Limited Sea Surface Temperature Cooling Due to the Barrier Layer Promoting Super Typhoon Mangkhut(2018)

This study investigates the impact of the salinity barrier layer(BL)on the upper ocean response to Super Typhoon Mangkhut(2018)in the western North Pacific.After the passage of Mangkhut,a noticeable increase(~0.6 psu)in sea surface salinity and a weak decrease(<1℃)in sea surface temperature(SST)were observed on the right side of the typhoon track.Mangkhut-induced SST change can be divided into the three stages,corresponding to the variations in BL thickness and SST before,during,and after the passage of Mangkhut.During the pre-typhoon stage,SST slightly warmed due to the entrainment of BL warm water,which suppressed the cooling induced by surface heat fluxes and horizontal advection.During the forced stage,SST cooling was controlled by entrainment,and the preexisting BL reduced the total cooling by 0.89℃ d-1,thus significantly weakening the overall SST cooling induced by Mangkhut.During the relaxation stage,the SST cooling was primarily caused by the entrainment.Our results indicate that a preexisting BL can limit typhoon-induced SST cooling by suppressing the entrainment of cold thermocline water,which contributed to Mangkhut becoming the strongest typhoon in 2018.

Interannual variability in the sea surface cooling induced by tropical cyclones in the South China Sea

Sea surface cooling induced by tropical cyclones(TCs)is an important component of air-sea interactions.Using coordinate transformation and composite analysis methods,we examined the interannual variability in TCinduced sea surface cooling(TCSSC)in the South China Sea(SCS).The frequency of surface cooling cases was over 86%and that of surface warming cases was less than 14%.The magnitude of TCSSC was defined as the absolute value of TCSSC.The maximum magnitude of TCSSC occurred on the right side of the TC track,and the mean magnitude of TCSSC decreased by 0.04℃/a from 2006 to 2018.The interannual variability in TCSSC was highly correlated with the TC translation speed and pre-TC mixed layer depth.Notably,TCSSC got enhanced in El Nino years of 2007,2010,and 2015.The El Nino types were suggested to determine the occurring periods of strong TCSSC via controlling the positions of SCS anticyclones,which brought pre-TC shallow mixed layer and caused strong TCSSC via vertical mixing process during El Nino events.To quantify how the anticyclone influences TCSSC,we need to use mixed layer heat balances model in the next study.

Simulation and Causes of Eastern Antarctica Surface Cooling Related to Ozone Depletion during Austral Summer in FGOALS-s2

Two parallel sets of numerical experiments （an ozone-hole simulation and a non-ozone-hole simulation） were performed to investigate the effect of ozone depletion on surface temperature change using the second spectral version of the Flexible Global Ocean-Atmosphere-Land System model （FGOALS-s2）, focusing on the eastern Antarctica （EA） continent in austral summer. First, we evaluated the ability of the model to simulate the EA surface cooling, and found the model can successfully reproduce the cooling trend of the EA surface, as well as the circulation change circling the South Pole in the past 30 years. Second, we compared the two experiments and discovered that the ozone depletion causes the cooling trend and strengthens the circumpolar westerly flow. We further investigated the causes of the EA surface cooling associated with the ozone hole and found two major contributors. The first is the ozone-hole direct radiation effect （DRE） upon the surface that happens because the decrease of the downward longwave （LW） radiation overcomes the increase of the downward shortwave （SW） radiation under clear sky. The second is the cloud radiation effect （CRE） induced by ozone depletion, which happens because the decreased downward SW radiation overcomes the increased downward LW radiation in the case of increased cloud. Although the CRE is theoretically opposite to the DRE, their final net effect makes comparable contributions to the EA surface cooling. Compared with the surface radiation budget, the surface heat flux budgets have a much smaller contribution. We additionally note that the CRE is basically ascribed to the circulation change.

