Ex situ echo sounder target strengths of ice krill Euphausia crystallorophias

Ice krill is the keystone species in the neritic ecosystem in the Southern Ocean,where it replaces the more oceanic Antarctic krill. It is essential to understand the variation of target strength(TS in d B re 1 m 2) with the different body size to accurately estimate ice krill stocks. However,there is comparatively little knowledge of the acoustic backscatter of ice krill. The TS of individual,formalin-preserved,tethered ice krill was measured in a freshwater test tank at 38,120,and 200 k Hz with a calibrated split-beam echo sounder system. Mean TS was obtained from 21 individual ice krill with a broad range of body lengths(L :13–36 mm). The length( L,mm) to wet weight( W; mg) relationship for ice krill was W =0.001 218×103 × L 3.53( R 2= 0.96). The mean TS-to-length relationship were TS3 8 k Hz =-177.4+57log 10( L),( R 2 = 0.86); TS 120 k Hz =-129.9+31.56 log 10( L),( R 2 =0.87); and TS 200 k Hz =-117.6+24.66log1 0( L),( R 2 =0.84). Empirical estimates of the relationship between the TS and body length of ice krill were established at 38,120,and 200 k Hz and compared with predictions obtained from both the linear regression model of Greene et al.(1991) and the Stochastic Distorted Wave Born Approximation(SDWBA) model. This result might be applied to improve acoustic detection and density estimation of ice krill in the Southern Ocean. Further comparative studies are needed with in situ target strength including various body lengths of ice krill.     

The influence of thermohaline fronts on chlorophyll a concentrations during spring and summer in the southeastern Yellow Sea

A spatial and temporal variation in physiochemical parameters in the southeastern Yellow Sea(YS) is investigated in the spring and summer of 2009 to 2011.Nutrient show a strong negative relationship with chlorophyll a(Chl a) concentration in spring,and the subsurface chlorophyll a maxima(SCM) layer was associated with the nitracline in summer.In summer,the SCM was usually found within or above the pycnocline and at the depths of shoals from the open sea to the coastal sea due to tidal and/or topographical fronts in the southernmost study area.High Chl a concentrations were found in the central southern YS,where the YS cold water layer expanded under the pycnocline and encountered water masses during spring and summer.After a typhoon in the summer of 2011,Chl a concentration increased,especially in the central southern YS,where cold waters occurred below the pycnocline.The results suggest that the development of thermohaline fronts may play an important role in the growth and accumulation of phytoplankton biomass in the upper layer of the southeastern YS during spring and summer.     

Distribution of dinoflagellate cysts in Yellow Sea sediments

To investigate the distribution,abundance,and species composition of dinoflagellate cysts in the Yellow Sea,surface sediment samples were collected at 37 sites,including the Korean dump site.Twenty-one dinoflagellate cyst taxa were identified,with the assemblages dominated mainly by Spiniferites bulloideus,Operculodinium centrocarpum,and cyst of Alexandrium catenella/tamarense type.A high frequency of O.centrocarpum in the Yellow Sea was observed for the first time,and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang(Yangtze) River runoff.Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight,and high cyst concentrations were recorded adjacent to the dumping site.This result suggests that anthropogenic activities such as ocean dumping stimulate the growth of dinoflagellates in the Yellow Sea,which in turn leads to high levels of dinoflagellate cyst production.     

Cloud Radiative Effects and Changes Simulated by the Coupled Model Intercomparison Project Phase 5 Models

Using 32 CMIP5(Coupled Model Intercomparison Project Phase 5) models, this study examines the veracity in the simulation of cloud amount and their radiative effects(CREs) in the historical run driven by observed external radiative forcing for 1850–2005, and their future changes in the RCP(Representative Concentration Pathway) 4.5 scenario runs for2006–2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics,four models—ACCESS1.0, ACCESS1.3, Had GEM2-CC, and Had GEM2-ES—are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average.All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about-0.99% K~(-1)and net radiative warming of 0.46 W m~(-2)K~(-1), suggesting a role of positive feedback to global warming.     

