Irradiance observations of the 1–8 Å solar soft X-ray flux from goes     

Markus J. Aschwanden 《Solar physics》1994,152(1):53-59

The solar 0.5–8 soft X-ray flux was monitored by the NOAA Geostationary Operational Environmental Satellites (GOES) from 1974 to the present, providing a continuous record over two solar activity cycles. Attempts have been made to determine a soft X-ray (SXR) background flux by subtracting out solar flares (using the daily lowest flux level). The SXR background flux represents the quiescent SXR flux from heated plasma in active regions, and reflects similar (intermediate-term) variability and periodicities (e.g. 155-day period) as the SXR or hard X-ray (HXR) flare rate, although it is determined in non-flaring time intervals. The SXR background flux peaks late in Solar Cycle 21 (2–3 years after the sunspot maximum), similar to the flare rate measured in SXR, HXR, or gamma rays, possibly due the increasing complexity of coronal magnetic structures in the decay phase of the solar cycle. The SXR background flux appears to be dominated by postflare emission from the dominant active regions, while the contributions from the quiet Sun are appreciable in the Solar Minimum only (A1-level). Comparisons with full-disk integrated images from YOHKOH suggest that the presence of coronal holes can decrease the quietest SXR irradiance level by an additional order of magnitude, but only in the rare case of absence of active regions.Presented at IAU Colloquium No. 143, The Sun as a Variable Star: Solar and Stellar Irradiance Variations, Boulder, CO, June 20–25, 1993  相似文献   

Estimating the compensation irradiance in the ocean: The importance of accounting for non-photosynthetic uptake of inorganic carbon     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

The compensation irradiance, the irradiance at which net photosynthesis is zero over a 24-h period, was estimated at station ALOHA (22°45′N, 158°W) from analysis of ¹⁴C uptake rates measured from 8 January 1989 to 13 June 1990 at depths ranging from 5 to 175 m. The estimates were made on the basis of linear regressions of the difference between light bottle and dark bottle ¹⁴C uptake in the light-limited region of the euphotic zone and determination of the depth at which the difference between the uptake rates was zero. About half of the non-photosynthetic ¹⁴C uptake at the compensation irradiance could be attributed to chemolithoautotrophy; the remainder was presumably due to anaplerotic processes. Deriving the compensation irradiance by extrapolating dawn-to-dawn light-bottle uptake above the compensation irradiance to zero resulted in underestimation of the compensation irradiance by a factor of 2. We estimated the compensation irradiance at station ALOHA to be 0.054 mol-photons m⁻² d⁻¹, about 0.11% of surface 400–700 nm radiation and 1% of surface 475-nm (blue) light.  相似文献   

First results of the earth observation Water Cycle Multi-mission Observation Strategy (WACMOS)     

《International Journal of Applied Earth Observation and Geoinformation》2014

Observing and monitoring the different components of the global water cycle and their dynamics are essential steps to understand the climate of the Earth, forecast the weather, predict natural disasters like floods and droughts, and improve water resources management. Earth observation technology is a unique tool to provide a global understanding of many of the essential variables governing the water cycle and monitor their evolution from global to basin scales. In the coming years, an increasing number of Earth observation missions will provide an unprecedented capacity to quantify several of these variables on a routine basis. However, this growing observational capacity is also increasing the need for dedicated research efforts aimed at exploring the potential offered by the synergies among different and complementary EO data records. In this context, the European Space Agency (ESA) launched the Water Cycle Multi-mission Observation Strategy (WACMOS) in 2009 aiming at enhancing, developing and validating a novel set of multi-mission based methods and algorithms to retrieve a number of key variables relevant to the water cycle. In particular the project addressed four major scientific challenges associated to a number of key variables governing the water cycle: evapotranspiration, soil moisture, cloud properties related to surface solar irradiance and precipitation, and water vapour. This paper provides an overview of the scientific results and findings with the ultimate goal of demonstrating the potential of strategies based on utilizing multi-mission observations in maximizing the synergistic use of the different types of information provided by the currently available observation systems and establish the basis for further work.  相似文献   

山区地表太阳辐照度随时空变化的模拟分析     

秦慧平  易维宁  黄红莲  潘邦龙 《武汉大学学报(信息科学版)》2011,(7)

