Mark A. Zondlo (Southwest Sciences) Fred L. Eisele, Christopher A. Cantrell, Ed Kosciuch, R. Lee Mauldin (NCAR ACD) Yuzo Miyazaki, Makoto Koike, Yutaka Kondo (Univ. Tokyo) V. Kapustin, Anthony D. Clarke (Univ. Hawaii) Y. Lee (Brookhaven), Y. Ma, Rod

1
NSF Gulfstream-V VCSEL hygrometer in START08
Mark A. Zondlo (1) , Mark E. Paige (2), and Joel
A. Silver (2) 1-Civil and Environmental
Engineering Princeton, University 2-Southwest
Sciences, Inc.
H2O
14.9 km NSF Gulfstream-V July 30, 2007
2
VCSEL hygrometer specifications
Specifications Range 1-40,000 ppmv Accuracy
5 Precision lt3 (1 Hz) Mass 5 kg Power 10
W Unattended operation Test flights in NSF
PACDEX, HEFT 07, and HEFT 08
3
Experimental VCSEL hygrometer
1. Vertical cavity surface emitting
laser (VCSEL) near 1854 nm 2. Wavelength
modulation spectroscopy (250 kHz) 3. Fiber
optic system 4. Digital signal processing
microchips 5. External, open-path design
29 cm
4
Near-IR water spectroscopy
Paige, 2005
? 1854 nm 1.5 ? stronger than 1370 nm, 100 ?
stronger than 944 nm
5
Vertical cavity surface emitting laser (VCSEL)
relatively new devices at 1854 nm
(Vertilas) consume very low power (15 mW)
large current tuning range probe multiple bands
with one laser) probe stronger absorption
band than existing TDL systems (sufficient
sensitivity for tropopause measurements)
6
Other design attributes
open path cell minimizes sampling
issues 1.9 cm diameter, Au-coated
mirrors, 14.95 cm apart, 25 passes 3.74 m
pathlength wavelength modulation spectros.
- full spectral fit - 250 kHz modulation
- modulation ampl. Adjusted to P, T fiber
optic (no purging) - calibrate at T, P, mixing
ratios
input (fiber)
Temp.
Press.
output (detector)
7
Lab experiments 1 ppmv, -79.0C f.p.
2 hr. drift is ltlt 1 Hz data
slopes -1/2
signal averaging to 500 s
Note 2 hour precision lt 1 Hz (22 hour
experiment)
25 Hz raw data, fits 1 Hz linelocking, T, P
8
HEFT 04 Overview
Except around 2300 UTC, VCSEL did well from
surface-tropopause
9
TF 04 segment at tropopause (14.9 km)

• ? 25 Hz deviation (2s) 4.3

10
VCSEL hygrometer summary
START08/Pre-HIPPO specifications 3 or less
precision (1 Hz) 5 accuracy 25 Hz
sampling Status Accuracy Intercompared at
Aqua-VIT in Oct. 2007 10 higher than
mean _at_ 5, 65, 150 ppmv (within
error) Precision In-flight precision
demonstrated HEFT-08 Refine calibrations,
spectroscopy laser control
11
7640 ppmv 0C frost point (weak line)
1 Hz 38 ppmv 0.5
12
Multilinear regression fit
? fit entire spectral peak to Voigt fit, adjust
modulation / scan width ? normalized Voigt shapes
constant vs. T,P (lt3)
13
Roles of atmospheric water vapor
standardatmosphere
14
Outline

• I. Introduction
• A. Climate
• B. Chemistry
• C. Dynamics
• II. VCSEL Hygrometer for NSF G-V
• A. Measurement challenges
• B. Experimental
• C. Flow modeling studies
• D. Flight results
• III. Laboratory studies
• A. Calibrations
• B. Precision / noise / drift
• IV. Future directions

Ackowledgements Mark E. Paige (SWS), Joel A.
Silver (SWS), Jack Fox (NCAR), Michael D. Curry
(St. Johns College), Kate Brubaker (St. Johns
College), Armin Afliche (Jülich), Martina Krämer
(Jülich), Cindy Twohy (Oregon St.), Elliot
Weinstock (Harvard), NCAR EOL aircraft/flight
crew, PACDEX Science team, NSF HAIS, NSF Atm.
Chem.