# Presentation: 395983

## The JPL Laser Hygrometer (JLH) in support of the NASA Aura Validation Experiment

- The JPL Laser Hygrometer (JLH) in support of the NASA Aura Validation Experiment

- Bob Herman (JPL) and Robert Troy (UCLA)
- 20 Sept. 2005
- Aura Validation Workshop

## Introduction to JLH

- Water vapor spectrometer.
- Near-infrared tunable diode laser and InGaAs detector.
- Open-path multi-pass Herriott cell
- 	(11.13-m path) mounted underneath the right wing.

## Instrument Specifications

- Detection range: 	1 to 500 ppmv
- Pressure range: 	40 to 500 hPa
- Accuracy: 		±5 to 8%
- Precision: 		±0.03 ppmv
- Time-resolution: 	1.3 sec
- Mass: 		13 kg
- Power: 		100 W (typ)
- Voltage: 		28 V DC
- What is new for JLH in 2005:
- Pressure and Temperature (in progress),
- Dedicated power supply for laser,
- Additional heaters and insulation,
- Purged electronics box.

## JLH participation in field missions

## Recent missions during Aura timeframe

| Mission | Dates | JLH data available for: | Focus |
| --- | --- | --- | --- |
| Pre-AVE | Jan-Feb 2004 | 6 flights | TTL (e.g. Jensen et al., 2004) |
| MidCiX | Apr-May 2004 | 7 flights | Mid-lat continental cirrus |
| PUMA-A | May 2004 | 3 flights | Atlas II rocket plume |
| Houston AVE | Oct-Nov 2004 | 9 flights | UT / LS water vapor, Aura validation |
| Houston AVE II | June 2005 | 9 flights | UT / LS water vapor, Aura validation |
| Water Isotope | July 2005 | 4 flights | UT / LS water vapor and cirrus clouds |
| PUMA (STS) | July 2005 | 6 flights | Space Shuttle plume |

## JLH water in support of AVE

- _Validation Goal:_  To provide water vapor measurements along the aircraft path (both level flight and spirals) for validation of TES, MLS, and HIRDLS on the EOS Aura satellite.
- _Science Goals:_  Characterize UT/LS water vapor, particularly small-scale variability, and relative humidity in and out of ice clouds.
- _Data Products in JW espoarchive file:_
- Water Vapor volume mixing ratio (ppmv),
- Frostpoint Temperature (°C),
- Relative Humidity over Ice (calculated using static   	temperature from the MMS or NOAA PT instruments).

## AVE - 31 Oct 2004 (coastal)

- Water vapor is highly variable over tens of km:

- Ozonesonde water measurements by Gary Morris (Vaisala RS80)

## AVE - 31 Oct 2004 (over ocean)

- This WB-57 spiral over the Gulf of Mexico is the closest spatial match to a TES Step and Stare point (within 18 km).
- Good comparison with TES over a limited range of altitudes.

## AVE - 5 Nov 2004 (coastal)

- WB-57 takeoff within 146-km proximity of TES Step and Stare point.

## Houston AVE - water statistics

## Water Isotope Intercomparison

- JLH recorded water vapor over a very wide range.
- Relative humidities inside clouds: important for supersaturation studies.
- Focus areas: cirrus clouds, wave clouds, contrails, and rocket plumes.

## JLH lab calibrations

- _New source of water/air mixture:_  Thunder Scientific 3900 low humidity generator (a JPL facility instrument).
- This system saturates dry (ultra-zero) air at one P,T and expands the flow to the test P,T. Technique originally developed at NIST.
- P,T are varied automatically to provide desired mixing ratio of water.
- Stability = ±0.3% at 300 ppmv.

## JLH lab calibrations

- _Reference Instruments:_  Vaisala SAW hygrometer and a General Eastern chilled-mirror hygrometer.
- _Calibration method:_  Flow through JLH Herriott Cell over a range of pressures and mixing ratios.
- _Calibration range:_ The humidity generator has been used over the 100-400 ppmv range.  Prior to Costa Rica AVE, we expect to achieve stratospheric mixing ratios (3-5 ppmv) in the laboratory.
- _Current status:_  July 2005 WIIF data have been reprocessed over 100-400 ppmv range only.

## P and T sensitivity

- Errors in P and T are unlikely to be significant sources of systematic error in JLH water mixing ratios.

- Relative humidity, on the other hand, is very sensitive to T.

## Summary

-  JLH has provided water vapor measurements during Pre-AVE, Houston AVE (Oct. 2004), Houston AVE 2 (June 2005), and other recent WB-57 missions.
-  These measurements compare favorably with tropospheric data from AIRS, TES, and sondes.
-  Improved calibrations with a low-humidity generator will impact JLH measurements from 2004 on.
-  We continue to examine calibration, pressure, and temperature.

## Acknowledgments

- 	Thanks to Michael Kurylo, Hal Maring, and Donald Anderson of the NASA Atmospheric Chemistry focus for supporting this research.  Thanks to the WB-57 support staff at Ellington Field, NASA Johnson Space Center.
- 	Part of the research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).

## (modeled by Bill Engblom, NASA Lewis)

## (modeled by Bill Engblom, NASA Lewis)

## (modeled by Bill Engblom, NASA Lewis)