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| Titel |
Mixing layer height retrievals by multichannel microwave radiometer observations |
| VerfasserIn |
D. Cimini, F. De Angelis, J.-C. Dupont, S. Pal, M. Haeffelin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 11 ; Nr. 6, no. 11 (2013-11-01), S.2941-2951 |
| Datensatznummer |
250085099
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| Publikation (Nr.) |
 copernicus.org/amt-6-2941-2013.pdf |
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| Zusammenfassung |
| The mixing layer height (MLH) is a key parameter for boundary layer studies,
including meteorology, air quality, and climate. MLH estimates are inferred
from in situ radiosonde measurements or remote sensing observations from
instruments like lidar, wind profiling radar, or sodar. Methods used to
estimate MLH from radiosonde profiles are also used with atmospheric
temperature and humidity profiles retrieved by microwave radiometers (MWR).
This paper proposes an alternative approach to estimate MLH from MWR data,
based on direct observations (brightness temperatures, Tb) instead of
retrieved profiles. To our knowledge, MLH estimates directly from Tb
observations have never been attempted before. The method consists of a
multivariate linear regression trained with an a priori set of collocated
MWR Tb observations (multifrequency and multi-angle) and MLH estimates from
a state-of-the-art lidar system. The proposed method was applied to a
7-month data set collected at a typical midlatitude site. Results show that
the method is able to follow both the diurnal cycle and the day-to-day
variability as suggested by the lidar measurements, and also it can detect
low MLH values that are below the full overlap limit (~200 m)
of the lidar system used. Statistics of the comparison between MWR- and
reference lidar-based MLH retrievals show mean difference within 10 m, root
mean square within 340 m, and correlation coefficient higher than 0.77. Monthly mean
analysis for daytime MLH from MWR, lidar, and radiosonde shows consistent
seasonal variability, peaking at ~1200–1400 m in June and
decreasing down to ~600 m in October. Conversely, nighttime
monthly mean MLH from all methods are within 300–500 m without any
significant seasonal variability. The proposed method provides results that
are more consistent with radiosonde estimates than MLH estimates from
MWR-retrieved profiles. MLH monthly mean values agree well within 1 standard deviation with
the bulk Richardson number method applied at radiosonde profiles at 11:00 and
23:00 UTC. The method described herewith operates continuously and is expected
to work with analogous performances for the entire diurnal cycle, except
during considerable precipitation, demonstrating new potential for
atmospheric observation by ground-based microwave radiometry. |
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