The cloud type product 2B-CLDCLASS-LIDAR based on CloudSat and CALIPSO from June 2006 to May 2017 is used to examine the temporal and spatial distribution characteristics and interannual variability of eight cloud typ...The cloud type product 2B-CLDCLASS-LIDAR based on CloudSat and CALIPSO from June 2006 to May 2017 is used to examine the temporal and spatial distribution characteristics and interannual variability of eight cloud types(high cloud, altostratus, altocumulus, stratus, stratocumulus, cumulus, nimbostratus, and deep convection) and three phases(ice,mixed, and water) in the Arctic. Possible reasons for the observed interannual variability are also discussed. The main conclusions are as follows:(1) More water clouds occur on the Atlantic side, and more ice clouds occur over continents.(2)The average spatial and seasonal distributions of cloud types show three patterns: high clouds and most cumuliform clouds are concentrated in low-latitude locations and peak in summer;altostratus and nimbostratus are concentrated over and around continents and are less abundant in summer;stratocumulus and stratus are concentrated near the inner Arctic and peak during spring and autumn.(3) Regional averaged interannual frequencies of ice clouds and altostratus clouds significantly decrease, while those of water clouds, altocumulus, and cumulus clouds increase significantly.(4) Significant features of the linear trends of cloud frequencies are mainly located over ocean areas.(5) The monthly water cloud frequency anomalies are positively correlated with air temperature in most of the troposphere, while those for ice clouds are negatively correlated.(6) The decrease in altostratus clouds is associated with the weakening of the Arctic front due to Arctic warming, while increased water vapor transport into the Arctic and higher atmospheric instability lead to more cumulus and altocumulus clouds.展开更多
基于重构的修正过程(correction procedure via reconstruction,CPR)方法是一种适用于非结构网格、紧致高效的高阶方法,但在离散非线性对流项时容易因为混淆误差的累积而出现数值不稳定。本文研究了基于LG(Legendre-Gauss)点分裂形式的...基于重构的修正过程(correction procedure via reconstruction,CPR)方法是一种适用于非结构网格、紧致高效的高阶方法,但在离散非线性对流项时容易因为混淆误差的累积而出现数值不稳定。本文研究了基于LG(Legendre-Gauss)点分裂形式的CPR方法在欠解析流动中的稳定性,并将其与子单元限制技术结合,求解含激波的欠解析流动问题。结果表明:经过边界通量修正的LG点分裂形式CPR格式能够满足离散守恒律,且与子单元限制相结合后守恒律依然成立;在无激波的欠解析流动问题中,相比于散度形式CPR格式,分裂形式明显提高了计算的稳定性,而且比使用LGL(Legendre-Gauss-Lobatto)点的分裂形式CPR格式具有更小的数值误差;在含激波的欠解析流动求解中,相比基于LGL点的间断伽辽金谱元法子单元限制策略,基于LG点的分裂形式CPR格式子单元限制策略具有更高的分辨率和更小的振荡。展开更多
重构修正(correction procedure via reconstruction, CPR)是一种计算高效、模板紧致、适用于非结构网格的高阶方法,但是无法处理流场含有较强间断的问题。针对这个问题,前期基于二阶非等距非线性加权插值的激波捕捉格式以及非结构四边...重构修正(correction procedure via reconstruction, CPR)是一种计算高效、模板紧致、适用于非结构网格的高阶方法,但是无法处理流场含有较强间断的问题。针对这个问题,前期基于二阶非等距非线性加权插值的激波捕捉格式以及非结构四边形网格,发展了高阶CPR方法的一种子单元限制技术。该技术首先通过侦测因子确定出问题单元,然后将问题单元基于CPR求解点划分成非等距子单元,并在子单元中采用二阶激波捕捉格式进行计算。这种子单元限制技术保证了主单元和子单元的求解点重合,可以十分方便地处理主单元和子单元之间的数据交换。问题单元的侦测是该子单元限制技术的关键步骤,侦测出的问题单元的数量以及分布情况都将会影响数值结果。基于此,本文同时考虑了单元侦测和分维侦测两种问题单元侦测方式。通过激波管问题、Shu-Osher问题、双马赫反射问题、激波-旋涡干扰等典型算例对比分析了TVB、MDHE和JST侦测因子对数值格式分辨率的影响。研究结果表明:分维侦测能够减少问题单元的区域,进而提高分辨率。展开更多
