集合最优插值方法在北印度洋海浪同化中的应用

基于第三代海浪模式WaveWatch III,采用集合最优插值(EnOI)方法对北印度洋海浪进行同化数值实验研究。在集合样本选取方案上,针对不同的实验分别选取有效波高(SWH)的历史后报场(样本A)、24h变化(样本B)以及以同一时刻72h预报时效和24h预报时效的差异(样本C)用于估计背景误差协方差。样本A和样本B是为海浪模拟而设计,样本C是为海浪预报而设计;通过与由高度计数据确定的模式背景误差进行比较,认为样本B优于样本A。采用样本B对2011年北印度洋海浪场进行同化模拟,结果表明2011-03-11相对误差改进都在5%及以上,其中7月份改进效果最佳。采用样本C对2013-07的有效波高进行0~72h预报,发现同化使0~24h预报改进最明显:均方根误差改进0.12m,相对误差改进5%。浮标检验结果支持上述结论。     

两种海面风场的对比及对海浪模拟的影响

海面风场在海浪模拟研究和预报中起着关键性的作用,再分析风场数据可为海浪模式提供长时间的大范围、高时空分辨率海面风场。利用日本浮标站资料和卫星高度计资料对再分析风场QuickSCAT/NCEP(Q/N)混合风场和ERA风场进行验证分析,并利用WAVEWATCH-Ⅲ模式进行连续12个月的数值模拟试验。对比风场和计算得到的海浪场得出结论:在风速较小的时候,ERA和Q/N风场较实测风场大,在风速较大的时候,ERA和Q/N风场较实测风场小;ERA风场模拟浪高较浮标观测波高偏小;Q/N混合风场模拟的浪高更接近实测浪高。     

全球海洋初级生产力时空异常变化对ENSO事件的响应

海洋初级生产力在海洋环境要素的驱动下,在不同海域呈现出不同的时空变化特征,这种时空演变特征在不同的ENSO事件类型下差异更为显著。本文基于1998年1月至2017年12月全球海洋初级生产力的卫星遥感数据集,通过改进海洋时空双约束聚类挖掘方法,挖掘了近20年海洋初级生产力的时空聚簇模式,并从时空分布和空间移动2个方面对比分析了海洋初级生产力时空演变簇与ENSO（El Niño-Southern Oscillation）事件之间的关系。结果表明：① 在EP（Eastern-Pacific）型El Niño事件期间,海洋初级生产力异常低值时空簇主要分布在赤道太平洋东部或中东部海域,异常高值时空簇主要分布在西太平洋和南太平洋中部海域;在CP（Central-Pacific）型El Niño事件期间,异常低值时空簇分布在太平洋中部,而异常高值时空簇分布在南太平洋与西太平洋海域;② 在EP型La Niña事件期间,赤道太平洋中部及东部、赤道大西洋与印度洋海域出现异常高值时空簇,南太平洋中东部海域出现异常低值时空簇;在CP型La Niña事件期间,赤道太平洋中部出现异常高值时空簇;南太平洋中西部海域出现异常低值时空簇;③ 发生在赤道太平洋的海洋初级生产力时空演变簇,在EP型ENSO事件期间具有东移特征,而在CP型ENSO事件期间,时空演变簇在赤道太平洋中部海域产生并消亡;④ ENSO事件中海洋初级生产力时空演变簇面积与MEI具有较强相关性。     

Evaluation of Typhoon Waves Simulated by Wave Watch-Ⅲ Model in Shallow Waters Around Zhoushan Islands

In this study, we simulated typhoon waves in the shallow waters around the Zhoushan Islands using the WaveWatch-Ⅲ(WW3) model version 5.16, the latest version released by the National Oceanic and Atmospheric Administration. Specifically, we used in-situ measurements to evaluate the performance of seven packages of input/dissipation source terms in the WW3 model. We forced the WW3 model by wind fields derived from a combination of the parametric Holland model and high-resolution European Center for Medium-Range Weather Forecasts(ECMWF) wind data in a 0.125? grid, herein called H-E winds. We trained the H-E winds by fitting a shape parameter B to buoy-measured observations, which resulted in a smallest root mean square error(RMSE) of 3 m s^-1 for B, when treated as a constant 0.4. Then, we applied the seven input/dissipation terms of WW3, labelled ST1, ST2, ST2+STAB2, ST3, ST3+STAB3, ST4, and ST6, to simulate the significant wave height(SWH) up to 5 m during typhoons Fungwong and Chan-hom around the Zhoushan Islands. We then compared the SWHs of the simulated waves with those measured by the in-situ buoys. The results indicate that the simulation using ST2 performs best with an RMSE of 0.79 m for typhoon Fung-wong and an RMSE of 1.12 m for typhoon Chan-hom. Interestingly, we found the simulated SWH results to be relatively higher than those of the observations in the area between Hangzhou Bay and the Zhoushan Islands. This behavior is worthy of further investigation in the future.     

