IMPLICATIONS OF THE NRC DECADAL REVIEW FOR INTERNATIONAL

HYDROLOGYDennis P. Lettenmaier

Department of Civil and Environmental EngineeringUniversity of Washington

for presentation at

AGU Fall MeetingSpecial Session

U.S. Contributions to International Hydrology

December 10, 2007

Decadal Review Charge

•Recommend a prioritized list of flight missions and supporting activities to support national needs for research and monitoring of the dynamic Earth system during the next decade.

•Identify important directions that should influence planning for the decade beyond.

Sponsors: NASA SMD, NOAA NESDIS, USGS Geography

Water Panel top 7 missions

1) Soil Moisture SMAP

2) Surface water/coastal oceanography (swath altimetry+) SWOT

3) Cold land processes SCLP

4) Groundwater/ocean mass (GRACE+)5) Water vapor transport (WOWS/AIRS+)6) Glacier mass balance/sea ice thickness7) Inland water quality

And … a strong endorsement of Global Precipitation Measurement (GPM)

• “Precipitation arguably is the most important part of the global water cycle. It dominates the land surface branch of the water cycle, and is second only to evaporation over the oceans … “

• The approved GPM mission was highest ranked by the water cycle panel

Bias in satellite precipitation estimates (no in situ adjustment) over La Plata basin, 2003-2005

The bias significantly decreased at the year 2005 over basins 3802 and 6598 for the three real-time satellite precipitation products.

For details: Su et al (H32A07)

Recent Results: NWP Skill

Sutton et al. (2007): Will Perturbing Soil Moisture Improve Warm-Season Ensemble Forecasts? A Proof of Concept, Monthly Weather Review, 134, 3174-3189.

“…changes to 5-km forecasts due to soil moisture differences were almost as large as the changes to 20-km forecasts due to using an alternate convective parameterization, previously determined to be a large source of uncertainty in ensemble forecasts…”

“…The results presented here suggest that short-term temperature and precipitation forecasts can indeed be changed as a consequence of changing the soil moisture…”

NOAA-FSL and NCAR Study

SMAP Flood and Drought ApplicationsSMAP Primary Science Objective

“…delivery of flash-flood guidance to weather forecast offices are centrally dependent on the availability of soil moisture estimates and observations.”

“SMAP will provide realistic and reliable soil moisture observations that will potentially open a new era in drought monitoring and decision-support.”

Decadal Survey:

Current: Empirical Soil Moisture Indices Based on Rainfall and Air Temperature ( By Counties or ~30 km )

Future: SMAP Soil Moisture Observations at 10 km

Current NWS Operational Flash Flood Guidance (FFG)

Current Operational Drought Indices by NOAA and National Drought Mitigation Center (NDMC)

Swath altimetry would “see” most global rivers and lakes, and would be able to recover useful altimetric information for surface areas > ~ 1 km2

Rivers and flood plains: a spatial view

Global lake and reservoir storage: beyond the largest ~100s – 1000s

Channel Discharge Estimation Error using synthetic SWOT observations and EnKF

• Spatially averaged RMSE of channel discharge

• Open-loop RMSE = 161.5 m3/s (23.2%)

• Filter RMSE = 76.3 m3/s (10.0%)

Apr 1 Apr 15 May 1 May 15 Jun 1 Jun 150

100

200

300

400

500

600

RM

SE (

m3/s

)

Details: Andreadis et al, GRL, 2007

15June 28, 2007

Runoff Dominated by Water from Snowmelt• Over much of the industrialized world (1/6 of world’s population), 50-

100% of runoff results from snowmelt1, affecting about a quarter of the global gross domestic product.

• Scientists, managers and planners need to know how much water is in the snowpack.2

1Barnett et al, Nature (17), Nov 20052Anthes et al, p 4-393Anthes et al, p 4-38

• Understanding the dynamics of water storage in seasonal snowpacks is critical to the effective management of water resources both within the U.S. and globally.3

Annual Accumulated Snowfall

Annual Runoff

Runoff Dominated by Snow1

Snow Water Equivalent (SWE)

Red outline: Snowmelt dominated and lacks sufficient storage capacity to buffer shifts in seasonal hydrograph.

NRC Decadal Survey Societal Challenge: Freshwater AvailabilityNRC Decadal Survey Societal Challenge: Freshwater Availability

16June 28, 2007

Large Uncertainty of Current Snow Measurements Comparing in situ + airborne Estimate to Satellite

NSA < AMSR

SWE(cm)

NSA > AMSR

Neutral

- 200- 150- 100- 50- 45- 40- 35- 30- 25- 20- 15- 10- 8- 6- 4- 20+ 2+ 4+ 6+ 8+ 10+ 15+ 20

NOAA National Snow Analysis (NSA)

Total Volume of Water Stored, U.S. 258 km3 (11% AIRWR)

Total Volume of Water Stored, U.S. 258 km3 (11% AIRWR)

SWE (cm) 0.01 0.1 0.5 1 2.5 5 10 15 25 50 75 100 2000

February 10, 2004

(AMSR SWE) - (NOAA NSA SWE)

Total Difference in Volume of Water Stored, U.S. -113 km3 (5% AIRWR)

Total Difference in Volume of Water Stored, U.S. -113 km3 (5% AIRWR)

Preliminary information from “The Value of Snow and Snow Information Services” – Office of the Chief Economist (NOAA, 2004):“..improved snow information and services have potential benefits greater than $1.3 billion annually.” “…investments that make only modest improvements in snow information will have substantial economic payoffs.”

NRC Decadal Survey Societal Challenge: Freshwater AvailabilityNRC Decadal Survey Societal Challenge: Freshwater Availability

Annual Internal Renewable Water Resources (AIRWR) are average fresh water resources available over a year from precipitation falling within a country’s borders (Gleick et al., 1993).( )

17June 28, 2007

Segal et al. (1992)

Snow • Snow accumulation impacts the sensible heat flow for clear skies, and provides positive feedback on the cloud formation and snow melt.

• SCLP will provide high resolution mapping of snow accumulation for improved surface parameterization for land-atmosphere interactions in mid and high latitudes during the winter-spring transitions, with implications for mesoscale hydrometeorology, terrestrial hydrology and carbon budgets.

Horizontal wind speed gradient

Shifting wind direction across the boundary

Lower potential temperature

Higher potential temperature

Lower sensible heat flux

Higher sensible heat flux

No Snow

Clear Sky Conditions

NRC Decadal Survey Societal Challenge: Improved Weather PredictionNRC Decadal Survey Societal Challenge: Improved Weather Prediction

Science Example: Snow Cover Impacts Mesoscale Hydrometeorology

What are the implications for the U.S. and International Hydrology?

• Global vs International Hydrology

• Each of the four missions would have a large impact on hydrological sciences, and taken together would fundamentally change the field

• The storm cloud on the horizon: NASA earth science funding

• Can these missions go forward without international cooperation (something the U.S. doesn’t always do very well)?

• And can we convince prospective international partners to adopt a policy of free and open data exchange (which the U.S. generally does better)?