22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MMeasurements easurements OOf f HHumidity in the umidity in the AAtmospheretmosphereand and VValidation alidation EExperiments (MOHAVE and MOHAVE II)xperiments (MOHAVE and MOHAVE II)
Results overviewResults overview
Thierry Leblanc1, Stuart McDermid1
Holger Vömel2
Dave Whiteman3, Larry Twigg3, and Tom McGee3
Larry Miloshevich4
1Jet Propulsion Laboratory, California Institute of Technology, Wrightwood, CA. USA2 University of Colorado, CIRES, Boulder, CO. USA
3 NASA Goddard Space Flight Center, Greenbelt, MD. USA4 National Center for Atmospheric Research, Boulder , CO
Thanks to:B. Demoz, G. Nedoluha, D. Venable, G. McIntyre, G. Sumnicht, K. Rush, M. Cadirola, R. Forno, T. Manucci, C. on Ao, P. Glatefelter, M. Colgan, R. Connell, S. Oltmans, B. Johnson, J. Howe, T. Grigsby, D. Walsh
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVE : 14-28 October 2006
JPL-Table Mountain Facility, Wrightwood, Southern CaliforniaLat. 34.5ºN Elev. 2300 m
13.95/14 cloud-free nights during MOHAVE (annual average>320)
FAKE trailers on display!FAKE trailers on display!
SRLSRL ATAT
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
One exampleOne exampleall instruments togetherall instruments together
- Thin layered structures well captured by all instruments
- Very small difference between the two RS92
- Lidar profiles start getting noisy above 12 km
- RS92 dry and lidars wet with respect to CFH
- Systematic bias now clear
- Only 4 profiles including all instruments simultaneously
- Lidar wet bias with respect to CFH increasing with height
Fluorescence suspected
Average of 4 profilesAverage of 4 profilesall instruments togetherall instruments together
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVE II
Main Result :No more sign of fluorescence
All lidars agree well with CFH up to 12 km
1-hour lidar integration reaches in average: - 18-19 km for ALVICE - 15-16 km for JPL - 13 km for AT
MOHAVEs + WAVES campaigns: New RS92 time-lag + dry bias correction by Larry Miloshevich, NCAR
Question:Why does ALVICE go higher than JPL?
Answer:Not sure (JPL gained factor 2 since the end of the campaign but not sufficient)
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVE II
Another example below (JPL lidar, 10/10/2007)
This high variability (+/-100% within 1-2 hours raises the important issue of calibration using a non-strictly coincident measurement (e.g., radiosonde)
Water vapor (lidar) Departure from nightly mean
Solid: RS92 departure from nightly mean
Dotted: RS92 zero reference, also time-altitude position
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
Besides lack of co-location and simultaneity, and differing vertical resolution and registration, the variability shown on JPL lidar profile within the same
night illustrates difficulty to validate satellite WV measurements
MOHAVE II: Aura/MLS water vapor validation
Best TMF-MLS overpass shown below
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVE 2009MOHAVE 2009- Where? JPL Table Mountain Facility
- When? 12-26 October 2009
- Who?
- 3+ water vapor Raman lidar (Leblanc/JPL, McGee/GSFC, Whiteman/GSFC)
- 15+ CFH (Vomel/DWD)
- ? NOAA Frost-Point Hygrometer (Oltmans/NOAA)
- 1+ FTIR (Toon/JPL, who else?)
