Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations
Unexpected observations of strong radiowave scatter at a ~85–90 km altitude with very high frequency radars were explained in the early 1990s, when it was demonstrated that these were due to special turbulent and small-scale scatterers with high Schmidt number. Studies of these phenomena have primar...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-02-01
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| Series: | Atmosphere |
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| Online Access: | https://www.mdpi.com/2073-4433/13/3/396 |
| _version_ | 1797472916927938560 |
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| author | Wayne K. Hocking Victoria L. Pinnegar |
| author_facet | Wayne K. Hocking Victoria L. Pinnegar |
| author_sort | Wayne K. Hocking |
| collection | DOAJ |
| description | Unexpected observations of strong radiowave scatter at a ~85–90 km altitude with very high frequency radars were explained in the early 1990s, when it was demonstrated that these were due to special turbulent and small-scale scatterers with high Schmidt number. Studies of these phenomena have primarily been concentrated in polar regions, and the events seem most prominent in regions of very cold air (below 140 K). Such radar echoes are referred to as polar mesosphere summer echoes (PMSE), and are rare at lower latitudes. In this paper we report observations of similar scatterers at sites below 50° latitude. The nature of these scatterers is discussed and results are compared to observations at the polar site of Eureka, Canada. Mid-latitude observations at frequencies of 48.92 and 45.47 MHz were made, respectively, at Abitibi Canyon (49.9° N latitude) and Markstay (46.5° N latitude) in Ontario, Canada. In particular, we look at the relationship of these scatterers to geophysical parameters, especially the <i>A<sub>p</sub></i> index. Our results suggest that mesospheric air with temperatures less than 140 K now exists below 50° latitude. This may be an indication of an equator-ward creep of global mesospheric cooling (which is associated with the well-known tropospheric global warming), but the scatterers at lower latitudes also demonstrate correlation with the <i>A<sub>p</sub></i> index. On the other hand, the polar scatterers at Eureka demonstrated no correlation of any significance with <i>A<sub>p</sub></i>. The importance of these results in regard to the global distribution of mesospheric temperatures is discussed, and comparisons to other measurements are made. |
| first_indexed | 2024-03-09T20:07:56Z |
| format | Article |
| id | doaj.art-8ec754687ed04ce8bb08998c7382a51b |
| institution | Directory Open Access Journal |
| issn | 2073-4433 |
| language | English |
| last_indexed | 2024-03-09T20:07:56Z |
| publishDate | 2022-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Atmosphere |
| spelling | doaj.art-8ec754687ed04ce8bb08998c7382a51b2023-11-24T00:26:11ZengMDPI AGAtmosphere2073-44332022-02-0113339610.3390/atmos13030396Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic VariationsWayne K. Hocking0Victoria L. Pinnegar1Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7, CanadaDepartment of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7, CanadaUnexpected observations of strong radiowave scatter at a ~85–90 km altitude with very high frequency radars were explained in the early 1990s, when it was demonstrated that these were due to special turbulent and small-scale scatterers with high Schmidt number. Studies of these phenomena have primarily been concentrated in polar regions, and the events seem most prominent in regions of very cold air (below 140 K). Such radar echoes are referred to as polar mesosphere summer echoes (PMSE), and are rare at lower latitudes. In this paper we report observations of similar scatterers at sites below 50° latitude. The nature of these scatterers is discussed and results are compared to observations at the polar site of Eureka, Canada. Mid-latitude observations at frequencies of 48.92 and 45.47 MHz were made, respectively, at Abitibi Canyon (49.9° N latitude) and Markstay (46.5° N latitude) in Ontario, Canada. In particular, we look at the relationship of these scatterers to geophysical parameters, especially the <i>A<sub>p</sub></i> index. Our results suggest that mesospheric air with temperatures less than 140 K now exists below 50° latitude. This may be an indication of an equator-ward creep of global mesospheric cooling (which is associated with the well-known tropospheric global warming), but the scatterers at lower latitudes also demonstrate correlation with the <i>A<sub>p</sub></i> index. On the other hand, the polar scatterers at Eureka demonstrated no correlation of any significance with <i>A<sub>p</sub></i>. The importance of these results in regard to the global distribution of mesospheric temperatures is discussed, and comparisons to other measurements are made.https://www.mdpi.com/2073-4433/13/3/396turbulencemesospheremesopauseradar echoesice crystalsnoctilucent clouds |
| spellingShingle | Wayne K. Hocking Victoria L. Pinnegar Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations Atmosphere turbulence mesosphere mesopause radar echoes ice crystals noctilucent clouds |
| title | Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations |
| title_full | Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations |
| title_fullStr | Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations |
| title_full_unstemmed | Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations |
| title_short | Mid-Latitude Detection of High Schmidt-Number Turbulent Echoes, and Comparison to PMSE and Geomagnetic Variations |
| title_sort | mid latitude detection of high schmidt number turbulent echoes and comparison to pmse and geomagnetic variations |
| topic | turbulence mesosphere mesopause radar echoes ice crystals noctilucent clouds |
| url | https://www.mdpi.com/2073-4433/13/3/396 |
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