Analysis of the light curve of the magnetic CP star HD 56022

An examination of the published observational data concerning the light curves of magnetic CP stars has shown that only one star — HD 56022 — shows a light curve with a very long phase interval of light constancy. Only for this type of variability it is imaginable that the equatorial symmetry of the surface brightness distribution could be excluded. However, the analysis of the light curve of HD 56022 in the colour u of the Strömgren system has indicated that the possibly equatorial position of the small bright spot is not in contradiction to this observed curve. From the analysis in u the maximum amplitude of a light curve at another wavelength, where the curve is in counterphase to the light curve in u, can be predicted. The amplitude of such a light curve must be much smaller than 0.1 mag. From unpublished observations of HD 56022 by the satellites TD-1 A and ANS we have determined the amplitude at $LD = 155 nm, where the light curve is in counterphase to that in u, to be 0.2 mag. The consequences from the contradiction between the model and the observations in UV are discussed.     

高频探空温度和风速的质量控制方法研究

针对中国高分辨率探空资料,本文提出了一种计算气候学界限值的方法以满足业务中对资料进行质量控制的需求.首先在垂直方向上将整个大气划分为64层,将落在每层范围内的观测数据都收集到一起进行排序并计算百分位,在此基础上通过比较不同百分位廓线值来获得气候学界限值.除了业务台站,本文还使用了TIPEX-Ⅲ的探空数据来验证本方法在科...     

珠江口盆地恩平21洼文昌组沉积期原型盆地及其对优质烃源岩的控制

珠江口盆地阳江东凹恩平21洼古近纪文昌组沉积期发育断陷湖盆,由于该区古近纪经历多期岩浆底辟和整体构造抬升,导致原型盆地被强烈改造,使其主要生烃层段文昌组的原型盆地面貌不清,从而给油气勘探和资源潜力评价造成困难.本文遵循改造型盆地的研究思路,将地震解析、声波时差法和趋势厚度法相结合,恢复了文昌组沉积期洼陷的原始面貌,并明...     

对铁路施工期线上GNSS网更新原则的探讨

新建南通至上海铁路一期工程线上CPⅡ复测按照新规范技术要求实施,CPⅡ点按照评判标准更新后,部分更新点的坐标变化与CPⅢ控制网的变化并不协调.通过分析复测中的典型案例发现,线上CPⅡ更新在规范评判原则的基础上,还应增加CPⅢ复测与建网成果的分析来确定CPⅡ成果的采用情况,并扩展至无砟轨道.提出了采用CPⅢ控制网的复测数...     

Long-term effects of reduced nutrient inputs to the North Sea

The OSPAR Commission has identified a set of Ecological Quality Objectives (EcoQOs) to assess eutrophication in the North Sea. In order to assess the long-term effects of different river nutrient reduction scenarios in terms of these EcoQOs, a 3-dimensional coupled physical–chemical–biological model, NORWECOM, has been used. The model results show that there is a decreasing response gradient from near-shore to offshore, where the largest effects are identified along the Dutch coast, and that the full potential of a reduction is seen after 2–3 years. The EcoQOs on winter nutrients and chlorophyll are achieved for most areas. Oxygen concentrations displace no or very low response to the modelled nutrient reductions. The study also shows that the ecological quality is controlled to a large extent by winds and ocean circulation.     

STUDY OF A COMPREHENSIVE MONITORING INDEX FOR TWO TYPES OF ENSO EVENTS

Some recent studies presented two existing types of ENSO events, one is the Eastern-Pacific(EP) type and the other the Central-Pacific(CP) type. This study examined the monitoring ability of several current operational ENSO indices. The results indicated that a single index could not distinguish the EP and CP in the historical ENSO events during 1950-2009. The Nio 3 index may only be suitable for monitoring the EP-type ENSO, while the Nio 4 index works only for the CP-type ENSO. In order to capture the occurrence of ENSO events and distinguish the type, we considered a new monitoring index group using Nio 3 and Nio 4 indices. Further analysis confirmed that this index group can monitor different types of historical ENSO events with different spatial distribution of sea surface temperature. It has a good performance in determining the characteristics of the ENSO events, including peak intensity, onset,decay, and mature phase.