Measurements of mid-stratospheric formaldehyde from the Odin/SMR instrument

Abstract

Measurements of mid-stratospheric formaldehyde (H2CO) have been obtained from the limb-viewing sub-millimeter radiometer (SMR) instrument aboard the Odin satellite. The analysis is based upon the only weak (808→707) rotational transition line of H2CO that can be measured by Odin/SMR at 576.7083150 GHz in the band dedicated to the measurement of carbon monoxide (CO). The signal-to-noise ratio is increased by averaging about 1000 spectra within 2-km width vertical layers in the stratosphere over periods from 1 to 7 days and within 3 latitude bands: Southern Hemisphere (90°S–45°S), tropics (30°S–30°N), and Northern Hemisphere (45°N–90°N). The faint H2CO line can then be retrieved using the standard scientific ground-segment developed for the Odin/SMR measurements. The mid-stratospheric H2CO shows maxima in the tropics for every period considered (January 2006, February 2005, March 2005, and September 2005). The spring-time extra-tropical mid-stratospheric H2CO is more intense than the fall-time extra-tropical amounts. The simulations from the three-dimensional chemical-transport model Reprobus satisfactorily show these general features

Retrieval of global upper tropospheric and stratospheric formaldehyde (H<sub>2</sub>CO) distributions from high-resolution MIPAS-Envisat spectra

“…Table 2 (Lefèvre et al, 1994;Ricaud et al, 2007). For latitudes south of 45 • S, MIPAS and Odin-SMR values agree within the MIPAS standard error (Table 2, first row).…”

“…In order to put our results into the context of previously published measurements of H 2 CO, we compare the MIPAS results with those from ACE-FTS (Coheur et al, 2007) and Odin-SMR (Ricaud et al, 2007), as well as REPROBUS model calculations (Lefèvre et al, 1994;Ricaud et al, 2007). While this comparison is not meant as quantitative validation, it still gives an idea of the general agreement between the measurements.…”

“…Global distributions of H 2 CO columns have been derived with the GOME (Global Ozone Monitoring Experiment) instrument (Burrows et al, 1999;Chance et al, 2000) which are dominated by the tropospheric signal. Vertically resolved satellite measurements of H 2 CO have been made recently with the sub-millimeter radiometer (SMR) aboard the Odin satellite (Ricaud et al, 2007), with an altitude region of about 35 to 50 km, and with the Atmospheric Chemistry Experiment -Fourier Transform Spectrometer (ACE-FTS) (Coheur et al, 2007) with focus on the upper tropospheric and lower stratospheric (UTLS) region. In the following we show that MIPAS has the potential to provide day and night profile information of formaldehyde from the upper troposphere to the stratopause on a global scale.…”

“…The formaldehyde analysis is based on a weak rotational transition line at 576.7083150 GHz (Ricaud et al, 2007). The signal-to-noise ratio is increased by averaging about 1000 spectra within vertical layers of 2 km width leading to profile retrieval in the upper stratosphere.…”

Global upper-tropospheric formaldehyde: seasonal cycles observed by the ACE-FTS satellite instrument

“…Up to now, satellite measurements of HCHO were performed either by UV-visible nadir sounders (e.g., GOME, SCIA-MACHY, OMI) that provide tropospheric columns mostly sensitive to the lower troposphere (e.g., Palmer et al, 2001;Wittrock et al, 2006; or by limb viewers (e.g., MIPAS, SMR) that provide profiles but mainly limited to the stratosphere (Steck et al, 2008;Ricaud et al, 2007). Measurements of formaldehyde profiles in the upper troposphere from the ACE-FTS therefore represent a unique data set for investigating the seasonal variation in this altitude region, with a more specific focus on the mid and high latitudes (better covered by the instrument).…”