Cooperative Institute for Research in Environmental Sciences

Dale Hurst

Dale Hurst

Research Interests

  • High altitude measurements of water vapor and other trace gases, especially those influencing climate and stratospheric ozone
  • Determination and attribution of the inter-annual variability and longer-term trends in stratospheric water vapor and other trace gases
  • Statistical validations of atmospheric composition measurements by satellite-based remote sensors using in situ measurements from balloons and aircraft
  • Improvement of atmospheric composition measurements from mobile platforms including trains, aircraft and balloons

Current Research

I oversee a research team that builds and deploys compact, lightweight, custom-made, balloon-borne frost NOAA point hygrometers (FPHs) that measure atmospheric water vapor profiles from the surface to ~28 km at three sites around the world: Boulder, Colorado; Hilo, Hawaii; and Lauder, New Zealand. Profiles are obtained monthly at each site to compile long-term records of atmospheric water vapor, with a focus on the upper troposphere and lower stratosphere (UTLS) region. The FPH measurements at Boulder date back to 1980 and comprise the longest continuous record of UTLS water vapor in the world. Flight data, including FPH, ozone sonde and radiosonde measurements, are processed, quality controlled and archived by our team here in Boulder.

There are several goals of this research. First (and foremost) is to amass and analyze records of UTLS water vapor over decadal time scales to detect inter-annual variations and longer-term trends in UTLS water vapor driven by variations in atmospheric dynamics. Water vapor changes due to periodic dynamical variations (QBO, ENSO) are present in the FPH records. Our FPH profiles also provide invaluable validation data for UTLS water vapor measurements by satellite-based remote sensors to ensure their accuracy and long-term measurement stability. In 2017 we began launching instrumented balloons in coordination with overpasses of the SAGE-III instrument aboard the International Space Station to validate its measurements of stratospheric water vapor, ozone and aerosols. The FPH time series of water vapor measurements also provide validation data for numerical model simulations of moisture in the UTLS region.

Our team is also regularly involved in field research sponsored by NASA and NSF, predominantly to support scientific campaigns using high-altitude aircraft. We have launched balloons from many locations including New Mexico, California, Hawaii, Guam and Kunming, China.



Dale explains the measurements of some of instruments aboard the NSF/NCAR Gulfstream-V research aircraft to a tour group during the START-08 mission (2008; NCAR Research Aviation Facility, Broomfield, CO)

Dale watches over the ACATS 4-channel gas chromatograph measuring CFCs during the 14-day transit across Russia on the Trans-Siberian Railway as part of the TROICA-7 experiment (2001; somewhere in Siberia)

Dale configuring the instrument rack that will anchor the ACATS-IV gas chromatograph aboard the NASA ER-2 high-altitude aircraft during the SOLVE mission in northern Sweden (1999, NASA Dryden Flight Research Center, Edwards Air Force Base, CA)

Honors and Awards

  • 2016 - Väisälä Award for Outstanding Research Paper (WMO)
  • 2013 - NOAA Bronze Medal (team award)
  • 2007 - NOAA Bronze Medal (team award)
  • 2005 - NOAA/OAR Outstanding Scientific Paper
  • 2000 - CIRES Outstanding Performance Award
  • 1993 - National Research Council Postdoctoral Associateship
  • 1990 - Australian Research Council Postdoctoral Fellowship
  • 1989 - Outstanding Student Speaker Award (UC Irvine)
  • 1983 - American Institute of Chemists Award (UC Irvine)

