Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems
This study presents the evaluation of a technique to estimate cloud condensed water content (CWC) in tropical convection from airborne cloud radar reflectivity factors at 94 GHz and in situ measurements of particle size distributions (PSDs) and aspect ratios of ice crystal populations. The appro...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/10/2239/2017/amt-10-2239-2017.pdf |
| _version_ | 1811213938261491712 |
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| author | E. Fontaine E. Fontaine D. Leroy A. Schwarzenboeck J. Delanoë A. Protat F. Dezitter A. Grandin J. W. Strapp L. E. Lilie |
| author_facet | E. Fontaine E. Fontaine D. Leroy A. Schwarzenboeck J. Delanoë A. Protat F. Dezitter A. Grandin J. W. Strapp L. E. Lilie |
| author_sort | E. Fontaine |
| collection | DOAJ |
| description | This study presents the evaluation of a technique to
estimate cloud condensed water content (CWC) in tropical convection from
airborne cloud radar reflectivity factors at 94 GHz and in situ measurements
of particle size distributions (PSDs) and aspect ratios of ice crystal
populations. The approach is to calculate from each 5 s mean PSD and
flight-level reflectivity the variability of all possible solutions of <i>m</i>(<i>D</i>)
relationships fulfilling the condition that the simulated radar reflectivity
factor (<b>T</b>-matrix method) matches the measured radar reflectivity factor. For
the reflectivity simulations, ice crystals were approximated as oblate
spheroids, without using a priori assumptions on the mass–size relationship
of ice crystals. The CWC calculations demonstrate that individual CWC values
are in the range ±32 % of the retrieved average <span style="text-decoration: overline;">CWC</span> value
over all CWC solutions for the chosen 5 s time intervals. In addition, during
the airborne field campaign performed out of Darwin in 2014, as part of the
international High Altitude Ice Crystals/High Ice Water Content
(HAIC/HIWC) projects, CWCs were measured independently with the new IKP-2
(isokinetic evaporator probe) instrument along with simultaneous particle
imagery and radar reflectivity. Retrieved <span style="text-decoration: overline;">CWC</span>s from the <b>T</b>-matrix
radar reflectivity simulations are on average 16 % higher than the direct
CWC<sub>IKP</sub> measurements. The differences between the CWC<sub>IKP</sub> and
averaged retrieved <span style="text-decoration: overline;">CWC</span>s are found to be primarily a function of the
total number concentration of ice crystals. Consequently, a correction term
is applied (as a function of total number concentration) that significantly
improves the retrieved CWC. After correction, the retrieved <span style="text-decoration: overline;">CWC</span>s
have a median relative error with respect to measured values of only −1 %.
Uncertainties in the measurements of total concentration of hydrometeors are
investigated in order to calculate their contribution to the relative error
of calculated <span style="text-decoration: overline;">CWC</span> with respect to measured CWC<sub>IKP</sub>. It is shown
that an overestimation of the concentration by about +50 % increases the
relative errors of retrieved <span style="text-decoration: overline;">CWC</span>s by only +29 %, while possible
shattering, which impacts only the concentration of small hydrometeors,
increases the relative error by about +4 %. Moreover, all cloud events
with encountered graupel particles were studied and compared to events
without observed graupel particles. Overall, graupel particles seem to have
the largest impact on high crystal number-concentration conditions and show
relative errors in retrieved <span style="text-decoration: overline;">CWC</span>s that are higher than for
events without graupel particles. |
| first_indexed | 2024-04-12T05:54:36Z |
| format | Article |
| id | doaj.art-32a10f7db8964238926bd26ba5018fd5 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-12T05:54:36Z |
