TY - JOUR
T1 - Satellite retrieval of cloud condensation nuclei concentrations by using clouds as CCN chambers
AU - Rosenfeld, Daniel
AU - Zheng, Youtong
AU - Hashimshoni, Eyal
AU - Pöhlker, Mira L.
AU - Jefferson, Anne
AU - Pöhlker, Christopher
AU - Yu, Xing
AU - Zhu, Yannian
AU - Liu, Guihua
AU - Yue, Zhiguo
AU - Fischman, Baruch
AU - Li, Zhanqing
AU - Giguzin, David
AU - Goren, Tom
AU - Artaxo, Paulo
AU - Barbosa, Henrique M.J.
AU - Pöschl, Ulrich
AU - Andreae, Meinrat O.
PY - 2016/5/24
Y1 - 2016/5/24
N2 - Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day.
AB - Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Validation against ground-based CCN instruments at Oklahoma, at Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25° restricts the satellite coverage to ∼25% of the world area in a single day.
KW - Ccn concentrations
KW - Cloud-aerosol interactions
KW - Convective clouds
KW - Satellite remote sensing
UR - http://www.scopus.com/inward/record.url?scp=84969785574&partnerID=8YFLogxK
U2 - 10.1073/pnas.1514044113
DO - 10.1073/pnas.1514044113
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AN - SCOPUS:84969785574
SN - 0027-8424
VL - 113
SP - 5828
EP - 5834
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 21
ER -