View Publications

  • Bodeker, GE, S Bojinski, D Cimini, RJ Dirksen, M Haeffelin, JW Hannigan, DF Hurst, T Leblanc, F Madonna, M Maturilli, AC Mikalsen, R Philipona, T Reale, DJ Seidel, DGH Tan, PW Thorne, H Vomel and J Wang (2016), REFERENCE UPPER-AIR OBSERVATIONS FOR CLIMATE From Concept to Reality. Bull. Amer. Meteorol. Soc. Version: 1 97 (1) 123-135, issn: 0003-0007, ids: DD6WZ
  • Hall, EG, AF Jordan, DF Hurst, SJ Oltmans, H Vomel, B Kuhnreich and V Ebert (2016), Advancements, measurement uncertainties, and recent comparisons of the NOAA frost point hygrometer. Atmos. Meas. Tech. Version: 1 9 (9) 4295-4310, issn: 1867-1381, ids: DW8GB, doi: 10.5194/amt-9-4295-2016
  • Hurst, DF, WG Read, H Vomel, HB Selkirk, KH Rosenlof, SM Davis, EG Hall, AF Jordan and SJ Oltmans (2016), Recent divergences in stratospheric water vapor measurements by frost point hygrometers and the Aura Microwave Limb Sounder. Atmos. Meas. Tech. Version: 1 9 (9) 4447-4457, issn: 1867-1381, ids: DW9VC, doi: 10.5194/amt-9-4447-2016
  • Krauchi, A, R Philipona, G Romanens, DF Hurst, EG Hall and AF Jordan (2016), Controlled weather balloon ascents and descents for atmospheric research and climate monitoring. Atmos. Meas. Tech. Version: 1 9 (3) 929-938, issn: 1867-1381, ids: DL4NF, doi: 10.5194/amt-9-929-2016
  • Weigel, K, A Rozanov, F Azam, K Bramstedt, R Damadeo, KU Eichmann, C Gebhardt, D Hurst, M Kraemer, S Lossow, W Read, N Spelten, GP Stiller, KA Walker, M Weber, H Bovensmann and JP Burrows (2016), UTLS water vapour from SCIAMACHY limb measurements V3.01 (2002-2012). Atmos. Meas. Tech. Version: 1 9 (1) 133-158, issn: 1867-1381, ids: DL4MI, doi: 10.5194/amt-9-133-2016
  • Muller, R, A Kunz, DF Hurst, C Rolf, M Kramer and M Riese (2016), The need for accurate long-term measurements of water vapor in the upper troposphere and lower stratosphere with global coverage. Earth's Future Version: 1 4 (2) 25-32, issn: 2328-4277, ids: DH6WA, doi: 10.1002/2015EF000321
  • Davis, S.M., K.H. Rosenlof, D.F. Hurst, and H.B. Selkirk (2016), Stratospheric Water Vapor in State of the Climate in 2014. Bull. Amer. Meteorol. Soc. Version: 1 97 (8) S51-S53, doi: 10.1175/2016BAMSStateoftheClimate.1
  • Davis, Sean M., Karen H. Rosenlof, Birgit Hassler, Dale F. Hurst, William G. Read, Holger Vomel, Henry Selkirk, Masatomo Fujiwara and Robert Damadeo (2016), The Stratospheric Water and Ozone Satellite Homogenized (SWOOSH) database: a long-term database for climate studies. Earth Syst. Sci. Data Version: 1 8 (2) 461-490, issn: 1866-3508, doi: 10.5194/essd-8-461-2016
  • Hurst, DF, A Lambert, WG Read, SM Davis, KH Rosenlof, EG Hall, AF Jordan and SJ Oltmans (2014), Validation of Aura Microwave Limb Sounder stratospheric water vapor measurements by the NOAA frost point hygrometer. J. Geophys. Res.-Atmos. Version: 1 119 (3) 1612-1625, issn: 2169-897X, ids: AD1LD, doi: 10.1002/2013JD020757
  • Dirksen, RJ, M Sommer, FJ Immler, DF Hurst, R Kivi and H Vomel (2014), Reference quality upper-air measurements: GRUAN data processing for the Vaisala RS92 radiosonde. Atmos. Meas. Tech. Version: 1 7 (12) 4463-4490, issn: 1867-1381, ids: CF1GA, doi: 10.5194/amt-7-4463-2014
