Publications Published in 1993

1. An Analysis of Sierra Nevada Winter Orographic Storms: Ground-based Ice-Crystal Observations. Demoz, Belay B.; Zhang, Renyi; Pitter, Richard L..
   Journal of Applied Meteorology: 1993
   Notes
   Systematic observations of the sizes, shapes, and degrees of riming of ice particles falling at a downwind station of a major mountain barrier are presented. The observational station was equipped to measure ice-particle masses from 1microg to a few milligrams and to measure ice-particle dimensions, habits, degrees of riming, and degrees of aggregation. The results are shown to be useful in learning where ice nucleation and growth take place in the cloud system. The present study analyzed dissipating and developing winter orographic storm systems, which are representative of more than 60% of the storms observed over the study region. It suggests that most of the needles and columns observed at the ground may be formed by secondary ice production. Heavy riming was associated with light precipitation, while high precipitation rates were correlated with a high number fraction of aggregate crystals. Aggregation was found to be important in the process of precipitation development and the aggregate mass was mostly contained in the dendritic crystal growth region.
   
   
   
2. Can Large-Scale Climatic Models Be Linked with Multiscale Ecological Studies?. Root, Terry L.; Schneider, Stephen H..
   Conservation Biology: 1993
   Notes
   On a global scale, climatic changes driven by human activities are typically projected to increase from 1°C to 5°C per 100 years, a rate of change that is an order of magnitude greater than that typically experienced naturally. Such a potentially dramatic change in climate could easliy cause dramati biological responses, including extinction. Species show a wide range of responses to climate, and consequently the response of different species of plants and animals to climatic change will be quite variable. This implies a likelihood for a disassembling of natural communities and for transient, nonequilibrium restructuring of habitats as climatic change unfolds. Validated models that help forecast these events are needed to aid scientists in better understanding the ecological ramifications of global climatic change. Also, and perhaps more important for conservation biology, such validated models can help provide probabilities for the occurrence of these events, which will allow policy makers to make better, informed decisions. Typically, the study plots of most ecological field work are tennis-court-sized, while the smalles resolved scales in global climatic models are about 500 X 500 km. Computer limitations preclude significant reduction in scales of climatic models.
   
   
   
3. Evolution of the large-scale temperature field in the greenland sea during 1988-89 from tomographic measurements. Worcester, P. F.; Lynch, J. F.; Morawitz, W. M. L.; Pawlowicz, R.; Sutton, P. J.; Cornuelle, B. D.; Johannessen, O. M.; Munk, W. H.; Owens, W. B.; Shuchman, R.; Spindel, R. C..
   Geophysical Research Letters: 1993
   Notes
   The Greenland Sea Ocean Acoustic Tomography Experiment was conducted during 1988-89, as one component of the international Greenland Sea Project, to study deep water formation and the response of the gyre to variations in wind stress and ice cover. Six acoustic transceivers moored in an array 200-km across transmitted to one another at four hour intervals. Near the end of February, 1989, a sub-surface temperature maximum at several hundred meters depth disappeared over a suprisingly large area of the central Greenland Sea . While the water column was modified to about 1000 m depth over much of the gyre, the surface remained colder than the deeper water, contrary to what might be expected from simple models of convective renewal.
   
   
   
4. Fire history and climate change in giant sequoia groves. Swetnam, T. W..
   Science: 1993
   Notes
   Fire scars in giant sequoia [Sequoiadendron giganteum (Lindley) Buchholz] were used to reconstruct the spatial and temporal pattern of surface fires that burned episodically through five groves during the past 2000 years. Comparisons with independent dendroclimatic reconstructions indicate that regionally synchronous fire occurrence was inversely related to yearly fluctuations in precipitation and directly related to decadal-to-centennial variations in temperature. Frequent small fires occurred during a warm period from about A. D. 1 000 to 1300, and less frequent but more widespread fires occurred during cooler periods from about A.D. 500 to 1000 and after A.D. 1300. Regionally synchronous fire histories demonstrate the importance of climate in maintaining nonequilibrium conditions.
   
