Intercomparisons with the Harvard in situ water vapor instrument in the tropics during Pre-AVE and earlier aircraft campaigns: Implications for the seasonal cycle of stratospheric water vapor and Aura validation
E. M. Weinstock, J. V. Pittman, D.S. Sayres, J. B. Smith, J. R. Spackman, S. S. Leroy, J. G. Anderson and S. C. Wofsy Harvard University
Differences between measurements designed to be close in space and time (Rosenlof, 2003)
before flight date HALOE
120 40
CMDL FP
120
tropopause
40
Aircraft/Balloon/Satellite comparison, Pre-AVE, Galapagos, 2004
364
(a) Mixing from northern hemisphere
carbon dioxide (ppmv)
362
360
358
356 364
951105 960213 960801 960808 961211 970923 (carbon dioxide boundary condition) (b) Mixing from southern hemisphere
(water vapor saturation mixing ratios)
carbon dioxide (ppmv)
362
360
358
356 1995
951105 960213 960801 960808 961211 970923 (carbon dioxide boundary condition)
1996 1997 1998 date airmass crossed the 390 K isentrope
Constraints on the seasonal cycle of stratospheric water vapor using in situ measurements from the ER-2 and a CO photochemical clock
How do we resolve the differences exhibited by water vapor instruments?
1. More intercomparisons followed by organized laboratory intercomparisons and validation with full PI participation.
2. Independent evaluation of instrument performance and accuracy. 3. A national calibration facility under independent oversight.
Illustration of the implications of Pre-AVE intercomparison data on the corresponding tropopause temperatures.
Calibration source tied to vapor pressure of water at room temperature
Source of H2O
unperturbed
H2O Detection axis
Ambient air
Laboratory calibration
Less than 5%
<2 <5
<1
Calibration in flight
Uncertainties in water vapor measurement