Validation and data characteristics of nitrous oxide and methane profiles observed by the Improved Limb Atmospheric Spectrometer (ILAS) and processed with the Version 5.20 algorithm

Abstract

Vertical profiles of nitrous oxide and methane at high latitudes (57–72°N; 64–89°S) were observed by the Improved Limb Atmospheric Spectrometer (ILAS) solar occultation sensor aboard Advanced Earth Observing Satellite. These measurements were made continuously from November 1996 through June 1997 with some additional periods in September–October 1996. A validation study of the nitrous oxide and methane data processed with the Version 5.20 ILAS retrieval algorithm is presented in this paper. Comparisons are made with (1) nitrous oxide and methane obtained by the ILAS validation balloon campaigns at Kiruna, Sweden, and at Fairbanks, Alaska, in the Arctic; (2) nitrous oxide and methane by the Photochemistry of Ozone Loss in the Arctic Region in Summer aircraft campaign in the Arctic; (3) nitrous oxide by the ground‐based spectroscopic measurements and by the aircraft‐based remote sensing measurements in the Arctic; and (4) methane by satellite measurements of the Version 19 Halogen Occultation Experiment in the Arctic and Antarctic. Comparisons of ILAS nitrous oxide and methane with Upper Atmosphere Research Satellite Reference Atmosphere data are also made. The results of the comparisons and additional ILAS internal consistency analyses are as follows: (1) the uncertainty of ILAS nitrous oxide is better than 10% over 10–30 km in altitude, and is larger than 50% over 30–40 km, which is comparable to the expected total errors of the ILAS measurements; (2) the uncertainty of ILAS methane is better than 10% over 10–50 km, except for 15–30 km in winter with positive biases exceeding 20%, which is smaller than or comparable to the expected total errors of the ILAS measurements (the quality of ILAS methane in the polar lower stratosphere is better in summer than in winter). In summary, the characteristics of ILAS measurements, i.e., high sampling frequency in polar latitudes with high vertical resolution, along with the good quality of ILAS Version 5.20 nitrous oxide for 10–40 km and the good quality of ILAS Version 5.20 methane for 10–50 km except for 15–30 km in winter, make the ILAS nitrous oxide and methane data set valuable for scientific study of various polar stratospheric phenomena.

Validation of ACE-FTS N<sub>2</sub>O measurements

“…The Improved Limb Atmospheric Spectrometer (ILAS) and ILAS-II instruments on the Advanced Earth Observing Satellite (ADEOS) and ADEOS-II, respectively, both measured N 2 O using infrared solar occultation. ILAS made measurements from September 1996 to June 1997 (Kanzawa et al, 2003;Khosrawi et al, 2004), while ILAS-II operated for eight months in 2003 (Ejiri et al, 2006;Khosrawi et al, 2006).…”

Retrieval of nitrous oxide from Atmospheric Infrared Sounder: Characterization and validation

“…Two types of techniques are used, in general. One uses solar occultation measurement, which includes the Cryogenic Limb Array Etalon Spectrometer, the Improved SAMS, and the Halogen Occultation Experiment on board the Upper Atmosphere Research Satellite [e.g., Roche et al, 1996], and the Improved Limb Atmospheric Spectrometer (ILAS) and ILAS-II [Ejiri et al, 2006], on board the Advanced Earth Observing Satellite (ADEOS) and ADEOS-II [Kanzawa et al, 2003]. Another type uses the limb emission measurement, which includes the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Sun-synchronous polar-orbiting European Environmental Satellite (Envisat) [Payan et al, 2009], the submillimeter radiometer on board the Odin satellite [Urban et al, 2005], the Microwave Limb Sounder (MLS) on board the NASA's Earth Observing System (EOS) Aura satellite [Lambert et al, 2007], and the Atmospheric Chemistry Experiment (ACE) fourier transform spectrometer (ACE-FTS) [Strong et al, 2008].…”

SCIAMACHY validation by aircraft remote sensing: design, execution, and first measurement results of the SCIA-VALUE mission

“…The flexibility of the aircraft allows to investigate small and medium scale spatial variations in the stratosphere closing the gap between locally limited balloon measurements and synoptic satellite data. The high stability and reproducibility of the measurements performed with ASUR make this technique well suited for validation campaigns of spaceborne sensors as successfully done for UARS (MLS, HALOE) ATLAS (MAS), ERS-2 (GOME) and ADEOS (ILAS) (Crewell et al, 1995;Sugita et al, 2002;Kanzawa et al, 2003).…”

“…It is also apparent from Table 1 that in most cases in-situ instruments were used. Only very few examples of validation activities are reported in the literature where remote sensing instruments have been deployed on aircraft such as the NASA DC-8 , the DLR Falcon or the M55-Geophysika (Crewell et al, 1995;Englert et al, 2000;Feist et al, 2000;Schoeberl et al, 2002;Sugita et al, 2002;Kanzawa et al, 2003;Lumpe et al, 2003;Fix et al, 2003;Blom et al, 2003).…”