# Presentation: 237181

## Tropospheric ozone from assimilation of Aura data using different definitions of the tropopause  

**Tropospheric ozone from assimilation of Aura data using different ****definitions of the tropopause**

- I. Stajner, K. Wargan, L.-P. Chang,
- H. Hayashi, S. Pawson,
- L. Froidevaux, N. Livesey,
- P. K. Bhartia
- NASA Goddard and JPL

- Aura Science Team Meeting                       Boulder, Colorado, September 15, 2006

## Tropospheric ozone

- One of the goals of the assimilation of Aura data is to produce maps of tropospheric ozone
- Different definitions of tropopause:
- temperature lapse rate (WMO)
- dynamical
- chemical
**What is the sensitivity of the tropospheric ozone columns to different definitions of the tropopause?**

## SHADOZ example

**SHADOZ example**

**WMO**

**Ozone**

- 17.1 km

- 14.3 km

## Background

*Bethan et al 1996*: ozone defined tropopause lower than WMO tropopause by about 1 km.  When WMO tropopause indefinite, 27% of the ozone below WMO tropopause lies above ozone tropopause.  Sondes from four European stations 51°N-79°N.

## Assimilation of Aura ozone data within a GCM

**Assimilation of Aura ozone data within a GCM**

**Data:**
**MLS** stratospheric ozone profiles (for pressure   <= 216 hPa, some temporal gaps)
- US retrieved  **OMI** total ozone data  (for reflectivity < 15%)
- Time period: **January-December 2005**.
- The assimilation system model includes:
- transport within GEOS-4 **general circulation model** constrained by meteorological analyses
- parameterizations for stratospheric photochemistry and heterogeneous ozone loss
- a parameterization of the tropospheric chemistry (for year 1998).

## Sample validation

- 20050218

**Assimilated ozone** captures larger scale variability seen in **MOZAIC data** without obvious systematic offsets

- Mean differences between **assimilation** and **sondes** at Hohenpeissenberg for year 2005 are smaller than 10% between 10 and 500 hPa

- Charlotte-Munchen

**Sample validation**

## Slide 7

| Tropopause definition | Criterion | Pressure search range |
| --- | --- | --- |
| WMO (algorithm by Reichler et al 2003) | Lapse rate < 2K/km and does not exceed 2K/km for 2 km above | 550 to 
75 hPa |
| Dynamical | Lower of: |PV|=3.5 PVU or  = 380 K | > 51 hPa |
| Ozone from below | Ozone = 0.1 ppmv | < 500 hPa |
| Ozone from above | Ozone= 0.1 ppmv
 | > 51 hPa |

## Zonal mean altitude of tropopause

**WMO**
**Dynamical**
**Ozone from below**
**Ozone from above**

- Ozone tropopause
- lower than WMO
- by 0.7 to 1 km in
- northern
- midlatitudes

**Zonal mean altitude of tropopause**

## Zonal mean tropospheric ozone column

**WMO**
**Dynamical**
**Ozone from below**
**Ozone from above**

- Tropospheric
- column using
- ozone tropopause
- lower than that
- using WMO
- Tropopause by
- ~2-3DU (10%)
- in northern
- midlatitudes

**Zonal mean tropospheric ozone column**

## Percentage of ozone column below WMO tropopause

- %

- that lies above ozone tropopause at 00Z15FEB2005

## Wind magnitude at 200 hPa at 1:30Z15FEB2005

## Assimilation of OMI and MLS ozone provides a global dataset for studies of ozone in the UTLS. 
Assimilated ozone agrees well with independent MOZAIC and Hohenpeissenberg data.
The choice of the tropopause definition has a large impact on the tropospheric ozone column.
The amount of ozone below WMO tropopause that is above ozone tropopause is:
About 10% on average in the northern middle latitudes in the example for February 15, 2005
Can exceed 80% depending on dynamical features.
Comparisons with dynamical tropopause and applications to study of the stratosphere-troposphere exchange are planned.

- Assimilated ozone **agrees well** with independent **MOZAIC **and **Hohenpeissenberg** data.
- The choice of the **tropopause definition **has a** large impact** on the tropospheric ozone column.
- The amount of **ozone below WMO tropopause** that is **above ozone tropopause** is:
- About **10% on average** in the northern middle latitudes in the example for February 15, 2005
- Can **exceed 80%** depending on dynamical features.
- Comparisons with dynamical tropopause and applications to study of the stratosphere-troposphere exchange are planned.

**Conclusions**

## Backup slides

## Slide 14

## Background cont.

**Background cont.**

*Pan et al 2004*: In extratropics, a transition layer centered around WMO tropopause 2-3 km thick, and thicker near subtropical jet. Aircraft data from STRAT and POLARIS campaigns.

**Stratosphere**

**Transition**

**Troposphere**

- CO

- O3

## SHADOZ example 2

**SHADOZ example 2**

**WMO**

**Ozone**

- 17.2 km

- 15.6 km

## Assimilation vs MOZAIC

**Assimilation**** vs ****MOZAIC**

- 20050218

- 20050226

- 20050310

- Miami-Munchen

- Charlotte-Munchen

- 20050124

- 20050127

- 20050201

- Assimilated ozone captures larger scale
- variability seen in MOZAIC data without
- obvious systematic offsets

## Mean differences 

- Mean differences
- between assimilation
- and sondes at
- Hohenpeissenberg
- for year 2005 are
- smaller than 10%
- between 10 and 500 hPa