TY - JOUR
T1 - Evaluation of long-term surface-retrieved cloud droplet number concentration with in situ aircraft observations
AU - Lim, Kyo Sun Sunny
AU - Riihimaki, Laura
AU - Comstock, Jennifer M.
AU - Schmid, Beat
AU - Sivaraman, Chitra
AU - Shi, Yan
AU - McFarquhar, Greg M.
N1 - We greatly express our thanks to Haf Jonsson and Andy Vogelmann for their help providing in situ airborne mea surement data. Our thanks also extend to the value-added products (VAP) science sponsors and scientists, Qilong Min, Allison McComiskey, Graham Feingold, and David D. Turner, for their helpful discussions and contributions to VAP development. The first author would like to express her thanks to Hyeyum Hailey Shin, Zhe Feng, and Jinho Yoon for their helpful review and suggestion. This research was supported by the Office of Biological and Environmental Research of the U.S. Department of Energy as part of the Atmospheric Radiation Measurement (ARM) Climate Research Facility, an Office of Science user facility. Data were obtained from the Atmospheric Radiation Measurement (ARM) Climate Research Facility, a U.S. Department of Energy Office of Science user facility sponsored by the Office of Biological and Environmental Research. The surface retrieval and the in situ aircraft data during RACORO field campaign used in this study can be freely downloadable at https://www.arm.gov/data/vaps and https://www.arm.gov/campaigns/ aaf2009racoro, respectively. The Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC05-76RLO 1830.
PY - 2016/3/16
Y1 - 2016/3/16
N2 - A new operational retrieval of cloud droplet number concentration (ND) at cloud base has been produced from surface remote sensors at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site for 13 years from January 1998 to January 2011. The retrieval is based on surface radiometer measurements of cloud optical depth from the multifilter rotating shadow band radiometer and liquid water path from the microwave radiometer (MWR). It is only applicable for single-layered overcast warm (stratus or stratocumulus) clouds. Evaluation with in situ aircraft measurements during the extended-term aircraft field campaign, Routine ARM Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO), shows that the retrieved ND robustly reproduces the primary mode of the in situ measured probability density function (PDF) but produces too wide a distribution, primarily caused by frequent high cloud droplet number concentration. Our analysis shows that the error in the MWR retrievals at low liquid water paths is one possible reason for this deficiency. Modification through the diagnosed liquid water path from the coordinate solution improves not only the PDF of the retrieved ND but also the relationship between the cloud droplet number concentration and cloud droplet effective radius. Consideration of entrainment effects rather than assuming an adiabatic cloud improves the values of the ND retrieval by reducing the magnitude of cloud droplet number concentration. Aircraft measurements and retrieval comparisons suggest that retrieving the vertical distribution of cloud droplet number concentration and effective radius is feasible with an improvement of the parameter representing the mixing effects between environment and clouds and with a better understanding of the effect of mixing degree on cloud properties.
AB - A new operational retrieval of cloud droplet number concentration (ND) at cloud base has been produced from surface remote sensors at the Atmospheric Radiation Measurement (ARM) Southern Great Plains site for 13 years from January 1998 to January 2011. The retrieval is based on surface radiometer measurements of cloud optical depth from the multifilter rotating shadow band radiometer and liquid water path from the microwave radiometer (MWR). It is only applicable for single-layered overcast warm (stratus or stratocumulus) clouds. Evaluation with in situ aircraft measurements during the extended-term aircraft field campaign, Routine ARM Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO), shows that the retrieved ND robustly reproduces the primary mode of the in situ measured probability density function (PDF) but produces too wide a distribution, primarily caused by frequent high cloud droplet number concentration. Our analysis shows that the error in the MWR retrievals at low liquid water paths is one possible reason for this deficiency. Modification through the diagnosed liquid water path from the coordinate solution improves not only the PDF of the retrieved ND but also the relationship between the cloud droplet number concentration and cloud droplet effective radius. Consideration of entrainment effects rather than assuming an adiabatic cloud improves the values of the ND retrieval by reducing the magnitude of cloud droplet number concentration. Aircraft measurements and retrieval comparisons suggest that retrieving the vertical distribution of cloud droplet number concentration and effective radius is feasible with an improvement of the parameter representing the mixing effects between environment and clouds and with a better understanding of the effect of mixing degree on cloud properties.
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U2 - 10.1002/2015JD024082
DO - 10.1002/2015JD024082
M3 - Article
AN - SCOPUS:84959932952
SN - 0148-0227
VL - 121
SP - 2318
EP - 2331
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
IS - 5
ER -