Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique
<p>The RadAlp experiment aims at improving quantitative precipitation estimation (QPE) in the Alps thanks to X-band polarimetric radars and in situ measurements deployed in the region of Grenoble, France. In this article, we revisit the physics of propagation and attenuation of microwaves in...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-06-01
|
| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/15/3297/2022/amt-15-3297-2022.pdf |
| _version_ | 1818263487511527424 |
|---|---|
| author | G. Delrieu A. K. Khanal F. Cazenave B. Boudevillain |
| author_facet | G. Delrieu A. K. Khanal F. Cazenave B. Boudevillain |
| author_sort | G. Delrieu |
| collection | DOAJ |
| description | <p>The RadAlp experiment aims at improving quantitative precipitation estimation (QPE) in the Alps thanks to X-band polarimetric radars and in situ measurements deployed in the region of Grenoble, France. In this article, we revisit the physics of propagation and attenuation of microwaves in rain. We first derive four attenuation–reflectivity (<span class="inline-formula"><i>A</i><i>Z</i></span>) algorithms constrained, or not, by path-integrated attenuations (PIAs) estimated from the decrease in the return of selected mountain targets when it rains compared to their dry weather levels (the so-called mountain reference technique – MRT).
We also consider one simple polarimetric algorithm based on the profile of the total differential phase shift between the radar and the mountain targets. The central idea of the work is to implement these five algorithms all together in the framework of a generalized sensitivity analysis in order to establish useful parameterizations for attenuation correction. The parameter structure and the inherent mathematical ambiguity of the system of equations makes it necessary to organize the optimization procedure in a nested way. The core of the procedure consists of (i) exploring with classical sampling techniques the space of the parameters allowed to be variable from one target to the other and from one time step to the next, (ii) computing a cost function (CF) quantifying the proximity of the simulated profiles and (iii) selecting parameters sets for which a given CF threshold is exceeded. This core is activated for a series of values of parameters supposed to be fixed, e.g., the radar calibration error for a
given event. The sensitivity analysis is performed for a set of three convective events using the 0<span class="inline-formula"><sup>∘</sup></span> elevation plan position indicator (PPI) measurements of the
Météo-France weather radar located on top of the Moucherotte mountain (altitude of 1901 m a.s.l. – above sea level). It allows the estimation of critical parameters
for radar QPE using radar data alone. In addition to the radar calibration error, this includes the time series of radome attenuation and estimations of the coefficients of the power law models relating the specific attenuation and the reflectivity (<span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>Z</i></span> relationship) on the one hand and the specific attenuation and the specific differential phase shift (<span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>K</i><sub>dp</sub></span> relationship) on the other hand. It is noteworthy that the <span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>Z</i></span> and <span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>K</i><sub>dp</sub></span> relationships obtained are consistent with those derived from
concomitant drop size distribution measurements at ground level, in particular with a slightly non-linear <span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>K</i><sub>dp</sub></span> relationship (<span class="inline-formula"><i>A</i>=0.28</span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>K</mi><mi mathvariant="normal">dp</mi><mn mathvariant="normal">1.1</mn></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="26pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="0b5e5412ca6f28e886322ad7deed131c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-3297-2022-ie00001.svg" width="26pt" height="18pt" src="amt-15-3297-2022-ie00001.png"/></svg:svg></span></span>. X-Band radome attenuations as high as 15 dB were estimated, leading to the recommendation of avoiding the use of radomes for remote sensing of precipitation at such a frequency.</p> |
| first_indexed | 2024-12-12T19:19:48Z |
| format | Article |
| id | doaj.art-dab196cc233345f096ee204368fb3335 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-12T19:19:48Z |
