The Relationship Between Indian Ocean SST and Tropical Cyclone Genesis Frequency over North Indian Ocean in May

Tropical cyclone(TC)activities in the North Indian Ocean(NIO)peak in May during the pre-monsoon period,but the TC frequency shows obvious inter-annual variations.By conducting statistical analysis and dynamic diagnosis of long-term data from 1948 to 2016,the relationship between the inter-annual variations of Indian Ocean SST and NIO TC genesis frequency in May is analyzed in this paper.Furthermore,the potential mechanism concerning the effect of SST anomaly on TC frequency is also investigated.The findings are as follows:1)there is a broadly consistent negative correlation between NIO TC frequency in May and SST in the Indian Ocean from March to May,with the key influencing area located in the southwestern Indian Ocean(SWIO);2)the anomalies of SST in SWIO(SWIO-SST)are closely related to a teleconnection pattern surrounding the Indian Ocean,which can significantly modulate the high-level divergence,mid-level vertical motion and other related environmental factors and ultimately influence the formation of TCs over the NIO;3)the increasing trend of SWIO-SST may play an essential role in the downward trend of NIO TC frequency over the past 69 years.

New discovery of seafloor hydrothermal activity on the Indian Ocean Carlsberg Ridge and Southern North Atlantic Ridge-progress during the 26th Chinese COMRA cruise

The 26th Chinese COMRA （China Ocean Mineral Resources Research ＆ Development Association） cruise was an important cruise. The Carlsberg Ridge （CR） of the Northwest Indian Ocean and the North Atlantic Ridge （NAR）, in which less investigation has been carried out for hydrothermal activities, were investigated and studied during the first two legs of the 26th COMRA cruise. During the first leg, we found one hydrother- mal activity field located in the CR at 3.5^-3.8~ N on the Northwest Indian Ocean Ridge （NWIR）, and sampled seafloor polymetallic sulfide deposits where only abnormalities were found before. During the second leg, we found a new hydrothermal anomaly field located in the NAR at 4^-7~N. The discovery of two hydrother- real and anomaly fields filled in the gap of hydrothermal investigation and study in the corresponding re- ~ions for China.

Teleconnection Patterns along the Asian Jet Associated with Different Combinations of Convection Oscillations over the Indian Continent and Western North Pacific during Summer

A zonal teleconnection has been found along the Asian jet over the Eurasian continent during summer. In this study, the authors investigated circulation anomalies in the extratropics, in particular for the zonal teleconnection, under different combinations of subtropical convection anomalies over the northern Indian continent （IND） and the westem North Pacific （WNP）. The outof-phase configuration （i.e., stronger （weaker） IND convection and weaker （stronger） WNP convection） was found to be more common than the in-phase configuration （i.e., stronger （weaker） IND convection and stronger （weaker） WNP convection）, which is consistent with previous results. Composite results indicated that circulation anomalies for out-of-phase configurations of 30-60-day convection oscillations are much stronger in the middle latitudes than those for in-phase configurations. In addition, zonal teleconnection patterns are predominant for the out-of-phase configurations, particularly for the configuration of strong IND convection and weak WNP convec- tion; however, they are either weak or obscure for the in-phase configurations. These results suggest that the zonal teleconnection pattem along the Asian jet is dependent on different combinations of the 1ND and WNP subtropical convection anomalies.

Statistical characteristics and mechanisms of mesoscale eddies in the North Indian Ocean

The statistical characteristics and mechanisms of mesoscale eddies in the North Indian Ocean are investigated by adopting multi-sensor satellite data from 1993 to 2019.In the Arabian Sea(AS),seasonal variation of eddy characteristics is remarkable,while the intraseasonal variability caused by planetary waves is crucial in the Bay of Bengal(BOB).Seasonal variation of the eddy kinetic energy(EKE)is distinct along the west boundary of AS,especially in the Somali Current region.In the BOB,larger EKE occurs at the northwest basin from March to May,to the east of Sri Lanka from June to September,and along the east coast of India from November to December.The wind stress work(WW)is further studied to figure out the direct influence of wind forcing on EKE.The WW exerts positive effects on EKE along the west boundary of AS and in the south of India/Sri Lanka during the two monsoon seasons.Besides,the WW also has impact on EKE along the east coast of India in November and December.Eventually,we investigate the characteristics and the driving mechanisms of long lifespan eddies.In the AS,long lifespan anti-cyclonic eddies(AEs)mainly generate in the Socotra,the West Indian Coastal Current and the East Arabian Current regions,while cyclonic eddies(CEs)are concentrated in the northwest region.In the BOB,long lifespan AEs mostly form near the west of Myanmar,while CEs are accumulated at the north and northwest basin.The instabilities caused by Rossby waves,coastal Kelvin waves,seasonal currents,together with wind stress forcing exert enormous efforts on the generation and evolution of these eddies.

