LAI.DOC
1. TITLE
1.1 Data Set Identification
Total Leaf Area Index (LAI)
LAI (Monthly ; NASA/GSFC)
1.2 Data Base Table Name.
Not applicable.
1.3 CD-ROM File Name.
\DATA\VEGETATN\LAI\YyyMmm.sfx
Note: capital letters indicate fixed values that appear on the CD-ROM
exactly as shown here, lower case indicates characters (values) that
change for each path and file.
The format used for the filenames is: YyyMmm.sfx, where yy is the last
two digits of the year (e.g., Y87=1987), and mm is the month of the year
(e.g., M12=December). The filename extension (.sfx), identifies the data
set content for the file (see Section 8.2) and is equal to .LAI for this
data set.
1.4 Revision Date Of This Document.
April 5, 1995.
2. INVESTIGATOR(S)
2.1 Investigator(s) Name And Title.
Sietse O. Los, Piers J. Sellers
Biospheric Sciences Branch
NASA Goddard Space Flight Center
2.2 Title Of Investigation.
Earth Observing System - Inter Disciplinary Science
project (Sellers - Mooney)
2.3 Contacts (For Data Production Information).
________________________________________________
| Contact 1 |
______________|_________________________________|
2.3.1 Name |Sietse O. Los |
2.3.2 Address |Biospheric Sciences Branch |
|code 923 |
|NASA Goddard Space Flight Center |
City/St.|Greenbelt MD |
Zip Code|20771 |
2.3.3 Fax |(301) 286-1757 |
2.3.4 Email |Sietse@Jello.gsfc.nasa.gov |
______________|_________________________________|
NOTE: Providing information on these data is not part of my daily routine;
Please read literature and descriptions first. Allow for some delay in
my response.
**********************************************************
* FOR GENERAL QUESTIONS REGARDING THE DATA CONTACT THE *
* GODDARD DAAC (SEE SECTION 13). *
**********************************************************
2.4. Requested Form of Acknowledgment.
Please cite the following publications when ever these data are used:
Sellers, P.J., S.O. Los, C.J. Tucker, C.O. Justice, D.A. Dazlich, G.J.
Collatz, and D.A. Randall, 1994. A global 1 by 1 degree NDVI data set
for climate studies. Part 2: The generation of global fields of
terrestrial biophysical parameters from the NDVI. International
Journal of Remote Sensing, 15(17):3519-3545.
Sellers, P.J., S.O. Los, C.J. Tucker, C.O. Justice, D.A. Dazlich, G.J.
Collatz, and D.A. Randall, 1995. A revised land surface
parameterization (SiB2) for atmospheric GCMs. Part 2: The generation
of global fields of terrestrial biophysical parameters from satellite
data. Submitted to Journal of Climate.
ACKNOWLEDGMENTS
This research was funded by the NASA Earth Observing System Inter
disciplinary science (EOS-IDS) program, Sellers-Mooney team
3. INTRODUCTION
3.1 Objective/Purpose
The 1 X 1 degree leaf area index (LAI) global data set was compiled for
use within the simple biosphere model (SiB2, see Sellers et al., 1994,
1995), to calculate the energy and water exchange between the biosphere
and atmosphere. With the SiB calculations the effect of vegetation on
climate can be incorporated in a General Circulation Model (GCM) of the
atmosphere.
3.2 Summary of Parameters.
LAI: Total (life and dead) one-sided Leaf Area
Index (ratio between leaf area and ground surface)
3.3 Discussion.
Not available at this revision.
4. THEORY OF MEASUREMENTS
The FPAR - LAI relationship is assumed exponential for vegetation evenly
distributed over a surface (Monteith, 1973) and linear for vegetation
concentrated in clusters (Huemmrich and Goward, 1992), likely to occur in
classes 4, 5, and 9, see the documentation on vegetation classification in
VEG_CLSS.DOC section 8 and Defries and Townshend (1994). We tied the
relationship between FPAR and LAI to these two points, an FPAR of 0.95 is
equivalent to the maximum LAI for a particular class, an FPAR of 0.001 is
equivalent to a minimum LAI. The minimum and maximum LAI values are presented
in the table in section 9.
5. EQUIPMENT
5.1 Instrument Description.
See the NDVI document.
5.1.1 Platform (Satellite, Aircraft, Ground, Person...).
See the NDVI document.
5.1.2 Mission Objectives.
See the NDVI document.
5.1.3 Key Variables.
See the NDVI document.
