用选支CO激光研究水汽的共振吸收

用选支CO激光对大气中水汽的共振吸收特性进行了实验研究.本文简述了实验装置和实验方法,给出了水汽v_2带中某些谱线的共振吸收系数、谱线半宽度以及压力加宽效应等实验结果.     

选支CO激光86条发射谱线大气透过率的研究

本文给出了用实验方法得到的5.3—6.3微米范围内CO激光的86条谱线大气衰减系数的研究结果,简单地介绍了实验装置并对结果进行了讨论。分析表明,这一范围内的激光谱线在大气传输过程中主要受到水汽的衰减。各谱线大气衰减系数的实验值和相应的计算值之间存在着不同程度的差异,是由于水汽的共振吸收频率和激光发射频率之间的差异以及计算时采用Lorentz线型所引起的。在用CO激光监测大气微量气体或污染气体时,必须根据实际大气状况,进行必要的水汽订正。     

A STUDY ON NO AND NO_2 ABSORPTION PROPERTIES BY USING LINE-TUNABLE CO LASER

The absorption properties of NO in 5.2 μm band and NO2 in 6.2 μm band are measured for some definite wavelengths by using line-tunable CO laser and long-path absorption cell. The absorption coefficients for 49 CO laser wavelengths are given and variations of absorption withpartial and total pressures are analysed. Furthermore, the experimental errors and the interference of water vapour with the absorption at definite laser lines are also discussed.     

大气二氧化碳对CO2激光辐射各谱线的吸收

本文给出了大气二氧化碳对CO_2激光辐射各谱线吸收的计算公式,并利用标准大气资料计算了各谱线的吸收值。发现在P支谱线中,P(16)线吸收最大;在R支谱线中,R(16)线为最大。当转动量子数J大于或小于16时,吸收值随J值的增大或减小几乎成指数减小。为了验证计算公式的可靠性,在实验室中进行了模拟大气测量,其测量结果和理论计算结果具有较好的一致性。     

温室气体吸收带重叠对CO2红外辐射效应的影响

利用精确的逐线积分模式,研究了大气主要温室气体H2O、CO2、O3、N2O和CH4吸收带重叠对红外冷却率的影响。同时,通过CO2浓度加倍的敏感性试验,详细讨论了重叠效应对CO2辐射效应的影响。结果表明：气体吸收带重叠对大气红外辐射计算具有重要的影响。在这5种大气主要的吸收气体中,N2O和CH4的重叠效应对总冷却率影响很小,在实际应用中可以忽略两者的重叠作用,采用近似方法处理其贡献。重叠效应对CO2辐射效应影响的总趋势是减弱由于其浓度增加而导致的温室效应的增强,主要贡献来自于CO2 15 μm带的两翼,以及以960 cm-1和1064 cm-1为中心的次级弱吸收区。在垂直方向上,重叠效应主要表现在减弱了地表大气的增温强度,并使对流层大气由原来的冷却作用转变为增暖作用,而对平流层大气的影响很小。此外,由于大气H2O含量的变化,重叠效应还表现出明显的季节性和纬度变率。     

CO2激光辐射谱线的大气衰减特性

我们于1986年8月在成都市实地测量了CO_2激光辐射00°l—10°0和00°1—02°0振动带内40条谱线在大气中的衰减。文中给出了各谱线衰减系数的一般值并描述了衰减特征。在八月份成都地区的特定条件下,水蒸汽的吸收和气溶胶粒子的吸收与散射构成了衰减的主要部分。测得的各谱线的衰减系数可为CO_2激光的大气应用提供有益的参考。     

膜基-气体吸收耦合分离混合气中CO2性能评价

在膜基-气体吸收耦合实验装置上,评价了疏水性PP(聚丙烯)微孔膜,活化MDEA(N-甲基二乙醇胺)溶液分离混合气中CO2传质性能,研究了气液流速、吸收剂和混合气的浓度等因素对总传质系数的影响,采用阻力层关联方程模型预测总传质系数Kov值.结果表明:活化MDEA溶液能提高总传质系数Kov值,模型的计算值和实验值符合较好.     