  • Patra, PK, MC Krol, SA Montzka, T Arnold, EL Atlas, BR Lintner, BB Stephens, B Xiang, JW Elkins, PJ Fraser, A Ghosh, EJ Hintsa, DF Hurst, K Ishijima, PB Krummel, BR Miller, K Miyazaki, FL Moore, J Muhle, S O'Doherty, RG Prinn, LP Steele, M Takigawa, HJ Wang, RF Weiss, SC Wofsy and D Young (2014), Observational evidence for interhemispheric hydroxyl-radical parity. Nature Version: 1 513 (7517) 219-223, issn: 0028-0836, ids: AO5DP, doi: 10.1038/nature13721, PubMed ID: 25209800
  • Rollins, AW, TD Thornberry, RS Gao, JB Smith, DS Sayres, MR Sargent, C Schiller, M Kramer, N Spelten, DF Hurst, AF Jordan, EG Hall, H Vomel, GS Diskin, JR Podolske, LE Christensen, KH Rosenlof, EJ Jensen and DW Fahey (2014), Evaluation of UT/LS hygrometer accuracy by intercomparison during the NASA MACPEX mission. J. Geophys. Res.-Atmos. Version: 1 119 (4) 1915-1935, issn: 2169-897X, ids: AD3KP, doi: 10.1002/2013JD020817
  • Santoni, GW, BC Daube, EA Kort, R Jimenez, S Park, JV Pittman, E Gottlieb, B Xiang, MS Zahniser, DD Nelson, JB McManus, J Peischl, TB Ryerson, JS Holloway, AE Andrews, C Sweeney, B Hall, EJ Hintsa, FL Moore, JW Elkins, DF Hurst, BB Stephens, J Bent and SC Wofsy (2014), Evaluation of the airborne quantum cascade laser spectrometer (QCLS) measurements of the carbon and greenhouse gas suite - CO2, CH4, N2O, and CO - during the CalNex and HIPPO campaigns. Atmos. Meas. Tech. Version: 1 7 (6) 1509-1526, issn: 1867-1381, ids: AM5YB, doi: 10.5194/amt-7-1509-2014
  • Hegglin, MI, DA Plummer, TG Shepherd, JF Scinocca, J Anderson, L Froidevaux, B Funke, D Hurst, A Rozanov, J Urban, T von Clarmann, KA Walker, HJ Wang, S Tegtmeier and K Weigel (2014), Vertical structure of stratospheric water vapour trends derived from merged satellite data. Nature Geosci. Version: 1 7 (10) 768-776, issn: 1752-0894, ids: AQ8VC, doi: 10.1038/NGEO2236
  • Waugh, DW, AM Crotwell, EJ Dlugokencky, GS Dutton, JW Elkins, BD Hall, EJ Hintsa, DF Hurst, SA Montzka, DJ Mondeel, FL Moore, JD Nance, EA Ray, SD Steenrod, SE Strahan and C Sweeney (2013), Tropospheric SF6: Age of air from the Northern Hemisphere midlatitude surface. J. Geophys. Res.-Atmos. Version: 1 118 (19) 11429-11441, issn: 2169-897X, ids: 297PF, doi: 10.1002/jgrd.50848
  • Kunz, A, R Muller, V Homonnai, IM Janosi, D Hurst, A Rap, PM Forster, F Rohrer, N Spelten and M Riese (2013), Extending water vapor trend observations over Boulder into the tropopause region: Trend uncertainties and resulting radiative forcing. J. Geophys. Res.-Atmos. Version: 1 118 (19) 11269-11284, issn: 2169-897X, ids: 297PF, doi: 10.1002/jgrd.50831
  • Fueglistaler, S, YS Liu, TJ Flannaghan, PH Haynes, DP Dee, WJ Read, EE Remsberg, LW Thomason, DF Hurst, JR Lanzante and PF Bernath (2013), The relation between atmospheric humidity and temperature trends for stratospheric water. J. Geophys. Res.-Atmos. Version: 1 118 (2) 1052-1074, issn: 2169-897X, ids: 129KN, doi: 10.1002/jgrd.50157
  • Nedoluha, GE, RM Gomez, H Neal, A Lambert, D Hurst, C Boone and G Stiller (2013), Validation of long-term measurements of water vapor from the midstratosphere to the mesosphere at two Network for the Detection of Atmospheric Composition Change sites. J. Geophys. Res.-Atmos. Version: 1 118 (2) 934-942, issn: 2169-897X, ids: 129KN, doi: 10.1029/2012JD018900
