A Study of the Freezing Cycle in an Alaskan Stream : A Completion Report

The work upon which this report is based was supported in part by funds (Proj. A-012-ALAS) provided by the United States Department of the Interior, Office of Water Resources Research, as authorized under the Water Resources Act of 1964, as amended

Remote sensing of global snowpack energy and mass balance: In-situ measurements on the snow of interior and Arctic Alaska

Observations led to a study of the physical properties of snow and the processes which operate on it. These observations included microwave brightness temperatures in interior Alaska which revealed: (1) up to three times more variability from one cell (1/2 degree latitude x 1/2 degree longitude) to the next in winter than in summer (5 to 15 K in winter and about 5 K in summer); (2) the overall range of temperature from week to week is about seven times greater in winter than in summer; (3) the microwave brightness temperature is about 25 K less than air temperature during summer but 35 to 60 K less during winter; and (4) the presence of snow cover appears to contribute to increasing the difference between air temperature and brightness temperature. The role of irregular substrate under the snow in enhancing convection has been studied with particular attention to variations in snow cover on water surfaces and in forested regions. LANDSAT imagery has been obtained to prepare a classification of ground surface types of the area. The extreme conditions of the 1988 to 1989 winter are discussed with respect to comparing the microwave data sets from 1985, and before, up to the present. The use of the Mt. Wrangell area as aerial photogrammetric controls for glacier measurements is given attention

Ice Fog: Low Temperature Air Pollution; Defined with Fairbanks, Alaska as type locality

Stable pressure systems over interior Alaska sometimes produce prolonged, extreme (below -40°C) cold spells at the surface. The meteorological conditions responsible for two such cold spells are discussed in detail in Appendix A, where it is shown that the rate of radiative cooling of the air is enhanced by suspended ice crystals which are themselves a result of the initial cooling. Radiation fogs formed during the onset of cold spells are generally of short duration because the air soon becomes desiccated. These fogs consist of supercooled water droplets until the air temperature goes below the "spontaneous freezing point” for water droplets (about -40°C); the fog then becomes an ice crystal fog, or simply "Ice Fog". During the cooling cycle water is gradually condensed out of the air until the droplets freeze. At this point there is a sharp, discontinuous decrease in the saturation vapor pressure of the air because it must be reckoned over ice rather than over water. The polluted air over Fairbanks allows droplets to begin freezing at the relatively high temperature of -35°C. Between -35 and -40°C the amount of water vapor condensed by freezing of supercooled water droplets is 3 to 5 times greater than the amount condensed by 1°C of cooling at these temperatures. This results in rapid and widespread formation of ice fog (Appendix B) which persists in the Fairbanks area as long as the cold spell lasts. The persistence of Fairbanks ice fog depends on a continual source of moisture (4.. 1 x 10^6 Kg H2O per day) from human activities within the fog. Ice fog crystals are an order of magnitude smaller than diamond dust, or cirrus cloud crystals, which in turn are an order of magnitude smaller than common snow crystals (0.01, 0.1 and 1 to 5-mm respectively). The differences in size are shown to result from differences in cooling rates over 5 orders of magnitude. Most of the ice fog crystals have settling rates which are slower than the upward velocity of air over the city center. The upward air movement is caused by convection cells driven by the 6°C "heat island" over Fairbanks. This causes a reduced precipitation rate which permits the density of ice fog in the city center to be three times greater than that in the outlying areas. The inversions which occur during cold spells over Fairbanks begin at ground level and are among the strongest and most persistent in the world. They are three times stronger than those in the inversion layer over Los Angeles. Thus, the low-lying air over Fairbanks stagnates and becomes effectively decoupled from the atmosphere above, permitting high concentrations of all pollutants. The combustion of fuel oil, gasoline, and coal provides daily inputs of: 4.1 x 10^6 kg CO2 ; 8.6 x 10^3 kg SO2 ; and 60, 46 and 20 kg of Pb, Br and Cl respectively, into a lens-like layer of air resting on the surface with a total volume less than 3 x 10^9 m^3. The air pollution over Fairbanks during cold spells couldn't be worse, because the mechanisms for cleaning the air are virtually eliminated while all activities which pollute the air are increased.This study was supported by Grants DA-ENG-11-190 61 G3, DA-ENG-27-021-62-G5 and DA-AMC-27-021-64-G8 from the Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, and by State of Alaska funds.Introduction : Acknowledgements -- Air Pollution : Types of air pollution ; Temperature Inversions ; Low Temperature Air Pollution -- Sources of Pollution, I Water : Combustion Products ; Cooling Water from Power Plants ; Miscellaneous Sources ; Summary of Man-made Water Sources for the Fairbanks Atmosphere -- Sources of Pollution, II Products Other Than Water : Electrical Conductance and Particulates ; Combustion Products ; Summary of Pollutants Other Than Water -- Economic Growth and Ice Fog -- General Physical Properties of Ice Fog : Optical Properties ; Cooling Rate of Exhaust Gases ; Development of a Typical Ice Fog -- Structure of the Polluted Air Layer : Volume ; Temperature Distribution and Convection in Fairbanks Air -- Mass Budget of Ice Fog : Ice Fog Precipitation Rates ; Density of Ice Fog ; Ice Fog Evaporation Rates ; Use of the Mass Budget Equation -- Air Pollution Aspects of Ice Fog : Air Pollution ; Remedial Action -- References Cited -- Appendices : Appendix A -- Appendix BYe

