Numerical study of the seasonal salinity budget of the upper ocean in the Bay of Bengal in 2014

Impact factors on the salinity budget, especially the eddy salt fluxes and smaller-scale diffusive salt fluxes for the upper 50 m of the Bay of Bengal(BoB) in 2014 are investigated using a box model based on the Regional Ocean Modeling System(ROMS) daily outputs. The model results reproduce that the precipitation and river runoff s are the dominant factors modulating the sharp salinity decrease during the summer monsoon season. The analysis shows that the salinity increase after the summer monsoon is mostly due to the meridional advective and diffusive salt fluxes. The vertical advective salt flux, which is sensitive to the different signals of the wind stress curl, plays an important role in balancing the salinity change induced by the meridional advective salt flux during both the summer and winter monsoon seasons. Distinctive spatial mesoscale structures are presented in the eddy salt flux throughout the year, and their contributions are sizeable(over 30% in the meridional direction and about 10%–30% in the vertical direction). The meridional eddy salt flux is larger in the monsoon seasons than that in the inter-monsoon seasons, and in a positive pattern near the western boundary during the winter monsoon and autumn inter-monsoon. The vertical eddy salt flux makes an important contribution to the salinity budget, especially along the coastal area and around the Andaman and Nicobar Islands. The vertical eddy salt flux becomes large when a tropical cyclone passes the area.

Eddy diffusivity and coherent mesoscale eddy analysis in the Southern Ocean

The spatial distribution of eddy diffusivity,basic characteristics of coherent mesoscale eddies and their relationship are analyzed from numerical model outputs in the Southern Ocean.Mesoscale fluctuation information is obtained by a temporal-spatial filtering method,and the eddy diffusivity is calculated using a linear regression analysis between isoneutral thickness flux and large-scale isoneutral thickness gradient.The eddy diffusivity is on the order of O(103 m2/s)with a significant spatial variation,and it is larger in the area with strong coherent mesoscale eddy activity.The mesoscale eddies are mainly located in the upper ocean layer,with the average intensity no larger than 0.2.The mean radius of the coherent mesoscale cyclonic(anticyclonic)eddy gradually decays from(121.2±10.4)km((117.8±9.6)km)at 30°S to(43.9±5.3)km((44.7±4.9)km)at 65°S.Their vertical penetration depths(lifespans)are deeper(longer)between the northern side of the Subpolar Antarctic Front and 48°S.The normalized eddy diffusivity and coherent mesoscale eddy activity show a significant positive correlation,indicating that coherent mesoscale eddy plays an important role in eddy diffusivity.

Submesoscale eddies in the East China Sea detected from SAR images

Seven-year(2005-2011)Synthetic Aperture Radar(SAR)images are applied to study oceanic eddies in the East China Sea.It is found that most of these eddies detected from the SAR images are less than 10 km,which are submesoscale eddies.Seasonal differences are evident in the distribution of eddies,with the highest and the lowest number of eddies noted in summer and winter,respectively.Since slick streaks in SAR images look dark,an eddy identified due to the slicks is referred to as“black eddy”.As a result of wave-current interactions in the zones of current shear,it can be seen that an eddy exhibits a bright curve,the eddy is called“white eddy”.During the seven years,95 black eddies and 50 white eddies are identified in the study area.Black eddies are found in the whole study area while white eddies are mainly distributed in the vicinity of the Kuroshio Current.This study suggests that the distribution of the white eddy is denser around the Kuroshio because of the strong shear in the Kuroshio region.In terms of the eddy sizes,white eddies are generally smaller than black eddies.

Sri Lanka seasonal warm pools

Sri Lanka seasonal warm pools(SSWPs)with high sea surface temperature(SST)(greater than 29.6℃in summer and greater than 28℃in winter)around the Sri Lanka Island are discovered using 37-year(1982–2018)satellite remote sensing SST data.It is identifi ed that during the onset of the summer(winter)monsoon,the maximum SST in the SSWPs can be 1.8℃(0.8℃)higher than the surrounding ocean.Due to orographic infl uences,the wind intensity on the leeward side of Sri Lanka is weakened,reducing evaporation and oceanic mixing,and resulting in higher SST.The analysis of the long-term data shows that SSWPs are related to El Niño-Southern Oscillation(ENSO)events.Background currents are also found to play important roles in governing the SSWPs intensities through the heat advection.

