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 Con-vergence Zone), as well as their relations with typhoons in the northwestern Pacific were studied. It was found that the pentad loca-tion 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 loca-tion of the ITCZ. It was found that the index defined with the maximum value ofpentad 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°E-150°E].     

Tropical pacific decadal variability in subsurface temperature

The nature decadal variability of the equatorial Pacific subsurface temperature is examined in the control simulation with the Geophysical Fluid Dynamics Laboratory coupled model CM2.1.The dominant mode of the subsurface temperature variations in the equator Pacific features a 20-40 year period and is North-South asymmetric about the equator.Decadal variations of the thermocline are most pronounced in the southwest of the Tropical Pacific.Decadal variation of the north-south asymmetric Sea Surface wind in the tropical Pacific,especially in the South Pacific Convergence,is the dominant mechanism of the nature decadal variation of the subsurface temperature in the equatorial Pacific.     

Events of decadal thermocline variations in the South Pacific Ocean

1 INTRODUCTION It has been suggested that interior thermal anomalies that subduct into the subtropics of the North Pacific may propagate to the equatorial region of the Pacific (Russell, 1994; Deser et al., 1996; Gu and Philander, 1997; Huang and Huang an…     

Difference in the influence of Indo-Pacific Ocean heat content on South Asian Summer Monsoon intensity before and after 1976/1977

Monthly ocean temperature from ORAS4 datasets and atmospheric data from NCEP/NCAR Reanalysis I/II were used to analyze the relationship between the intensity of the South Asian summer monsoon(SASM) and upper ocean heat content(HC) in the tropical Indo-Pacific Ocean.The monsoon was differentiated into a Southwest Asian Summer Monsoon(SWASM)(2.5°–20°N,35°–70°E) and Southeast Asian Summer Monsoon(SEASM)(2.5°–20°N,70°–110°E).Results show that before the 1976/77 climate shift,the SWASM was strongly related to HC in the southern Indian Ocean and tropical Pacific Ocean.The southern Indian Ocean affected SWASM by altering the pressure gradient between southern Africa and the northern Indian Ocean and by enhancing the Somali cross-equatorial flow.The tropical Pacific impacted the SWASM through the remote forcing of ENSO.After the 1976/77 shift,there was a close relationship between equatorial central Pacific HC and the SEASM.However,before that shift,their relationship was weak.     

Interdecadal variability of the South China Sea monsoon and its relationship with latent heat flux in the Pacific Ocean

We analyzed interdecadal variability of the South China Sea monsoon and its relationship with latent heat flux in the Pacific Ocean, using NCEP wind field and OAFlux heat flux datasets. Results indicate that South China Sea monsoon intensity had an obvious interdecadal variation with a decreasing trend. Variability of the monsoon was significantly correlated with latent heat flux in the Kuroshio area and tropical Pacific Ocean. Variability of latent heat flux in the Kuroshio area had an interdecadal increasing trend, while that in the tropical Pacific Ocean had an interdecadal decreasing trend. Latent heat flux variability in these two sea areas was used to establish a latent heat flux index, which had positive correlation with variability of the South China Sea monsoon. When the latent heat flux was 18 months ahead of the South China Sea monsoon, the correlation coefficient maximized at 0.58 (N=612), with a 99.9% significance level of 0.15. Thus, it is suggested that latent heat flux variability in the two areas contributes greatly to interdecadal variability of the South China Sea monsoon.     

Diatom assemblages in surface sediments from the South China Sea as environmental indicators