- 2 Improved Microwave (Nedoluha/NRL, Kampfer/Univ. Bern)
- 50+ Vaisala RS92 PTU radiosondes (Leblanc/JPL)
- 15+ IMET PTU radiosondes (Leblanc/McDermid/JPL)
- Also ECC ozonesondes, ozone lidar, T lidar
- Also 3D transport model MIMOSA-UT/LS for cirrus and water vapor transport
MAIN OBJECTIVES:
Validation of lidar H2O above 15 km
Validation of new microwave (especially below 25 km)
Inter-comparison of FTIR, GPS and microwave TWC
Case studies of UTH transport in the vicinity of the sub-tropical jet
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOTIVATIONMOTIVATION
1. Water Vapor (WV) in UT/LS plays a major radiative role
2. WV in UT/LS variability and trends not yet well understood
3. Accurate WV measurements in the UT/LS remains very difficult
NDACC (formerly NDSC) recently included WV Raman lidaramong its suite of long-term monitoring instruments
The MOHAVE and MOHAVE II campaigns (Oct 2006 and Oct 2007)were designed to evaluate the current (and future)
measuring capabilities of the WV Raman lidars in the UT/LS
Each campaign involved 5 lidars, >40 PTU sondes, 10 CFH sondes, GPS, and more…
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVEMOHAVE
3 co-located WV Raman lidars:
AT Lidar (McGee, GSFC)
SRL temporarily “resuscitated” (Whiteman, GSFC)
JPL-TMF (Leblanc/McDermid, JPL)
49 simultaneous co-located Vaisala RS92 PTU profiles
10 simultaneous co-located ECC/CFH profiles
2 co-located GPS receivers and one WV Microwave
>250 hours of WV lidar measurements (total)
(also 80 hours of tropospheric O3 measurements 3-27 km)
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVEMOHAVE
Lidar characteristics (overview)
Laser out 355 nm 355 , 532 , 1064 nm 355 nm
Energy/pulse 300 mJ 200 mJ 700 mJ
Rep. rate 30 Hz 50 Hz 10 Hz
Power 9 W 10 W 7 W
H2O / N2 pairs 2 x 407/387 nm 1 x 407/387 nm 3 x 407/387 nm
Telescopes diam 76 cm , 25 cm 91 cm 91 , 7.5 cm
Other channels 2 polar. , 1 liquid 4 Ram , 6 Ray 3 Ray
GSFC / SRL* GSFC / AT JPL/TMF
H2O filter width 0.25 nm 1 nm 0.6 nm
Telescopes fov 0.25 , 2.5 mrad 1.9 mrad 0.6 , 10 mrad
* Resuscitated
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVE operationsMOHAVE operations
1/ Target nights: 14 nights centered to new moon
2/ New moon first priority, Aura-TMF overpasses next priority
3/ CFH : reference instrument at least 1 CFH launch per night (2 CFH launches on highest priority night)
4/ RS92 : 1 to 5 pairs per night, including one on same payload as CFH
5/ All lidar data analyzed for 1-hour segment following each launch
6/ MOHAVE campaign split in 2 main periods:
10/14-10/23 = mainly nominal operations (except SRL)
10/25-10/28 = Many tests related to fluorescence
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
Is this really fluorescence, as suspected?
For the JPL lidar, three tests were made on the same night:
1/ Acquire data in “normal” configuration
2/ Acquire data with additional 355 nm blocking filterin front of optical fiber
3/ Acquire data with additional 355 nm blocking filterimmediately after the optical fiber
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
Below (left): Presence of fluorescence in lidar receiver
Comparisons “Comparisons “with” with” vs.vs. “without” “without” 355 nm block (JPL lidar) 355 nm block (JPL lidar)
Left (bottom):Empirical correction = 1/700 of 387 nm low-intensity signal subtracted from H20 signal (no 355 nm signal available in troposphere)
when fluorescence is removed,when fluorescence is removed,agreement with CFH becomes very goodagreement with CFH becomes very good
Below (right): 355 nm blocking filter insertedat lidar receiver entrance
Not shown: Fluorescence not removed if same block placed after fiber (not shown)
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
- No apparent systematic bias- Only bias associated with calibration method
- RH differences peak at 2% near 10-11 km- RH differences well below standard deviations
JPL and GSFC AT lidar comparison
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
3 datasets:
1/ RS92, no GPS(DG 2.7 soft)
2/ RS92 w/ GPS(DG 3.5 soft)
3/ RS92 no GPS processed w/ 3.5
RS92 - CFH comparisons
Left: RS92-CFHWAVES+MOHAVE campaigns + ARM siteRS92 uncorrected (far left) andtime-lag + empirically corrected (right)by L. Miloshevich, NCAR (2008)
All RS92 show dry bias w.r.t. to CFH(similar to previous Vaisala sensors)
