# Presentation: 417832

## Validation of TES tropospheric Ozone Profiles Using Airborne Observations

- On average TES exhibits a small positive bias in the middle and lower troposphere of less than 15% and a larger negative bias of up to 30% in the upper troposphere.
- Some of the differences could be due to the temporal mismatch of the measurements.
- The comparison of in-situ profiles taken during aircraft spirals is problematic due to the high degree of variability in tropospheric Ozone and the large distances covered by the aircraft whilst obtaining the measurements.
- The next version of TES data will improve the comparisons in the upper troposphere.

**Summary**

**TES Observations during The MILAGRO/INTEX-B Campaign**

- During MILAGRO/INTEX-B TES made 243 Step & Stare special observations.
- 7 DC-8 flights were coincident or near-coincident with TES nadir observations providing ~212 DIAL profiles for validation.

**Validation of TES tropospheric Ozone Profiles Using Airborne Observations**

- Nigel Richards, Qinbin Li, Ed Browell1, Melody Avery1 Greg Osterman, Kevin Bowman
-  and the TES team

- Jet Propulsion Laboratory, California Institute of Technology
- 1NASA Langley Research Center

**Comparing Ozone profiles with TES**

- In order to compare profiles obtained from a remote sensing instrument such as TES with model or *in-situ* data, we must first apply the averaging kernels.
- Averaging kernels intrinsically account for both, and may be used to transform model/*in-situ* profiles into “TES space” so that they may be directly compared

- All DIAL observations within 0.15 degrees lat/lon of each TES observation were selected and averaged for comparison with the corresponding TES profile.
- DIAL profiles were interpolated to the TES pressure grid.
- In order to apply TES averaging kernels to the DIAL profiles missing data in the DIAL profile were replaced with TES *a priori* information, each profile was also extended to the highest TES pressure level using the *a priori*.

*a priori profile*

- DIAL profile

- Averaging kernel

**Introduction**

- In addition the aircraft made several coincident spirals during which the FASTOZ in-situ instrument was able to obtain Ozone profile information
- TES Ozone profiles were compared to those obtained by the DIAL and the FASTOZ instruments during the coincident flights.

- Validation of remotely sensed constituent profiles is essential before they may be used for scientific studies. Validation seeks to identify and characterize any systematic biases that may be present in the reported mixing ratio profile. Validation is conducted through comparisons with independent measurements of the same parameters. The Tropospheric Emission Spectrometer (TES) is an infrared instrument which was launched onboard NASA’s Aura satellite in 2004. TES is the first instrument to provide vertical information on tropospheric Ozone whilst simultaneously measuring CO on a global basis. During INTEX-B the NASA DC-8 aircraft conducted several flights which allowed the DIfferential Absorption LIDAR (DIAL) instrument to obtain Ozone profile measurements which were spatially coincident with TES special observations in three different geographical regions. Here we will present comparisons of TES and DIAL tropospheric Ozone profiles for all coincident flights during INTEX-B.

- TES averaging kernel

- TES exhibits a mean positive bias of less then 15% in the lower and mid-troposphere relative to DIAL.
- Bias is negative in the upper troposphere and increases to up to 30%.
- Larger differences observed on individual flights, this could be due to temporal differences in collocation of observations.
- The aircraft can take around 3 hours to complete the TES validation run, however TES covers the same distance in just a few minutes leading to a temporal mismatch in the observations.
- The panels above show the tracks for the three TES validation flights, the small black lines represent 3 hour forward trajectories started at the locations of the TES observations at three different altitudes. The background shows GEOS-Chem model Ozone at each altitude.
- Depending on the altitude and the homogeneity of the Ozone field, the aircraft and TES can be measuring very different air masses, this could explain some of the observed differences between TES and DIAL.
- Due to the high degree of spatial variability exhibited by tropospheric Ozone, it is very difficult to use the FASTOZ in-situ aircraft observations to validate satellite retrievals.
- The in-situ observations are however useful for validating background Ozone concentrations in regions where little variability is observed

**Results**

**Acknowledgements**

- This work was performed at Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

- DIAL images courtesy of Ed Browell (LARC).
- GEOS-CHEM data provided by Harvard.

- Data gaps filled with TES *a priori*

- FASTOZ problems

**DIAL**

**FASTOZ**

- March 12th (Houston)

- March 9th (Houston)

**Houston**

**Hawaii**

**Anchorage**

**3459 (March 16****th****)**

**Version 2**

**Version 3**

**Future TES data versions**

-  The next version of TES data (Version 3) will include updates which will improve TES upper tropospheric temperature and Ozone retrievals
- The above example demonstrates this, where the large negative bias in the upper troposphere is significantly reduced.

- 5 km

- 1 km

- 8 km

**March 4****th**** 2006 Run 3399**

- March 4th

- March 12th

- March 16th

- April 23rd

- April 25th

- May 7th

- May 9th