We studied diatom distribution from 62 samples from the uppermost 1 cm of sediment in the South China Sea (SCS), using grabs or box corers in three cruises between 2001–2007. Fifty six genera, 256 species and their varieties were identified. Dominating species included Coscinodiscus africanus, Coscinodiscus nodulifer, Cyclotella stylorum, Hemidiscus cuneiformis, Melosira sulcata, Nitzschia marina, Roperia tesselata, Thalassionema nitzschioides, Thalassiosira excentrica, and Thalassiothrix longissima. Most surface sediments in the SCS were rich in diatoms, except for a few coarse samples. Average diatom abundance in the study area was 104 607 valve/g. In terms of the abundance, ecology, and spatial distribution, seven diatom zones (Zones 1–7) were recognized. Zone 1 (northern continental shelf) is affected by warm currents, SCS northern branch of the Kuroshio, and northern coastal currents; Zone 2 (northwestern continental shelf) is affected by intense coastal currents; Zone 3 (Xisha Islands sea area) is a bathyal environment with transitional water masses; Zone 4 (sea basin) is a bathyal-to-deep sea with stable and uniform central water masses in a semi-enclosed marginal sea; Zone 5 (Nansha Islands marine area) is a pelagic environment with relatively high surface temperature; Zone 6 (northern Sunda Shelf) is a tropical shelf environment; and Zone 7 (northern Kalimantan Island shelf area) is affected by warm waters from the Indian Ocean and coastal waters. The data indicate that these diatom zones are closely related to topography, hydrodynamics, temperature, nutrients and especially the salinity. Better understanding of the relationship between diatom distribution and the oceanographic factors would help in the reconstruction of the SCS in the past.     

“海上丝绸之路”主要海域热带气旋时空分布特征及其危险性

热带气旋作为一种海上灾害性天气,对“海上丝绸之路”海上航运影响重大。本文基于西北太平洋和北印度洋1990—2017年的热带气旋路径数据,结合热带气旋风场参数模型,利用缓冲区分析、叠加分析等GIS空间分析技术,系统研究了“海上丝绸之路”主要海域、主要海区、关键通道受热带气旋影响频次以及热带气旋危险性的时空分布特征。主要结论：① “海上丝绸之路”主要海域受热带气旋影响严重,表现在热带气旋影响范围广、影响频次高,其中西北太平洋较北印度洋受热带气旋影响更为严重,危险性更大;② 西北太平洋的15°N—30°N,120°E-—145°E海域热带气旋危险性最高;③ 热带气旋危险性季节变化较为明显,秋夏两季危险性较高,冬春两季危险性较低,在夏秋两季各月份中,7、8、9、10月危险最高;④ 在各海区中,中国东部海区热带气旋危险最高,其次是南海、日本海、孟加拉湾、阿拉伯海,而红海和波斯湾不受热带气旋影响;在各关键通道中,吕宋海峡热带气旋危险性最高,其次是台湾海峡、对马海峡、宗谷海峡、鞑靼海峡、保克海峡、霍尔木兹海峡,而马六甲海峡和曼德海峡无热带气旋危险。     

热带次表层海温对中国东部夏季气候的影响

热带海洋热状况是影响中国气候变化的主要因子之一,为了研究热带次表层海温如何影响中国气候,通过相关计算和合成分析等方法讨论了热带太平洋至印度洋次表层海温异常对中国东部夏季降水和温度的影响。结果表明:当冬季赤道东印度洋至西太平洋次表层海温偏暖(偏冷),中印度洋和东太平洋次表层海温偏冷(偏暖),夏季,长江中下游地区降水偏少(偏多),华南、华北和东北大部地区降水偏多(偏少);中国东部大范围高温(低温)。其可能的影响途径为,东亚夏季风环流对热带次表层海温异常的响应导致了其年际变化,进而引起中国东部夏季气候的异常分布。     

Seasonal variability of zonal heat advection in the mixed layer of the tropical Pacific

