns of the temperature field. With the dirunal cycle removed, the averaged temperature indicated the direction of regional scale transport, since low temperatures in the Eastern US are often associated with Canadian airmasses, and high temperatures are associatedwith airmasses from the Gulf of Mexico and the deep South. The temperature is also often a good indication of the kinetic activity of an airmass. It has been shown that there is a strong relationship between the temperature and ozone concentrations.
Regionally Average Daily Maximum AIRS Ozone: For each day, the maximum ozone concentrations were averaged together for all location within the defined regions of New England (NE), Atlantic (AT), South Central (SC), and Upper Midwest (UM) (LINK to MAP of regions!!!).
Morphed AIRS Ozone: The morphed ozone removes the strong diurnal cycling seen in the raw ozone contours. With the diurnal cycle removed, the temporal and spatial development of high ozone airmasses can be better visualized.
Precipitation: Precipitation is a very efficient removal mechanism for aerosols and many gaseous pollutants such as ozone. Also, during precipitation events, clouds are present which can greatly reduce the solar radiation reaching the lower levels of the atmosphere inhibiting photochemistry. This combined affect can lead to low ozone concentrations.