5.1.4 Principles of Operation.
See the NDVI document.
5.1.5 Instrument Measurement Geometry.
See the NDVI document.
5.1.6 Manufacturer of Instrument.
See the NDVI document.
5.2 Calibration.
See the NDVI document.
5.2.1 Specifications.
See the NDVI document.
5.2.1.1 Tolerance.
See the NDVI document.
5.2.2 Frequency of Calibration.
See the NDVI document.
5.2.3 Other Calibration Information.
See the NDVI document.
6. PROCEDURE
6.1 Data Acquisition Methods.
The 1 X 1 degree LAI data set is calculated from the 1 X 1 degree global
FPAR data set, the VEG_CLSS.VGC data and a look-up table (section 9.2.1).
6.2 Spatial Characteristics.
6.2.1 Spatial Coverage.
The coverage is global. Data in each file are ordered from North
to South and from West to East begining at the international
dateline. Point (1,1) represents the grid cell centered at 89.5 N
and 179.5 W (see section 8.4).
6.2.2 Spatial Resolution.
The data are given in an equal-angle grid that has a spatial
resolution of 1 X 1 degree lat/long.
6.3 Temporal Characteristics.
6.3.1 Temporal Coverage.
January 1987 through December 1988.
6.3.2 Temporal Resolution.
Monthly mean.
7. OBSERVATIONS
7.1 Field Notes.
Not applicable.
8. DATA DESCRIPTION
8.1 Table Definition With Comments.
Not applicable.
8.2 Type of Data.
--------------------------------------------------------------------------------
| 8.2.1 | | | |
|Parameter/Variable Name | | | |
--------------------------------------------------------------------------------
| | 8.2.2 | 8.2.3 | 8.2.4 | 8.2.5 |
| |Parameter/Variable Description |Range |Units |Source |
--------------------------------------------------------------------------------
|LAI | | | |
| |Leaf area index, which is the |min = 0.01 |[Unitless]* |Sellers |
| |ratio of leaf surface to ground |max = | |et al |
| |surface. |See footnote$ | |(1994a) |
| | | | | |
--------------------------------------------------------------------------------
$A minimum value of 0.01 has been inserted into the FASIR_NDVI data sets for
regions (Antarctic, Greenland...) that are classified as missing data in the
NDVI data set (see NDVI.DOC). Note: some of these regions have no
vegetation. The LAI maximum values are dependent on the vegetation class,
see table in section 9.2.1.
*Leaf area index Units are non-dimensional, [m^2 m^-2].
8.3 Sample Data Base Data Record.
Not applicable.
8.4 Data Format.
The CD-ROM file format is ASCII, and consists of numerical fields of
varying length, which are space delimited and arranged in columns and
rows. Each column contains 180 numerical values and each row contain 360
numerical values.
Grid arrangement
ARRAY(I,J)
I = 1 IS CENTERED AT 179.5W
I INCREASES EASTWARD BY 1 DEGREE
J = 1 IS CENTERED AT 89.5N
J INCREASES SOUTHWARD BY 1 DEGREE
90N - | - - - | - - - | - - - | - -
| (1,1) | (2,1) | (3,1) |
89N - | - - - | - - - | - - - | - -
| (1,2) | (2,2) | (3,2) |
88N - | - - - | - - - | - - - | - -
| (1,3) | (2,3) | (3,3) |
87N - | - - - | - - - | - - - |
180W 179W 178W 177W
ARRAY(360,180)
8.5 Related Data Sets.
1 X 1 degree normalized difference vegetation index (NDVI) global data
(on this CD-ROM).
1 X 1 degree Fourier based adjustment, solar zenith angle correction,
interpolation of missing data and reconstruction of evergreen
broadleaf land cover types (tropics), (FASIR-NDVI) data (on this
CD-ROM).
1 X 1 degree fraction of photosynthetic active radiation absorbed by the
vegetation canopy (FPAR) monthly global data (on this CD-ROM).
1 X 1 degree leaf area index (LAI) global data (on this CD-ROM).
1 X 1 degree GREENNESS global data (on this CD-ROM).
1 X 1 degree roughness length (ZO) monthly global data (on this CD-ROM).
1 X 1 degree snow free SURFACE ALBEDO monthly global data (on this
CD-ROM).
1 X 1 degree vegetation classification map (Dorman and Sellers 1989,
Nobre et al. 1991), on this CD-ROM.
Also see section 8.5 (Related Data Sets) in the NDVI document.
