On the climatology of persistent circulation anomalies in the atmosphere and in a general circulation model

Abstract

The climatologies of upper‐air persistent circulation anomalies found in observations of the Northern Hemisphere and in a General Circulation Model (GCM) integration are compared with each other and with those found in previous studies. The model simulation is that of the Canadian Climate Centre GCM run at resolution T20. The objective criteria that define the persistent events differ from those of some earlier investigations in that the anomalies are not required to be as nearly stationary. It is found that the GCM generates persistent circulation anomalies downstream of the synoptic‐scale storm tracks, in very nearly the correct geographical locations, but that the frequency of occurrence is too low in the model. A kinetic energy and streamfunction variance analysis is presented for both dataseis to clarify the differences between the observed and simulated distributions of circulation anomalies. It is evident that, apart from the mean annual cycle, the middle‐latitude transient eddies of the model are too weak.     

A fast version of LASG/IAP climate system model and its 1000-year control integration

A fast version of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geo- physical Fluid Dynamics(LASG)/Institute of Atmospheric Physics(IAP)climate system model is briefly documented.The fast coupled model employs a low resolution version of the atmospheric component Grid Atmospheric Model of IAP/LASG(GAMIL),with the other parts of the model,namely an oceanic component LASG/IAP Climate Ocean Model(LICOM),land component Common Land Model(CLM),and sea ice component from National Center for Atmospheric Research Community Climate System Model (NCAR CCSM2),as the same as in the standard version of LASG/IAP Flexible Global Ocean Atmosphere Land System model(FGOALS g).The parameterizations of physical and dynamical processes of the at- mospheric component in the fast version are identical to the standard version,although some parameter values are different.However,by virtue of reduced horizontal resolution and increased time-step of the most time-consuming atmospheric component,it runs faster by a factor of 3 and can serve as a useful tool for long- term and large-ensemble integrations.A 1000-year control simulation of the present-day climate has been completed without flux adjustments.The final 600 years of this simulation has virtually no trends in global mean sea surface temperatures and is recommended for internal variability studies.Several aspects of the control simulation’s mean climate and variability are evaluated against the observational or reanalysis data. The strengths and weaknesses of the control simulation are evaluated.The mean atmospheric circulation is well simulated,except in high latitudes.The Asian-Australian monsoonal meridional cell shows realistic features,however,an artificial rainfall center is located to the eastern periphery of the Tibetan Plateau persists throughout the year.The mean bias of SST resembles that of the standard version,appearing as a"double ITCZ"(Inter-Tropical Convergence Zone)associated with a westward extension of the equatorial eastern Pacific cold tongue.The sea ice extent is acceptable but has a higher concentration.The strength of Atlantic meridional overturning is 27.5 Sv.Evidence from the 600-year simulation suggests a modulation of internal variability on ENSO frequency,since both regular and irregular oscillations of ENSO are found during the different time periods of the long-term simulation.     

北大西洋地区气候准20年周期的观测和模拟分析

北大西洋地区除了存在约70 a周期的AMO（Atlantic Multidecadal Oscillation,北大西洋年代际振荡）之外,历史长期气候记录中英格兰温度（Central England Temperature,CET）与格陵兰冰芯净雪累计率还存在显著的20 a周期波动。本研究利用CCSM4（Community Climate System Model version 4）耦合模式工业革命前控制试验（piControl）结果中的海表面温度（Sea Surface Temperature,SST）,通过10～50 a带通滤波与扩展经验正交函数（Extended Empirical Orthogonal Function,EEOF）分解,得到在北大西洋副极地海区存在准20 a振荡的逆时针旋转模态。此周期与其临近地区的CET、格陵兰冰芯净雪累计率的准20 a振荡周期相吻合,说明这种北大西洋副极地海区准20 a振荡的海洋模态与其临近地区的大气准20 a振荡之间可能存在相应的联系。进一步利用CAM4（the Community Atmosphere Model version4）大气模式,以北大西洋副极地海区准20 a振荡SST旋转模态为强迫场进行敏感性试验,进一步验证了这种联系。     

大庆地区气候异常初步分析

利用统一的标准和方法，计算并分析了大庆地区（肇州，肇源，林甸，林尔伯特4个站）36年的气温和降水演变特征，从中找出气候异常的规律。     

A local climatic model of the temperature-cloudiness relationship

Summary Filtered secular series of temperature at Zagreb (Croatia) are negatively correlated with simultaneous series of solar radiation and positively correlated with cloudiness.The local balance of radiative fluxes, with cloudiness interference included, provides a basis for the evaluation of a local deterministic model, which can describe both the positive and negative impacts of cloud radiative forcing upon surface temperature. A theoretical temperature series, generated by the model simulation, proves a prevailing greenhouse effect of clouds upon recent climatic variations of temperature at Zagreb.With 5 Figures     

2020年6月广西持续性暴雨的天气气候特征

2020年5月30日至6月10日广西出现了大范围持续性暴雨天气过程,造成西江流域部分地区发生洪涝及其衍生灾害.基于广西90个气象观测站降水数据和NCEP/NCAR逐日再分析资料,研究了此次持续性暴雨过程的天气气候特征.结果表明:(1)持续性暴雨期间,西太平洋副热带高压异常偏强、偏西,稳定控制在华南及南海地区,青藏高原上...     

