Stratospheric Ozone-induced Cloud Radiative Effects on Antarctic Sea Ice

Recent studies demonstrate that the Antarctic Ozone Hole has important influences on Antarctic sea ice.While most of these works have focused on effects associated with atmospheric and oceanic dynamic processes caused by stratospheric ozone changes,here we show that stratospheric ozone-induced cloud radiative effects also play important roles in causing changes in Antarctic sea ice.Our simulations demonstrate that the recovery of the Antarctic Ozone Hole causes decreases in clouds over Southern Hemisphere(SH)high latitudes and increases in clouds over the SH extratropics.The decrease in clouds leads to a reduction in downward infrared radiation,especially in austral autumn.This results in cooling of the Southern Ocean surface and increasing Antarctic sea ice.Surface cooling also involves ice-albedo feedback.Increasing sea ice reflects solar radiation and causes further cooling and more increases in Antarctic sea ice.     

单片机控制的锁相频率合成技术

叙述了由单片机、定时计数器8253－5及单片集成锁相环路组成的可程控频率合成技术，而标频可经单片机设定预置值给定时器T1而形成，并经锁相环路产生各种离散的频率输出。     

青藏高原感热加热对7月份大气环流和亚洲夏季风影响的数值试验

根据低纬地区地表温度高、蒸发及降水量大、辐合上升运动剧烈等特点,本文构造了一个正压模式的方程组,提示出影响低纬大气波动的一个重要因素——海表温度SST。研究指出:(1)当SST<25℃时,含蒸发风反馈机制的Rossby波向西传播,当SST>25℃时.含蒸发风反馈机制的Rossby波向东传播。(2)SST的数值越高,空气越潮湿,含蒸发风反馈机制的Rossby波传播速度就越小。当SST超过29℃时,会形成周期为30天的低频振荡。     

Mechanisms of variability and predictability of the tropical coupled ocean-atmosphere system

A conceptual model is proposed to explain the observed aperiodicity in the short term climate fluctuations of the tropical coupled ocean-atmosphere system. This is based on the evidence presented here that the tropical coupled ocean-atmosphere system sustains a low frequency inter-annual mode and a host of higher frequency intra-seasonal unstable modes. At long wavelengths, the low frequency mode is dominant while at short wavelengths, the high frequency modes are dominant resulting in the co-existence of a long wave low frequency mode with some short wave intra-seasonal modes in the tropical coupled system. It is argued that due to its long wavelength, the low frequency mode would behave like a linear oscillator while the higher frequency short wave modes would be nonlinear. The conceptual model envisages that an interaction between the low frequency linear oscillator and the high frequency nonlinear oscillations results in the observed aperiodicity of the tropical coupled system. This is illustrated by representing the higher frequency intra-seasonal oscillations by a nonlinear low order model which is then coupled to a linear oscillator with a periodicity of four years. The physical mechanism resulting in the aperiodicity in the low frequency oscillations and implications of these results on the predictability of the coupled system are discussed.     

Environmental information for total catchment management: incorporating local knowledge

Total Catchment Management (TCM) has been implemented in New South Wales to provide a more integrated, participatory' approach to natural resource management. This change in direction poses significant challenges for obtaining and integrating environmental information. This paper examines the adequacy of environmental information in terms of both the participatory turn in government policy and the management imperatives of the integrated, catchment‐wide approach of TCM. Drawing on empirical studies in the Hunter Valley, it is suggested that current information available for TCM is inadequate and reflects a fragmented approach that is primarily concerned with biophysical phenomena and is generated at inappropriate scales. Furthermore, most information is generated by government agencies, ignoring the substantial contribution that catchment occupiers could make. It is argued that the utilisation of the knowledge and experience of occupiers could provide more integrated catchment perspectives while meeting the participatory goals espoused in TCM.     

一个自组织气候模型

本文选择全球平均地表温度#AT#a和全球平均云量#An#a为状态变量。通过对气候系统中物理过程的研究与在气候意义上的合理近似，得到行星反照率α和大气有效发射率ε与状态变量的参数化关系，它们给出了气候系统内部几个重要的反馈过程。利用这些结果，建立起一个云和辐射相互作用的零维的非线性气候模型。在Hopf分支点附近，得到极限环的解析解，它们同数值解吻合得相当好，由解析解得到振幅，周期和位相差与太阳常数和CO2的近似关系，依此可估计它们在气候振荡中的作用，尤其，我们发现CO2的增加除有增温效应外，还能使气候振荡的振幅增加，这个结果意味着CO2的增加可能导致自然灾害周期性地出现或加剧。     

