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You are here: Home / Air Quality / Air Modeling / Air Modeling Research and Contract Projects / Air Quality Research and Contract Reports: Photochemical Modeling

Air Quality Research and Contract Reports: Photochemical Modeling

Reports related to photochemical modeling of air quality written by contractors for the Texas Commission on Environmental Quality.

Reports from Air Quality Research and Contract Projects related to photochemical modeling are posted here as PDF files (Help with PDF) unless otherwise specified. Some reports have companion data files in various formats.

For comments and questions regarding these reports, please e-mail us at amda@tceq.texas.gov, put "Air Quality Photochemical Modeling Contract Report Inquiry" in the subject line, and include the web address of the report PDF file in the e-mail text or attache the original report PDF file.

Improving CAMx Plume-in-Grid Efficiency - Environ improved the physical and chemical evolution of large point source nitrogen oxides (NOx) plumes in the CAMx photochemical model that are too small to be resolved in the modeling grid. By using a Plume-in-Grid (PiG)-specific chemical mechanism limited to the inorganic chemical reactions in early NOx plumes, the computational efficiency was increased. Total CAMx run times were reduced 10-20% using the June 2006 episode. A bug fix corrected NOy conservation in the PiG mechanism, which artificially increased NOy by as much as 30% previously. Sensitivity tests showed the impact to be larger on course model grids, which is expected as PiG plumes dump to finer grids quickly. These improvements will be included in the next official release of CAMx version 6.1. (August 2013)

Foreign Contributions to Texas Ozone - This report, provided by Environ, documents the modeling project using GEOS-Chem global model to estimate the contribution of foreign anthropogenic sources to Texas ozone concentrations directly, and also to provide alternate boundary conditions from which TCEQ can conduct its own refined modeling to more accurately calculate the effects of foreign sources on Texas ozone. (August 2013)

Improving the CAMx photochemical model and support programs with a focus on the Dallas-Fort Worth area - This report, provided by Environ, provides details on improving the vertical mixing algorithms in the CAMx pre-processor WRFCAMx, the nocturnal plume growth rates in the Plume-in-Grid sub-model, and temperature and pressure dependencies for specific photolysis rates. Model tests were conducted using the June 2006 modeling episode. (August 2012)

Improving the Representation of Vertical Mixing Processes in CAMx - This report, provided by Environ, provides details on the vertical mixing updates to the CAMx pre-processor WRFCAMx. Various boundary layer schemes in the WRF meteorological model were analyzed and considered for implementation into the WRFCAMx interface program. CAMx model sensitivity to revised vertical diffusivity (Kv) inputs was conducted and analyzed. (August 2011)

Improving the Characterization of Pollution Transported into Texas - This report, provided by Harvard University, provides chemical boundary conditions for regional model simulations of U.S. air quality using the chemical transport model GEOS-Chem. The project calculated the chemical composition of the global atmosphere for two scenarios: (1) 2005-2006 meteorology with 2005-2006 emissions and (2) 2005-2006 meteorology with 2018 emissions. (April 2011)

Improving the Characterization of Pollution Transported into Texas Using OMI and TES Satellte and In Situ Data and HYSPLIT Back Trajectory Analyses - The Jet Propulsion Librartory (JPL) used ozone and NO2 measurements from the Tropospheric Emission Spectrometer (TES) and Ozone Monitoring Instrument (OMI) satellite-borne instruments together with in situ data and the Hybrid Single Particle Lagrangian Integrated Trajectory Model (Hy-SPLIT) to assess whether air parcels exhibiting enhanced ozone in the lower troposphere above Texas have moved within or outside of Texas. (April 2011)

Development, Evaluation and Testing of Version 6 of the Carbon Bond Chemical Mechanism (CB6) - This report, provided by Environ, documents the update of the carbon bond (CB) chemical mechanism for photochemical modeling applications from version CB05 to CB6. Compared to CB05, CB6 increases the number of chemical species from 51 to 77 and the number of reactions from 156 to 218. (September 2010)

Speed Improvements for EPS3 - This report, provided by Environ, documents the speed-up achieved with the latest Emissions Processing System v3 (EPS3). The entire process was examined for efficiency and various improvement techniques were implemented, with a significant speed-up of the oft-used merging and control tools. (July 2010)

Implementation of an Alternative Plume Rise Methodology in CAMx - This report, provided by Environ, documents a new plume rise algorithm for CAMx. The previous algorithm in CAMx did not allow the plume to release in more than one layer. Algorithms used in CMAQ and other air quality models were evaluated as possible replacements or options. Neither the existing schemes in CMAQ or CAMx was ideal in all conditions. Environ tested and ultimately chose this new algorithm for CAMx that eliminates discontinuities for various stability layer regimes and wind speeds. (June 2010)

Updated CAMx Boundary Conditions - This report, provided by Environ, documents the developement of new boundary conditions for the CAMx domain for the 2005 and 2006 Houston ozone episodes. The boundary conditions were extracted from CAMx runs on the RPO domain, which used boundary conditions from date-specific GEOS-Chem and date-specific MOZART. The GEOS-Chem results used in this study were specifically for 2005 and 2006 whereas previously monthly averaged 2002 results had been used. (July 2009)

