磁赤道地区2007—2013年COSMIC掩星反演和国际参考电离层模型输出结果分析

An analysis of ionospheric characteristic parameters retrieved from COSMIC and IRI at Jicamarca during the period of 2007—2013

利用2007—2013年电离层测高仪位于磁赤道观测站Jicamarca(11.95°S,76.8°W,地磁纬度为1°N)的垂测数据和COSMIC掩星反演电离层资料,分析了不同太阳活动条件下两种探测技术获取电离层特征参数峰值密度N_mF_2和峰值高度H_mF_2的相关性,同时也探讨了国际参考电离层模型IRI输出参数与测高仪垂测数据的相关性.此外,进一步分析了COSMIC掩星和IRI模型在不同地方时高估或低估垂测参数的分布特征.结果表明:(1)由COSMIC掩星反演和IRI模型输出参数N_mF_2与测高仪垂测值N_mF_2得到的相关系数都在0.8以上.太阳活动低年COSMIC探测得到的N_mF_2相关性高于太阳活动高年得到的结果,但IRI模型在太阳高年得到的N_mF_2相关性好于太阳活动低年的计算结果.(2)由COSMIC掩星反演和IRI模型输出的H_mF_2与测高仪垂测值H_mF_2在春秋季得到的相关性较高,夏季的相关性最弱.由COSMIC掩星探测H_mF_2得到的季节和时间相关系数大都集中在0.8和0.6以上,但由IRI模型得到的H_mF_2相关性降低,特别是太阳活动低年的夏季和傍晚其相关系数低于0.3.(3)太阳低年COSMIC掩星和IRI模型白天时段大都高估、夜间至凌晨前后低估电离层参数N_mF_2和H_mF_2;但太阳活动高年N_mF_2在地方时午夜后则呈现高估的特点.相关结果为未来IRI模型的进一步完善以及低纬地区电离层同化模式研究提供参考.

To evaluate comprehensively the performance of the Constellation Observing System for Meteorology, Ionosphere and Climate （COSMIC） and the International Reference Ionosphere （IRI）, ionospheric characteristic parameters, the F2-peak density NmF2 and the F2-peak height HmF2 from Digisonde over Jicamarca （11.95°S, 76.8°W, I°N geomagnetic） are compared with data from the COSMIC radio occultation and IRI model during the different solar activity period of 2007-- 2013 in this study. The correlation of the digisonde observations and COSMIC/IRI measurements is analyzed emphatically, and then ionospheric parameters at Jicamarca being overestimated/underestimated by COSMIC and IRI are further discussed. The results are shown as follows： （1） Both the COSMIC-derived NmF2 and the IRI-derived NmF2 are in good agreement with the digisonde-derived measurements, and the correlation coefficients are more than 0.8. The correlation of the COSMIC-derived NmF2 in the solar minimum is greater than that in the solar maximum, and while the correlation of the IRI-derived NmF2 in the solar minimum is smaller than that in the solar maximum; （2） The HmF2 correlation between COSMIC/IRI and digisonde in spring and autumn is greater than that in summer and winter. Most seasonal and temporal correlation coefficients of COSMIC-derived HmF2 are more than 0.8 and 0.6, respectively. However, the correlation of the IRI-derived HmF2 decreased significantly, especially for the summer season in the solar minimum and dusk segment with a value of less than 0.3; （3） The ionospheric parameters are generally overestimated by COSMIC and IRI in the daytime and while they are underestimated from night to dawn in the solar minimum. Distinct from that in the solar minimum, the NmF2 are overestimated during the post-night （0000 LT-0500 LT） in the solar maximum. The current research could be useful for the ionospheric model improvement as well as data assimilation work based on the IRI model and COSMIC radio occultation data.