Zonal heat advection （ZHA） plays an important role in the variability of the thermal structure in the tropical Pacific Ocean, especially in the western Pacific warm pool （WPWP）. Using the Simple Ocean Data Assimilation （SODA） Version 2.02/4 for the period 1958-2007, this paper presents a detailed analysis of the climatological and seasonal ZHA in the tropical Pacific Ocean. Climatologically, ZHA shows a zonal- band spatial pattern associated with equatorial currents and contributes to forming the irregular eastern boundary of the WPWP （EBWP）. Seasonal variation of ZHA with a positive peak from February to July is most prominent in the Nifio3.4 region, where the EBWP is located. The physical mechanism of the seasonal cycle in this region is examined. The mean advection of anomalous temperature, anomalous advection of mean temperature and eddy advection account for 31%, 51%, and 18% of the total seasonal variations, respectively. This suggests that seasonal changes of the South Equatorial Current induced by variability of the trade winds are the dominant contributor to the anomalous advection of mean temperature and hence, the seasonality of ZHA. Heat budget analysis shows that ZHA and surface heat flux make comparable contributions to the seasonal heat variation in the Nifio3.4 region, and that ZHA cools the upper ocean throughout the calendar year except in late boreal spring. The connection between ZHA and EBWP is further explored and a statistical relationship between EBWP, ZHA and surface heat flux is established based on least squares fitting.     

Anomalies of asian summer monsoon related to ssta in the south China Sea and the tropical pacific

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＳｏｕｔｈＣｈｉｎａＳｅａ(ＳＣＳ)ｉｓａｐａｒｔｌｙ ｅｎｃｌｏｓｅｄｏｃｅａｎｂａｓｉｎｏｖｅｒｌａｉｄｂｙａｐｒｏｎｏｕｎｃｅｄｍｏｎｓｏｏｎｓｕｒｆａｃｅｗｉｎｄ .Ｐａｓｔｓｔｕｄｉｅｓ (Ｃｈｅｎｅｔａｌ.,1 991 ;ＤｉｎｇａｎｄＭｕｒａｋａｍｉ,1 994 ;Ｙａｎ ,1 997;ＬｉａｎｇＢｉｑｉ,1 991 ;ＬｉａｎｇＪｉａｎｙｉｎ ,1 991 )ｉｎｄｉｃａｔｅｔｈａｔａｈｕｇｅｗａｒｍｗａｔｅｒｐｏｏｌｊｏｉｎｔｌｙｃｏｎｔｒｉｂｕｔｅｄｂｙｔｈｅｗｅｓｔｅｒｎＰａｃｉｆｉｃ ,ｅａ…     

The increased storage of suspended particulate matter in the upper water of the tropical Western Pacific during the 2015/2016 super El Ni?o event

The climate variability induced by the El Ni?o-Southern Oscillation(ENSO) cycle drives significant changes in the physical state of the tropical Western Pacific,which has important impacts on the upper ocean carbon cycle.During 2015-2016,a super El Ni?o event occurred in the equatorial Pacific.Suspended particulate matter(SPM) data and related environmental observations in the tropical Western Pacific were obtained during two cruses in Dec.2014 and 2015,which coincided with the early and peak stages of this super El Ni?o event.Compared with the marine environments in the tropical Western Pacific in Dec.2014,an obviously enhanced upwelling occurred in the Mindanao Dome region;the nitrate concentration in the euphotic zone almo st tripled;and the size,mass concentration,and volume concentration of SPM obviously increased in Dec.2015.The enhanced upwelling in the Mindanao Dome region carried cold but eutrophic water upward from the deep ocean to shallow depths,even into the euphotic zone,which disrupted the previously N-limited conditions and induced a remarkable increase in phytoplankton blooms in the euphotic zone.The se results reveal the mechanism of how nutrient-limited ecosystems in the tropical Western Pacific respond to super El Ni?o events.In the context of the ENSO cycle,if predicted changes in biogenic particles occur,the proportion of carbon storage in the tropical Western Pacific is estimated to be increased by more than 52%,ultimately affecting the regional and possibly even global carbon cycle.This paper highlights the prospect for long-term prediction of the impact of a super El Ni?o event on the global carbon cycle and has profound implications for understanding El Ni?o events.     

Influence of temperature and frequency on microwave dielectric properties of lunar regolith simulant

The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.     