  • Kort, EA, SC Wofsy, BC Daube, M Diao, JW Elkins, RS Gao, EJ Hintsa, DF Hurst, R Jimenez, FL Moore, JR Spackman and MA Zondlo (2012), Atmospheric observations of Arctic Ocean methane emissions up to 82 degrees north. Nature Geosci. Version: 1 5 (5) 318-321, issn: 1752-0894, ids: 934RP, doi: 10.1038/NGEO1452
  • Whiteman, DN, M Cadirola, D Venable, M Calhoun, L Miloshevich, K Vermeesch, L Twigg, A Dirisu, D Hurst, E Hall, A Jordan and H Vomel (2012), Correction technique for Raman water vapor lidar signal-dependent bias and suitability for water vapor trend monitoring in the upper troposphere. Atmos. Meas. Tech. Version: 1 5 (11) 2893-2916, issn: 1867-1381, ids: 046ZK, doi: 10.5194/amt-5-2893-2012
  • Stiller, GP, M Kiefer, E Eckert, T von Clarmann, S Kellmann, M Garcia-Comas, B Funke, T Leblanc, E Fetzer, L Froidevaux, M Gomez, E Hall, D Hurst, A Jordan, N Kampfer, A Lambert, IS McDermid, T McGee, L Miloshevich, G Nedoluha, W Read, M Schneider, M Schwartz, C Straub, G Toon, LW Twigg, K Walker and DN Whiteman (2012), Validation of MIPAS IMK/IAA temperature, water vapor, and ozone profiles with MOHAVE-2009 campaign measurements. Atmos. Meas. Tech. Version: 1 5 (2) 289-320, issn: 1867-1381, ids: 900HD, doi: 10.5194/amt-5-289-2012
  • Hurst, DF, EG Hall, AF Jordan, LM Miloshevich, DN Whiteman, T Leblanc, D Walsh, H Vomel and SJ Oltmans (2011), Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE-2009. Atmos. Meas. Tech. Version: 1 4 (12) 2777-2793, issn: 1867-1381, ids: 867ZD, doi: 10.5194/amt-4-2777-2011
  • Hall, BD, GS Dutton, DJ Mondeel, JD Nance, M Rigby, JH Butler, FL Moore, DF Hurst and JW Elkins (2011), Improving measurements of SF6 for the study of atmospheric transport and emissions. Atmos. Meas. Tech. Version: 1 4 (11) 2441-2451, issn: 1867-1381, ids: 863AS, doi: 10.5194/amt-4-2441-2011
  • Kort, EA, PK Patra, K Ishijima, BC Daube, R Jimenez, J Elkins, D Hurst, FL Moore, C Sweeney and SC Wofsy (2011), Tropospheric distribution and variability of N2O: Evidence for strong tropical emissions. Geophys. Res. Lett. Version: 1 38 , Art. No. L15806, issn: 0094-8276, ids: 804JZ, doi: 10.1029/2011GL047612
  • Hurst, DF, SJ Oltmans, H Vomel, KH Rosenlof, SM Davis, EA Ray, EG Hall and AF Jordan (2011), Stratospheric water vapor trends over Boulder, Colorado: Analysis of the 30 year Boulder record. J. Geophys. Res.-Atmos. Version: 1 116 , Art. No. D02306, issn: 2169-897X, ids: 713SF, doi: 10.1029/2010JD015065
  • Leblanc, T, TD Walsh, IS McDermid, GC Toon, JF Blavier, B Haines, WG Read, B Herman, E Fetzer, S Sander, T Pongetti, DN Whiteman, TG McGee, L Twigg, G Sumnicht, D Venable, M Calhoun, A Dirisu, D Hurst, A Jordan, E Hall, L Miloshevich, H Vomel, C Straub, N Kampfer, GE Nedoluha, RM Gomez, K Holub, S Gutman, J Braun, T Vanhove, G Stiller and A Hauchecorne (2011), Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE)-2009: overview of campaign operations and results. Atmos. Meas. Tech. Version: 1 4 (12) 2579-2605, issn: 1867-1381, ids: 867ZD, doi: 10.5194/amt-4-2579-2011
  • Wunch, D, GC Toon, PO Wennberg, SC Wofsy, BB Stephens, ML Fischer, O Uchino, JB Abshire, P Bernath, SC Biraud, JFL Blavier, C Boone, KP Bowman, EV Browell, T Campos, BJ Connor, BC Daube, NM Deutscher, M Diao, JW Elkins, C Gerbig, E Gottlieb, DWT Griffith, DF Hurst, R Jimenez, G Keppel-Aleks, EA Kort, R Macatangay, T Machida, H Matsueda, F Moore, I Morino, S Park, J Robinson, CM Roehl, Y Sawa, V Sherlock, C Sweeney, T Tanaka and MA Zondlo (2010), Calibration of the Total Carbon Column Observing Network using aircraft profile data. Atmos. Meas. Tech. Version: 1 3 (5) 1351-1362, issn: 1867-1381, ids: 673KW, doi: 10.5194/amt-3-1351-2010
