时变涡动输送和阻高形成──1980年夏中国的持续异常天气

１９８０年６至８月发生在中国的持续时间长、强度大的南方低温洪涝及北方高温干旱天气与中高纬地区阻塞高压在东北亚持续发展维持有关。本文研究了时变天气系统的输送过程在强迫阻高形成中的作用。结果表明，源于欧洲强斜压带上的天气尺度扰动在东传过程中出现动能转化。这种转化满足双向法则：在向小尺度系统转化的同时，还向时间平均西风急流及大尺度的阻塞系统输送能量。位涡分析也表明，天气尺度系统维持着急流轴南侧的反气旋式平均位涡和北侧的气旋式平均位涡，并在急流分流区下游激发出高纬强烈的反气旋性涡度增长和相应的正变高。研究表明，这种波流相互作用激发阻高增长的过程比著名的１９７６年夏西欧阻高的发展还强烈得多。因此，在研究中国北方的持续异常天气形势时，除了注意热带、副热带系统的动态外，还必须注意欧洲及西亚地区强斜压带的发展及其上天气尺度系统的传播和输送特征。     

Improvements of a dynamic global vegetation model and simulations of carbon and water at an upland-oak forest

The interest in the development and improvement of dynamic global vegetation models （DGVMs）, which have the potential to simulate fluxes of carbon, water and nitrogen, along with changes in the vegetation dynamics, within an integrated system, has been increasing. In this paper, some numerical schemes and a higher resolution soil texture dataset were employed to improve the Sheffield Dynamic Global Vegetation Model （SDGVM）. Using eddy covariance-based measurements, we then tested the standard version of the SDGVM and the modified version of the SDGVM. Detailed observations of daily carbon and water fluxes made at the upland oak forest on the Walker Branch Watershed in Tennessee, USA offered a unique opportunity for these comparisons. The results revealed that the modified version of the SDGVM did a reasonable job of simulating the carbon and water flux and the variation of soil water content （SWC）. However, at the end of the growing season, it failed to simulate the effect of the limitations on the soil respiration dynamics and as a result underestimated this respiration. It was also noted that the modified version overestimated the increase in the SWC following summer rainfall, which was attributed to an inadequate representation of the ground water and thermal cycle.     

上海郊区二氧化碳通量特征分析

利用上海郊区奉贤的涡动相关通量观测资料,对2015年9月至2016年8月二氧化碳(CO2)通量的时空分布特征、年总排放量进行了分析.结果表明,上海奉贤春、夏、秋季的9-14时CO2通量几乎全为负值,冬季CO2通量则全天均为正值.奉贤CO2通量没有明显的周末效应.植物光合作用是影响奉贤CO2通量时间变化特征的主要因素.各...     

东北冷涡过程的能量学分析

对一次较典型的东北冷涡过程作了能量学分析。结果表明，冷涡涡动动能的主要收入来自涡动位能的转换（Ａｅ→Ｋｅ）。在冷涡发展期，由外边界强气流入侵所产生的动能输入也十分重要。涡动动能的支出主要是转换为纬向气流的动能，即Ｋｅ→Ｋｚ，其次是消耗项和成熟期以后的边界动能输出。冷涡过程涡动动能变化的绝对值以中、高空为大，但相对变率却远小于低空。Ａｅ→Ｋｅ主要发生在７００—３００ｈＰａ中空，高空则为Ｋｅ→Ａｅ的转换     

盘锦芦苇湿地近地面层湍流通量参数化方案研究

基于2005年盘锦芦苇湿地近地面层湍流通量和微气象梯度的连续观测,研究了芦苇湿地近地面层湍流通量参数化方案。结果表明,盘锦芦苇湿地近地面层经常维持弱稳定和弱不稳定层结。在不稳定层结(-0.4     

The eddy pair off eastern Vietnam: Interannual variability and impact on thermohaline structure

The main features, interannual variability of the eddy pair (an anti-cyclonic southern eddy and a cyclonic northern eddy) off eastern Vietnam and its impact on local thermohaline structure are analyzed using altimeter data, the Simple Ocean Data Assimilation (SODA) data, and the Medium-Range Weather Forecasts (ECWMF) data. The results show that the eddy pair is a seasonal phenomenon usually found in the summer to fall. It can reach downward to about 400 m depth but is strongest at the upper 100 m depth. In addition, the eddy pair displays a remarkable interannual variability with periods of 5.6 and 3.6 years. The local wind stress curl plays an important role in the interannual variability of eddy pair. Moreover, the eddy pair has an obvious impact on the thermohaline structure of the local upper ocean. The eddy pair can lead to stronger temperature variability in the upper 380 m but stronger salinity variability only in the upper 150 m depth. When the eddy pair is strong, the anti-cyclonic eddy deepens the thermocline, while the cyclonic eddy shoals the thermocline. Taking the depth of 20 °C isotherm as the thermocline depth, we find that in September, the thermocline drops downward to 110–140 m depth in the anti-cyclonic eddy but rises up to 50–80 m depth in the cyclonic eddy.     

