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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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doi:10.5194/amt-2016-336
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
24 Oct 2016
Review status
This discussion paper is under review for the journal Atmospheric Measurement Techniques (AMT).
Radar Reflectivity Factors Simulations of Ice Crystal Populations from In-Situ Observations for the Retrieval of Condensed Water Content in Tropical Mesoscale Convective Systems
Emmanuel Fontaine1,6, Delphine Leroy1, Alfons Schwarzenboeck1, Julien Delanoë2, Alain Protat3, Fabien Dezitter4, Alice Grandin4, John Walter Strapp5, and Lyle Edward Lilie5 1Université Blaise Pascal, Laboratoire de Météorologie Physique, Aubière, France
2Laboratoire Atmosphère, Milieux et Observations Spatiales, UVSQ, Guyancourt, France
3Center for Australian Weather and Climate Research, Melbourne, Australia
4Airbus, Toulouse, France
5Met Analytics, Toronto, Canada
6University of Reading, United Kingdom
Abstract. 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 the variability of 5 second average PSD CWCs and all possible solutions of corresponding m(D) relationships fulfilling the condition that the simulated radar reflectivity factors (T-matrix method) matches the measured reflectivity. 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 measured CWC values are in the range ±32 % of the average CWC value: averaged over all CWC solutions for the chosen 5s time intervals. In addition, during the airborne field campaign performed out of Darwin in 2014, as part of the international High Altitude Ice Crystals (HAIC) – High Ice Water Content (HIWC) projects, CWCs were measured directly with the new IKP-2 (isokinetic evaporator probe) instrument along with simultaneous particle imagery and radar reflectivity. Averaged CWC retrieved from the radar reflectivity simulations are roughly 16 % higher than the IKP-2 CWC measurements. The differences between the IKP-2 and PSD derived CWCs from the entire set of realistic m(D) solutions for T-matrix retrievals is found to be 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 CWC have a median error relative to measured values of only −1 %.

Citation: Fontaine, E., Leroy, D., Schwarzenboeck, A., Delanoë, J., Protat, A., Dezitter, F., Grandin, A., Strapp, J. W., and Lilie, L. E.: Radar Reflectivity Factors Simulations of Ice Crystal Populations from In-Situ Observations for the Retrieval of Condensed Water Content in Tropical Mesoscale Convective Systems, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-336, in review, 2016.
Emmanuel Fontaine et al.
Emmanuel Fontaine et al.
Emmanuel Fontaine et al.

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Short summary
In this study we evaluate a method to estimate cloud water content (CWC) knowing cloud reflectivity. Ice hydrometeors are replace by ice oblate spheroids to simulate their reflectivity. There is no assumption on the relation between mass and their size. Then, a broad range of CWCs are compared with direct measurements of CWC. The accuracy of the method is ~ ±32 %. This study is performed in areas of convective clouds where reflectivity and CWC are especially high, what makes it unique.
In this study we evaluate a method to estimate cloud water content (CWC) knowing cloud...
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