| publishDate | 2017-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-32a10f7db8964238926bd26ba5018fd52022-12-22T03:45:11ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482017-06-01102239225210.5194/amt-10-2239-2017Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systemsE. Fontaine0E. Fontaine1D. Leroy2A. Schwarzenboeck3J. Delanoë4A. Protat5F. Dezitter6A. Grandin7J. W. Strapp8L. E. Lilie9Université Clermont Auvergne, Laboratoire de Météorologie Physique, Aubière, FranceDepartment of Meteorology, University of Reading, Reading, UKUniversité Clermont Auvergne, Laboratoire de Météorologie Physique, Aubière, FranceUniversité Clermont Auvergne, Laboratoire de Météorologie Physique, Aubière, FranceLaboratoire Atmosphère, Milieux et Observations Spatiales, UVSQ, Guyancourt, FranceCenter for Australian Weather and Climate Research, Melbourne, AustraliaAirbus, Toulouse, FranceAirbus, Toulouse, FranceMet Analytics, Toronto, CanadaMet Analytics, Toronto, CanadaThis study presents the evaluation of a technique to estimate cloud condensed water content (CWC) in tropical convection from airborne cloud radar reflectivity factors at 94 GHz and in situ measurements of particle size distributions (PSDs) and aspect ratios of ice crystal populations. The approach is to calculate from each 5 s mean PSD and flight-level reflectivity the variability of all possible solutions of <i>m</i>(<i>D</i>) relationships fulfilling the condition that the simulated radar reflectivity factor (<b>T</b>-matrix method) matches the measured radar reflectivity factor. For the reflectivity simulations, ice crystals were approximated as oblate spheroids, without using a priori assumptions on the mass–size relationship of ice crystals. The CWC calculations demonstrate that individual CWC values are in the range ±32 % of the retrieved average <span style="text-decoration: overline;">CWC</span> value over all CWC solutions for the chosen 5 s time intervals. In addition, during the airborne field campaign performed out of Darwin in 2014, as part of the international High Altitude Ice Crystals/High Ice Water Content (HAIC/HIWC) projects, CWCs were measured independently with the new IKP-2 (isokinetic evaporator probe) instrument along with simultaneous particle imagery and radar reflectivity. Retrieved <span style="text-decoration: overline;">CWC</span>s from the <b>T</b>-matrix radar reflectivity simulations are on average 16 % higher than the direct CWC<sub>IKP</sub> measurements. The differences between the CWC<sub>IKP</sub> and averaged retrieved <span style="text-decoration: overline;">CWC</span>s are found to be primarily a function of the total number concentration of ice crystals. Consequently, a correction term is applied (as a function of total number concentration) that significantly improves the retrieved CWC. After correction, the retrieved <span style="text-decoration: overline;">CWC</span>s have a median relative error with respect to measured values of only −1 %. Uncertainties in the measurements of total concentration of hydrometeors are investigated in order to calculate their contribution to the relative error of calculated <span style="text-decoration: overline;">CWC</span> with respect to measured CWC<sub>IKP</sub>. It is shown that an overestimation of the concentration by about +50 % increases the relative errors of retrieved <span style="text-decoration: overline;">CWC</span>s by only +29 %, while possible shattering, which impacts only the concentration of small hydrometeors, increases the relative error by about +4 %. Moreover, all cloud events with encountered graupel particles were studied and compared to events without observed graupel particles. Overall, graupel particles seem to have the largest impact on high crystal number-concentration conditions and show relative errors in retrieved <span style="text-decoration: overline;">CWC</span>s that are higher than for events without graupel particles.http://www.atmos-meas-tech.net/10/2239/2017/amt-10-2239-2017.pdf |
| spellingShingle | E. Fontaine E. Fontaine D. Leroy A. Schwarzenboeck J. Delanoë A. Protat F. Dezitter A. Grandin J. W. Strapp L. E. Lilie Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems Atmospheric Measurement Techniques |
| title | Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems |
| title_full | Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems |
| title_fullStr | Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems |
| title_full_unstemmed | Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems |
| title_short | Evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems |
| title_sort | evaluation of radar reflectivity factor simulations of ice crystal populations from in situ observations for the retrieval of condensed water content in tropical mesoscale convective systems |
| url | http://www.atmos-meas-tech.net/10/2239/2017/amt-10-2239-2017.pdf |
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