# Presentation: 939133

## TES-AIRS T Comparisons:

- Eldering and the TES team
- September 2005

## Outline

- Dataset & analysis
- TES-AIRS temperature comparisons
- TES-MLS temperature comparisons
- Expected changes in future version of TES data
- Conclusions

## The data sets

- TES
- Global surveys
- Step and stares
- Removed data with radiance residual RMS larger than 1.4 or radiance residual mean greater than 0.1

- AIRS data
- Closest match to TES, but note that retrievals are on 45km diameter footprint
- Used only QA_TEMP_BOT =0
- Using v4.0
- MLS data
- V1.51
- Did not apply QA screening to MLS data

## The analysis

- Scatterplots of temperature for each layer
- Histograms and statistics of the differences
- Plots of bias and rms as a function of pressure

## AIRS & TES Comparisons

- Comparisons:
- Integrated TES water vapor profiles to make a layer water quantity like AIRS 28 layer product
- Caveats:
- Footprint:
- AIRS retrievals are on a group of 9 AIRS footprints which are captured in an AMSU footprint - 45km diameter circle
- TES retrieval is on 5km by 8km footprint

- Retrievals:
- AIRS applies cloud-clearing and then a complex cascade of retrieval steps, including tuning
- Different initial guesses, AIRS applies trapezoids to set the retrieval grid
- AIRS incorporates microwave sounder measurements in retrieval
- Bottom line: I don’t try to account for these differences, just note that they will impact comparisons

## AIRS v4 vs sondes

- Validation of AIRS version 4 retrievals using ARM TWP RH90 data scaled by MWR.
- Left upper panel: 1 km layer temperature differences (AIRS-ARM);
- Left lower panel: percent difference in 2 km layer water vapor amounts (100(AIRS-ARM)/ARM);
-  Right panels: yields using different quality constraints.

## SGP

- Near surface temperature bias different
- Upper troposphere biases similar at both sites
- Analysis courtesy of Dave Tobin

## A summary of statistics (GS)

- Mean profiles
- TES - AIRS

- Bias in green [TES-AIRS], rms differences in black

## Summary stats for step and stares

- Similar statistics for special observations

## Latitudinal dependence?

- 20S-20N
- 555

- 20-40
- 560

- 40-60
- 400

- Overall characteristics of bias show little latitudinal dependence - Some reduction of upper trop bias at higher latitudes

## Layer by layer analysis

- At all layers, RMS near 2K, unskewed differences
- Mean difference are:  -1.8K, -0.4K, and -0.4K at 1000, 925, and 800 mb.
- Standard deviation is 2.7 to 1.6K at all these levels.
- Differences normally distributed.

- TES

- AIRS

- TES-AIRS

## middle layers

- 700, 600, and 500mb layers, mean differences of -0.6K,   -0.7K, and -0.6K
- Standard deviation near 1.5K for these layers
- Differences normally distributed

## highest altitudes

- Bias changes sign and becomes larger.
- 0.5K at 400mb
- 2.0K at 300mb
- 1.7K at 250mb
- Differences still nearly normally distributed.
- Consistent with analysis of aircraft campaigns

## TES and MLS

- MLS data unscreened
- Not yet put on common basis with averaging kernals
- TES 2.1K warmer than MLS at 316mb
- TES 2.6K warmer at 215mb
- TES 2.4K warmer at 146mb
- RMS of 4.8 to 3.3K
- Consistent with other comparisons.

- TES

- MLS

## TES future versions

- T_atm at 215 mb
- Current L1B
- Prototype L1B

## 2147 with old & new radiance calibration and AIRS

- With new calibration, TES becomes colder, less biased near tropopause. Water vapor changes little.

## Conclusions

- TES temperatures are less than 1K colder than AIRS below 400mb.
- TES is about 2K warmer than AIR above 400mb.
- RMS of less than 2K at all levels
- Similar mean differences with MLS

- Future L1B calibration will make TES temperature profiles less bias relative to AIRS in the upper troposphere.
- Next up: operational sonde comparison

## Backup slides

## 2147 versus AIRS v3(L) and v4 (R)

- Since AIRS gets drier in upper trop in V4, bias becomes larger.

## TES Averaging kernals - water

- TES loses sensitivity above 200mb, impacted by clouds

- OD = 0.05

- OD = 0.7

- OD = 3.1

## TES Averaging kernals - temperature

- Sensitivity throughout the atmosphere