在光学遥感数据的应用过程中,地表太阳辐照度的量化问题对于遥感数据的获取和地表地物特性的反演等工作都是一个非常重要的环节,而地表太阳辐照度的定量计算又依赖于辐射源、目标物和传感器三者之间的几何关系以及目标地物的地表特征。利用山区地表太阳辐照度的计算模型,对不同时间、不同山区地形下的地表太阳辐照度进行了定量模拟,用三维图的方式分析了地表太阳辐照度随时间、地形坡度、坡向的变化规律,为光学遥感中地表太阳辐照度随时空变化的量化关系分析提供了更直观的依据。  相似文献   

Effects of activity complexes and active longitudes on variations in total solar irradiance     

A. V. Mordvinov  R. C. Willson 《Astronomy Letters》2001,27(7):451-454

A numerical technique of time-longitude analysis has been developed by studying the fine structure of temporal variations in total solar irradiance (TSI). This analysis produces maps of large-scale thermal inhomogeneities on the Sun and reveals corresponding patterns of radiative excess and deficit relative to the unperturbed solar photosphere. These patterns are organized in two-and four-sector structures and exhibit the effects of both activity complexes and the active longitudes. Large-scale patterns with radiative excess show a facular macrostructure caused by the relaxation of large-scale thermo-magnetic perturbations and/or energy output due to very large-scale solar convection. These thermal patterns are related to long-lived magnetic fields that are characterized by rigid rotation. The patterns with radiative excess tend to concentrate around the active longitudes and are centered at 103° and 277° in the Carrington system when averaged over the time-longitude distribution of thermal inhomogeneities during activity cycles 21–23.  相似文献   

月球目标监测风云二号静止气象卫星可见光辐射响应变化     

陈林  张鹏  吴荣华  胡秀清  张璐 《遥感学报》2018,22(2):211-219

月球的光度具有纪年级的稳定性,其辐照度可作为可见—近红外光谱辐射基准,基于此的月球辐射定标方法有望成为辐射定标的新方法之一。本文介绍一种利用月球目标作为稳定辐射定标源,结合月球辐照度模型,跟踪风云二号静止气象卫星遥感仪器可见光通道辐射响应变化的方法。通过轨道预报遴选出风云二号E星(FY-2E)的扫描辐射计2010年1月—2014年10月的对月观测数据,经过月球图像提取和筛选、月球照度模型计算、卫星观测月球照度模型计算、星—月—日距离校正等环节处理后,获取了FY-2E扫描辐射计可见光通道的辐射响应变化,并且与深对流云辐射定标方法进行了对比验证。主要结果:(1)利用月球辐射作为基准可有效监测遥感仪器可见光通道的辐射响应变化情况,通过线性回归分析发现FY-2E可见光通道的辐射响应总衰减率是9.2%,年衰减率为1.96%,95%置信区间的不确定度和稳定性指标分别为±0.79%和2.66,其结果与基于深对流云目标监测的仪器辐射响应结果相近;(2)FY-2E可见光通道较低的量化等级(6 bit)、杂散光影响等因素对利用月球进行辐射响应定标和跟踪监测有一定的影响;(3)FY-2E辐射响应除了衰减趋势,还存在周期性震荡的特点。基于月球目标的辐射定标方法能够有效监测卫星的辐射响应衰减,可作为星载遥感仪器辐射响应定标和检验的一种可靠手段,特别是针对卫星全生命周期的历史数据再定标,从而提高辐射定标精度。  相似文献   

Solar Arctic-Mediated Climate Variation on Multidecadal to Centennial Timescales: Empirical Evidence,Mechanistic Explanation,and Testable Consequences     