Contrasting the Indian and western North Pacific summer monsoons in terms of their intensity of interannual variability and biennial relationship with ENSO

The intensity of interannual variability(IIV)of the monsoon and monsoon–ENSO biennial relationship(MEBR)were examined and compared for both the Indian summer monsoon(ISM)and western North Pacific summer monsoon(WNPSM)during 1958–2018.Covariability of the IIV and MEBR were identified for the two monsoons.When the MEBR was strong(weak),the IIV of the monsoon was observed to be large(small).This rule applied to both the ISM and WNPSM.Out-ofphase relationships were found between the ISM and the WNPSM.When the IIV and MEBR of the ISM were strong(weak),those of the WNPSM tended to be weak(strong).During the period with a stronger(weaker)ENSO–Atlantic coupling after(before)the mid-1980 s,the IIV and MEBR of the WNPSM(ISM)were observed to be stronger.The increasing influences from the tropical Atlantic sea surface temperature(SST)may trigger the observed seesaw pattern of the ISM and WNPSM in terms of the IIV and MEBR multidecadal variability.The results imply that tropical Atlantic SST may need to be given more attention and consideration when predicting future monsoon variability of the ISM and WNPSM.

The Oscillation between Tropical Indian Ocean and North Pacific:Evidence and Possible Impact on Winter Climate in China

This paper provides evidence that the variation of boreal winter sea level pressure (SLP) over the North Pacific is out-of-phase with SLP fluctuation over the tropical Indian Ocean on both the interdecadal and interannual time scales.Subsequently,a SLP between tropical Indian Ocean and North Pacific (TIO-NP) oscillation index is defined to indicate the variation of such out-of-phase fluctuation.Moreover,the simultaneous surface air temperature and precipitation anomalies in China are closely related to TIO-NP oscillations.Below-normal surface air temperature anomalies in the northern and the eastern part of China,and less rainfall in southern China,correspond to positive TIO-NP oscillation phase with negative SLP anomalies in tropical Indian Ocean and positive anomalies in North Pacific.The TIO-NP oscillation affects China's winter climate anomalies,possibly through modulating the northeast East Asia winter monsoon.

Observed Relationship between Surface Freshwater Flux and Salinity in The North Indian Ocean

Using 10-year (2001 10) monthly evaporation, precipitation, and sea surface salinity (SSS) datasets, the relationship between local freshwater flux and SSS in the north Indian Ocean (NIO) is evaluated quantitatively. The results suggest a highly positive linear correlation between freshwater flux and SSS in the Arabian Sea (correlation coefficient, R=0.74) and the western equatorial Indian Ocean (R=0.73), whereas the linear relationships are relatively weaker in the Bay of Bengal (R=0.50) and the eastern equatorial Indian Ocean (R=0.40). Additionally, the interannual variations of freshwater flux and SSS and their mutual relationship are investigated in four sub- regions for pre-monsoon, monsoon, and post-monsoon seasons separately. The satellite retrievals of SSS from the Soil Moisture and Ocean Salinity (SMOS) and Aquarius missions can provide continuous and consistent SSS fields for a better understanding of its variability and the differences between the freshwater flux and SSS signals, which are commonly thought to be linearly related.

Prediction and mechanistic analysis of May precipitation in North China based on April Indian Ocean SST and the Northwest Pacific Dipole

North China May precipitation(NCMP)accounts for a relatively small percentage of annual total precipitation in North China,but its climate variability is large and it has an important impact on the regional climate and agricultural production in North China.Based on observed and reanalysis data from 1979 to 2021,a significant relationship between NCMP and both the April Indian Ocean sea surface temperature(IOSST)and Northwest Pacific Dipole(NWPD)was found,indicating that there may be a link between them.This link,and the possible physical mechanisms by which the IOSST and NWPD in April affect NCMP anomalies,are discussed.Results show that positive(negative)IOSST and NWPD anomalies in April can enhance(weaken)the water vapor transport from the Indian Ocean and Northwest Pacific to North China by influencing the related atmospheric circulation,and thus enhance(weaken)the May precipitation in North China.Accordingly,an NCMP prediction model based on April IOSST and NWPD is established.The model can predict the annual NCMP anomalies effectively,indicating it has the potential to be applied in operational climate prediction.