   
   
5. Landfill CH4: Rates, Fates, and role in global carbon cycle. Bogner, J; Spokas, K.
   Chemosphere Global Change Science: 1993
   Notes
   Published estimates for worldwide landfill methane emissions range from 9 to 70 Tg yr−1. Field and laboratory studies suggest that maximum methane yields from landfilled refuse are about 0.06 to 0.09 m3 (dry kg)−1 refuse, depending on moisture content and other variables, such as organic loading, buffering capacity, and nutrients in landfill microenvironments. Methane yields may vary by more than an order of magnitude within a given site. Fates for landfill methane include (1) direct or delayed emission to the atmosphere through landfill cover materials or surface soils; (2) oxidation by methanotrophs in cover soils, with resulting emission of carbon dioxide; or (3) recovery of methane followed by combustion to produce carbon dioxide. The percent methane assigned to each pathway will vary among field sites and, for individual sites, through time. Nevertheless, a general framework for a landfill methane balance can be developed by consideration of landfill age, engineering and management practices, cover soil characteristics, and water balance. Direct measurements of landfill methane emissions are sparse, with rates between 10−6 and 10−8 g cm−2 s−1; very high rates of 400 kg m−2 yr−1 have been measured at a semiarid unvegetated site. The proportion of landfill carbon that is ultimately converted to methane and carbon dioxide is problematical; the literature suggests that, at best, 25% to 40% of refuse carbon can be converted to biogas carbon. Cellulose contributes the major portion of the methane potential. Routine excavation of nondecomposed cellulosic materials after one or two decades of landfill burial suggests that uniformly high conversion rates are rarely attained at field sites. For a longer-term viewpoint, considering archaeologic and geologic preservation of organic carbon through anaerobic burial, one can speculate that widespread landfilling practices in developed and developing countries may be providing a measurable sink for organic carbon, as well as increasing the atmospheric methane burden.
   
   
   
6. Nitrous Oxide emissions from motor vehicles in tunnels and their global extrapolation. Berges, M G M; Hofmann, R M; Scharffe, D; Crutzen, P J.
   Journal of Geophysical Research Atmospheres: 1993
   Notes
   The finding that catalytic converters enhance the N2O emissions from motor vehicles give rise to the concern that they may represent a significant source of N2O. Measurements of N2O and CO2 emissions of a fleet of about 40,000 cars were conducted in two roadway tunnels in Stockholm, Sweden, and Hamburg, Germany, to estimate N2O emissions under normal driving conditions. To avoid any risk of artifact N2O formation, samples were analyzed within 1 min after collection. Median N2O to CO2 molar emission ratios of 1.4×10−4 and 0.6×10−4 were measured in Stockholm and Hamburg, respectively. The lower emission ratio in Hamburg may well reflect the smaller fraction of catalyst-equipped cars in Germany (22%) compared to the Swedish vehicle fleet (33%) as well as low N2O emissions from trucks which were not allowed in the Stockholm tunnel. From our measurements we derive a N2O to CO2 molar emission ratio from cars equipped with catalysts in the median to interquartile range of 3.8±2.2×10−4, from which present worldwide N2O emissions from cars are estimated to be 0.38±0.22 Tg N2O (0.24±0.14 Tg N) per year, corresponding to 3–16% of the atmospheric growth of 4.7±0.9 Tg N2O/yr (3.0±0.6 Tg N/yr). From the worldwide emission of 0.38 Tg N2O we derived an emission of about 170 mg N2O/km for catalyst-equipped cars, significantly higher than those reported in earlier studies. If the entire present fleet of cars were to be equipped with current types of catalysts, the global N2O emission could double and reach 6–32% of the atmospheric growth rate. © American Geophysical Union 1993
   
   
   
7. The Jepson Manual: Higher Plants of California. Hickman, J. C..
   University of California Press: 1993
   
   
8. Variations in northern sierra nevada streamflow - implications of climate change. Pupacko, A..
   Water Resources Bulletin: 1993
   Notes
   Historical records of streamflow for an eastward- and a westward-draining stream in the northern Sierra Nevada have been analyzed for evidence of changes in runoff characteristics and patterns of variability. A trend of increasing and more variable winter streamflow began in the mid-1960s. Mean monthly streamflow during December through March was substantially greater for water years 1965-1990 compared to water years 1939-1964. Increased winter and early-spring streamflow during the later period is attributed to small increases in temperature, which increase the rain-to-snow ratio at lower altitudes and cause the snowpack to melt earlier in the season at higher altitudes. The timing of snowmelt runoff on the western slope of the Sierra Nevada is more sensitive than it is on the eastern slope to changes in temperature, owing to predominantly lower altitudes on the west side.