《自然地理学》2013,34(2):144-184

Soon (2005) showed that the variable total solar irradiance (TSI) could explain, rather surprisingly, well over 75% of the variance for the decadally smoothed Arctic-wide surface air temperature over the past 130 years. The present paper provides additional empirical evidence for this physical connection, both through several newly published high-resolution paleo-proxy records and through robust climate-process modeling outputs. This paper proposes a mechanistic explanation, involving: (1) the variable strength of the Atlantic meridional overturning circulation (MOC) or thermohaline circulation (THC); (2) the shift and modulation of the Inter-Tropical Convergence Zone (ITCZ) rainbelt and tropical Atlantic ocean conditions; and (3) the intensity of the wind-driven subtropical and subpolar gyre circulation, across both the North Atlantic and North Pacific. A unique test of this proposed solar TSI-Arctic thermal-salinity-cryospheric coupling mechanism is the 5- to 20-year delay effect on the peak Atlantic MOC flow rate centered near 30-35°N, and on sea surface temperature (SST) for the tropical Atlantic. The solar Arctic-mediated climate mechanism on multidecadal to centennial timescales presented here can be compared with and differentiated from both the related solar TSI and UV irradiance forcing on decadal timescales. The ultimate goal of this research is to gain sufficient mechanistic details so that the proposed solar-Arctic climate connection on multidecadal to centennial timescales can be confirmed or falsified. A further incentive is to expand this physical connection to longer, millennial-scale variability as motivated by the multiscale climate interactions shown by Braun et al. (2005), Weng (2005), and Dima and Lohmann (2009).  相似文献   

月球探测中月面热环境影响的研究现状   总被引：1，自引：0，他引：1  

于雯  李雄耀  王世杰 《地球科学进展》2012,27(12):1337-1343

在月球探测中,多光谱、热红外、被动微波辐射等探测技术被广泛应用于月表物质组分和物理特性的探测,也积累了大量探测数据。月球太阳辐照、月球表面温度、地球反照和内部热流等月面热环境的变化,改变了月表物质反射率、热发射率以及其他电磁学等基本性质,制约了探测数据的准确解译;同时,大幅度的太阳辐射强度和月面温度变化也直接威胁月面探测中巡视探测器和宇航员的安全。但是,目前月球表面热环境对探测活动的影响认识还比较欠缺,月面热环境的时空变化规律认识还不够充分,在实验研究不足的情况下对各种探测方式的影响缺乏系统的理解。结合月球探测的发展,进一步立足实验手段和探测结果,通过开展不同地形条件下月面太阳辐射和物理温度的时间变化和空间分布规律研究、探测数据与月面热环境参数时空匹配问题研究、建设具备类似物质组成和月面热环境特征的实验场地以及开展系统的热环境影响模拟实验研究,全面认识月面热环境参数的时空变化规律,探讨月面热环境对不同探测方式的影响将是月面热环境研究的重要内容。  相似文献   

The Solar Dynamo and Its Phase Transitions during the Last Millennium     

S. Duhau  C. de Jager 《Solar physics》2008,250(1):1-15

Variations in total solar irradiance (TSI) correlate well with changes in projected area of photospheric magnetic flux tubes associated with dark sunspots and bright faculae in active regions and network. This correlation does not, however, rule out possible TSI contributions from photospheric brightness inhomogeneities located outside flux tubes and spatially correlated with them. Previous reconstructions of TSI report agreement with radiometry that seems to rule out significant “extra-flux-tube” contributions. We show that these reconstructions are more sensitive to the facular contrasts used than has been generally recognized. Measurements with the Solar Bolometric Imager (SBI) provide the first reliable support for the relatively high, wide-band, disk-center contrasts required to produce 10% rms agreement. Longer term bolometric imaging will be required to determine whether the small but systematic TSI residuals we see here are caused by remaining errors in spot and facular areas and contrasts or by extra-flux-tube brightness structures such as bright rings around sunspots or “convective stirring” around active regions.  相似文献   

Cross-Calibration of TIMED SEE and SOHO EIT Irradiances     

R. A. Hock  F. G. Eparvier 《Solar physics》2008,250(1):207-219

Absolutely calibrated solar images are necessary for a variety of solar physics problems, such as the identification of solar variability sources and the derivation of differential emission measure (DEM) maps. SOHO EIT is absolutely calibrated by using TIMED SEE spectra to provide a method of determining physical values of irradiance for EIT images. EIT images from 1 April 2002 to 15 March 2005 in the 28.4- and 30.4-nm channels are compared to SEE daily spectra from the same time period. The resulting fitted EIT irradiances are well correlated to SEE irradiance measurements and are within the uncertainties of both instruments. The new cross-calibration results are compared to the currently used calibration based on the UARS SUSIM Mg ii index.  相似文献