Response of the Hadley Circulation to Climate Change in an Aquaplanet GCM Coupled to a Simple Representation of Ocean Heat Transport

It is unclear how the width and strength of the Hadley circulation are controlled and how they respond to climate changes. Simulations of global warming scenarios with comprehensive climate models suggest the Hadley circulation may widen and weaken as the climate warms. But these changes are not quantitatively consistent among models, and how they come about is not understood. Here, a wide range of climates is simulated with an idealized moist general circulation model (GCM) coupled to a simple representation of ocean heat transport, in order to place past and possible future changes in the Hadley circulation into a broader context and to investigate the mechanisms responsible for them. By comparison of simulations with and without ocean heat transport, it is shown that it is essential to take low-latitude ocean heat transport and its coupling to wind stress into account to obtain Hadley circulations in a dynamical regime resembling Earth’s, particularly in climates resembling present-day Earth’s and colder. As the optical thickness of an idealized longwave absorber in the simulations is increased and the climate warms, the Hadley circulation strengthens in colder climates and weakens in warmer climates; it has maximum strength in a climate close to present-day Earth’s. In climates resembling present-day Earth’s and colder, the Hadley circulation strength is largely controlled by the divergence of angular momentum fluxes associated with eddies of midlatitude origin; the latter scale with the mean available potential energy in midlatitudes. The importance of these eddy momentum fluxes for the Hadley circulation strength gradually diminishes as the climate warms. The Hadley circulation generally widens as the climate warms, but at a modest rate that depends sensitively on how it is determined

Building self-evaluation skills through criterion-referenced assessment in public relations

Although technical skills in public relations are essential to practice, skills in self-evaluation, critical thinking, and problem solving are required when new practitioners move to management roles (Van Leuven, 1999). Public relations courses integrate specialist subject knowledge with graduate skill sets and capabilities in non-technical areas (Butcher & Stefani, 1995). Given that autonomy in learning is a skill valued by employers (Clifford, 1999) and advocated by accrediting professional bodies (Anderson, 1999), this study explores how public relations students build skills in and perceive the practice of self-evaluation. Currently, the public relations education literature presents a limited treatment of self-evaluation. Therefore, this study is guided mostly by the education literature and uses criterion-referenced assessment to determine how more than 150 students understand assessment requirements, assess their strengths and weaknesses, and interpret the differences between their self and their tutor's judgement of performance. The results indicate strong support for student understanding of assessment requirements and self-evaluation techniques but lower than expected support for understanding the differences between their self and tutor judgements. These findings are significant to educators, practitioners and professional bodies as they have implications for lifelong learning for public relations professionals