Publication Abstracts

Alexandrov et al. 2020

Alexandrov, M.D., D.J. Miller, C. Rajapakshe, A. Fridlind, B. van Diedenhoven, B. Cairns, A.S. Ackerman, and Z. Zhang, 2020: Vertical profiles of droplet size distributions derived from cloud-side observations by the Research Scanning Polarimeter: Tests on simulated data. Atmos. Res., 239, 104924, doi:10.1016/j.atmosres.2020.104924.

The Research Scanning Polarimeter (RSP) is an airborne along-track scanner measuring the polarized and total reflectances with high angular resolution. It allows for accurate characterization of liquid water cloud droplet sizes using the rainbow structure in the polarized reflectance. RSP's observations also provide constraints on the cumulus cloud's 2D cross section, yielding estimates of its geometric shape. In this study for the first time we evaluate the possibility to retrieve vertical profiles of microphysical characteristics along the cloud side by combining these micro- and macrophysical retrieval methods. First we constrain cloud's geometric shape, then for each point on the bright side of its surface we collect data from different scans to obtain the multi-angle polarized reflectance at that point. The rainbow structures of the reflectances from multiple points yield the corresponding droplet size distributions (DSDs), which are then combined into vertical profiles. We present the results of testing the proposed profiling algorithm on simulated data obtained using large eddy simulations and 3D radiative transfer computations. The virtual RSP measurements were used for retrieval of DSD profiles, which then were compared to the actual data from the LES-model output. A cumulus congestus cloud was selected for these tests in preparation for analysis of real measurements made during the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex). We demonstrate that the use of the non-parametric Rainbow Fourier Transform (RFT) allows for adequate retrieval of the complex altitude-dependent bimodal structure of cloud DSDs.

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BibTeX Citation

@article{al01700t,
  author={Alexandrov, M. D. and Miller, D. J. and Rajapakshe, C. and Fridlind, A. and van Diedenhoven, B. and Cairns, B. and Ackerman, A. S. and Zhang, Z.},
  title={Vertical profiles of droplet size distributions derived from cloud-side observations by the Research Scanning Polarimeter: Tests on simulated data},
  year={2020},
  journal={Atmos. Res.},
  volume={239},
  pages={104924},
  doi={10.1016/j.atmosres.2020.104924},
}

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RIS Citation

TY  - JOUR
ID  - al01700t
AU  - Alexandrov, M. D.
AU  - Miller, D. J.
AU  - Rajapakshe, C.
AU  - Fridlind, A.
AU  - van Diedenhoven, B.
AU  - Cairns, B.
AU  - Ackerman, A. S.
AU  - Zhang, Z.
PY  - 2020
TI  - Vertical profiles of droplet size distributions derived from cloud-side observations by the Research Scanning Polarimeter: Tests on simulated data
JA  - Atmos. Res.
VL  - 239
SP  - 104924
DO  - 10.1016/j.atmosres.2020.104924
ER  -

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