用GMS-5对东亚地区对流层高层水汽的研究

大气中的水汽是气候变化中至关重要的影响因子,对流层高层的水汽对地气系统的辐射能量平衡尤为重要。卫星观测极大地弥补了常规探空手段对高空低温低湿条件下的水汽探测能力的不足。6．7μm水汽通道是被广泛用于大气水汽反演的卫星通道之一,Soden等（1993）提出一个用该通道亮温反演对流层高层水汽的方法。将这一方法应用于日本GMS-5静止卫星的水汽云图,得到东亚地区中无云区域与水汽云图具有相同时空分辨率的对流层高层水汽分布。反演得到的月平均对流层高层平均相对湿度与NCEP分析资料给出的平均相对湿度具有较好的一致性。根据 1996-2002年的GMS 5水汽通道亮温资料得到东亚地区对流层高层水汽的典型时、空分布形式。随卫星观测记录的延续,反演得到的长时间序列的对流层高层相对湿度资料将为水循环的研究和水汽对气候变化响应和反馈的研究提供有力依据。     

东亚沙尘源区晴空和云上沙尘气溶胶特征

利用2006年6月至2012年12月的CALIPSO Level 2 VFM产品、5 km分辨率的Aerosol Profile、Cloud Layer产品以及MISR反演的产品,揭示了东亚地区不同高度层上沙尘的时空分布特征,重点对比分析了东亚沙尘源区晴空和云上沙尘的垂直分布特征、消光系数和光学厚度。结果表明：塔克拉玛干沙漠和戈壁沙漠是东亚沙尘的主要源区,沙尘出现频率具有显著的季节差异,春季最多,夏秋相当,冬季最少,无论在晴空还是有云条件下,前者出现频率大于后者。对于同一地区而言,云上沙尘出现的最大高度较晴空沙尘更高。塔克拉玛干沙漠云上沙尘消光系数高值区集中在2~4 km,而戈壁沙漠则集中在3~5 km,但是在云层之上晴空和云上沙尘消光系数差别不大。塔克拉玛干沙漠以沙尘气溶胶为主,约占总气溶胶光学厚度的77%,晴空和云上沙尘光学厚度平均值分别为0.22和0.15;戈壁沙尘气溶胶约占总气溶胶光学厚度的52%,晴空和云上沙尘光学厚度的平均值分别为0.09和0.06。     

An Overview of the Studies on Black Carbon and Mineral Dust Deposition in Snow and Ice Cores in East Asia

Black carbon （BC） is the most eff ective insoluble light-absorbing particulate （ILAP）, which can strongly absorb solar radiation at visible wavelengths. Once BC is deposited in snow via dry or wet process, even a small amount of BC could signifi cantly decrease snow albedo, enhance absorption of solar radiation, accelerate snow melting, and cause climate feedback. BC is considered the second most important component next to CO2 in terms of global warming. Similarly, mineral dust （MD） is another type of ILAP. So far, little attention has been paid to quantitative measurements of BC and MD deposition on snow surface in the midlatitudes of East Asia, especially over northern China. In this paper, we focus on reviewing several experiments performed for collecting and measuring scavenging BC and MD in the high Asian glaciers over the mountain range （such as the Himalayas） and in seasonal snow over northern China. Results from the surveyed literature indicate that the absorption of ILAP in seasonal snow is dominated by MD in the Qilian Mountains and by local soil dust in the Inner Mongolian region close to dust sources. The detection of BC in snow and ice cores using modern techniques has a large bias and uncertainty when the snow sample is mixed with MD. Evidence also indicates that the reduction of snow albedo by BC and MD perturbations can signifi cantly increase the net surface solar radiation, cause surface air temperature to rise, reduce snow accumulation, and accelerate snow melting.     

TRACE-P期间硫酸盐、硝酸盐和铵盐气溶胶的模拟研究

结合最新评估的东亚地区 1°× 1°污染源资料 ,利用由区域大气模式系统 (RAMS)和区域大气质量模式系统 (CMAQ)耦合的空气质量模式系统 ,对东亚地区 2 0 0 1年春季气溶胶的输送及其化学转化过程进行了研究。为了检验模式系统的模拟效果 ,我们将模拟的硫酸盐、硝酸盐和铵盐气溶胶的浓度与TRACE -P观测期间获取的观测值进行了比较。比较结果显示 ,模拟值与观测值具有相当好的一致性 ,模式很好地反映了气溶胶浓度的分布特征和变化规律 ,再现了许多观测到的重要特征。模拟结果表明 ,中国区域硫酸盐气溶胶浓度高值主要是人为排放的二氧化硫造成的 ,10 0°E以东的中国广大地区的硫酸盐气溶胶柱含量超过了 6mg·m- 2 ,最高值达到 2 4mg·m- 2 ,柱含量 >16mg·m- 2 的区域延伸到中国近海的广大海域。东亚地区的人类活动不仅使污染地区气溶胶柱含量显著增加 ,而且使近海无源区的广大海域的污染加重。本模式系统的建立为今后进一步研究区域大气污染物的变化机理提供了有效的手段。     

A numerical study on the winter monsoon and cold surge over East Asia

By using the improved regional climate model （RegCM_NCC）, a numerical study has been undertaken for the East Asia region over a period of 5 years （1998-2002） in an effort to evaluate the model＇s ability to reproduce the winter monsoon conditions that were observed. The results showed that the model can successfully simulate the basic characteristics of the winter monsoon circulations, including the location and intensity of the cold-surface, high-pressure system, as well as the wind patterns and the intensity of the winter monsoon. The simulated occurrence frequency and regions of the cold surge were consistent with the observations. The simulated rainfall distribution over China was consistent with the observations collected in South China. The features of the simulated moisture transport were also in good agreement with the observations that were derived from the NCEP reanalysis data, indicating that moisture transport coming from the Bay of Bengal trough plays a crucial role in supplying moisture needed for precipitation in South China. In addition, the moisture transport coming from the near-equatorial west-Pacific was also important. These two branches of moisture transport converged in South China, as a prerequisite for occurrence of the precipitation that was observed there. Heat budgets have shown that the development of a heat sink over the East Asian continent was remarkable and its thermal contrast relative to the neighboring seas was the important forcing factor for the winter monsoon activity. The simulation also indicated that the significant differences in circulation patterns and rainfalls during the winters of 1997/98 and 1998/99 were affected by cold and warm ENSO events, respectively. The above analysis demonstrated the model＇s ability to simulate the East Asian winter monsoon.     