  • Turnbull, JC, JB Miller, SJ Lehman, D Hurst, W Peters, PP Tans, J Southon, SA Montzka, JW Elkins, DJ Mondeel, PA Romashkin, N Elansky and A Skorokhod (2009), Spatial distribution of Delta(CO2)-C-14 across Eurasia: measurements from the TROICA-8 expedition. Atmos. Chem. Phys. Version: 1 9 (1) 175-187, issn: 1680-7316, ids: 395DO
  • Engel, A, T Mobius, H Bonisch, U Schmidt, R Heinz, I Levin, E Atlas, S Aoki, T Nakazawa, S Sugawara, F Moore, D Hurst, J Elkins, S Schauffler, A Andrews and K Boering (2009), Age of stratospheric air unchanged within uncertainties over the past 30 years. Nature Geosci. Version: 1 2 (1) 28-31, issn: 1752-0894, ids: 397CB, doi: 10.1038/NGEO388
  • Gloor, M, E Dlugokencky, C Brenninkmeijer, L Horowitz, DF Hurst, G Dutton, C Crevoisier, T Machida and P Tans (2007), Three-dimensional SF6 data and tropospheric transport simulations: Signals, modeling accuracy, and implications for inverse modeling. J. Geophys. Res.-Atmos. Version: 1 112 (D15) , Art. No. D15112, issn: 0148-0227, ids: 202JJ, doi: 10.1029/2006JD007973
  • Spackman, JR, EM Weinstock, JG Anderson, DF Hurst, HJ Jost and SM Schauffler (2007), Aircraft observations of rapid meridional transport from the tropical tropopause layer into the lowermost stratosphere: Implications for midlatitude ozone. J. Geophys. Res.-Atmos. Version: 1 112 (D12) , Art. No. D12308, issn: 0148-0227, ids: 185AG, doi: 10.1029/2006JD007618
  • Hurst, DF, JC Lin, PA Romashkin, BC Daube, C Gerbig, DM Matross, SC Wofsy, BD Hall and JW Elkins (2006), Continuing global significance of emissions of Montreal Protocol-restricted halocarbons in the United States and Canada. J. Geophys. Res.-Atmos. Version: 1 111 (D15) , Art. No. D15302, issn: 2169-897X, ids: 071JK, doi: 10.1029/2005JD006785
  • Wilmouth, DM, RM Stimpfle, JG Anderson, JW Elkins, DF Hurst, RJ Salawitch and LR Lait (2006), Evolution of inorganic chlorine partitioning in the Arctic polar vortex. J. Geophys. Res.-Atmos. Version: 1 111 (D16) , Art. No. D16308, issn: 0148-0227, ids: 078KA, doi: 10.1029/2005JD006951
  • Hurst, DF, PA Romashkin, JW Elkins, EA Oberlander, NF Elansky, IB Belikov, IG Granberg, GS Golitsyn, AM Grisenko, CAM Brenninkmeijer and PJ Crutzen (2004), Emissions of ozone-depleting substances in Russia during 2001. J. Geophys. Res.-Atmos. Version: 1 109 (D14) , Art. No. D14303, issn: 2169-897X, ids: 844VT, doi: 10.1029/2004JD004633
  • Werner, C, K Davis, P Bakwin, CX Yi, D Hurst and L Lock (2003), Regional-scale measurements of CH4 exchange from a tall tower over a mixed temperate/boreal lowland and wetland forest. Glob. Change Biol. Version: 1 9 (9) 1251-1261, issn: 1354-1013, ids: 725TJ, doi: 10.1046/j.1365-2486.2003.00670.x
  • Moore, FL, JW Elkins, EA Ray, GS Dutton, RE Dunn, DW Fahey, RJ McLaughlin, TL Thompson, PA Romashkin, DF Hurst and PR Wamsley (2003), Balloonborne in situ gas chromatograph for measurements in the troposphere and stratosphere. J. Geophys. Res.-Atmos. Version: 1 108 (D5) , Art. No. 8330, issn: 2169-897X, ids: 661KY, doi: 10.1029/2001JD000891
