Infra-red sensing for the Retrieval of Tropospheric Composition from Space

A contribution to ACCENT-TROPOSAT-2, Task Group 1

John  J. Remedios

EOS, Department of Physics, University of Leicester, Leicester, LE1 7RH, UK
Tel.: +44 (0) 116 223 1319
Fax : +44 (0) 116 252 2464

The University of Leicester EOS group has been involved in infra-red remote sensing since its inception in 1993. Current work in infra-red remote sensing of the atmosphere has two main study areas: 1) characteristics of CO profiles from MOPITT; 2) retrieval of upper tropospheric composition from MIPAS, particularly the detection of organic compounds. The work in the timeframe of AT2 will focus on:

the characterisation of day–night differences in MOPITT data for CO to identify surface sources and higher altitude inter-continental transport: and

the detection and retrieval characterisation of trace gases, such as organics, HNO3, CO and O3 from MIPAS data for the mid-to upper troposphere.

Activity 1 - The characterisation of day–night differences in MOPITT data for CO to identify surface sources and higher altitude inter-continental transport.

The objectives of this work are to investigate the increased altitude sensitivity of day – night differences to differentiate the altitude region in which CO enhancements can appear. Although the vertical resolution of MOPITT is relatively low and it has limited sensitivity to the lowermost troposphere, differencing of day and night MOPITT data can have enhanced sensitivity to the surface or to the upper atmosphere. The reason lies in the differences between day and night averaging kernels for the “surface” retrieval level. The day averaging kernels for the surface tend to have stronger sensitivities to the lowermost troposphere where the surface temperature is highest, whereas the night averaging kernels for the surface tend to be more responsive to middle and upper tropospheric CO changes; high temperature surfaces tend to have strong diurnal heating. We will investigate how these differences can be used to investigate CO enhancements and variability in the troposphere. We will also include the additional information in MOPITT retrieval levels directly providing information for the upper troposphere. Already we have indications that day-night differencing can reveal low altitude industrial pollution (Houston, East Asia) and biomass burning (Africa) as well as high altitude CO transport (see Figure 1).

 Figure 1 – Monthly mean of MOPITT day-night “surface” concentrations for January 2001. Strong positive enhancements indicate high CO in the lowermost troposphere. Negative values  may indicate high altitude (mid- to upper troposphere enhancements of CO).

Activity 2 - The detection and retrieval characterisation of trace gases, such as organics, HNO3, CO and O3 from MIPAS data for the mid-to upper troposphere.

The MIPAS instrument is the first limb sounding emission spectrometer to routinely sound to mid-troposphere altitudes on a routine basis. The nominal scan pattern reaches down to 6 km at the bottom of its range. The MIPAS data, with its high spectral resolution of 0.025 cm-1 unapodised, therefore allow us an unprecedented insight into vertical variations of tropospheric composition. However, the data must first be cloud cleared and trace gas retrievals tested for residual cloud/aerosol effects. In this study, we aim to characterise MIPAS observations (detection limits, sensitivity, errors) in the upper troposphere for four groups of compounds: (a) organics, (b) HNO3, (c) CO, and (d) O3. Such datasets will be invaluable for modellers working in other task groups and may help to identify signatures of biomass burning and pollutant transport in the upper troposphere.

Time Schedule

 

2004

2005

2006

2007

2008

Activity 1

****

***

**

*

*

Activity 2

**

****

****

**

*

Approximate manpower and cost

 

2004

2005

2006

2007

2008

Personnel / man years

1.0

1.0

1.0

0.5

0.25

Yearly Cost (kECU)

15,000

15,000

15,000

7,500

3,750

 Likely Funding Agencies

CEC, UK national funding bodies (e.g. NERC, EPSRC, BNSC) and ESA

Co-workers

Nigel Richards, Alison Waterfall  and Harjinder Sembhi        

          

 

 


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