CLPX-Ground: Ground-Based Infrared Images of the LSOS Site


This data set presents more than 400 sub-canopy digital thermograms collected at the Fraser Experimental Forest (Fraser, Colorado, USA) using an Infrared Solutions IR SnapShot™ thermoelectric thermal infrared (IR) imaging radiometer that was cold-weather modified.

Citing These Data

Rowlands, A., R. Essery, and J. Pomeroy. 2005. CLPX-Ground: Ground-Based Infrared Images of the LSOS Site. [indicate subset used]. Boulder, Colorado USA: NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: 10.5067/BYFK490NJTAD.

Overview Table

Category Description
Data format Binary (.dat), Infrared Solutions format (.ISI), and comma-separated ASCII (.csv)
Spatial coverage CLPX Local Scale Observation Area (LSOS) in northern Colorado (100 m x 100 m). 39.9066° N, 105.8829° W
Temporal coverage

18-22 February 2002 (Intensive Observation Period, IOP1), 28-30 March 2002 (IOP2), 26-30 March 2003 (IOP4)

Total File size IR files range from 5 to 29 KB. Meteorological files are 96 and 100 KB.
Parameter(s) Infrared Solutions format digital thermograms, and meteorological parameters
Procedures for obtaining data Data are available via FTP and HTTPS.

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

John W. Pomeroy
Department of Geography
Rm 42 Kirk Hall
117 Science Place
University of Saskatchewan
Saskatoon, SK Canada S7N 5C8

Aled Rowlands
Institute of Geography and Earth Sciences
University of Wales
Aberystwyth, Ceredigion
SY23 3DB Wales, UK

Richard Essery
Centre for Glaciology
Institute of Geography and Earth Sciences
University of Wales
Aberystwyth, Ceredigion
SY23 3DB Wales, UK

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services

2. Detailed Data Description

This data set presents sub-canopy digital thermograms (infrared images) from two pine sites and a small clearing at the CLPX Local Scale Observation Site (LSOS) in northern Colorado. The LSOS is a 0.8-ha study site located within the Fraser Intensive Study Area (ISA). The study area has flat topography with a uniform pine forest, a discontinuous pine forest, and a small clearing. Each digital thermogram is 120 x 120 pixels. The instrument was mounted on a tripod and obtained an image every 15 minutes from approximately 0730 until 1800 local time. The instrument was aimed at different scenes on different days, but consistantly looked at the same scene throughout each day.

Meteorological data were collected in conjunction with some of these measurements (during IOP2). Meteorological parameters were temperature, albedo, short-wave radiation, long-wave radiation, and net radiation.


Infrared images are presented as binary (.dat) files (IOP1 only) and Infrared Solutions formatted (.ISI) digital thermograms. Data are supplied in °C and Wm-2. The spectral range is 8 to 12 µm.

Meteorological data are available as comma-separated ASCII files (.cvs). Missing data are identified by "-999". The dense-pine and open-pine meteorological data files have the following column headers:

TC1 (°C)
TC2 (°C)
TC3 (°C)
TC4 (°C)
Kup (Wm-2)
Kdown (Wm-2)
Knet (Wm-2)
Lnet (Wm-2)
NetRad (open pine only) (Wm-2)
Lup (Wm-2)
Ldown (Wm-2)


TC = Thermocouple
K = Short-wave radiation
L = Long-wave radiation
NetRad = Net Radiation
DecDay = Decimal Day

File and Directory Structure:

Data are available via FTP in the following directory structure:

  020218_raw/ (date of measurements: YYMMDD)

File Naming Convention

In each IOP, IR images are named IR##### with .dat or .ISI file extensions, where ##### refers to a four- or five-digit number representing the number of the photograph recorded in each IOP.

Meteorological files are named "clpx_open_met_data_jd86-88.csv" and "clpx_dense_met_data_jd86-88.csv".

File Size

IR files range from 5 to 29 KB. Meteorological files are 96 and 100 KB.

Spatial Coverage

This data set covers the CLPX Local Scale Observation Area (LSOS) in northern Colorado. This site is 100 m x 100 m (39.9066°N, 105.8829°W).

