%0 Journal Article
%T Seven Years¡¯ Observation of Mid-Upper Tropospheric Methane from Atmospheric Infrared Sounder
%A Xiaozhen Xiong
%A Chris Barnet
%A Eric Maddy
%A Jennifer Wei
%A Xingpin Liu
%A Thomas S. Pagano
%J Remote Sensing
%D 2010
%I MDPI AG
%R 10.3390/rs2112509
%X The Atmospheric Infrared Sounder (AIRS) on EOS/Aqua platform provides a measurement of global methane (CH4) in the mid-upper troposphere since September, 2002. As a thermal infrared sounder, the most sensitivity of AIRS to atmospheric CH4 is in the mid-upper troposphere with the degree of freedom of ~1.0. Validation of AIRS CH4 product versus thousands of aircraft profiles (convolved using the AIRS averaging kernels) demonstrates that its RMS error (RMSE) is mostly less than 1.5%, and its quality is pretty stable from 2003 to 2009. For scientific analysis of the spatial and temporal variation of mid-upper tropospheric CH4 (MUT-CH4) in the High Northern Hemisphere (HNH), it is more valuable to use the AIRS retrieved CH4 in a layer of about 100 hPa below tropopause (¡°Representative Layer¡±) than in a fixed pressure layer. Further analysis of deseasonalized time-series of AIRS CH4 in both a fixed pressure layer and the ¡°Representative Layer¡± of AIRS (only for the HNH) from 2003 to 2009 indicates that, similar to the CH4 in the marine boundary layer (MBL) that was found to increase in 2007¨C2008, MUT-CH4 was also observed to have a recent increase but the most significant increase occurred in 2008. MUT-CH4 continued to increase in 2009, especially in the HNH. Moreover, the trend of MUT-CH4 from 2006 to 2008 is lower than the trend of CH4 in the MBL by 30¨C40% in both the southern hemisphere and HNH. This delay for the MUT-CH4 increase of about one year than CH4 in the MBL as well as the smaller increase trend for MUT-CH4 suggest that surface emission is likely a major driver for the recent CH4 increase. It is also found that the seasonal cycle of MUT-CH4 is different from CH4 in the MBL due to the impact of transport, in addition to the surface emission and the photochemical loss.
%K methane
%K mid-upper troposphere
%K satellite
%K AIRS
%K trend
%K seasonal cycle £¿
%U http://www.mdpi.com/2072-4292/2/11/2509