A 28-Year Climatological Analysis of Size Parameters for Northwestern Pacific Tropical Cyclones

A 28-year best track dataset containing size parameters that include the radii of the 15.4 m s^-1 winds （R15） and the 25.7 m s^-1 winds （R26） of tropical cyclones （TCs） in the Northwestern Pacific, the NCEP/ NCAR reanalysis dataset and the Extended Reconstructed Sea Surface Temperature （ERSST） dataset are employed in this study. The climatology of size parameters for the tropical cyclones in the Northwestern Pacific from 1977 to 2004 is investigated in terms of the spatial and temporal distributions. The results show that the major activity of TCs in the Northwestern Pacific is from July to October. A majority of TCs lie over the ocean west of 150°E, and a few TCs can intensify to the Saffir-Simpson （S-S） categories 4, 5. Both R15 and R26 tend to increase as the tropical cyclones intensify. The values of R15 and R26 are larger for intense TCs in the Northwestern Pacific than in the North Atlantic generally. Both R15 and R26 peak in October, and before and after October, R15 and R26 decrease, which is different from the case in the North Atlantic. The smaller R15s and R26s occur in a large range over the Northwestern Pacific, while the larger R15s and R26s mainly lie in the eastern ocean from Taiwan Island to the Philippine Islands where many tropical cyclones develop in intense systems. The tropical cyclones with size parameters of R15 or R26 on average take a longer time to intensify than to weaken, and the weak tropical cyclones have faster weakening rates than intensification rates. From 1977 to 2004, the annual mean values of R15 increase basically with year; during the 28-year period, the value of R15 increases by 52.7 kin, but R26 does not change with year obviously.

The upper ocean response to tropical cyclones in the northwestern Pacific analyzed with Argo data

A large number of autonomous profiling floats deployed in global oceans have provided abundant temperature and salinity profiles of the upper ocean. Many floats occasionally profile observations during the passage of tropical cyclones. These in-situ observations are valuable and useful in studying the ocean’s response to tropical cyclones, which are rarely observed due to harsh weather conditions. In this paper, the upper ocean response to the tropical cyclones in the northwestern Pacific during 2000–2005 is analyzed and discussed based on the data from Argo profiling floats. Results suggest that the passage of tropical cyclones caused the deepening of mixed layer depth (MLD), cooling of mixed layer temperature (MLT), and freshening of mixed layer salinity (MLS). The change in MLT is negatively correlated to wind speed. The cooling of the MLT extended for 50–150 km on the right side of the cyclone track. The change of MLS is almost symmetrical in distribution on both sides of the track, and the change of MLD is negatively correlated to pre-cyclone initial MLD.

Importance of Weighting for Multi-Variable Habitat Suitability Index Model: A Case Study of Winter- Spring Cohort of Ommastrephes bartramii in the Northwestern Pacific Ocean

Weighting values for different habitat variables used in multi-factor habitat suitability index (HSI) modeling reflect the relative influences of different variables on distribution of fish species. Using the winter-spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwestern Pacific Ocean as an example, we evaluated the impact of different weighting schemes on the HSI models based on sea surface temperature, gradient of sea surface temperature and sea surface height. We compared differences in predicted fishing effort and HSI values resulting from different weighting. The weighting for different habitat variables could greatly influence HSI modeling and should be carefully done based on their relative importance in influencing the resource spatial distribution. Weighting in a multi-factor HSI model should be further studied and optimization methods should be developed to improve forecasting squid spatial distributions.

Projections of ocean climate for northwestern Pacific Ocean

The long-term adjustment processes of atmosphere and ocean in response to gradually increased atmospheric CO2 concentration have been analyzed in 70 and 140 a integrations with NCAR fully-coupled climate system model (CSM). In these experiments the CO2 concentration has been increased to double and quadruples the initial concentration, respectively. After 70 a, at the time of CO2 doubling, the model predicts surface air temperature rises by 1.2 and 1.5 K for the globe and the northwestern Pacific Ocean, respectively. The behavior of the quadrupling run is similar: each global and regional mean surface air temperatures increase by 2.8 and 3.0 K at the time of CO2 quadrupling. From the experiments, surface air temperature changes in the northwestern Pacific Ocean will be more distinctive compared with the global average, mainly due to exceptionally large wanning and sea level change near the entrance of the Kuroshio extension.

