Assimilation and validation

Martin Juckes, BADC

ACE-FTSACE-FTS is the main instrument on SCISAT-1. It is

a high spectral resolution (0.02 cm-1) Fourier Transform Spectrometer (FTS) operating from 2.2 to 13.3 µm (750-4400 cm-1) with a Michelson interferometer that was custom designed and built by ABB-Bomem.

Background: MIPAS vs. ACE-FTS

Wang et al. (2007; ACP) show mean differences between ACE-FTS and MIPAS HNO3 of around 0.5ppbv, standard deviation around 1.

Wang et al. – MIPAS vs. Odin

The MIPAS – Odin differences are generally larger than the MIPAS – ACEFTS differences.

Validation of assimilated fields

Blue: HIRDLS, Green: ACE-FTS, Orange: MLS-AURA

500K

Mean differences from assimilaton and standard deviation in 6 latitude bands and 12 months.

650K and 850K

Equivalent latitude means

(a) (b)

(a) HIRDLS, (b) MLS-AURA

(a) (b)

(a) HIRDLS, (b) MLS-AURA

Odin SMR (Orsolini et al., 2008, ACPD)

N. hemisphere, 650K

HIRDLS, HNO3 ECMWF, PV MLS-AURA, HNO3

Closing remarks

• Validation against ACE-FTS gives reasonable results: detailed analysis still needs to be done

• The annual cycle is markedly different from that obtained by Orsolini et al. from ODIN SMR data, but consistent with MLS-AURA

• Evolution of large scale structures broadly consistent with potential vorticity evolution