台风期间厦门电离层变化的一次特例分析

文中利用中国气象局厦门电离层监测站的电离层频高图数据,研究了2007年登陆地点在厦门附近地区的3次台风登陆事件期间厦门电离层的变化,分析比较了台风登陆前后F2 层临界频率(foF2)的相对变化、电离层Es和扩展F出现率等,结果显示这3次台风登陆均导致电离层foF2扰动,偶发E层(Es)和扩展F的出现率在3次台风临近登陆和登陆后都有明显的增加.台风圣帕(Sepat)登陆前一天,电离层foF2出现了相对月中值达40%(约4 MHz)的增强,登陆后电离层foF2迅速降低到月中值水平;台风韦帕(Wipha)登陆后电离层foF2从登陆前的略高于月中值的水平迅速下降到月中值以下(降幅达30%)并持续4天.台风罗莎登陆前的2天内电离层foF2低于月中值,台风罗莎登陆当天电离层foF2恢复到月中值水平,随后foF2出现了1天的下降和连续3天的增强.初步分析认为由于台风登陆前后,强烈的海气、陆气相互作用可能影响到电离层高度,从而导致对电离层foF2、Es和扩展F等参量发生变化.利用Wang(2005)提出的CoP机制,可以较好地解释台风登陆导致foF2下降,但文中发现在台风临近登陆出现的foF2上升的现象,则需要进一步深入分析研究.

A case study of the variation of ionospheric parameter during typhoons at Xiamen.

The variation of the F2 layer critical frequency (foF2), the frequencies of occurences of the sporadic E layer(Es) and spread F during 3 typhoons in 2007 observed by Xiamen Ionosonde Station are investigated in this paper. The results indicate that the foF2 is disturbed, and the Es and spread F occurring rates increase distinctly during the three typhoons approaching the station. One day before Sepat landing, the foF2 enhancement reached 40% (4 MHz) comparing with the month median value, and the foF2 quickly fell to the month median value after Sepat landing; the foF2 was a little higher than the month median value before Wipha landing, and quickly dropped below the median value after it landing with the decreasing amplitude of about 30% and lasted 4 days. On the other hand, the foF2 was below the month median value 2 days before Krosa landing; the foF2 restored the month median value during its landing, and then foF2 decreased in the following 1 day and increased continuously in the successive 3 days. Based on the preliminary analyses we consider that the interaction between the atmosphere, ocean and land may influence the altitude of the ionosphere, and bring about the foF2, Es, and spread F variations. Although the foF2 decrease is able to be well explained by the mechanism proposed in Wang (2005), further investigation is necessary to interpret the foF2 increase when the typhoon landing as revealed.