Peer Review10.5194/egusphere-2023-2858-ac2
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Jianqi Zhao
- 22 Apr 2024
TL;DR: Aerosol-cloud interactions in liquid-phase clouds over eastern China and its adjacent ocean in winter
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Abstract: <strong class="journal-contentHeaderColor">Abstract.</strong> This study aims to explore aerosol-cloud interactions in liquid-phase clouds over eastern China (EC) and its adjacent ocean (ECO) in winter based on WRF-Chem-SBM model which couples a spectral-bin cloud microphysics (SBM) and online aerosol module (MOSAIC) as well as the four-dimensional assimilation approach. The model evaluation demonstrates that assimilation has a predominantly favorable impact on the simulation, and the model reasonably reproduces the satellite-retrieved cloud parameters. Differences in meteorological, topographic and aerosol conditions lead to differences in EC and ECO aerosol-cloud processes. Multiple atmospheric supersaturation pathways and abundant aerosols in EC enable more aerosols to be activated, but limited water content makes them difficult to grow into large droplets. While atmospheric supersaturation pathway and aerosol number concentration (N<sub>aero</sub>) limit the cloud droplet number concentration (N<sub>d</sub>) in ECO, the relatively abundant water content enables more large cloud droplets to exist here. EC and ECO cloud liquid water content (CLWC) exhibit close variation trends with N<sub>d</sub>, but differences in aerosols, supersaturation pathways, and water vapor conditions result in distinctions in CLWC variations and the differentiation between precipitation and non-precipitation clouds in the two regions. Meteorological conditions suitable for EC cloud development include (1) weak winds and strong surface radiative forcing cooling, (2) moist air brought by strong easterly winds, (3) cooling and topographic uplift caused by strong northerly winds, and (4) strong updrafts. Meteorological conditions suitable for ECO cloud development include (1) aerosol-rich and not excessively dry airflow from moderate westerly wind, (2) cooling caused by northerly winds, and (3) updrafts. In general, the effect of cooling on aerosol activation is more pronounced compared to humidification in EC and ECO. Moreover, the aerosol conditions suitable for aerosol activation and CLWC increase are similar overall, with the difference being that aerosol activation is strongest under moderate N<sub>aero</sub> conditions, whereas high CLWC to N<sub>aero</sub> ratios are often seen under low N<sub>aero</sub> conditions in addition to moderate N<sub>aero</sub> conditions.
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Figures
Figure 5. MODIS and simulated CER (a and b, in μm), Nd (c and d, in cm-3), CLWP (e and f, in g·m-2), COT (g and h, dimensionless), CTH (i and j, in m), CTP (k and l, in hPa) and CTT (m and n, in °C) distributions (r and RMSE on top right represent the spatial correlation coefficient and root mean square error of the simulated and MODIS data, where RMSE is in 255 the same unit as the variable in the figure) 
Figure 4. Temporal variations of near-surface PM2.5 observed (black line) and simulated before (blue line) and after (red line) assimilation of meteorological fields, at each site. The r and p values represent the correlation and significance of the observation and simulation, respectively, and subscripts “bf” and “af” represent simulated before and after assimilation 245 
Figure 8. EC and ECO aerosol number concentration (in cm-3, a-b), Nd in liquid-phase cloud (in cm-3, c-d), atmospheric 310 supersaturation (in %, e-f), CER (in μm, g-h), water vapor content (in g·m-3, i-j) and vertical wind speed (in m·s-1, k-l) distributions 
Figure 11. Probability density distribution functions (sum of probabilities corresponding to 1 for each Nd value) and means (lines in the figures) of CLWC relative to Nd (a, c, e, and g), as well as the CER values (b, d, f, and h, corresponding to the left and bottom axis) and their mean changes relative to Nd (lines in the figures, corresponding to the right and bottom axis) of precipitation clouds (a-b and e-f) and non-precipitation clouds (c-d and g-h) in EC (a-d) and ECO (e-h) 395 
Figure 7. EC (a-d and i-l) and ECO (e-h and m-p) sulfate, nitrate, ammonium, chloride, sodium, OC, BC and other inorganic (dust) aerosols (in μg·m-3) distributions 
Figure 10. Variation of EC (a-g) and ECO (h-n) Nd to Naero ratio (unit: cm-3·cm3) with Naero at different U-wind (a and h), Vwind (b and i), W-wind (c and j), temperature (d and k), water vapor content (e and l), temperature variation (f and m) and water vapor variation (g and n)
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