青藏高原东南部昌都地区近地层湍流输送的观测研究

利用我国1998年第2次青藏高原气象科学试验 (TIPEX) 昌都的湍流观测资料, 初步分析了三维风速、温度和湿度湍流谱、归一化方差与稳定度的关系、湍流通量和整体输送系数.结果表明, 白天标准化的湍流谱大多数满足2/3次方定律.风速方差与稳定度的关系在不稳定条件下基本服从1/3次方定律, 但水平风速方差比垂直速度方差与稳定度的关系离散.中性层结下的A、B值比平原地区大, 与起伏地形的值接近, C值与平原地区和起伏地区的差异不大.温度和湿度方差与不稳定层结的关系基本满足1/3次方定律, 而在稳定层结下的关系均无明显规律.湍流通量在干湿期转换中有突变现象, 干期的动量和热量通量均大于湿期, 热源强度以感热为主, 占80%.湿期热源强度明显增大, 其中以潜热为主, 占热源强度的60%.整体输送系数与稳定度的关系明显, 拟合得到的中性层结条件下的C_DN和C_HN分别为4.40×10-3和4.70×10-3, 其结果大于高原中、西部的同期观测值.     

Seasonal drought effects on carbon sequestration of a mid-subtropical planted forest of southeastern China

Continuous measurement of carbon dioxide exchange using the eddy covariance (EC) technique is made at the Qianyanzhou mid-subtropical planted forest as part of the ChinaFLUX network. Qianyanzhou planted forest is affected by typical subtropical continental monsoon climate. It has plentiful water and heat resource but is in inconsistency of its seasonal distribution in the mid-subtropical region, thus seasonal drought frequently occurs in this planted forest. In this study, seasonal drought effect on ecosystem carbon sequestration was analyzed based on net ecosystem productivity (NEP), ecosystem respiration (RE) and gross ecosystem productivity (GEP) at the month scale in 2003 and 2004. In this drought-stressed planted forest, ecosystem carbon sequestration showed a clear seasonality, with low rates during seasonal drought and in winter. The declining degree of ecosystem carbon sequestration under the seasonal drought condition was determined by the accumulation of soil moisture deficits and a co-occurrence of high temperatures. Different drought effects are expected for RE and GEP. The net effect of ecosystem carbon balance depends on how these two quantities are affected relatively to each other. Summer drought and heat wave are two aspects of weather that likely play an important part in the annual NEP of forest in this region.     

中国陆地生态系统通量观测研究网络(ChinaFLUX)的主要进展及发展展望

基于微气象学理论的涡度相关通量观测技术实现了对生态系统尺度的生产力、能量平衡和温室气体交换等功能和过程的直接测定,特别是全球尺度通量塔观测网络的联合观测是实现从生态现象观察和生态要素观测跨越到全球尺度生态系统功能状态变化观测的重大突破。本文回顾了中国陆地生态系统通量观测研究网络(ChinaFLUX)的创建及发展历程,系统介绍了ChinaFLUX的科学目标和设计理念、观测技术体系、观测数据的标准化处理及长期积累;综合评述了ChinaFLUX在陆地生态系统碳—氮—水的收支评估和交换过程的环境响应、碳通量时空格局及其形成机制等方面所取得的主要研究进展。最后,在探讨未来全球尺度通量塔观测网络发展趋势的基础上,提出了ChinaFLUX的主要发展方向、关键科学问题与未来工作重点,为中国通量观测研究事业的进一步发展提供理论参考。     

一次中亚低涡中期过程的能量学特征

中亚低涡是中期时间尺度（4天以上）的对流层深厚切断低压系统,也是造成新疆暴雨（雪）、持续低温天气的重要影响系统之一,对其形成、维持和减弱的能量特征还不十分清楚。利用美国国家环境预报中心/国家大气研究中心（NCEP/NCAR）2.5°×2.5°逐日再分析资料和有限区域能量循环方程,对1996年7月10—20日造成新疆区域两次暴雨过程的中亚低涡系统进行分析,以揭示低涡持续活动11天的能量循环和转换特征。分析结果表明,中亚低涡活动具有明显的阶段性能量学特征。这次低涡发展和减弱过程处于斜压不稳定状态,扰动动能来源于扰动位能的转换和区域开放边界扰动动能的输入,且两者作用相当,它们使得低涡快速发展,同时区域内部非绝热加热制造的一部分扰动有效位能向外输出,在减弱期扰动有效位能向外输出大于扰动位能的转换和区域开放边界扰动动能的输入,因此低涡逐渐减弱。低涡成熟期处于正压不稳定状态,系统内部的能量转换很小,扰动动能来自于外界扰动位能输入,支出项为向开放边界的扰动动能输出。低涡过程各个时期纬向平均动能向扰动动能的转换都很小,即正压不稳定造成的能量转换较弱。低涡活动过程中,在对流层中、高层扰动动能很强,表明中亚低涡是主要在对流层中、高层活动的天气尺度系统,低涡内部的能量转换及其与外界的能量输送主要发生在中、高层,扰动位能和扰动动能的变化很好地反映低涡的强度变化和发展阶段,且能量的垂直输送对低涡系统的发展也有一定促进作用。