Good repeatability of all RS92 pairs
Courtesy of L. Miloshevich
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
LESSONS LEARNED FROM MOHAVE :LESSONS LEARNED FROM MOHAVE :
ALL 3 RAMAN LIDARS SHOWED PRESENCE OF ALL 3 RAMAN LIDARS SHOWED PRESENCE OF FLUORESCENCE IN THEIR RECEIVERFLUORESCENCE IN THEIR RECEIVER
Fluorescence was not detected Fluorescence was not detected in the same part of the receiversin the same part of the receivers
but the same resolution came out:but the same resolution came out:
ALL 3 LIDAR RECEIVERS MUST BE RE-CONFIGURED TO ALL 3 LIDAR RECEIVERS MUST BE RE-CONFIGURED TO SUPPRESS FLUORESCENCESUPPRESS FLUORESCENCE
then meet again for…then meet again for…
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
3 co-located WV Raman lidars (improved receivers)
AT Lidar (McGee, GSFC)
SRL ALVICE (new system, Whiteman, GSFC)
JPL-TMF (Leblanc/McDermid, JPL)
MOHAVE II : 6-17 October 2007
Campaign operations similar to MOHAVE
41 simultaneous co-located RS92 profiles (no pairs this time)
10 simultaneous co-located ECC/CFH profiles
240 hours of WV lidar measurements (total)
(also 80 hours of tropospheric O3 measurements 3-27 km)
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
MOHAVE IIMOHAVE II
Lidar characteristics (overview) **
Laser out 355 nm 355 , 532 , 1064 nm 355 nm
Energy/pulse 350 mJ 90 mJ 700 mJ
Rep. rate 50 Hz 50 Hz 10 Hz
Power 17.5 W 4.5 W 7 W
H2O / N2 pairs 1 x 407/387 nm 2 x 407/387 nm 3 x 407/387 nm
Telescopes diam 60 cm 91 , 10 cm 91 , 7.5 cm
Other channels 2 polar. , 1 liquid 4 Ram , 7 Ray 3 Ray
GSFC / ALVICE GSFC / AT JPL/TMF
H2O filter width 0.25 nm .25 nm 0.6 nm
Telescopes fov 0.2 mrad 1.9 , 4.5 mrad 0.6 , 5 mrad
** All 3 instruments: New “fluorescence-free” Barr optics
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
ALVICE vs. JPL :
Difference within 5-7% up to 12 km
then noise limited
MOHAVE II
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
Upper tropospheric dry Upper tropospheric dry tongues penetrate into tongues penetrate into lower tropospherelower troposphere
Meanwhile, humidifying Meanwhile, humidifying trend in the upper trend in the upper troposphere throughout troposphere throughout the nightthe night
MOHAVE II: more weather-related disturbed conditions than MOHAVE (humidity-wise)
high WV variability at short time scales (two examples below from the JPL lidar)
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
Calibration tests during MOHAVE II (JPL lidar)
Tests showed that calibration from not strictly co-located and simultaneous radiosonde can still yield 10-15% (poor) accuracy during atmospherically
disturbed nights
New hybrid method uses daily partial calibration of the lidar receiver using a stable calibrated lamp, and a campaign-basis absolute calibration using multiple radiosondes and the lamp
New method allows daily tracking of 2% expected or unexpected lidar receiver changes together with long-term stability suitable for long-term
measurements
Method was described in Poster = Monday session too late!(contact Thierry Leblanc if interested)
To achieve 5% accuracy required for the detection of long-term trend, an hybrid method was proposed
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
SUMMARYSUMMARY
2. MOHAVE Fluorescence found in all three participating lidars
3. MOHAVE II Fluorescence removed,resulting in much better agreement with CFH in UT/LS
4. MOHAVE II Calibration tests revealed shortfallsof widely used calibration techniques,
Important implications for applicability to long-term measurements
6. A factor of 4 in lidar signal-to-noise ratioshould be reasonably achievable in the near-future
When this level is achieved, water vapor Raman lidar will become a key instrument for the long-term monitoring of water vapor in the UT/LS
1. MOHAVE + MOHAVE II = both successful
5. The JPL lidar does reach expected range when compared to ALVICE tests are ongoing to track the cause of signal loss
22ndnd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland
WHAT’S NEXT ?WHAT’S NEXT ?
MOHAVE 2009planned for October 2009
will host more instruments: 2 microwave, 1 FTUVS, 1 FTIR, etc.
will be more science-oriented than MOHAVE and MOHAVE II
A wealth of science (and validation) results is still to come(stratospheric intrusions, simultaneous tropospheric ozone and
water vapor, total column, etc.)