# Presentation: 710388

## Seasonal and Spatial Distribution of Lower Stratospheric Lamina as Observed by HIRDLS and Modeled by the Global Modeling InitiativeMark A. Olsen1, Jose M. Rodriguez2, Yasuko Yoshida1, Anne R. Douglass2, John C. Gille3, Valery A. Yudin3, Bruno Nardi3, and Doug Kinnison31GEST/NASA GSFC      2NASA GSFC      3NCARCorrespondence:  Mark.Olsen@nasa.gov

**Introduction**
- Synoptic, global observations of laminar isentropic transport in the upper-troposphere/lower-stratosphere (UTLS) from the tropics to higher latitudes have been difficult due to the high vertical resolution needed to resolve the events.  *Olsen et al.* [2008, GRL, in press] have shown that HIRDLS is capable of observing these events with 1 km vertical resolution and that a Global Modeling Initiative (GMI) simulation agrees well with the observations.  A systematic algorithm to detect ozone lamina in along-track HIRDLS observations of the UTLS is presented here.  The algorithm is applied to the observations and a GMI simulation for year 2006 in the NH.  The global seasonal and spatial characteristics of these intrusions are examined.  In addition, comparisons of the observational and simulated results bring out the successes and limitations of the model in representing this isentropic transport between the tropics and extratropics.

**Summary and Conclusions**
-   The lamina identification algorithm is capable of discerning isentropic lamina in both observations and simulations.
-   The observations show a strong seasonal dependence of lamina frequency, thickness, and potential temperature altitude between 340 K - 480 K.
-   Observed lamina exhibit a longitudinal preference in winter and spring.
-   Simulation agrees well with observations in winter/spring, but large discrepancies in summer/fall.
-   Continuing work:  Investigate relationship to meteorology and dynamics; compare with evaluation of nitric acid lamina; evaluate and compare lamina in Goddard Chemistry Climate Model simulations.

**Data and Model**
- _HIRDLS:_
-   v004; only ascending orbits in NH
-   All recommended filters (from Data Guide)
-   Vertical profiles; ~ 1 km vertical resolution
-   ~65 km along-track resolution
-   ~ 14 orbits/day

- Sample Along-Track Curtains

- Average Number of Lamina in 2° Mean Profiles Per Day

- _Global Modeling Initiative (GMI) Combo:_
-   Stratospheric and tropospheric chemistry
-   GEOS-4 DAS (time-averaged)
-   ~ 1 km vertical resolution in the UTLS
-   2° x 2.5° horizontal resolution

- Mean Layer Thickness

**Algorithm**
-   For each profile between 34° - 70° N, interpolate HIRDLS ozone above 260 hPa altitude to potential temperatures from 340 K to 480 K in 5 K increments.
-   Determine average profiles for all profiles within 2° latitude bands along each orbit.
-   **Lamina bottom:** potential temperature where ozone begins to decrease with height.
-   **Lamina top: **potential temperature where ozone ≥ ozone at lamina bottom.
-   Additional criteria:
-   Difference of the ozone at lamina bottom and the minimum ozone in layer must be greater than the sum of the precisions at the bottom and minimum.
-   The potential temperature difference between the layer top and bottom (thickness) ≤ 60 K.  (~2-2.5 km)
-   Feature must be coherent across three adjacent mean profiles (6° latitude).
-   Lamina similarly identified in GMI simulation.
-  Simulated ozone interpolated to HIRDLS measurement locations.
-  HIRDLS precision field used with simulated ozone.

- Potential Temperature

- Ozone Mixing Ratio

- Layer top, t

- Layer bottom, b

**Mean along-track profile in 2° latitude band**

- Xb_x0008_±∂Xb

- Xm_x0008_±∂Xm

- t - b ≤ 60 K

- Xb - Xm ≥ ∂Xb + ∂Xm

-   Similar features identified in both observations and simulation.
-   Identification even where features differ in magnitude and overall shape.
-   High latitude cases are found.  Origin?

- HIRDLS
- GMI

-   In general, observations show more profiles with lamina.
-   Strong seasonal cycle in both, peaking in March-April.

-   Seasonal cycle in phase with frequency.
-   GMI more variable in latter half of year.

- Mean Layer Magnitude    (O3max -O3min) / O3max * 100%

-   No significant seasonal dependence.
-   Less agreement between observations and simulation in fall.

- Mean Potential Temperature of Layer

-   Strong seasonal cycle in observations; not reproduced in simulation with large differences in summer and fall.

- Spatial Distribution

- HIRDLS
- GMI

- HIRDLS
- GMI

- HIRDLS
- GMI

- HIRDLS
- GMI

**Jan**

**Apr**

**Jun**

**Sep**

-   Strong spatial dependence in winter/spring not evident in summer/fall.
-   Simulation not in good agreement with observations in summer and fall.