Atmospheric thermal structure and cloud features in the southern hemisphere of Venus as retrieved from VIRTIS/VEX radiation measurements
Atmospheric thermal structure and cloud features in the southern hemisphere of Venus as retrieved from VIRTIS/VEX radiation measurements
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DOI：
10.1016/j.icarus.2014.01.020
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发表时间：
2014-04-01
期刊：
影响因子：
3.2
通讯作者：
Arnold, G.
中科院分区：
文献类型：
--
作者：
Haus, R.;Kappel, D.;Arnold, G.
利用欧空局金星快车使命上的可见光和红外热成像光谱仪（VIRTIS）在中等分辨率红外测绘通道（M-IR，1-5 μ m）中记录的光谱测量数据，研究了金星大气层的热结构和云特征。北方半球的新方法和检索结果最近已由豪斯等人描述（豪斯，R.，卡佩尔，D.，Arnold，G. [2013年]。星球空间科学89，77-101. http://dx.doLorg/10.1016/j.pss.2013.09.020).现在，南半球的中间层温度和云参数场的地图，包括高度，纬度，当地时间和使命时间的变化。利用2006年4月至2008年10月金星8个太阳日的辐射光谱数据，反演了南北半球的温度-高度廓线，其纬向平均值非常相似，证明了全球大气温度结构的南北轴对称性。在75 ° S和63 km高度上，冷领和较暖的极涡区域表现出最强的温度变率，标准偏差可达8.5 K，而在75 km以上的低中纬度地区，标准偏差约为1.0 K。中间层温度场强烈地依赖于当地时间。在75公里以上的高度，大气在后半夜比较温暖，而在较低高度的黎明侧通常比黄昏侧冷约8 K。当地最低温度为220 K，出现在当地时间03：00，距离65公里，南纬60度。极地纬度的温度标准差在午夜附近特别大。温度随太阳经度的变化是由太阳热潮汐与占主导地位的昼夜分量。观测到的云参数变化对反演的中层纬向平均温度结构的影响是中等的，在60和75公里之间的高度不超过2-3 K。2006 - 2008年朱利安日的中层热结构基本稳定，云结构也存在全球南北轴对称性。云顶高度在1 μ m处从赤道的71公里缓慢下降到45-50度处的70公里，并迅速向极地下降50度。它在两极达到61公里。垂直云柱中的平均粒子大小从中纬度向两极和向赤道增加，导致最小和最大纬向平均云不透明度约为32和42，1 μ m处的行星平均值为36.5。云特征的纬向平均值在不同的太阳日是相似的，但随当地时间的变化是非常复杂的，与云的超旋转密不可分。(C)2014 Elsevier Inc. All rights reserved.
Thermal structure and cloud features in the atmosphere of Venus are investigated using spectroscopic nightside measurements recorded by the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA's Venus Express mission in the moderate resolution infrared mapping channel (M-IR, 1-5 mu m). New methodical approaches and retrieval results for the northern hemisphere have been recently described by Haus et al. (Haus, R., Kappel, D., Arnold, G. [2013]. Planet. Space Sci. 89, 77-101. http://dx.doLorg/10.1016/j.pss.2013.09.020). Now, southern hemisphere maps of mesospheric temperature and cloud parameter fields are presented that cover variations with altitude, latitude, local time, and mission time. Measurements from the entire usable data archive are utilized comprising radiation spectra recorded during eight Venus solar days between April 2006 and October 2008.Zonal averages of retrieved temperature altitude profiles in both hemispheres are very similar and give evidence of global N-S axial symmetry of atmospheric temperature structure. Cold collar and warmer polar vortex regions exhibit the strongest temperature variability with standard deviations up to 8.5 K at 75 degrees S and 63 km altitude compared with about 1.0 K at low and mid latitudes above 75 km. The mesospheric temperature field strongly depends on local time. At altitudes above about 75 km, the atmosphere is warmer in the second half of night, while the dawn side at lower altitudes is usually colder than the dusk side by about 8 K. Local minimum temperature of 220 K occurs at 03:00 h local time at 65 km and 60 degrees S. Temperature standard deviation at polar latitudes is particularly large near midnight. Temperature variability with solar longitude is forced by solar thermal tides with a dominating diurnal component. The influence of observed cloud parameter changes on retrieved mesospheric zonal average temperature structure is moderate and does not exceed 2-3 K at altitudes between 60 and 75 km. The mesospheric thermal structure was essentially stable with Julian date between 2006 and 2008.Global N-S axial symmetry is also observed in cloud structures. Cloud top altitude at 1 mu m slowly decreases from 71 km at the equator to 70 km at 45-50 degrees and rapidly drops poleward of 50 degrees. It reaches 61 km over both poles. Average particle size in the vertical cloud column increases from mid latitudes toward the poles and also toward the equator resulting in minimum and maximum zonal average cloud opacities of about 32 and 42 and a planetary average of 36.5 at 1 mu m. Zonal averages of cloud features are similar at different solar days, but variations with local time are very complex and inseparably associated with the superrotation of the clouds. (C) 2014 Elsevier Inc. All rights reserved.