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卷云在大气辐射中扮演着重要角色,对天气系统和气候变化产生重要影响。相比传统地基观测手段,卫星遥感更容易探测到高层卷云的信息,本文利用CALIOP主动遥感仪器可获取较为准确的薄卷云特性的特点,针对MODIS被动遥感探测器反演的薄卷云云顶高度的偏差开展订正研究。研究选取2013～2017年京津冀地区MODIS云产品,结合CALIPSO卫星的卷云云顶高度数据,基于交叉验证的方法得到线性拟合方案,对MODIS卷云云顶高度进行订正。订正后的MODIS与CALIPSO卷云云顶高度差值的分布区间由?3～2 km变为?2.0～2.5 km,峰值由?0.8 km左右变为0.2 km左右。订正效果随云顶高度和云光学厚度的不同有所变化,其中较低层卷云和光学薄卷云的订正效果更明显。 相似文献
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Analysis and mapping of geochemical anomalies using logratio-transformed stream sediment data with censored values 总被引：1，自引：0，他引：1
There is lack of research and documentation of actual (as opposed to theoretical) benefits (e.g., mineral deposit discovery) of developments in compositional data analysis and imputation of censored values to mineral exploration geochemistry. In the present study, analyses of logratio- and ln-transformed stream sediment geochemical data containing ca. 30% of samples with censored values of a pathfinder element for the mineral deposit-type of interest yielded the following findings. Exclusion of those samples supports interpretation of multi-element anomalies reflecting the presence of mineralization. However, the multi-element anomaly maps obtained by exclusion of those samples are barely better than the multi-element anomaly maps derived by inclusion of those samples after replacing the censored values with 1/2 of detection limit or with imputed values. Logratio (i.e., alr, clr, or ilr) transformation, compared to ln-transformation, of stream sediment geochemical data does not improve mapping of pathfinder element anomalies reflecting the presence of mineralization. However, stream sediment geochemical data, excluding or including censored values (replaced with 1/2 of detection limit or with imputed values), should be clr- or ilr-transformed to enhance recognition of anomalous multi-element associations reflecting the presence of mineralization. The anomaly maps of multi-element associations derived from ilr-transformed data are better, albeit slightly, than the anomaly maps of multi-element associations derived from clr-transformed data. In the present study, the main benefit of either clr- or ilr-transformation, compared to either ln- or alr-transformation, of stream sediment geochemical data is the enhancement of anomalous multi-element associations reflecting the presence of mineralization. This is an important benefit because variations in trace element concentrations in regional-scale stream sediment geochemical data are mostly due to lithology and other factors (or processes) unrelated to mineralization. Further investigations of various exploration geochemical data are needed to demonstrate and document the actual (as opposed to theoretical) benefits of developments in compositional data analysis and imputation of censored values to mineral exploration. 相似文献
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Measurements of martian atmospheric water vapor made throughout Ls = 18.0°-146.4° (October 3, 1996-July 12, 1997) show changes in Mars humidity on hourly, daily, and seasonal time scales. Because our observing program during the 1996-1997 Mars apparition did not include concomitant measurement of nearby CO2 bands, high northern latitude data were corrected for dust and aerosol extinction assuming an optical depth of 0.8, consistent with ground-based and HST imaging of northern dust storms. All other measurements with airmass greater than 3.5 were corrected using a total optical depth of 0.5. Three dominant results from this data set are as follows: (1) pre- and post-opposition measurements made with the slit crossing many hours of local time on Mars’ Earth-facing disk show a distinct diurnal pattern with highest abundances around and slightly after noon with low abundances in the late afternoon, (2) measurements of water vapor over the Mars Pathfinder landing site (Carl Sagan Memorial Station) on July 12, 1997, found 21 ppt μm in the spatial sector centered near 19° latitude, 36° longitude while abundances around the site varied from as low as 6 to as high as 28 ppt μm, and (3) water vapor abundance is patchy on hourly and daily time scales but follows the usual seasonal trends. 相似文献
