Indian Monsoon Signals Reflected by the Ratio of Cl- to Na+ in Dasuopu Ice Core From Xixiabangma, Himalayas

INDIAN MONSOON SIGNALS REFLECTED BY THE RATIO OF Cl~- TO Na~ IN DASUOPU ICE CORE FROM XIXIABANGMA,HIMALAYAStheChineseNationalBasicResearchProgramme (GrantG19980 4 0 80 0 )andChineseNationalScienceFoun dation (NSFgrant 4 980 10 0 4 )     

Storm catastrophes in the United States

A unique historical data set describing the 142 storms each producing losses in excess of $100 million in the United States during the 1950–89 period were analyzed to describe their temporal characteristics. The storms caused $66.2 billion in losses (in 1991 values), 76% of the nation's insured storm losses in this period. These extreme storm catastrophes (SCs) were most prevalent in the south, southeast, northeast, and central U.S., with few in and west of the Rocky Mountains. Storm incidences were high in the 1950s, low in the 1960s-early 1970s, and increased in the 1980s. Losses due to SCs peaked in the 1950s, again in the late 1960s, with a lesser peak after 1985. The areal extent of storm losses peaked after 1975 and was least in the 1960s. The temporal variations of the three storm measures (incidence, losses, and extent) did not agree except when they all peaked in the 1950s. Regionally-derived time distributions of SCs showed a marked north-south differences in the United States with a U-shaped 40-year distribution in the northern half of the nation, and a relatively flat trend until a peak in the 1980s in the southern regions. The temporal distributions of hurricane-caused catastrophes differed regionally with occurrences in the prime areas, the southern, southeastern, and northeastern U.S., each quite different. Temporal distributions of thunderstorm and winter storm catastrophes were regionally more uniform.     

Quality assessment and hydrogeochemical characteristics of groundwater in Agastheeswaram taluk,Kanyakumari district,Tamil Nadu,India

The present study investigates the hydrogeochemical characteristics of groundwater quality in Agas- theeswaram taluk of Kanyakumari district, Tamil Nadu, India. A total of 69 groundwater samples were collected during pre- and post-monsoon periods of 2011-2012. The groundwater quality assessment has been carried out by evaluating the physicochemical parameters such as pH, EC, TDS, HCO3, Cl, SO42-, Ca2＋, Mg2＋, Na＋ and K＋ for both the seasons. Based on these parameters, groundwater has been assessed in favor of its suitability for drinking and irrigation purpose. Dominant cations for both the seasons are in the order of Na＋〉 Ca2＋〉 Mg2＋ 〉 K＋ while the dominant anions for post monsoon and pre monsoon have the trends of CI 〉 HCO3 〉 SO42- and HCO3- 〉 CI 〉 SO42-, respectively. Analytical results observed from various indices reveal that the groundwater quality is fairly good in some places. Analytical results of few samples show that they are severely polluted and incidentally found to be near the coasts, estuaries and salt pans in the study area. The Gibbs plot indicates that the majority of groundwater samples fall in rock dominant region, which indicates rock water interaction in the study area. The United States salinity （USSL） diagram shows that the groundwater is free from sodium hazards but the salinity hazard varies from low to very high throughout the study area. This reveals that the groundwater is moderately suitable for agricultural activities. The observed chemical variations in pre-monsoon and post-monsoon seasons may be the effect to rock-water interactions, ion-exchange reactions, and runoff of fertilizers from the surrounding agricultural lands.     

Modeling the length of day and extrapolating the rotation of the Earth

The stochastic behavior of the length of day (LOD) process is analyzed and is modeled within statistical accuracy on a time-scale ranging from weeks to millennia by a three-component model comprising a global Brownian motion process, decadal fluctuations, and a 50-day Madden–Julian oscillation. While the model is intended to be phenomenological, some possible physical models underlying the three components are speculated upon. The model is applied to estimate long-range extrapolation errors. For example, it predicts a standard error of 1 h in the clock-time correction ΔT for extrapolation by 1,500 years from 500 to 2000 BC.     

Seasonal Prediction of the Global Precipitation Annual Modes with the Grid-Point Atmospheric Model of IAP LASG

