Evaluating Spaceborne Tropospheric Ozone Time Series With Sonde Data
Creators: name: Zörner, Jan
Publisher: name: Zenodo
Year: 2012
Subjects: tropospheric ozone, TES, AURA, ozone sonde

description: <strong>Abstract</strong>

Tropospheric ozone is a global air pollutant and an important greenhouse gas. It is mainly produced by the photochemical reaction of short-wave radiation with precursor molecules such as NOx and VOC’s originating from anthropogenic pollution and biogenic sources. Besides that, intrusions of stratospheric ozone into the higher troposphere contribute to<br>
the ozone abundance in the lower atmosphere. Ozone sondes provide in-situ measurements of temperature, pressure, humidity and ozone from balloons launched from stations located all over the world. The distribution of ozone in the troposphere is not uniform and varies both temporally as well as spatially. In contrast to the poor spatial sampling<br>
by sondes, satellite sensors provide a much better coverage of ozone measurements in time and space enabling the understanding of patterns and origins of tropospheric ozone. These sensors, for instance TES (Tropospheric Emission Spectrometer onboard NASA’s EOS Aura satellite), however need to be evaluated with independent data, such as worldwide sonde ozone data (i.e. World Ozone and Ultraviolet Data Center, WOUDC). The objective of this study is to investigate the usefulness of TES ozone measurements for a multi year trend analysis of global ozone mixing ratios. Thereby, the TES version 4 data set is compared against sonde data as reference from the WOUDC data archive for the period 2005-2010. A comparison between the TES and the sonde data provides an in-depth consistency check of TES vertical ozone profiles on a global and multi-year basis. A maximum range of 300 km and a maximum time difference of ±9 hours between the TES and ozone sonde retrieval are used as coincident criteria to increase the probability that the same air parcels are sampled. To ensure a valid comparison, the TES operator, comprising the TES averaging kernel matrix and a priori information, is applied on the sonde data. Validation of TES tropospheric ozone is conducted for the lower (&gt;500 hPa) and upper (&lt;500 hPa) troposphere, at the 464 hPa pressure level, per season, year, station, latitudinal zone and for some specific regions. Validation results for all seasons and all stations show better agreement between TES version 4 and sonde ozone in the upper troposphere than in the lower troposphere, consistent with the better sensitivity of the satellite instrument higher up in the troposphere. Generally, TES is biased high by 0-15 ppbv in the troposphere, in<br>
line with earlier reports on the validation of TES version 2 retrievals with sondes. The linear trend analysis of free tropospheric ozone indicates a significant (p&lt;0.05) increase in summer time tropospheric ozone over North East China. Further, linear trends analysis of monthly ozone averages show a significant (p&lt;0.05) increase of tropospheric ozone in tropical regions (35N to 35S).

Dissertation presented in fulfillment of the requirements for the degree of Master of Science in Earth Observation at the Faculty of Bioscience-Engineering, KU Leuven, Leuven, Belgium.

Thesis research was conducted at the Eindhoven University of Technology (TU/e), The Netherlands, supervised by Dr. KF (Folkert) Boersma and Dr. Willem W. Verstraeten.
description: Thesis research was conducted at the Eindhoven University of Technology (TU/e), The Netherlands, supervised by Dr. KF (Folkert) Boersma and Dr. Willem W. Verstraeten.