Title: STAR-Light: Enabling a New Vision for Land Surface Hydrology in the Arctic A. W. England and Roger De Roo Atmospheric, Oceanic, and Space Sciences Electrical Engineering and Computer Science The University of Michigan
1STAR-Light Enabling a New Vision for Land
Surface Hydrology in the ArcticA. W. England and
Roger De RooAtmospheric, Oceanic, and Space
SciencesElectrical Engineering and Computer
ScienceThe University of Michigan
- Abstract
- STAR-Light, a 1.4 GHz radiometer for use on light
aircraft, is an enabling instrument for
monitoring thickness and water content of the
active layer throughout the circumpolar Arctic.
Our underlying vision is that the active layer
can be modeled with a Soil-Vegetation-Atmosphere
Transfer (SVAT) model that is forced by available
data on weather and downwelling radiation.
Through near-daily assimilation of satellite
observations of microwave brightness at a
frequency that is sensitive to liquid water in
the upper few centimeters of soil, these SVAT
models will maintain reliable spatial estimates
of the thickness and water content of the active
layer. - Key for this vision are accurate SVAT models for
Arctic terrains, an airborne radiometer for the
extensive field observations necessary to
calibrate these models, and a satellite
radiometer to provide near-daily observations.
SVAT/Radiobrightness models for Arctic tundra are
in the early stages of development. The
hydrology community has converged upon 1.4 GHz
brightness as the most effective observation for
sensing soil moisture, and the European Space
Agency is completing a preliminary study of a 1.4
GHz Soil Moisture Ocean Salinity (SMOS) satellite
mission for later this decade. STAR-Light is an
NSF-funded, airborne instrument for SVAT model
calibration in the Arctic beginning in 2004. - We will describe our progress with the STAR-Light
development, and describe how others can
participate in this research.
- We are developing and will calibrate the
SVAT/Radiobrightness model - for tussock tundra near Toolik Lake. We seek
collaborators to - Develop calibrate SVAT/Radiobrightness models
for other Arctic terrains - Develop calibrate 2-D land-surface
hydrology/radiobrightness models - Field test models in relevant Arctic terrains
Observational Scales and Deployment Timeline
Background
- 1) Stored water is an important unmeasured
parameter limiting the predictive skills of
continental weather and climate models - Desire to estimate stored water, on a near-daily
basis, globally, and at 10 km resolution - Climate models predict early significant
warming in the Arctic - Observed warming of permafrost
- Concern about transition of Arctic from carbon
sink to carbon source - Desire to monitor evolution of active layer
throughout Arctic - Seasonal duration
- Water content
- Access to Arctic tundra is limited in summer
- Desire for supporting land surface hydrology
observations from airborne and satellite sensors
Operational Strategy for Estimating Stored Water
Satellite L-band Radiometer (University of
Michigan research area)
Atmospheric Model
Calibrated Soil-Vegetation-Atmosphere-Transfer
(SVAT) Model (University of Michigan research
area)
Assimilate Tb(observed) - Tb(model)
- Objective
- Design and fabricate a reliable L-band imaging
radiometer for use on light aircraft in Arctic
land-surface hydrology - Strategy
- Use Synthetic Thinned Aperture Radiometer (STAR)
technology for compactness - Use Direct Sampling Digital Receivers (DSDR) for
reliability and compactness - Use Digital Signal Processing technology for
uniform band definition - These technologies move complexity from analog
domain to digital domain and achieve compactness,
reliability, and flexibility
Radiobrightness Model (University of Michigan
research area)
Estimates of stored water from SVAT models
running in open loop (blue arrows) diverge from
reality over time (due to imperfect weather data,
poor estimates of runoff, etc.) Closed loop
(yellow arrows) estimates of stored water use
remotely sensed radiobrightness data to
quantify surface soil moisture and thereby
correct model and data imperfections over time.
Calibrating SVAT Models with Season-long
Observations
STAR-Light Control Module
Airborne L-band Radiometer and Truck
Multi-frequency Radiometers
Micromet Tower and buried sensors
SVAT Radiobrightness Models
STAR-Light Sensor Module
Refinements
Refinements
A 1.4 GHz radiometer on a light aircraft would
greatly facilitate remote sensing hydrology in
the Arctic
- Development/calibration of SVAT/radiobrightness
models of Arctic tundra require observations from
thawing in spring to freezing in fall - NASA radiometers used for hydrology are designed
to fly on large, 4-engine, turboprop aircraft
like the C-130 and P-3 - High operations costs and scheduling conflicts
prohibit use of these aircraft in field campaigns
of more than a few weeks - Operations costs of STAR-Light will be lt 5 those
of NASA systems and the aircraft will be
dedicated to STAR-Light enabling season-long
field campaigns
SVAT/Radiobrightness Model Frequencies (GHz) Status Availability Sponsor
Prairie Grasslands 19, 37, 85 Calibrated Now NASA Hydrology
Row Crops (corn) 1.4 Calibrated mid 2002 NASA Hydrology
Tussock Tundra 19, 37, 85 Preliminary Now NSF LAII
Meadow with Snowpack 1.4, 6.9, 19, 37 Funded 2004 NASA CLPX GWEC
Tussock Tundra 1.4, 6.9, 19, 37 Funded 2005 NASA GWEC
This work is supported by NSF grant OPP-0085176
from the Office of Polar Programs