Calibration of Landsat thermal data and application to water resource studies

The newest in the Landsat series of satellites was launched April 15, 1999. The imagery collected by Landsat is used for a myriad of applications, from coral reef studies to land management. In order to take advantage of Landsat 7 data, the Enhanced Thematic Mapper+ (ETM+) instrument must be calibrated. This study focuses on the immediate postlaunch calibration verification of the Landsat 7 thermal band (Band 6), specifically so that it can be useful in water resource studies. Two year's worth of thermal calibration results using a combination of underfiight data and ground truth show the ETM+ to be extremely stable, though the prelaunch calibration produces an offset of 0.261 W/m2 sr μm. This paper focuses on the details of the calibration process, including problems faced with ground truth instrumentation. While the technical emphasis in this paper is the calibration of Landsat thermal data, it is presented in the context of the water resource studies for which calibrated thermal data are required. At certain times in the year, water quality in large lakes, particularly the spatial structure of water quality, is driven by temperature of lake waters. During the spring warming, a phenomena called the thermal bar drives the current and sedimentation of large water bodies. A long-term goal of this study is to use thermally driven hydrodynamic models of lake processes to better understand and monitor water quality in large lakes. This paper presents the hydrodynamic model and the relationship between temperature and water quality in the Great Lakes as one example of why high-resolution, well-calibrated data are critical to earth observing. © 2001 Elsevier Science Inc. All rights reserved

Hypoxic contraction of small pulmonary arteries from normal and endotoxemic rats: fundamental role of NO.

The present study was aimed at examining the role of nitric oxide (NO) in the hypoxic contraction of isolated small pulmonary arteries (SPA) in the rat. Animals were treated with either saline (sham experiments) or Escherichia coli lipolysaccharide [LPS, to obtain expression of the inducible NO synthase (iNOS) in the lung] and killed 4 h later. SPA (300- to 600-micrometer outer diameter) were mounted as rings in organ chambers for the recording of isometric tension, precontracted with PGF2alpha, and exposed to either severe (bath PO2 8 +/- 3 mmHg) or milder (21 +/- 3 mmHg) hypoxia. In SPA from sham-treated rats, contractions elicited by severe hypoxia were completely suppressed by either endothelium removal or preincubation with an NOS inhibitor [NG-nitro-L-arginine methyl ester (L-NAME), 10(-3) M]. In SPA from LPS-treated rats, contractions elicited by severe hypoxia occurred irrespective of the presence or absence of endothelium and were largely suppressed by L-NAME. The milder hypoxia elicited no increase in vascular tone. These results indicate an essential role of NO in the hypoxic contractions of precontracted rat SPA. The endothelium independence of HPV in arteries from LPS-treated animals appears related to the extraendothelial expression of iNOS. The severe degree of hypoxia required to elicit any contraction is consistent with a mechanism of reduced NO production caused by a limited availability of O2 as a substrate for NOS