# Presentation: 437405

## Assimilation of OMI and MLS ozone data 

**Assimilation of OMI and MLS ozone data**

**I. Stajner, K. Wargan, L.-P. Chang, **
**H. Hayashi, and S. Pawson,**
- Global Modeling and Assimilation Office (GMAO), NASA/Goddard
**L. Froidevaux, and N. Livesey**
- Jet Propulsion Laboratory
- Aura Science Team Meeting                         Pasadena, March 2005

## Ozone assimilation at GMAO

**Total ozone** columns and **stratospheric profiles** from **SBUV/2** instrument are assimilated in near-real time into a parameterized chemistry and transport model (**CTM**) driven by GMAO assimilated winds.
- Assimilation provides a sensitive tool for **monitoring** of the quality of ozone data:
- Time series of observed-minus-forecast (**O-F**) **residuals**.
**Comparisons** of assimilated ozone with **independent** data
- (*Stajner et al, JGR 2004, *doi:10.1029/2003JD004118).

## Assimilation of limb viewing data

**Assimilation of limb viewing data**

- Representation of **lower stratospheric ozone** improved by assimilation of:
**POAM III** over Antarctica (*Stajner and Wargan GRL 2004, *doi:10.1029/2004GL020846)
**MIPAS** globally (*Wargan et al. submitted to QJRMS*)
- These limb and occultation instruments provide high quality data in regions where SBUV/2 data are of lower quality or missing.
- Aura **OMI** and **MLS** ozone data were assimilated.

## OMI total column O-F residuals

**OMI total column O-F residuals**

**OMI** residuals are
- typically 1DU **smaller**
- than SBUV residuals.

- Global RMS (DU)

**OMI** data:
-    January 1-27
**MLS** data:
-    January 2, 3, 9-13,
- 17, 19, 20, 23

- This is a measure of the **disagreement **between incoming **OMI** data and short-term model forecasts.

**OMI+MLS(46-0.15 hPa)**
**OMI+MLS(100-0.15 hPa)**
**MLS data**
**OMI zoom mode data**
**SBUV assimilation**

## OMI total column O-F residuals

**OMI total column O-F residuals**

**OMI** data from **zoom **
**mode increase** O-F
- residuals.

**OMI** residuals are
- typically 1DU smaller
- than SBUV residuals.

- Global RMS (DU)

**Zoom**

**OMI+MLS(46-0.15 hPa)**
**OMI+MLS(100-0.15 hPa)**
**MLS data**
**OMI zoom mode data**
**SBUV assimilation**

## OMI total column O-F residuals

**OMI total column O-F residuals**

- Assimilation of **MLS** data **decreases** **OMI** O-F residuals

**OMI** data from zoom
- mode increase O-F
- residuals.

**OMI** residuals are
- typically 1DU smaller
- than SBUV residuals.

- Global RMS (DU)

**MLS**

**MLS**

**MLS**

**MLS**

**Zoom**

**OMI+MLS(46-0.15 hPa)**
**OMI+MLS(100-0.15 hPa)**
**MLS data**
**OMI zoom mode data**
**SBUV assimilation**

## OMI total column O-F residuals

**OMI total column O-F residuals**

- Assimilation of **MLS** data decreases **OMI** O-F residuals
- Absence of **MLS** data **increases** **OMI** O-F residuals
**OMI** and **MLS** seem **consistent**.
- Use of **MLS** data in lower stratosphere **decreases** **OMI** O-Fs further.

**OMI** data from zoom
- mode increase O-F
- residuals.

**OMI** residuals are
- typically 1DU smaller
- than SBUV residuals.

- Global RMS (DU)

**MLS**

**MLS**

**MLS**

**MLS**

**Zoom**

**OMI+MLS(46-0.15 hPa)**
**OMI+MLS(100-0.15 hPa)**
**MLS data**
**OMI zoom mode data**
**SBUV assimilation**

## Comparison with SAGE III

- Assimilation of **Aura MLS** and **OMI** data reproduces the mean **profile shape** in the **lower stratosphere** and its **variability** with latitude better than the assimilation of SBUV/2 data.

- Mean profiles from:
**_ SAGE III**
**_ Aura assimilation**
**_ SBUV/2 assimilation**

- Sunrise
- near 37°S

- Sunset
- near 67°N

- MLS data are available
- for January 9-13.
- The comparisons are at
- SAGE III measurement
- locations on
- January 11-13.

**3**

## Low ozone air

**Low ozone air**

-     4    5    6    7    8    9  10  11 12  13  14  15 mPa

- MLS+OMI assimilation
**at 100 hPa on January 9, 2005**

**January 11, 2005**

**January 12, 2005**

**January 13, 2005**

**SAGE III ****Aura assim.**

- Intrusion of low ozone air at 100 hPa from the Tropics is advected eastward and wrapped around higher ozone over Canada.
- Circles mark locations where SAGE III ozone was less than 10 mPa on the previous day at sunset.

- This SAGE III profile and the collocated Aura assimilated profile agree well.

- 180W

- 0

## Comparisons with sondes

**52N 5E**

**52N 20E**

**46N 7E**

**64S 56W**

- Jan. 11

- Jan. 20

- Jan. 12

- Jan. 19

- Jan. 12

- Jan. 22

- Jan. 9

- Jan. 19

**__   Sondes**
**__   MLS+OMI**
**__   MLS+SBUV **
**                 ****total column**

- Either assimilation with **MLS** data captures well different profile shapes and **variability in the middle and lower stratosphere**.
- Assimilation of **OMI** data produces excessively low ozone in the troposphere.  This may be due to the way we are using OMI data, or to data themselves.

**52N 5E**

**52N 20E**

**46N 7E**

**64S 56W**

- Pressure (hPa)

- 100

- 100

- 10

- 10

- Ozone (mPa)

## Tropical tropospheric ozone

- Both assimilations reproduce climatology at SHADOZ stations.  **MLS+OMI** seems better at Natal (324°E) and Ascension (345°E).
**Wave one** in tropospheric ozone is captured, with higher ozone values over the Atlantic than over the Pacific ocean.
- Tropospheric columns from Aura assimilation agree within ~5 DU with sondes at Nairobi (36°E) and Samoa (189°E).

- January mean
- for SHADOZ** **
**sondes**
- (1998-2000)
**MLS+OMI**
**MLS+SBUV**

- 324°E    345°E    36°E     112°E    189°E    270°E

- Atlantic

- Pacific

## Conclusions

- Aura **OMI** and **MLS** ozone data were **assimilated**.
- Preliminary evaluation shows:
- OMI total ozone column O-F residuals decrease when MLS data are available: indicates that data are **consistent**.
- Aura assimilation **agrees** better **with independent**     SAGE III and ozone sonde **profiles** than the SBUV/2 assimilation, as expected.
- Spatio-temporal variability in the **lower stratospheric** ozone seems well represented in the Aura assimilation.
- Wave one in tropical **tropospheric** ozone is represented.  Elsewhere, tropospheric ozone becomes too low – reasons will be investigated.
- Further evaluations and applications will follow.

## Backup slide

## Low-reflectivity OMI 

**OMI **data with low reflectivity (<15%) provide reduced coverage (especially at high latitudes), but improved assimilated tropospheric ozone in the extra-tropics.  Longer runs are needed.

- OMI coverage on Jan. 10

- Low reflectivity on Jan. 10

- Low reflectivity on Jan. 1-24

**sonde**
**All OMI**
**Low reflectivity**

**O-F residuals**