Aerosol Transport in the California Central Valley Observed by Airborne Lidar. DeYoung, R. J.; Grant, W. B. & Severance, K..
Environmental Science & Technology:
http://dx.doi.org/10.1021/es048740l DOI: 10.1021/es048740l
An aerosol lidar system was deployed on the NASA DC-8 and used to measure aerosol vertical profiles in the California Central Valley. The nadir-pointing Nd:YAG lidar operated at 532 and 1064 nm at 20 Hz. The resulting aerosol profiles were plotted in a unique three-dimensional format that allowed the visual observation of the aerosol scattering ratio profiles, the valley topography, and corresponding backward trajectory air masses. The accumulation of aerosols from the Bakersfield area can be seen in the southern end of the valley due to topography and prevailing winds.
Air quality impacts of the October 2003 southern California wildfires. Phuleria, Harish; Fine, Philip M; Zhu, Yifang & Sioutas, Constantinos.
Journal of Geophysical Research:
In Southern California, dry summers followed by hot and dry westerly wind conditions contribute to the region's autumn fire season. In late October 2003, 13 large Southern California wildfires burned more than 750,000 acres of land, destroyed over 3500 structures, and displaced approximately 100,000 people. The fire episode was declared the deadliest and most devastating in more than a decade, and local media advised individuals to stay indoors to avoid exposure to excessive levels of PM, CO, VOCs, and ozone caused by the wildfires. This study examines the actual impact of these wildfires on air quality in urban Los Angeles (LA) using ''opportunistic'' data from other air pollution studies being conducted at the time of the fires. Measurements of pollutant gases (CO, NOx, and ozone), particulate matter (PM), particle number (PN) concentrations, and particle size distributions at several sampling locations in the LA basin before, during, and after the fire episode are presented. In general, the wildfires caused the greatest increases in PM10 levels (a factor of 3-4) and lesser increases in CO, NO, and PN (a factor of up to 2). NO2 levels remained essentially unchanged, and ozone concentrations dropped during the fire episode. Particle size distributions of air sampled downwind of the fires showed number modes at diameters between 100 and 200 nm, significantly larger than that of typical urban air. The particles in this size range were shown to effectively penetrate indoors, raising questions about the effectiveness of staying indoors to avoid exposure to wildfire emissions.
This report, an analysis of climate effects on agicultural systems, is a supplemental report to the main PIER-funded report that is an attachment to the Climate Action Team Report to the Governor and Legislature.
This report, an assessment of future CO2 and climate impacts on agriculture, is a supplemental report to the main PIER-funded report that is an attachment to the Climate Action Team Report to the Governor and Legislature.
This review summarizes many of the leading land use/land cover change models being used to predict urban/rural land use change, as well as those more specific to agricultural land use change. This assessment was conducted to examine model differences and assess which models may be most appropriate for use in Public Interest Energy Research (PIER) Climate Change studies. Models were identified through literature reviews, Internet searches, and consultation with sources at the University of California Agricultural Issues Center, Davis. Although numerous models were identified, this review focused only on those that are predictive and appropriate in spatial and temporal scale to the broader study. This report provides an overview of the models examined, a brief assessment for their usability in the PIER project, and a comparison chart of select factors of the models examined. Of the 39 leading land use/land cover change models examined, only 11 met the criteria established for use in the PIER climate change and ecosystems project. This report recommends that either the current or updated version (in development) of the University of California, Berkeley's California Urban and Biodiversity Analysis Model (CURBA) is the most appropriate model to use in the PIER Climate Change studies.
Asian continental aerosol persistence above the marine boundary layer over the eastern North Pacific: Continuous aerosol measurements from Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2). VanCuren, Richard A.; Cliff, Steven S.; Perry, Kevin D. & Jimenez-Cruz, Michael.
