I: Remote Spectroscopic Measurements of Atmospheric HDO/H₂O and Column CO₂. II: Interannual Variations of the Earth’s Reflectance

Citation

Kuang, Zhiming (2003) I: Remote Spectroscopic Measurements of Atmospheric HDO/H₂O and Column CO₂. II: Interannual Variations of the Earth’s Reflectance. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Q9TP-RR97. https://resolver.caltech.edu/CaltechETD:etd-06022003-114148

Abstract

The theme of this thesis is to apply remote sensing data on problems concerning the climate system. It is grouped into two parts. Part I (Chapters 1, 2) is devoted to spectroscopic measurements of HDO, H₂O and column CO₂, and Part II (Chapters 3-5) is devoted to variations in the Earth's reflectance.

In Chapter 1, we derive the first simultaneous measurements of HDO and H₂O in the tropical upper troposphere and lower stratosphere. This is made possible by extending the retrievals of the Atlas-3 Atmospheric Trace Molecule Spectroscopy (ATMOS) data deeper into the troposphere. The derived HDO/H₂O ratio demonstrates that convection has a major influence on the moisture budget and the dehydration processes in this region.

The objective of Chapter 2 is to determine the precision to which column averaged CO₂ volume mixing ratio (VMR) can be measured by near-infrared (NIR) spectrometry of reflected sun light. The key idea in this study is the simultaneous use of the CO₂ (1.58-µm and 2.06-µm) and O₂ (0.76-µm) bands. This approach allows small changes in the spectrum arising from variations of column CO₂ VMR to be distinguished from those arising from variations of other atmospheric/surface parameters. Using prototype retrieval simulations based on a practical satellite instrument design, we show that the 3-band, high-resolution, spectrometric approach using NIR reflected sunlight has the potential for highly accurate column CO₂ VMR measurements.

In Chapters 3-5, we examine the interannual variations in the Earth's reflectance. Chapter 3 introduces the Nimbus-7 TOMS reflectance measurements and provides an overview on the interannual variability of the Earth's reflectance. Variations in the globally averaged reflectance are also used to examine a postulated cosmic ray-cloud-climate connection.

In Chapter 4, we relate interannual reflectance variations over the summertime polar icy areas to variations in the microwave-derived sea ice concentration. The results provide independent confirmation on sea ice variations observed by microwave instruments, and quantify the role of clouds in shielding the reflectance effect of sea ice variations. An interesting hemispheric asymmetry is found: a 1% change in the sea ice concentration is related to a significantly larger reflectance change in the Antarctic than in the Arctic icy areas.

Chapter 5 is devoted to interannual reflectance variations over the northern midlatitude oceans. We find that interannual reflectance variations in these regions are, to a large extent, related to variations in the large scale circulation, mostly through variations in the storms tracks. The findings in this chapter suggest that the response of clouds to climate change may be better viewed from a large-scale circulation perspective, other than a purely thermodynamic one (such as in the cloud-temperature relations), a stand many previous investigations have taken.

Thesis Files