What is Moss?

TRACE observations of active regions show a peculiar extreme ultraviolet (EUV) emission over certain plage areas. Termed `moss' for its spongy, low-lying, appearance, observations and modeling imply that the phenomenon is caused by thermal conduction from 3–5 MKcoronal loops overlying the plage: moss is the upper transition region emission of hot coronal loops. The spongy appearance is due to the presence of chromospheric jets or `spicules' interspersed with the EUV emission elements. High cadence TRACE observations show that the moss EUV elements interact with the chromospheric jets on 10 s time scales. The location of EUV emission in the moss does not correlate well to the locations of underlying magnetic elements in the chromosphere and photosphere, implying a complex magnetic topology for coronal loop footpoint regions. We summarize here the key observations leading to these conclusions and discuss new implications for understanding the structuring of the outer solar atmosphere. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005286503963     

PHOENIX-2: A New Broadband Spectrometer for Deci- metric and Microwave Radio Bursts – First Results

A broadband radio spectrometer has been put into operation at Bleien, Switzerland, to register the flare emission of the full Sun. In the frequency range of operation, 0.1 to 4.0 GHz, both modes of circular polarization are recorded continuously. The new system, Phoenix-2, has been developed from the experience with the previous Phoenix spectrometer. Improved, computer-controlled focal hardware allows now a complete daily calibration, a more sophisticated calibration procedure, and monitoring of all essential instrumental and environmental parameters. Calibrated data are now usually available the day after observation and are accessible through the Internet. The scientific improvements include a larger frequency range of observation, a larger number of completely recorded events due to full-day registration, more accurate measurements, particularly in circular polarization, and more reliable operation. First observations are presented and quantitative results comparing the calibration with single frequency instruments are reported. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1005194314845     

M4–18: the planetary nebula and its WC10 central star

We present a detailed analysis of the planetary nebula M4–18 (G146.7+07.6) and its WC10-type Wolf–Rayet (WR) central star, based on high‐quality optical spectroscopy (WHT/UES, INT/IDS, WIYN/DensPak) and imaging ( HST /WFPC2). From a non-LTE model atmosphere analysis of the stellar spectrum, we derive T _eff=31 kK,     v _∞=160 km s⁻¹ and abundance number ratios of H/He<0.5, C/He=0.60 and O/He=0.10. These parameters are remarkably similar to those of He 2–113 ([WC10]). Assuming an identical stellar mass to that determined by De Marco et al. for He 2–113, we obtain a distance of 6.8 kpc to M4–18 [ E ( B−V )=0.55 mag from nebular and stellar techniques]. This implies that the planetary nebula of M4–18 has a dynamical age of ∼3100 yr, in contrast to ≥270 yr for He 2–113. This is supported by the much higher electron density of the latter. These observations may be reconciled with evolutionary predictions only if [WC]-type stars exhibit a range in stellar masses.
Photoionization modelling of M4–18 is carried out using our stellar WR flux distribution, together with blackbody and Kurucz energy distributions obtained from Zanstra analyses. We conclude that the ionizing energy distribution from the WR model provides the best consistency with the observed nebular properties, although discrepancies remain.     

Predicted present-day evolution patterns of ice thickness and bedrock elevation over Greenland and Antarctica

This paper discusses predicted evolution patterns of present-day changes of ice thickness, surface elevation, and bedrock elevation over the Greenland and Antarctic continents. These were obtained from calculations with dynamic 3-D ice sheet models which were coupled to a visco-elastic solid Earth model. The experiments were initialized over the last two glacial cycles and subsequently averaged over the last 200 years to obtain the current evolution. The calculations indicate that the Antarctic Ice Sheet is still adjusting to the last glacial-interglacial transition yielding a decreasing ice volume and a rising bedrock elevation of the order of several centimetres per year. The Greenland Ice Sheet was found to be close to a stationary state with a mean thickness change of only a few millimetres per year, but the calculations revealed large spatial differences. Predicted patterns over Greenland are characterized by a small thickening over the ice sheet interior and a general thinning of the ablation area. In Antarctica, almost all of the predicted changes are concentrated in the West Antarctic Ice Sheet, which is still retreating at both the Weddell and Ross Sea margins. Over most of both ice sheets, the model indicates that the surface elevation trend is dominated by ice thickness changes rather than by bedrock elevation changes.     

