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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
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