An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared
An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared
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DOI：
10.1029/2002je001921
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发表时间：
2002-09
影响因子：
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通讯作者：
Junjun Liu;M. Richardson;R. J. Wilson
中科院分区：
文献类型：
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作者：
Junjun Liu;M. Richardson;R. J. Wilson
[1]对Mariner 9号、Viking和火星全球测量者(MGS)收集的热红外数据进行了相互比较，特别关注了气温、尘埃不透明度和水冰不透明度。重点是创建一个统一的数据集，以最有效地减少仪器间的偏差和偏移量。年周期始终表现出强烈的春分不对称性，北方春季和夏季表现出相对较低的温度，很高的年际重复性，基本上没有短期(数十天)的变化。火星北部春季和夏季的全球平均夜间气温每年接近1开尔文。白天的温度表现出更大的变异性(3-6K)。白天和夜间温度重复性的差异还不清楚。北欧海盗和MGS的气温在这一时期基本上是无法区分的，这表明北欧海盗和MGS时代的气候状况基本上相同。南方夏季的特点是沙尘暴活动强烈，因此气温年际变化很大。沙尘不透明度在南部春季和夏季表现出显著的年际变化，与区域和环绕地球的沙尘暴的间歇性活动有关，但在北部春季和夏季表现出较高的年际重复性。具体地说，北方春末和夏初的沙尘不透明度似乎对前一年南半球春季或夏季主要沙尘暴的发生(或不发生)完全不敏感。我们发现，维京和MGS数据集都显示出显著的(和相似的)极冠边缘沙尘暴活动。各种主要沙尘暴的起源可以从Viking和MGS的热红外数据中确定，包括从北部秋季斜压带到南半球热带的尘埃输送，这也在可见光成像中得到了确认。我们还注意到，到目前为止，航天器观测到的每年都有与沙尘暴发展或衰变有关的非常高的尘埃不透明度，在LS=225°附近。首次从海盗号的红外数据中提取了水冰不透明度。结果表明，北半球春季和夏季热带云带的结构和演变在Viking和MGS观测的多年中的每一年都是基本相同的。相对微妙的空间特征年复一年地出现在云带中，这表明地表地形和热物理性质的影响以及水蒸气的合理持续供应。结果表明，热带云带在春季和夏季的季节演变过程中，唯一显著的年际偏差出现在LS=140°~160°之间，其中与小沙尘暴有关的第二个MGS年的不透明度下降。北欧海盗和MGS观测中观测到的极地引擎盖云具有相似的时间和范围。在1977a和2001年的沙尘暴期间，希腊盆地地区的尘埃和水冰之间的相互作用是突出的。观测结果表明，火星大气层的大气现象呈现出一种非常“可重复”的年度循环。然而，这一周期的一个主要部分是高度可变的和潜在的重大沙尘暴事件的发生。在这样的沙尘暴事件之后，大气迅速放松到稳定的、可重复的状态。
[1] Intercomparison of thermal infrared data collected by Mariner 9, Viking, and Mars Global Surveyor (MGS) is presented with a specific focus on air temperatures, dust opacities, and water ice opacities. Emphasis is placed on creating a uniform data set to most effectively reduce interinstrument biases and offsets. The annual cycle consistently shows a strong asymmetry about the equinoxes, with northern spring and summer exhibiting relatively low temperatures, very high year-to-year repeatability, and essentially no short-term (tens of days) variability. The globally averaged Martian nighttime air temperatures close annually to within a Kelvin during northern spring and summer. Daytime temperatures show more variability (3–6 K). The difference in repeatability of daytime versus nighttime temperatures is not understood. Viking and MGS air temperatures are essentially indistinguishable for this period, suggesting that the Viking and MGS eras are characterized by essentially the same climatic state. Southern summer is characterized by strong dust storm activity and hence strong year-to-year air temperature variability. Dust opacity shows a remarkable degree of interannual variability in southern spring and summer, associated with the intermittent activity of regional and planet-encircling dust storms, but exhibits high year-to-year repeatability in northern spring and summer. Specifically, late northern spring and early northern summer dust opacities appear to be completely insensitive to the occurrence (or not) of major dust storms in the previous southern spring or summer. We show that both Viking and MGS data sets exhibit significant (and similar) polar cap edge dust storm activity. The origins of the various major dust storms can be identified in the thermal infrared data from Viking and MGS, including the transport of dust from the northern autumn baroclinic zone into the southern hemisphere tropics, which has also been identified in visible imaging. We also note that the period around Ls = 225° is characterized by very high dust opacities associated with dust storm development or decay in every year thus far observed by spacecraft. Water ice opacities have been retrieved from Viking infrared data for the first time. We show that the northern spring and summer tropical cloud belt structure and evolution are essentially the same in each of the multiple years observed by Viking and MGS. Relatively subtle spatial features recur in the cloud belt from year to year, suggesting the influence of surface topography and thermophysical properties and a reasonably consistent supply of water vapor. The seasonal evolution of the tropical cloud belt through northern spring and summer is shown, with the only significant deviations between years occurring from Ls = 140° to 160°, where opacities fall in the second MGS year associated with a small dust storm. Polar hood clouds are observed in Viking and MGS observations with similar timing and extent. Interactions between dust and water ice were highlighted in the Hellas basin region during the southern spring 1977a and 2001 dust storms. The observations demonstrate that the Martian atmosphere executes a very “repeatable” annual cycle of atmospheric phenomena. However, a major part of this cycle is the occurrence of highly variable and potentially major dust storm events. After such dust storm events the atmosphere rapidly relaxes to its stable, repeatable state.