Dynamical contribution to formation of an ozone mini hole in the Northern Hemisphere in mid-winter

Ozone mini holes are localized and transient (several days) column ozone amount depletion phenomena which often appear over northern Europe. In early February 1989, the extremely low ozone value of 172 DU was observed by Total Ozone Mapping Spectrometer observation. Quantitative analyses of this event using a forward and backward trajectory method show that the total ozone depletion is by uplift of air throughout the lower stratosphere, whereas the effect of horizontal advection of ozone-poor air from lower latitudes is relatively small. Similar results are obtained for 4 other severe mini hole cases. However, these two dynamical effects cannot fully explain the total ozone depletion, which implies the existence of other possible processes responsible for ozone mini holes

Surface Roughness Control Based on Digital Copy Milling Concept to Achieve Autonomous Milling Operation

AbstractIn order to develop an autonomous and intelligent machine tool, a system named Digital Copy Milling (DCM) was developed in our previous studies. The DCM generates tool paths in real time based on the principle of copy milling. In the DCM, the cutting tool is controlled dynamically to follow the surface of CAD model corresponding to the machined shape without any NC program. In this study, surface roughness control of finished surface is performed as an enhanced function of DCM. From rough-cut to semi-finish-cut and finish-cut operations, the DCM selects cutting conditions and generates tool paths dynamically to satisfy instructed surface roughness Ra. The experimental verification was performed successfully

Tropical water vapour in the lower stratosphere and its relationship to tropical/extratropical dynamical processes in ERA5

Stratospheric water vapour (SWV), in spite of its low concentration in the stratosphere as compared to the troposphere, contributes significantly to the surface energy budget and can have an influence on the surface climate. This study investigates the dynamical processes that determine SWV on interannual to decadal time‐scales. First, we evaluate two SWV reanalysis products and show that SWV is better represented in a new‐generation reanalysis product, ERA5, than in its predecessor, ERA‐Interim. In particular, it is shown that SWV in ERA5 is highly consistent with observational data obtained from the SPARC Data Initiative Multi‐Instrument Mean (SDI MIM). Second, we investigate the variability of tropical SWV and its relationship to dynamical stratospheric variables. The analyses show that the interannual variability in the tropical lower‐stratospheric water vapour is closely linked to the tropical Quasi‐Biennial Oscillation (QBO). When westerlies occupy the middle stratosphere and easterlies the lower stratosphere, a decrease is observed in lower‐stratospheric water vapour due to a colder tropical tropopause and a QBO‐induced enhanced residual circulation. On decadal time‐scales, the composite analysis of the boreal winter in two typical periods shows that less SWV is related to a warm anomaly in the North Atlantic sea‐surface temperature, which leads to stronger upward propagation of planetary wave activity at high latitudes, a weaker polar vortex and an enhanced residual circulation. The opposite occurs during periods with higher concentrations of SWV