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Andrew Heymsfield, Aaron Bansemer, Norman B. Wood, Guosheng Liu, Simone Tanelli, Ousmane O. Sy, Michael Poellot, and Chuntao Liu

sample volumes of the particle probes compared to those of the radars. The use of the HVPS-3 probe greatly increases the sample volume compared to measurements obtained from other aircraft-radar “collocation” studies. The HVPS-3 has a sample volume that is 73% larger than that of the 2D-P probe that has been used in earlier studies. Further discussion of this point is given in section 3 and in the conclusions. b. Mass-flux conservation through the melting layer The second method used to derive

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David J. Purnell and Daniel J. Kirshbaum

precipitation enhancement (OPE) apply to most mountain ranges, including the Olympics. The amplitude of OPE depends on the impinging vertically integrated horizontal moisture flux (or “influx,” I ) (e.g., Neiman et al. 2002 ). Larger I favors increased terrain-forced condensation and, in turn, precipitation. Also, the nondimensional mountain height ( , where is the crest height, and N and U are the mean Brunt–Väisälä frequency and mean cross-barrier wind speed in the subcrest layer) broadly

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Robert Conrick and Clifford F. Mass

disdrometers was documented by Jaffrain and Berne (2011) , who demonstrated that number concentration uncertainty was less than 5% and D 0 uncertainty less than 7% at temporal averages exceeding 10 min. Thus, there is confidence that the observing systems used in this study are sufficiently accurate for model evaluation. 3. Results of OLYMPEX wintertime simulations a. Fidelity of incoming moisture flux during the OLYMPEX project Before evaluating model microphysics, it is important to evaluate the

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William Ryan Currier, Theodore Thorson, and Jessica D. Lundquist

little incoming longwave radiation, corresponding to too much or not enough melt in our model simulations. Furthermore, we evaluated WRF incoming radiation at the Snoqualmie Pass energy balance tower and found biases in WRF shortwave and longwave radiation to be greater than empirical estimates and to be in opposite directions. See appendix B for more details. Another nontrivial decision was the choice in wind speed. In this region, we found modeled turbulent fluxes to be a significant energy input

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Aaron R. Naeger, Brian A. Colle, Na Zhou, and Andrew Molthan

partly attributed to initial conditions, in addition to choice of BMP and model resolution. Martin et al. (2018) attributed precipitation deficiencies for AR simulations from the WRF Model to low biases in the low-level water vapor flux. Thus, there remains a strong need to improve forecasts of extreme precipitation events such as ARs in an effort to mitigate flood risk and damage from these storms. The suite of intensive instrumentation deployed during the recent Olympic Mountains Experiment

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Joseph P. Zagrodnik, Lynn A. McMurdie, and Robert A. Houze Jr.

south of the warm-frontal region sometimes contains an extensive narrow zone of water vapor flux commonly called an “atmospheric river” ( Newell et al. 1992 ; Zhu and Newell 1994 , 1998 ; Ralph et al. 2004 ; Warner et al. 2012 ). Behind the cold front, the postfrontal sector consists mainly of small-scale convective showers, which sometimes form into bands or other mesoscale features. This study focuses on the sectors with predominantly stratiform precipitation. Postfrontal convection is left to

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Joseph P. Zagrodnik, Lynn A. McMurdie, Robert A. Houze Jr., and Simone Tanelli

lee side is very dry ( Fig. 1 ). In a recent study using OLYMPEX data, Purnell and Kirshbaum (2018 , hereafter PK18 ) used rain gauges and operational National Weather Service radars to show that orographic precipitation distributions are highly sensitive to the upstream static stability, horizontal moisture flux, and the presence of preexisting precipitation associated with the large-scale synoptic storm sectors. McMurdie et al. (2018) found that when the large-scale conditions resembled warm

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Hannah C. Barnes, Joseph P. Zagrodnik, Lynn A. McMurdie, Angela K. Rowe, and Robert A. Houze Jr.

shown in Fig. 11a . This oscillating pattern was also seen in the Z DR data ( Fig. 11d ). Regions of increased Z H and Z DR are associated with larger raindrops. There are several microphysical processes that could account for an increase in the size of raindrops beneath the crest of the waves. First, the waviness in the bright band suggests that liquid water might have been fluxed above the freezing level and, as discussed in section 5b , fostered riming. Being larger and/or denser, such

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Annareli Morales, Hugh Morrison, and Derek J. Posselt

condition. A positive definite advection scheme is used, and a Rayleigh damper with damping coefficient of 0.0003 s −2 is applied to the top 4 km to prevent reflection of vertically propagating gravity waves. Although interactions of radiation with the mountain surface can result in the forcing of mesoscale mountain circulations, for example, mountain-valley winds, our focus is on the interaction of microphysics and dynamics. Thus, radiative transfer and surface heat flux parameterizations are

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Qian Cao, Thomas H. Painter, William Ryan Currier, Jessica D. Lundquist, and Dennis P. Lettenmaier

, L. , and Y. Qian , 2003 : The sensitivity of precipitation and snowpack simulations to model resolution via nesting in regions of complex terrain . J. Hydrometeor. , 4 , 1025 – 1043 , https://doi.org/10.1175/1525-7541(2003)004<1025:TSOPAS>2.0.CO;2 . 10.1175/1525-7541(2003)004<1025:TSOPAS>2.0.CO;2 Liang , X. , D. P. Lettenmaier , E. Wood , and S. Burges , 1994 : A simple hydrologically based model of land-surface water and energy fluxes for general-circulation models . J. Geophys

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