福衛三號電離層資料品質控管

The Quality Control of Formosat-3/COSMIC ionospheric data

柯孝聰(Hsiao-Tzung Ko)

指導教授 ： 朱延祥

國立中央大學/地球科學學院/太空科學研究所/碩士(2007年)

摘要

本文針對福衛三號2006.07~2007.02電離層電子濃度資料設計一套品質篩選( Quality Control )的流程：首先，利用電子濃度對高度的斜率正負變換，重新定義原始資料中的F2 層的峰值高度( Layer Peak-height )與最大電子密度( Peak-density )，另外，定義兩個參數，其一是420 km與490 km處的電子濃度對高度的斜率( Slope )，另一是140 km以上電子濃度的擾動量( Mean Deviation )，利用物理與統計特性替這兩項參數設定了門檻值：-9 < Slope < -0.02與M.D.< 3，在門檻值之內屬於品質較優的資料；經過F2 Layer Peak-height重新定義與Slope、M.D.的條件篩選後，將其資料與IRI 模式(Model)模擬值、電離層觀測儀( Ionosonde )觀測值作一比較，證實經篩選後的資料遠優於未經篩選的資料；再與IRI模擬值作一差異值的分布比較，差異值多發生在赤道正負20度的區域，且都是IRI模擬值偏高。分別再針對前述定義的Slope與M.D.做日變化與季節變化，可以觀察到Slope的變化情形與F2 Layer Peak-density呈負相關，而M.D.有顯著變化的區域則與電漿泡發生的分布情形類似。

關鍵字

中華衛星三號 ； 福爾摩沙三號 ； 福衛三號

並列摘要

We develop a Quality Control algorithm in this study to screen out bad FORMOSAT-3/COSMIC-retrieved electron density profile collected during the period from July 2006 to February 2007. First of all, we redefine the F2 Layer Peak-height and F2 Layer Peak-density of the raw data. Second, we define two new parameters for the use of the data quality control: one is Slope which is the vertical gradient of the electron density for the height range 420-490 km, the other one is Mean Deviation (M.D.) which is the summation of the relative deviation of the raw electron density from the background electron density profile that is obtained by doing 9-point running average on the original electron density profile above 140 km. According to the statistics analysis, we select thresholds for these two parameters: -9 < Slope < -0.02 and M.D. < 3, namely, the electron density profile with the slope and M.D. are, respectively, within their thresholds is accepted for further analysis. We compare the data between COSMIC measurement and IRI Model and find that the threshold that we define are pertinent and acceptable. With good quality data, we compare COSMIC-measured electron density with IRI model data. We find that the differences in the two are primarily distributed along the geomagnetic equator. We also compare the seasonal and diurnal variations of Slope and M.D.. The result shows that Slope is negatively correlated with F2 Layer Peak-density and the variation of M.D. is distributed in the region where the plasma bubbles are frequently occurred.

並列關鍵字

Formosat-3 ； COSMIC

參考文獻

立中央大學太空科學研究所, 2000

of Venus as studies with the Mariner V radio occultation experiment,

Astron. J., 76, 123-140, 1971.

measurements using the Global Position System, J. Geophys. Res.,

5. M. C. Kelley, The Earth’s ionosphere, Academic Press, p5, 1989.