Journal of Geophysical Research:
We report analyses of aerosols collected for the 2002 Intercontinental Transport and Chemical Transformation experiment (ITCT-2K2). Sampling was conducted 15 April to 25 May 2002. Data are from three sites: a sea level site at Trinidad Head, California, a coastal mountain site 1 km altitude (Trinity Alps), and an inland mountain site near 2 km altitude (Mount Lassen). Aerosols were continuously collected in eight size bins (0.09 to 10 micrometers aerodynamic diameter) using eight-stage rotating drum impactors. Samples were analyzed in 3-hour time steps by synchrotron x-ray fluorescence. We find the following. (1) Aerosol chemical composition at Trinidad Head was generally dominated by marine aerosols with varying minor contributions from local sources. Despite the presence of Asian continental aerosol above the marine boundary layer, significant concentrations of Asian aerosols were observed at sea level only during a strong frontal passage between 22 and 25 April. (2) At the elevated sites, aerosol elemental composition was predominantly Asian despite wide swings in concentration. Analysis of soil-forming elements shows that Asian continental dust and associated combustion products overwhelmed local-source aerosols through the first half of the sampling period; in the latter half, Asian aerosols present in the free troposphere were regularly delivered to the mountain sampling sites by nocturnal subsidence. (3) Asian aerosols in the lower free troposphere, although highly variable, were very persistent, not arriving only in discrete 'transport events.' We conclude that throughout the experiment the aerosols in the lower free troposphere over the northeastern Pacific Ocean and western North America were dominated by continental outflow from Asia, with little marine or North American continental influence. Viewed in the context of previously published analyses of the long-term aerosol history for Mount Lassen that showed frequent, strong Asian influence throughout spring, summer, and fall, the Asian impact appears likely to be quasi-continuous for much of the year.
This study evaluated the hydrologic sensitivity of vernal pool ecosystems in the Central Valley of California to climatic changes projected for 2100. A vernal pool water- balance model was used to evaluate rain-fed vernal pools at four locations under future conditions projected by two contrasting global climate models. The potential for change in the duration of continuous inundation, frequency of reproductively suitable inundation events, and the seasonal distribution of inundation was quantified. The potential impact of hydrologic changes varied by species and by location. Three scales of response were identified: (a) At the regional scale, pools in the middle of the Central Valley near Merced were the most responsive to climatic changes. (b) At the local scale, smaller, shallower pools had the greatest potential to change the distribution of reproductively suitable habitat available to branchiopods. (c) At the individual pool scale, changes in precipitation will dominate changes in temperature, resulting in relatively linear responses in the duration of inundation. The ecological impact of these changes will be determined by a balance between the increasing suitability of vernal pools for branchiopod predators and the hydrologic improvement of currently marginal habitats.
Atmosphere-land cover feedbacks alter the response of surface temperature to CO2 forcing in the western United States. Diffenbaugh, Noah S..
http://dx.doi.org/10.1007/s00382-004-0503-0 DOI: 10.1007/s00382-004-0503-0
Soil CO2 flux was measured monthly over a year from tropical peatland of Sarawak, Malaysia using a closed-chamber technique. The soil CO2 flux ranged from 100 to 533 mg C m-2 h-1 for the forest ecosystem, 63 to 245 mg C m-2 h-1 for the sago and 46 to 335 mg C m-2 h-1 for the oil palm. Based on principal component analysis (PCA), the environmental variables over all sites could be classified into three components, namely, climate, soil moisture and soil bulk density, which accounted for 86% of the seasonal variability. A regression tree approach showed that CO2 flux in each ecosystem was related to different underlying environmental factors. They were relative humidity for forest, soil temperature at 5 cm for sago and water-filled pore space for oil palm. On an annual basis, the soil CO2 flux was highest in the forest ecosystem with an estimated production of 2.1 kg C m-2 yr-1 followed by oil palm at 1.5 kg C m-2 yr-1 and sago at 1.1 kg C m-2 yr-1. The different dominant controlling factors in CO2 flux among the studied ecosystems suggested that land use affected the exchange of CO2 between tropical peatland and the atmosphere.
Atmospheric aerosol light scattering and surface wetness influence the diurnal pattern of net ecosystem exchange in a semi-arid ponderosa pine plantation. Misson, Laurent; Lunden, Melissa; McKay, Megan & Goldstein, Allen H..
Agricultural and Forest Meteorology:
The diurnal variation of net ecosystem exchange (NEE) showed an unusual pattern at the Blodgett Forest Ameriflux site, with late afternoon NEE lower than early morning (indicating more uptake), while air temperature and atmospheric vapor pressure deficit were much higher. To investigate processes influencing this pattern, NEE was compared to several environmental variables during summer 2002. Unusual variations of NEE can be partly attributed to dew formation on the leaf surface. An empirical model is used to show that surface wetness reduced the net ecosystem uptake of CO2 during the morning by 11%. In addition, transport of air-pollution from the Central Valley to this site results in higher aerosol particle concentration, light extinction and light scattering during the afternoon than in the morning. Total irradiance was 11% lower during the afternoon than in the morning, while diffuse irradiance was 24% higher. The empirical model is used to show that the decrease in total radiation reduced photosynthesis during the afternoon, but the increase in diffuse radiation enhanced photosynthesis even more. Aerosol loading caused net uptake of CO2 by the forest to increase by 8% in the afternoon as a result of changes in direct and diffuse radiation.