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Thierry Leblanc 1 , Stuart McDermid 1 Holger Vömel 2

M easurements O f H umidity in the A tmosphere and V alidation E xperiments (MOHAVE and MOHAVE II) Results overview. Thierry Leblanc 1 , Stuart McDermid 1 Holger Vömel 2 Dave Whiteman 3 , Larry Twigg 3 , and Tom McGee 3 Larry Miloshevich 4

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Thierry Leblanc 1 , Stuart McDermid 1 Holger Vömel 2

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  1. Measurements Of Humidity in the Atmosphereand Validation Experiments (MOHAVE and MOHAVE II)Results 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. USA 2 University of Colorado, CIRES, Boulder, CO. USA 3 NASA Goddard Space Flight Center, Greenbelt, MD. USA 4 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  2. MOHAVE : 14-28 October 2006 JPL-Table Mountain Facility, Wrightwood, Southern CaliforniaLat. 34.5ºN Elev. 2300 m13.95/14 cloud-free nights during MOHAVE (annual average>320) SRL AT FAKE trailers on display! 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  3. One exampleall 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 Average of 4 profilesall instruments together - Systematic bias now clear - Only 4 profiles including all instruments simultaneously - Lidar wet bias with respect to CFH increasing with height  Fluorescence suspected 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  4. 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) 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  5. MOHAVE II Dotted: RS92 zero reference, also time-altitude position Another example below (JPL lidar, 10/10/2007) Solid: RS92 departure from nightly mean Water vapor (lidar) Departure from nightly mean This high variability (+/-100% within 1-2 hours raises the important issue of calibration using a non-strictly coincident measurement (e.g., radiosonde) 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  6. MOHAVE II: Aura/MLS water vapor validation Best TMF-MLS overpass shown below 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  7. MOHAVE 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  8. MOTIVATION • Water Vapor (WV) in UT/LS plays a major radiative role • WV in UT/LS variability and trends not yet well understood • Accurate WV measurements in the UT/LS remains very difficult • NDACC (formerly NDSC) recently included WV Raman lidar among 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… 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  9. MOHAVE • 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) 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  10. MOHAVE Lidar characteristics (overview) GSFC / SRL* GSFC / AT JPL/TMF 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 Telescopes diam 76 cm , 25 cm 91 cm 91 , 7.5 cm Telescopes fov 0.25 , 2.5 mrad 1.9 mrad 0.6 , 10 mrad H2O / N2 pairs 2 x 407/387 nm 1 x 407/387 nm 3 x 407/387 nm H2O filter width 0.25 nm 1 nm 0.6 nm Other channels 2 polar. , 1 liquid 4 Ram , 6 Ray 3 Ray * Resuscitated 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  11. MOHAVE 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  12. 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  13. Comparisons “with” vs. “without” 355 nm block (JPL lidar) Below (left): Presence of fluorescence in lidar receiver Below (right): 355 nm blocking filter inserted at lidar receiver entrance Not shown: Fluorescence not removed if same block placed after fiber (not shown) 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, agreement with CFH becomes very good 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  14. JPL and GSFC AT lidar comparison • - 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  15. RS92 - CFH comparisons 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 All RS92 show dry bias w.r.t. to CFH (similar to previous Vaisala sensors) Good repeatability of all RS92 pairs Left: RS92-CFH WAVES+MOHAVE campaigns + ARM site RS92 uncorrected (far left) and time-lag + empirically corrected (right) by L. Miloshevich, NCAR (2008) Courtesy of L. Miloshevich 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  16. LESSONS LEARNED FROM MOHAVE : ALL 3 RAMAN LIDARS SHOWED PRESENCE OF FLUORESCENCE IN THEIR RECEIVER Fluorescence was not detected in the same part of the receiversbut the same resolution came out: ALL 3 LIDAR RECEIVERS MUST BE RE-CONFIGURED TO SUPPRESS FLUORESCENCE then meet again for… 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  17. MOHAVE II : 6-17 October 2007 Campaign operations similar to MOHAVE 3 co-located WV Raman lidars (improved receivers) AT Lidar (McGee, GSFC) SRL ALVICE (new system, Whiteman, GSFC) JPL-TMF (Leblanc/McDermid, JPL) 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) 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  18. MOHAVE II Lidar characteristics (overview) ** GSFC / ALVICE GSFC / AT JPL/TMF Laser out 355 nm 355 , 532 , 1064 nm 355 nm Energy/pulse 350 mJ90 mJ 700 mJ Rep. rate 50 Hz 50 Hz 10 Hz Power 17.5 W 4.5 W 7 W Telescopes diam 60 cm 91 , 10 cm 91 , 7.5 cm Telescopes fov 0.2 mrad 1.9 , 4.5 mrad 0.6 , 5 mrad H2O / N2 pairs 1 x 407/387 nm 2 x 407/387 nm 3 x 407/387 nm H2O filter width 0.25 nm .25 nm 0.6 nm Other channels 2 polar. , 1 liquid 4 Ram , 7 Ray 3 Ray ** All 3 instruments: New “fluorescence-free” Barr optics 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  19. MOHAVE II ALVICE vs. JPL : Difference within 5-7% up to 12 km then noise limited 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  20. 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) Upper tropospheric dry tongues penetrate into lower troposphere Meanwhile, humidifying trend in the upper troposphere throughout the night 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  21. 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 To achieve 5% accuracy required for the detection of long-term trend, an hybrid method was proposed 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) 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  22. SUMMARY 1. MOHAVE + MOHAVE II = both successful 2. MOHAVE  Fluorescence found in all three participating lidars • MOHAVE II  Fluorescence removed, • resulting in much better agreement with CFH in UT/LS • MOHAVE II  Calibration tests revealed shortfalls • of widely used calibration techniques, • Important implications for applicability to long-term measurements • The JPL lidar does reach expected range when compared to ALVICE •  tests are ongoing to track the cause of signal loss 6. A factor of 4 in lidar signal-to-noise ratio should 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 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

  23. WHAT’S NEXT ? A wealth of science (and validation) results is still to come(stratospheric intrusions, simultaneous tropospheric ozone and water vapor, total column, etc.) MOHAVE 2009 planned for October 2009 will host more instruments: 2 microwave, 1 FTUVS, 1 FTIR, etc. will be more science-oriented than MOHAVE and MOHAVE II 2nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland

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