Quest over the Sampling Error of COSMIC Radio Occultation Temperature Climatologies

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  • 1 Jiangsu Key Laboratory of Resources and Environmental Information Engineering, China, University of Mining and Technology, Xuzhou 221116, China,
  • 2 School of Environment Science and Spatial Information, China University of Mining and Technology, Xuzhou 221116, China,
  • 3 Satellite Positioning for Atmosphere, Climate and Environment (SPACE) Research Centre, Royal Melbourne Institute of Technology (RMIT) University, Melbourne VIC 3001, Australia
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Abstract

The sampling error caused by the uneven distribution of radio occultation (RO) profiles in both space and time domains is an important error source of RO climatologies. In this paper, the sampling error RO temperature climatologies is investigated using the 4-year (2007-2010) data from the Constellation Observing System for Meteorology, Ionosphere, and Climate mission. The error is divided into three parts, including local time component (LTC), temporal component (TC), and spatial component (SC). The characteristics of the three components are investigated. Results show that: 1) The LTC part of the total sampling error is characterized by a pattern of periodic positive and negative deviations, with a full cycle of about four months. The most significant LTC values are found in the area around 60° N/S and the polar regions. 2) The TC part is mainly associated with the extent of day-to-day temperature variability and the daily number of RO profiles observed in each month. The most pronounced TC part is shown in high latitude areas in wintertime, where the day-to-day temperature variability is high. 3) The SC part shows distinct features in different altitude ranges. It is characterized by a systemic error in the lower troposphere (2-8 km) but exhibits a seasonal trend at the altitude range from 8 to 40 km. 4) the total sampling error is dominated by the TC and SC parts in the troposphere and lower stratosphere, while in the upper stratosphere, it is dominated by the LTC part.

Corresponding author: Kefei Zhang, E-mail: kefei.zhang@rmit.edu.au.

Abstract

The sampling error caused by the uneven distribution of radio occultation (RO) profiles in both space and time domains is an important error source of RO climatologies. In this paper, the sampling error RO temperature climatologies is investigated using the 4-year (2007-2010) data from the Constellation Observing System for Meteorology, Ionosphere, and Climate mission. The error is divided into three parts, including local time component (LTC), temporal component (TC), and spatial component (SC). The characteristics of the three components are investigated. Results show that: 1) The LTC part of the total sampling error is characterized by a pattern of periodic positive and negative deviations, with a full cycle of about four months. The most significant LTC values are found in the area around 60° N/S and the polar regions. 2) The TC part is mainly associated with the extent of day-to-day temperature variability and the daily number of RO profiles observed in each month. The most pronounced TC part is shown in high latitude areas in wintertime, where the day-to-day temperature variability is high. 3) The SC part shows distinct features in different altitude ranges. It is characterized by a systemic error in the lower troposphere (2-8 km) but exhibits a seasonal trend at the altitude range from 8 to 40 km. 4) the total sampling error is dominated by the TC and SC parts in the troposphere and lower stratosphere, while in the upper stratosphere, it is dominated by the LTC part.

Corresponding author: Kefei Zhang, E-mail: kefei.zhang@rmit.edu.au.
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