Correlations between the North China Craton and the Indian Shield:Constraints from regional metallogeny

The correlation between the North China Craton（NCC） and the Indian Shield（IND） has been a hot topic in recent years,On the basis of ore deposit databases,the NCC and IND have shown broad similarity in metallogenesis from the middle Archaean to the Mesoproterozoic,The two blocks both have three major metallogenic systems：（1） the Archaean BIF metallogenic system;（2） the Paleoproterozoic Cu-Pb-Zn metallogenic system;and（3） the Mesoproterozoic Fe-Pb-Zn system,In the north margin of the NCC and the west margin of the IND,the Archaean BIF-Au-Cu-Pb-Zn deposits had the same petrogenesis and host rocks,the Paleoproterozoic Cu-Pb-Zn deposits were controlled by active belts,and the Mesoproterozoic Fe-Pb-Zn deposits were mainly related to multi-stage rifting,Matching regional mineralization patterns and geological features has established the continental assembly referred to as ＂NCWI＂,an acronym for the north margin of the NCC（NC） and the west margin of the IND（WI） during the middle Archaean to the Mesoproterozoic,In this assembly,the available geological and metallogenic data from the Eastern Block and active belts of NC fit those from the Dharwar craton and the Aravalli-DelhiVindhyan belt of WI,respectively,Moreover,the depositional model and environment of Paleoproterozoic metasedimentary manganese deposits in NCWI implied that the assembly may be located at low latitudes,where the conditions were favorable for dissolving ice and precipitating manganese deposits,

Local intraseasonal air-sea relationship over the North Indian Ocean and western North Pacific during the spring-to-summer transition

This study investigates the local air-sea relationship associated with the two dominant intraseasonal oscillation（ISO） components during the spring-to-summer transition and compares their properties using multiple air-sea variables in the period 1998-2013.The amplitude of percentage variance in SST in periods of 10-20 and 30-60 days are comparable,but the locations of the maxima differ.A strong percentage variance in the 10-20-day SST is evident in the equatorial western Pacific,whereas for the 30-60-day SST the strongest ratio occurs in the North Indian Ocean（NIO）,South China Sea（SCS）,and North Pacific.Over the NIO,SCS,and Philippine Sea,there are significant correlations between SST and precipitation for both 10-20-day and 30-60-day ISOs.In contrast,the correlations between SST and surface heat fluxes cover a broader region and have larger coefficients.Thus,the atmospheric variables and surface heat fluxes show larger variations within the higher frequency band.However,the amplitude of the correlation coefficients between SST and surface heat fluxes,and SST and rainfall,is greater in the lower frequency band.The corresponding time lags for the different variables reveal that a strong local air-sea interaction is indicated over the NIO,SCS,and western North Pacific,from April to June in both timescales;however,the strength of the air-sea relationship depends on the region and variable.

American historic influences on North American Indians

Indians have lived in America for 15,000 or 20,000 years and created their unique civilization.However,since Europeans came,their life was interrupted.The two different cultures conflicted fiercely and influenced each other.After several hundred years of mutual influence,Indians'life had been changed drastically in the terms of population,daily life,arts.And urbanization came up.Therefore,is civilization a good process or bad one? Maybe it can't be judged with only"right"or"wrong".Changes did happen.

Seasonal Behaviour of Mesoscale Eddy Trajectories in the North Indian Ocean Based on Satellite Altimetry

In the north Indian Ocean (NIO), maps of sea level anomaly from satellite altimetry were analysed from January-1995 to December-2000. The study attempted to trace the trajectories of the individual mesoscale anomalies manually and to understand seasonal changes in terms of phase speed. Mesoscale anomalies are detected as concentric circular shapes and diameters of ~90 km to 600 km and the minimum 30 days life cycle. Relatively higher eddy kinetic energy was noticed in the northwestern region of the NIO. Individual mesoscale anomalies, namely positive (warm, anticyclonic eddies) and negative (cold, cyclonic eddies) showing travelling direction westward in the NIO basins. In autumn, the number of negative anomalies detected is more than positive anomalies and vice versa during summer. The westward propagating positive (negative) anomalies in the Arabian Sea start appearing in winter (spring) along (away from) the west coast of India and west of 65°E;individual anomalies move to the west in spring/summer/autumn and collide along Somalia’s & Arabian coast. A group of positive (negative) anomalies trajectories appears as a tail at the southern tip of India are located west of the Laccadive ridge in winter (summer to autumn) associated with LH (LL). The Bay of Bengal (BB) trajectories show southwestward in northern BB, westward in central BB and northwestward in southern BB;individual anomalies are appearing along the west coast of Andaman & Nicobar ridge. The zonal phase speed decreases away from the equator, and the magnitude varies longitudinally in each season in the form of a wave-like pattern propagating westward from autumn to summer;the life cycle of the wave is almost 365 days (a year). The theoretical phase speed of the first mode of the baroclinic Rossby waves is quite similar to that of averaged zonal speed. Therefore mesoscale anomalies (eddies) are embedded into the large waves like phenomenon (Rossby waves), responsible for creating high variability and EKE in the region of NIO along the western boundaries.

