Constraints on 2-Way Transport across the Arctic Tropopause Based on O3, Stratospheric Tracer (SF6) Ages, and Water Vapor Isotope (D, T) Tracers

Based upon airborne trace gas and isotope observations in the winter months 1991/1992 to1994/1995, transport pathways across the mid-latitude and Arctic tropopause areinvestigated. A powerful set of contrasting transport tracers are examined, such asdeuterated water vapor (HDO) which is shown to trace the passage of water vapor from thetroposphere into the lowermost stratosphere (LS), or the `SF₆ age' defined as theresidence time of an air parcel within the stratosphere since its entry at thetropopause. Cross-tropopause transport in both directions was found near mid-latitudecyclones (at baroclinic flanks of troughs in the polar front), in which about 80% of thestratosphere-to-troposphere flux proceeded along potential temperature ()surfaces of 300 ± 10 K. As these isentropes are the lowest which reach into the LS(in winter), a mixing zone just above the Arctic tropopause (at least 1.5 km thick) isformed. Here, upwelling tropospheric air is mixed with downwelling LS air which isaffected by air from higher altitudes, the surf-zone and the polar vortex. The observedelevated D/H isotope ratio of water vapor within the mixing zone can be explained byinjection of subtropical water vapor that is transported to the tropopause by the warmconveyor belt associated with mid-latitude cyclones. Downward vertical transport ofArctic LS air, which may be influenced by ouflowing chemically disturbed polar vortexair, into the Arctic troposphere was found to be small.     

Weakening of Indian summer monsoon in recent decades

The analysis of 43 years of NCEP-NCAR reanalysis data and station observations reveals the connections between tropospheric temperature variations and the weakening of the Indian summer monsoon circulation. The Indian summer monsoon variation is strongly linked to tropospheric temperature over East Asia, showing significant positive correlations of mean tropospheric temperature with all-Indian summer rainfall and the monsoon circulation intensity. The result shows that Indian summer monsoon circulation underwent two weakening processes in recent decades. The first occurred in circa the mid-1960s, and the other occurred in circa the late 1970s. The finding indicates that the mean tropospheric temperature may play a crucial role in the weakening of the Indian summer monsoon intensity via changing land-sea thermal contrast. The role of the tropospheric temperature contrast between East Asia and the tropical area from the eastern Indian Ocean to the tropical western Pacific is to weaken the Indian summer monsoon circulation.     

MEASUREMENTS AND MODEL SIMULATIONS OF SURFACE OZONE VARIATIONS AT DIFFERENT BACKGROUND CONCENTRATIONS OF THE PRECURSORS*

Ozone photochemical production and loss in very different environments at Waliguan baseline station and Lin'an background station were simulated by using the measurement data and photochemical box model.The results show that net ozone photochemical production rate is negative,about 0.5 ppb/d,at Waliguan baseline sation,because of very low precursor concentrations.But at Lin'an background station,the net photochemical ozone production is positive,about 2-3 ppb/h.which is very closed with the measurement at Lin'an.That means ozone production was controlled by photochemical reactions at Lin'an background station,because of the higher precursor concentrations.The net destruction rate,at Waliguan Mt.,is not large,so that future increase in anthropogenic emission of reactive nitrogen will lead to larger production rates of steady-state O₃ concentration.     

Harmonious Inter-decadal Changes of July–August Upper Tropospheric Temperature Across the North Atlantic, Eurasian Continent,and North Pacific

The authors have developed an integral view of the inter-decadal variability of July–August(JA)tro- pospheric temperature across the entire subtropical Northern Hemisphere.Using reanalysis data and com- plementary balloon-borne measurements,the authors identify one major mode of variability for the period 1958–2001 which exhibits a significant cooling center over East Asia and warming centers over the North Atlantic and North Pacific.The cooling(warming)signals barotropically penetrate through the troposphe...     

Spatial patterns of Tropospheric Biennial Oscillation and its numerical simulation

In order to investigate the spatial patterns of the Tropospheric Biennial Oscillation （TBO） on the global scale, the Climate Prediction Center （CPC） Merged Analysis of Precipitation （CMAP） monthly averaged precipitation and the Climate Diagnostics Center （CDC） monthly outgoing long-wave radiation （OLR） and SST are used in conjunction with TBO bandpass-filtering. The results indicate active biennial variability in the tropical eastern-central Pacific regions. It is evident that observations reflect the biennial component of the ENSO rather than the TBO itself. Since some studies have pointed out that the TBO is a broad-scale phenomenon differing from the ENSO, to investigate the pure TBO the ENSO signal must be excluded. The Scale Interaction Experiment-FRCGC （SINTEX-F） coupled general circulation model （CGCM） developed at Japan Frontier Research Center for Global Change （FRCGC） can capture both the ENSO and the biennial signals. Air-sea interactions in the tropical eastern-central Pacific are decoupled to eliminate the effects of ENSO in a experiment by SINTEX-F and the results show that biennial variability still exists even without ENSO. It seems to mean that the TBO and ENSO are independent from each other. Furthermore, the model results indicate that the two key regions are southwest Sumatra and the tropical western Pacific for the TBO cycle.     

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.     

对流层大气的负熵流和熵产生

将原始熵平衡方程应用于大气系统，详细计算了对流层大气平均状态下的负熵流和熵产生及其各项分量，得出了它们之间的一些数量关系，并应用熵理论初步解释了大气运动的某些规律，对于天气预报和气候变化的研究具有一定参考意义。     

河北平原第四系咸水同位素组成

本文讨论了河北平原地下咸水的同位素组成。并且依据水文地质、水化学和同位素特征将咸水成因分为两种类型,即大陆盐化成因和海水成因咸水。前者δ１８Ｏ＜－７．００‰,δＤ＜－５５．０‰,３６Ｃｌ／Ｃｌ＞５７±９（×１０－１５）,１４Ｃ年龄为１０００～４０００ａ（校正）;后者δ１８Ｏ＞－７．００‰,δＤ＞－５５．０‰,δ３７Ｃｌ值接近海水值,１４Ｃ年龄大于１００００ａ（校正）,咸水中的海水百分比大于３８．０％。     

高精度测定稳定氯同位素的制样方法

以Ｔａｙｌｏｒ和Ｇｒｉｍｓｒｕｄ（１９６９）提出的＾３７Ｃｌ测量的测样原理为基础，介绍了不同地质样品的化学处理方法，研究了ＣＨ３Ｉ的纯化技术，将ＡｇＣｌ转化为ＣＨ３Ｃｌ的过程以及用气相色谱（ＧＣ）法分离ＣＨ３Ｃｌ和ＣＨ３Ｉ的技术。文中详述的制样方法可用来查明近地表地下水和岩石系统中δ＾３７Ｃｌ的天然变化。