Atmospheric turbidity at athens observatory

Summary In this study, values of the Ångström turbidity coefficient () determined from Solar radiation observations at the National Observatory of Athens over the period 1955–1972 are analysed. Mean daily turbidity lies between 0.020–0.100. Turbidity is higher in summer than in winter. The main factor determining the turbidity is the air mass type. The scavenging by rainfall probably has a considerable effect in determining this distribution. There is some evidence of a trend of increasing turbidity during the period.     

太阳风引起的地磁场扰动的系统辨识

本文利用最小二乘非参数辨识,在线性时不变假设下,对由太阳风变化引起的地磁场扰动进行了研究.用这种方法得到的脉冲响应函数给出了地磁层对太阳风变化响应的宏观外部描述,同时还得到了较好的地磁扰动预报结果.本文不仅对单输入单输出系统（SISO系统）进行了分析,而且也对多输入单输出系统（MISO系统）进行了讨论.     

100—200km热层大气光电离率及电子密度剖面对太阳活动的响应

本文利用新的太阳EUV辐射资料、中性大气结构模式及大气成分的吸收及电离特性,计算了100—200km大气的光电离率随高度、太阳天顶角及太阳活动的变化,求得了E-F_1谷的变化特征;利用完整的光化模式求得了电子密度随太阳天顶角的变化及对太阳活动的响应,并与IRI模式作了比较.结果表明,1.太阳活动指数与光电离率间的相关关系一般为正,但在一定的高度范围内,或在天顶角大于临界值X_(cr)=60°时,两者之间可出现负相关;2.太阳活动明显地影响E-F_1谷高与谷厚,当天顶角不变时,谷高与谷厚均与太阳活动成正相关;3.本模式与IRI间的偏差因子明显随高度及太阳天顶角而变化.     

太阳风引起的地磁扰动的参数辨识

作为太阳风引起的地磁扰动的系统辨识一文的姊妹篇,本文利用参数系统辨识方法,对太阳风-磁层耦合系统做了进一步的探讨.根据地磁扰动机制的理论研究,地磁扰动被认为是太阳风能量耦合进入磁层以及由此引起的一系列磁层内能量的输运和耗散的结果.在此基础上,对太阳风-磁层系统的非线性情况进行了讨论,建立了D_st指数与太阳风参量的非线性函数关系,给出了由此得到的地磁扰动计算结果.同时还利用1967年2月3-12日和1980年12月16-23日的两次事件,对已得到的函数关系进行了验证和讨论.验证结果不仅对模型的合理性、普适性做了很好的说明,也表明这种非线性函数关系作为定量的地磁预报模型,具有一定的可信度和实用性.     

Solar UV variability: Effects on stratospheric ozone,trace constituents and thermal structure

The effect of long-term (11-year solar cycle) solar UV variability on stratospheric chemical and thermal structure has been studied using a time-dependent one-dimensional model. Previous studies have suggested substantial variations in local and total ozone, and in stratospheric thermal structure from solar minimum to solar maximum. It is shown here that significant variations also occur in some of the trace constituents. Members of the HO _x family and N₂O exhibit the largest variations, and these changes, if detected, may provide additional means of verifying the presence of solar UV variability and its effects. Some of the species show large phase differences with the assumed solar flux variation. The role of chemical and transport time constants on the time variations of the trace species is examined. Comparisons with reported ozone and temperature data show reasonable agreement for the period 1960 to 1972.     

