A simultaneous study of ionospheric parameters derived from FORMOSAT‐3/COSMIC, GRACE, and CHAMP missions over middle, low, and equatorial latitudes: Comparison with ionosonde data
A simultaneous study of ionospheric parameters derived from FORMOSAT‐3/COSMIC, GRACE, and CHAMP missions over middle, low, and equatorial latitudes: Comparison with ionosonde data
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DOI：
10.1002/2014ja020192
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发表时间：
2014-09
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影响因子：
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通讯作者：
J. Habarulema;Z. Katamzi;E. Yizengaw
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文献类型：
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作者：
J. Habarulema;Z. Katamzi;E. Yizengaw
准确的电离层建模工作在一定程度上受到缺乏足够可靠的地面数据和无法验证现有天基数据的限制。在这篇文章中，我们首次提出了利用GPS无线电掩星(RO)技术(来自三个不同的任务：FORMOSAT-3/COSMIC、GRACE和CHAMP)获得的电离层数据的全面可靠性和有效性检查，方法是同时将RO数据与低纬、赤道和中纬度站的电离层探空数据进行比较。这份文件讨论了两个主要目标：(A)确定用于有效的RO和电离层探空仪数据比较的适当空间分辨率；(B)估计从RO飞行任务得出的电离层参数相对于非洲部门内的电离层探空仪数据的准确性。首次将从RO数据反演的电离层参数与非洲地区的电离层探空数据进行了比较(详细)，特别是南非中纬度站Grahamstown，GR13L(33.3°S，26.5°E)和Madimbo，MU12K(22.4°S，30.9°E)。对于赤道和低纬地区，分析了福塔莱萨FZA0M(3.8°S，38°W)、巴西和阿森松岛AS00Q(7.9°S，14.4°W)的资料。建立了一种简单但重要的方法来确定与电离层探空仪数据相比较要使用的纬度和经度范围。统计分析表明，对于中纬、低纬和赤道地区的有效比较，4.5°×4.5°、3°×3°和4°×4°是电离层探空站上空纬度和经度空间的近似合适的空间分辨率。有效比较的适当空间复盖面因区域而异，因此不应在区域/全球基础上采用恒定的假设，特别是如果研究/调查或模拟从中纬度地区扩展到低/赤道纬度地区。对于三个纬度地区，COSMIC高估了F2层的最大高度(HmF2)，低估了最大电子密度。这些结果为将RO数据用于电离层建模(特别是给出平均条件的模型)和对没有足够地面仪器/数据的区域进行表征提供了逐步的基础和动机。
Accurate ionospheric modeling efforts are partly restricted by lack of enough reliable ground‐based data and the inability to validate the existing space‐based data. In this article, we present a first time comprehensive reliability and validation check of ionospheric data derived using the GPS Radio Occultation (RO) Technique (from three separate missions: FORMOSAT‐3/COSMIC, GRACE, and CHAMP) by comparing RO data with ionosonde data for low‐latitude, equatorial, and midlatitude stations, simultaneously. This paper discusses two main objectives: (a) Determination of the appropriate spatial resolutions for effective RO and ionosonde data comparisons and (b) Estimating the accuracy of the ionospheric parameters derived from RO missions with respect to ionosonde data within the African sector. For the first time, ionospheric parameters retrieved from RO data have been compared (in details) to ionosonde data over the African sector, specifically for the South African midlatitude stations Grahamstown, GR13L (33.3°S, 26.5°E), and Madimbo, MU12K (22.4°S, 30.9°E). For the equatorial and low‐latitude regions, data for Fortaleza FZA0M (3.8°S, 38°W), Brazil, and Ascension Islands AS00Q (7.9°S, 14.4°W) was analyzed. A simple but important method to determine the latitudinal and longitudinal range to be used in comparison with ionosonde data has been established. Based on statistical analysis, it is found that 4.5°×4.5°, 3°×3°, and 4°×4° are the approximate suitable spatial resolutions in both latitude and longitude spaces over an ionosonde station for effective comparisons for midlatitude, low‐latitude, and equatorial regions, respectively. Appropriate spatial coverage for effective comparisons vary with region and therefore a constant assumption should not be applied on regional/global basis especially if the studies/investigations or modeling extends from middle to low/equatorial latitude zones. For the three latitude regions, COSMIC overestimates the maximum height of the F2 layer (hmF2) and underestimates the maximum electron densities. These results provide a step‐by‐step basis and motivation for the usage of RO data in ionospheric modeling (especially for models which give average conditions) and characterisation over regions that do not have sufficient ground‐based instruments/data.