Glaciological Studies on Mount Wrangell, Alaska, 1961

Measurements of temperature,density, hardnesss and stratigraphic profiles were made in the upper 10 m of the snow cover in the caldera and an adjacent snow-filled crater. Facies parameters calculated for the summit area, 4000-4300 m at 62 degrees N, compare well with the same parameters near the dry-snow line on the Greenland ice sheet. This comparison is part of the purpose of the Mt Wrangell study within the framework of the "hypothetical North Polar Ice Sheet", based on a concept that the Greenland ice sheet behaves as though it belonged to a much larger ice sheet, which is symmetrical about the North Pole. The mean annual temperature, based on the measurements at 10 m depth in the caldera and inactive craters, is -20C. The mean annual value of accumulation in smooth central areas of the caldera is >100 cm water equivalent. Velocity of surface movement in the caldera averages about 5 cm/day or ~20 m/yr.Études glaciologiques sur le mont Wrangell, Alaska, 1961. En cinq points de la caldéra et du cratère voisin rempli de neige, on a mené des études sur la neige, au moyen de trous profonds de 3 à 4 m prolongés par des carottes jusqu'à 10 m. : les études ont porté sur la température, la densité, la dureté et les profils stratigraphiques de la neige. Les paramètres de faciès calculés pour le sommet du mont Wrangell (4,000 à 4,300 m., 62ºN.) se comparent très bien aux mêmes paramètres calculés près de la limite de la neige sèche sur la calotte groenlandaise. A 10 m. sous la surface au centre de la caldéra et au centre des cratères inactifs, la température moyenne annuelle est et – 20ºC. Près du bord de la caldéra, on a observé des effets de réchauffement volcanique. Au cours de l'été de 1961, l'accumulation nivale a été anormalement élevée. Elle varie de façon marquée selon le relief et sa valeur annuelle moyenne dépasse 100 cm en équivalent d'eau dans les parties centrales de la caldéra et des cratères. On a mesuré le mouvement de la surface par triangulation d'un réseau de pieux, à partir de points de contrôle situés à la bordure de la caldéra; dans la caldéra, la valeur moyenne était de 5 cm/jour ‾¹, soit environ 20 m/an‾¹

Pediatric heart transplantation: Improving results in high-risk patients

AbstractObjectives: Our institutional experience with 73 pediatric patients undergoing cardiac transplantation between January 1, 1990, and December 31, 1999, was reviewed to determine the impact of unconventional donor and recipient management protocols implemented to extend the availability of this therapy. Methods and results: The introduction of donor blood cardioplegic solution with added insulin was associated with a significant improvement in patient and graft survival (hazard ratio [Cox] = 0.25, P =.08), despite significantly longer ischemic times with this protocol compared with the use of crystalloid-based donor procurement techniques (P <.01). Eleven patients underwent intentional transplantation of ABO-incompatible donor hearts with the aid of a protocol of plasma exchange on bypass. In this subgroup, there were 2 early deaths caused by nonspecific graft failure (n = 1) and respiratory complications with mild vascular rejection (n = 1), and there was 1 late death caused by lymphoma. ABO-incompatible transplantation was not a risk factor for death by multivariate analysis. The postoperative course in these patients suggests minimal reactivity directed against incompatible grafts on the basis of low anti-donor blood group antibody production, in association with a favorable rejection profile. Ten of 13 patients requiring preoperative support with an extracorporeal membrane oxygenator survived transplantation; there were 3 additional late deaths in this subgroup (hazard ratio = 2.88, P =.05). Conclusions: The results with pediatric cardiac transplantation continue to improve as a result of changes in both surgical and medical protocols permitting successful treatment of patients conventionally considered at high risk or unsuitable for transplantation. (J Thorac Cardiovasc Surg 2001;121:782-91