Hansford Ucam Ozone

In Situ Measurements of Ozone during Hibiscus 2004: 

In Situ Measurements of Ozone during Hibiscus 2004 Contributions through provision of data and discussions: Niels Larsen (DMI ozonesondes) Gerhard Held, José Mauricio Leite, Bruno Biazon, Pierre Dedieu (preparation and processing of IPMet RS80 & O3 sondes) Georges Durry, Nadir Amarouche (mSDLA) Tom Gardiner, Nigel Swann (TDLAS) Alain Hauchcorne (MIMOSA) G. M. Hansford, R. A. Freshwater, R. L. Jones

Outline: 

Outline Assessment of 13 Ozonesondes (DMI/IPMet) launched during Hibiscus TTL characteristics: temperature, lapse rate, saturated water vapour mixing ratio profiles and their relation to ozone Definition of the TTL appropriate to Bauru Individual flights: anomalies, relation to PV Assessment of UCAM solid-state ozone sensor measurements on SF flights Correlations with other tracers: CH4, H2O, CO2 Comparison with Theseo 2000 correlations

All Ozonesondes launched during Hibiscus: 

All Ozonesondes launched during Hibiscus Flat mixing ratio in the troposphere 11th Feb and 6th Mar are anomalous in the altitude range 12 – 16 km

Slide4: 

MIMOSA PV Maps at 350K: Selected Dates 350K corresponds to ~13.6 km, 165 hPa 11th Feb and 6th Mar show high PV at this level other dates show normal PV characteristic of the tropics

Slide5: 

Ozonesondes: Averages and Ambient Temperature Ozonopause in the average profile occurs at 13.66 km Except for the boundary layer, the TTL shows greatest variability Standard deviation is only ~5% above 20 km Broad temperature minimum in individual and average profiles Cold-point tropopause at 17.56 km (-75.9ºC) in the average profile Variability also greatest in the TTL, though less pronounced than ozone

Slide6: 

Ozonesondes: Lapse Rate and Saturated Water Vapour MR Clear TTL signature 13.4 – 17.8 km Local minimum in the average lapse rate at 13.42 km Lapse rate profiles very noisy Very flat SWVMR between 15.0 – 17.8 km Minimum in the average profile is 12.2 ppmv Individual minima are more important? Dataset minimum is 6.0 ppmv on the 20th Feb

Slide7: 

TTL Statistics from Ozonesonde Series Definitions of the TTL Highwood and Hoskins (1998): extending from the main convective outflow to the cold point. Sherwood and Dessler (2001): the region where convection overshoots its level of neutral buoyancy. Vömel et al. (2002): TTL lower boundary can be defined by a local minimum in relative humidity. Thuburn and Craig (2002): region where radiation is more important than convection, but convection is more important than chemical ozone production. Gettelman and Forster (2002): lower boundary marked by the lapse rate minimum, upper boundary by the cold point.

Slide8: 

Individual Profile: 16th February 2004 TTL extends from 14.2 – 19.2 km (lapse rate minimum to secondary temperature minimum) Cold-point at 16.4 km Although a clear lapse rate minimum is apparent in this dataset, many show multiple local minima in the range 10 – 15 km Conclusion The Gettelman and Forster criteria for the TTL boundaries are not appropriate for this region of the tropics. TTL definition appropriate for Bauru? – Lower boundary: change in gradient in ozone mixing ratio. Upper boundary: decrease in ozone variability.  14.0 – 17.9 km This definition reflects the potentially greater role of horizontal transport/mixing at TTL altitudes relative to sites closer to the equator.

Slide9: 

SF4 24th Feb 2004: O3 (O3-SSS), CH4, CO2 (mSDLA) Ascent Profiles No clear correlations between any of these tracers

Slide10: 

SF4 24th Feb 2004: O3 (O3-SSS), H2O (mSDLA) Descent Profiles Anti-correlation between ozone and water vapour 16.5 – 19 km Major features occur at similar altitudes

Slide11: 

SF2 13th Feb 2004: O3 (O3-SSS), CH4 (mSDLA) Ascent Profiles No significant correlations over any extended altitude range

Slide12: 

SF2 13th Feb 2004: O3 (O3-SSS), H2O (mSDLA) Descent Profiles No significant correlations over any extended altitude range (large feature at 6 km correlated?)

Slide13: 

SF3 26th Feb 2004: O3 (O3-SSS), H2O (TDLAS) Anti-correlation during descent between 10.5 and 13.5 km No other significant correlations

Slide14: 

THESEO-2000: O3 (O3-SSS), CH4 (TDLAS) Much more obvious (anti-)correlations seen between ozone and methane above Kiruna But, these profiles represent mostly stratospheric air

Slide15: 

Summary of Tracer Correlations on SF Flights These results need to be interpreted in terms of origin of air – are any (anti-)correlations expected?

Slide16: 

Future Work Ozonesondes Calculate photochemical ozone production rates in the lower TTL, and check for a positive correlation between ozone and lapse rate above ~14 km (Folkins et al, 1999) Check ancillary data for 11th Feb and 6th Mar to understand elevated ozone in the 12 - 16 km range on these dates SF flights Interpretation of (lack of) correlations between ozone and other tracers Comparison with back-trajectories