![]() ![]() ![]() Pollutants can be transported across cities, states, regions or even across the globe CMAQ simulates how winds move pollutants both vertically and horizontally in the atmosphere from local to global scales. This process, called four-dimensional data assimilation (see below), improves the accuracy of the weather model.Īir pollutants do not generally remain where they are emitted because of transport by the wind. In retrospective applications (looking at past events), which is how CMAQ is primarily used, weather observations and analyses can be used to “nudge” the model-predicted values toward reality. The equations simulate weather conditions, such as temperature, relative humidity and wind speed/direction. The equations are integrated forward in time using initial and boundary conditions, which are usually provided by a model at the global or regional scale. The approach used to inform CMAQ meteorological processes includes both explicit partial differential equations of mass and energy conservation, as well as parameterizations that reproduce the general impacts of extremely complex processes. Because meteorology is so critical for accurately predicting the build-up, transport, and removal of pollution, substantial effort is put into reproducing weather metrics reliably using state-of-science model evaluation methods. and time duration of interest from global to local scales. These equations are translated into computer code and applied on 3-D gridsover any domain domainThe area in space or time period over which a prediction is made. Meteorology modeling is based on equations for the dynamics and physics of the atmosphere. In this section you can read about the following: Wind, rain, temperature, clouds, sunshine, and humidity all impact chemistry in the air and near the ground. conditions strongly influence air quality. Weather can change from hour to hour, day to day, and season to season. ![]() Some familiar characteristics of the weather include wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation. Weather WeatherThe condition of the atmosphere at a particular place and time. Mixing and random movement of eddies result in a diffusion-like transport that is often orders of magnitude stronger than molecular diffusion.Ĭlouds, especially thunderstorms, transport surface-based emissions to higher altitudes where these chemicals can live longer and be transported around the globe by the stronger winds aloft.Ĭlouds produce rainfall, returning chemical compounds back to Earth's surface through wet deposition. The atmosphere is a generally turbulent environment, especially close to the Earth’s surface, which means it contains several eddies of different length and time scales affecting pollutant transport. When pollutants are emitted into the atmosphere from smoke stacks, tailpipes, fires, trees, dust storms, etc., they are transported by the wind (advection) and diffused by turbulence. Light can excite airborne molecules and turn them into other molecules. ![]()
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