The influence of bubble plumes on air-seawater gas transfer velocities

Air-sea gas exchange is an important process in the geochemical cycling of carbon dioxide (CO{sub 2}). The air-sea flux of CO{sub 2} is determined in part by the physical forcing functions, which are parameterized in terms of the air-sea transfer velocity, k{sub L}. Past studies have attempted to correlate k{sub L} with wind speed, U. Because strong winds occur in ocean regions thought to be important sources or sinks of CO{sub 2}, accurate knowledge of k{sub L} at high U is important in estimating the global air-sea flux of CO{sub 2}. Better understanding of the physical processes affecting gas transfer at large U will increase the accuracy in estimating k{sub L} in ocean regions with high CO{sub 2}, fluxes. Increased accuracy in estimating k{sub L} will increase the accuracy in calculating the net global air-sea CO{sub 2} flux and provide more accurate boundary and initial conditions for global ocean carbon cycle models. High wind speeds are associated with the presence of whitecaps, which can increase the gas flux by generating turbulence, disrupting surface films, and creating bubble plumes. Bubble plumes will create additional turbulence, prolong the surface disruption, and transfer gas to or from individual bubbles while they are beneath the surface. These turbulence and bubble processes very effectively promote gas transfer. Because of this, it is postulated that breaking waves, if present, will dominate non-whitecap related gas exchange. Under this assumption, k{sub L} Will increase linearly with increasing fractional area whitecap coverage, W{sub c}. In support of this, researchers found k{sub L} measured in a whitecap simulation tank (WSI) was linearly correlated with bubble plume coverage, B{sub c} (the laboratory analog of W{sub c}). However, it is not definitively known how the presence of breaking waves and bubble plumes affect the dependence of k{sub L} on Schmidt number, Sc, and aqueous-phase solubility, {alpha}

Water Surface Topography Measurements with the RSSG

<p>A new optical instrument for the measurement of surface wave slope and height properties was recently developed at the University of Heidelberg. The abilities of this <em>Reflective Stereo Slope Gauge</em> (RSSG) to measure the two-dimensional surface topography will be demonstrated. The RSSG overcomes the usual inaccuracies of stereo triangulation at specular surfaces by using properly positioned artificial light sources. The stereo images of a water surface patch with a size of about 1 m² are filled with specular reflections that are very similar to sun glitter. An algorithm was developed that precisely determines the water surface elevation for all specular reflections and interpolates over image areas without visible reflections to yield two-dimensional surface topography. Results from both a test on a pier near Lamont-Doherty Earth Observatory and the OSSPRE 2011 experiment on the Kilo Moana in the Pacific Ocean are presented to demonstrate the wide range of environmental conditions under which measurements are possible.</p

FACTORS INFLUENCING LEGISLATORS'USE OF POLICY INFORMATION AND IMPLICATIONS FOR PROMOTING GREATER USE

Despite a tremendous growth in the volume of policy analysis in the past decade, recent research indicates governmental decisionmakers make little direct use of such research; at best, policy-oriented research alters a decisionmaker's conceptualization of the policy problem over the long term. Previous efforts to explain policymakers'limited use of policy research have generally not considered the opportunities and constraints presented by specific decisionmaking contexts. To a large extent, the research utilization literature has focused on attitudinal and demographic characteristics of decisionmakers and has adopted as a central focus the "two-communities" theory which asserts that frequent, direct use of policy research by policymakers is unlikely because of the competing worldview and belief systems of policy researchers and policymakers. While the two-communities theory may partially explain the limited use of policy research, it ignores the institutional incentives motivating decisionmakers. More specifically, this earlier research does not consider the different motivations of policymakers and their relative impact on use of policy information. To expand the explanation of decisionmakers'use of policy information, I postulate a model of legislators'use of policy information that includes four types of factors that influence legislators'propensity to use policy information. These factors-worldview and attitude toward social science, perception of the way policy issues are considered in the legislature, perception of the legislative structure, and legislative orientations-combine two-communities type of independent variables and perceptions of the legislative environment. In this way, policymakers'use of policy information can be examined more realistically and comprehensively. Copyright 1987 by The Policy Studies Organization.