塔克拉玛干沙漠腹地流沙下垫面土壤呼吸特征及影响因素分析

通过LI-COR8100A土壤碳通量观测系统分别于2013年1月、5月、10月和11月进行了塔克拉玛干沙漠腹地塔中流沙下垫面土壤呼吸速率测定试验,并分析了相应的土壤水热因子对呼吸速率的影响。结果表明:塔克拉玛干沙漠腹地土壤呼吸速率整体偏低,但具有明显的昼夜波动性和季节变化特征。研究区流沙土壤中可能存在的无机碳过程是导致夜间及凌晨的土壤呼吸速率为负值,白天为正值的主要原因。不同时段的土壤呼吸速率(Rs)分别与土壤表层0~5 cm平均土壤温度(T)和湿度(W)间存在较为同步的昼夜变化趋势且具有良好的回归关系。相对于单因素影响的回归分析,土壤温、湿度的协同作用能够从整体角度更好地解释土壤呼吸速率的变化情况。回归方程Rs=a+bT+cW和Rs=a+bT+cW+dTW可解释不同时段土壤呼吸速率76.0%以上的变化情况。这说明土壤温、湿度是控制土壤呼吸速率的主要环境因子。沙漠腹地土壤极低的水分条件成为土壤呼吸的限制性因子,呼吸速率对于作为限制性因子的土壤湿度的变化响应则更加直接,而对于土壤温度变化的敏感性就有所下降,导致土壤呼吸速率与土壤温度回归关系出现明显的时滞环现象。     

南京地区高温天气下城市化影响的模拟研究

利用WRF(Weather Research and Forecasting)模式耦合单层城市冠层模式,研究了南京地区一次高温热浪过程(2013年8月5—10日)中气溶胶的辐射效应、城市扩张对边界层的影响和它们间的相互作用。结果显示,由于气溶胶的直接辐射效应,在白天,南京近地面温度平均降低约0.11℃,净辐射平均降低约12 W/m~2;城市扩张使近地面温度增加约1.7℃,在本次试验过程中,城市扩张的增暖效应明显强于气溶胶冷却效应。另外,由于城市扩张后产生了较强的增暖作用,加强了周围气流的辐合运动,城市区域风速平均增加约0.8 m/s。白天潜热通量的减少与感热通量的增加导致城市边界层内温度升高,并且城市增暖引起的上升运动将气溶胶抬升至更高层,使边界层更不稳定,气溶胶与城市边界层稳定性之间可能存在正反馈。     

气候环境驱动下的中国北方早期社会历史时空演进及其机制

诸多沉积记录揭示,中国北方早期历史,气候环境大致经历了3580-3050 cal a BP、3050-1800 cal a BP两个阶段;前者为稳定的湿润气候期,后者为逐渐趋于干燥的气候期;前期为中国历史上第二个王朝—商王朝统治期,政局稳定,社会承平,王朝较为稳定地传承了500余年,是中国历史上“寿命”最长的朝代;后者对应西周—东周（春秋—战国）—秦—西汉—东汉—三国等朝代,在不足1300年内,政权格局多次更迭,表现出一种与前期截然相反的社会政治生态。这期间,以都城为标志的王朝的重心,具有向东南迁移的趋势。年代对比发现,商代夏、周代商、平王东迁、西汉甚至东汉灭亡等改朝换代的社会政治事件,都与沉积记录所指示的气候环境的显著变化（恶化）对应。研究再次证实早期的中国历史与气候变化存在密切的关系,并认为如下两个因素可以阐述这种关系的存在：① 中国北方地理环境空间是扇状的,且自然环境具有梯度变化的特征,这种地理环境格局叠加在气候变化之上,具有特殊的加剧与舒缓区域社会矛盾的作用。② 小农经济具有对气候变化的特殊敏感性。对西汉所做的案例考察认为,不尽合理的社会体制往往通过一系列反馈作用将这种敏感性在气候恶化阶段“放大”,随之形成一系列连锁反应,由此造成的各种危机成为王朝崩溃重要因素。     

Dynamical Feedback between Synoptic Eddy and Low-Frequency Flow as Simulated by BCC_CSM1.1(m)

Since the interaction between atmospheric synoptic eddy(SE)(2–8 days) activity and low-frequency(LF)(monthly)flow(referred to as SELF) plays an essential role in generating and maintaining dominant climate modes,an evaluation of the performance of BCC_CSM1.1(m) in simulating the SE feedback onto the LF flow is given in this paper.The model captures well the major spatial features of climatological eddy vorticity forcing,eddy-induced growth rate,and patterns of SELF feedback for the climate modes with large magnitudes in cold seasons and small magnitudes in warm seasons for both the Northern and Southern Hemisphere.As in observations,the eddy-induced growth rate and SELF feedback patterns in the model also show positive SE feedback.Overall,the relationships between SE and LF flow show that BCC_CSM1.1(m)satisfactorily captures the basic features of positive SE feedback,which demonstrates the simulation skill of the model for LF variability.Specifically,such an evaluation can help to find model biases of BCC_CSM1.1(m) in simulating SE feedback,which will provide a reference for the model's application.