三大洋海温异常对2022年2月中国南方持续低温雨雪的影响

2022年2月,中国南方出现持续低温雨雪天气:区域平均降水量126.6 mm,较多年(1981~2020年)平均偏多99.7%;日最低气温5.1℃,较多年平均偏低2.6℃。分析表明,该地区700 hPa到925 hPa异常强的经向风垂直切变是2月持续低温雨雪期间的关键环流特征。经向风垂直切变与三大洋的海温异常均有联系:在赤道中东太平洋海温偏冷的背景下,热带西太平洋和北太平洋中部海温偏暖可导致东亚槽加深和对流层低层到近地面出现偏北风异常;北大西洋中部海温偏暖可通过西欧—东亚沿岸的北支Rossby波列加强乌拉尔山高压脊和东亚槽,使得西伯利亚高压和中国南方低层偏北风增强;东南印度洋海温偏暖有利于南支槽加深和西北太平洋异常反气旋加强,对流层中层偏南风加强。海温对环流的影响有明显的季内变化,北太平洋中部和北大西洋中部海温与西伯利亚高压仅在2月显著相关,有利于2月气温偏低;东南印度洋海温与1月和2月的南支槽显著相关,与2月西北太平洋异常反气旋显著相关,中国南方地区降水从1月中旬起增多可能与该海域海温持续偏暖有关。因此,上述三个海区的海温异常可能与2021/2022年冬季暖干到冷湿的季内转折以及2022年2月持续低温雨雪有关。

东亚夏季风与热带海气相互作用研究进展

在东亚夏季风变异的众多影响因子中,热带海温是影响夏季风系统变化的主要原因。近年来,国内外学者在热带海温异常对东亚夏季风影响的研究方面取得了很大进展。本文从季节内、年际到年代际时间尺度,简要回顾了近年来关于热带海气相互作用影响东亚夏季风变异及其机理的研究进展,特别综述了关于ENSO(El Ni?o-Southern Oscillation)、热带印度洋和大西洋海温异常对东亚夏季风系统的影响和机理方面的主要研究进展。此外,本文还系统回顾了热带海温对东亚夏季风与冬季风关联的影响及过程。最后,提出了在热带海温异常影响东亚夏季风季节内尺度变化、全球变暖下热带海温的变化及其对东亚夏季风的影响等方面值得深入探讨的科学问题。

北印度洋热带气旋统计特征及年代际变化

本研究利用基于统一卫星观测和识别方法产生的ADT-HURSAT气旋数据集,对北印度洋热带气旋在1978~2017共40年的整体特征及年代际变化进行了统计分析。研究发现,春季和秋季是北印度洋热带气旋的高发季节,孟加拉湾气旋数量达到峰值的时间在两个高发季节中均比阿拉伯海提前约一个月。北印度洋气旋的生成区域主要分布于阿拉伯海东部海域和孟加拉湾中部偏西海域。CS(Cyclone Storm)等级气旋更多生成于在北印度洋的偏北海域,ESCS(Extremely Severe Cyclone Storm)等级及以上的强气旋全部在5°N~15°N纬度范围内生成。对于年代际变化,北印度洋热带气旋在秋季的生成数量平均每十年增加5个,生成区域在后二十年呈现向西北方向移动的特点,其中阿拉伯海热带气旋生成位置分别向西移动1.3°和3.2°(p<0.01),较孟加拉湾气旋变化更加显著,平均增强速率也超过孟加拉湾约20%。特别是,相比于前10年(1998~2007),阿拉伯海近10年(2008~2017年)热带气旋数量减少,气旋达到的最大强度提高至120 kt,孟加拉湾气旋数量自1998年以来较为稳定,气旋最大强度却持续降低,这与使用其他数据集的研究结果不同,表明数据集质量对气旋特征变化的重要性。进一步分析发现,北印度洋潜热通量的年代际差异是控制北印度洋热带气旋生成位置年代际变化的主要因素。