Spatial Coverage Map:

The following maps show the CLPX LSOS, with the uniform pine area to the south and east of clearing, and the discontinuous pine site to the north of the clearing.

spatial coverage map

Temporal Coverage

IR images were collected during IOP1 (18-22 February 2002), IOP2 (28-30 March 2002), and IOP4 (26-30 March 2003). Meteorological data were collected on 27-29 March 2002. Images were recorded at various times throughout the day, between 0730 and 1800 local time. The following figure provides an example of diurnal differences in sub-canopy thermal energy in the dense and open pine areas:

spatial coverage map

Parameter or Variable

Parameters include digital thermograms, hypodermic needle thermocouple temperature, shortwave radiation, longwave radiation, net radiation, and albedo.

Quality Assessment

The IR SnapShot™ has a spectral range of 8 to 12 μm, an absolute accuracy of 1.2˚C, and a differential accuracy of 0.1˚C. Separate tests with the imaging radiometer, narrow-beam thermal infrared radiometers, and hypodermic needle thermocouples inserted into various natural surfaces onsite confirmed that the imaging radiometer was operating well within accuracy specifications.

3. Data Access

Data Access

Data are available via FTP and HTTPS.

Related Data Collections

All CLPX Data Sets
CLPX-Ground: ISA Snow Pit Measurements
Sub-Canopy Energetics at the CLPX Local Scale Observation Site (LSOS)
CLPX-Ground: Micrometeorological Data at the Local Scale Observation Site (LSOS)
CLPX-Ground: Ground-based L and Ku Band Polarimetric Scatterometry at the LSOS
CLPX-Ground: Ground Based Passive Microwave Radiometer (GBMR-7) Data at the LSOS

4. Data Acquisition

The IR SnapShot™ Thermoelectric Infrared Imaging Radiometer has the following specifications:

Detector: 120-element linear array of uncooled thermoelectric detectors, 50 µm square pixels
System Dynamic Range:
12 bits usable with digitizing resolution of 16 bits
17.2° horizontal and vertical
Lens: Germanium 20 mm, F/0.8, focus 10” to infinity
Spectral Band:
8 µm to 12 µm, anti-reflection-coated Germanium optics
<0.1°C at 30°C
2°C or 2% of reading
Measurement Temperatures:
0 to 350°C (custom ranges available within -30°C to 600°C)
Operating Temperature:
0 to 40°C (0 to 50°C custom range available)
Image Scan Time:
<1.5 seconds

Some thermocouple (TC) measurements were made using an IRTC (Infrared Thermocouple) from Exergen, Inc. Others were made using a HYP-0 (Hypodermic Thermocouple) from Omega Engineering. Kup, Kdown, Knet, albedo, NetRad, Lup, and Ldown were measured using a CNR1 Net Radiometer from Kipp & Zonen.

5. References and Related Publications

Hardy, J., D. Cline, K. Elder, R. Davis, R. Armstrong, G. Castres Saint-Martin, R. DeRoo, T. Graf, Y. Koh, T. Koike, H-P. Marshall, K. McDonald, T. Painter, and K. Sarabandi (submitted). An overview of data from the Local Scale Observation Site of the Cold Land Processes Experiment (CLPX). Journal of Hydrometeorology.

Hardy, JP, D. Cline, K. Elder, R. Davis, J. Pomeroy, G. Koh, R. Armstrong, T. Koike, and K. McDonald. 2002. The Cold Land Processes Experiment (CLPX) Local Scale Observation Site (LSOS). American Geophysical Union Fall Meeting 6-10 December 2002, San Francisco, California. Eos Transactions 83 (47): F537.

Rowlands, A.P., J.W. Pomeroy, J.P. Hardy, D. Marks, K. Elder, and R. Melloh. 2002. Small-scale variability of radiant energy for snowmelt in a mid-latitude sub-alpine forest. Proceedings of the Eastern Snow Conference 59: 109-119.

6. Document Information

List of Acronyms

CLPX = NASA Cold Land Processes Experiment
IOP = Intensive Observation Period
IR = Infrared
ISA = Intensive Study Area
LRSA = Large Regional Study Area
LSOS = Local Scale Observation Site
MSA = Meso-Cell Study Area

Document Creation Date

15 June 2005