Case studies of the impact of orbital sampling on stratospheric trend detection and derivation of tropical vertical velocities: solar occultation vs. limb emission sounding
Other literature type
Millán, Luis F.
Livesey, Nathaniel J.
Santee, Michelle L.
Neu, Jessica L.
Manney, Gloria L.
Fuller, Ryan A.
arxiv: Physics::Atmospheric and Oceanic Physics | Astrophysics::Earth and Planetary Astrophysics
This study investigates the representativeness of two types of orbital
sampling applied to stratospheric temperature and trace gas fields. Model
fields are sampled using real sampling patterns from the Aura Microwave Limb
Sounder (MLS), the HALogen Occultation Experiment (HALOE) and the Atmospheric
Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The MLS
sampling acts as a proxy for a dense uniform sampling pattern typical of limb
emission sounders, while HALOE and ACE-FTS represent coarse nonuniform
sampling patterns characteristic of solar occultation instruments. First,
this study revisits the impact of sampling patterns in terms of the sampling
bias, as previous studies have done. Then, it quantifies the impact of
different sampling patterns on the estimation of trends and their associated
detectability. In general, we find that coarse nonuniform sampling patterns
may introduce non-negligible errors in the inferred magnitude of temperature
and trace gas trends and necessitate considerably longer records for their
definitive detection. Lastly, we explore the impact of these sampling
patterns on tropical vertical velocities derived from stratospheric water
vapor measurements. We find that coarse nonuniform sampling may lead to a
biased depiction of the tropical vertical velocities and, hence, to a biased
estimation of the impact of the mechanisms that modulate these velocities.
These case studies suggest that dense uniform sampling such as that available
from limb emission sounders provides much greater fidelity in detecting
signals of stratospheric change (for example, fingerprints of greenhouse gas
warming and stratospheric ozone recovery) than coarse nonuniform sampling
such as that of solar occultation instruments.