Impact of the Pacific–Japan Teleconnection Pattern on July Sea Fog over the Northwestern Pacific: Interannual Variations and Global Warming Effect

The northwestern Pacific （NWP） is a fog-prone area, especially the ocean east of the Kuril Islands. The present study analyzes how the Pacific-Japan （PJ） teleconnection pattern influences July sea fog in the fog-prone area using independent datasets. The covariation between the PJ index and sea fog frequency （SFF） index in July indicates a close correlation, with a coefficient of 0.62 exceeding the 99% confidence level. Composite analysis based on the PJ index, a case study, and model analysis based on GFDL-ESM2M, show that in high PJ index years the convection over the east of the Philippines strengthens and then triggers a Rossby wave, which propagates northward to maintain an anticyclonic anomaly in the midlatitudes, indicating a northeastward shift of the NWP subtropical high. The anticyclonic anomaly facilitates the formation of relatively stable atmospheric stratification or even an inversion layer in the lower level of the troposphere, and strengthens the horizontal southerly moisture transportation from the tropical-subtropical oceans to the fog-prone area. On the other hand, a greater meridional SST gradient over the cold flank of the Kuroshio Extension, due to ocean downwelling, is produced by the anticyclonic wind stress anomaly. Both of these two aspects are favorable for the warm and humid air to cool, condense, and form fog droplets, when air masses cross the SST front. The opposite circumstances occur in low PJ index years, which are not conducive to the formation of sea fog. Finally, a multi-model ensemble mean projection reveals a prominent downward trend of the PJ index after the 2030s, implying a possible decline of the SFF in this period.

Modulation of Tropical Cyclone Activity Over the Northwestern Pacific Through the Quasi-Biweekly Oscillation

The quasi-biweekly oscillation(QBWO)is the second most dominant intraseasonal mode for circulation over the Northwestern Pacific(WNP)during boreal summer.In this study,we investigated how the QBWO modulates tropical cyclone(TC)activities over the WNP from dynamic and thermodynamic perspectives.The propagation of the QBWO can be divided into four phases through empirical orthogonal function analysis of the vorticity at 850 hPa,which was proven to be effective in extracting the QBWO signal.TC generation and landings are significantly enhanced during the active period(phases 1 and 2)relative to the inactive period(phases 3 and 4).Composite analyses show the QBWO could significantly modulate TC activity as it propagates northwestward by changing the atmospheric circulation at both high and low levels.Cumulus convection provides an important link between TCs and the QBWO.The major component of the atmosphere heat source is found to be the latent heat release of convection.The condensation latent heat centers,vertical circulation,and water vapor flux divergence cooperate well during different phases of the QBWO.The vertical profile of the condensation latent heat indicates upper-level heating(cooling)during the active(inactive)phases of the QBWO.Thus,the northwestward propagation of the QBWO can modulate TC activity by affecting the configuration of atmospheric heating over the WNP.

Three-dimensional characteristics of mesoscale eddies simulated by a regional model in the northwestern Pacific Ocean during 2000–2008