海洋对人为CO2吸收的三维模式研究

文中用包含海洋化学过程和一个简单生物过程的三维碳循环模式模拟了海洋对大气CO2的吸收,并分析了碳吸收的纬度分布。模拟工业革命以来海洋对大气CO2的吸收表明:海洋碳吸收再加上大气CO2的增加只占由化石燃料燃烧、森林砍伐和土地利用的变化而释放到大气中的CO2的2/3。1980～1989年期间海洋年平均吸收2.05GtC。海洋人为CO2的吸收有明显的纬度特征。模式计算的海洋CO2的吸收在总量与纬度分布上与观测结果比较相符。     

用非色散红外气体分析仪进行大气CO2本底浓度的测量

按WMO关于开展全球CO2监测的要求，在对引进设备进行改进的情况下，建立了我国开展大气CO2本底浓度连续测量的红外气体分析测量系统及有关方法。系统的测量精度优于0.1ppm，完全满足全球本底测量的要求，并具有较好的国际可比性。在此基础上，首次取得了我国大陆上空大气CO2的本底浓度资料。     

AN EXPERIMENTAL STUDY ON ABSORPTION PROPERTIES OF NO, N0_2, NH_3, CO_2 AND H_2O BY USING LINE-TUNABLE CO LASER

Measurements of absorption properties of some gases in the atmosphere were made by using CO line-tunable laser. Experimental equipment and method are briefly described. Absorption coefficients of NO, NO2, NH3, CO2 and H2O at some definite laser wavelengths are given, and variations of absorption properties with both partial and total pressures are discussed.     

A study on NO and NO2 absorption properties by using line-tunable CO laser

The absorption properties of NO in 5.2 μm band and NO2 in 6.2 μm band are measured for some definite wavelengths by using line-tunable CO laser and long-path absorption cell. The absorption coefficients for 49 CO laser wavelengths are given and variations of absorption withpartial and total pressures are analysed. Fur-thermore, the experimental errors and the interference of water vapour with the absorption at definite laser lines are also discussed.     

An experimental study on absorption properties of NO,NO2, NH3, CO2 and H2O by using line-tunable co laser

Measurements of absorption properties of some gases in the atmosphere were made by using CO line-tunable laser. Experimental equipment and method are briefly described. Absorption coefficients of NO, NO2, NH3, CO2 and H2O at some definite laser wavelengths are given, and variations of absorption properties with both partial and total pressures are discussed.     

Atmospheric NO2 concentration measurements using differential absorption lidar technique

Using the Differential Absorption Lidar (DIAL) technique, two types of approaches, namely, reflection from retroreflector/topographic target and backscatter from atmosphere, are available for studying remotely the atmos-pheric NO2 concentration. The Argon ion lidar system at the Indian Institute of Tropical Meteorology (IITM), Pune, India has been used for the measurements by following both the path-averaged and range-resolved ap-proaches. For the former, a topographic target (hill) is used for determining path-averaged surface concentration. In the latter, spectral properties of atmospheric attenuation is used for making range-resolved measurements in the sur-face layer. The results of the observations collected by following both approaches are presented. The average surface NO2 concentration was found to vary between 0.01 and 0.105 ppm and the range-resolved measurements exhibited higher values suggesting treatment of the lidar data for scattering and extinction effects due to atmospheric aerosols and air molecules, and atmospheric turbulence. Certain modifications that arc suggested to the experimental set-up, data acquisition and analysis to improve the measurements are briefly described.     

二氧化碳红外吸收带透过率的计算

本文较简单而系统地说明了大气中CO_2及类似于CO_2的线形分子的红外吸收带透过率公式及计算方法。在不伤害物理本质的前提下采用分子光谱模型处理。在计算P、R两支谱线的吸收时,采用艾尔萨斯模型并加上弱谱线吸收订正。当有Q支谱线时则在靠近Q支吸收有影响的波段计及Q支谱线的吸收,对它也采用相应的模型处理。     

Estimates of the Climate Response to Aircraft CO2 and NO x Emissions Scenarios

A combination of linear response models is used to estimate the transient changes in the global means of carbon dioxide (CO₂) concentration, surface temperature, and sea level due to aviation. Apart from CO₂, the forcing caused by ozone (O₃) changes due to nitrogen oxide (NO_x) emissions from aircraft is also considered. The model is applied to aviation using several CO₂ emissions scenarios, based on reported fuel consumption in the past and scenarios for the future, and corresponding NO_x emissions. Aviation CO₂ emissions from the past until 1995 enlarged the atmospheric CO₂ concentration by 1.4 ppmv (1.7% of the anthropogenic CO₂ increase since 1800). By 1995, the global mean surface temperature had increased by about 0.004 K, and the sea level had risen by 0.045 cm. In one scenario (Fa1), which assumes a threefold increase in aviation fuel consumption until 2050 and an annual increase rate of 1% thereafter until 2100, the model predicts a CO₂ concentration change of 13 ppmv by 2100, causing temperature increases of 0.01, 0.025, 0.05 K and sea level increases of 0.1, 0.3, and 0.5 cm in the years 2015, 2050, and 2100, respectively. For other recently published scenarios, the results range from 5 to 17 ppmv for CO₂ concentration increase in the year 2050, and 0.02 to 0.05 K for temperature increase. Under the assumption that present-day aircraft-induced O₃ changes cause an equilibrium surface warming of 0.05 K, the transient responses amount to 0.03 K in surface temperature for scenario Fa1 in 1995. The radiative forcing due to an aircraft-induced O₃ increase causes a larger temperature change than aircraft CO₂ forcing. Also, climate reacts more promptly to changes in O₃ than to changes in CO₂ emissions from aviation. Finally, even under the assumption of a rather small equilibrium temperature change from aircraft-induced O₃ (0.01 K for the 1992 NO_x emissions), a proposed new combustor technology which reduces specific NO_x emissions will cause a smaller temperature change during the next century than the standard technology does, despite a slightly enhanced fuel consumption. Regional effects are not considered here, but may be larger than the global mean responses.     

Comparison of eddy-covariance measurements of CO2 fluxes by open- and closed-path CO2 analysers

Eddy fluxes of CO₂ estimated using a sonic anemometer and a closed-path analyser were, on average, 16% lower than those obtained with the same anemometer and an adjacent open-path CO₂ analyser. Covariances between vertical windspeed and CO₂ density from the closed-path analyser were calculated using data points for CO₂ that were delayed relative to anemometer data by the time required for a parcel of air to travel from the tube inlet to the CO₂ sensor. Air flow in the intake tube was laminar. Densities of CO₂ that had been corrected for spurious fluctuations arising from fluctuations in temperature and humidity were used in the flux calculations. Corrections for the cross-sensitivity of CO₂ analysers to water vapour were also incorporated. Spectral analysis of the corrected CO₂ signal from the closed-path analyser showed that damping of fluctuations in the sampling tube at frequencies f > 0.1 Hz caused the apparent loss in flux. The measured losses can be predicted accurately using theory that describes the damping of oscillations in a sampling tube. High-frequency response of the closed-path system can be improved substantially by ensuring turbulent flow in the tube, using a combination of high volumetric flow rate and small tube diameter. The analysis of attenuation of turbulent fluctuations in flow through tubes is applicable to the measurement of fluxes of other minor atmospheric constituents using the eddy covariance method.     

Fourier transform measurement of NO2 absorption cross-section in the visible range at room temperature

New laboratory measurements of NO₂ absorption cross-section were performed using a Fourier transform spectrometer at 2 and 16 cm^-1 (0.03 and 0.26 nm at 400 nm) in the visible range (380–830 nm) and at room temperature. The use of a Fourier transform spectrometer leads to a very accurate wavenumber scale (0.005 cm^-1, 8×10^-5 nm at 400 nm). The uncertainty on the new measurements is better than 4%. Absolute and differential cross-sections are compared with published data, giving an agreement ranging from 2 to 5% for the absolute values. The discrepancies in the differential cross-sections can however reach 18%. The influence of the cross-sections on the ground-based measurement of the stratospheric NO₂ total amount is also investigated.