东亚地区一次切断低压引起的平流层、对流层交换数值模拟研究

用中尺度模式(MM5)模拟研究东亚地区(网格中心45°N,120°E)一次强切断低压过程(2000年4月8日～12日)引起的平流层、对流层交换.用Wei公式计算此次过程由平流层到对流层的净交换量为5.0×1014 kg,平均交换通量为-0.72×10-3 kg m-2 s-1.地面锋与高空锋的相互作用,在急流入口处和高空锋区出现对流层顶折叠,并引起平流层、对流层物质交换,其中空气的水平运动起主要作用.利用历史天气图统计东亚地区(20～70°N,80～180°E)切断低压的年平均个数为60,占北半球极区类型切断低压的52%.由此,推断东亚地区的平流层、对流层交换对整个北半球的平流层、对流层交换贡献很大.     

梅雨期及其前后东亚地区的径向环流结构

本文分析了1983年江淮流域入梅前、梅雨期以及出梅后东亚地区各期平均的径向环流结构及其演变特征。在不同时期，印度热带季风环流和东亚热带及副热带季风环流具有显著差异。研究指出，江淮流域梅雨是亚洲夏季三个季风系统相互作用的结果，是东亚副热带季风系统中径向经向环流上升支中的产物，同时又与其它两个季风系统密切相关，梅雨结束则与印度热带季风环流减弱南撤、西太平洋高压加强西伸、东亚副热带季风环流北上有关。     

华北和西北区干湿年间水汽场及东亚夏季风的对比分析

为了更好地理解华北及西北地区的夏季降水气候，我们利用NCEP的再分析格点资料等，对华北和西北两区干，湿年（月）的水汽场及夏季风状况作了对比分析，主要结论是：（1）近50年来华北和西北区东部明显干旱化，这可能与同期内东亚夏季风强度趋弱，大气可降水量逐渐减少有关；（2）两地区干，湿年（月）间气柱可降水量差别明显；（3）两地区干，湿年（月）的夏季风，水汽输送通道的位置及强度，以及水汽通量的辐散辐合情况均不同；（4）高原与太平洋间的海陆温差指数及东亚夏季风指数（SMI）对表征东亚夏季风的季节变化及夏季风强度的年际变化有一定的能力，冬春季高原与太平洋间的海陆温差对其后东亚夏季风的强弱及西北和华北区的干湿状况有部分指示意义；作西北区夏季降水预报时要注意四川盆地的水汽场及广元－汉中一带，以及闽，台和两广的水汽输送状况。     

Simulation of Tropospheric Ozone with MOZART-2： An Evaluation Study over East Asia

Climate changes induced by human activities have attracted a great amount of attention. With this, a coupling system of an atmospheric chemistry model and a climate model is greatly needed in China for better understanding the interaction between atmospheric chemical components and the climate. As the first step to realize this coupling goal, the three-dimensional global atmospheric chemistry transport model MOZART-2 (the global Model of Ozone and Related Chemical Tracers, version 2) coupled with CAM2 (the Community Atmosphere Model, version 2) is set up and the model results are compared against observations obtained in East Asia in order to evaluate the model performance. Comparison of simulated ozone mixing ratios with ground level observations at Minamitorishima and Ryori and with ozonesonde data at Naha and Tateno in Japan shows that the observed ozone concentrations can be reproduced reasonably well at Minamitorishima but they tend to be slightly overestimated in winter and autumn while underestimated a little in summer at Ryori. The model also captures the general features of surface CO seasonal variations quite well, while it underestimates CO levels at both Minamitorishima and Ryori. The underestimation is primarily associated with the emission inventory adopted in this study. Compared with the ozonesonde data, the simulated vertical gradient and magnitude of ozone can be reasonably well simulated with a little overestimation in winter, especially in the upper troposphere. The model also generally captures the seasonal, latitudinal and altitudinal variations in ozone concentration. Analysis indicates that the underestimation of tropopause height in February contributes to the overestimation of winter ozone in the upper and middle troposphere at Tateno.     

RegCM3对东亚环流和中国气候模拟能力的检验

使用RegCM3区域气候模式,嵌套ERA40再分析资料,对东亚地区进行了15年（1987～2001年）时间长度的数值积分试验,分析了模式对东亚平均环流及中国地区气温和降水的模拟。结果表明,模式对东亚平均环流的特征和中国地区降水、地面气温的年、季地理分布和季节变化特征均具有一定的模拟能力,对气温和降水年际变率的模拟也较好。此外模式模拟在测站稀少地区,可以提供局地如降水分布更可靠的信息。模式对气温的模拟存在1-3℃的系统性冷偏差;对中国地区降水地理分布的模拟也存在一定偏差,如对年平均降水的模拟中,降水最大值位置与观测有一定差距,特别是对冬季降水中心的模拟存在较大偏差。模式模拟的夏季降水,在中国北方地区总体偏大100-200 mm,南方总体偏小100-200 mm。模式对地面气温的模拟效果好于降水。