The relationship between low-level cloud amount and its proxies over the globe by cloud type
<p>We extend upon previous work to examine the relationship between low-level cloud amount (LCA) and various proxies for LCA – estimated low-level cloud fraction (ELF), lower tropospheric stability (LTS), and estimated inversion strength (EIS) – by low-level cloud type (CL) over the globe usin...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-03-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/20/3041/2020/acp-20-3041-2020.pdf |
| Summary: | <p>We extend upon previous work to examine the relationship between
low-level cloud amount (LCA) and various proxies for LCA – estimated
low-level cloud fraction (ELF), lower tropospheric stability (LTS),
and estimated inversion strength (EIS) – by low-level cloud type
(CL) over the globe using individual surface and upper-air
observations. Individual CL has its own distinct environmental
structure, and therefore our extended analysis by CL can provide
insights into the strengths and weaknesses of various proxies and help to
improve them.</p>
<p>Overall, ELF performs better than LTS and EIS in diagnosing the variations
in LCA among various CLs, indicating that a previously identified
superior performance of ELF compared to LTS and EIS as a global proxy for LCA comes
from its realistic correlations with various CLs rather than with
a specific CL. However, ELF, LTS, and EIS have a problem in
diagnosing the changes in LCA when noCL (no low-level cloud) is
reported and also when Cu (cumulus) is reported over deserts where
background stratus does not exist. This incorrect diagnosis of noCL
as a cloudy condition is more clearly seen in the analysis of
individual CL frequencies binned by proxy values. If noCL is excluded,
ELF, LTS, and EIS have good inter-CL correlations with the
amount when present (AWP) of individual CLs. In the future, an advanced
ELF needs to be formulated to deal with the decrease in LCA when the
inversion base height is lower than the lifting condensation level to
diagnose cumulus updraft fraction, as well as the amount of stratiform
clouds and detrained cumulus, and to parameterize the scale height as
a function of appropriate environmental variables.</p> |
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| ISSN: | 1680-7316 1680-7324 |