Instantaneous Convergence Research Articles

Individual Time Period Analyses over the GATE Ship Array

Abstract Diagnostic moisture and dry static energy budgets for the GATE A/B-scale area are performed for individual time periods using rawinsonde and satellite data. The data are sufficiently accurate to permit quantitative analysis of that area with 3–6 h time resolution. Each budget is used to estimate the net condensation rate for every time period. The budget condensation rates slightly exceed radar rainfall estimates for the GATE master array and the radar values lag the budget condensation by 4–6 h during major rainfall episodes. Storage of liquid water and unsampled vapor in clouds can account for a large portion of the observed lag. The present results indicate that observed 3–6 h lags between, low-level mass convergence and echo growth during GATE result primarily from the lag between condensation and precipitation during convective system evolution. The release of latent heat in a tropical convective system appears to be closely related to the instantaneous mass convergence below 700 mb. Budget-...

Violent deformation of rock near deep-level, tabular excavations—seismic events

abstract Inelastic deformation of the rock near the edges of the thin tabular excavations (stopes) of deep-level mines sometimes occurs violently, resulting in a seismic event. These seismic events are produced in the highly-stressed rock near the edges of the stopes and appear to be the result of shear failure across a plane; these conclusions are based on seismic as well as underground observations. The seismic events occurring near stopes can be described using a model based on the theory of dislocations; they result from two edge dislocations of opposite sign annihilating each other and releasing energy. The instantaneous convergence of the stope that is observed to occur at the time of a large mine tremor is compatible with the observed seismic energy of the tremor, according to analysis based on the dislocation model.