Latitudinal and Seasonal Variations in Tropical Cyclone-Induced Ocean Surface Cooling in the Tropical Western North Pacific

The passage of tropical cyclones induces ocean surface cooling through vertical mixing,upwelling,and surface heat loss.The dependence of tropical cyclone-induced ocean surface cooling on the intensity and translation speed of tropical cyclones has been documented in previous studies.The present study investigates the latitudinal and seasonal variations in tropical cyclone-induced ocean surface cooling in the tropical western North Pacific based on data for the 2001–2020 period.Our analysis focuses on the open ocean(0°–25°N,130°E–180°)to reduce the interference of coastal topography so that the obtained results better represent the influences of the intensity and translation speed of tropical cyclones.Our analysis confirms the dependence on the intensity and translation speed of tropical cyclone-induced cooling.The new findings are as follows.First,the time to reach the maximum cooling increases with the magnitude of the maximum cooling.Second,the magnitude of ocean surface cooling increases with latitude in the tropical region for tropical cyclones with different intensities and translation speeds.Third,the ocean surface cooling is larger in summer and autumn than in spring for tropical cyclones with different intensities and translation speeds.Fourth,the dependence of ocean surface cooling on the translation speed is more obvious at higher latitudes in the tropics and less apparent in spring.These new findings add to the existing knowledge of the impacts of tropical cyclone intensity and translation speed on ocean surface cooling.

The Effect of Warm Water and Its Weak Negative Feedback on the Rapid Intensification of Typhoon Hato(2017)

Typhoon Hato (2017) went through a rapid intensification (RI) process before making landfall in Zhuhai,Guangdong Province, as the observational data shows. Within 24 hours, its minimum sea level pressure deepened by35hPa and its maximum sustained wind speed increased by 20m s-1. According to satellite observations, Hato encountered a large area of warm water and two warm core rings before the RI process, and the average sea surface temperature cooling (SSTC) induced by Hato was only around 0.73℃. Air-sea coupled simulations were implemented to investigate the specific impact of the warm water on its RI process. The results showed that the warm water played an important role by facilitating the RI process by around 20%. Sea surface temperature budget analysis showed that the SSTC induced by mixing mechanism was not obvious due to the warm water. Besides, the cold advection hardly caused any SSTC, either. Therefore, the SSTC induced by Hato was much weaker compared with that in general cases. The negative feedback between ocean and Hato was restrained and abundant heat and moisture were sufficiently supplied to Hato. The warm water helped heat flux increase by around 20%, too. Therefore, the warm water influenced the structure and the intensity of Hato. Although there might be other factors that also participated in the RI process, this study focused on air-sea interaction in tropical cyclone forecast and discussed the impact of warm water on the intensity and structure of a tropical cyclone.

Targeted temperature management in neurological intensive care unit

Targeted temperature management(TTM) shows the most promising neuroprotective therapy against hypoxic/ischemic encephalopathy(HIE).In addition, TTM is also useful for treatment of elevated intracranial pressure(ICP).HIE and elevated ICP are common catastrophic conditions in patients admitted in Neurologic intensive care unit(ICU).The most common cause of HIE is cardiac arrest.Randomized control trials demonstrate clinical benefits of TTM in patients with post-cardiac arrest.Although clinical benefit of ICP control by TTM in some specific critical condition, for an example in traumatic brain injury, is still controversial, efficacy of ICP control by TTM is confirmed by both in vivo and in vitro studies.Several methods of TTM have been reported in the literature.TTM can apply to various clinical conditions associated with hypoxic/ischemic brain injury and elevated ICP in Neurologic ICU.

Surface microstructure control of microalloyed steel during slab casting

Lots of work has been done to investigate slab surface microstructure evolution during continuous casting in order to improve hot ductility and avoid transverse cracks.The slab surface microstructure after continuous casting was characterized by optical microscopy,and the precipitation behavior was investigated by transmission electron microscopy.At the same time,the mechanical properties of the slabs were measured using a Gleeble 1500 Dthermal simulator and the transformation temperatures were examined by means of a thermal dilatometer.The experimental results show that homogeneous microstructure without film-like ferrites and chain-like precipitates at grain boundary can be obtained through surface intensive cooling and transverse cracks do not occur on the slab surface.For the experimental steel,fine ferrite can form at slab surface when the water flow rate is larger than 1560L/min at vertical section.As the distance to surface increases,microstructure turned to ferrite and pearlite.Moreover,nano-size carbonitrides precipitated in the ferrite grain and the size was larger at the junction of the dislocations.The mechanical experiment results show that the hot ductility of the sample deformed at 650°C was better than that of the sample deformed at 750°C.The reason is that filmlike ferrite formed at the grain boundary in the sample deformed at 750°C.Thus,the slab must be cooled quickly below Ar3 to prevent the occurrence of film-like ferrite and transverse cracks on the slab surface during casting.

