Simulation study for ground-based Ku-band microwave observations of ozone and hydroxyl in the polar middle atmosphere
<p>The Ku-band microwave frequencies (10.70–14.25 GHz) overlap emissions from ozone (<span class="inline-formula">O<sub>3</sub></span>) at 11.072 GHz and hydroxyl radical (OH) at 13.441 GHz. These important chemical species in...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-03-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/1375/2019/amt-12-1375-2019.pdf |
| Summary: | <p>The Ku-band microwave frequencies (10.70–14.25 GHz)
overlap emissions from ozone (<span class="inline-formula">O<sub>3</sub></span>) at 11.072 GHz and hydroxyl radical
(OH) at 13.441 GHz. These important chemical species in the polar middle
atmosphere respond strongly to high-latitude geomagnetic activity
associated with space weather. Atmospheric model calculations predict that
energetic electron precipitation (EEP) driven by magnetospheric
substorms produces large changes in polar mesospheric <span class="inline-formula">O<sub>3</sub></span> and OH.
The EEP typically peaks at geomagnetic latitudes of <span class="inline-formula">∼65</span><span class="inline-formula"><sup>∘</sup></span> and evolves rapidly with time longitudinally and over the
geomagnetic latitude range 60–80<span class="inline-formula"><sup>∘</sup></span>. Previous
atmospheric modelling studies have shown that during substorms OH
abundance can increase by more than an order of magnitude at 64–84 km and
mesospheric <span class="inline-formula">O<sub>3</sub></span> losses can exceed 50 %. In this work, an atmospheric
simulation and retrieval study has been performed to determine the
requirements for passive microwave radiometers capable of measuring diurnal
variations in <span class="inline-formula">O<sub>3</sub></span> and OH profiles from high-latitude Northern
Hemisphere and Antarctic locations to verify model predictions. We show
that, for a 11.072 GHz radiometer making 6 h spectral measurements with
10 kHz frequency resolution and root-mean-square baseline noise of
1 mK, <span class="inline-formula">O<sub>3</sub></span> could be profiled over <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">8</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="42pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="6795c8d189f4e715bc85b29c13e85307"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-12-1375-2019-ie00001.svg" width="42pt" height="14pt" src="amt-12-1375-2019-ie00001.png"/></svg:svg></span></span>–0.22 hPa
(<span class="inline-formula">∼98</span>–58 km) with 10–17 km height resolution and
<span class="inline-formula">∼1</span> ppmv uncertainty. For the equivalent 13.441 GHz
measurements with vertical sensor polarisation, OH could be profiled over
<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">3</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="42pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="b2936b2136c0b6ded9a213ef1277680c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-12-1375-2019-ie00002.svg" width="42pt" height="14pt" src="amt-12-1375-2019-ie00002.png"/></svg:svg></span></span>–0.29 hPa (<span class="inline-formula">∼90</span>–56 km) with 10–17 km
height resolution and <span class="inline-formula">∼3</span> ppbv uncertainty. The proposed
observations would be highly applicable to studies of EEP, atmospheric
dynamics, planetary-scale circulation, chemical transport, and the
representation of these processes in polar and global climate models. Such
observations would provide a relatively low-cost alternative to
increasingly sparse satellite measurements of the polar middle atmosphere,
extending long-term data records and also providing “ground truth”
calibration data.</p> |
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| ISSN: | 1867-1381 1867-8548 |