Water Cycle Breakout Session
Attendees: June Wang, Julie Haggerty, Tammy Weckwerth, Steve Nesbitt,Carlos Welsh, Vivek, Kathy Sharpe, Brad Small
Two objectives:
1.Identify Scientific Initiatives and Research Topics toadvance Water Cycle research;
2.Assess the ability of NSF facilities to support theseactivities: retaining, new acquisition, and newdevelopment.
1.Colorado Headwaters project:
•Focus on critical questions concerning the effect of climate change on snowprocesses in the western cordillera of North America.
•Measurement of snow depth is very important for the project.
•Currently don’t have good observations of snow pack. Radar not useful inmountains. Snotel network provides data to USGS(?).
•Need in situ snowpack measurements, including snow water equivalent.Collaborations with RAL is important.
2. Global Precipitation Measurement (GPM):
•GPM will provide global precipitation map, eventually available every 3hours over +/- 70 degrees latitude.
•Snow detection is a challenge for remote sensing techniques.
•NSF/NCAR should be involved in ground validation of GPM as in LBA, etc.G-V cloud radar could observe areas that are inaccessible to ground-basedradar. CSU also active in this area; investigating detection of mixed phaseconditions.
3. Spatial variability of precipitation:
• Need to understand scaling differences between satellite footprint andother measurements.
• Polarimetric radar bridges the spatial gap between satellite and ground-based measurements.
• Need more disdrometers, research and mobile, spaced at ~100 m.
4. Water vapor in lower troposphere:
• Need 3-dimensional moisture fields at 500 m (or less) horizontal resolutionfor mesoscale research.
• Acquisition of existing instruments and development of new instrumentsand algorithms.
• Synthesize existing data sets into a 3-d analysis (aircraft, lidar, GPS,microwave radiometer, radar retrievals).
5. Water vapor in UT/LS region:
• Characterizing UT/LS water vapor is very important (radiative,chemical and microphysical roles)
• No capability at NCAR other than G-V TDL sensors.
• Satellite observations need more validation in this region.
• Development of balloon-borne reference hygrometers in UT/LSis essential. Ground-based remote sensing techniques (lidar)would supplement the radiosonde observations.
6. Satellite validation:
NCAR has done precip validation (TRMM), but not water vapor.This could be a niche for NCAR with targeted field programsassuming we could access better water vapor instruments.
7. Process studies:
• Provide a better understanding of water cycle dynamics, improvemeasurements of surface atmosphere fluxes, improve modelparameterizations, relate to cloud physics and radiation.
• Special field projects are designed to utilize integration ofdifferent instruments and careful experimental and networkdesigns.
8. Climate policy:
• Disagreements between measurements and modeling hamperthe policy making.
• Water cycle is a key issue for adaptation to climate change.
• Water vapor isotope measurement is important for discerninghistorical water levels; need better methods for measurement ofwater vapor isotopes.
9. Hydrology: Need soil moisture, stream flow, ground watermeasurements. Such instruments are difficult to maintain in thefield.
10. Cloud ice: It is challenging because we have fewer wintermeasurements. Less validation of radar algorithms. Aircraftvalidation is limited by flight safety concerns.
Recommendations on Facility Needs
Facilities
Needs
Sciences
35 GHz, Ka, S, X band radars
Retaining
GPM
High-quality disdrometers & network
Acquisition anddevelopment
Mapping precipitation
MWR, GPS for continuous WVprofiles
Acquisition
Mesoscale & others
Scanning WV DIAL
Development
Mesoscale & others
Balloon-borne referencehygrometers for UT/LS
Development
Climate, UT/LS
UT/LS airborne microwaveradiometers
Development
UT/LS
Algorithm development (VAP &integration)
Development
All areas
Airborne cloud radar/lidar (HSRL &HCR)
Retaining (underdevelopment)
Cloud ice