a first view of temperature fields from the microwave limb ... · a second-generation microwave...

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A First View of Temperature Fields from the Microwave Limb Sounder on AuraMichael J. Schwartz1, Gloria L. Manney1,2, Michelle L. Santee1, Jonathan H. Jiang1, Dong L. Wu1, Nathaniel J. Livesey1, Mark J. Filipiak3, Hugh C. Pumphrey3, Eric J. Fetzer1, Kirstin Kruger4 and Joe W. Waters1

1 Jet Propulsion Laboratory2 New Mexico Highlands University3 University of Edinburgh4 Alfred Wegener Institute for Polar and Marine Research

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http://mls.jpl.nasa.gov

1 Abstract

A second-generation Microwave Limb Sounder (MLS) was launched in July of 2004 as a part of the Earth Observing System (EOS) Aurasatellite. This instrument provides temperature fields co-located with atmospheric composition measurements from the upper tropospherethrough the mesosphere. In this poster we give an overview of the MLS temperature measurements from the first months of EOS Auraobservations. Of particular interest is the 3-dimensional evolution of temperatures in the Antarctic polar vortex during the late winter and springfinal warming, including the evolution of temperatures in the lower stratosphere associated with polar processing, and planetary wave evolutionduring vortex breakup.

2 MLS Temperature Retrieval

✦ MLS retrievals are broken into several “phases,” each of which has an associated temperature product. This approach allows for better consideration of the radiance errorbudget than the more usual “constrained quantity error” propagation.

✧ “Core” Temperature is based only upon the 118-GHz R1 radiometer and has the poorest vertical resolution but is least prone to retrieval instability.

✧ “CorePlusR2”, “CorePlusR3”, “CorePlusR4” and “CorePlusR5” retrievals add 190-GHz (R2), 240-GHz (R3), 640-GHz (R4) and 2500-GHz (R5) radiances respec-tively. The v01.45 and v01.46 CorePlusR2 and CorePlusR3 products are prone to oscillation due to inaccuracies in the modeling of R2 and R3 radiances in these early(“launch-ready”) versions of the algorithms.

✦ Retrieval performance is significantly improved in v01.50, which will be used in production processing starting in January of 2005, and will yield the first “public” MLSdataset.

✦ Maps and time-series plots on this poster are based upon (the similar) v01.45 and v01.46 “Core” temperatures, as few days have yet been processed with v01.50.

2.1 Vertical Averaging Kernels and Precision

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2Kernel, Integrated kernel

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February 0o N2D retrievals every 1.5o along orbit track

Retrieval grid: 6 per decade from 1000 to 0.1 hPa, 3 per decade from 0.1 to 0.001 hPa

Kernels for different levels (marked with +) are distinguished using color1K reg, T=Core

Plot made Monday August 2 07:27:02 GMT 2004from data file MLS-Aura_L2MTX-Full_bin0-pe-2D-standard-v1-3-8-l2pc01-v1-3-8-f02-v1-4-1-07_1996d051.h5 created Fri Jul 30 16:18:02 2004

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Kernels for different levels (marked with +) are distinguished using color1K reg, T=Core+R2

Plot made Friday July 30 15:13:26 GMT 2004from data file MLS-Aura_L2MTX-Full_bin0-pe-2D-standard-v1-3-8-l2pc01-v1-3-8-f02-v1-4-1-03_1996d051.h5 created Fri Jul 30 14:55:16 2004



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Plot made Friday July 30 15:25:52 GMT 2004from data file MLS-Aura_L2MTX-Full_bin0-pe-2D-standard-v1-3-8-l2pc01-v1-3-8-f02-v1-4-1-05_1996d051.h5 created Fri Jul 30 15:13:01 2004


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1K reg, T=Core+R2

Plot made Friday July 30 14:59:48 GMT 2004from data file MLS-Aura_L2GP-Temperature_bin0-pe-2D-standard-v1-3-8-l2pc01-v1-3-8-f02-v1-4-1-03_1996d051.he5 created Fri Jul 30 14:53:43 2004

Single profile precisionDaily 5o zonal mean and monthly map precisionMonthly 5o zonal mean precisionUncertainty > (a priori uncertainty) / 2

✦ The first three plots show modeled averaging kernels for three MLS v01.50 tem-perature products. Each product is a retrieval on 28 surfaces, 6 surfaces-per-decadefrom 316 hPa to 0.1 hPa and on 3 surfaces-per-decade from 0.1 hPa to 0.001 hPa.

✦ Dashed lines are the FWHM of the averaging kernels. The FWHM of the “Core”averaging kernels is 6 km at 1 hPa, improves to 4 km between 10 hPa and 32 hPabut degrades to 6 K at 100 hPa and 8 K at 147 hPa.