| publishDate | 2022-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-dab196cc233345f096ee204368fb33352022-12-22T00:14:39ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482022-06-01153297331410.5194/amt-15-3297-2022Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference techniqueG. DelrieuA. K. KhanalF. CazenaveB. Boudevillain<p>The RadAlp experiment aims at improving quantitative precipitation estimation (QPE) in the Alps thanks to X-band polarimetric radars and in situ measurements deployed in the region of Grenoble, France. In this article, we revisit the physics of propagation and attenuation of microwaves in rain. We first derive four attenuation–reflectivity (<span class="inline-formula"><i>A</i><i>Z</i></span>) algorithms constrained, or not, by path-integrated attenuations (PIAs) estimated from the decrease in the return of selected mountain targets when it rains compared to their dry weather levels (the so-called mountain reference technique – MRT). We also consider one simple polarimetric algorithm based on the profile of the total differential phase shift between the radar and the mountain targets. The central idea of the work is to implement these five algorithms all together in the framework of a generalized sensitivity analysis in order to establish useful parameterizations for attenuation correction. The parameter structure and the inherent mathematical ambiguity of the system of equations makes it necessary to organize the optimization procedure in a nested way. The core of the procedure consists of (i) exploring with classical sampling techniques the space of the parameters allowed to be variable from one target to the other and from one time step to the next, (ii) computing a cost function (CF) quantifying the proximity of the simulated profiles and (iii) selecting parameters sets for which a given CF threshold is exceeded. This core is activated for a series of values of parameters supposed to be fixed, e.g., the radar calibration error for a given event. The sensitivity analysis is performed for a set of three convective events using the 0<span class="inline-formula"><sup>∘</sup></span> elevation plan position indicator (PPI) measurements of the Météo-France weather radar located on top of the Moucherotte mountain (altitude of 1901 m a.s.l. – above sea level). It allows the estimation of critical parameters for radar QPE using radar data alone. In addition to the radar calibration error, this includes the time series of radome attenuation and estimations of the coefficients of the power law models relating the specific attenuation and the reflectivity (<span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>Z</i></span> relationship) on the one hand and the specific attenuation and the specific differential phase shift (<span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>K</i><sub>dp</sub></span> relationship) on the other hand. It is noteworthy that the <span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>Z</i></span> and <span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>K</i><sub>dp</sub></span> relationships obtained are consistent with those derived from concomitant drop size distribution measurements at ground level, in particular with a slightly non-linear <span class="inline-formula"><i>A</i></span>–<span class="inline-formula"><i>K</i><sub>dp</sub></span> relationship (<span class="inline-formula"><i>A</i>=0.28</span> <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>K</mi><mi mathvariant="normal">dp</mi><mn mathvariant="normal">1.1</mn></msubsup><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="26pt" height="18pt" class="svg-formula" dspmath="mathimg" md5hash="0b5e5412ca6f28e886322ad7deed131c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-15-3297-2022-ie00001.svg" width="26pt" height="18pt" src="amt-15-3297-2022-ie00001.png"/></svg:svg></span></span>. X-Band radome attenuations as high as 15 dB were estimated, leading to the recommendation of avoiding the use of radomes for remote sensing of precipitation at such a frequency.</p>https://amt.copernicus.org/articles/15/3297/2022/amt-15-3297-2022.pdf |
| spellingShingle | G. Delrieu A. K. Khanal F. Cazenave B. Boudevillain Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique Atmospheric Measurement Techniques |
| title | Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique |
| title_full | Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique |
| title_fullStr | Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique |
| title_full_unstemmed | Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique |
| title_short | Sensitivity analysis of attenuation in convective rainfall at X-band frequency using the mountain reference technique |
| title_sort | sensitivity analysis of attenuation in convective rainfall at x band frequency using the mountain reference technique |
| url | https://amt.copernicus.org/articles/15/3297/2022/amt-15-3297-2022.pdf |
| work_keys_str_mv | AT gdelrieu sensitivityanalysisofattenuationinconvectiverainfallatxbandfrequencyusingthemountainreferencetechnique AT akkhanal sensitivityanalysisofattenuationinconvectiverainfallatxbandfrequencyusingthemountainreferencetechnique AT fcazenave sensitivityanalysisofattenuationinconvectiverainfallatxbandfrequencyusingthemountainreferencetechnique AT bboudevillain sensitivityanalysisofattenuationinconvectiverainfallatxbandfrequencyusingthemountainreferencetechnique |