2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland Measurements Of Humidity in the Atmosphere and Validation Experiments (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 1 Jet 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

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland MOHAVE : October 2006 JPL-Table Mountain Facility, Wrightwood, Southern California Lat. 34.5ºN Elev m 13.95/14 cloud-free nights during MOHAVE (annual average>320) FAKE trailers on display! SRLAT

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland One example all 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 profiles all instruments together

2 nd 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: km for ALVICE 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)

2 nd 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

2 nd 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

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland MOHAVE Where?JPL Table Mountain Facility - When?12-26 October Who? - 3+ water vapor Raman lidar (Leblanc/JPL, McGee/GSFC, Whiteman/GSFC) CFH (Vomel/DWD) - ? NOAA Frost-Point Hygrometer (Oltmans/NOAA) - 1+ FTIR (Toon/JPL, who else?) - 2 Improved Microwave (Nedoluha/NRL, Kampfer/Univ. Bern) Vaisala RS92 PTU radiosondes (Leblanc/JPL) 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

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

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

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland MOHAVE 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 H 2 O / N 2 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 H 2 O 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

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

2 nd 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 filter in front of optical fiber 3/ Acquire data with additional 355 nm blocking filter immediately after the optical fiber

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

2 nd 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 km - RH differences well below standard deviations JPL and GSFC AT lidar comparison

2 nd 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-CFH WAVES+MOHAVE campaigns + ARM site RS92 uncorrected (far left) and time-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

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland 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 receivers but the same resolution came out: ALL 3 LIDAR RECEIVERS MUST BE RE-CONFIGURED TO SUPPRESS FLUORESCENCE then meet again for…

2 nd 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)

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland MOHAVE 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 H 2 O / N 2 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 H 2 O 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

2 nd 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

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

2 nd 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

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland SUMMARY 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 shortfalls of widely used calibration techniques, Important implications for applicability to long-term measurements 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 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

2 nd ISSI Workshop on Water Vapor Instruments, 3-6 November 2008, Bern, Switzerland WHAT’S NEXT ? 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 A wealth of science (and validation) results is still to come (stratospheric intrusions, simultaneous tropospheric ozone and water vapor, total column, etc.)