✦ “CorePlusR2” averaging kernels have FWHM of approximately 4 km through the

upper troposphere and lower stratosphere and are similar to those of “Core” higherin the atmosphere.

✦ The fourth plot shows single-profile precision for CorePlusR2 (right-most line)and the same line scaled to approximate daily and monthly-averaged values. Pre-cision for Core, CorePlusR2 and CorePlusR3 is similar (better than 1 K) in thestratosphere and above. “Core” precision degrades in the troposphere to 2 K at316 hPa, but “Core” has smaller biases relative to GMAO GEOS-4 than the otherphases. “CorePlusR2” temperature has precision of 0.9 K at 316 hPa.

2.2 Temperature Retrieval-Phase Comparison with GMAO GEOS-4

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✦ The “launch-ready” v01.45 and v01.46 “CorePlusR3” temperature displays large,persistent vertical oscillations in the upper troposphere and lower stratosphere, andsmaller oscillation are present in “CorePlusR2” temperatures. Retrieval stability

is significantly improved in v01.50, which will be the production software startingin January of 2005, but CorePlusR3 still swings from a -2.5 K bias w.r.t GEOS-4at 100 hPa to a +9 K bias at 316 hPa.

2.3 Comparison of MLS v1.5 Temperature Profiles with AIRS, HALOE and CHAMP GPS

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✦ Plots show MLS minus AIRS (IR on Aqua), HALOE (solar IR occultation onUARS), CHAMP (GPS occultation) and GMAO GEOS-4 (NASA Global Model-ing and Assimilation Office assimilation.) Error bars are the scatter of the profilecomparisons. The MLS temperature used is v1.5 “Core” 316 hPa to 1 hPa and“CorePlusR2” above.

✦ In the upper troposphere, MLS is 2 K cooler than HALOE and 1-2 K warmer thanCHAMP. Agreement is better than 1 K with GEOS-4 and AIRS.

✦ In the lower stratosphere (100-14.7 hPa), MLS is 1-2 K warmer than CHAMP andGEOS-4 and 2.5 K warmer than AIRS. HALOE varies from 0-4 K cooler thanMLS.

✦ MLS is 4-5 K warmer than the other sets at 10 hPa. In the comparison with GEOS-4, this is a sharp feature in altitude, while with respect to AIRS and HALOE, largebiases continue into the upper stratosphere.

✦ Agreement is to ±1 K in at 1.47 hPa, then MLS swings back and forth with respectto HALOE and GEOS-4. MLS is: 2 K warm at 0.68 hPa, 5 K cold at 0.1 hPa and5-7 K warm at 0.0215 hPa.

3 Maps of MLS Temperature on Isentropic Surfaces

✦ Maps show MLS v01.45 and v01.46 “Core” temperature on isentropic surfaces for seven days at roughly 20-day spacings.

✦ Three potential vorticity contours from the GEOS-4 analysis are shown in white. When closely-spaced and concentric, they mark thepolar vortex edge. Cold regions are not confined in the vortex in the way that atmospheric constituents are, but low temperatures dodevelop in the confined air mass of the vortex.

✦ Maps of temperature on isentropic surfaces show the temperatures through which air parcels can move adiabatically.

3.1 Northern Hemisphere

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2004d230 2004d239 2004d260 2004d280 2004d300 2004d319 2004d33517Aug2004 26Aug2004 16Sep2004 06Oct2004 26Oct2004 14Nov2004 30Nov2004

θ=2700 K

(H≈60 km)

(P≈0.2 hPa)

θ=1700 K

(H≈50 km)

(P≈1.5 hPa)

θ=850 K

(H≈32 km)

(P≈10 hPa)

θ=490 K

(H≈18 km)

(P≈56 hPa)

✦ Low temperatures are associated with the northern polar vortex on the 1700 K and 850 K isentropic surface as it spins up throughOctober.

✦ On the 490 K isentropic surface, the region of low temperatures associated with the vortex only begins to become apparent in the30-Nov map.

✦ Planetary wave activity disturbs the symmetry of the northern vortex at all times, as is characteristic of northern fall and winter.

3.2 Southern Hemisphere

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2004d230 2004d239 2004d260 2004d280 2004d300 2004d319 2004d33517Aug2004 26Aug2004 16Sep2004 06Oct2004 26Oct2004 14Nov2004 30Nov2004

θ=2700 K

(H≈60 km)

(P≈0.2 hPa)

θ=1700 K

(H≈50 km)

(P≈1.5 hPa)

θ=850 K

(H≈32 km)

(P≈10 hPa)

θ=490 K

(H≈18 km)

(P≈56 hPa)

✦ The southern vortex erodes from the top of the atmosphere downward, so winter-like low temperatures associated with the vortex persistthrough October on the 490-K isentropic surface. High temperatures are already present over the pole at the beginning of the time-serieson the 1700-K isentropic surface.