Remote sensing of the middle atmospheric aerosol

Summary This article analyzes the nature of the aerosol information that current or planned spacecraft measurements could contribute toward the required input data for studies of natural anthropogenic influences on the middle atmosphere, and their consequent effects on our weather and climate. The analysis is conducted with particular reference to the solar occultation sounding technique as applied by the SAGE I experiment on the Atmospheric Explorer Mission B spacecraft. Its conclusions should prove to be of use in both the interpretation of the SAGE I data, and in the design of the follow-on mission on the Earth Radiation Budget satellite.Our analysis shows, in particular, that further studies are required in: the choice and number of sounding channels; the data taking sequence in relation to the atmospheric regions probed; the accuracy and vertical resolution of the atmospheric profiling, and their dependence on both the instrument/spacecraft parameters and the data inversion techniques; and the data reduction procedures. Neither of the selected channels is in a one-to-one relationship with an atmospheric constituent; hence, unless further assumptions are introduced, inversion techniques based on such a property are not applicable. The aerosol wavelengths are not satisfactory as they are only sensitive to the large size tail of the aerosol size distribution rather than to the predominant sizes; for these, UV wavelengths would be required. Owing to the change of the Sun's shape due to atmospheric refraction as the Sun either sets or rises, the higher altitudes will be scanned fewer times than the lower altitudes. Also, because transmission approaches rapidly unity above 40 km, the same high altitudes are more sensitive to measurement errors-errors that will propagate to lower altitude determinations when inverted profiles are reconstructed from the top of the atmosphere. These two factors, combined with the small air mass values at the high altitudes, are the cause of the mathematical ill-conditioning of the inversion problem. They point toward the need for a data-taking sequence strategy that would trade off between data storage and transmission constraints, larger accuracy at the high altitudes, and proper division of the atmosphere in order to overcome the ill-conditioning. Likewise, and as a result of the above considerations, there is a need for a detailed trade off study between data accuracy and vertical resolution of the reconstructed profiles. This should take into account the seasonal and geographical variations in the distribution of atmospheric constituents, as well as a representative statistical set at any given location and time, appropriate error measures and their vertical profiles, and several inversions utilizing as initial guesses profiles that depart from the true ones.It is also shown that the aerosol and ozone number densities cannot be recovered simultaneously without introducing some formula for the aerosol extincition or assumptions on the form of the aerosol size distribution. This problem is not resolved by the addition of sounding channels because each such channel introduces an additional unknown aerosol extinction. Thus, one is led to a separate rather than a simultaneous determination of the various constituents by resorting to complementary measurements. For a future experiment, it is suggested to determine the ozone separately from measurements at a close pair of appropriate wavelengths between which the aerosol extinction varies slowly whereas that of ozone exhibits a rapid variation. A similar technique could also be used for the separate determination of NO₂. The relaxation-type of inversion suggest byChu andMcCormick (1979) does not seem to be appropriate because each channel is not sensitive selectively to an individual constituent, the aerosol channels are not sensitive to the important sizes in the distribution, and the sensitivity of the channels to the constituents of interest varies greatly with altitude.In the retrieval of the vertical profiles, the cause of the ill-conditioning of the inversion is identified. Two approaches are suggested for overconing this problem: (i) build the profile starting from the top of the atmosphere (forward procedure) but with an initial layer of sufficient air mass, or preferably (ii) reconstruct the profile from the lowest altitude reached (backward procedure) with a renormalization at the top of the atmosphere. In this process, the minimization search method (Fymat, 1976) would appear to be a better technique than the onion-peeling technique, as demonstrated byMill andDrayson (1978).In order to maximize the scientific return of SAGE I, a data inversion procedure is proposed. It assumes that (i) there are no aerosols above 25 km, and no NO₂ below this altitude (as suggested byChu andMcCormick, 1979), (ii) below 25 km, ozone (and NO₂, if present) could be determined separately, and (iii) the aerosol has a known refractive index at all wavelengths of interest, is assumed to be spherical (or describable in terms of equivalent spheres), and the minimum and maximum radii of its size distribution are known a priori. Under these assumptions, it is possible to retrieve the neutral density, NO₂ and O₃ profiles above 25 km, by either the forward or the backward procedure described above. Taking into consideration the power law variation of the air density with altitude, it is further possible to reconstruct the corresponding profiles at all the lower altitudes from the determinations in the altitude range 30–40 km. Below 25 km, the four SAGE I channels would then all become available for the aerosol inversion. While the profile reconstruction could proceed as for the higher altitudes, the aerosol inversion at each individual altitude presents problems of its own. Results of numerical experiments for aerosol inversion using all four SAGE wavelengths and seven different inversion routines are presented. If good a priori information is available on the sought size distribution solution, reasonably satisfactory inversions can be performed (see line 1 of Table 2, and Fig. 3c and 3d). However, in the absence of such information, there are as many solutions as inversion methods tried, in complete conformity with the well-known ill-conditioning of the problem. Among methods providing physically meaningful solutions, no method could be singled out as preferable to the others. In these inversions, the data were assumed to be exact, and 99% of the distribution were used. Under different conditions, the nonuniqueness of the inversion would be further compounded.Lastly, based on the present study, a strategy is suggested for the design and data interpretation of a follow-on SAGE-type experiment. Considering the important advantages to this problem presented by forward scattering, as demonstrated byFymat andMease (1978), a composite (extinction-forward scattering) experiment is recommended for the future experiments.Invited article for the Special Issue The Middle Atmosphere, Journal of Pure and Applied Geophysics.Supported by NASA Contract NAS 7-100 with the Jet Propulsion Laboratory, sponsored by the Offices of Planetary Atmospheres and Earth Applications. JPL Atmospheres Publication No.     

