A Comparison Study of Tropical Pacific Ocean State Estimation： Low-Resolution Assimilation vs. High-Resolution Simulation

A comparison study is performed to contrast the improvements in the tropical Pacific oceanic state of a low-resolution model respectively via data assimilation and by an increase in horizontal resolution.A low resolution model (LR) (1°lat by 2°lon) and a high-resolution model (HR) (0.5°lat by 0.5°lon) are employed for the comparison. The authors perform 20-yr numerical experiments and analyze the annual mean fields of temperature and salinity. The results indicate that the low-resolution model with data assimilation behaves better than the high-resolution model in the estimation of ocean large-scale features.From 1990 to 2000, the average of HR's RMSE (root-mean-square error) relative to independent Tropical Atmosphere Ocean project (TAO) mooring data at randomly selected points is 0.97℃ compared to a RMSE of 0.56℃ for LR with temperature assimilation. Moreover, the LR with data assimilation is more frugal in computation. Although there is room to improve the high-resolution model, the low-resolution model with data assimilation may be an advisable choice in achieving a more realistic large-scale state of the ocean at the limited level of information provided by the current observational system.     

IMPACT OF LARGE-SCALE CIRCULATION ON THE INTERDECADAL VARIATIONS OF THE WESTERN NORTH PACIFIC TROPICAL CYCLONE

Based on the annual frequency data of tropical cyclones from 1960 to 2005 and by the polynomial fit and statistical analysis, this work has discovered that TC activity in the 46a exhibits significant decadal- scale variability. It has two high frequency periods (HFP) and two low frequency periods (LFP). Significant differences in the number of TCs between HFP and LFP are found in active TC seasons from July to October. Differences of large-scale circulation during HFP and LFP have been investigated with NCEP/NOAA data for the season. In HFP, the condition includes not only higher sea surface temperature,lower sea level pressure, larger divergence of upper air, larger relative vorticity at low levels and smaller vertical shear, but also 500-hPa wind vector being more available for TC activity and moving to western North Pacific, the position of the subtropical anticyclone over the western Pacific shifting more northward,and South Asian Anticyclone at 100-hPa being much smaller than that in LFP. The precipitation of western North Pacific has no clear influence on TC activity.     

Relationship Between Soil Temperature in May over Northwest China and the East Asian Summer Monsoon Precipitation

This study investigates the relationship between the soil temperature in May and the East Asian summer monsoon （EASM） precipitation in June and July using station observed soil temperature data over Northwest China from 1971 to 2000.It is found that the memory of the soil temperature at 80-cm depth can persist for at least 2 months,and the soil temperature in May is closely linked to the EASM precipitation in June and July.When the soil temperature is warmer in May over Northwest China,less rainfall occurs over the Yangtze and Huaihe River valley but more rainfall occurs over South China in June and July.It is proposed that positive anomalous soil temperature in May over Northwest China corresponds to higher geopotential heights over the most parts of the mainland of East Asia,which tend to weaken the ensuing EASM.Moreover,in June and July,a cyclonic circulation anomaly occurs over Southeast China and Northwest Pacific and an anticyclonic anomaly appears in the Yangtze and Huaihe River valley at 850 hPa.All the above tend to suppress the precipitation in the Yangtze and Huaihe River valley.The results also indicate that the soil temperature in May over Northwest China is closely related to the East Asia/Pacific （EAP） teleconnection pattern,and it may be employed as a useful predictor for the East Asian summer monsoon rainfall.     

Sensitivity of ENSO variability to Pacific freshwater flux adjustment in the Community Earth System Model

The effects of freshwater flux （FWF） on modulating ENSO have been of great interest in recent years. Large FWF bias is evident in Coupled General Circulation Models （CGCMs）, especially over the tropical Pacific where large precipitation bias exists due to the so-called ＂double ITCZ＂ problem. By applying an empirical correction to FWF over the tropical Pacific, the sensitivity of ENSO variability is investigated using the new version （version 1.0） of the NCAR＇s Community Earth System Model （CESM1.0）, which tends to overestimate the interannual variability of ENSO accompanied by large FWF into the ocean. In response to a small adjustment of FWF, interannual variability in CESM1.0 is reduced significantly, with the amplitude of FWF being reduced due to the applied adjustment part whose sign is always opposite to that of the original FWF field. Furthermore, it is illustrated that the interannual variability of precipitation weakens as a response to the reduced interannual variability of SST. Process analysis indicates that the interannual variability of SST is damped through a reduced FWF-salt-density-mixing-SST feedback, and also through a reduced SST-wind-thermocline feedback. These results highlight the importance of FWF in modulating ENSO, and thus should be adequately taken into account to improve the simulation of FWF in order to reduce the bias of ENSO simulations by CESM.     

亚太地区迁移研究网络（APMRN）第八次国际会议在福建师范大学召开

2007年5月26～29日，亚洲及太平洋地区迁移研究网络（Asia Pacific Migration Research Network，简称APMRN）第八次国际会议在福建师范大学召开。[第一段]     

拉尼娜回来了

经过近几十年的研究,人们已经在很大程度上认识了热带太平洋海气相互作用在改变全球天气和气候型方面的重要作用。例如,在El Nio事件期间,热带中东太平洋地区海表温度比正常情况偏高,相反,在La Nia事件期间,该区域海表温度比正常情况偏低。海表温度的变化与全球主要的气候波动紧密联系,这种气候波动一旦被触发有可能延续12个月或更长时间。     

太平洋地区晚第三纪事件的时空分布——IGCP246主要成果和启示

ＩＧＣＰ２４６着重研究太平洋地区晚第三纪事件的时分布。本文综述其主要成果，包括：①气候最适期事件，②海水变冷、上升流事件，③构造运动和相关的古生物地理事件，和④重大的生物演化事件；评述这些事件的内在联系和影响，及给我们的启示。     

中国学者提出热带地区气候变化新驱动机制有助于预测未来气候变化趋势

2011年4月26日,《自然·通讯》发表了中国科学技术大学极地环境研究室孙立广课题组的研究成果《过去千年南海水文变化与太平洋沃克环流变化》。该成果对南海地区过去千年降雨变化进行了研究,并对热带太平洋地区气候变化机制提出了新的认识。     

基于历史文献资料的17世纪以来东北亚台风信息挖掘

西北太平洋地区,尤其是东北亚地区,台风灾害多发,这些地区的台风的运动轨迹变化会对社会经济发展带来深刻的影响。台风活动跨海而行,因此将东北亚几个国家的历史台风信息结合起来,才能看出其全貌。中日两国,最早通过仪器观测描述的台风路径分别为1879年和1878年,历史时期的东北亚地区台风事件只能靠历史文献来推测。以在台风路径的推测上具有问题（台风影响范围评估、详细记录时间的利用、2次相近台风的辨别等）的4次台风事件为例,讨论17世纪以来东北亚台风路径的推测方法。通过对台风个案的讨论,指出将致灾记录和感应记录相结合的可行性;利用仪器观测时期台风记录验证历史文献记载的有效性。相当一部分日记资料在古风暴研究中仍处于未被发掘状态。历史上流传至今的公用日记和各名家的家记,拥有较长的写作时间和较为均质的写作内容,可提高跨国界古风暴研究的时空分辨率。