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CLPX-Satellite: AVHRR/HRPT Brightness Temperatures and Reflectances

Summary

This data set includes AVHRR/HRPT (Advanced Very High Resolution Radiometer/High Resolution Picture Transmission) brightness temperatures and reflectances over the NASA Cold Land Processes Field Experiment (CLPX) Large Regional Study Area (LRSA) (NW corner: 42°N, 108.5°W, SE corner: 38.5°N 104°W). Data are gridded to the LRSA at 1.1 km (or 30 arc-second) resolution. Data were collected between November 2001 and June 2003. Reflectance files contain flat binary rasters of 2-byte unsigned integers representing albedo. The brightness temperature files contain 2-byte unsigned integers representing interpolated temperatures in tenths of degrees Kelvin.

Citing These Data

Cline, D. 2004. CLPX-Satellite: AVHRR/HRPT Brightness Temperatures and Reflectances. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format

Reflectance files: flat binary rasters of 2-byte unsigned integers representing albedo.
Brightness temperature files: 2-byte unsigned integers representing interpolated temperatures in tenths of degrees Kelvin.
Images: tiff images and tfw (header files)

Spatial coverage CLPX LRSA in Colorado and Wyoming
Upper left: 42°N, 108.5°W
Lower right: 38.5°N 104°W
Temporal coverage and resolution Sporadic coverage between 9 November 2001 and 26 June 2003
Total File size Compressed files range in size from 4.6 to 4.85 KB.
Parameter(s) Brightness temperatures and reflectances
Procedures for obtaining data Data are available via FTP

Table of Contents

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

1. Contacts

Investigator(s) Name and Title

Don Cline
National Weather Service
National Operational Hydrologic Remote Sensing Center
1735 Lake Drive W.
Chanhassen, MN 55317

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

2. Detailed Data Description

The Advanced Very High Resolution Radiometer (AVHRR) data set is comprised of data collected by the AVHRR sensor, carried aboard the National Oceanic and Atmospheric Administration's Polar Orbiting Environmental Satellite series. The AVHRR sensor is a broadband 5-channel scanning radiometer, sensing in the visible, near-infrared, and thermal infrared portions of the electromagnetic spectrum. Please refer to NOAA's AVHRR site for further information about this sensor.

This data set includes AVHRR/HRPT rasters; five bands co-registered to the UTM and Geographic (lat-lon) grids of the CLPX LRSA. Data are provided for the five wavelengths 0.63, 0.91, 1.61, 10.8 and 12.0 microns; HRPT channels 1, 2, 3a, 4 and 5. Data are calibrated to reflectance and brightness temperature using on-board coefficients, reprojected from swath space to geographic grid, and exported as 16-bit binary rasters. The data are also reprojected to UTM, Zone 13. Daylight passes were collected from NOAA-16 and NOAA-17.

Format

Reflectance files contain flat binary rasters of 2-byte unsigned integers. The values represent percent albedo, multiplied by 100, ranging from 0 to 10000. The brightness temperature files contain 2-byte unsigned integer representing interpolated temperatures in tenths of Kelvins. The values range roughly from 2300 to 3100. Data are gridded to the LRSA, at 1.1 km (or 30 arc-second) resolution.

File and Directory Structure:

Data are provided as tarred and zipped binary and tiff files; one each for UTM and geographic grids. Within the compressed files, the data structure is:

binary_geo.tgz/
     2001-11-09.2030.noaa-16.geo.ch1.bil
     2001-11-09.2030.noaa-16.geo.ch1.blw
     2001-11-09.2030.noaa-16.geo.ch1.hdr
     etc...
binary_utm.tgz/
     2001-11-09.2030.noaa-16.utm.ch1.bil
     2001-11-09.2030.noaa-16.utm.ch1.blw
     2001-11-09.2030.noaa-16.utm.ch1.hdr
     etc...
tiff_geo.tgz/
     2001-11-09.2030.noaa-16.geo.ch1.tfw
     2001-11-09.2030.noaa-16.geo.ch1.tif
     2001-11-09.2030.noaa-16.geo.ch2.tfw
     etc...
tiff_utm.tgz/
     2001-11-09.2030.noaa-16.utm.ch1.tfw
     2001-11-09.2030.noaa-16.utm.ch1.tif
     2001-11-09.2030.noaa-16.utm.ch2.tfw
     etc...	
lrsa-meta.tgz/
     2001-11-09.2030.noaa-16.geo.ch1.blw
     2001-11-09.2030.noaa-16.geo.ch1.meta
     etc...