9. DATA MANIPULATIONS
9.1 Formulas.
Data have been adjusted using both formulas and rules, the
description of the complete procedure is provided under 9.2.
9.1.1 Derivation Techniques/Algorithms.
See section 9.2
9.2 Data Processing Sequence
(Sellers et al., 1994)
9.2.1 Processing Steps and Data Sets).
Two data sets and a lookup table are used for the calculation of
LAI.
1. 1 X 1 degree FPAR data set (FPAR87)
2. land cover classification (VEG_CLSS.VGC)
calculation of LAI from FPAR data
C CALCULATE LEAF AREA INDEX AND GREENNESS FRACTION FROM FPAR.
C
C FPARM = FPAR previous month
C BARKD, STEMSD = biophysical, vegetation type dependent variables
C
C EXPONENTIAL EXTINCTION USED FOR BROADLEAVES : 1,2,6,7,8,10,11,12
C LINEAR MODEL ( CLUMPED CANOPIES ) USED FOR : 4,5,9
C MIXTURE OF LINEAR AND EXPONENTIAL MODELS : 3
C
C-----------------------------------------------------------------
C
C
C
RLINE = 0.
IF( IV .EQ. 4 .OR. IV .EQ. 5 .OR. IV .EQ. 9 ) RLINE = 1.
IF( IV .EQ. 3 ) RLINE = 0.5
C
LAI1 = -1.0/BARK(IV) * ALOG(1.-FPAR ) * (1.-RLINE)
& + FPAR * LAIMAX(IV) * RLINE
LAI0 = -1.0/BARK(IV) * ALOG(1.-FPARM) * (1.-RLINE)
& + FPARM * LAIMAX(IV) * RLINE
DEAD = AMAX1( 0.0001,( LAI0-LAI1) ) + STEM(IV)
GREEN = LAI1/( LAI1 + DEAD )
LAI = LAI1 + DEAD
C
RETURN
END
where
BARK = -1/LAIMAX(IV)*ALOG(0.05)
LAIMAX = maximum LAI for particular vegetation/land cover type
IV refers to land cover class, see documentation VEG_CLSS.VGC.
=====================
vegetation parameters
=====================
1 7.0 0.08
2 7.0 0.08
3 7.5 0.08
4 8.0 0.08
5 8.0 0.08
6 5.0 0.20
7 5.0 0.20
8 5.0 0.20
9 5.0 0.20
10 5.0 0.20
11 5.0 0.20
12 6.0 0.20
IV LAIMAX STEM
9.2.2 Processing Changes.
Not available at this revision.
9.3 Calculations.
9.3.1 Special Corrections/Adjustments.
Not available at this revision.
9.4 Graphs and Plots.
Not available at this revision.
10. ERRORS
10.1 Sources of Error.
1. Errors inherited from other data sets (see NDVI,
FASIR and FPAR data sets).
2. Assumptions on LAI - FPAR relation, Note: LAI is not as
critical a parameter in the calculation of heat and water
exchange as FPAR.
10.2 Quality Assessment.
10.2.1 Data Validation by Source.
A point-area level verification of these LAI fields has yet
to be made (Sellers et al., 1994, 1995). The numbers obtained
are generally lower than those from point measurements
reported in the literature, possibly because these were
derived for fairly idealized situations.
10.2.2 Confidence Level/Accuracy Judgment.
See FASIR, NDVI and FPAR documents. The numbers obtained
are generally lower than those from point measurements
reported in the literature, possibly because these were
derived for fairly idealized situations. There is evidence
that the relationship between NDVI and LAI is fairly weak,
and by no means as strong as the relationship between FPAR
and NDVI. Hence, we have more confidence in the FPAR fields
than in the LAI fields. The LAI values are fairly sensitive
to changes in the NDVI (e.g. as a result of corrections) or
changes in the estimation of the 98 % values of the NDVI
distributions (see FASIR documentation).
10.2.3 Measurement Error for Parameters and Variables.
See the NDVI, FASIR and FPAR documentation.
10.2.4 Additional Quality Assessment Applied.
Not available at this revision.
11. NOTES
11.1 Known Problems With The Data.
Not available at this revision.
11.2 Usage Guidance.
LAI presents generalized patterns which may result in poor
representations on a local level.
11.3 Other Relevant Information.
Not available at this revision.
12. REFERENCES
12.1 Satellite/Instrument/Data Processing Documentation
Not applicable.