南极海冰面积变化特性及其与赤道太平洋海表面温度的联系

南极海冰面积变化特性及其与赤道太平洋海表面温度的联系陈锦年,乐肯堂,于康玲,张彦臣（中国科学院海洋研究所,青岛２６６０７１）（青岛海洋大学,青岛２６６００３）关键词南极海冰面积,赤道太平洋海表面温度,厄尔尼诺１引言８０年代以前,人们对南极实地考察、资...     

西南地区东部夏季旱涝转换期的确定及其特征分析

提出一种区域旱涝转换期定义方法,并对西南地区东部1961-1995年旱涝转换期进行了划定,结果表明:本文对西南地区东部旱涝转换期定义方法是可行的;在西南地区东部,转换日期最早出现于6月第6候,最晚出现于7月第6候,主要集中于6月第6候、7月第1、2、4候;旱涝转换具有东多西少、南早北迟的特点,部分年份各地旱涝转换日期并不一致.     

用定量遥感方法监测UNDP试区小流域水土流失研究

简要介绍了水土流失定量遥感方法的组成和基本原理,重点叙述了它在小流域治理试区的应用作业和应用结果,并讨论了它的适应性、准确性、实用性和应用前景等。该法的监测模型可与美国近年刊出的RUSLE相媲美,且其因子算式算法系由我国实测资料所建,故更适合我国水土流失实际的应用效果,尤其适用于遥感和GIS数据的微机处理。其应用结果,不仅有比常规调查法和定性遥感法更准确实用的流失总量、各级面积的统计数据和流失现状图,而且还有流失治理规划的防治强度预报图。在UNDP试区应用表明,该法所建立的系统,也可对小流域(大于7km2)每年实施监测,以获水土流失变化动态的准确信息。     

Relationships between lightning activity and various thundercloud parameters: satellite and modelling studies

The lightning frequency model developed by Baker et al. [Baker, M.B., Christian, H.J., Latham, J., 1995. A computational study of the relationships linking lightning frequency and other thundercloud parameters, Q. J. R. Meteorol. Soc., 121, 1525–1548] has been refined and extended, in an effort to provide a more realistic framework from which to examine computationally the relationships that might exist between lightning frequency f (which is now being routinely measured from a satellite, using the NASA/MSFC Optical Transient Detector (OTD)) and a variety of cloud physical parameters. Specifically, superior or more comprehensive representations were utilised of: (1) glaciation via the Hallett–Mossop (H–M) process; (2) the updraught structure of the model cloud; (3) the liquid-water-content structure of the model cloud; (4) the role of the reversal temperature T_rev in influencing lightning characteristics; (5) the critical breakdown field for lightning initiation; and (6) the electrical characteristics of the ice crystal anvil of the model cloud. Although our extended studies yielded some new insights into the problem, the basic pattern of relationships between f and the other parameters was very close to that reported by Baker et al. (1995). The more elaborate treatment of T_rev restricted somewhat the range of conditions under which reverse-polarity lightning could be produced if the cloud glaciated via H–M, but confirmed the earlier conclusion that such lightning would not occur if the glaciation was of the Fletcher type. The computations yielded preliminary support for the hypothesis that satellite measurements of f might be used to determine values of the ice-content of cumulonimbus anvils: a parameter of climatological importance. The successful launch and continuing satisfactory functioning of the OTD [Christian, H.J., Goodman, S., 1992. Global observations of lightning from space, Proc. 9th Int. Conf. on Atmospheric Electricity, St. Petersburg, pp. 316–321; Christian, H.J., Blakesee, R.J., Goodman, S.J., 1992. Lightning imaging sensor (LIS) for the earth observing system. NASA Tech. Memorandum, 4350] make it possible—with a high degree of precision—to measure lightning location, occurrence time and frequency f over extensive areas of the Earth's surface. Measured global distributions of lightning and associated lightning stroke radiance demonstrate that: lightning activity is particularly pronounced over the tropics, much greater over land than over the oceans, and exhibits great seasonal variability; lightning radiance tends to be greater over the oceans, less when lightning activity is high, and greater in the Northern Hemisphere winter than summer.     

农作物后向散射特性的测量

利用多波段极化散射计对中原地区常见的几种农作物（水稻、棉花、玉米、花生）的后向散射特性进行了测量,并从散射系数的测量结果得出了其在不同频率及不同地物参数下的散射特点