Roland R. Draxler

NOAA’s HYSPLIT Atmospheric Transport and Dispersion Modeling System

AbstractThe Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), developed by NOAA’s Air Resources Laboratory, is one of the most widely used models for atmospheric trajectory and dispersion calculations. We present the model’s historical evolution over the last 30 years from simple hand-drawn back trajectories to very sophisticated computations of transport, mixing, chemical transformation, and deposition of pollutants and hazardous materials. We highlight recent applications of the HYSPLIT modeling system, including the simulation of atmospheric tracer release experiments, radionuclides, smoke originated from wild fires, volcanic ash, mercury, and wind-blown dust.

Determination of the contribution of northern Africa dust source areas to PM10 concentrations over the central Iberian Peninsula using the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) model

[1]xa0A source apportionment methodology has been implemented to estimate the contribution from different arid geographical areas to the levels of measured atmospheric particulate matter with diameters less than 10 μm (PM10). Toward that end, the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) has been used to quantify the proportions of mineral dust originated from specific geographical areas in northern Africa. HYSPLIT simulates the transport, dispersion, and deposition of dust plumes as they travel from the source areas to the receptors. This model has been configured to reproduce high daily ambient PM10 levels recorded at three Spanish EMEP (Cooperative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air pollutants in Europe) regional background monitoring stations, located over the central Iberian Peninsula, during a North African dust outbreak from 12 to 15 March 2003. Different model setups have been utilized to determine the best suite of parameters needed to better represent the observed concentrations. Once the simulation has been configured, the model has been run for individual scenarios which include eight specific source areas over northern Africa considered as possible contributors to the PM10 levels measured at the monitoring stations. One additional run has been carried out to account for the rest of the dust sources in northern Africa. Furthermore, the fractional contribution to the PM10 air concentrations at the receptors from each run has been used to estimate the source apportionment. According to these calculations, the contribution from each area to the PM10 recorded over central Iberia for the March 2003 episode can be detailed as follows: 20–30% of the PM10 dust originated in Mauritania and the western Sahara, 15–20% from Mali, Mauritania and the western flanks of the Ahaggar Mountains, and 55–60% from other northwestern African sources within the rest of the desert source area.

World Meteorological Organization's model simulations of the radionuclide dispersion and deposition from the Fukushima Daiichi nuclear power plant accident☆

Five different atmospheric transport and dispersion models (ATDM) deposition and air concentration results for atmospheric releases from the Fukushima Daiichi nuclear power plant accident were evaluated over Japan using regional (137)Cs deposition measurements and (137)Cs and (131)I air concentration time series at one location about 110xa0km from the plant. Some of the ATDMs used the same and others different meteorological data consistent with their normal operating practices. There were four global meteorological analyses data sets available and two regional high-resolution analyses. Not all of the ATDMs were able to use all of the meteorological data combinations. The ATDMs were configured identically as much as possible with respect to the release duration, release height, concentration grid size, and averaging time. However, each ATDM retained its unique treatment of the vertical velocity field and the wet and dry deposition, one of the largest uncertainties in these calculations. There were 18 ATDM-meteorology combinations available for evaluation. The deposition results showed that even when using the same meteorological analysis, each ATDM can produce quite different deposition patterns. The better calculations in terms of both deposition and air concentration were associated with the smoother ATDM deposition patterns. The best model with respect to the deposition was not always the best model with respect to air concentrations. The use of high-resolution mesoscale analyses improved ATDM performance; however, high-resolution precipitation analyses did not improve ATDM predictions. Although some ATDMs could be identified as better performers for either deposition or air concentration calculations, overall, the ensemble mean of a subset of better performing members provided more consistent results for both types of calculations.

Across North America tracer experiment (ANATEX): Sampling and analysis

Abstract Between 5 January 1987 and 29 March 1987, there were 33 releases of different tracers from each of two sites: Glasgow, MT and St. Cloud, MN. The perfluorocarbon tracers were routinely released in a 3-h period every 2.5 days, alternating between daytime and night-time tracer releases. Ground-level air samples of 24-h duration were taken at 77 sites mostly located near rawinsonde stations east of 105°W and between 26°N and 55°N. Weekly air samples were taken at 12 remote sites between San Diego, CA and Pt. Barrow, AK and between Norway and the Canary Islands. Short-term 6-h samples were collected at ground level and 200 m AGL along an arc of five towers between Tulsa, OK and Green Bay, WI. Aircraft sampling within several hundred kilometers of both tracer release sites was used to establish the initial tracer path. Experimental design required improved sampler performance, new tracers with lower atmospheric backgrounds, and improvements in analytic precision. The advances to the perfluorocarbon tracer system are discussed in detail. Results from the tracer sampling showed that the average and peak concentrations measured over the daily ground-level sampling network were consistent with what would be calculated using mass conservative approaches. however, ground-level samples from individual tracer patterns showed considerable complexity due to vertical stability or the interaction of the tracer plumes with low pressure and frontal systems. These systems could pass right through the tracer plume without appreciable effect. Aircraft tracer measurements are used to confirm the initial tracer trajectory when the narrow plume may miss the coarser spaced ground-level sampling network. Tower tracer measurements showed a more complex temporal structure than evident from the longer duration ground-level sampling sites. Few above background plume measurements were evident in the more distant remote sampling network due to larger than expected uncertainties in the ambient background concentrations.

