# Presentation: 209194

## Aura science team meeting, 3 October 2007

- Holger Vömel
- Cooperative Institute for Research in Environmental Sciences
- University of Colorado

**Balloon Borne Cryogenic Frostpoint Hygrometer Measurements in Support of Aura Water Vapor Validation**

## Acknowledgements

- Henry Selkirk, NASA Ames Research Center
- Jéssica Valverde Canossa, Universidad Nacional
- Werner Stolz, Instituto Meteorológico Nacional
- SOWER project:
- Fumio Hasebe, Hokkaido University
- Masatomo Fujiwara, Hokkaido University
- Masato Shiotani, Kyoto University
- S. Iwasaki, National Defense Academy, Yokosuka, Japan
- S.-Y. Ogino, JAMESTEC, Yokosuka, Japan
- J. E. Barnes, S. C. Ryan, NOAA, Mauna Loa Observatory
-  R. N. Forno, University of San Andrés, La Paz, Bolivia
- R.Kivi, E. Kyrö, Finnish Meteorological Institute,
- N. Komala , S. Saraspriya, LAPAN, IndonesiaT. Leblanc, JPL, Table Mountain Facility
- B. Morel, University of La Reunion
- W. G. Read, JPL
- D. N. Whiteman, NASA Goddard
- NASA for kind support
- MLS Team for their great instrument and data products

## Overview: Validation with version 2.2

- Individual comparison examples
- Summary by geographic region
- Correlation between CFH and MLS
- Summary

## Cryogenic Frostpoint Hygrometer (CFH)

-  Absolute measurement
-  Vertical Range: surface to ~28 km         (surface to ~25 km on ascent)
-  Uncertainty: troposphere:  > 4% MR	          stratosphere: ~ 9 %
-  Microprocessor control
-  Phase sensitive detector:       electronic sunlight filter
-  Weight: ~ 400 gr
-  Payloads carry  ECC ozone   sonde and Vaisala RS80
-  ~ 280 soundings so far

**Notes:**
A frostpoint (or dewpoint) hygrometer is based on the assumption that the ice (or dew) on the mirror is in equilibrium with the water vapor in the air flowing over the mirror. The instrument regulates the mirror temperature so that the condensate on the mirror is stable and that this condition is satisfied. A frost point hygrometer is therefore not calibrated for water vapor but for temperature with the assumption that water pressure equations are correct. 
The large improvements of the CFH over the old NOAA/CMDL hygrometer are the weight savings of nearly a factor 5 and the highly improved controller characteristics. The CFH measures water vapor from the surface to the middle stratosphere without significant gaps or degraded accuracy as was the case in the older instrument. It is currently the only small balloon borne instruments capable of this large dynamic range. 
We integrated a phase sensitive detector, which eliminates the need for baffles or other mechanical means for shielding the sensor from sun light. This dramatically reduces the potential for self contamination, in particular when going through clouds. Thus the instrument typically gets good water vapor measurements on ascent up to 25 km, in some cases up to 28 km. The instrument also works well on (large) parachute descent, and valved balloons are no longer necessary. 
The photo shows Dr. Ninong Komala from LAPAN Indonesia, who is about to launch the CFH/ECC ozone combination. 

## Sounding locations

- 47 matched soundings within 6 hours and 300 km of Aura/MLS overpass
- Campaigns:
- TCSP, July 2005
- CR-AVE, Jan/Feb 2006
- TC4, Jul/Aug 2007
- WAVES, Jul 2006, Jul 2007
- MOHAVE, Oct 2006
- SOWER, Jan 2006, Jan 2007
- Plus several other unnamed campaigns

- MLS water vapor profile version 2.2Examples

## Satellite profile

**Notes:**
Delta time = 5 hours, Delta x = 204 km

## Satellite profile

**Notes:**
Delta time = 7 hours, Delta x = 225 km

## Satellite profile

**Notes:**
Delta time = 20 min, Delta x = 161 km

- Update on MLS water vapor validation with version 2.2

## MLS Comparison: All soundings

## MLS Comparison: Equatorial

- Soundings during Dec/Jan

- Example			Difference profile

## MLS Comparison: Costa Rica 

- Soundings during Jan-Mar and Jul-Sep

- Example			Difference profile

## MLS Comparison: Mid Latitudes 

- Example			Difference profile

## MLS Comparison: Arctic 

- Example			Difference profile

- Correlations based on:
*q**i, MLS** = **α** + **β** q**i, CFH **+ **η**i*

## Correlation between MLS and CFH

**Tropics****Midlatitude****Arctic**

## Correlation parameters

- Slope β					Offset α

## Summary

- On average good agreement between CFH and Aura/MLS in stratosphere, with some bias in the upper tropopshere
- Layer average difficult to interpret in process studies
- Transition from 12 leves/decade to 6 leves/decade creates a spike
- Tropical upper troposphere (P ≥ 216 hPa): MLS wetter than CFH, but very large scatter
- Tropical lower TTL (216 hPa > P > 100 hPa): MLS drier than CFH(-17%±20%)
- Tropical tropopause (100 hPa ≥ P ≥ 82 hPa): MLS wetter than CFH (~ 10%±10%)
- Arctic upper troposphere (P ≥ 216 hPa): MLS drier than CFH (~ -40%±30%)
- MLS sensitivity is lower than CFH (about 80%), compensated by positive offset