IBIS vs HF Observations:

When examined on a seasonal or monthly basis IBIS has systematic biases in NRG. But, seasonal biases cancel upon annual aggregation.

Annual IBIS mean annual NEE close to observed 12-yr mean NEE IBIS on average the systematically low GEE (1.4 MgC/ha/yr) balanced by systematically low R (-1.4 MgC/ha/yr)

Summer IBIS R close to observed, GEE & NEE well below observed

Spring (Apr/May): Very high GEE (~ 1MgC/ha/yr), partially offsets summer deficit. Uptake is way over predicted. Mostly May.

Winter (Nov-Mar): IBIS under predicts efflux. Nov-Mar R low by 2MgC/ha.yr on average, Dec-Mar NEE low by about1 1MgC/ha/yr

Fall (Nov-Oct): R low.

2000 – 2004 Abrupt up tick in summer R (+2.5MgC/ha/yr) and GEE (+3MgC/ha/yr). No similar jump in HF observed drivers: daily precipitation, solar, Tair, RH, Wspd.

Spring (Apr/May): Very high GEE (~ 1MgC/ha/yr), partially offsets summer deficit. Uptake is way over predicted. Mostly May.

This looks like the phenology scheme. Uptake starts too early.

Summer IBIS R close to observed, GEE & NEE well below observed IBIS GEE typically low vs. obs IBIS R consistently high in June, mixed other months

Seems to be over sensitivity to soil moisture (or soil is too dry in IBIS)For months of Jun-Aug, IBIS GEE, R errors correlate with soil moisture estimated with our simple hydrology model. Dry conditions supress GEE more than R

Winter (Nov-Mar): IBIS under predicts efflux. Nov-Mar R low by 2MgC/ha.yr on average, Dec-Mar NEE low by about1 1MgC/ha/yr

IBIS soil temperatures too low?

Heterotrophic R pretty much shuts down in Jan & Feb.

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-40

00

-30

00

-20

00

-10

00

obsM0ibis

Annual (calyr) NEE - observed, Model-0, IBIS

year

GE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-16

00

0-1

40

00

-12

00

0-1

00

00

-80

00

obsM0ibis

Annual (calyr) GEE - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

80

00

90

00

10

00

011

00

01

20

00

13

00

01

40

00

obsM0ibis

Annual (calyr) R - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

20

00

40

00

60

00

80

00

10

00

01

20

00

14

00

0

obsibisibis-Raibis-Rh

Annual (calyr) R - observed, IBIS

year

NE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

05

00

10

00

15

00

20

00

25

00

30

00

obsM0ibis

Winter (Dec-Mar) NEE - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

05

00

10

00

15

00

20

00

25

00

30

00

obsibisibis_Raibis_Rh

Winter (Dec-Mar) R - observed, IBIS

year

NE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-10

00

-50

00

50

01

00

0

obsM0ibis

Spring (Apr-May) NEE - observed, Model-0, IBIS

year

GE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-30

00

-25

00

-20

00

-15

00

-10

00

obsM0ibis

Spring (Spr-May) GEE - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

16

00

18

00

20

00

22

00

24

00

obsM0ibis

Spring (Apr-May) R - observed, Model-0, IBIS

year

NE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-70

00

-60

00

-50

00

-40

00

-30

00

-20

00

-10

00

obsM0ibis

Summer (Jun-Sep) NEE - observed, Model-0, IBIS

year

GE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-14

00

0-1

20

00

-10

00

0-8

00

0-6

00

0

obsM0ibis

Summer (Jun-Sep) GEE - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

40

00

50

00

60

00

70

00

80

00

90

00

obsM0ibis

Summer (Jun-Sep) R - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

02

00

04

00

06

00

08

00

0

obsibisibis-Raibis-Rh

Summer (Jun-Sep) R - observed, Model-0, IBIS

year

NE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

20

04

00

60

08

00

10

00

12

00

obsM0ibis

Fall (Oct-Nov) NEE - observed, Model-0, IBIS

year

GE

E [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

-12

00

-10

00

-80

0-6

00

-40

0

obsM0ibis

Fall (Oct-Nov) GEE - observed, Model-0, IBIS

year

R [

kgC

/ha

/mo

nth

]

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

50

01

00

01

50

02

00

02

50

0

obsM0ibis

Fall (Oct-Nov) R - observed, Model-0, IBIS

month

NE

E [

kgC

/ha

/mo

nth

]

jul92 jul94 jul96 jul98 jul00 jul02

-20

00

-15

00

-10

00

-50

00

50

01

00

0Monthly NEE - observed, IBIS

observed

month

GE

E [

kgC

/ha

/mo

nth

]

jul92 jul94 jul96 jul98 jul00 jul02

-40

00

-30

00

-20

00

-10

00

0Monthly GEE - observed, IBIS

observed

month

R [

kgC

/ha

/mo

nth

]

jul92 jul94 jul96 jul98 jul00 jul02

05

00

10

00

15

00

20

00

25

00

Monthly R - observed, IBIS

IBIS

deep layer soil moisture [%max]

IBIS

GE

E e

rro

r

0.4 0.5 0.6 0.7 0.8 0.9 1.0

-50

00

50

01

00

01

50

02

00

0IBIS monthly GEE error (Jun-Aug) vs. Soil Hydrology Model

R2 = 0.49

deep layer soil moisture [%max]

IBIS

R e

rro

r

0.4 0.5 0.6 0.7 0.8 0.9 1.0

-50

00

50

0IBIS monthly R error (Jun-Aug) vs. Soil Hydrology Model

R2 = 0.39