Mesoscale eddies play vital roles in ocean processes.Although previous studies focused on eddy surface features and individual three-dimensional(3D)eddy cases in the northwestern Pacific Ocean,the analysis of unique eddy3D regional characteristics is still lacking.A 3D eddy detection scheme is applied to 9 years(2000-2008)of eddyresolving Regional Ocean Modeling System(ROMS)output to obtain a 3D eddy dataset from the surface to a depth of 1000 m in the northwestern Pacific Ocean(15°-35°N,120°-145°E).The 3D characteristics of mesoscale eddies are analyzed in two regions,namely,Box1(Subtropical Countercurrent,15°-25°N,120°-145°E)and Box2(Southern Kuroshio Extension,25°-35°N,120°-145°E).In Box1,the current is characterized by strong vertical shear and weak horizontal shear.In Box2,the current is characterized by the strong Kuroshio,topographic effect,and the westward propagation of Rossby waves.The results indicate the importance of baroclinic instability in Box1,whereas in Box2,both the barotropic and baroclinic instability are important.Moreover,the mesoscale eddies’properties in Box1 and Box2 are distinct.The eddies in Box1 have larger number and radius but a shorter lifetime.By contrast,Box2 has fewer eddies,which have smaller radius but longer lifetime.Vertically,more eddies are detected at the subsurface than at the surface in both regions;the depth of 650 m is the turning point in Box1.Above this depth,the number of cyclonic eddies(CEs)is larger than that of anticyclonic eddies(AEs).In Box2,the number of CEs is dominant vertically.Eddy kinetic energy(EKE)and mean normalized relative vorticity in Box2are significantly higher than those in Box1.With increasing depth,the attenuation trend of EKE and relative vorticity of Box1 become greater than those of Box2.Furthermore,the upper ocean(about 300 m in depth)contains 68.6%of the eddies(instantaneous eddy).Only 16.6%of the eddies extend to 1000 m.In addition,about87%of the eddies are bowl-shaped eddies in the two regions.Only about 3%are cone-shaped eddies.With increasing depth of the eddies,the proportion of bowl-shaped eddies gradually decreases.Conversely,the coneand lens-shaped eddies are equal in number at 700-1000 m,accounting for about 30%each.Studying the 3D characteristics of eddies in two different regions of the northwestern Pacific Ocean is an important stepping stone for discussing the different eddy generation mechanisms.

A discussion on vertical profiles of dissolved Cu, Cd and Ni in the northwestern Pacific, south of Japan

Some of the results about vertical profile of heavy metals of seawater to the south of Japan in Oct. 1990 are presented and discussed in relation to the concentration of dissolved Cu, Cd and Ni to biogeochemical environments. It points out that the distribution of dissolved Cu is higher in surface water than that in/upper 500 m layer, and maxima value attains the 8. 2 n mol/dm3 in depth of 4 000 m. The concentrations of dissolved Ni ranges from 3. 4 n mol/dm3 in surface seawater to 8. 5 n mol/dm3 in the deep to the south of Japan. The highest values are observed in the colder waters. This paper shows also that the vertical profile of dissolved Cd is perfect nutrient-type distribution. And dissolved Cd and Phosphate are linearly correlated by the regression equation. The ·Cd : ·N : ·P atomic ratio is 3. 5 × 10-4 : 14 : 1.

A new species of the glass sponge genus Walteria(Hexactinellida:Lyssacinosida:Euplectellidae)from northwestern Pacific seamounts,providing a biogenic microhabitat in the deep sea

We report on a hexactinellid sponge new to science,Walteria demeterae sp.nov.,which was collected from the northwestern Pacific seamounts at depths of 1271–1703 m.Its tubular and basiphytous body,extensive lateral processes,numerous oval lateral oscula which are irregularly situated in the body wall,the presence of microscleres with oxyoidal,discoidal and onychoidal outer ends,and the absence of anchorate discohexasters,indicate it belongs to the genus Walteria of family Euplectellidae,which is also supported by molecular phylogenetic evidence from 18 S,28 S,16 S rRNA and cytochrome c oxidase subunit I(COI)gene sequences.The unique morphotype,which is structured by a thin and rigid framework of body wall and lateral processes consisting of diactins,characterizes it as a new species.Local aggregations of individuals of this new species coupled with their associated macrofauna in the Suda Seamount are reported,highlighting its functional significance in providing biogenic microhabitats in the deep sea.