A contour-based topographic model for hydrological and ecological applications

A digital model for discretizing three-dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described. From this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area, element area, slope, and aspect. This form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon. The model therefore has wide potential application for representing the three-dimensionality of natural terrain and water flow processes in the fields of hydrology, sedimentology, and geomorphology. Three example applications are presented and discussed. They are the prediction of zones of surface saturation, the prediction of the distribution of potential daily solar radiation, and the prediction of zones of erosion and deposition in a catchment.     

VIRGO: Experiment for helioseismology and solar irradiance monitoring

The scientific objective of the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) is to determine the characteristics of pressure and internal gravity oscillations by observing irradiance and radiance variations, to measure the solar total and spectral irradiance and to quantify their variability over periods of days to the duration of the mission. With these data helioseismological methods can be used to probe the solar interior. Certain characteristics of convection and its interaction with magnetic fields, related to, for example, activity, will be studied from the results of the irradiance monitoring and from the comparison of amplitudes and phases of the oscillations as manifest in brightness from VIRGO, in velocity from GOLF, and in both velocity and continuum intensity from SOI/MDI. The VIRGO experiment contains two different active-cavity radiometers for monitoring the solar constant, two three-channel sunphotometers (SPM) for the measurement of the spectral irradiance at 402, 500 and 862 nm, and a low-resolution imager (LOI) with 12 pixels, for the measurement of the radiance distribution over the solar disk at 500 um. In this paper the scientific objectives of VIRGO are presented, the instruments and the data acquisition and control system are described in detail, and their measured performance is given.died 13 October 1994     

Hype among low-carbon technologies: Carbon capture and storage in comparison

Carbon dioxide capture and storage (CCS) technology has become a crucial part of climate change mitigation strategies around the world; yet its progress has been slow. Some have criticised CCS as a distracting hype, even as mainstream support continues. This article adapts the literature on technological hypes to develop a framework suitable for technologies with limited media/public exposure, such as CCS. It provides a qualitative context and analyses seven quantitative indicators of hype that are largely internal to the CCS technology regime. Throughout, the article contrasts results for CCS with those of comparable technologies. The main findings, which support the view that CCS has been hyped, are as follows. “Expectations” mounted rapidly in the form of project announcements for electricity applications of CCS and deployment forecasts in influential reports. However, announcements soon plummeted. “Commitments” remained high, nonetheless, judging by allocations in public budgets and number of peer-reviewed publications. Meanwhile, “outcomes”—in terms of patents, prototypes and estimated costs—reveal few if any improvements for CCS. Considering these findings and the characteristics of CCS, its development is likely to be more difficult than initially expected. Accordingly, this article calls for decisively prioritising CCS for industrial and, potentially, bioenergy uses. Coal- and gas-fired power plants may be replaced by non-CCS technologies, so power CCS development is far less pressing.     

菏泽冬季日光温室内最低气温预测方法的对比研究

利用2012/2013年冬季菏泽巨野日光温室内外的逐日平均气温、最高气温、最低气温、相对湿度、日照时数和最大风速等气象观测资料,采用相关分析法确定了影响温室内最低气温的关键气象因子,采用逐步回归法和主成分分析法分别建立温室内最低气温预报模型,并用2013/2014年冬季的气象数据检验评价两种预报模型的差异。结果表明:(1)温室内最低气温与当天温室内外及前1 d温室内外的气温、相对湿度、日照时数等相关性比较显著。(2)两种方法建立的预报模型均通过了α=0.01的显著性检验,逐步回归法所建预报模型得到的整个冬季预测值与实测值的相关系数为0.82,平均绝对误差仅为0.9℃,平均相对误差仅为9%;而主成分分析法所建的预报模型得到的整个冬季预测值与实测值的相关系数为0.58,平均绝对误差为1.8℃,平均相对误差为15%。由此表明,用逐步回归法所建的温室内最低气温预报模型的准确度高于主成分分析法,可满足预测冬季温室内最低气温的业务需求。