Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information?
<p>Far-infrared (FIR: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">100</m...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/7927/2019/acp-19-7927-2019.pdf |
| _version_ | 1828544782117371904 |
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| author | C. Bellisario H. E. Brindley S. F. B. Tett R. Rizzi G. Di Natale L. Palchetti G. Bianchini |
| author_facet | C. Bellisario H. E. Brindley S. F. B. Tett R. Rizzi G. Di Natale L. Palchetti G. Bianchini |
| author_sort | C. Bellisario |
| collection | DOAJ |
| description | <p>Far-infrared (FIR: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">100</mn><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><msup><mi mathvariant="normal">cm</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow><mo><</mo><mtext>wavenumber</mtext></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="121pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1368b7d9579ef3b9a97e6df034c9113a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-7927-2019-ie00001.svg" width="121pt" height="13pt" src="acp-19-7927-2019-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula"><i>ν</i><667</span> <span class="inline-formula">cm<sup>−1</sup></span>) radiation emitted by the Earth and its
atmosphere plays a key role in the Earth's energy budget. However, because of
a lack of spectrally resolved measurements, radiation schemes in climate
models suffer from a lack of constraint across this spectral range.
Exploiting a method developed to estimate upwelling far-infrared radiation
from mid-infrared (MIR: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">667</mn><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><msup><mi mathvariant="normal">cm</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow><mo><</mo><mi mathvariant="italic">ν</mi><mo><</mo><mn mathvariant="normal">1400</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="101pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="ffea5bebe86a56cd11629887c3b6bb87"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-7927-2019-ie00002.svg" width="101pt" height="13pt" src="acp-19-7927-2019-ie00002.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>−1</sup></span>) observations, we explore the possibility of
inferring zenith FIR downwelling radiances in zenith-looking observation
geometry, focusing on clear-sky conditions in Antarctica. The methodology
selects a MIR predictor wavenumber for each FIR wavenumber based on the
maximum correlation seen between the different spectral ranges. Observations
from the REFIR-PAD instrument (Radiation Explorer in the Far Infrared –
Prototype for Application and Development) and high-resolution radiance
simulations generated from co-located radio soundings are used to develop and
assess the method. We highlight the impact of noise on the correlation
between MIR and FIR radiances by comparing the observational and theoretical
cases. Using the observed values in isolation, between 150 and 360 <span class="inline-formula">cm<sup>−1</sup></span>, differences between the “true” and
“extended”
radiances are less than 5 %. However, in spectral bands of low signal,
between 360 and 667 <span class="inline-formula">cm<sup>−1</sup></span>, the impact of instrument
noise is strong and increases the differences seen. When the extension of the
observed spectra is performed using regression coefficients based on
noise-free radiative transfer simulations the results show strong biases,
exceeding 100 % where the signal is low. These biases are reduced to just a
few percent if the noise in the observations is accounted for in the
simulation procedure. Our results imply that while it is feasible to use this
type of approach to extend mid-infrared spectral measurements to the
far-infrared, the quality of the extension will be strongly dependent on the
noise characteristics of the observations. A good knowledge of the
atmospheric state associated with the measurements is also required in order
to build a representative regression model.</p> |
| first_indexed | 2024-12-12T02:36:34Z |
| format | Article |
| id | doaj.art-45db08f624484bb590da3e57d243d986 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T02:36:34Z |
| publishDate | 2019-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-45db08f624484bb590da3e57d243d9862022-12-22T00:41:16ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-06-01197927793710.5194/acp-19-7927-2019Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information?C. Bellisario0H. E. Brindley1S. F. B. Tett2R. Rizzi3G. Di Natale4L. Palchetti5G. Bianchini6School of Geosciences, University of Edinburgh, Crew Building, The King's Buildings, Edinburgh, EH9 3FF, UKSpace and Atmospheric Physics Group, National Centre for Earth Observation, Imperial College London, London, UKSchool of Geosciences, University of Edinburgh, Crew Building, The King's Buildings, Edinburgh, EH9 3FF, UKDepartment of Physics and Astronomy, University of Bologna, Bologna, ItalyIstituto Nazionale di Ottica – CNR, Sesto Fiorentino, ItalyIstituto Nazionale di Ottica – CNR, Sesto Fiorentino, ItalyIstituto Nazionale di Ottica – CNR, Sesto Fiorentino, Italy<p>Far-infrared (FIR: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">100</mn><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><msup><mi mathvariant="normal">cm</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow><mo><</mo><mtext>wavenumber</mtext></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="121pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1368b7d9579ef3b9a97e6df034c9113a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-7927-2019-ie00001.svg" width="121pt" height="13pt" src="acp-19-7927-2019-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula"><i>ν</i><667</span> <span class="inline-formula">cm<sup>−1</sup></span>) radiation emitted by the Earth and its atmosphere plays a key role in the Earth's energy budget. However, because of a lack of spectrally resolved measurements, radiation schemes in climate models suffer from a lack of constraint across this spectral range. Exploiting a method developed to estimate upwelling far-infrared radiation from mid-infrared (MIR: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">667</mn><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><msup><mi mathvariant="normal">cm</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup></mrow><mo><</mo><mi mathvariant="italic">ν</mi><mo><</mo><mn mathvariant="normal">1400</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="101pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="ffea5bebe86a56cd11629887c3b6bb87"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-7927-2019-ie00002.svg" width="101pt" height="13pt" src="acp-19-7927-2019-ie00002.png"/></svg:svg></span></span> <span class="inline-formula">cm<sup>−1</sup></span>) observations, we explore the possibility of inferring zenith FIR downwelling radiances in zenith-looking observation geometry, focusing on clear-sky conditions in Antarctica. The methodology selects a MIR predictor wavenumber for each FIR wavenumber based on the maximum correlation seen between the different spectral ranges. Observations from the REFIR-PAD instrument (Radiation Explorer in the Far Infrared – Prototype for Application and Development) and high-resolution radiance simulations generated from co-located radio soundings are used to develop and assess the method. We highlight the impact of noise on the correlation between MIR and FIR radiances by comparing the observational and theoretical cases. Using the observed values in isolation, between 150 and 360 <span class="inline-formula">cm<sup>−1</sup></span>, differences between the “true” and “extended” radiances are less than 5 %. However, in spectral bands of low signal, between 360 and 667 <span class="inline-formula">cm<sup>−1</sup></span>, the impact of instrument noise is strong and increases the differences seen. When the extension of the observed spectra is performed using regression coefficients based on noise-free radiative transfer simulations the results show strong biases, exceeding 100 % where the signal is low. These biases are reduced to just a few percent if the noise in the observations is accounted for in the simulation procedure. Our results imply that while it is feasible to use this type of approach to extend mid-infrared spectral measurements to the far-infrared, the quality of the extension will be strongly dependent on the noise characteristics of the observations. A good knowledge of the atmospheric state associated with the measurements is also required in order to build a representative regression model.</p>https://www.atmos-chem-phys.net/19/7927/2019/acp-19-7927-2019.pdf |
| spellingShingle | C. Bellisario H. E. Brindley S. F. B. Tett R. Rizzi G. Di Natale L. Palchetti G. Bianchini Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information? Atmospheric Chemistry and Physics |
| title | Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information? |
| title_full | Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information? |
| title_fullStr | Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information? |
| title_full_unstemmed | Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information? |
| title_short | Can downwelling far-infrared radiances over Antarctica be estimated from mid-infrared information? |
| title_sort | can downwelling far infrared radiances over antarctica be estimated from mid infrared information |
| url | https://www.atmos-chem-phys.net/19/7927/2019/acp-19-7927-2019.pdf |
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