基金supported in part by the National Natural Science Foundation of China (Grant No. 42105127)the Special Research Assistant Project of the Chinese Academy of Sciencesthe National Key Research and Development Plans of China (Grant Nos. 2019YFC1510304 and 2016YFE0201900-02)。
文摘The cloud type product 2B-CLDCLASS-LIDAR based on CloudSat and CALIPSO from June 2006 to May 2017 is used to examine the temporal and spatial distribution characteristics and interannual variability of eight cloud types(high cloud, altostratus, altocumulus, stratus, stratocumulus, cumulus, nimbostratus, and deep convection) and three phases(ice,mixed, and water) in the Arctic. Possible reasons for the observed interannual variability are also discussed. The main conclusions are as follows:(1) More water clouds occur on the Atlantic side, and more ice clouds occur over continents.(2)The average spatial and seasonal distributions of cloud types show three patterns: high clouds and most cumuliform clouds are concentrated in low-latitude locations and peak in summer;altostratus and nimbostratus are concentrated over and around continents and are less abundant in summer;stratocumulus and stratus are concentrated near the inner Arctic and peak during spring and autumn.(3) Regional averaged interannual frequencies of ice clouds and altostratus clouds significantly decrease, while those of water clouds, altocumulus, and cumulus clouds increase significantly.(4) Significant features of the linear trends of cloud frequencies are mainly located over ocean areas.(5) The monthly water cloud frequency anomalies are positively correlated with air temperature in most of the troposphere, while those for ice clouds are negatively correlated.(6) The decrease in altostratus clouds is associated with the weakening of the Arctic front due to Arctic warming, while increased water vapor transport into the Arctic and higher atmospheric instability lead to more cumulus and altocumulus clouds.
文摘基于重构的修正过程(correction procedure via reconstruction,CPR)方法是一种适用于非结构网格、紧致高效的高阶方法,但在离散非线性对流项时容易因为混淆误差的累积而出现数值不稳定。本文研究了基于LG(Legendre-Gauss)点分裂形式的CPR方法在欠解析流动中的稳定性,并将其与子单元限制技术结合,求解含激波的欠解析流动问题。结果表明:经过边界通量修正的LG点分裂形式CPR格式能够满足离散守恒律,且与子单元限制相结合后守恒律依然成立;在无激波的欠解析流动问题中,相比于散度形式CPR格式,分裂形式明显提高了计算的稳定性,而且比使用LGL(Legendre-Gauss-Lobatto)点的分裂形式CPR格式具有更小的数值误差;在含激波的欠解析流动求解中,相比基于LGL点的间断伽辽金谱元法子单元限制策略,基于LG点的分裂形式CPR格式子单元限制策略具有更高的分辨率和更小的振荡。
文摘重构修正(correction procedure via reconstruction, CPR)是一种计算高效、模板紧致、适用于非结构网格的高阶方法,但是无法处理流场含有较强间断的问题。针对这个问题,前期基于二阶非等距非线性加权插值的激波捕捉格式以及非结构四边形网格,发展了高阶CPR方法的一种子单元限制技术。该技术首先通过侦测因子确定出问题单元,然后将问题单元基于CPR求解点划分成非等距子单元,并在子单元中采用二阶激波捕捉格式进行计算。这种子单元限制技术保证了主单元和子单元的求解点重合,可以十分方便地处理主单元和子单元之间的数据交换。问题单元的侦测是该子单元限制技术的关键步骤,侦测出的问题单元的数量以及分布情况都将会影响数值结果。基于此,本文同时考虑了单元侦测和分维侦测两种问题单元侦测方式。通过激波管问题、Shu-Osher问题、双马赫反射问题、激波-旋涡干扰等典型算例对比分析了TVB、MDHE和JST侦测因子对数值格式分辨率的影响。研究结果表明:分维侦测能够减少问题单元的区域,进而提高分辨率。