Beta gyres in global analysis fields

A three-component decomposition is applied to global analysis data to show the existence of a beta gyre, which causes Tropical Cyclone (TC) to drift from a large-scale environmental steering current. Analyses from the Global Data Assimilation and Prediction System (GDAPS) of the Korea Meteorological Administration (KMA), the Global Forecast System (GFS) of NCEP, and the Navy Operational Global Atmospheric Prediction System (NOGAPS) are used in this study. The structure of the beta gyre obtained in our analyses is in good agreement with the theoretical structure, with a cyclonic circulation to the southwest of the TC center, an anticyclonic circulation to the northeast, and a ventilation flow directed northwestward near the center. The circulation of the beta gyre is strongest at the 850-hPa level where the cyclonically swirling primary circulation is strongest, and decreases with height, in a pyramid shape similar to the primary circulation. The individual structure of the beta gyre is case- and model-dependent. At a certain analysis time, one model may clearly reveal a well-defined beta gyre, but the other models may not. Within one model, the beta gyre may be well defined at some analysis times, but not at other times. The structure of the beta gyre in the analysis field is determined by the nature of the vortex initialization scheme and the model behavior during the 6-h forecast in the operational data assimilation cycle.     

How do weather characteristics change in a warming climate?

The possible change in the characteristics of weather in the future should be considered as important as the mean climate change because the increasing risk of extremes is related to the variability on daily time scales. The weather characteristics can be represented by the climatological mean interdiurnal (day-to-day) variability (MIDV). This paper first assessed the phase five of the Coupled Model Intercomparison Project coupled climate models’ capability to represent MIDV for the surface maximum and minimum temperature, surface wind speed and precipitation under the present climate condition. Based on the assessment, we selected three best models for projecting future change. We found that the future changes in MIDV are characterized by: (a) a marked reduction in surface maximum and minimum temperature over high latitudes during the cold season; (b) a stronger reduction in the surface minimum temperature than in the maximum temperature; (c) a reduction in surface wind speed over large parts of lands in Northern Hemisphere (NH) during NH spring; (d) a noticeable increase in precipitation in NH mid-high latitudes in NH spring and winter, and in particular over East Asia throughout most of the year.     

天体运动的轨道偏心率研究概述---从恒星系统到行星系统

偏心率是描述天体运动轨道的重要参数之一, 能够为揭示天体的动力学演化提供重要线索, 进而帮助理解天体形成与演化的过程及背后的物理机制. 随着天文观测技术的不断发展, 人们对于天体运动轨道的研究已经走出太阳系, 包含的系统也从大质量端的恒星系统延伸到了低质量端的行星系统. 聚焦天体轨道偏心率研究, 回顾了目前在恒星系统(包括主序恒星、褐矮星以及致密星)和行星系统(包括太阳系外巨行星以及``超级地球''、``亚海王星''等小质量系外行星)方面取得的进展, 总结了不同尺度结构下偏心率研究的一些共同之处和待解决的问题. 并结合当下和未来的相关天文观测设备和项目, 对未来天体轨道偏心率方面的研究工作进行了展望.     

Beta Gyres in Global Analysis Fields

A three-component decomposition is applied to global analysis data to show the existence of a beta gyre, which causes Tropical Cyclone (TC) to drift from a large-scale environmental steering current. Analyses from the Global Data Assimilation and Prediction System (GDAPS) of the Korea Meteorological Adminis-tration (KMA), the Global Forecast System (GFS) of NCEP, and the Navy Operational Global Atmospheric Prediction System (NOGAPS) are used in this study. The structure of the beta gyre obtained in our anal...     

Implementation of turbulent mixing over a stratocumulus-topped boundary layer and its impact in a GCM

The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer (STBL) was investigated using the YONU AGCM (Yonsei University Atmospheric General Circulation Model). To consider the impact of clouds on the turbulence production, the turbulence mixing term, driven by radiative cooling at the cloud top, is implemented as an extended non-local diffiusion scheme. In the model with this new scheme, the STBL parameterization significantly influences the lower atmosphere over the tropical and...