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Continuous time series of catchment-averaged sensible heat flux from a large aperture scintillometer: efficient estimation of stability conditions and importance of fluxes under stable conditions

Bruno Samain UGent, Willem Defloor and Valentijn Pauwels UGent (2012) JOURNAL OF HYDROMETEOROLOGY. 13(2). p.423-442
abstract
A large aperture scintillometer (LAS) observes the intensity of the atmospheric turbulence across large distances, which is related to the path-averaged sensible heat flux H. In this paper, two problems in the derivation of continuous series of H from LAS data are investigated and the importance of nighttime H fluxes is assessed. First, as an LAS is unable to determine the sign of H, the transition from unstable to stable conditions is evaluated in order to make continuous H series. Therefore, different algorithms to judge the atmospheric stability for an LAS installed over a distance of 9.5 km have been tested. The diurnal cycle of the refractive index structure parameter, C-N(2), results in the best suitable, operational algorithm. A second issue is the humidity correction for LAS data, which is performed by using the Bowen ratio (beta). As beta is taken from ground-based measurements with data gaps, the number of resulting H values is reduced. Not including this humidity correction results in a marginal error in H, but increases the completeness of the H series. Applying these conclusions to the 2-yr time series of the LAS results in an almost-continuous H time series. As the majority of the time steps has been found to be under stable conditions, there is a clear impact of H-stable on H-24h-the 24-h average of H. For stable conditions, H-stable values are mostly negative, and hence lower than the H - 0 W m(-2) assumption as mostly adopted. For months where stable conditions prevail (winter), H-24h is overestimated using this assumption, and calculation of H-stable is recommended.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
HETEROGENEOUS LAND-SURFACE, INDEX-STRUCTURE PARAMETER, REFRACTIVE-INDEX, EDDY-COVARIANCE, WATER-VAPOR, BOWEN-RATIO, AREAS, LAYER, FIELD, SCINTILLATION
journal title
JOURNAL OF HYDROMETEOROLOGY
J. Hydrometeorol.
volume
13
issue
2
pages
423 - 442
Web of Science type
Article
Web of Science id
000302483900003
JCR category
METEOROLOGY & ATMOSPHERIC SCIENCES
JCR impact factor
3.273 (2012)
JCR rank
14/73 (2012)
JCR quartile
1 (2012)
ISSN
1525-755X
DOI
10.1175/JHM-D-11-030.1
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
2098268
handle
http://hdl.handle.net/1854/LU-2098268
date created
2012-05-03 14:42:14
date last changed
2012-05-04 08:48:20
@article{2098268,
  abstract     = {A large aperture scintillometer (LAS) observes the intensity of the atmospheric turbulence across large distances, which is related to the path-averaged sensible heat flux H. In this paper, two problems in the derivation of continuous series of H from LAS data are investigated and the importance of nighttime H fluxes is assessed. First, as an LAS is unable to determine the sign of H, the transition from unstable to stable conditions is evaluated in order to make continuous H series. Therefore, different algorithms to judge the atmospheric stability for an LAS installed over a distance of 9.5 km have been tested. The diurnal cycle of the refractive index structure parameter, C-N(2), results in the best suitable, operational algorithm. A second issue is the humidity correction for LAS data, which is performed by using the Bowen ratio (beta). As beta is taken from ground-based measurements with data gaps, the number of resulting H values is reduced. Not including this humidity correction results in a marginal error in H, but increases the completeness of the H series. Applying these conclusions to the 2-yr time series of the LAS results in an almost-continuous H time series. As the majority of the time steps has been found to be under stable conditions, there is a clear impact of H-stable on H-24h-the 24-h average of H. For stable conditions, H-stable values are mostly negative, and hence lower than the H - 0 W m(-2) assumption as mostly adopted. For months where stable conditions prevail (winter), H-24h is overestimated using this assumption, and calculation of H-stable is recommended.},
  author       = {Samain, Bruno and Defloor, Willem and Pauwels, Valentijn},
  issn         = {1525-755X},
  journal      = {JOURNAL OF HYDROMETEOROLOGY},
  keyword      = {HETEROGENEOUS LAND-SURFACE,INDEX-STRUCTURE PARAMETER,REFRACTIVE-INDEX,EDDY-COVARIANCE,WATER-VAPOR,BOWEN-RATIO,AREAS,LAYER,FIELD,SCINTILLATION},
  language     = {eng},
  number       = {2},
  pages        = {423--442},
  title        = {Continuous time series of catchment-averaged sensible heat flux from a large aperture scintillometer: ef\unmatched{fb01}cient estimation of stability conditions and importance of fluxes under stable conditions},
  url          = {http://dx.doi.org/10.1175/JHM-D-11-030.1},
  volume       = {13},
  year         = {2012},
}

Chicago
Samain, Bruno, Willem Defloor, and Valentijn Pauwels. 2012. “Continuous Time Series of Catchment-averaged Sensible Heat Flux from a Large Aperture Scintillometer: Efficient Estimation of Stability Conditions and Importance of Fluxes Under Stable Conditions.” Journal of Hydrometeorology 13 (2): 423–442.
APA
Samain, B., Defloor, W., & Pauwels, V. (2012). Continuous time series of catchment-averaged sensible heat flux from a large aperture scintillometer: efficient estimation of stability conditions and importance of fluxes under stable conditions. JOURNAL OF HYDROMETEOROLOGY, 13(2), 423–442.
Vancouver
1.
Samain B, Defloor W, Pauwels V. Continuous time series of catchment-averaged sensible heat flux from a large aperture scintillometer: efficient estimation of stability conditions and importance of fluxes under stable conditions. JOURNAL OF HYDROMETEOROLOGY. 2012;13(2):423–42.
MLA
Samain, Bruno, Willem Defloor, and Valentijn Pauwels. “Continuous Time Series of Catchment-averaged Sensible Heat Flux from a Large Aperture Scintillometer: Efficient Estimation of Stability Conditions and Importance of Fluxes Under Stable Conditions.” JOURNAL OF HYDROMETEOROLOGY 13.2 (2012): 423–442. Print.