  • Jost, HJ, M Loewenstein, JB Greenblatt, JR Podolske, TP Bui, DF Hurst, JW Elkins, RL Herman, CR Webster, SM Schauffler, EL Atlas, PA Newman, LR Lait and SC Wofsy (2002), Mixing events revealed by anomalous tracer relationships in the Arctic vortex during winter 1999/2000. J. Geophys. Res.-Atmos. Version: 1 107 (D24) , Art. No. 4795, issn: 2169-897X, ids: 650JF, doi: 10.1029/2002JD002380
  • Drdla, K, BW Gandrud, D Baumgardner, JC Wilson, TP Bui, D Hurst, SM Schauffler, H Jost, JB Greenblatt and CR Webster (2002), Evidence for the widespread presence of liquid-phase particles during the 1999-2000 Arctic winter. J. Geophys. Res.-Atmos. Version: 1 108 (D5) , Art. No. 8318, issn: 2169-897X, ids: 650GX, doi: 10.1029/2001JD001127
  • Herman, RL, K Drdla, JR Spackman, DF Hurst, PJ Popp, CR Webster, PA Romashkin, JW Elkins, EM Weinstock, BW Gandrud, GC Toon, MR Schoeberl, H Jost, EL Atlas and TP Bui (2002), Hydration, dehydration, and the total hydrogen budget of the 1999/2000 winter Arctic stratosphere. J. Geophys. Res.-Atmos. Version: 1 108 (D5) , Art. No. 8320, issn: 2169-897X, ids: 650HB, doi: 10.1029/2001JD001257
  • Hurst, DF, SM Schauffler, JB Greenblatt, H Jost, RL Herman, JW Elkins, PA Romashkin, EL Atlas, SG Donnelly, JR Podolske, M Loewenstein, CR Webster, GJ Flesch and DC Scott (2002), Construction of a unified, high-resolution nitrous oxide data set for ER-2 flights during SOLVE. J. Geophys. Res.-Atmos. Version: 1 107 (D20) , Art. No. 8271, issn: 0747-7309, ids: 636PY, doi: 10.1029/2001JD000417
  • Gloor, M, P Bakwin, D Hurst, L Lock, R Draxler and P Tans (2001), What is the concentration footprint of a tall tower?. J. Geophys. Res.-Atmos. Version: 1 106 (D16) 17831-17840, issn: 2169-897X, ids: 465FR, doi: 10.1029/2001JD900021
  • Romashkin, PA, DF Hurst, JW Elkins, GS Dutton and PR Wamsley (1999), Effect of the tropospheric trend on the stratospheric tracer-tracer correlations: Methyl chloroform. J. Geophys. Res.-Atmos. Version: 1 104 (D21) 26643-26652, issn: 2169-897X, ids: 257KN, doi: 10.1029/1999JD900744
  • Hurst, DF, GS Dutton, PA Romashkin, PR Wamsley, FL Moore, JW Elkins, EJ Hintsa, EM Weinstock, RL Herman, EJ Moyer, DC Scott, RD May and CR Webster (1999), Closure of the total hydrogen budget of the northern extratropical lower stratosphere. J. Geophys. Res.-Atmos. Version: 1 104 (D7) 8191-8200, issn: 2169-897X, ids: 187NV, doi: 10.1029/1998JD100092
  • Novelli, PC, PM Lang, KA Masarie, DF Hurst, R Myers and JW Elkins (1999), Molecular hydrogen in the troposphere: Global distribution and budget. J. Geophys. Res.-Atmos. Version: 1 104 (D23) 30427-30444, issn: 2169-897X, ids: 268DR, doi: 10.1029/1999JD900788
  • Hintsa, EJ, EM Weinstock, JG Anderson, RD May and DF Hurst (1999), On the accuracy of in situ water vapor measurements in the troposphere and lower stratosphere with the Harvard Lyman-alpha hygrometer. J. Geophys. Res.-Atmos. Version: 1 104 (D7) 8183-8189, issn: 2169-897X, ids: 187NV, doi: 10.1029/1998JD100110
  • Hurst, DF, PS Bakwin, RC Myers and JW Elkins (1997), Behavior of trace gas mixing ratios on a very tall tower in North Carolina. J. Geophys. Res.-Atmos. Version: 1 102 (D7) 8825-8835, issn: 2169-897X, ids: WX558, doi: 10.1029/97JD00130