Tool wear performance and surface integrity studies for milling DD5 Ni-based single crystal superalloy

Based on the results of slot milling experiments on the DD5 Ni-based single crystal superalloy(001) crystal plane along the [110]crystal direction, in this paper, efforts were devoted to investigate the tool wear process, wear mechanism and failure modes of the physical vapor deposition(PVD)-AlTiN and TiAlN coated tools under dry milling and water-based minimum quantity lubrication(MQL) conditions. The scanning electron microscope(SEM) morphological observation and energy dispersive X-ray spectroscopy(EDX) elements analysis methods were adopted. Moreover, under the water-based MQL condition, the surface integrity such as surface roughness, dimensional and shape accuracy, microhardness and microstructure alteration were researched. The results demonstrated that the tool edge severe adhesion with the work material, induced by the high Al content in the PVD-AlTiN coating caused the catastrophic tool tip fracture. In contrast, the PVD-TiAlN tool displayed a steady and uniform minor flank wear, even though the material peeling and slight chipping also occurred in the final stage. In addition, due to the high effective cooling and lubricating actions of the water-based MQL method, the PVD-TiAlN coated tool demonstrated intact tip geometry; consequently it could be repaired and reused even if the failure criterion was attained. Moreover, as the accumulative milling length and the tool wear increased, all indicators of the surface integrity forehand were deteriorated.

The Impact of Storm-Induced SST Cooling on Storm Size and Destructiveness: Results from Atmosphere-Ocean Coupled Simulations

In this study, both an atmospheric model [Weather Research and Forecasting(WRF) model] and an atmosphere(WRF)–ocean(Princeton Ocean Model;POM) coupled model are used to simulate the tropical cyclone(TC) Kaemi(2006). By comparing the simulation results of the models, effects of oceanic elements, especially the TC-induced sea surface temperature(SST) cooling, on the simulated TC size and destructiveness are identified and analyzed. The results show that there are no notable differences in the simulated TC track and its intensity between the uncoupled and coupled experiments;however, there are large differences in the TC size(i.e., the radius of gale-force wind)between the two experiments, and it is the TC-induced SST cooling that decreases the TC size. The SST cooling contributes to the decrease of air–sea moisture difference(ASMD) outside the TC eyewall, which subsequently leads to the decreases in surface enthalpy flux(SEF), radial sea-level pressure gradient, absolute vorticity advection, and wind speed outside the TC eyewall. As a result, the TC size and size-dependent TC destructive potential all decrease remarkably.

A MODEL FOR PROGRAMMING DESIGN INTERVENTIONS AIMED AT REDUCING THERMAL DISCOMFORT IN URBAN OPEN SPACES:A Case Study on the Politecnico di Milano Campus

The environmental quality of urban spaces is strongly related to the thermal comfort perceived by people in open areas.At the micro-scale of neighbourhoods,the mitigation of the heat island effect can improve both the well-being of cityusers in the public realm and the energy performance of buildings.A model intended for urban designers is presented,and it sets out to evaluate critical areas in the city context and define sustainable design solutions and concrete actions on the physical environment,in order to increase thermal comfort.In particular,variables used in the model are basically related to urban geometry,such as the accessibility of sunlight,sky view factors,aspect ratios of street canyons,and to the physical materials in the city,such as the albedo of horizontal and vertical surfaces and vegetation density.The technique is based on the use of algorithms defi ned in a Matlab environment and derived from image processing of Digital Elevation Models(DEMs)of the urban texture.The application was tested on the case study of the Politecnico di Milano’s main campus,located in the city of Milan.Especially in the case of limited resources,the results of the analysis suggest how public administrators and decision-makers could benefi t from programming specific site interventions,based on the identification of critical weaknesses emerging at several points in the city.Moreover,the study focuses on the application of cool surfaces,the role of building layout(shape and size)and the effects of increasing the vegetation.Even in the absence of expensive thermal imagery from remote sensing,but simply referring to available cartography,this low-cost technique makes it possible to very quickly set up feasible environmental strategies over extensive urban areas.Furthermore,this tool proves to be useful for existing urban areas,as well as for simulating the impact of new design schemes.