TY - JOUR
T1 - Importance of accurate liquid water path for estimation of solar radiation in warm boundary layer clouds
T2 - An observational study
AU - Sengupta, Manajit
AU - Clothiaux, Eugene E.
AU - Ackerman, Thomas P.
AU - Kato, Seiji
AU - Min, Qilong
PY - 2003/9/15
Y1 - 2003/9/15
N2 - A 1-yr observational study of overcast boundary layer stratus at the U.S. Department of Energy Atmospheric Radiation Measurement Program Southern Great Plains site illustrates that surface radiation has a higher sensitivity to cloud liquid water path variations when compared to cloud drop effective radius variations. The mean, median, and standard deviation of observed cloud liquid water path and cloud drop effective radius are 0.120, 0.101, 0.108 mm and 7.38, 7.13, 2.39 μm, respectively. Liquid water path variations can therefore cause 3 times the variation in optical depth as effective radius-a direct consequence of the comparative variability displayed by the statistics of the two parameters. Radiative transfer calculations demonstrate that, over and above the impact of higher liquid water path variability on optical depth, normalized cloud forcing is 2 times as sensitive to liquid water path variations as it is to effective radius variations. Consequently, radiative transfer calculations of surface flux using observed liquid water paths and a fixed effective radius of 7.5 μm have a 79% correlation with observed values. This higher sensitivity of solar flux to liquid water path is a result of the regimes of natural occurrence of cloud liquid water paths and cloud drop effective radii.
AB - A 1-yr observational study of overcast boundary layer stratus at the U.S. Department of Energy Atmospheric Radiation Measurement Program Southern Great Plains site illustrates that surface radiation has a higher sensitivity to cloud liquid water path variations when compared to cloud drop effective radius variations. The mean, median, and standard deviation of observed cloud liquid water path and cloud drop effective radius are 0.120, 0.101, 0.108 mm and 7.38, 7.13, 2.39 μm, respectively. Liquid water path variations can therefore cause 3 times the variation in optical depth as effective radius-a direct consequence of the comparative variability displayed by the statistics of the two parameters. Radiative transfer calculations demonstrate that, over and above the impact of higher liquid water path variability on optical depth, normalized cloud forcing is 2 times as sensitive to liquid water path variations as it is to effective radius variations. Consequently, radiative transfer calculations of surface flux using observed liquid water paths and a fixed effective radius of 7.5 μm have a 79% correlation with observed values. This higher sensitivity of solar flux to liquid water path is a result of the regimes of natural occurrence of cloud liquid water paths and cloud drop effective radii.
UR - http://www.scopus.com/inward/record.url?scp=0242349786&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0242349786&partnerID=8YFLogxK
U2 - 10.1175/1520-0442(2003)016<2997:IOALWP>2.0.CO;2
DO - 10.1175/1520-0442(2003)016<2997:IOALWP>2.0.CO;2
M3 - Article
AN - SCOPUS:0242349786
SN - 0894-8755
VL - 16
SP - 2997
EP - 3009
JO - Journal of Climate
JF - Journal of Climate
IS - 18
ER -