Assessment of BCP (Backscatter CloudProbe) and BCPD (Backscatter Cloudprobe with Polarization Detection) Aircraft Observations by Validation against Ice Water Content from the Nevzorov Probe.

The BCP and BCPD instruments were developed (Beswick et al. 2014, 2015 and Baumgardner et al. 2017) to allow the IAGOS (European In-service Aircraft for Global Observations) community to exclude periods the aircraft were flying in clouds from the measurements. The instruments are however capable of giving size resolved number concentration measurements of cloud particles and large aerosols such as e.g. dust particles. It can therefore provide more information than warnings to pilots of dangerous flying conditions which are typically found in deep convective clouds and their outflow regions. The warnings to pilots could avoid issues of engine roll back due to encounters with areas of high ice water content, air frame icing and sensor degradation due to high ice crystal concentrations.
Several commercial airliners are fitted with BCP/BCPD instruments and have been flying for several years collecting a large database of encounters with ice clouds at cruise altitude and water and mixed-phase clouds during take off and landings. In real time this could give warnings to pilots as mentioned above. The collected database could create a very useful near global dataset of cirrus cloud properties encountered during flights for comparisons with numerical weather prediction models and also satellite measurements as well as give a near global climatology of ice water content for weather and climate models. Cirrus clouds are important for climate modulation and can sometimes be difficult to measure with satellites.
The instrument has been shown to work well in liquid water clouds (Beswick et al. 2014, 2015, Baumgardner et al. 2017). Here we will report on the comparison of BCP and BCPD measurements on the FAAM BAe-146 aircraft with simultaneous measurements of ice water content using the Nevzorov probe (Korolev et al. 1998, 2013) to determine how well ice water content can be detected by the IAGOS BCP system.

References
Baumgardner, D., Newton, R., Freer, M., and Axisa, D. 2017: The Backscatter Cloudprobe with Polarization Detection: A New Aircraft Ice Water Detector, AIAA 2017
Beswick, K., Baumgardner, D., Gallagher, M., Volz-Thomas, A., Nedelec, P., Wang, K.-Y., and Lance, S., 2014: The backscatter cloud probe – a compact low-profile autonomous optical spectrometer, Atmos. Meas. Tech., 7, 1443-1457, doi:10.5194/amt-7-1443-2014.
Beswick, K., Baumgardner, D., Gallagher, M., Raga, G.B., Minnis, P., Spangenberg, D. A., Volz-Thomas, A., Nedelec, P., Wang, K-Y., 2015: Properties of Small Cirrus Ice Crystals from Commercial Aircraft Measurements and Implications for Flight Operations, Tellus B, 67, 27876, http://dx.doi.org/10.3402/tellusb.v67.27876.
Korolev, A. V., Strapp, J. W., Isaac, G. A., and Nevzorov, A. N.: The Nevzorov airborne hot-wire LWC-TWC probe: principle of operation and performance characteristics, J. Atmos. Ocean. Tech., 15, 1495–1510, 1998.
Korolev, A. V., Strapp, J. W., Isaac, G. A., and Emery, E.: Improved airborne hot-wire measurements of ice water content in clouds, J. Atmos. Ocean. Tech., 30, 2121–2131, 2013.