Assessment of Atmospheric Wet Profiles Obtained from COSMIC Radio Occultation Observations over China

Guirong Xu,Xinan Yue,Xia Wan,Wengang Zhang

doi:10.3390/atmos8110208

Abstract

Atmosperic profiles derived from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) measurements make up for the lack of operational radiosonde soundings with a high spatiotemporal distribution, and their performance over China is assessed in this paper. COSMIC-retrieved atmospheric wet profiles from 2014 to 2015 are compared to the contemporaneous radiosonde profiles from 120 stations, and the vertical mean differences are used. The results show that the vertical mean biases of temperature, pressure and vapor pressure are −0.10 K, 0.69 hPa and −0.01 hPa, respectively, and that for refractivity is 0.17 N. Moreover, the temperature differences are positively correlated with station altitude, yet both the pressure and vapor pressure differences are negatively correlated with station latitude, as is the refractivity difference. The large temperature difference arising from the Qinghai-Tibet Plateau (QTP) region may be associated with the complex topography of the area and the limitations in the background model used in the COSMIC profile retrieval. Furthermore, negative refractivity bias between COSMIC and radiosonde data occurs below 5 km and is large in wet southern China, with a value of less than 1%. This result may be related to more humid conditions and super-refraction.

Highlights

Atmospheric temperature, pressure and humidity profiles are essential for meteorological research
Because a background atmospheric state is used in the retrieval of the temperature profile in COSMIC radio occultation (RO) [39,59] and the model temperature bias is large in the Qinghai-Tibet Plateau (QTP) area because of its complex topography [60], the limited ability of the background may contribute to the temperature difference between COSMIC and radiosonde data, especially in the QTP region
The COSMIC profiles of temperature, pressure, vapor pressure, and refractivity from 0 to 40 km are compared with radiosonde soundings in China between 2014 and 2015

Summary

Introduction

Atmospheric temperature, pressure and humidity profiles are essential for meteorological research. Accurate and stable long-term observations of the vertical structure of atmospheric temperature are crucial for climate change monitoring. Radiosondes are the only operational instruments that have provided these atmospheric profiles in the troposphere and lower stratosphere for more than three decades, and they have been widely used in climate studies [1,2,3,4]. The atmospheric temperature trends estimated from radiosonde observations are sensitive to the objective selection of radiosonde samples [5,6,7,8]. The selection of radiosonde samples can result in differences in temperature trends, as radiosonde observations are obtained with various types of radiosondes manufactured by different countries

Results

Discussion

Conclusion