Maritime Cloud and Drizzle Microphysical Properties Retrieved From Ship-Based Observations During MAGIC

摘要

The Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign provided a wealth of information looking at the stra-tocumulus to cumulus transition (SCT) over the Eastern-North Pacific (ENP), however, the lack of cloud in situ measurements gave limited information. Using the observations of Marine W-band ARM cloud radar, ceilometer, and three-channel microwave radiometer onboard the ship, we retrieve the single-layer, low-level cloud-droplet effective radius and drizzle median radius (r_c and r_(m,d)), number concentration (N_c and N_d), and liquid water content (LWC_c and LWC_d) using the methods in Wu et al. Based on the results during MAGIC, we found that both cloud base and top heights increase approximately 0.75 km from Los Angeles (LA) until cloud breakup (CB) before leveling off. Low cloud fractions (CFs) ranged from ～85% halfway between LA and CB to ～20% near Hawaii. Retrieved r_c values decreased approximately 2 μm from peak CF to Hawaii while r_(m,d) increased more than 20 μm over the same path. Mean values of r_c, r_(m,d), N_c, N_d, LWC_c, and LWC_d during MAGIC are 12.1 μm, 55.8 μm, 97.9 cm~(-3), 0.09 cm~(-3), 0.40 g m~(-3), and 0.05 g m~(-3), respectively. Compared to the mean values over the Azores in Wu et al. the mean cloud and drizzle microphysical properties during MAGIC, except LWC_d which is roughly equal, are greater due to higher liquid water path and warmer sea surface temperature. This information allows for a better understanding of the SCT over the ENP and can be used to better improve model simulations.