Climatic trends in E-region critical frequency and virtual height above Tromsø (70° N, 10° E)
International audience We have examined the long time series of observations of E-region virtual height (1948?2006) and critical frequency (1935-2006) hitherto made by the Tromsø ionosonde at 70° N, 19° E. Combining a simplistic trend analysis with a rigorous treatment of errors we identify a negati...
| Main Authors: | , , |
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| Other Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
HAL CCSD
2007
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| Subjects: | |
| Online Access: | https://hal.science/hal-00318408 https://hal.science/hal-00318408/document https://hal.science/hal-00318408/file/angeo-25-2351-2007.pdf |
| Summary: | International audience We have examined the long time series of observations of E-region virtual height (1948?2006) and critical frequency (1935-2006) hitherto made by the Tromsø ionosonde at 70° N, 19° E. Combining a simplistic trend analysis with a rigorous treatment of errors we identify a negative trend in critical frequency. While a similar analysis of the virtual height h'E also suggests a negative trend, a closer examination reveals a possible weak positive trend prior to ~1975 and a strong negative trend from ~1975 to present. These two metrics of essentially the same feature of the ionosphere do not exhibit the same signature since critical frequency is controlled by photochemistry within the E-layer while height is controlled by pressure level. We further find that the trend in critical frequency is a daylight/summer phenomenon, no significant trend being evident in the winter subset of the data. On the other hand, the trends in virtual height are independent of season/daylight. |
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