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,

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 [email protected]

Outline Data description Climatology Clustering approach Stratospheric case Conclusions

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

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

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

Cirrus type Derived geometric parameters Top height Bottom height Thickness .

Cirrus altitude

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

Distribution of the parameters

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.

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

Position relative to tropopause Mimosa OHP

Flexpart (Stohl, 1998) Air mass history

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

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,

Documents

cirrus altitude slide

conclusions cirrus

cirrus type

tropopause mimosa ohp

x noise slide

subvisible cirrus

optical depth of cirrus

air mass history slide