Diagnostic Analyses and Numerical Modeling of Explosive Cyclone over Northwestern Pacific on January 11-13,2012

In this paper,we use FNL grid data obtained from the National Centers for Environmental Prediction(NCEP)to analyze an explosive cyclone(EC)that occurred over the northwestern Pacific Ocean from January 11 to 13,2012.To simulate the EC,we used the Weather Research and Forecasting model(WRFV3.5).The cyclone outbreak occurred east of Japan from January 11 to 12 and weakened near the Kamchatka Peninsula on January 13.The analysis results show a distinct frontal structure,in which the high potential vorticity(PV)of the upper troposphere extends downward to the surface,which can facilitate EC development.A low-level jet stream develops with the EC,which can lead to more distinct convergence.The results of sea surface temperature(SST)sensitivity tests suggest that changes in the SST can affect cyclone intensity,but have little effect on its path.When small changes are made to the SST,the air pressure at the cyclonic center responds more distinctly to an increased SST than a decreased SST.The results of our latent heat release test suggest that diabatic heating processes lead to maximum PV values in the lower troposphere.Latent heat is also one of the important factors influencing EC development.

Sea level anomalies in the northwestern Pacific during 2011 associated with La Nina and negative Indian Ocean Dipole

The sea level anomalies(SLAs)pattern in the northwestern Pacific delineated significant differences between La Ni?a events occurring with and without negative Indian Ocean Dipole(IOD)events.During the pure La Ni?a events,positive the sea surface level anomalies(SLAs)appear in the northwestern Pacific,but SLAs are weakened and negative SLAs appear in the northwestern Pacific under the contribution of the negative IOD events in 2010/2011.The negative IOD events can trigger significant westerly wind anomalies in the western tropical Pacific,which lead to the breakdown of the pronounced positive SLAs in the northwestern Pacific.Meanwhile,negative SLAs excited by the positive wind stress curl near the dateline propagated westward in the form of Rossby waves until it approached the western Pacific boundary in mid-2011,which maintained and enhanced the negative phase of SLAs in the northwestern Pacific and eventually,it could significantly influence the bifurcation and transport of the North Equatorial Current(NEC).

Abundance of total bacteria, ATP and manganese-oxidating bacteria in the sediments and manganese nodules of the Northwestern Pacific Ocean

In the seawater and sediments of the ocean, there exist huge quantities of bacteria whose living activities cause various chemical reaction processes. It is demonstrated that microorganisms play a fundamental role on chemical changes of the sediments and diageneses. Over the last twenty years, great interest has been increased about the role of deep-sea bacteria in the ferromanganese sedimentary process. Much work has been done on this aspect in the Atlantic Ocean, the Baltic Sea and the Pacific O-

Two interannual variability modes of the Northwestern Pacific Subtropical Anticyclone in boreal summer

Using the reanalysis data and 20th century simulation of coupled model FGOALS_gl developed by LASG/IAP, we identified two distinct interannual modes of Northwestern Pacific Subtropical Anticyclone （NWPAC） by performing Empirical Orthogonal Function （EOF） analysis on 850 hPa wind field over the northwestern Pacific in summer. Based on the associated anoma- lous equatorial zonal wind, these two modes are termed as ＂Equatorial Easterly related Mode＂ （EEM） and ＂Equatorial Westerly related Mode＂ （EWM）, respectively. The formation mechanisms of these two modes are similar, whereas the maintenance mechanisms, dominant periods, and the relationships with ENSO are different. The EEM is associated with E1 Nifio decaying phase, with the anomalous anticyclone established in the preceding winter and persisted into summer through local positive air-sea feedback. By enhancing equatorial upwelling of subsurface cold water, EEM favors the transition of ENSO from E1 Nifio to La Nifia. The EWM is accompanied by the E1 Nifio events with long persistence, with the anomalous anticyclone formed in spring and strengthened in summer due to the warm Sea Surface Temperature anomalies （SSTA） forcing from the equatorial central-eastern Pacific. The model well reproduces the spatial patterns of these two modes, but fails to simulate the percentage variance accounted for by the two modes. In the NCEP reanalysis （model result）, EEM （EWM） appears as the first mode, which accounts for 35.6% （68.2%） of the total variance.

