# Presentation: 639916

## Comparison of the Boulder Water Vapor Record 

**With the UARS/HALOE and Aura/MLS Observations**** **
- Samuel Oltmans1, Holger Vömel2,1, and Karen Rosenlof3
- 1 NOAA Earth System Research Laboratory, Global Monitoring Division, 325 Broadway, Boulder, Colorado, 80305, USA
- 2 CIRES, University of Colorado, Boulder, Colorado 80309, USA
- 3 NOAA Earth System Research Laboratory, Chemical Sciences Division, 325 Broadway, Boulder, Colorado, 80305, USA

**Introduction**
**The completion of the HALOE observation record and the inauguration of the Aura/MLS measurements provides an opportunity to compare the long term Boulder balloon water vapor record with these two important satellite stratospheric water vapor time series. The Boulder, Colorado water vapor profile measurements obtained using cryogenic, chilled-mirror hygrometers flown on small balloons represent the longest time series of upper tropospheric and stratospheric water vapor. The HALOE water vapor measurements obtained from the UARS platform provided stratospheric water vapor measurements from 1992 through 2005. The Aura/MLS observational record began in 2004.**** ****	**

-                             ***                       ***

***                   ***

**JAN   FEB   MAR  APR   MAY  JUN   JUL   AUG   SEP  OCT  NOV  DEC **

***Figure 4 (left): Comparison of matched profiles from Aura/MLS over Boulder with soundings from the balloon chilled mirror hygrometer.***

***Figure 1: Trend with altitude of the balloon profile water vapor mixing ratio over Boulder, Colorado for the period 1980-2006. ***

**The UARS/HALOE water vapor record has ended.**
**POAM 2 and SAGE 2 water vapor records have also ended.**
**Aura/HRDLS is not likely to produce the kind of record we have seen from HALOE.**
**Aura/MLS will likely be the source of satellite upper tropospheric and stratospheric water time series for the near future.**
**Can the ground based measurements provide a link between the past and ongoing satellite observations?**
**Differences between the HALOE and Boulder records that emerged in the late 1990s have raised questions about whether the Boulder data have maintained their long-term stability.**

**Comparison of the Aura/MLS profiles over Boulder with the balloon water vapor profiles shows generally good agreement with an average difference of about 5%. There is some altitude dependence in this difference, however, with MLS a bit lower at 68 hPa and about the same percentage higher at 14.7 hPa.**

**(3)**

**Comparison of the Boulder Balloon and HALOE Time Series**
**During the first half of the HALOE record the Boulder measurements and the HALOE observations over Boulder were in good agreement in their longer-term variation.  During the latter half of the HALOE record (beginning in the late 1990s) the HALOE profiles over Boulder showed an increasing difference with the balloon profiles. This becomes most apparent after 2000 when the HALOE data show a sharper decline in the lower stratosphere than is seen in the Boulder profiles.**

***Figure 2: The 16-24 km (above) average water vapor profiles over Boulder from individual balloon measurements (******blue******) and from HALOE overpasses (******red******). The HALOE time series includes all overpasses over Boulder not just days when there was a balloon sounding. Averages in the 14-16 km and 24-26 km layers (below).***

***Figure 3 (above): Comparison of the cryogenic frostpoint hygrometer balloon water vapor profile at Boulder on June 22, 2005 with an MLS profile obtained over Boulder. The MLS vertical weighting applied to the balloon profile is also shown.***

**Comparison of Aura/MLS With the Boulder Balloon Soundings****      **

**(1)**

***Figure 5: Time series of the layer average water vapor mixing ratio in the 20-24 km layer over Boulder from HALOE, MLS, and the balloon chilled mirror hygrometer. The MLS data are only for coincident profiles with the balloon soundings.***

**Conclusions**
**The HALOE observations of the last several years show generally lower values over Boulder than the balloon-borne, NOAA chilled mirror hygrometer soundings at Boulder.**
**Earlier comparisons showed good agreement.**
**The source of this difference is not clear.**
**The balloon frostpoint measurements show good agreement with MLS observations (<5% differences in general).**
**The MLS series is not long enough to determine the agreement with the Boulder profiles over time.**
**The Boulder time series for the 1991-2006 period shows smaller changes than the overall 1980-2006 record.**

**(4)**

**(2)**

***Figure 6: Trend with altitude of the balloon profile water vapor mixing ratio over Boulder, Colorado but just for the period 1991-2006; approximately the HALOE period. ***