Tropical precipitation–buoyancy relationship in Convectively Coupled Waves over South America region

<p>In this work, the tropical wave precipitation-buoyancy relationship is revisited by analyzing 4-times daily wave-filtered brightness temperature, reanalysis, and radiosonde datasets over tropical South America during the wet season. Prior studies demonstrated that an integrated measure of buoyancy well-diagnoses precipitation over land and ocean. However, it is an open question whether the buoyancy-based approach can yield a robust relation to precipitation for equatorial wave disturbances. To advance our understanding of this relationship, a comprehensive analysis of their vertical thermodynamic structure and potential interactions with the basic state is also presented. An emphasis is placed on understanding the convection coupling mechanism in convectively coupled Kelvin and inertia-gravity waves. It will be shown that buoyancy is a better predictor of convection for these disturbances than the often-used moist static energy (MSE). Examination of this discrepancy reveals that a cooling of the lower troposphere by gravity wave motions, which reduces MSE, is key to the production of precipitation in these disturbances.</p>

Variations in Winter Ocean Wave Climate in the Japan Sea under the Global Warming Condition

Future variations in the ocean wave climate caused by global warming could affect various coastal issues. Using a third-generation wave model, this study produced projections of the ocean wave climate for winter around Japan, focusing on the Japan Sea side. Wave simulation forcing (sea surface wind) was generated through five different global warming experiments. More than half the future wave projections showed an increasing tendency of the climatological mean significant wave height during winter. However, the maximum significant wave height did not show any clear tendency in future variation. The top 1% of significant wave heights and mean wave periods showed apparent increases in frequencies of higher/longer waves in three out of the five future projections. Frequency distributions of significant wave height, mean wave period, mean wavelength and wave direction showed various future variations (reduction of small ocean waves, increasing frequency of waves from the west). There are large uncertainties in future variations of wave climate in the Japan Sea, but the high probability of variations in daily wave climate is recognized, based on the future wave projections. Variations in daily wave climate are important because they could affect the topography and environment of the coast through long-term repetitive actions.

BEACH AND SURF ZONE EQUILIBRIA AND RESPONSE TIMES

Analyses were performed on a 6% year time series of daily wave data, daily beach state data and monthly beach and surf zone profile data. Beach state changes, which involve the relatively rapid redistribution of sediment already stored locally, are predictable in terms of Dean's (3) simple parameter A • H, /(w T) where H, is breaker height, w is sediment fall velocity and T is wave period. Each of the six beach states has a different equilibrium range of S2 values and the direction of change (erosion or accretion) depends on the departure from the equilibrium association. Empirical eigenvector analyses performed on the profile data permitted separation of different response components. The lower order vectors expressing the grosser aspects of the profile features such as beach volume and surf zone gradient displayed maximum variance at periods in excess of 2 years whereas much shorter response times characterized the higher order components such as bar-trough shapes and asymmetries. We infer that the fast response, and more predictable, components of beach and surf zone change largely involve smaller scale sediment exchanges between the beach and surf zone whereas the slower responses are related to larger scale exchanges between the surf zone and the inner continental shelf.