 |
| Titel |
The feasibility of water vapor sounding of the cloudy boundary layer using a differential absorption radar technique |
| VerfasserIn |
M. D. Lebsock, K. Suzuki, L. F. Millán, P. M. Kalmus |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 9 ; Nr. 8, no. 9 (2015-09-08), S.3631-3645 |
| Datensatznummer |
250116570
|
| Publikation (Nr.) |
 copernicus.org/amt-8-3631-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| The feasibility of differential absorption radar (DAR) for the spaceborne
remote profiling of water vapor within the cloudy boundary layer is assessed
by applying a radar instrument simulator to large eddy simulations (LES).
Frequencies near the 183 GHz water vapor absorption line attenuate too
strongly to penetrate the large vapor concentrations that are ubiquitous in
the boundary layer. However it is shown that lower frequencies between 140
and 170 GHz in the water vapor absorption continuum and on the wings of the
absorption line, which are attenuated less efficiently than those near the
line center, still have sufficient spectral variation of gaseous attenuation
to perform sounding. The high resolution LES allow for assessment of the
potential uncertainty in the method due to natural variability in
thermodynamic and dynamic variables on scales smaller than the instrument
field of view. The (160, 170) GHz frequency pair is suggested to best
maximize signal for vapor profiling while minimizing noise due to undesired
spectral variation in the target extinction properties. Precision in the
derived water vapor is quantified as a function of the range resolution and
the instrument precision. Assuming an observational spatial scale of 500 m
vertical and 750 m full width at half maximum (FWHM) horizontal, measurement
precision better that 1 g m−3 is achievable for stratocumulus scenes and
3 g m−3 for cumulus scenes given precision in radar reflectivity of 0.16 dBZ. Expected precision in the column water vapor (CWV) is achievable
between 0.5 and 2 kg m−2 on these same spatial scales. Sampling
efficiency is quantified as a function of radar sensitivity. Mean biases in
CWV due to natural variability in the target extinction properties do not
exceed 0.25 kg m−2. Potential biases due to uncertainty in the
temperature and pressure profile are negligible relative to those resulting
from natural variability. Assuming a −35 dBZ minimum detectable signal,
40 %(21.9 %) of stratocumulus(cumulus) atmospheric boundary layer range
bins would be sampled. Simulated surface reflectivities are always greater
than −5 dBZ, which implies the DAR technique could provide near spatially
continuous observation of the CWV in subtropical boundary layers at a
spatial resolution better than 1 km. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|