El Niño and the delayed action oscillator

We study the dynamics of the El Niño phenomenon using the mathematical model of delayedaction oscillator (DAO). Topics such as the influence of the annual cycle, global warming, stochastic influences due to weather conditions and even off-equatorial heat-sinks can all be discussed using only modest analytical and numerical resources. Thus the DAO allows for a pedagogical introduction to the science of El Niño and La Niña while at the same time avoiding the need for large-scale computing resources normally associated with much more sophisticated coupled atmosphere-ocean general circulation models. It is an approach which is ideally suited for student projects both at high school and undergraduate level

Atmospheric Response to the North Pacific Enabled by Daily Sea Surface Temperature Variability

Ocean–atmosphere interactions play a key role in climate variability on a wide range of time scales from seasonal to decadal and longer. The extratropical oceans are thought to exert noticeable feedbacks on the atmosphere especially on decadal and longer time scales, yet the large-scale atmospheric response to anomalous extratropical sea surface temperature (SST) is still under debate. Here we show, by means of dedicated high-resolution atmospheric model experiments, that sufficient daily variability in the extratropical background SST needs to be resolved to force a statistically significant large-scale atmospheric response to decadal North Pacific SST anomalies associated with the Pacific Decadal Oscillation (PDO), which is consistent with observations. The large-scale response is mediated by atmospheric eddies. This implies that daily extratropical SST fluctuations must be simulated by the ocean components and resolved by the atmospheric components of global climate models to enable realistic simulation of decadal North Pacific sector climate variability

Upwelling in the Gulf of Guinea

Upwelling along the northern coast of the Gulf of Guinea occurs only between June and October even though the local winds are favorable for upwelling throughout the year and have no seasonal variability. Away from the coast, near the equator for example, the winds do vary seasonally and cause large scale oceanographic conditions in the Gulf of Guinea to change seasonally...

The effects of coastal geometry on equatorial waves (forced waves in the Gulf of Guinea)

The response of a stratified, semi-infinite equatorial ocean, bounded by a zonal coast close to the equator, to forcing at a given frequency and zonal wavenumber, is considered. If the coast is distant from the equator, the vertically propagating waves that are excited could include an infinite set of inertia-gravity waves, a finite set of Rossby waves, a Rossby-gravity wave and a coastally or equatorially trapped Kelvin wave...

The Effect of Online Gaming on Commercial Casino Revenue

This study estimates the effect of the online gaming industry on the commercial casino gaming industry. The findings from this study suggest that during the pre-UIGEA period, online gaming was a moderate substitute good for brick and mortar gaming in the U.S. During this early period in the online gaming market, which was characterized by loose regulation and relatively easy access, online gaming revenue is estimated to have cannibalized commercial casino revenue at a rate of 27 to 30 cents on the dollar. A discussion of this finding’s relevance to the current gaming market and the related policy considerations is provided. This study also led to the discovery of a seemingly valid instrumental variable, internet user rates, which can be used to correct internet gaming coefficient estimates for potential bias in future studies

What is the climate system able to do ‘on its own’?

The climate of the Earth, like planetary climates in general, is broadly controlled by solar irradiation, planetary albedo and emissivity as well as its rotation rate and distribution of land (with its orography) and oceans. However, the majority of climate fluctuations that affect mankind are internal modes of the general circulation of the atmosphere and the oceans. Some of these modes, such as El Nino-Southern Oscillation (ENSO), are quasi-regular and have some longer-term predictive skill; others like the Arctic and Antarctic Oscillation are chaotic and generally unpredictable beyond a few weeks. Studies using general circulation models indicate that internal processes dominate the regional climate and that some like ENSO events have even distinct global signatures. This is one of the reasons why it is so difficult to separate internal climate processes from external ones caused, for example, by changes in greenhouse gases and solar irradiation. However, the accumulation of the warmest seasons during the latest two decades is lending strong support to the forcing of the greenhouse gases. As models are getting more comprehensive, they show a gradually broader range of internal processes including those on longer time scales, challenging the interpretation of the causes of past and present climate events further

Seasonal cycle in the upper equatorial Atlantic Ocean

The dynamics of the seasonal cycle in the upper equatorial Atlantic ocean are studied using observations and a hierarchy of ocean models. Distinctive features of the seasonal cycle are strong annual and semiannual components: eastward (westward) propagating sea surface height (SSH) and thermocline depth at the equator (off the equator) and westward propagating surface zonal currents at the equator. Modelling results show that linear theory can explain the seasonal cycle in thermocline depth and SSH. While first-order linear theory can also explain the structure of the seasonal cycle of surface zonal currents at the equator, nonlinear terms are required; they weaken the variability and improve its phase and zonal extent. The important terms are meridional and vertical advection and vertical diffusion of zonal momentum. The linear solution is essentially determined by the four gravest baroclinic modes and Kelvin and first meridional mode Rossby waves. The eastward propagation in thermocline depth at the equator results from the Kelvin wave contribution, while the westward propagation in thermocline depth off the equator and surface zonal currents at the equator result from the first meridional mode Rossby wave. The contribution of Kelvin and Rossby waves generated by boundary reflections equals that of the directly forced waves. The semiannual cycle in zonal winds although much weaker than the annual component forces a strong semiannual component in SSH and surface zonal currents, because it excites the basin mode of the second baroclinc mode. This explains the observed feature in the seasonal cycle from March to August