Input Data Requirements for Lagrangian Trajectory Models

In October 2011 an American Geophysical Union Chapman Conference was held in Grindelwald, Switzerland, titled “Advances in Lagrangian Modeling of the Atmosphere.” Lagrangian models are being applied to a wide range of high-impact atmospheric phenomena, such as the transport of volcanic ash and dispersion of radioactive releases. One common theme that arose during the meeting is the need for improved access to the output products of forecast models and reanalysis systems, which are used as in-puts to trajectory and dispersion models. The steady increases in horizontal and vertical resolution in forecast models and data assimilation systems have not been accompanied by changes in model output products, such as higher-frequency winds and the provision of important auxiliary parameters (e.g., heating rates and subgrid-scale mixing properties). This paper discusses the principles of Lagrangian kinematic models and recommends changes in model output practices that would lead directly to significant improvements...

Incorporation of detailed chemistry into a three-dimensional Lagrangian–Eulerian hybrid model: application to regional tropospheric ozone

Abstract During the last 20 years a variety of models have been developed to study the transport, transformation and deposition of pollutants on the regional scale. Different levels of complexity have been considered to depict these phenomena. The representation of the chemical transformations has been one of the most challenging tasks. A detailed non-linear Eulerian chemistry module (CheM) has here been added to the hybrid single-particle Lagrangian integrated trajectory (HY-SPLIT) model. The model is applied to analyze changes in hourly averaged ozone concentration over the period of 8–12 July 1996. Comparisons between simulation results and measurements from 11 monitoring stations throughout Pennsylvania show that hybrid Lagrangian–Eulerian modeling techniques are promising and may be useful for predicting air quality variables in general.

Estimating vertical diffusion from routine meteorological tower measurements

Abstract Data from an instrumented meteorological tower are used to calculate vertical dispersion coefficients and vertical diffusivities using surface layer concepts. The tower instrumentation is similar to that at many power plant sites and only a temperature gradient and wind speed are required for the calculations. The calculated vertical turbulence compares well with bivane data collected on the tower. Calculations of vertical dispersion also compare well with dispersion data collected at other sites.

Sensitivity of the modelled deposition of Caesium-137 from the Fukushima Dai-ichi nuclear power plant to the wet deposition parameterisation in NAME

This paper describes an investigation into the impact of different meteorological data sets and different wet scavenging coefficients on the model predictions of radionuclide deposits following the accident at the Fukushima Dai-ichi nuclear power plant in March 2011. Three separate operational meteorological data sets, the UK Met Office global meteorology, the ECMWF global meteorology and the Japan Meteorological Agency (JMA) mesoscale meteorology as well as radar rainfall analyses from JMA were all used as inputs to the UK Met Offices dispersion model NAME (the Numerical Atmospheric-dispersion Modelling Environment). The model predictions of Caesium-137 deposits based on these meteorological models all showed good agreement with observations of deposits made in eastern Japan with correlation coefficients ranging from 0.44 to 0.80. Unexpectedly the NAME run using radar rainfall data had a lower correlation coefficient (Rxa0=xa00.66), when compared to observations, than the run using the JMA mesoscale model rainfall (Rxa0=xa00.76) or the run using ECMWF met data (Rxa0=xa00.80). Additionally the impact of modifying the wet scavenging coefficients used in the parameterisation of wet deposition was investigated. The results showed that modifying the scavenging parameters had a similar impact to modifying the driving meteorology on the rank calculated from comparing the modelled and observed deposition.

Meteorological Factors of Ozone Predictability at Houston, Texas

ABSTRACT Several ozone modeling approaches were investigated to determine if uncertainties in the meteorological data would be sufficiently large to limit the application of physically realistic ozone (O3) forecast models. Three diagnostic schemes were evaluated for the period of May through September 1997 for Houston, TX. Correlations between measured daily maximum and model calculated O3 air concentrations were found to be 0.70 using a linear regression model, 0.65 using a non-advective box model, and 0.49 using a three-dimensional (3-D) transport and dispersion model. Although the regression model had the highest correlation, it showed substantial underestimates of the highest concentrations. The box model results were the most similar to the regression model and did not show as much underestimation. The more complex 3-D modeling approach yielded the worst results, likely resulting from O3 maxima that were driven by local factors rather than by the transport of pollutants from outside of the Houston domain. The highest O3 concentrations at Houston were associated with light winds and meandering trajectories. A comparison of the gridded meteorological data used by the 3-D model to the observations showed that the wind direction and speed values at Houston differed most on those days on which the O3 underestima-tions were the greatest. These periods also tended to correspond with poor precipitation and temperature estimates. It is concluded that better results are not just obtained through additional modeling complexity, but there needs to be a comparable increase in the accuracy of the meteorological data.

Long-range travel of airborne material subjected to dry deposition

Abstract A finite difference model has been adapted to simulate the effect on plume depletion of dry depositon and diurnal stability variations. Tests were conducted out to ten days travel time for various deposition velocities. Residence times were twice those obtained by the traditional deposition model suggested by Chamberlain. A diurnal stability cycle changed the residence time for low level releases from 1 5 (nighttime release) to 3 (daytime release) times that obtained in those tests with constant neutral stability. The stability at the time of release was one of the primary factors that determined the mass remaining airborne, even at several days travel time.