MODIS_LST与AMSR-E_BT的相关性及地表温度反演

本文以2007年和2008年MODIS每日地表温度（LST）数据及AMSR-E地表亮温（BT）数据为研究对象,结合土地覆盖类型数据,统计分析MODIS_LST与AMSR-E_BT在不同土地覆盖类型、频率和极化方式条件下的相关性。结果表明,频率在18.7、23.8和36.5 GHz的AMSR-E-BT与MODIS_LST的相关性较大,且在垂直极化通道上的相关性较在水平极化上大;不同土地覆盖类型,与MODIS_LST相关性较大所对应的AMSR-E微波通道不同。同时,考虑混合像元问题对相关性的影响,对25种不同地物类型组合下MODIS_LST与AMSR-E-BT的相关性进行统计分析,发现混合像元中地物类型越多,则二者相关性越小。最后,采用多元线性回归分析法,根据不同土地覆盖类型建立反演回归模型,对部分研究区域MODIS-LST进行反演,误差平均在±3.15 K以内,与不考虑下垫面覆盖的模型比较,反演MODIS_LST精度平均提高了1.5 K。     

The link between interannual variation of the South China Sea summer monsoon onset and summer precipitation in Shandong Province

Relationship between the onset date of South China Sea (SCS) summer monsoon and the summer rainfall in Shandong Province was examined by comprehensive analysis to establish a conceptual model of the link. If the summer monsoon occurs earlier, the 500 hPa level would induce the teleconnection of Eurasian pattern in the summer (June-August), which indicates that the western Pacific subtropical high is displaced northward further than usual, the Siberian high is intensified and the Okhotsk low is deepened. Under such circumstance, Shandong, located in the west side of the subtropical high and in front of the mid-Siberia high, would be expected to have a wet summer because it is quite possible for cold and warm air to meet and interact with each other in Shandong. Statistical analysis revealed that the 500 hPa anomalies over Korea and Japan were sensitive to the SCS monsoon onset date and very important to precipitation in Shandong, and that the convective activities over the deep water basin in the SCS in 24-26 pentads significantly influenced the position of the ridge line of the western Pacific subtropical high. These findings yielded better understanding of the causative mechanisms involved in the precipitation generation, so that the knowledge gained can possibly be applied for long-lead forecast.     

Characteristics of water exchange in the Luzon Strait during September 2006

The Luzon Strait is the only deep channel that connects the South China Sea(SCS) with the Pacific.The transport through the Luzon Strait is an important process influencing the circulation,heat and water budgets of the SCS.Early observations have suggested that water enters the SCS in winter but water inflow or outflow in summer is quite controversial.On the basis of hydrographic measurements from CTD along 120° E in the Luzon Strait during the period from September 18 to 20 in 2006,the characteristics of t...     

Brightness Temperature Model of Sea Foam Layer at L-band

Permittivity of a sea foam layer is very important in investigating ocean brightness temperature model. At microwave frequency, the Rayleigh method is developed to estimate the effective permittivity of the sea foam layer. To simplify the tedious calculation of sea foam effective permittivity at L band(1.4 GHz), Pade’ approximation is adopted to fit the sea foam effective permittivity computed by the Rayleigh method. With this fitting formula, a new brightness temperature model of sea foam layer defined by certain geophysical parameters, such as air volume fraction(AVF), sea surface temperature(SST), sea surface salinity(SSS) and thickness of foam layer d, is given. Furthermore, the sensitivities of the brightness temperature model to SST, SSS, d and AVF of a sea foam layer at L band are discussed. The sensitivities are ranked from most to least in the order:(1) d;(2) AVF;(3) SSS;(4) SST. This result indicates that the measurement errors of d and AVF have significant impacts on the retrievals of SSS and SST. With the experimental brightness temperature data, the SSS and AFV are retrieved by cost function.     

Characteristics of change of the SST in the tropical western Pacific and the tropical Indian Ocean and its response to the change of the Antarctic ice area

In this paper, by using ocean surface temperature data (COADS), the study is made of the characteristics of the monthly and annual changes of the SST in the tropical western Pacific and Indian Oceans, which have important influences on the climate change of the whole globe and the relation between ENSO(E1 Nino-Southern Oscillation) and the Antarctic ice area is also discussed. The result indicates that in the tropical western Pacific and the Indian Oceans the change of Sea Surface Temperture (SST) is conspicuous both monthly and armaully, and shows different change tendency between them. This result may be due to different relation in the vibration period of SST between the two Oceans. The better corresponding relationship is obvious in the annual change of SST in the tropical Indian Ocean with the occurrence El Nino and LaNlra. The change of the SST in the tropical western Pacific and the tropical Indian Oceans has a close relation to the Antarctic ice area, especially to the ice areas in the eastern-south Pole and Ross Sea, and its notable correlative relationship appears in 16 months when the SST of the tropical western Pacific and the Indian Oceans lag back the Antarctic ice area.     