Refining Hydrocarbon Oxidation Mechanisms via Isomeric Specific Radical Initiated Chemistry - This report, provided by Texas A&M University, documents the laboratory chemistry to perform measurements needed to improve the chemical mechanism used in the photochemical model CAMx itself. Dr. Simon North developed a new laboratory technique to measure the speed of radical oxidation of hydrocarbons (VOC). He then applied this technique to isoprene and measured individual rates of several reactions that are currently estimated in CAMx. In a future project, these individual reactions will be incorporated into CAMx. (December 2008)

CAMx Multiprocessing Capability for Computer Clusters Using the Message Passing Interface (MPI) Protocol - This report, provided by Environ, documents the implementation of MPI in CAMx. The MPI capablity in CAMx enables it to distribute a model application to multiple CPUs that share the computational load in integrating the model solution. (August 2008)

Higher-Order Decoupled Direct Method (HDDM) for Ozone Modeling Sensitivity Analyses and Code Refinements - This report, provided by Environ (Bonyoung Koo and Greg Yarwood) and Rice University (Dan Cohan), presents the results of their work on the HDDM method. Koo and Yarwood added refinements to the HDDM code in CAMx to help it run faster and more accurately, and Cohan performed an HDDM analysis on the June 2005 ozone episode. Cohan found that the ozone concentrations are very sensitive to photolysis, indicating a strong dependence on the placement of clouds. He also found that the sensitivity of ozone to VOC or NOx emission controls depends on weather. Two episode days showed strong NOx dependence, but one day showed strong VOC dependence in central Houston and strong NOx dependence further from the urban core. (August 2008)

Boundary Conditions and Fire Emissions Modeling - This report, provided by Environ, describes in detail two related projects. First is the development of emissions inventories of biomass burning for the continental United States plus large portions of Canada and Mexico. Day-specific inventories for the 2005 and 2006 ozone seasons were developed using satellite-derived fire estimates, and a "typical" fire inventory was developed from inventories previously prepared by CenRAP. The Contractor also developed software to process the emissions and allocate emissions from major fires to elevated model layers. In the second part of this work, the Contractor used output from two global atmospheric models, MOZART and GEOS-Chem, to build boundary concentration files for the CENRAP continental scale modeling domain. The Contractor then ran the continental-scale model (incorporating the aforementioned fire emissions inventory) to create both base year and future year boundary conditions files for the TCEQ Eastern United States (EUS) modeling domain. The report includes performance evaluation of the resulting boundary conditions and recommendations on their use, along with recommendations for future work. (September 2008)

Lagrangian Modeling of Industrial Point-source Plumes in the Houston-Galveston Area - This report, provided by Noor Gillani and Yuling Wu of the University of Alabama at Huntsville, describes Lagrangian reactive plume modeling performed for the Harris-Galveston-Brazoria county area for August 28, 2000. The purpose of this modeling was to simulate the observed ozone and ozone precursors with a different type of model (other than a photochemical grid model which TCEQ uses in its regulatory ozone modeling). The report describes the modeling in detail, including the TexAQS 2000 data used to initialize the model's meteorological parameters. The report also provides an inferred point source emissions inventory for the industrial facilities in the greater Houston area. (March 2003)

Meteorological and Ozone Characteristics in the Houston Area from August 23 through September 1, 2000 - This report, from Sonoma Technology, Inc., provides a day-specific conceptual models of ozone formation in the Houston-Galveston-Brazoria area for each day of the Texas Air Quality Study. Each of these daily conceptual models provides a holistic picture of the processes leading to ozone formation (or lack thereof) throughout that day. Overall model performance for any day can then be assessed through comparing the modeled processes with the processes in that day's conceptual model. (August 2002)

Sensitivity Analyses of the September 8-11, 1993 Ozone Episode: Reports (1, 2, 3, 4) and Memo - Environ has prepared four reports and a technical memo describing a number of modeling analyses conducted for the September 8-11, 1993 episode. Environ first evaluated the use of Version 3 of CAMx, along with flexi-nesting and chlorine chemistry. Using these model enhancements, they then conducted sensitivity analyses to evaluate model performance under several hypothesized industrial VOC adjustments. Finally, future-case modeling was performed to assess the feasibility of trading the last 10% of industrial NOx reductions for VOC reductions. These analyses were conducted using the original SAIMM meteorology, and with MM5 and RAMS-generated meteorological inputs. The reports and memo are in PDF format. (May 2002)

An Investigation of CAMx Modeling Issues with Sensitivity Simulations for the September 6-11, 1993 Ozone Episode for Houston-Galveston Area - This report, from Sonoma Technology Inc., provides details on a project to isolate the causes of an area of ozone over prediction in the original modeling, assess the impact of cloud cover on CAMx ozone predictions, and determine if rapid ozone production events can be simulated with CAMx through a series of 12 sensitivity simulations. (August 2001)

Preliminary RAMS/CAMx Ozone Model Performance Results for the Houston Area and the September 6-11, 1993 COAST Episode - This memorandum, provided by Environ, describes the CAMx modeling performance evaluation done with the RAMS-based meteorological fields for the September 6-1,1 1993 Houston ozone episode. EPA performance criteria, including unpaired peak, bias, gross error, and time series are discussed. (January 2001)

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