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利用星载激光雷达资料研究东亚地区云垂直分布的统计特征 总被引：23，自引：6，他引：17
已有研究表明: 云的垂直结构(简称CVS)是一个在卫星资料反演和气候模式预测中很重要的云特征。本文通过利用美国2006年刚发射的卫星CALIPSO (Cloud－Aerosol Lidar and Infrared Pathfinder Satellite Observations) 所负载的激光雷达Level 2_05km的云数据, 研究了东亚地区(18°N～53°N, 74°E～144°E) 云的垂直分布特征。结果表明: 东亚地区多层云云量在夏季、秋季、冬季、春季分别为43.6%、29.6%、21.1%、33.3%, 而多层云分布中双层云比例最大。云顶和云底高度除了随季节变化显著外, 还有明显的区域特征。单层云、 双层云以及三层云的云顶和云底高度的数据显示, 三层云中最上层的云顶和云底最高, 并始终高于两层云中最上层云的云顶和云底高度。平均云层厚度季节变化不明显, 其值普遍在0.9～2 km范围之间。而云层间距同样没有明显的季节和区域变化, 其出现的概率随距离的增大而减小。其中, 间距在0.35 km的概率最大, 占到将近50%。而间距在1.45 km附近的概率大约为15%, 高一点的可达到20%。 相似文献
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S. E. Larsen H. E. Jørgensen L. Landberg J. E. Tillman 《Boundary-Layer Meteorology》2002,105(3):451-470
The structures of mean flow and turbulence in the atmospheric surface boundary layer have been extensively studied on Earth, and to a far less extent on Mars, where only the Viking missions and the Pathfinder mission have delivered in-situ data. Largely the behaviour of surface-layer turbulence and mean flow on Mars is found to obey the same scaling laws as on Earth. The largest micrometeorological differences between the two atmospheres are associated with the low air density of the Martian atmosphere. Together with the virtual absence of water vapour, it reduces the importance of the atmospheric heat flux in the surface energy budget. This increases the temperature variation of the surface forcing the near-surface temperature gradient and thereby the diabatic heat flux to higher values than are typical on the Earth, resulting in turn in a deeper daytime boundary layer. As wind speed is much like that of the Earth, this larger diabatic heat flux is carried mostly by larger maximal values of T*, the surface scale temperature. The higher kinematic viscosity yields a Kolmogorov scale of the order of ten times larger than on Earth, influencing the transition between rough and smooth flow for the same surface features.The scaling laws have been validated analysing the Martian surface-layer data for the relations between the power spectra of wind and temperature turbulence and the corresponding mean values of wind speed and temperature. Usual spectral formulations were used based on the scaling laws ruling the Earth atmospheric surface layer, whereby the Earth's atmosphere is used as a standard for the Martian atmosphere. 相似文献
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A high-resolution satellite-derived sea surface temperature climatology for the western North Atlantic Ocean 总被引：1，自引：0，他引：1
Long-term and high-resolution (∼1.2 km) satellite-derived sea surface temperature (SST) fields of a monthly mean time series for the 1985–1999 period, and a daily climatology have been calculated for the North West Atlantic Ocean. The SST fields extend from 78°W to 41°W in longitude, and 30°N to 56°N in latitude, encompassing the region off Cape Hatteras, North Carolina, to the southern Labrador Sea. The monthly mean time series, consists of 180 cloud-masked monthly mean SST fields, derived from a full-resolution NOAA/NASA Pathfinder SST data set for the 1985–1999 period. The satellite-derived monthly mean SST fields, as compared with in situ monthly mean near-surface ocean temperatures from buoys located in the western North Atlantic, yield an overall RMS difference of 1.15 °C. The daily climatology, which consists of 365 fields, was derived by applying a least-squares harmonic regression technique on the monthly mean SST time series for the full study period. The monthly mean and daily climatological SST fields will be useful for studying inter-annual variability related to climate variability of SST over the study domain. 相似文献
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