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,
Dec 19, 2015
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- Slide 1
- 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]
- Slide 2
- Outline Data description Climatology Clustering approach Stratospheric case Conclusions
- Slide 3
- 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
- Slide 4
- Cirrus Climatology Mid-latitude (44N) (from Goldfarb et al., GRL, 2001) Southern tropic (21S) (from Cadet et al., GRL, 2002)
- Slide 5
- Cirrus at OHP 1997-1999 T < T A, B, C = sub-visible cirrus < 0.03
- Slide 6
- Cirrus type Derived geometric parameters Top height Bottom height Thickness .
- Slide 7
- Cirrus altitude
- Slide 8
- 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
- Slide 9
- Distribution of the parameters
- Slide 10
- 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.
- Slide 11
- Cirrus into the stratosphere Keckhut et al., Atmos. Chem. Phys., 5, 3407-3414, 2005 January 20th, 2000 thermal tropopause threshold=3x noise
- Slide 12
- Position relative to tropopause Mimosa OHP
- Slide 13
- Flexpart (Stohl, 1998) Air mass history
- Slide 14
- 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
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