Lidar observations and modeling of cold air outbreaks during MASEX and GALE

As part of MASEX and GALE a number of research flights were carried out over the Marine Boundary Layer (MBL) during periods when extremely cold and dry continental air was flowing out over the warm coastal waters at the east coast of the U.S. Such periods, which are named cold air outbreaks are characterized by massive warming and moistening of the MBL resulting in rapid entrainment conditions. As the MBL deepens as a function of fetch over the ocean, clouds develop. The line of cloud formation typically follows the coast line closely as has been observed many times from satellite imagery. The backscatter data from the NASA Goddard airborne lidar, which was used to measure the depth of the MBL in great detail, is ideally suited to verify parametrized models of boundary layer growth rate. The data indicates that the deepening MBL gradually develops clouds at its top. Those clouds form an integral part of the MBL and exercise an important influence on the energy cycle within the MBL. It is suggested that the rapid entrainment observed during overcast conditions represent an increase in efficiency of conversion of available turbulence kinetic energy into entrainment energy

Convective structure of the planetary boundary layer of the ocean during gale

The structure of the Planetary Boundary Layer (PBL) was measured, using an airborne lidar, over the Atlantic Ocean during several intensive observation periods of the Genesis of Atlantic Lows Experiment (GALE). Primary emphasis is on the understanding of the convective structure within the PBL during cold air outbreaks. Cold outbreaks generally occur in between the development of coastal storms; and behind a cold front sweeping down from Canada out across the Atlantic. As the cold dry air moves over the relatively warm ocean, it is heated and moistened. The transfer of latent and sensible heat during these events accounts for most of the heat transfer between the ocean and atmosphere during winter. Moistening of the PBL during these eventsis believed to be an important factor in determining the strength of development of the storm system which follows. In general, the more PBL moisture available as latent heat the higher the probability the storm will intensify. The major mechanism for vertical mixing of heat and mositure within the PBL is cellular convection. Knowlede of the organization and structure of the convection is important for understanding the process

When does assonance make L2 lexical phrases memorable?

Among the challenges that second language learners face is that of acquiring a large num-ber of lexical phrases such as collocations and idiomatic expressions (e.g. Pawley & Syder, 1983; Willis, 1990; Nattinger & DeCarrico, 1992; Lewis, 1993). There is evidence that post-childhood learners master this dimension of L2 vocabulary very slowly (e.g. Li & Schmitt, 2010; Laufer & Waldman, 2011). In recent years, researchers have tested diverse proposals about how learners can be helped to acquire L2 phrases (see Boers & Lind-stromberg, 2012). The factor we explore in the present article, however, is a phonological feature that may make word combinations relatively noticeable and easy to acquire, namely, assonance

A cloudiness transition in a marine boundary layer

Boundary layer cloudiness plays several important roles in the energy budget of the earth. Low level stratocumulus are highly reflective clouds which reduce the net incoming shortwave radiation at the earth's surface. Climatically, the transition to a small area fraction of scattered cumulus clouds occurs as the air flows over warmer water. Although these clouds reflect less sunlight, they still play an important role in the boundary layer equilibrium by transporting water vapor upwards, and enhancing the surface evaporation. The First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) included a marine stratocumulus experiment off the southern California coast from June 29 to July 19, 1987. The objectives of this experiment were to study the controls on fractional cloudiness, and to assess the role of cloud-top entrainment instability (CTEI) and mesoscale structure in determining cloud type. The focus is one research day, July 7, 1987, when coordinated aircraft missions were flown by four research aircraft, centered on a LANDSAT scene at 1830 UTC. The remarkable feature of this LANDSAT scene is the transition from a clear sky in the west through broken cumulus to solid stratocumulus in the east. The dynamic and thermodynamic structure of this transition in cloudiness is analyzed using data from the NCAR Electra. By averaging the aircraft data, the internal structure of the different cloud regimes is documented, and it is shown that the transition between broken cumulus and stratocumulus is associated with a change in structure with respect to the CTEI condition. However, this results not from sea surface temperature changes, but mostly from a transition in the air above the inversion, and the breakup appears to be at a structure on the unstable side of the wet virtual adiabat

Cloud top entrainment instability and cloud top distributions

Classical cloud-top entrainment instability condition formulation is discussed. A saturation point diagram is used to investigate the details of mixing in cases where the cloud-top entrainment instability criterion is satisfied

Almost optimal adaptive LQ control: observed state case

In this paper we propose an almost optimal indirect adaptive controller for input/state dynamical systems. The control part of the adaptive scheme is based on a modified LQ control law: by adding a time varying gain to the certainty equivalent control law we avoid the conflict between identification and contro

Exploring the Impact of the EU’s Promotion of Regional and Inter-regional Processes in the Black Sea Region through Science Diplomacy. EL-CSID Working paper Issue 2017/7 • September 2017

Building on the analytical tools defined by Kingah, Amaya & Van Langenhove (2016) in the EL-CSID Working Paper 1, this paper assesses the willingness, capacity and acceptance of EU SD policies in the Black Sea Region (BSR). This qualitative mapping looks at science initiatives that aimed to enhance regional cooperation, both in the BSR itself and between those countries and the EU. There has been widespread commitment and willingness from the EU and the BSR to involve in science cooperation projects, and the projects under FP6, FP7 and H2020 did not face acceptance issues from national or regional leaders. However, implementation of the envisaged objectives and Action Plans has been quite often lacking or incomplete due to capacity issues or weak political commitment. Much more needs to be done in this area if the EU and the BS countries want to reach the full potential of the H2020 projects. On the other hand, a broader political framework that shows a clear vision of the EU towards the BSR is lacking, as the Black Sea Synergy (BSS) has been inactive and the Eastern Partnership has been gaining more momentum and thus overshadowed the BSS. Moreover, political tensions in the BSR will push the EU to opt for a more careful approach towards the region, where either all stakeholders will have to be better involved, or some stakeholders should be left out to ensure a better functioning of future projects

Identification and evaluation of linear damping models in beam vibrations

Sensitive method, identifying effective damping mechanisms, involves comparing experimentally determined ratio of first to second mode magnification factors related to common point on beam. Cluster size has little effect on frequencies of elements, magnification factor decreases with cluster size, and viscous and stress damping are dominant damping mechanisms