A NUMERICAL STUDY OF THE TIDE-SURGE INTERACTION IN THE EAST CHINA SEA AND THE SOUTH CHINA SEA

Nearshore sea levels in the East China Sea(ECS) and the South China Sea(SCS) during tropical cyclones-Typhoon 8007(Joe, 1980) and Typhoon 7209(Betty 1972) were simulated. The tide-surge interactions in the two regions are remarkable and locally produced. The corresponding nonlinear effects were derived from the different nonlinear terms. The contribution of the quadratic friction term is the most important, the shallow term comes second the convective term is the least; the phases of the interactions generated by the various nonlinear terms are asynchronous. Both the quadratic friction and the convective term can stimulate and aggravate the surge structure with more peaks. The bottom friction features have crucial influences on tides and surges, and the interaction is sensitive to the changes of tide and surge.     

Modulation of tropical cyclogenesis over the South China Sea by ENSO Modoki during boreal summer

This study examines the modulation of tropical cyclogenesis over the South China Sea(SCS) by the El Nio-Southern Oscillation(ENSO) Modoki during the boreal summer. Results reveal that there were more tropical cyclones(TCs) formed over the SCS during central Pacific warming years and less TC frequency during central Pacific cooling years. How different environmental factors(including low-level relative vorticity, mid-level relative humidity, vertical wind shear, and potential intensity) contribute to this influence is investigated, using a genesis potential(GP) index developed by Emanuel and Nolan. Composite anomalies of the GP index are produced for central Pacific warming and cooling years separately, which could account for the changes of TC frequency over the SCS in different ENSO Modoki phases. The degree of contribution by each factor is determined quantitatively by producing composites of modified indices in which only one of the contributing factors varies, with the others set to climatology. The results suggest that the vertical wind shear and low-level relative vorticity, which are associated with the ENSO Modoki-induced anomalous circulations in Matsuno-Gill patterns, make the largest contributions to the ENSO Modoki modulation of tropical cyclogenesis over the SCS as implied by the GP index. These results highlight the important roles of dynamic factors in the modulation of TC frequency over the SCS by the ENSO Modoki during the boreal summer.     

Subtropical air-sea interaction and development of central Pacific El Niño

The standard deviation of the central Pacific sea surface temperature anomaly (SSTA) during the period from October to February shows that the central Pacific SSTA variation is primarily due to the occurrence of the Central Pacific El Nio (CP-El Nio) and has a connection with the subtropical air-sea interaction in the northeastern Pacific. After removing the influence of the Eastern Pacific El Nio, an S-EOF analysis is conducted and the leading mode shows a clear seasonal SSTA evolving from the subtropical northeastern Pacific to the tropical central Pacific with a quasi-biennial period. The initial subtropical SSTA is generated by the wind speed decrease and surface heat flux increase due to a north Pacific anomalous cyclone. Such subtropical SSTA can further influence the establishment of the SSTA in the tropical central Pacific via the wind-evaporation-SST (WES) feedback. After established, the central equatorial Pacific SSTA can be strengthened by the zonal advective feedback and thermocline feedback, and develop into CP-El Nio. However, as the thermocline feedback increases the SSTA cooling after the mature phase, the heat flux loss and the re-versed zonal advective feedback can cause the phase transition of CP-El Nio. Along with the wind stress variability, the recharge (discharge) process occurs in the central (eastern) equatorial Pacific and such a process causes the phase consistency between the thermocline depth and SST anomalies, which presents a contrast to the original recharge/discharge theory.