TY - JOUR
T1 - Investigation of the marine boundary layer cloud and CCN properties under coupled and decoupled conditions over the azores
AU - Dong, Xiquan
AU - Schwantes, Adam C.
AU - Xi, Baike
AU - Wu, Peng
N1 - Funding Information:
The data were obtained from the Atmospheric Radiation Measurement (ARM) Program sponsored by the U.S. Department of Energy (DOE) Office of Energy Research, Office of Health and Environmental Research, Environmental Sciences Division. The data can be downloaded from http://www.archive. arm.gov/. This study was primarily supported by DOE ASR project with award DE-SC0008468, NASA CERES project under grant NNX13AK29G, and NASA EPSCoR CAN under grant NNX11AM15A at the University of North Dakota. Special thanks to Francine Dong who helped to design Figure 7.
Publisher Copyright:
© 2015. American Geophysical Union. All Rights Reserved.
PY - 2015
Y1 - 2015
N2 - Six coupled and decoupled marine boundary layer (MBL) clouds were chosen from the 19 month Atmospheric Radiation Measurement Mobile Facility data set over the Azores. Thresholds of liquid water potential temperature difference ΔθL < 0.5 K (>0.5 K) and total water mixing ratio difference Δqt < 0.5 g/kg (>0.5 g/kg) below the cloud base were used for selecting the coupled (decoupled) cases. A schematic diagram was given to demonstrate the coupled and decoupled MBL vertical structures and how they associate with nondrizzle, virga, and rain drizzle events. Out of a total of 2676 5 min samples, 34.5% were classified as coupled and 65.5% as decoupled, 36.2% as nondrizzle and 63.8% as drizzle (47.7% as virga and 16.1% as rain), and 33.4% as daytime and 66.6% as nighttime. The decoupled cloud layer is deeper (0.406 km) than coupled cloud layer (0.304 km), and its liquid water path and cloud droplet effective radius (re) values (122.1 gm-2 and 13.0 μm) are higher than coupled ones (83.7 gm-2 and 10.4 μm). Conversely, decoupled stratocumuli have lower cloud droplet number concentration (Nd) and surface cloud condensation nucleus (CCN) concentration (NCCN) (74.5 cm-3 and 150.9 cm-3) than coupled stratocumuli (111.7 cm-3 and 216.4 cm-3). The linear regressions between re and Nd with NCCN have demonstrated that coupled re and Nd strongly depend on NCCN and have higher correlations (-0.56 and 0.59) with NCCN than decoupled results (-0.14 and 0.25). The MBL cloud properties under nondrizzle and virga drizzle conditions are similar to each other but significantly different to those of rain drizzle.
AB - Six coupled and decoupled marine boundary layer (MBL) clouds were chosen from the 19 month Atmospheric Radiation Measurement Mobile Facility data set over the Azores. Thresholds of liquid water potential temperature difference ΔθL < 0.5 K (>0.5 K) and total water mixing ratio difference Δqt < 0.5 g/kg (>0.5 g/kg) below the cloud base were used for selecting the coupled (decoupled) cases. A schematic diagram was given to demonstrate the coupled and decoupled MBL vertical structures and how they associate with nondrizzle, virga, and rain drizzle events. Out of a total of 2676 5 min samples, 34.5% were classified as coupled and 65.5% as decoupled, 36.2% as nondrizzle and 63.8% as drizzle (47.7% as virga and 16.1% as rain), and 33.4% as daytime and 66.6% as nighttime. The decoupled cloud layer is deeper (0.406 km) than coupled cloud layer (0.304 km), and its liquid water path and cloud droplet effective radius (re) values (122.1 gm-2 and 13.0 μm) are higher than coupled ones (83.7 gm-2 and 10.4 μm). Conversely, decoupled stratocumuli have lower cloud droplet number concentration (Nd) and surface cloud condensation nucleus (CCN) concentration (NCCN) (74.5 cm-3 and 150.9 cm-3) than coupled stratocumuli (111.7 cm-3 and 216.4 cm-3). The linear regressions between re and Nd with NCCN have demonstrated that coupled re and Nd strongly depend on NCCN and have higher correlations (-0.56 and 0.59) with NCCN than decoupled results (-0.14 and 0.25). The MBL cloud properties under nondrizzle and virga drizzle conditions are similar to each other but significantly different to those of rain drizzle.
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U2 - 10.1002/2014JD022939
DO - 10.1002/2014JD022939
M3 - Article
AN - SCOPUS:84941082433
VL - 120
SP - 6179
EP - 6191
JO - Journal of Geophysical Research: Atmospheres
JF - Journal of Geophysical Research: Atmospheres
SN - 2169-897X
IS - 12
ER -