Developing combined Developing combined phenological indices for phenological indices for

reducing uncertainty in the reducing uncertainty in the magnitude and interannual magnitude and interannual variation of carbon, water variation of carbon, water and energy fluxes in mid-and energy fluxes in mid-

latitude forests latitude forests

PIs:PIs: Noormets, Chen, Schwartz Noormets, Chen, SchwartzCollaborators:Collaborators: DeForest (SR), Reed (RS), DeForest (SR), Reed (RS), Flux & Phenology data sharing (7 flux Flux & Phenology data sharing (7 flux sites)sites)

OverviewOverview

►ProblemProblem►What can be done to solve itWhat can be done to solve it►Expected obstaclesExpected obstacles►Specific tasksSpecific tasks►SignificanceSignificance

Problem (1)Problem (1)

Sources of uncertaintySources of uncertaintyA.A. AreaArea

1.1. DisturbanceDisturbance2.2. Land use changeLand use change

B.B. Sink strengthSink strength1.1. Regulation Regulation 2.2. GSLGSL

When does GS start? When does GS start? for GPP - for ER - for SRfor GPP - for ER - for SR

Problem (2)Problem (2)

►MODIS phenology products MODIS phenology products notnot validatedvalidated

►Compositing over 8 and 16 daysCompositing over 8 and 16 days

0

0.1

0.2

0.3

0.4

0.5

0.6

1-Jan 1-Mar 1-May 1-Jul 1-Sep 1-Nov 1-Jan

ND

VI

How to define SOS?How to define SOS?

Seasonal midpoint NDVIMaximum increaseDelayed moving averageInflection point

Reed et al., 2003, Phenology

0

200

400

600

0

200

400

600

SR

(µm

ol C

O2 m

-2 s

-1)

0 5 10 15 20 25

Ts5 (°C)

0

100

200

300

Dormant

Ac tive

Open canopy

Closed canopy

May, 2004

J ul, 2004

Sep, 2004

(early )

Sep, 2004

(late)Oc t, 2004

(before leaf drop)

Oc t, 2004

(leaf drop)Apr, 2005

J an, 2005

When does GS When does GS start?start?

What causes the transition?What causes the transition?

Suni et al., 2003, JGR

We propose:We propose:

►Detect phenological transition in fluxes Detect phenological transition in fluxes GPPGPP ERER SR SR

►Seek concomitant signals in Seek concomitant signals in VI-s (NDVI, EVI)VI-s (NDVI, EVI) surface water (LSWI)surface water (LSWI) snow (NDSI, MOD10A1)snow (NDSI, MOD10A1)

AR = ER - SR

Special requirementsSpecial requirements

►High temporal resolutionHigh temporal resolution historical data from flux sites with historical data from flux sites with

phenological observations phenological observations couple with couple with MODIS dataMODIS data

►High spatial resolutionHigh spatial resolution Chequamegon, existing flux towers. Up to Chequamegon, existing flux towers. Up to

10 days difference in transition of 10 days difference in transition of . .

ObstaclesObstacles

► Cover-type specificityCover-type specificity re-classify MOD12 at local scalere-classify MOD12 at local scale validate against Landsat land cover & age mapsvalidate against Landsat land cover & age maps

► Daily frequencyDaily frequency 50-55% sunny50-55% sunny transitions occur during warm & clear periodstransitions occur during warm & clear periods

► Spatial continuitySpatial continuity express fluxes in terms of SI-sexpress fluxes in terms of SI-s SI-s linear between 275 and 282 K (annual TSI-s linear between 275 and 282 K (annual Tmeanmean))

Tasks (1) – collect existing Tasks (1) – collect existing datadata►Flux, MODIS & phenology data for Flux, MODIS & phenology data for

different flux sitesdifferent flux sites

►MODIS products that are available at MODIS products that are available at daily time step: MOD09daily time step: MOD09reflrefl, MOD10, MOD10snowsnow, ,

MOD11MOD11ttºº

Tasks (2) – re-processingTasks (2) – re-processing

►Optimize MOD12 for detecting Optimize MOD12 for detecting composition and age differences composition and age differences identified from Landsatidentified from Landsat

►Recalculate MODIS products at daily Recalculate MODIS products at daily interval if not available - LSWI, interval if not available - LSWI, MOD43MOD43AlbedoAlbedo, , MOD15MOD15LAILAI, , MOD13MOD13VIVI

Tasks (3) – timing of Tasks (3) – timing of transitiontransition► Identify SOS for individual fluxesIdentify SOS for individual fluxes

►Analyze the time course of MODIS Analyze the time course of MODIS products for signatures indicating the products for signatures indicating the SOS. Develop CPI. SOS. Develop CPI.

Tasks (4) – spatial resolutionTasks (4) – spatial resolution

►Within a landscape, patches differWithin a landscape, patches differ

►How small units can the CPI resolve?How small units can the CPI resolve?

►Depends on the need for coarser Depends on the need for coarser resolution products – land cover, resolution products – land cover, temperature, LAI & FPARtemperature, LAI & FPAR

Tasks (5) – spatial continuityTasks (5) – spatial continuity

►Calculate spring indices (SI) for Calculate spring indices (SI) for indicator species – cloned lilac & indicator species – cloned lilac & honeysuckle throughout NE UShoneysuckle throughout NE US

►Evaluate the relationship between Evaluate the relationship between developed CPI and SIdeveloped CPI and SI

SignificanceSignificance

►Reduce uncertainties of interannual Reduce uncertainties of interannual variability in C flux estimatesvariability in C flux estimates

►Reduce dependence of biogeochemical Reduce dependence of biogeochemical models on ground-based and generic models on ground-based and generic observations of phenological change observations of phenological change