基于ECMWF再分析数据的大气波导分布规律研究

The analysis on distribution characteristics of atmospheric ducts based on ECMWF reanalysis data

中文关键词:  大气波导  ERA-Interim  波导概率  波导强度  波导高度

英文关键词:Atmospheric ducts  ERA-Interim  Ducts probability  Magnitude of ducts  Altitude of ducts

中文摘要:

      大气波导对电磁波传播有显著的影响，大气波导特征参量分布研究对于分析电磁波传播乃至雷达、通信等电子设备效能具有重要意义，利用ERA-Interim数据计算大气波导特征参量，并用海洋调查期间的低空探空火箭数据计算的大气波导进行了验证，在此基础上用2011—2016年ERA-Interim温度、湿度分层数据统计分析了全球大气波导的发生概率、强度、高度，得出的结论是：大洋东部、大陆西部的信风带是大气波导的高发区，大洋上大气波导的高发区（发生概率＞50%）主要有6个，分别是北太平洋海区、南太平洋海区、北大西洋海区、南大西洋海区、北印度洋海区、南印度洋澳大利亚西部海区；同时，存在3个大气波导低发区或无大气波导区（热带辐合带区、北半球中高纬度区、南半球中高纬度区）。这些大气波导高发和低发区的位置、范围、发生概率具有季节变化，北半球MAM季（3—5月）发生概率最高，出现的范围最大，SON季（9—11月）概率最低，出现的范围最小，DJF（12、1、2月）、JJA（6—8月）季节介于两者之间；南半球SON季发生概率最高，出现的范围最大，MAM季概率最低，出现的范围最小。北半球大气波导强度总体上强于南半球大气波导强度，北半球MAM季大气波导较强海域范围最大，强度最强，其次为JJA季，SON季大气波导较强海域范围最小，强度最弱；南太平洋大气波导强度季节变化不明显，强度与北太平洋比均较弱，南大西洋SON季大气波导较强海域范围最大，强度最强，DJF季大气波导较强海域范围最小，强度最弱；北印度洋MAM季大气波导强度强，是大洋上波导最强的海域，大气波导较强海域范围大，JJA季基本没有大气波导。大气波导高度在信风带靠近大陆西岸海域高度较低，随着向西离岸距离增大高度升高，大气波导高发区的波导高度季节变化特征是：北半球在SON、DJF季高度高，波导高度高的区域面积大，MAM、JJA季高度低，波导高度高的区域面积小；南半球在MAM、JJA季高度高，波导高度高的区域面积大，SON、DJF季高度低，波导高度高的区域面积小；其他中低纬度近岸海域大气波导高度较低，大陆包围的内海大气波导高度最低。

英文摘要:

      Atmospheric ducts have significant impacts on electromagnetic wave propagation. Studying the distribution feature of atmospheric ducts is of great significance for analyzing electromagnetic wave propagation and effectiveness of radar and communication equipment. The feature values of atmospheric ducts are calculated based on the ERA-Interim reanalysis data, and these values are verified by rocketsonde data. On this basis, the feature values of global ducts are analyzed using the ERA-Interim data for the period of 2011—2016. The conclusions are as follows. The eastern part of the ocean and the western part of the continent in the trade wind belt are the high probability zone of the atmospheric ducts. There are six high probability zones and three little or no duct zones. The position, range, and probability of occurrence of these zones have seasonal variations. Season MAM (Mar—May) has the highest probability and the largest occurrence zone in the northern hemisphere, while Season SON (Sep—Nov) has the lowest probability and the smallest occurrence zone. Seasons DJF (Dec, Jan, Feb) and JJA (Jun—Aug) are between the two seasons. Season SON has the highest probability and the largest occurrence zone in the southern hemisphere, while Season MAM has the lowest probability and the smallest occurrence zone. The magnitude of atmospheric duct in the northern hemisphere is generally stronger than that in the southern hemisphere. Season MAM has the strongest magnitude of atmospheric duct in the northern hemisphere, followed by Season JJA. For Season SON, the sea areas with strong magnitude are the smallest, and the magnitude is the weakest. The magnitude of atmospheric duct in the South Pacific has no obvious seasonal variation, and its strength is weaker than that in the North Pacific. The strong magnitude zone of duct in the South Atlantic has the largest sea area and strongest in Season SON, and it has the smallest sea area and the weakest in Season DJF. The northern Indian Ocean has the strongest magnitude in Season MAM, which is the strongest zone in world ocean, and there is no atmospheric duct in Season JJA. The altitude of the atmospheric duct is low near the west coast of continent in the trade wind belt. As the distance from coast to the west increases, the altitude gradually increases. The high probability zone of the atmospheric duct is high altitude in Season SON and DJF in the northern hemisphere, the zone of high altitude is large, the low altitude in Season MAM and JJA, and the zone of high altitude is small. The high probability zone of the atmospheric duct is the high altitude in Season MAM and JJA in the southern hemisphere, and the zone of high altitude is large; the high probability zone of the atmospheric duct is the low altitude in Season SON and DJF, and the zone of high altitude is small. The altitude of atmospheric ducts in other low and middle latitudes offshore water is relatively low. In the inland sea areas surrounded by mainlands, the altitude of atmospheric ducts is the lowest.