12.2 Journal Articles and Study Reports.
Huemmrich, K. F., and S.N. Goward, 1992. Spectral vegetation indexes
and the remote sensing of biophysical parameters. Proceedings of the
International Geoscience and Remote Sensing Symposium (IGARSS), held
in Houston, Texas. Institute of Electrical and Electronics Engineers,
pp. 1017-1019.
Los, S.O., C.O. Justice, C.J. Tucker, 1994. A global 1 by 1 degree NDVI
data set for climate studies derived from the GIMMS continental NDVI
data. International Journal of Remote Sensing, 15(17):3493-3518.
Monteith, J.L., 1973. Principles of Environmental Physics, Edward
Arnold, 242 pp.
Sellers, P.J., S.O. Los, C.J. Tucker, C.O. Justice, D.A. Dazlich, G.J.
Collatz, and D.A. Randall, 1994. A global 1 by 1 degree NDVI data set
for climate studies. Part 2: The generation of global fields of
terrestrial biophysical parameters from the NDVI. International
Journal of Remote Sensing, 15(17):3519-3545.
Sellers, P.J., S.O. Los, C.J. Tucker, C.O. Justice, D.A. Dazlich, G.J.
Collatz, and D.A. Randall, 1995. A revised land surface
parameterization (SiB2) for atmospheric GCMs. Part 2: The generation
of global fields of terrestrial biophysical parameters from satellite
data. Submitted to Journal of Climate.
12.3 Archive/DBMS Usage Documentation.
Contact the EOS Distributed Active Archive Center (DAAC) at NASA Goddard
Space Flight Center (GSFC), Greenbelt Maryland (see Section 13 below).
Documentation about using the archive or information about access to the
on-line information system is available through the GSFC DAAC User
Services Office.
13. DATA ACCESS
13.1 Contacts for Archive/Data Access Information.
GSFC DAAC User Services
NASA/Goddard Space Flight Center
Code 902.2
Greenbelt, MD 20771
Phone: (301) 286-3209
Fax: (301) 286-1775
Internet: daacuso@eosdata.gsfc.nasa.gov
13.2 Archive Identification.
Goddard Distributed Active Archive Center
NASA Goddard Space Flight Center
Code 902.2
Greenbelt, MD 20771
Telephone: (301) 286-3209
FAX: (301) 286-1775
Internet: daacuso@eosdata.gsfc.nasa.gov
13.3 Procedures for Obtaining Data.
Users may place requests by accessing the on-line system, by sending
letters, electronic mail, FAX, telephone, or personal visit.
Accessing the GSFC DAAC Online System:
The GSFC DAAC Information Management System (IMS) allows users to
ordering data sets stored on-line. The system is open to the public.
Access Instructions:
Node name: daac.gsfc.nasa.gov
Node number: 192.107.190.139
Login example: telnet daac.gsfc.nasa.gov
Username: daacims
password: gsfcdaac
You will be asked to register your name and address during your first
session.
Ordering CD-ROMs:
To order CD-ROMs (available through the Goddard DAAC) users should
contact the Goddard DAAC User Support Office (see section 13.2).
13.4 GSFC DAAC Status/Plans.
The ISLSCP Initiative I CD-ROM is available from the Goddard DAAC.
14. OUTPUT PRODUCTS AND AVAILABILITY
14.1 Tape Products.
None.
14.2 Film Products.
None.
14.3 Other Products.
None.
15. GLOSSARY OF ACRONYMS
AVHRR Advanced Very High Resolution Radiometer
CD-ROM Compact Disk (optical), Read Only Memory
DAAC Destributed Active Archive Center
EOS Earth Observing System
GAC Global Area Coverage
GCM General Circulation Model of the atmosphere
CIA Central Intelligence Agency
FASIR_NDVI Fourier Adjusted, Solar zenith angle correction,
Interpolation (of missing data during winter), and
Reconstruction of NDVI over tropical forests.
FPAR Fraction of Photosynthetic Active Radiation absorbed by
green vegetation
GIMMS Global Inventory Monitoring and Modeling Studies at
NASA GSFC
GSFC Goddard Space Flight Center
GVI Global Vegetation Index
IDS Inter disciplinary Science
IFOV Instantaneous Field Of View
ISLSCP International Satellite Land Surface Climotology Project
LAC Local Area Coverage
LAI Leaf Area Index
NASA National Aeronautics and Space Administration
NDVI Normalized Difference Vegetation Index
NOAA National Oceanographic and Atmospheric Administration
pixel Picture element
SiB2 Simple Biosphere model (Sellers et al 1995)
SR Simple Ratio