不同季节印度洋Walker环流年代际变化的海温驱动因素研究

基于观测资料,本文研究了1900—2015年北半球不同季节影响印度洋沃克(Walker)环流年代际变化的关键海温异常和物理过程,发现在北半球冬季,热带东太平洋海温与热带北大西洋海温均对印度洋Walker环流的年代际变化有影响;在北半球夏季,印度洋Walker环流的年代际变化仅与热带北大西洋海温相关。进一步研究发现,冬季与夏季影响印度洋Walker环流年代际变化的物理机制存在差异。在冬季,太平洋Walker环流与印度洋Walker环流紧密耦合,热带东太平洋海温负异常以及热带北大西洋海温正异常会通过调制大气对流异常,进而增强太平洋Walker环流,并通过跨海盆的“齿轮”效应加强印度洋Walker环流;而在夏季,太平洋Walker环流与印度洋Walker环流的耦合关系消失,取而代之的是热带北大西洋海温正异常通过加强其上空以及北非的对流活动,激发大气开尔文(Kelvin)波而削弱印度洋Walker环流。值得注意的是,冬季和夏季热带北大西洋都对印度洋Walker环流有影响,但效应刚好相反:冬季热带北大西洋增暖有利于印度洋Walker环流的增强,而夏季热带北大西洋增暖使印度洋Walker环流减弱。本文的研究结果为气候长期变化预测提供了理论参考。

Moisture sources of extreme summer precipitation events in North Xinjiang and their relationship with atmospheric circul

In this study, the daily observational precipitation data and NCEP reanalysis data during 1951e2014, Euler and Lagrangian method were used to investigate the moisture sources of summer extreme precipitation events in North Xinjiang. The results show that water vapor at low and upper levels of most summer heavy rain (more than 50 mm d
1 and less than 100 mm d
1) in North Xinjiang are mainly transported by westerly circulation from the North Atlantic Ocean and the Eurasian continent. However, rainstorms of more than 100 mm d
1, which are rarely observed, are dominated by vertically integrated moisture from the North Atlantic, Arctic Oceans, and the Eurasian continent, in addition to lowlevel moisture from the Indian Ocean. Among these sources, the anomalous low-level moisture from the Indian Ocean, which is closely associated with stronger meridional circulation, is considered to be more important with respect to rainstorms. On the days prior to rainstorm days, stronger meridional circulation leads to an anomalous pressure gradient force, which can transport low-level moisture from the Indian Ocean along the eastern periphery of the Tibetan Plateau to North Xinjiang. Furthermore, moisture from the North Atlantic, Arctic Oceans, the Eurasian continent, and the Indian Ocean converge together to influence rainstorm development in this region.

The Trend of Changes in Surface Wind in the Indian Ocean, in the Period from 1981 to 2015, Using Reanalysis Data, NCEP/NCAR

Knowing the pattern of surface winds on the seas and oceans and how it changes over time is of great importance. In this research, the monthly surface wind fields on the Indian Ocean have been studied and analyzed for a 35-year period (1981-2015), using NCEP/NCAR data reanalysis. The results show that transition from cold to warm pattern happens in May and that the summer monsoon pattern begins in June and continues until August. The wind speed pattern tends to the winter monsoon from November on. The maximum average wind speed in June is 13 m/s and its minimum is 2 m/s in October. Direction of prevailing winds is the southwest in the summer. The highest wind speed happens in the latitude of 10 - 15 degrees. Analysis of the wind distribution shows that the wind speed of 2 - 5 m/s happens in about 60% of the cases. There is probability of blowing 0.5 - 4 m/s wind for all months;but this probability is higher in the autumn (October and November) than that in the summer (July and August). Probability of the monthly over 5 m/s winds shows a definitely opposite distribution;that is, wind speed in July and August is higher than that in October. A long-term survey on the speed of surface water wind and sea surface temperature shows an opposite changing trend in wind speed and sea surface temperature during a 55-year statistical period. Wind speed reduced, while the sea surface temperature was increasing. The wind speed gradient in the upper levels of atmosphere graph has been increasing;this phenomenon confirms the effects of global warming and ocean warming on the monsoon system patterns in the Indian Ocean. Keywords

Impact of Tropical Cyclones over the North Indian Ocean on Weather in China and Related Forecasting Techniques:A Review of Progress

Tropical cyclones(TCs)over the North Indian Ocean(NIO)are closely related to Asian summer monsoon activities and have a great impact on the precipitation in the Tibetan Plateau,southwestern China,and even the middle and lower reaches of the Yangtze River.In this paper,the research progress on the impacting mechanisms of NIO TCs on the weather in China and associated forecasting techniques is synthesized and reviewed,including characteristics of the NIO TC activity,its variability under climate change,related precipitation mechanism,and associated forecasting techniques.On this basis,the limitations and deficiencies in previous research on the physical mechanisms and forecasting techniques of NIO TCs affecting the weather in China are elucidated and the directions for future investigations are discussed.