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SMEX02 Regional Vegetation Sampling Data, Iowa

Summary

This data set contains the vegetation parameters plant height, row spacing, stand density, and leaf area index (LAI) as part of the Soil Moisture Experiment 2002 (SMEX02). The SMEX studies are designed to evaluate, among other things, the accuracy of AMSR-E soil moisture data.

This study was conducted during June and July 2002 in the SMEX02 Iowa regional area around Ames, Iowa, USA. LAI was measured by a plant canopy analyzer. The other parameters were measured manually.

LAI is the ratio of the total area of all leaves on a plant to the area of ground covered by the plant. Stand density is the number of plants in a meter length of a crop row. Plant height and row spacing data are given in meters.

Data are provided as ASCII text files and are available via FTP.

These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.

Citing These Data

Anderson, M. 2003. SMEX02 Regional Vegetation Sampling Data, Iowa. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format Data are provided as ASCII text files.
Spatial coverage and resolution 41.7°N to 42.7°N, 93.2°W to 93.8°W.
Temporal coverage and resolution Select dates between 30 June to 28 July 2002.
File naming convention "IA_LAI_Raw.txt" contains the raw data; "IA_LAI_Sum.txt" contains the summary data.
File size File sizes are: "IA_LAI_Raw.txt" 16.0 KB, and "IA_LAI_Sum.txt" 3.76 KB.
Parameter(s) The parameters are plant height, row spacing, stand density, and leaf area index (LAI).
Procedures for obtaining data Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Martha Anderson
Assistant Scientist
Space Science and Engineering Center
University of Wisconsin, Madison, WI, USA.

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

Many graduate students and volunteers collected the field data.

2. Detailed Data Description

Format

Data are provided as ASCII text files.

File Naming Convention

"IA_LAI_Raw.txt" contains the raw data; "IA_LAI_Sum.txt" contains the summary data.

File Size

File sizes are: "IA_LAI_Raw.txt" 16.0 KB, and "IA_LAI_Sum.txt" 3.76 KB.

Spatial Coverage

Southernmost Latitude: 41.7° N
Northernmost Latitude: 42.7° N
Westernmost Longitude: 93.8° W
Easternmost Longitude: 93.2° W

Temporal Coverage

Dates for sampling were 29 and 30 June, and 3, 9, 28, and 29 July 2002.

Parameter or Variable

Parameter Description

The parameters are plant height, row spacing, stand density, and leaf area index (LAI).

The following table describes each column in the "IA_LAI_Raw.txt" data file.

Column heading Description
SITE Site location number
SAMPLE Sampling point 1-5 for each site location
Latitude Latitude of the sampling site
Longitude Longitude of the sampling site
UTM_East UTM Easting in meters (Zone 15)
UTM_North UTM Northing in meters (Zone 15)
LAI Leaf Area Index
Date MM/DD/YYYY
DAY Numerical day of the year (Julian date)
Time HHMMSS (Central Standard Time)
Adjusted Readings corrupted by sun glare were adjusted by an interpolated estimate

The following table describes each column in the "IA_LAI_Sum.txt" data file.

Column heading Description
SITE Site location number
Latitude Latitude of the sampling site
Longitude Longitude of the sampling site
UTM_East UTM Easting in meters (Zone 15)
UTM_North UTM Northing in meters (Zone 15)
DOY Numerical day of the year (Julian date)
date MM/DD/YYYY
LAI-Mean Mean Leaf Area Index
LAI-StDev Standard deviation of Leaf Area Index
Crop C=Corn, S=Soy
Row_Spacing in m Space between rows in meters
Row_Density Number of plants in one meter
Height in m Vegetation height in meters

Unit of Measurement

Parameter Source

LAI is measured by a plant canopy analyzer. Row spacing, row density, and plant height were measured manually.

Sample Data Record

The following sample is taken from the "IA_LAI_Raw.txt" data file.

SITE SAMPLE Latitude Longitude UTM_East UTM_North LAI Date DOY TIME Adjusted
IA01 1 42.65988 -93.71737 441207 4723296 2.45 6/30/2002 181 11:53:30 **
IA01 2 42.65988 -93.71737 441207 4723296 2.71 6/30/2002 181 11:55:24 **
IA01 3 42.65988 -93.71737 441207 4723296 1.87 6/30/2002 181 11:57:01
IA01 4 42.65988 -93.71737 441207 4723296 2.06 6/30/2002 181 11:58:21

The next sample is taken from the "IA_LAI_Sum.txt" data file.

SITE Latitude Longitude UTM_East UTM_North DOY date LAI-Mean LAI-StDev Crop Row_Spacing in m Row_Density Height in m
IA01 42.65988 -93.71737 441207 4723296 181 6/30/2002 2.252 0.023 C 0.75 7 1.524
IA02 42.58718 -93.70582 442086 4715215 181 6/30/2002 2.612 0.034 C 0.75 7 2.1336
IA03 42.50662 -93.71921 440911 4706278 181 6/30/2002 1.29 0.072 S 0.75 30 0.381
IA04 42.41222 -93.72801 440099 4695803 181 6/30/2002 2.39 0.089 C 0.75 6 1.524
IA05 42.34171 -93.72867 439977 4687974 181 6/30/2002 1.398 0.025 C 0.75 6 1.397

Error Sources

In the final processing, certain LAI readings were determined to have been corrupted by sun glare. These readings were adjusted or recovered by replacing an interpolated estimate. This was done for approximately 36 of the 236 readings, and one reading was determined to be too corrupted to adjust. A value of "-99" indicates missing or corrupt data.

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume of the data files is 19.76 KB.

Related Data Collections

See related information on the NSIDC Soil Moisture Experiment (SMEX) Web site.

4. Data Acquisition and Processing

Theory of Measurements

The purpose of vegetative sampling is to provide an estimate of the variation in the vegetative components in the corn and soybean fields across the SMEX02 study sites. Sampling dates are provided in the data files for each field.

Sensor or Instrument Description

LAI sampling was done using LI-COR LAI-2000 instruments.

Data Acquisition Methods

Five locations were sampled in each field in the IA regional soil moisture sampling site. Samplers chose locations far enough away from each other to gain independent samples. At each location, leaf area was measured at four locations (in-row, ¼ across row, ½ across row, ¾ across row) with the plant canopy analyzer. The first sampling position was between the first row and the row to the left.

Leaf area was measured in the inter-row region at least one meter away from where the manual samples were taken. The analyzer was set to average four locations into a single value, so one observation was taken above the canopy and four beneath the canopy; in the row, ¼ of the way across the row, ½ of the way across the row, and ¾ of the way across the row. This gave a good spatial average for row crops of partial cover. The sampler always stood with the back to the sun (if it was shining). A lens cap that blocks ¼ of the sensor view was always in place and positioned so the sun and the sampler were never in the view of the sensor.

5. References and Related Publications

Please see the SMEX02 site for more information, and the NSIDC SMEX site to access data.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

FTP File Transfer Protocol
LAI Leaf Area Index
SMEX Soil Moisture Experiment
UTM Universal Transverse Mercator

Document Creation Date

September 2003

Document URL

http://nsidc.org/data/docs/daac/nsidc0188_smex_veg_regional.gd.html