THE EFFECT OF THE LONG WAVE OVER THE NORTHERN HEMISPHERE ON TYPHOON TRACKS OVER THE NORTHWESTERN PACIFIC

The normal typhoon paths with 109 cases during the period from 1960 to 1979 have been analysed in this study. These paths are divided into 7 categories. The effect of the position and intensity of large- scale wave on each category has been examined. It has been discovered, as a result, that this effect is rather evident. On the other hand, the teleconnection between different centers of anion does exist. A simple theoretical analysis indicates that the teleconnection is related to the propagation of wave energy. Thus, to predict correctly typhoon path, not only the steering flow of typhoon, but also, more significantly, the behavior of large-scale wave over the Northern Hemisphere must be taken into consideration.

POC fluxes from euphotic zone estimated from ^(234)Th deficiency in winter in the northwestern North Pacific Ocean

Dissolved and particulate 234 Th, particulate organic carbon(PON), nitrogen, and chlorophyll-a concentrations in the upper 200 m of water columns from seven stations in the northwestern North Pacific Ocean were determined in the winter of 1997.The dissolved, particulate, and total 234 Th activities (dissolved plus particulate)show a pronounced deficiency with respect to its parent 238 U in the euphotic zone whereas the total 234 Th shows a near-equilibrium at the depth greater than 100 m.The 234 Th data are used to derive the mean residence time, export fluxes of 234 Th, and fluxes of particulate organic carbon and nitrogen out of the euphotic zone. In the Subarctic Current area, the residence time of dissolved 234 Th with respect to its removal onto particles is 40 ~50 d while the residence time of dissolved 234Th in the subtropical area is about 20 d due to the Kuroshio's influence.The particulate organic carbon(POC)and particulate organic nitroge(PON)fluxes in winter range over 3.8～8.2 and 0.50～0.98 mmol/(m2 ·d), respectively, and are higher in the west region than in the east, and higher in the south than in the north. The co-influence of Kuroshio-Oyashio Currents with supply of nutrient substances from the coastal area and the light condition are two factors determining the horizontal distribution of POC fluxes in winter.The depth distribution of the chlorophyll-a as well as the consistence of the ratio of POC to PON with the Redfield ratio suggest that phytoplankton is the main contributor to the export of POC in this area in winter.The POC fluxes in the northwestern North Pacific Ocean in winter are comparable to some areas in the world oceans in spring and summer seasons.

Unveiling controls of the latitudinal gradient of surface pCO_(2) in the Kuroshio Extension and its recirculation regions(northwestern North Pacific)in late spring

In the northwestern North Pacific,annual net air-sea CO_(2) flux is greatest in the Kuroshio Extension(KE)zone,owing to its low annual mean partial pressure of CO_(2)(pCO_(2)),and it decreases southward across the basin.To quantify the influences of factors controlling the latitudinal gradient in CO_(2) uptake,sea surface pCO_(2) and related parameters were investigated in late spring of 2018 in a study spanning the KE,Kuroshio Recirculation(KR),and subtropical zones.We found that the sea-to-air pCO_(2) difference(ΔpCO_(2))was negative and at its lowest in the KE zone.ΔpCO_(2) gradually increased southward across the KR zone,and the sea surface was nearly in air-equilibrium with atmospheric CO_(2) in the subtropical zone.We found that northward cooling and vertical mixing were the two major processes governing the latitudinal gradient in surface pCO_(2) and ΔpCO_(2),while biological influences were relatively minor.In the KE zone affected by upwelling,the vertical-mixing-induced increase in surface pCO_(2) likely canceled out approximately 61%of the decrease in surface pCO_(2) caused by cooling and biological activities.Moreover,the prolonged air-sea equilibration for CO_(2) and relatively short hydraulic retention time jointly led to the low surface pCO_(2) in the KE zone in spring.Ultimately,the cooling KE current flows out of the region before it can be re-equilibrated with atmospheric CO_(2).

