# Presentation: 177773

## Aura Science Team Meeting 2008MLS Status

- Aura Science Team Meeting 2008MLS Status

- Nathaniel Livesey on behalf of the MLS teams at
**Jet Propulsion Laboratory**
**California Institute of Technology**
- and at
**University of Edinburgh**
- Copyright 2008,All rights reserved

## MLS science goals

- Track the stability of the stratospheric ozone layer

- MLS observations of the 2006 Antarctic ‘ozone hole’ development in the lower stratosphere

## MLS Level 2 products

- All MLS data are publicly available from the GSFC DISC

- Thick/thin lines are current (v2.2) range. Thin lines denote where averaging (e.g., zonal means) is required for useful signal to noise. Dotted lines are goals for later versions

## MLS instrument status

- MLS continues to operate very well
- The majority of the instrument subsystems are performing flawlessly
- However, some are exhibiting premature aging and/or anomalies
- To date, the science impact of these has been slight
- Recent / ongoing anomalies
**Band 32, channels 2&3 **(UT/LS temperature) – brief signal decline, Sep. 2008
- Returned to normal after ~1 week
- These channels are effectively redundant three times over
**Band 17 **(pointing for 2.5 THz OH data) – oscillator lost lock, May 2008
- Impact on OH product is <5% at peak
- A single event upset (cosmic ray hit) is suspected, a reset might clear the problem, but involves reset of all THz bands
**Band 13 **(HCl) – Premature aging, powered off to conserve life, Feb. 2006
- HCl information also obtained from band 14 which overlaps the same line

## MLS data processing status

- All MLS data have been reprocessed with the latest (version 2.2) algorithms
- These were described in the MLS validation papers
- V2.2 reprocessing was completed in May, earlier than originally planned thanks to efficiency improvements in the software
- Versions 2.21, 2.22 and 2.23 produce nominally identical results
- A near-real-time (NRT) MLS dataset for stratospheric and mesospheric O3 and Temperature is now operational
- NRT data typically available within 3 hours of observation
- An addendum to the v2.2 quality document describes these data
- Improvements to NRT UT/LS O3 and US/LM temperature are planned
- ‘Version 3’ algorithms for MLS are under development
- Main goals are to improve biases, especially in UT/LS
- Plan to double the vertical resolution of UT/LS O3 profile representation
- 12 surfaces per decade (~1.5 km)
- True resolution of information will be closer to ~2 km

## MLS HCl status and trends

- V2.2 retrieves HCl from band 14, as the band 13 dataset stopped in May 2006
- A ‘band 13 HCl’ product is retrieved for days when band 13 data are available
- The two HCl products agree very well in the middle and lower stratosphere

- However, observed trends in the upper stratosphere / lower mesosphere differ
- Offset between the two datasets is within expected accuracy
- Trends in the raw MLS radiance observations show the same discrepancy
- See poster by Lucien Froidevaux et al., for more discussion

- 460 K, 18 November 2004

## Reducing biases in the upper troposphere

- Upper tropospheric biases (mainly at 215 hPa) are a recognized problem in v2.2
- Factor of ~2 high bias in CO at 215 hPa
- Negative bias in HNO3 at 215 hPa in the tropics
- We have investigated several possible causes
- Instrument issues (e.g., channel positions, gain compression nonlinearities)
- Spectroscopy issues (e.g., ozone line mixing)
- While these investigations have led to small bias reductions, no ‘silver bullet’ has yet been found
- Comparing MLS radiances to forward-model computations using co-located WB-57 data as ‘truth’ reveals a ‘slope’ feature across some 240 GHz bands
- Removing this before the retrieval alleviates biases
- The origins of this slope are under investigation, in the meantime we are considering applying such a radiance correction in v3

- 215 hPa CO for 6 Feb 2008

## Halogen chemistry in the polar lower strat.

*[Santee et al., 2008, JGR]*

- Recent laboratory measurements *[Pope et al., 2007]* call into question our theoretical understanding of chlorine-catalyzed polar ozone destruction
- When new parameters are used, models (e.g., SLIMCAT shown here) severely underestimate measured ClO during the peak activation period

- ClO also remains significantly enhanced well after MLS shows deactivation, especially at the lower levels
- Dramatic delay in deactivation also seen in HCl
- Substantially less ozone loss
- See related talk by Michelle Santee, Wednesday 11:15am

- Antarctic vortex average profiles vs. time

## MLS gives insights into TTL processes

- MLS H2O and CO observations have led to improved understanding of processes in the Tropical Tropopause Layer (TTL)
- H2O observations confirm the role of the cold point tropopause in controlling stratospheric humidity
- However, overshooting convection (above the level of neutral buoyancy) is needed for models to match TTL CO variations observed by MLS

- See *Read et al., [2008, ACP in press] *for more discussion
- Including the use of ACE-FTS HDO to provide further constraints on cloud ice lofted by the overshooting convection
- Also, discussion of factors affecting trends in stratospheric humidity

- 147hPa CO variability

- MLS observations

- Extra-tropical CO

- Models without overshooting convection

- Models with overshooting convection

## MLS cloud observations at 2.5 THz

- The standard MLS cloud ice products are based on 240 GHz observations
- Other MLS frequencies (e.g., 190 GHz, 640 GHz) offer complementary information, and provide a measure of cloud particle size
- In particular, the 2.5 THz MLS radiance observations are sensitive to thin cirrus clouds that have less impact on the ‘standard’ 240 GHz products
- We generally see a broader spread in latitude for THz clouds compared to GHz
- E.g., December average shown right
- Consistent with our expectation that thin cirrus is more extensive than thicker deep convective cloud
- We will soon implement a revised MLS THz scan program to make more UT/LS views, giving better cloud information