File Naming Convention

Compressed files are named binary_geo.tgz, binary_utm.tgz, tiff_geo.tgz, and tiff_utm.tgz. WIthin the compressed files, individual data files are named as follows.

Raw reflectance data files are named YYYY-MM-DD.HHMM.noaa-SS, where

YYY = Year
MM = Month
DD = Day
HHMM = Hour Minute
SS = Satellite number (16 or 17).

Processed data files are split into two subdirectories, binary and tiff. Within each subdirectory data have been reprojected into Geographic and UTM formats. The file naming structure for binary data in geographic format is YYYY-MM-DD.HHMM.noaa-SS.geo.chX, where

YYY = Year
MM = Month
DD = Day
HHMM = Hour Minute
SS = Satellite number (16 or 17)
X = Channel (1, 2, 3a, 4 and 5).

Each file is available in *.bil (binary interleaved by line), *.blw (georeferencing information) and *.hdr (standard header information) formats. The file naming structure for binary data in UTM format is similar to the geographic format, except for the use of ‘utm' instead of ‘geo' in the file naming format. For example:

YYYY-MM-DD.HHMM.noaa-SS.utm.chX

The tiff subdirectories follow the same file naming structure for both Geographic and UTM reprojections as the binary subdirectories. However the file types in the tiff subdirectory are *.tif (image files) and *.tfw (header files for TIF files).

Metadata files are available to support each AVHRR scene, in both UTM and Geographic reprojections. Metadata files follow the same naming structure as the processed data files but with *.meta file types.

File Size

Compressed files range in size from 4.6 to 4.85 KB.

Spatial Coverage

This data set covers the CLPX LRSA in Colorado and Wyoming.

Upper Left Boundary: 42°N, 108.5°W
Lower Right Boundary: 38.5°N, 104°W

Data are gridded to the LRSA, at 1.1 km (or 30 arc-second) resolution.

Spatial Coverage Map:

The following map shows the CLPX LRSA:

Temporal Coverage

Data were collected between 9 November 2001 and 26 June 2003. The complete temporal coverage is given in the following table.

Year

Month

Day

Time

2001

11

9

2030

2001

12

7

2050

2002

2

12

2005

2002

2

20

2034

2002

3

1

2037

2002

3

9

2052

2002

3

12

2017

2002

3

13

2006

2002

3

20

2032

2002

3

21

2020

2002

3

22

2009

2002

3

31

2012

2002

4

8

2025

2002

4

10

2003

2002

4

17

2028

2002

4

28

2008

2002

5

5

2034

2002

5

6

2023

2002

5

7

2012

2002

12

2

2020

2002

12

5

1717

2002

12

23

1713

2003

1

7

2021

2003

1

17

1752

2003

1

21

1802

2003

1

23

1722

2003

1

27

1732

2003

1

29

1828

2003

2

3

2021

2003

2

10

1712

2003

2

12

1807

2003

2

17

1756

2003

2

18

1732

2003

2

22

2008

2003

2

27

1724

2003

3

3

1739

2003

3

10

2032

2003

6

13

1744

2003

6

17

1753

2003

6

21

1804

2003

6

22

1741

2003

6

24

2050

2003

6

25

1814

2003

6

26

1751

 

Parameter or Variable

Parameters presented in this data set are brightness temperatures and reflectances.

Sample Data Record

Accompanying the raw data files are header files (*.hdr) that provide information about each raw reflectance file. An example of a header files is shown below.

            Space Science & Engineering Center 
            University of Wisconsin - Madison 
        Man computer Interactive Data Access System (McIDAS) 
		
Satellite: NOAA-16                     SSEC ID Number: 66 
Image Date: 7 DEC 01 (YYDDD=01341)     Image Start Time: 20:36:29 GMT 
 
                    IMAGE COORDINATES 
Start Line    Start Element     Line Resolution     Element Resolution 
   1240           284                  1                    1 
   