Standardizing CPUE of Ommastrephes bartramii for Chinese squid-jigging fishery in Northwest Pacific Ocean

Generalized linear models （GLM） and generalized additive models （GAM） were used to standardize catch per unit fishing effort （CPUE） of Ommastrephes bartramii for Chinese squid-jigging fishery in Northwest Pacific Ocean. Three groups of variables were considered in the standardization： spatial variables （longitude and latitude）, temporal variables （year and month） and environmental variables, including sea surface temperature （SST）, sea surface salinity （SSS） and sea level height （SLH）. CPUE was treated as the dependent variable and its error distribution was assumed to be log-normal in each model. The model selections of GLM and GAM were based on the finite sample-corrected Akaike information criterion （AICC） and pseudo-coefficient （Pcf） combined P-value, respectively. Both GAM and GLM analysis showed that the month was the most important variable affecting CPUE and could explain 21.3% of variability in CPUE while other variables only explained 8.66%. The interaction of spatial and temporal variables weakly influenced the CPUE. Moreover, spatio-temporal factors may be more important in influencing the CPUE of this squid than environmental variables. The standardized and nominal CPUEs were similar and had the same trends in spatio-temporal distribution, but the standardized CPUE values tended to be smaller than the nominal CPUE. The CPUE tended to have much higher monthly variation than annual variations and their values increased with month. The CPUE became higher with increasing latitude-high CPUE usually occurred in 145°E-148°E and 149°E-162°E. The CPUE was higher when SST was 14-21℃ and the SLH from -22 cm to -18 cm. In this study, GAM tended to be more suitable than GLM in analysis of CPUE.

Analysis of the Anomalous Strength and Location of the ITCZ Affecting the Formation of Northern Pacific Typhoons

Using the NCEP/NCAR reanalysis dataset from 1959-2004, the location and strength of the ITCZ （Inter-Tropical Convergence Zone）, as well as their relations with typhoons in the northwestern Pacific were studied. It was found that the pentad location and strength of the ITCZ had close relations with the typhoon frequency. Higher latitude location or strengthened ITCZ were found to be favorable for the occurrence of typhoons over the Northwestern Pacific. An index was defined for ascertaining the location of the ITCZ. It was found that the index defined with the maximum value of pentad and monthly meridional shear of zonal wind speed could better describe the location of ITCZ than another index defined with the maximum value of convergence. Correlation analysis between the index of ITCZ and the maximum cloud cover in the tropics showed that there were close relations between the ITCZ determined by the index and the maximum tropical cloud belt. The strength index of an ITCZ was defined as the zonal wind speed difference at latitudes south and north of the ITCZ. It was found that there are close relations between the ITCZ intensity and typhoon occurrence in the South China Sea [10°N-20°N, 100°E-120°E] and regions east of the Philippines and near the Mariana Islands[5°N-20°N, 127.5°-150°E].

Variation in Principal Modes of Midsummer Precipitation over Northeast China and Its Associated Atmospheric Circulation

This study documents the first two principal modes of interannual variability of midsummer precipitation over Northeast China （NEC） and their associated atmospheric circulation anomalies. It is shown that the first principal mode exhibits the largest amount of variability in precipitation over the south of NEC （referred to as the south mode）, whereas the second principal mode behaves with the greatest precipitation anomaly over the north of NEC （referred to as the north mode）. Further findings reveal that, through modulating moisture transportation and upper- and lower-troposphere divergence circulation as well as vertical movement over NEC, the anomalous northwestern Pacific anticyclone and the anticyclone centered over northern NEC exert the dominant influence on the south and north modes, respectively. Additionally, it is quantitatively estimated that water vapor across the southern boundary of NEC dominates the moisture budget for the south mode, while the north mode has a close connection with moisture through NEC＇s northern and western boundal＇ies. Furthermore, the north （south） mode is strongly related to the intensity （meridional shift） of the East Asian westerly jet.