- December 2005  – 2007 average

*[Wu et al., 2008, GRL]*

## Aura/Aqua and cloud climate feedbacks

- The impact of clouds on Earth’s radiative balance is one of the greatest uncertainties in climate models
- Cloud fraction and cloud ice data from AIRS and MLS show that upper tropospheric (~10 km altitude) clouds increase with increasing sea surface temperature (SST)

*[Su et al., 2008, JGR]*

- These clouds provide a net warming
- Thus leading to a positive climate feedback overall
- This work refutes the ‘Iris hypothesis’ [Lindzen et al.] that clouds have a negative feedback on climate

- Increased SST gives more UT clouds

- UT clouds produce net warming

- Solar radiative fluxes

- Longwave radiative fluxes

## A-train studies of aerosol indirect effect

- Aerosol indirect effects are one of the largest uncertainties in climate predictions
- Previous studies have been hampered by a lack of pollution aerosol measurements in the presence of cloud
- Using Aura MLS observed carbon monoxide as a pollution index, Jiang et al. found that polluted clouds are associated with smaller ice cloud particle size and weaker precipitation than clean clouds over South America during the dry season
- This represents a significant leap forward in our understanding of the aerosol indirect effects from observations
- The cloud particle size and precipitation measurements are based on observations from Aqua MODIS and TRMM, respectively
*[Jiang et al., 2008, GRL]*

## New products/diagnostics for senior review

**New THz cloud products**
- Take advantage of a newly implemented scan for the MLS THz telescope
- This makes more observations in the UT/LS, to get better cloud data
**Produce and augment ‘Level 3’ MLS products**
- Produce all MLS standard products in a simple ‘level 3’ format
- Maps, zonal means, daily / monthly granularity
- Equivalent latitude / potential temperature means for some products
**Enhanced ‘Derived Meteorological Products’ (DMPs)**
- Current DMPs describe a range of important met. parameters interpolated to the MLS observation locations (e.g., PV, wind, tropopause location etc.)
- Planned additions include static stability, additional tropopause / stratopause information, jet diagnostics (see Gloria Manney’s poster)
**New ‘Convective Influence Diagnostics’**
- Run reverse trajectories back from MLS observation track
- Note where these pass through strong convection (from GOES IR data)
- Based on similar work by Lenny Pfister for aircraft data

## Proposed MLS ‘joint’ products

**Combined CO profiles from TES and MLS**
- Retrieve CO from the lower troposphere to the mesosphere using TES and MLS radiance information simultaneously
- This is expected to provide better information than obtained by simply ‘bolting together’ the datasets
- Will enable unified studies of vertical transport of air from the lower to upper troposphere
**Surface pressure product **(talk by Evan Fishbein, Wednesday 8:00am)
- Combine MLS 100 hPa geopotential height product with temperature from Aqua AMSU to infer surface pressure, including in cloudy situations
- Valuable over oceans, particularly for studying hurricane genesis
- Accuracy is dependent on knowledge of Aura pointing / pointing stability
- We have a goal of 1 – 2 hPa accuracy (1 )
**Combined MLS / CloudSat / Calipso cloud information**
- We anticipate that (at least for now) this will be a research rather than a ‘new product’ activity

## Summary

- MLS continues to operate well
- Version 3 is under development
- Plan to reduce biases in upper tropospheric species
- Also reduce bias in lower stratospheric ClO, kink in strat. H2O, new products (e.g., CH3Cl)
- Aim to start production Spring ‘09
- Reprocessing done in 6–8 months
- Following that, plan to implement new algorithm for cloudy regions
- Additional products to be proposed for the senior review, including:
- Combined MLS/TES CO
- MLS/AMSU surface pressure
- Over 135 publications to date using MLS data, with 40+ in 2008
- Includes MLS (and other) validation papers

| Product(s) | MLS team member(s) |
| --- | --- |
| Temperature / GPH | Michael Schwartz |
| O3 | Lucien Froidevaux (strat./mes.)Nathaniel Livesey (upper trop.) |
| H2O / RHi | Alyn Lambert (strat. / mes.)Bill Read (upper trop.) |
| CO | Hugh Pumphrey (strat. / mes.)Nathaniel Livesey (upper trop.) |
| Cloud ice | Alyn Lambert / Dong Wu |
| HNO3, ClO,(CH3Cl, CH3CN) | Michelle Santee |
| HCl, HOCl | Lucien Froidevaux |
| N2O | Alyn Lambert |
| OH, HO2 | Herb Pickett |
| BrO | Nathaniel Livesey |
| SO2 | Bill Read |
| HCN | Hugh Pumphrey |

## Herb Pickett’s retirement

- In the New Year, Herb Pickett will be retiring after a 30-year career at JPL, preceded by productive periods at Berkley, Harvard and the University of Texas
- Herb’s contributions to science have been profound and diverse
- Microwave spectroscopy in both atmospheric and astrophysical applications
- Balloon-borne atmospheric observations

- Herb has contributed to countless aspects MLS
- Suggesting the UARS MLS ClO capability
- Devising the 2.5 THz Aura MLS OH system
- Closely supervising the MLS methanol laser local oscillator manufacturer to ensure reliable operation in orbit
- Overseeing critical modifications to the software driving the MLS mechanisms
- Thank you Herb for your many contributions, your innate wisdom and invaluable advice!