天文观测攻略系列之三十七深空天体观测入门攻略（十二）

进入12月,北半球中纬度地区正式进入冬季,黑夜长,自昼短,十分适宜长时间观星。不过,许多地方此肘天气会变得非常寒冷,观星一定要注意保暖,避免着凉生病。 12月的星空,是秋冬之交的星空,天刚黑时,头顶还是秋夜星空的代表——飞马座四边形,而冬夜群星,正在东方慢慢升起。因此,我们抓住秋夜星空的尾巴,介绍一个天赤道附近的小星系和一个秋夜银河中的小星团。对本系列有任何意见或建议,欢迎给笔者发邮件交流：universezx@bjp．org．cn。     

深空天体观测入门攻略（十八）

进入12月,北半球中纬度地区正式进入冬季,黑夜长,自昼短,十分适宜长时闻观星。不过,许多地方此时天气会变得非常寒冷,观星一定要注意保暖,避免着凉生病。     

北半球对流层厚度的时空变化特征

利用1948—2010年NCEP/NCAR逐月位势高度再分析资料、美国国家海洋局提供的1948—2010年逐月海温再分析资料,分别定义了1 000—500 hPa和500—200 hPa厚度,利用EOF、SVD等方法研究了北半球对流层厚度时空演变特征及其与大气环流和海面温度的关系。结果表明,冬季平均厚度EOF第一模态均具有北太平洋及附近高纬度亚洲大陆地区与北美大陆高纬地区反位相变化的特点,而夏季第一模态则是北半球范围内较一致的位相分布;冬、夏季平均厚度EOF第二模态均突出体现了欧亚大陆及附近地区与北半球其他地区反位相变化的特点;冬、夏季厚度场的变化形势与大气环流及海面温度具有密切联系。     

A Theoretical Explanation of Anomalous Atmospheric Circulation Associated with ENSO Modoki during Boreal Winter

Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （ENSO） Modoki in winter. The ideal triple pattern is composed of an equatorially symmetric heat source in the middle and equatoriaUy asymmetric cold forcing in the southeast and northwest. The equatorially symmetric heat source excites low-level cyclonic circulation anomalies associated with Rossby waves in both hemispheres, while the northwest- ern and southeastern equatorially asymmetric cold sources induce low-level anomalous anticyclones associated with Rossby waves in the hemisphere where the forcing source is located. Low-level zonal winds converge toward the heat sources associated with Kelvin and Rossby waves. Due to unequal forcing intensity in the northwest and southeast, atmospheric responses around the equatorially symmetric forcing become asymmetric, and low-level cyclonic circulation anomalies in the Southern Hemisphere become greater than those in the Northern Hemisphere. Ascending （descending） flows coincide with heat （cold） sources, resulting in a double-cell structure over the regions of forcing sources. Ideal triple patterns similar to SSTA patterns associated with La Nina Modoki produce opposite atmospheric responses. The theoretical atmospheric responses are consistent with observed circulation anomalies associated with ENSO Modoki. Therefore, the theoretical solutions can explain the dynamics responsible for atmospheric circulation anomalies associated with ENSO Modoki events.     

The boreal summer intraseasonal oscillation simulated by four Chinese AGCMs participating in the CMIP5 project

The performances of four Chinese AGCMs participating in the Coupled Model Intercomparison Project Phase 5 （CMIP5） in the simulation of the boreal summer intraseasonal oscillation （BSISO） are assessed. The authors focus on the major characteristics of BSISO： the intensity, significant period, and propagation. The results show that the four AGCMs can reproduce boreal summer intraseasonal signals of precipitation; however their limitations are also evident. Compared with the Climate Prediction Center Merged Analysis of Precipitation （CMAP） data, the models underestimate the strength of the intraseasonal oscillation （ISO） over the eastern equatorial Indian Ocean （IO） during the boreal summer （May to October）, but overestimate the intraseasonal variability over the western Pacific （WP）. In the model results, the westward propagation dominates, whereas the eastward propagation dominates in the CMAP data. The northward propagation in these models is tilted southwest-northeast, which is also different from the CMAP result. Thus, there is not a northeast-southwest tilted rain belt revolution off the equator during the BSISO＇s eastward journey in the models. The biases of the BSISO are consistent with the summer mean state, especially the vertical shear. Analysis also shows that there is a positive feedback between the intraseasonal precipitation and the summer mean precipitation. The positive feedback processes may amplify the models＇ biases in the BSISO simulation.     

巧用数学知识 智解地理问题

正在给学生复习气候类型判读时,我举2013四川高考题(5~6题)为例。图1是北半球亚热带某地降水量逐月累计曲线图。读图回答1~2题。(2013年四川卷)     

中学地理有关太阳视运动的复习总结

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高三地理有效复习课堂的建构——以“气压带与风带”为例

正一、基础过关1.在下图中相应位置填出全球性气压带与风带,并完成下表。极地高气压带极地高气压带气压带风带90。S60。S30。S30。N0。60。N90。N极地东风带极地东风带该图及下表的设计只是让学生选填部分重点的气压带与风带,没有让学生每个都填出,这不仅节省了课堂时间,提高容量,同样可以检测出学生对气压带与风带基础知识的掌握情况,强化了学生对基础知识的巩固。并通过典型例题1引导学生对"气压带、风带随太阳直射点移动"的灵活迁移运用。     

深空天体观测入门攻略（四）

8月到了,北半球进入了仲夏时节。夏夜对天文爱好者来说是又爱又恨,爱的是夏夜星空非常壮丽,一奢明亮的银河横贯天空,同时夏夜天气也比较暖和,观测时不至于受冻了。恨的是夏天天黑太晚,可观测时间太短,同时夏夜野外蚊虫较多,会给观测带来一点儿小麻烦。不过对于学生爱好者而言,不用上学的暑假是当之无愧的进行天文观测的最佳时节。夏夜星空中有许多漂亮的深空天体,它们就像一个个珍宝隐藏在夜空之中。下面,就让我带大家去欣赏几个深空天体吧!对本系列有任何意见或建议,欢迎发邮件到我的邮箱：universezx@bjp．org．cn。     

上新世/更新世之交太平洋经向翻转流演化

随着北半球冰盖的发育,全球气候环境发生了显著变化。太平洋经向翻转流（PMOC）对全球海洋热量分配和大气CO₂在深海的封存起举足轻重的作用,但是关于PMOC与北半球冰盖的形成之间的关系还欠缺研究。本文收集了太平洋海山富钴结壳的Nd同位素记录,通过对比不同区域Nd同位素记录的演化特征,分析风尘输入、水团演化等因素对Nd同位素记录的影响,探讨了太平洋经向翻转流演化及其与全球气候变化之间的关系,认为北太平洋深层水下沉的停滞和亚洲风尘输入增加可能是导致深层水Nd同位素从距今3～4 Ma开始降低的原因。同时,因北太平洋深层水下沉停滞,PMOC改组,使得更多的CO₂在深水封存,从而对全球气候变冷和北半球冰盖形成产生了积极的贡献。