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Climate Change/Air Quality Project

Impacts of Climate Change and Land Cover Change on Biogenic Volatile Organic Compounds (BVOCs) Emissions in Texas (RD83145201)


  1. To develop an integrated regional modeling system for climate change, biogenic emissions and air quality.

  2. To quantify the direct effect of climate change on biogenic emissions in Texas.

  3. To quantify the indirect effects of climate change on biogenic emissions in Texas.

  4. To investigate the impacts of human-induced land use/land cover change on biogenic emissions in Texas.

Purpose of the Study:

Significant amounts of vegetation and forests in eastern and central Texas are the source of substantial emissions of volatile organic compounds (VOCs), which, when mixed with nitrogen oxides (NOx) from anthropogenic sources (automobiles, electrical power generation, industrial boilers, incinerators and jet engines), can form tropospheric ozone - an air pollutant and a greenhouse gas. These biogenically-emitted VOCs (hereafter BVOCs) include isoprene (C5H8), monoterpenes (C10H16), and other reactive carbon compounds. Through their effects on atmospheric chemistry, aerosol concentrations, and the global carbon cycle, BVOC emissions can also potentially influence global climate.

The biogenic emissions depend on many factors, primarily the types of vegetation species, as well as the densities of these species. Isoprene is the most abundant of BVOCs, and is emitted by oak, sweetgum, eucalyptus, and aspen. Monoterpenes are the second most abundant of BVOCs, and are emitted by pine, cypress, spruce and fir. In addition, BVOC emissions vary with environmental conditions such as temperature, light (solar radiation), plant water stress, and ambient ozone and CO2 concentrations. At present, the response of BVOC emissions to climate change and land cover change is largely unknown.

We propose to address this issue by applying an integrated land-emission-climate modeling system (see below) to assess the effects of climate change and land cover change on BVOC emissions at the regional scale in Texas.


We hypothesize that climate change influences the emissions of biogenic volatile organic compounds (BVOCs) and hence air quality both directly and indirectly. The direct effect is that the changes in the surface incident solar radiation and air temperature, among other variables, affect the vegetation’s capability to release BVOCs.

The indirect effect is that the climate change will cause changes in the types of vegetation species as well as the prevalence of these species, thereby modulating the emission rates of BVOCs. In addition, human-driven land use change will also impact BVOC emissions.


The study area focuses on the State of Texas for three main reasons:

  1. The State has several urban areas that fail to meet the National Ambient Air Quality Standards for ozone, including the Houston/Galveston, Beaumont/Port Arthur and Dallas/Ft. Worth metropolitan areas.

  2. The elevated atmospheric ozone concentrations are not limited to the urban areas, but also extend throughout the eastern half of the State of Texas, including rural areas with high biogenic hydrocarbon emissions.

  3. Texas’ averaged state temperatures have varied substantially over the past century, with a warming trend since the late 1960s. This significant warming trend is projected to continue into the end of the 21st century.

We will integrate the Community Land Model (CLM3), which includes a dynamic general vegetation model (DGVM), with a biogenic emission module (BEIS/GLOBEIS) to explicitly estimate BVOC emissions. The CLM3 simulates, at every time step, the exchange of water, carbon, energy, and momentum between the land surface and atmosphere through a wide range of ground and canopy bio-geophysical processes which BVOC emissions depend on. A newly mapped land use dataset with a spatial resolution of 1 km and over 600 classifications for the state of Texas, together with human-driven land use change in urban areas (Houston/Galveston, Dallas/Ft. Worth, San Antonio, and Austin), will be used to estimate BVOC emissions. The DGVM will not only simulate the interactive vegetation processes (e.g., interaction between leaf growth and precipitation) but also include vegetation competition and distribution and dynamic disturbance (typically fire).

The CLM3-DGVM with the biogenic emission module will be linked first to the NCEP re-analysis data for an “off-line” sensitivity study and then to a regional climate model (WRF) for an investigation of system “feedbacks” and future climate sensitivities. Particular care will be taken to separate the effects of human-induced land use change.

Publications and Presentations:

(* denotes the student first author)

  • *Gulden, L.E. and Z.-L. Yang, 2006: Development of species-based, regional emission capacities for simulation of biogenic volatile organic compound emissions in land-surface models: An example from Texas, USA, Atmospheric Environment, 40(8), 1464-1479. [pdf]

  • *Gulden, L. E., Z.-L. Yang, and G.-Y. Niu, 2007: Interannual variation in biogenic emissions on a regional scale, J. Geophys. Res., 112 (D14), D14103, 10.1029/2006JD008231. [pdf]

  • *Gulden, L. E., Z.-L. Yang, and G.-Y. Niu, 2007: Sensitivity of biogenic emissions simulated by a land-surface model to uncertainty in representation of land-surface vegetation, Atmospheric Environment (submitted).

  • *Gulden, L.E., Z.-L. Yang, and G.-Y. Niu, 2005: Relative contribution of climate variability and vegetation phenology to biogenic emissions: Results from regional study in Texas, USA, poster presentation to American Geophysical Union 2005 Fall Meeting, San Francisco, CA, 5-9 December, 2005. [pdf]

  • *Gulden, L.E. and Z.-L. Yang, 2006: Incorporating plant-species variation in biogenic emission rates into regional weather and climate models, poster presented to the Eighth Conference on Atmospheric Chemistry, American Meteorological Society, Atlanta, Georgia, 29 January–2 February 2006. [pdf]

  • Jiang, X.-Y., and Z.-L. Yang, 2007: Improving Regional-scale Air Quality Modeling by the Better Representation of Land Use and Land Cover in a Coupled Atmosphere-Chemistry Model, poster presented to the NCAR WRF-CHEM Workshop, Boulder, Colorado, 20 June, 2007.

  • Lo, J. C. F., Z.-L. Yang, and R. Pielke Sr., 2007: Assessment of Dynamical Climate Downscaling Methodologies Using the Weather Research and Forecasting (WRF) Model, J. Geophys. Res. (submitted). [pdf]

  • *Song, J.H., L. E. Gulden, Z.-L. Yang, and D. T. Allen, 2006: The response of biogenic emissions to land-cover change and climate change, EPA Science Forum 2006 "Your Health, Your Environment, Your Future", Ronald Reagan Building and International Trade Center, Washington, DC.16-18 May, 2006. [pdf]

  • *Song, J.H., B. Parmenter, E.C. McDonald-Buller, and D.T. Allen, 2006: Impacts of urbanization on biogenic emissions and air pollutant deposition, JAWMA (submitted). [pdf]

  • Yang, Z.-L. and L.E. Gulden, 2006: Issues in the Simulated Biogenic Emissions at a Regional Scale, 2006 Western Pacific Geophysics Meeting, Beijing, China, 24-27 July 2006.

  • Yang, Z.-L., L.E. Gulden, and G.-Y. Niu, 2005: Sensitivity of biogenic emission estimates to uncertainties in land-cover datasets: An example from Texas, USA, oral presentation to American Geophysical Union 2005 Fall Meeting, San Francisco, CA, 5-9 December, 2005.

  • Yang, Z.-L., D. Allen, B. Parmenter, G.-Y. Niu, Y. Xu, and L. E Gulden, 2005: Plants, Climate, and Ozone: The future of Smog in Texas. Using climate models to investigate how climate change and land-cover change affect ground-level ozone, The University of Texas at Austin Climate Change Symposium, April 2005. [pdf]

Project Progress Reports: