兰州冬季气溶胶的短波加热效应及其对混合层发展的影响

综合考虑无云天气条件下，气溶胶和大气中各种吸收气体对太阳辐射的影响，建立了一个气溶胶大气的短波加热率模式，研究了兰州冬季气溶胶的短波加热效应。计算结果表明:气溶胶吸收太阳辐射而加热大气的作用是显著的。在上述工作的基础上，建立了一个完全闭合的混合层发展模式，利用数值方法探讨了气溶胶的辐射效应对混合层发展的影响。计算发现大气中气溶胶的增加会抑制混合层的发展，使混合层内的平均位温减小。     

太阳短波辐射分光谱计算模式

本文采用太阳短波辐射分光谱模式计算了我国太阳辐射收支各分量。模式中主要考虑及计算了大气中各种成份在不同谱区对太阳辐射的吸收和衰减作用。如水汽、均匀混和气体的红外吸收，紫外和可见光区的臭氧吸收、雷利散射及大气气溶胶的削弱作用等。给出了大气中各种成份在不同波段对太阳辐射的削弱。并且分析了我国太阳辐射收支各分量1月、7月的分布特征。模式误差在4％～10％，比较理想。为无辐射观测的高原、沙漠、海洋等地区提供了一种较好的计算方法。     

云层与气溶胶对大气吸收太阳辐射的影响

云通过辐射过程对地气系统的能量平衡起着特别显著的调节作用 ,是影响天气、气候以及全球变化的重要因子。近年来 ,有云大气对太阳短波辐射的“异常吸收”又成为云—辐射研究中的一个争论热点。有云大气的短波吸收受到多种因素的影响 ,关于这方面的研究还不够充分。本文通过计算 ,从理论上探讨了若干因素的组合对大气吸收的综合影响。在计算中 ,同时考虑了不同太阳辐射波段、不同太阳入射天顶角、不同云顶高度以及不同下垫面的影响 ,并考虑了包含大气分子、气溶胶和云滴的吸收与散射 ,以及在近红外波段大气自身的热辐射等过程 ,阐明了云与气溶胶在不同波段对大气吸收太阳辐射的影响。     

气溶胶与气候

气溶胶粒子对气候系统的辐射平衡有重要影响。气溶胶对气候的影响可分为两大方面,即直接影响和间接影响。直接影响指大气中的气溶胶粒子吸收和散射太阳辐射和地面射出长波辐射从而影响地－气辐射收支。模式计算表明,人类活动引起大气气溶胶增加倾向于使地球表面降温,工业化以来,气溶胶增加引起的地面变冷趋势可部分抵销温室气体增加引起的地表温度上升。气溶胶对气候的间接影响是指气溶胶浓度变化会影响云的形成,而云的变化反过来对气候有巨大影响,这方面至今还没有定量结果。       

烟雾层的长波辐射效应以及对边界层温度层结的影响

本文利用一个简化的长波辐射方案，计算了兰州城市烟雾层大气的辐射效应．计算表明:烟雾层气溶胶增加了到达地面的大气逆辐射和气层的冷却率，平均污染状况时，增加量分别为15．2％和0．073℃／h．与烟雾层对太阳辐射吸收加热率相比，冷却率量值较小，但对全天边界层能量平衡所起作用不可忽略．对比分析了兰州和郊区夜晚的平均温度廓线演变情况，可以看出烟雾层长波辐射效应增加了低层大气中上部的冷却．     

太阳辐射在大气中的衰减

本文根据世界气象组织仪器和观测方法委员会第八届会议通过的大气界外的太阳光谱辐照以及最新的臭氧和分子散射的光谱透明系数等资料,计算了各种大气中的太阳辐射强度。分析了减弱太阳直接辐射诸因子的影响。并提出了正确计算水汽吸收辐射量和气溶胶减弱辐射量的方法。同时还建立了便于普遍应用的和具有足够精度的计算太阳辐射强度的简易方法。计算值和实测值比较结果良好。     

微量物质对大气能量收支的影响

地球吸收的太阳辐射是驱动大气运动的初始能源。可以通过几种微量物质和通过海陆表面层来了解大气电磁场到温度场的能量转换。行星或地-气系统中最强烈的吸收发生在近地层。就全球平均而论,大气直接吸收的太阳辐射只占入射辐射的20％。大约51％的太阳辐射是经过地面后间接到达大气的。这部分能量再自然地被分成各种能量通量。水汽、臭氧、CO_2和气溶胶粒子是吸收最有效的微量物质。表1归纳了这些微量物质的一些特性资料。     

平流层大气对太阳辐射能的吸收

本文讨论了如下三个问题:1.设计了一套计算平流层大气对太阳辐射吸收的计算公式。2.讨论了利用平面层大气来代替曲率大气对太阳辐射吸收引起的误差。3.计算了1,7月份太阳对平流层大气的加热。     

污染大气边界层的长波冷却率模式

考虑大气气溶胶在长波窗区的散射和吸收作用以及水汽的连续吸收作用，建立了一个适用于污染大气边界层的长波冷却率模式。计算结果表明：当单位面积气柱中气溶胶含量为７８５．９ｍｇ／ｍ２时，气溶胶的作用可使到达地面的长波向下辐射增大３９Ｗ／ｍ２。在大气窗区，大气气溶胶和水汽的连续吸收对长波冷却率的影响是同等重要的。在水汽含量和气溶胶浓度较大的大气边界层内，水汽连续吸收的冷却率最大时可达１．３Ｋ／ｄ，气溶胶的冷却率最大时可达到１．６６Ｋ／ｄ，二者对长波冷却率的贡献均不容忽视     

大气气溶胶变化对农业影响的研究进展

随着工业化和城市化的迅速发展,大气气溶胶含量和种类明显增加,它们通过直接吸收和反射太阳辐射以及改变其它辐射强迫因子(云、臭氧)的大小间接影响地气系统的能量收支,从而影响气候。气溶胶变化对气候的影响已有较多的研究,而对植被(农业)的影响是一个相对较新的研究领域,文章简要概述了大气气溶胶辐射强迫效应和大气气溶胶对农业的影响研究现状及国内外主要研究成果,并对气溶胶监测方法及模式评估方面可能存在的问题作了简单的分析。     

THE ABSORPTION OF SOLAR RADIATION BY AEROSOL ATMOSPHERE

The two-stream approximation is applied to solve the multiple scattered radiation transfer equationsfor an inhomogeneous aerosol atmosphere.The accurate absorption of water vapor,ozone,carbon dioxideand molecular oxygen is calculated.Calculations have been carried out band by band for the beating rateof atmosphere.The results show that the effect of aerosols on solar heating of the atmosphere is significant.     

东亚地区的大气辐射能的收支(一)——地球和大气的太阳辐射能收支

本文是讨论东亚地区大气辐射能收支研究工作的第一部分,讨论了以下三个问题: (1)本文利用文献[1]的水汽各吸收带的吸收光谱实验资料,求得了一个适合于手算的水汽对太阳辐射的总吸收能量公式(公式(6))。并把式(6)与Mugge—Moller公式进行了比较。 (2)利用公式(6),计算了东亚地区39个测站1,7月自地面到100毫巴各气层对太阳辐射的吸收能量,及其对大气的加温率。本文还进一步考虑了云的订正、大气对地面反射辐射的吸收,而求得了东亚地区对流层大气吸收能量的分布。 (3)利用1958—1960年中国地区的一些地面总辐射和反射率观测资料,以及本文计算的大气中各种吸牧能量,讨论了中国地区行星反射率的分布和地球大气系统中各种太阳辐射能的收支。     

太阳紫外辐射在大气中衰减的探讨

在对北京紫外辐射观测资料分析的基础上,提出了参与光化学反应的物质对太阳紫外辐射能量的吸收作用.计算表明北京地区1990年云天比晴天紫外辐射减少约为21W m-2,此值与CeSS等人的观测结果比较接近.这表明了大气中参与光化学反应的物质对光化辐射能量的吸收基本上等于云对太阳短波辐射的"异常吸收"之值.所以,在辐射传输模式、大气化学模式、气候模式中,应该考虑参与光化学反应的物质对光化辐射能量的吸收作用.     

The effects of the Arctic haze as determined from airborne radiometric measurements during AGASP II

The interaction of the Aretic winter aerosol (Arctic haze) with solar radiation produces changes in the radiation field that result in the enhancement of scattering and absorption processes which alter the energy balance and solar energy distribution in the Arctic atmosphere-surface system. During the second Arctic Gas and Aerosols Sampling Project (AGASP II) field experiment, we measured radiation parameters using the NOAA WP-3D research aircraft as a platform. State-of-the-art instrumentation was used to measure in situ the absorption of solar radiation by the Arctic atmosphere during severe haze events. Simultaneously with the absorption measurements, we determined optical depths, and total, direct, and scattered radiation fields. All optical measurements were made at spectral bands centered at 412, 500, 675, and 778 nm and with a bandpass of 10 nm. With this selection of spectral regions we concentrated on the measurement of the radiative effects of the aerosol excluding most of the contributions by the gaseous components of the atmosphere. An additional measurement performed during these experiments was the determination of total solar spectrum fluxes. The experimentally determined parameters were used to define an aerosol model that was employed to deduce the absorption by the aerosols over the full solar spectrum and to calculate atmospheric heating rate profiles. The analyses summarized above allowed us to deduce the magnitude of the change in some important parameters. For example, we found changes in instantaneous heating rate of up to about 0.6 K/day. Besides the increased absorption (30 to 40%) and scattering of radiation by the atmosphere, the haze reduces the surface absorption of solar energy by 6 to 10% and the effective planetary albedo over ice surfaces by 3 to 6%. The vertical distribution of the absorbing aerosol is inferred from the flux measurements. Values for the specific absorption of carbon are found to be around 6 m²/g for externally mixed aerosol and about 11.7 m²/g for internally mixed aerosol. A complete study of the radiative effects of the Arctic haze should include infrared measurements and calculations as well as physics of the ice, snow, and water surfaces.     

NUMERICAL SIMULATIONS OF THE EFFECTS OF AEROSOLS IN THE ATMOSPHERIC BOUNDARY LAYER ON THE CLIMATE*

The climatic effects of the atmospheric boundary aerosols are studied by the use of a three-dimensional climate model.Simulated results show that the climate states both at the surface and in the atmosphere change remarkably when the aerosols with different optical thicknesses and properties are introduced into the atmospheric boundary layer of the model.The aerosols absorb and scatter the solar shortwave radiation,therefore,they reduce the solar energy reaching the ground surface and decrease the surface and the soil temperatures.The temperature in the boundary layer increase because of the supplementary absorption of radiation by the boundary aerosols.In the atmosphere,the temperatures at all isobaric surfaces rise up except for the 100 hPa level.The atmospheric temperatures below the 500 hPa level are directly influenced by the boundary aerosols,while the atmospheric temperatures above the 500 hPa level are influenced by the heating due to convective condensation and the changes in the vertical motion field.Cyclonic differential circulations appear over the desert areas at the low levels,and anticyclonic differential circulations exist at the upper levels in the horizontal flow fields.The vertical motions change in correspondence with the differential circulations.The changes in precipitation are directly related to that of vertical motions.The mechanisms of climate effects of the boundary aerosols are also discussed in this paper.     

NUMERICAL SIMULATIONS OF THE EFFECTS OF AEROSOLS IN THE ATMOSPHERIC BOUNDARY LAYER ON THE CLIMATE

The climatic effects of the atmospheric boundary aerosols are studied by the use of a three-dimensional climatemodel.Simulated results show that the climate states both at the surface and in the atmosphere change remarkably whenthe aerosols with different optical thicknesses and properties are introduced into the atmospheric boundary layer of themodel.The aerosols absorb and scatter the solar shortwave radiation,therefore,they reduce the solar energy reachingthe ground surface and decrease the surface and the soil temperatures.The temperature in the boundary layer increasesbecause of the supplementary absorption of radiation by the boundary aerosols.In the atmosphere,the temperatures atall isobaric surfaces rise up except for the 100 hPa level.The atmospheric temperatures below the 500 hPa level aredirectly influenced by the boundary aerosols,while the atmospheric temperatures above the 500 hPa level are influencedby the heating due to convective condensation and the changes in the vertical motion field.Cyclonic differential circula-tions appear over the desert areas at the low levels,and anticyclonic differential circulations exist at the upper levels inthe horizontal flow fields.The vertical motions change in correspondence with the differential circulations.The changesin precipitation are directly related to that of vertical motions.The mechanisms of climate effects of the boundaryaerosols are also discussed in this paper.     