✦ The high temperatures move over the poles before the vortex breaks up, as is demonstrated by persisting, strong PV gradients.

✦ On the mesospheric 2700-K isentropic surface, there is strong mid-latitude wave activity in August, primarily wave-1 on August 17 andwave-2 on August 26.

4 Comparison of MLS, GEOS-4 and ECMWF Zonal Means and Planetary Waves

✦ Data are interpolated to daily maps on uniform lat/longrids and then zonal means and Fourier components alongindividual latitudes are calculated.

✦ Plots are linearly interpolated to provide a smoothed im-age. Points within days without data are marked withlighter colors.

✦ Line plots show phase (the longitude at which a wavepeaks) for the wave at 52S latitude. Agreement betweenthe analyses’ phases and that of MLS is generally within10◦. The most obvious discrepancies are due to phase-unwrapping problems associated with missing MLS data.

✦ Talks by Manney et al., Santee et al. in session A23F(Tuesday) provide more detailed description of MLS ob-

servation of the southern polar vortex and associatedchemistry and dynamics.

✦ Planetary wave activity is associated with the erosion andeventual breakup of the polar vortex. Wave-1 involves ashifting of the vortex off of the pole, resulting in one cyclearound the globe, while wave-2 involves a distortion of thevortex.

4.1 1-hPa Zonal Mean, and Wave-1, Wave-2 amplitudes

Day−of−Year 2004

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MLS 1−hPa Temperature Wave−1 Amplitude

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✦ Zonal mean temperatures at 1-hPa are in as good agree-ment with the GEOS-4 and ECMWF analyses as the anal-yses are with one another. The analyses become morepoorly constrained by data at these levels and higher, soMLS has the potential to contribute significantly to ourknowledge of mesospheric temperatures.

✦ The lowest temperatures in upper stratosphere are already

off the pole by the beginning of this time-series.

✦ Temperatures in the 40S-60S are lowest when not dis-turbed by wave-1. The late September wave-1 amplifica-tion is during final stages of vortex breakup in the upperstratosphere. The vortex is gone at this level by the begin-ning of October (2004d275).

✦ The MLS peak wave-1 amplitude, 2004d232 (Aug 19), is

between that of GEOS-4 and ECMWF.

✦ MLS misses some of the rapidly evolving wave featuresduring mid-September (ed 2004d255) because of gaps inthe MLS dataset. Some of these gaps will be filled in dur-ing reprocessing.

✦ The wave-1 amplification in late September is associatedwith the final breakup of the vortex in the stratosphere.



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✦ MLS zonal mean v01.46 temperatures have a 3-5 K highbias at 10 hPa. Profile comparisons with GEOS-4 showthis bias to be confined to a narrow altitude range.

✦ The vortex is essentially gone in mid-stratosphere (10 hPa)by the end of October (2004d304).

✦ Wave morphology is very similar among the three datasets.The biggest differences between the images are the resultof missing MLS data.



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✦ MLS 50-hPa zonal-mean temperatures have a 2-3 K highbias relative to GEOS-4 and ECMWF but the morpholo-gies of the three datasets are very similar.

✦ There is a distinct anti-correlation between wave-1 and

wave-2. Such an anti-correlation is often associated withnon-linear wave-wave interaction.

✦ Low temperatures are at the pole until mid-October, atwhich point summer-like conditions prevail, with high

temperatures at the pole. The vortex persists into Decem-ber although there is no associated pool of low tempera-tures at 50 hPa beyond the end of October.

5 Conclusions

✦ MLS v01.50 temperature, which will be the initialpublicly-released temperature data product, appears tohave a warm bias in the stratosphere of from 1-4 K, de-pending upon the level and the product with which com-parison is done. Validation activity is just beginning, sothis result should be considered preliminary.

✦ MLS v01.45 and v01.46 temperatures had larger biasesrelative to the validation sets examined, but still provide aview of temperature morphology, in association with polarprocesses, that is consistent with ECMWF and GEOS-4.Agreement between MLS and ECMWF or GEOS-4 is gen-erally about as good as the agreement between ECMWF

and GEOS-4.

✦ Reduction of biases in troposphere and stratosphere anddevelopment of a higher-vertical-resolution product for theupper-troposphere/lower-stratosphere is a priority.

✦ Validation of the mesospheric and lower-thermospheric re-trieval (to 0.0001 hPa ≈ 96 km) will begin soon.

a first view of temperature fields from the microwave limb ... · a second-generation microwave...

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