Isokinetic TWC Evaporator Probe: Development of the IKP2 and Performance Testing for the HAIC-HIWC Darwin 2014 and Cayenne Field Campaigns

Strapp, J. W.; Lilie, Lyle; Ratvasky, Thomas P.; Davison, Craig R.; Dumont, Christopher

doi:10.2514/6.2016-4059

Cited by 59 publications

(60 citation statements)

References 10 publications

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“…Because of this uncertainty, observed samples with TWC ≤ 0.1 g m −3 are excluded from this study. Further details about the microphysical instrumentation used on the Falcon 20 and data processing from the OAPs and IKP2 may be found in L16, L17, and Strapp et al (2016b).…”

Section: Observationsmentioning

confidence: 99%

“…Bulk TWC measurements were made with an isokinetic evaporator probe (IKP) first designed and developed by the National Research Council of Canada (NRC) and then reengineered as the IKP2 by Science Engineering Associates (SEA) Inc. and NRC to operate within the constraints of the Falcon 20 aircraft (Davison et al, 2008Strapp et al, 2016b). The probe was designed specifically for the measurement of high-altitude, high-IWC conditions, with a target accuracy of 20 %.…”

Section: Observationsmentioning

confidence: 99%

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A ubiquitous ice size bias in simulations of tropical deep convection

et al. 2017

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Abstract. The High Altitude Ice Crystals -High Ice Water Content (HAIC-HIWC) joint field campaign produced aircraft retrievals of total condensed water content (TWC), hydrometeor particle size distributions (PSDs), and vertical velocity (w) in high ice water content regions of mature and decaying tropical mesoscale convective systems (MCSs). The resulting dataset is used here to explore causes of the commonly documented high bias in radar reflectivity within cloud-resolving simulations of deep convection. This bias has been linked to overly strong simulated convective updrafts lofting excessive condensate mass but is also modulated by parameterizations of hydrometeor size distributions, single particle properties, species separation, and microphysical processes. Observations are compared with three Weather Research and Forecasting model simulations of an observed MCS using different microphysics parameterizations while controlling for w, TWC, and temperature. Two popular bulk microphysics schemes (Thompson and Morrison) and one bin microphysics scheme (fast spectral bin microphysics) are compared. For temperatures between −10 and −40 • C and TWC > 1 g m −3 , all microphysics schemes produce median mass diameters (MMDs) that are generally larger than observed, and the precipitating ice species that controls this size bias varies by scheme, temperature, and w. Despite a much greater number of samples, all simulations fail to reproduce observed high-TWC conditions (> 2 g m −3 ) between −20 and −40 • C in which only a small fraction of condensate mass is found in relatively large particle sizes greater than 1 mm in diameter. Although more mass is distributed to large particle sizes relative to those observed across all schemes when controlling for temperature, w, and TWC, differences with observations are significantly variable between the schemes tested. As a result, this bias is hypothesized to partly result from errors in parameterized hydrometeor PSD and single particle properties, but because it is present in all schemes, it may also partly result from errors in parameterized microphysical processes present in all schemes. Because of these ubiquitous ice size biases, the frequently used microphysical parameterizations evaluated in this study inherently produce a high bias in convective reflectivity for a wide range of temperatures, vertical velocities, and TWCs.

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Section: Observationsmentioning

confidence: 99%

Section: Observationsmentioning

confidence: 99%

A ubiquitous ice size bias in simulations of tropical deep convection

et al. 2017

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“…During the High Altitude Ice Crystals (HAIC; Dezitter et al, 2013)/High Ice Water Content (HIWC; Strapp et al, 2016) airborne field campaign performed out of Darwin, the from SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) measured on the same aircraft 94 GHz Z, PSD, aspect ratios of hydrometeors, and independently CWC. The objective of our study is to use this comprehensive HAIC/HIWC dataset to evaluate the method presented by Fontaine et al (2014).…”

Section: Introductionmentioning

confidence: 99%

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

Fontaine

Leroy²,

Schwarzenböeck³

et al. 2017

Atmos. Meas. Tech.

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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 from each 5 s mean PSD and flight-level reflectivity the variability of all possible solutions of m(D) relationships fulfilling the condition that the simulated radar reflectivity factor (T-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 CWC 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 CWCs from the T-matrix radar reflectivity simulations are on average 16 % higher than the direct CWC IKP measurements. The differences between the CWC IKP and averaged retrieved CWCs 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 CWCs 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 CWC with respect to measured CWC IKP . It is shown that an overestimation of the concentration by about +50 % increases the relative errors of retrieved CWCs 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 CWCs that are higher than for events without graupel particles.

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“…The probe was downsized to a second version (IKP2) for use on the Falcon 20 aircraft, and then successfully tested in a series of wind tunnel experiments, exposing it to IWCs as high as 15 g m −3 under highaltitude flight conditions . Accuracy estimates to date have been provided by Davison et al (2016) and Strapp et al (2016b). System accuracy estimates predict no more than 10 % error at all TWC values larger than about 0.1 g m −3 for temperatures colder than −30 • C. At warmer temperatures, uncertainty rises due to the increasing magnitude of the background humidity, which must be subtracted from the IKP2 humidity signal.…”

Section: In Situ Total Water Content Measurementsmentioning

confidence: 99%