Evidence of recent climatic anomalies at Trieste (Italy)

A recent noticeable climatic anomaly in some meteomarine quantities is analysed based on observations during the period March 1, 1971-February 28, 1993 taken in Trieste (Italy). Marked deviations from the normal values of the coupled quantities atmospheric pressure-solar irradiance and atmospheric pressure-sea level elevation, during the last 22 years, are analysed. The procedures used bring out a clear and persistent configuration of high pressure, high irradiance and low sea level from 1989 on, previously unmatched.     

镇江地区高温气候特征分析及一次连续性高温天气的诊断

本文利用镇江1961—2013年的观测资料以及2.5°×2.5°的逐日NCEP再分析资料,在分析镇江地区高温气候特征的基础上,着重对2013年的连续性高温天气进行诊断。结果表明:镇江夏季高温日数有明显的上升趋势,突变点为2000年,突变后2001—2013年比1961—2000年的年平均高温日数增幅近9 d;镇江地区的高温日数存在3~4 a,6 a,9~13 a,19~27 a的周期,2000年后的准3 a周期稳定存在;强盛且稳定的副热带高压及南亚高压与副热带高压形成的垂直环流的下沉增温,是2013年8月4—18日连续高温产生的重要原因;温度平流和垂直加热对持续性高温天气起积极作用,非绝热加热为负值;连续高温期间海上台风路径偏西偏南,中高纬无明显冷空气活动且2013年梅雨结束时间较早,都为镇江地区出现连续性高温天气提供了有利条件。     

A study of the climatic regimes of the Pleistocene using a stochastic resonance model

A global energy balance model employing the stochastic resonance mechanism, previously used to explain the climatic variability of the late Pleistocene, has now been extended to account for the climatic variations over the full Pleistocene. The possibility that extremely long-term changes (of the order of millions of years) in the boundary conditions of the climate system have altered the response of the Pleistocene climate to the external orbital forcing has been investigated. It is shown that, by slowly changing the only free parameter of the model, the system can undergo a pitchfork bifurcation. The bifurcation point separates a linear regime (identified with the early Pleistocene climate) from a strongly nonlinear regime (the late Pleistocene) where the stochastic resonance mechanism produces rapid and symmetric transitions between the two stable steady states of the system. The main differences in the dynamic features of the two regimes are the change in amplitude of the oscillations, the relative importance of the stochastic forcing, the change in shape of the probability distribution, and the corresponding change in the power centered around the 100000 year cycle: in qualitative agreement with the observed geological record. With the introduction of the external orbital forcing, now spectrally complete and included without requiring any additional hypothesis, the model reproduces the previous results, namely the good correlation with the isotopic record, the appearance of the dominant spectral peaks, as well as the redness of the power spectrum. In particular, it is shown that the orbital forcing in eccentricity acts as a pacemaker of the major glacial cycles of the late Pleistocene through the mechanism of stochastic resonance. A stochastic sensitivity analysis is then applied to validate the significance of the results and to investigate the predictability of the climate system over the time-scales of the orbital cycles.     

A Statistical Model for Investigating Climatic Trend Turning Points

A two-phase trend model is presented to investigate the turning-point signals of evolution trend in long-term series of a climatic element. Based on nonlinear fitting, the revised model brings out more evident improvement of the linear model proposed by Solow et al. (1987). Both theoretical deduction and case calculation show that our version can search the turning point and period accurately and objectively. In particular it is fit for computer exploring the turning points in long-range records from stations covering a large area, thus avoiding subjective judgement by a usual drawing method.     

