Information-based mid-upper tropospheric methane derived from Atmospheric Infrared Sounder (AIRS) and its validation
Item
Title (Dublin Core)
Information-based mid-upper tropospheric methane derived from Atmospheric Infrared Sounder (AIRS) and its validation
Description (Dublin Core)
Atmospheric Infrared Sounder (AIRS) measurements of methane (CH<sub>4</sub>) generally contain about 1.0 degree of freedom and are therefore dependent on a priori assumptions about the vertical methane distribution as well as the temperature lapse rate and the amount of moisture. Thus it requires that interpretation and/or analysis of the CH<sub>4</sub> spatial and temporal variation based on the AIRS retrievals need to use the averaging kernels (AK). To simplify the use of satellite retrieved products for scientific analysis, a method based on the information content of the retrievals is developed, in which the AIRS retrieved CH<sub>4</sub> in the layer from 50 to 250 hPa below the tropopause is used to characterize the mid-upper tropospheric CH<sub>4</sub> in the mid-high latitude regions. The basis of this method is that in the mid-high latitude regions the maximum sensitive layers of AIRS to CH<sub>4</sub> have a good correlation with the tropopause heights, and these layers are usually between 50 and 250 hPa below the tropopause. Validation using the aircraft measurements from NOAA/ESRL/GMD and the campaigns INTEX-A and -B indicated that the correlation of AIRS mid-upper tropospheric CH<sub>4</sub> with aircraft measurements is ~0.6–0.7, and its the bias and rms difference are less than ±1% and 1.2%, respectively. Further comparison of the CH<sub>4</sub> seasonal cycle indicated that the cycle from AIRS mid-upper tropospheric CH<sub>4</sub> is in a reasonable agreement with NOAA aircraft measurements. This method provides a simple way to use the thermal infrared sounders data to approximately analyze the spatial and temporal variation CH<sub>4</sub> in the upper free tropospere without referring the AK. This method is applicable to derive tropospheric CH<sub>4</sub> as well as other trace gases for any thermal infrared sensors.
Creator (Dublin Core)
Xiong, X.
Barnet, C.
Wei, J.
Maddy, E.
Date (Dublin Core)
2018-08-10
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acpd-9-16331-2009
https://acp.copernicus.org/preprints/acp-2009-378/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