A right annual cycle is of critical importance for a model to improve its seasonal prediction skill. This work assesses the performance of the Grid-point Atmospheric Model of IAP LASG （GAMIL） in retrospective prediction of the global precipitation annual modes for the 1980 2004 period. The annual modes are gauged by a three-parameter metrics： the long-term annual mean and two major modes of annual cycle （AC）, namely, a solstitial mode and an equinoctial asymmetric mode. The results demonstrate that the GAMIL one-month lead prediction is basically able to capture the major patterns of the long-term annual mean as well as the first AC mode （the solstitial monsoon mode）. The GAMIL has deficiencies in reproducing the second AC mode （the equinoctial asymmetric mode）. The magnitude of the GAMIL prediction tends to be greater than the observed precipitation, especially in the sea areas including the Arabian Sea, the Bay of Bengal （BOB）, and the western North Pacific （WNP）. These biases may be due to underestimation of the convective activity predicted in the tropics, especially over the western Pacific warm pool （WPWP） and its neighboring areas. It is suggested that a more accurate parameterization of convection in the tropics, especially in the Maritime Continent, the WPWP and its neighboring areas, may be critical for reproducing the more realistic annual modes, since the enhancement of convective activity over the WPWP and its vicinity can induce suppressed convection over the WNP, the BOB, and the South Indian Ocean where the GAMIL produces falsely vigorous convections. More efforts are needed to improve the simulation not only in monsoon seasons but also in transitional seasons when the second AC mode takes place. Selection of the one-tier or coupled atmosphere-ocean system may also reduce the systematic error of the GAMIL prediction. These results offer some references for improvement of the GAMIL seasonal prediction skill.     

广东英德宝晶宫CO2浓度的时空变化特征

于2011年12月至2013年4月每月一次对广东英德宝晶宫溶洞洞穴空气CO2浓度进行监测,结果显示洞穴空气CO2浓度存在明显的空间变化和季节变化。洞内空气CO2浓度在201×10-6?3 450×10-6之间变化,年平均值为1 018×10-6。在空间上,越靠近洞口或者通风效应越强的地方洞穴空气CO2浓度越低。在季节变化上,表现为洞穴空气CO2浓度在夏半年（5-10月）高而在冬半年（11-4月）低的特点。洞穴空气CO2浓度变化主要受洞穴通风效应和气候变化导致的植被呼吸作用和土壤微生物活动变化的影响。此外,宝晶宫特殊的洞穴结构及游客等因素也对该溶洞CO2浓度变化形成了一定的影响。     

The suspended sediment concentration distribution in the Bohai Sea, Yellow Sea and East China Sea

The distribution of the suspended sediment concentration (SSC) in the Bohai Sea, Yellow Sea and East China Sea (BYECS) is studied based on the observed turbidity data and model simulation results. The observed turbidity results show that (i) the highest SSC is found in the coastal areas while in the outer shelf sea areas turbid water is much more difficult to observe, (ii) the surface layer SSC is much lower than the bottom layer SSC and (iii) the winter SSC is higher than the summer SSC. The Regional Ocean Modeling System (ROMS) is used to simulate the SSC distribution in the BYECS. A comparison between the modeled SSC and the observed SSC in the BYECS shows that the modeled SSC can reproduce the principal features of the SSC distribution in the BYECS. The dynamic mechanisms of the sediment erosion and transport processes are studied based on the modeled results. The horizontal distribution of the SSC in the BYECS is mainly determined by the current-wave induced bottom stress and the fine-grain sediment distribution. The current-induced bottom stress is much higher than the wave-induced bottom stress, which means the tidal currents play a more significant role in the sediment resuspension than the wind waves. The vertical mixing strength is studied based on the mixed layer depth and the turbulent kinetic energy distribution in the BYECS. The strong winter time vertical mixing, which is mainly caused by the strong wind stress and surface cooling, leads to high surface layer SSC in winter. High surface layer SSC in summer is restricted in the coastal areas.     

ENSO事件对我国季节降水和温度的影响

对近40年来ENSO当年和次年我国季节降水和温度异常进行了合成分析和信度检验。结果表明，ENSO当年我国以少雨、低温为主，次年则相反。降水和温度异常季节变化也基本呈相反趋势。长江中下游地区显著降水异常并不发生在夏季，而在ENSO当年春、秋季和次年春季；东北地区最显著的低温也不在夏季，而在ENSO当年秋季至次年春季。根据本文结果对目前ENSO影响研究中的有关问题提出了看法。     

渤海、北黄海海冰与气候变化的关系

渤海和北黄海的冰情随着历年冬季气候差异而不同.暖冬海冰覆盖范围不足海域的15%,而寒冬可覆盖海域80%以上.概述了海冰监测及资料来源.冰覆盖面积、外缘线位置和冰况等级等被作为反映结冰海域冰情的指标.用大连和营口站的气温表示渤海、北黄海海域的局地气候.用1952～2000年大连的月平均气温描述冰情的变化.给出冰情指数由1952/1953年到1999/2000年随大连站月平均气温变化.影响渤海和北黄海冰情和气候的因子很多,诸如大气环流的演变和太阳活动等.分析了多种因子与冰情的滞后相关,指出20世纪90年代渤海冰情持续偏轻与全球气候变暖趋势相当一致;渤海和北黄海冰情的年际变化与El-Nino现象以及太阳活动周期有关;讨论了海冰季节演变的特征