中国近千年石笋-树轮集成温度记录

分析北京石笋年层和祁连山树轮标准化指数及二者的合成指数与气候的关系,探索对响应不同季节温度变化的不同代用指标进行集成的方法。根据集成序列与中国大区域器测资料的相关计算,建立了年分辨率的跨区域千年温度序列。讨论了中国近千年气温变化的一些特点,发现近千年来年代际温度变化低谷与几个重要的太阳活动极小期非常吻合,大区域平均气候在Sporer Minimum期间响应太阳的突然"冷却",气温下降的速率和幅度比Maunder Minimum期间更为显著。     

Numerical Simulation of Regional Short-Range Climate Anomalies

With the high-speed development of numerical weather prediction, since the later 1980’s, the prediction of short-range climate anomalies has attracted worldwide meteorologists’ attention. What the so called short-range re-fers to the time scale from one month to one season or more. In dealing with the problem of short-range climate pre-diction, two points are needed noticing: one is the basic research to explore or investigate the mechanism of variability of the slow varying components which mainly include internal dynamics of extratropics, external forcings and tropical dynamics, and the other is the modeling efforts to simulate the process of the long-term evolution of the signal which include the improvement of model quality, stochastic prediction and the air-sea-coupled model (Miyakoda et al.,1986). Previous researches on the numerical prediction of short-term climate anomalies are mostly concentrated in the analysis of variables with global spatial scale, especially the global general atmospheric circulation analysis.As to the simulation or prediction of regional short-term climate anomalies, there exist many difficulties and problems. Though some meteorologists are devoting themself to this field, up to now, they have not reached satisfac-tory results. As a primary effort, by using the 2-level general atmospheric circulation model developed in the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP-AGCM) (Zeng et al., 1989), and taking the year of 1985 as a case, a numerical simulation of regional short-term climate change is completed. We pay high attention to the predictand of anomalous summer rainfall in the Yangtze River and Yellow River valleys, especially its month-to-month variation.     

Large sea-ice volume anomalies simulated in a coupled climate model

Climate Dynamics - The processes leading to the formation of a large anomaly of sea-ice volume integrated over the Northern Hemisphere have been investigated in a coarse-resolution...     

长江三角洲夏季降水异常及气候成因

根据长江三角洲地区61个气象站的1961--2007年夏季降水量资料,应用EOF和REOF等统计方法分析了长江三角洲地区夏季降水的时空分布及演变特征,并探讨了夏季降水异常类型的初步成因。结果表明：47a来长江三角洲地区夏季降水有比较明显的年代际变化,1980s开始有明显增加,该地区降水异常可以分为两种类型,分别为一致偏多（少）型和北多（少）南少（多）型,并且通过分析500hPa环流型势、副热带高压和ENSO事件的特征,初步探讨了降水异常的可能成因。     

Orbital forcing in a stochastic resonance model of the Late-Pleistocene climatic variations

Applying a number of simplifying assumptions, we have used a zero-dimensional energy balance climate model (EBM) of the Budyko-Sellers type to investigate the degree to which the climatic variability of the Late Pleistocene can be explained by the mechanism of stochastic resonance. As a logical extension of an earlier version of this model we have included a more complete representation for the orbital forcings to show that a reasonably good agreement with the paleoclimatic record can be obtained. This zerodimensional EBM is appealing because of its simplicity and its ability to reproduce some of the most striking qualitative features of the observed climatic variability with a very limited number of parameters, several of which can be derived from either the observations or general circulation model (GCM) simulations of ice-age conditions.     

The seasonal climatic simulation of 9000 years before present by using the IAP atmospheric general circulation model

The seasonal cycle of the climate of 9000 years before present was simulated with the IAP two-level atmospheric general circulation model. The incoming solar radiation was specified from the orbital parameters for 9000 years Ago. The boundary conditions of that time were prescribed to the present value because of the small differences between the two. The change in radiation makes temperature to be higher in summer and lower in winter over large areas of the land; and the increased temperature contrast between the land and the ocean strengthens the summer monsoon circulation and increases the precipitation over there. The asymmetry of temperature change between the Northern Hemisphere and the Southern Hemisphere and between summer and winter still exists, which agrees with that get from the previous perpetual experiments.     

城市化对江苏气候变化影响的数值模拟个例分析

利用MM5模式对2003年夏季6、7两个月典型区域气候极端事件进行数值模拟,研究城市化急剧扩张对区域气候极端事件的影响和可能机制.研究发现:苏南及邻近地区城市化区域的扩张,会引起区域降水分布的变化.在城市化区域,降水将减少,而在城市化的下风区会有局地的降水增加;同时,在苏南城市化区域中,太湖等湖泊的影响也很重要,会加强其邻近地区局地降水强度.城市化区域的地面气温有明显的上升,对高温天气的作用更大.城市化也会影响地面风场,阻挡穿越城市化区域的风;苏南沿海城市化区域扩张,会使海陆风环流增强,加大了海面向陆面的风.城市化区域的潜热通量明显减少,而感热通量显著增加.城市化增暖产生的局地热源,使城市化区域及邻近地区局地环流发生变化,增强了低层城市化区域向周边辐散的强度.随着高度的增加,城市化的影响也越来越小.