Use of MODIS False Color to Monitor Snowfall, Snow melt and Thermal Belts
description
Transcript of Use of MODIS False Color to Monitor Snowfall, Snow melt and Thermal Belts
Use of MODIS False Color to Monitor Snowfall, Snow melt and Thermal
BeltsGina Loss – Service Hydrologist
Dave Bernhardt – Science & Operations Officer
Great Falls, Montana
Why MODIS to monitor snow and river ice?Montana is rural with a low population densityRemote sensing best to appropriately
determine the transition of snow cover and river ice in remote areas,Problem - Visible imagery does not clearly
differentiate snow from clouds.MODIS false color composite does differentiate
snow from cloudsResult is improved assessments of flooding
potential with rapid melt and runoff
MODIS False Color CompositeComposites one visible and two infrared
channels Highlights features with infrared signature
differencesSnow and clouds have reflective differences
above 1.4μmEspecially near the 1.6μm and 2.13μm MODIS
channelsCompositing a visible channel with these two
infrared channels creates an image that distinguishes snow and clouds
Comparison to Other Satellites
MODIS
AVHRR GOES
Spatial Resolution (meters) 500 1000 1000
Channels used to produce snow products
7 3 1 broadband
Images per day 1-2 3-6 20
Comparison to Other SatellitesMontana at a relatively high latitude and at
edges of both GOES East and WestRemapping of data results in a north-south and
east-west blurring of detailsGOES imagery can be looped to show
stationary snow features vs. moving cloudsStill issues with semi-stationary clouds
Fog Lenticular formations Orographically induced stratus
Assessment Samples
SnowCloud
sBare
Ground
Cirrus
Snow inForest
Clouds Snow
SnowCloud
sBare
Ground
Cirrus
Snow inForest
Clouds Snow
SnowCloud
sBare
Ground
Cirrus
Snow inForest
Clouds Snow
Visible Image Natural Color Image
False Color Image
River Ice Monitoring Samples
Bow-tieEffect Lake
Ice
Valley Fog
River Ice
Snow
Snow
Snow in Forests
Snow in Forests
River andLake Ice
RottingLake Ice
Bare Ground
Clouds
Snow in Forests
Snow in Forests
Rotting River andLake Ice Clouds
February 21, 2008 April 12, 2008
2004 Case AssessmentFebruary 19, 2004
Missouri
River
Milk River
Poplar River
2004 Case Assessment March 4, 2004
Missouri
River
Milk RiverPoplar River
2004 Case AssessmentMarch 11, 2004
Missouri
River
Milk River
Poplar River
2004 Case AssessmentMarch 18, 2004
Missouri
River
Milk River
Poplar River
2004 Case AssessmentMarch 25, 2004
Missouri
River
Milk River
Poplar River
Assessment of Flooding Potential
Co-op Observations
NOHRSC Model Snow DepthMonitor change
in snow cover and snow water
equivalent
Monitor change in
stream flow
NOHRSC Aerial Survey NOHRSC Flight
Lines
Satellite Imagery
NOHRSC Modeled Snow Melt
Satellite Imagery
Benefitsprovided by
MODISFalse Color
Imagery
Snow event
Inform emergency
management
NOHRSC Model Snow Water
Equivalent
USGS Streamflow
NWS Streamflow and Forecast
Facilitates monitoring 2-D change of snow cover
Illustrates stream
flow/snowmelt relationship
Faster and more
convenient
Corroborates NOHRSC snow
model products
Saves human resources and
increases safety
Provides easily
understood briefing tool
Examine snow cover
Request survey
of remote areas
SNOTEL Reports
Examine NOHRSC products
Findings - AdvantagesComplete overview of snow cover extent
High spatial and spectral resolution Information for areas void of surface data Indicates primary areas of concern when complemented with
supplemental data from ground measurements Often eliminates need for field surveys during potentially dangerous
situationsObservation of snow cover transition
Speed and extent of snowmelt provide insight to areas with possible flooding concerns
View of ice on rivers and lakes Ice formation and degradation provide insight on locations of possible
ice jams and related floodingCorroborates information provided by NOHRSC (National
Operational Hydrologic Remote Sensing Center) snow models
Findings – DisadvantagesCloud cover blocks view of surface
Visible and infrared spectrumsSignificant snowfall/snowmelt can occur under cloud
cover and full extent may not be viewable for daysImages per day limited
Polar-orbiting satellite provides only a few images daily
‘Bow-tie’ effect blurs imagesSatellite field of view overlap produces data
repetition at image edgeAlgorithm to remove this effect will be available soon
Fire ThreatsFires always a concern
to NWS forecastersNumerous specialized
forecasts provided for data sparse locations to support wildfire suppressionNeed all possible
observations – including satellite
Topography Western Montana
Bitte
rroo
t Val
ley
Bitte
rroo
t Mou
ntai
ns
Sapp
hire
Mou
ntai
ns
MODIS 3.7 micron 0930 UTC 30Aug2007
Warm Mountain
Cool Valley
Even Warmer Slopes
04 Jul 2007 Felix wildfire near the top of Bridger Range, northeast of Bozeman, MT
MODIS IR and AWIPS Topography
Felix Wildfire
Pronounced thermal belt west slopes
MODIS Derived hot spots depicted in google earth