                      IMAGE FILE(S) 
File Name     Parameter    Unit     Band     Lines    Elements    Element Format    Scale 
------------ ------------  ----     ----    -------   --------   ------------------ ----- 
W341.HDR     Header ASCII (80 Chars) 
W341.001     Raw Sensor    none       1       2000     1400 Int      (16 bit)         1 
W341.002     Raw Sensor    none       2       2000     1400 Int      (16 bit)         1 
W341.003     Raw Sensor    none       4       2000     1400 Int      (16 bit)         1 
W341.004     Raw Sensor    none       5       2000     1400 Int      (16 bit)         1 
W341.005     Raw Sensor    none       6       2000     1400   Int    (16 bit)         1  
W341.LAT     Latitude      NA        2000     1400     Integer       (16 bit)         100 
W341.LON     Longitude     NA        2000     1400     Integer       (16 bit)         100 
  * - Navigation files resolution: 1 Lat/Lon per every 1   image element(s)     
  * - Navigation files missing data value = 65535                               
                                                                                
                 SSEC NAVIGATION BLOCK (All nonzero entries)                    
  1. TIRO             2. 6601341          3. 203259           4. 1              
  5. 11209            6. 12246            7. 722992           8. 1094           
  9. 98849           10. 260389          11. 99859           12. 286025         
 13. 2048            14. 54128           15. 621             46. 1              
 47. 1040            48. 73979117        49. 167             51. 2200           
 52. 2048            53. 166667          54. 8138                

The following is an example of a UTM metadata file:

HRPT data for LRSA

Date:		2001-11-09
Time:		2030
Satellite:  NOAA-16
Upper Left latitude:     42.04999923706055
Upper Left longitude:  -108.55000305175781
Lower Right latitude:    38.45
Lower Right longitude: -103.95
Datum: WGS84
Approximate coverage: 4.6 x 3.6 degrees =~ 400km x 400km
UTM Grid
Zone: 13
Semi-Major Axis of Ellipsoid: 6378137.000 meters
Semi-Minor Axis of Ellipsoid: 6356752.314245 meters
Scale Factor of C Meridian:	0.999600
Longitude of Central Meridian: -105.0000  degrees
Upper Left XY:  175000.0, 4675000.0 = 42.159677085 M. 108.933826235 W
Lower Right XY:	600000.0, 4250000.0 = 38.392627781 N, 103.854898585 W
Datum: WGS84
X resolution: 816.83574327477345
Y resolution: -816.83574327477345
Upper Left X: 190250.60697080070000
Upper Left Y: 4661756.31889947410000
Rows: 497
Columns: 491
Nbits: 16
Nbands: 1

3. Data Access

Data Access

Data are available via FTP at ftp://sidads.colorado.edu/pub/DATASETS/CLP/data/satellite/nsidc0152_avhrr/.

Related Data Collections

All CLPX Data Sets
AVHRR Data at NSIDC

Quality Assessment:

The AVHRR sensor was designed to view cold space and one or more internal warm blackbodies for each scan sequence while in orbit. In general, radiometric calibration involves exposing a radiometer to sources of radiation that have been calibrated against primary or secondary standards and determining a relationship between the output of the radiometer and the intensity of the incident radiation (radiance). All of the radiometers flown on the NOAA/TIROS satellites undergo extensive prelaunch testing and calibration by their manufacturers to characterize their performance.

As the spacecraft moves through its orbit, the expected angular distance between the nadir of adjacent LAC/HRPT scans is approximately 0.0296 degrees of arc, or 3.2914 kilometers, as measured from the center of Earth. The actual value of the average angular distance can vary by up to about 0.1712 kilometers due to variations in satellite height, scan angle, and other factors. The instantaneous field-of-view (IFOV) for all channels is specified to be 1.3 +/- 0.1 milliradians.

4. Data Acquisition

These data were captured on a McIDAS SDI system and processed in the McIDAS software package (a suite of applications for analyzing and displaying meteorological data). Data are calibrated to reflectance and brightness temperature using on-board coefficients, reprojected from swath space to geographic grid, and exported as 16-bit binary rasters. The data are also reprojected to UTM, Zone 13.

6. Document Information

List of Acronyms

AVHRR = Advanced Very High Resolution Radiometer
CLPX = NASA Cold Land Processes Field Experiment
HRPT = High Resolution Picture Transmission
IOP = Intensive Observation Period
ISA = Intensive Study Area
LRSA = Large Regional Study Area
LSOS = Local Scale Observation Site
MSA = Meso-cell Study Area

Document Creation Date

19 February 2004

Document URL

http://nsidc.org/data/nsidc-0152.html