Development and engineering application of integratedsafety monitoring systems for China’s high-speed trains

With the improvement of the running speed of China’s high-speed trains,the demands for running status monitoring and security assurance of High-speed Electric Multiple Units(EMU)have increased significantly.However,the current safety monitoring systems are independent,which is not conducive to the comprehensive monitoring and information sharing of the whole vehicle.The temperature monitoring of running gear is insensitive to early failures.How to develop a train operation safety monitoring system with strong engineering implementation and high integration is a key problem to be solved.For the monitoring of running stationarity,frame stability and running gear health of China’s high-speed trains,an integrated safety monitoring system framework is designed,and the logic and algorithm for the diagnosis of stationarity,stability and health states of rotating parts are constructed.Monitoring software which fused the temperature,high and low frequency vibration data is developed,and the design and installation of the vibration temperature composite sensors are completed.The research results have realized the integration and comprehensive processing of multiple monitoring systems,completed the improvement from single component and vehicle-level safety monitoring to multi-system,train-level and interactive monitoring.In the process of real vehicle application,the developed monitoring system acquires the vehicle operation status data accurately and in real time.The constructed diagnosis algorithm and logic evaluates the vehicle operation status accurately and in a timely manner,and avoids the progression from fault to accident.The research results show that the integrated safety monitoring system can provide technical support for train operation safety.

Short-term effects of biochar and gypsum on soil hydraulic properties and sodicity in a saline-alkali soil

Salt and sodicity of saline-alkali soil adversely affect the construction of ecological landscapes and negatively impact crop production.The reclamation potential of biochar(BC,wheat straw biochar applied at\%by weight),gypsum(G,0.4%by weight),and gypsum coupled with biochar(GBC)was examined in this laboratory-based study by evaluating their effects on a saline-alkali soil(silt loam)with no amendment as a control(CK).Saline ice and fresh water(simulated rainfall)were leached through soil columns to investigate changes in salt content,sodium adsorption ratio(SAR),alkalinity,and pH of the leachate and the soil.Results showed that saturated water content and field water capacity(FWC)significantly increased by 4.4%and 5.6%,respectively,in the BC treatment after a short incubation time.Co-application of biochar and gypsum(GBC)increased soil saturated hydraulic conductivity(Ks)by 58.4%,which was also significantly higher than the sole addition.Electrical conductivity(EC)of the leachate decreased sharply after saline ice leaching;subsequent freshwater leaching accelerated the removal of the rest of the salts,irrespective of the amendment application.However,the application of gypsum(G and GB)significantly enhanced the removal of exchangeable Na^+and reduced leachate SAR.After leaching,the soil salt content decreased significantly for all treatments.The application of gypsum resulted in a significantly lower soil pH,exchangeable sodium percentage(ESP),SAR,and alkalinity values than those recorded for the CK and BC treatments.These results demonstrated that the co-application of gypsum and biochar could improve saline-alkali soil hydraulic conductivity and decrease leaching-induced sodicity over a short period.

High-resolution sea surface wind speeds of Super Typhoon Lekima (2019) retrieved by Gaofen-3 SAR

Gaofen-3(GF-3)is the first Chinese spaceborne multi-polarization synthetic aperture radar(SAR)instrument at C-band(5.43 GHz).In this paper,we use data collected from GF-3 to observe Super Typhoon Lekima(2019)in the East China Sea.Using a VH-polarized wide ScanSAR(WSC)image,ocean surface wind speeds at 100m horizontal resolution are obtained at 21:56:59 UTC on 8 August 2019,with the maximum wind speed,38.9 m·s^(-1).Validating the SAR-retrieved winds with buoymeasured wind speeds,we find that the root mean square error(RMSE)is 1.86 m·s^(-1),and correlation coefficient,0.92.This suggests that wind speeds retrieved from GF-3 SAR are reliable.Both the European Centre for MediumRange Weather Forecasts(ECMWF)fine grid operational forecast products with spatial resolution,and China Global/Regional Assimilation and Prediction Enhance System(GRAPES)have good performances on surface wind prediction under weak wind speed condition(<24 m·s^(-1)),but underestimate the maximum wind speed when the storm is intensified as a severe tropical storm(>24m·s^(-1)).With respect to SAR-retrieved wind speeds,the RMSEs are 5.24 m·s^(–1) for ECMWF and 5.17 m·s^(–1) for GRAPES,with biases of 4.16 m·s^(–1) for ECMWF and 3.84 m·s^(-1)for GRAPES during Super Typhoon Lekima(2019).