Taklimakan Desert nocturnal low-level jet: climatology and dust activity
While nocturnal low-level jets (NLLJs) occur frequently in many parts of the world, the occurrence and other detailed characteristics of NLLJs over the Taklimakan Desert (TD) are not well known. This paper presents a climatology of NLLJs and coincident dust over the TD by analyzing multi-year ERA...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/7773/2016/acp-16-7773-2016.pdf |
| Summary: | While nocturnal low-level jets (NLLJs) occur frequently in many parts of the
world, the occurrence and other detailed characteristics of NLLJs over the
Taklimakan Desert (TD) are not well known. This paper presents a climatology
of NLLJs and coincident dust over the TD by analyzing multi-year ERA-Interim
reanalysis and satellite observations. It is found that the ERA-Interim
dataset can capture the NLLJs' features well by comparison with radiosonde
data from two surface sites. The NLLJs occur in more than 60 % of nights,
which are primarily easterly to east-northeasterly. They typically appear at
100 to 400 m above the surface with a speed of 4 to 10 m s<sup>−1</sup>. Most
NLLJs are located above the nocturnal inversion during the warm season, while
they are embedded in the inversion layer during the cold season. NLLJs above
the inversion have a strong annual cycle with a maximum frequency in August.
We also quantify the convective boundary layer (CBL) height and construct an
index to measure the magnitude of the momentum in the CBL. We find that the
magnitude of momentum in the lower atmosphere from the top of the surface
layer to the top of mixed layer is larger for NLLJ cases than for non-NLLJ
cases, and in the warm season the downward momentum transfer process is more
intense and rapid. The winds below the NLLJ core to the desert surface gain
strength in summer and autumn, and these summer and autumn winds are
coincident with an enhancement of aerosol optical depth. This indicates that
the NLLJ is an important mechanism for dust activity and transport during the
warm season over the Taklimakan. |
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| ISSN: | 1680-7316 1680-7324 |