Aerosol modulation of atmospheric and surface solar heating over the tropical Indian Ocean

The major finding of this study is that aerosols over the tropical Indian Ocean enhance clear sky atmospheric solar heating significantly and decrease the surface solar heating by even a larger amount. The results presented here are based on aerosol chemical, microphysical, and optical and radiometric data collected at the island of Kaashidhoo (4.97°N, 73.47°E) during February and March of 1998, as part of the first field phase of the Indian Ocean experiment (INDOEX). The aerosol optical properties were integrated with a multiple scattering Monte Carlo radiative transfer model which was validated at the surface with broadband flux measurements and at the top of the atmosphere (TOA) with the clouds and earth's radiant energy system (CERES) radiation budget measurements. We consider both externally and internally mixed aerosol models with very little difference between the two models in the estimated forcing. For the February–March period, the aerosols increase the monthly mean clear sky atmospheric solar heating by about 12 W/m²(about 15% of the total atmospheric solar heating) and decrease the sea surface clear sky solar heating by about 16 W/m² with a daily range from 5 to 23 W/m². The net aerosol forcing at the top of the atmosphere is about −4 W/m² with a daily range from −2 to −6 W/m². Although the soot contributes only about 10% to the aerosol optical thickness, it contributes more than 50% to the aerosol induced atmospheric solar heating. The fundamental conclusion of this study is that anthropogenic aerosols over the tropical Indian Ocean are altering the clear sky radiation budget of the atmosphere and surface in a major manner.     

RADIATIVE CHARACTERISTICS OF AEROSOLS AT GOLMUD ON THE TIBETAN PLATEAU

The characteristics of atmospheric aerosols in the Golmud desert over the Tibetan (Qinghai-Xizang) Plateau are investigated using the measurements made during the QXPMEX-79.Using spectroscopic observations at the surface and satellite data,the aerosol optical depth is calculated,from which the aerosol size distribution is worked out by means of an inversion method.The effects of vertical distribution of aerosols on irradiance and heating rate profiles are investigated using radiation models in conjunction with the assumption of three idealized aerosol profiles.The effect of aerosols on solar irradiance at the surface is also investigated and the results are compared with the observations.It is shown that the solar irradiance can be reduced by up to 100 W m^-2 in the presence of aerosols,and the heating rate can be increased by 1 Kd^-1.     

Calculation of solar and thermal radiation absorption in the atmosphere, based on the HITRAN data

Summary Using the HITRAN database from 2003, the absorption of solar and thermal radiation by the atmosphere is calculated. The results are presented in the form of spectral densities of absorption yield of the atmosphere and its components, and fractions of absorbed energy of the solar radiation and thermal radiation in the atmosphere by each of its components separately and together. Finally, the obtained results are discussed in the context of the lately published model of Earth’s radiation budget-MAP 85(4), 275–281 (2004). The shares of atmospheric components in the greenhouse effect and in the absorption of solar radiation are calculated. The percentage contributions of the more important atmospheric components in the greenhouse effect are as follows: clouds 66, water vapor 25, CO₂ 6.7, N₂O 0.7, CH₄ 0.7.     

A Review of Aerosol Optical Properties and Radiative Effects

Atmospheric aerosols influence the earth's radiative balance directly through scattering and absorbing solar radiation, and indirectly through affecting cloud properties. An understanding of aerosol optical properties is fundamental to studies of aerosol effects on climate. Although many such studies have been undertaken, large uncertainties in describing aerosol optical characteristics remain, especially regarding the absorption properties of different aerosols. Aerosol radiative effects are considered as either positive or negative perturbations to the radiation balance, and they include direct, indirect (albedo effect and cloud lifetime effect), and semi-direct effects. The total direct effect of anthropogenic aerosols is negative (cooling), although some components may contribute a positive effect (warming). Both the albedo effect and cloud lifetime effect cool the atmosphere by increasing cloud optical depth and cloud cover, respectively. Absorbing aerosols, such as carbonaceous aerosols and dust, exert a positive forcing at the top of atmosphere and a negative forcing at the surface, and they can directly warm the atmosphere. Internally mixed black carbon aerosols produce a stronger warming effect than externally mixed black carbon particles do. The semi-direct effect of absorbing aerosols could amplify this warming effect. Based on observational (ground-and satellite-based) and simulation studies, this paper reviews current progress in research regarding the optical properties and radiative effects of aerosols and also discusses several important issues to be addressed in future studies.