The freeze-drying of ensembles of air parcels in determining stratospheric water Department of Environmental Sciences Institute of Environmental and Natural.

The freeze-drying of ensembles of air parcels in determining stratospheric water

Department of Environmental Sciences

Institute of Environmental and Natural Sciences

Lancaster University

Chuansen Ren & Robert MacKenzie

Outline

Dehydration near the tropical tropopause and the development of parameterization

Comparison with satellite measurementsDehydration cases in winter and summerSummary and perspectiveAcknowledgements

flight measurements

Water vapour

Saturation water vapour

Particle backscatter

Comparison of modelled size distribution (blue line) with APE-THESEO in-situ measurements on February 24, 1999 (black lines, Thomas et al. (2002)) near the tropopause. The model was tried to match the observations spatially and temporally.

Number density of ice particles as a function of the vertical velocity for 3 freezing temperatures. The mean mass diameters, used as the monodisperse dry aerosol sizes, are indicated by legends. The wet aerosol sizes at the freezing threshold 235.8K/216.0K/196.4K are magnified by a factor of 7.2/2.4/2.1.

182.5KSynoptic conditionrange in

the tropical tropopause

layer

a. Detailed

b1. Simplified—with time-step of 20 minutes

}c. Gettelman et al.

22

13

9

Dehydration behaviors of different schemes for a single trajectory

Total water (ppmv)

1.9

13

b2. Simplified—with time-step of 6 hours as c

time obs. a b1 b2 c inst.

-50hr 9 13 13 22 1.93

0hr ~3 2.72 3.85 2.63 3.85 1.84

The presence frequencies of optically thin clouds during the (a) 6–8 Dec 2000 and (b) 6–8 Jun 2001 time periods comparing with MODIS satellite results retrieved by Dessler and Yang (2003).

winter

summer

380K

370K

360K

Means

2.1ppmv

5.4ppmv

2.5ppmv

Averaged total water distributions (of 12 sets of domain-filling runs) on three potential temperature levels. Winter case (6–8 Dec 2000).

360K to 370K

370K to 380K

Means

0.4ppmv

3.3ppmv

Dehydration.

Winter case (6–8 Dec 2000).

Winter case

6—8 Dec 2000

Summer case

6—8 Jun 2001

Mean value Dehydration Level Dehydration Mean value

2.1ppmv 380K 2.8ppmv

0.6ppmv0.4ppmv2.5ppmv 370K 3.3ppmv

3.3ppmv 3.6ppmv

5.4ppmv 360K 6.4ppmv

380K

370K

360K

Means

2.8ppmv

6.4ppmv

3.3ppmv

Averaged total water distributions (of 12 sets of domain-filling runs) on three potential temperature levels. Summer case (6–8 Jun 2001 ).

0.6ppmv370K to 380K

Means

3.6ppmv360K to 370K

Dehydration.

Summer case (6–8 Jun 2001 ).

Winter case

6—8 Dec 2000

Summer case

6—8 Jun 2001

Mean value Dehydration Level Dehydration Mean value

2.1ppmv 380K 2.8ppmv

0.6ppmv0.4ppmv2.5ppmv 370K 3.3ppmv

3.3ppmv 3.6ppmv

5.4ppmv 360K 6.4ppmv

Summary

A Lagrangian, partial-column, microphysical model has been established which can capture some features of APE-THESEO observations, such as the number and size of ice crystals;

A parameterisation, deduced from the detailed model, maintains more of the essential cloud physics than current parameterisations, without significantly increasing calculation-time, showing similar dehydration behaviour to the detailed model.

Ensemble runs of space-filling trajectory sets are carried out. The results, bearing similar patterns of cloud-presence frequencies to MODIS satellite observations, show different dehydration behaviors in winter and summer cases.

Ensemble runs to estimate the annual cycle like ‘tape recorder’ and the stratospheric water content trend are going to be carried out in the next step.

Acknowledgements

• Funded by NERC CWVC, EC TroCCiNOx• THANKS TO:P. Haynes, and V. M. Bonazzola, Cambridge UniversityJ. Methven, University of ReadingA. E. Dessler, and P. Yang (2003), J. Climate, 16, 1241-7.A. Thomas, S. Borrmann, et al. (2002), J. Geophys. Res., 107,

10.29/2001JD001385T. Koop, and B. Luo, Swiss Federal Institute of Technology

This presentation is soon available online at http://www.es.lancs.ac.uk/cnhgroup/ChuansenR.html