The MIPAS/Envisat climatology (2002–2012) of polar stratospheric cloud volume density profiles
<p>A global data set of vertical profiles of polar stratospheric cloud (PSC) volume density has been derived from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) space-borne infrared limb measurements between 2002 and 2012. To develop a well characterized and efficient ret...
Main Authors: | , , , , , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-10-01
|
Series: | Atmospheric Measurement Techniques |
Online Access: | https://www.atmos-meas-tech.net/11/5901/2018/amt-11-5901-2018.pdf |
Summary: | <p>A global data set of vertical profiles of polar stratospheric cloud (PSC)
volume density has been derived from Michelson Interferometer for Passive
Atmospheric Sounding (MIPAS) space-borne infrared limb measurements between
2002 and 2012. To develop a well characterized and efficient retrieval
scheme, systematic tests based on limb-radiance simulations for PSCs from in
situ balloon observations have been performed. The finally selected
wavenumber range was
831–832.5 cm<sup>−1</sup>. Optical constants of nitric acid trihydrate (NAT)
have been used to derive maximum and minimum profiles of volume density which
are compatible with MIPAS observations under the assumption of small,
non-scattering and larger, scattering PSC particles. These max/min profiles
deviate from their mean value at each altitude by about 40 %–45 %,
which is attributed as the maximum systematic error of the retrieval.
Further, the retrieved volume density profiles are characterized by a random
error due to instrumental noise of 0.02–0.05 µm<sup>3</sup> cm<sup>−3</sup>, a
detection limit of about 0.1–0.2 µm<sup>3</sup> cm<sup>−3</sup> and a vertical
resolution of around 3 km. Comparisons with coincident observations
by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on the
CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations)
satellite showed good agreement regarding the vertical profile shape.
Quantitatively, in the case of supercooled ternary solution (STS) PSCs, the
CALIOP dataset fits to the MIPAS retrievals obtained under the assumptions of
small particles. Unlike for STS and NAT, in the case of ice PSCs the MIPAS
retrievals are limited by the clouds becoming optically thick in the
limb-direction. In these cases, the MIPAS volume densities represent lower
limits. Among other interesting features, this climatology helps to study
quantitatively the on-set of PSC formation very near to the South Pole and
the large variability of the PSC volume densities between different Arctic
stratospheric winters.</p> |
---|---|
ISSN: | 1867-1381 1867-8548 |