Characteristics of UT/ls carbon monoxide Intraseasonal oscillations and their impact factors over the Tibetan plateau and its adjacent areas in summer

Abstract

The study presented herein investigated the main characteristics of carbon monoxide intraseasonal variability and evaluated its possible impact factors using the upper troposphere and lower stratosphere (UT/LS) Aura Microwave Limb Sounder (MLS) observations over Tibetan Plateau and its adjacent areas in summer (June to August) of 2005 and 2006. Observations show a persistent constituent extreme extending up into the UT/LS throughout summer, as well as a temporally reversed phase variation between the carbon monoxide and ozone in UT/LS. The intraseasonal oscillations (ISOs) of carbon monoxide during summer are investigated by using methods of wavelet and band pass filter analysis. It is found that ISOs over the Tibetan Plateau have periods of 10 to 20 days and 30 to 60 days. The former mainly appeared in upper troposphere while the latter in lower stratosphere. Further analysis shows that these two periods of ISOs in UT/LS are mainly in phase to the activities of convection over the south of the plateau and the variation of South Asia High, respectively. The above two factors and their dynamical coupling may be responsible for the tracer ISOs at different levels.