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Cirrus climatology at mid-latitude observed with Lidar P. Keckhut, S. Bekki, A. Hauchecorne, F. Borchi, A. Colette, C. David, and J. Jumelet Climate, Ozone, and Sun Team Service dAronomie/IPSL, France Keckhut@aerov.jussieu.fr

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Outline Data description Climatology Clustering approach Stratospheric case Conclusions

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Lidar Observations were performed during nightime with a powerful system (350 mJ/pulse and telescope with 20 cm at 1 wavelength (532 nm) used a give lidar ratio of 18 sr -1 Detection of optical thickness of 0.001 Lidar observations are obtained at Observatory of Haute- Provence (44N, 6E), France since 1994 continuously180 profiles/year

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Cirrus Climatology Mid-latitude (44N) (from Goldfarb et al., GRL, 2001) Southern tropic (21S) (from Cadet et al., GRL, 2002)

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Cirrus at OHP 1997-1999 T < T A, B, C = sub-visible cirrus < 0.03

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Cirrus type Derived geometric parameters Top height Bottom height Thickness .

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Cirrus altitude

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Dynamical tropopause estimates Dynamical tropopause estimated from the Advection Mimosa model PV advection on isentropic surface 6h ECWWF input T106 Grid of 37x37 km Tropopause defined as 1.6-2 PV threshold (Blue) Hauchecorne et al, JGR, 2002

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Distribution of the parameters

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Cirrus classes ClassIIIIII Occurrence (%)362735 Height (km)8.6 0.99.8 0.711.5 0.9 Altitude relative to tropopause -78-0.513+716 Thickness (km)0.9 0.63.2 0.90.9 0.6 Temperature (C)-41 6-50 6-58 6 Keckhut et al., J. Appl. Meteo., 2005 (in press) Multivariate analyses Princ. Comp. Analy. Cluster methods Lin. Discrim. Analys.

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Cirrus into the stratosphere Keckhut et al., Atmos. Chem. Phys., 5, 3407-3414, 2005 January 20th, 2000 thermal tropopause threshold=3x noise

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Position relative to tropopause Mimosa OHP

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Flexpart (Stohl, 1998) Air mass history

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Conclusions Cirrus are observed for 50 %. Optical depth of cirrus range from 1 to 0.001. The lowest range corresponds to the detection threshold. Geometric cirrus characteristics can be deduced with lidar, and allow clustering. 3 cirrus classes have been found. 1 case located in the stratosphere has been described that came isentropically from the subtropical troposphere. Will improve our clustering in adding new parameters: temporal variability, lidar ratio, photometer-radiometer (XY0044-Thuillier et al., XY0045-Cadet et al.) Investigate further the cirrus in the UTLS