| 1. |
- Žagar, Nedjeljka
(författare)
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Assimilation of equatorial waves by line of sight wind observations
- 2004
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 61:15, s. 1877-1893
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the potential of line-of-sight (LOS) wind information from a spaceborne Doppler wind lidar to reduce uncertainties in the analysis fields of equatorial waves. The benefit of LOS winds is assessed by comparing their impact to that of a single wind component, full wind field information, and mass field data in three- and four-dimensional variational data assimilation. The dynamical framework consists of nonlinear shallow-water equations solved in spectral space and a background error term based on eigenmodes derived from linear equatorial wave theory. Based on observational evidence, simulated wave motion fields contain equatorial Kelvin, Rossby, mixed Rossby–gravity, and the lowest two modes of the westward-propagating inertio–gravity waves. The same dynamical structures are included, entirely or partially, into the background error covariance matrix for the multivariate analysis. The relative usefulness of LOS data is evaluated by carrying out “identical twin” observing system simulation experiments and assuming a perfect model. Results from the experiments involving a single observation or an imperfect background error covariance matrix illustrate that the assimilation increments due to LOS wind information rely more on the background error term specification than the full wind field information. This sensitivity is furthermore transferred to the balanced height field increments. However, all assimilation experiments suggest that LOS wind observations have a capability of being valuable and need supplemental information to the existing satellite mass field measurements in the Tropics. Although the new wind information is incomplete, it has a potential to provide reliable analysis of tropical wave motions when it is used together with the height data.
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| 2. |
- Johansson, C, et al.
(författare)
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Critical test of the validity of Monin-Obukhov similarity during convective conditions
- 2001
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 58:12, s. 1549-1566
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Tidskriftsartikel (refereegranskat)abstract
- A recent study of convective boundary layer characteristics performed with large eddy simulation technique (LES) has demonstrated unexpected influence of the depth of the boundary layer on surface layer characteristics. The present study tests some of the
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| 3. |
- Lacorata, G., et al.
(författare)
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Evidence for a k(-5/3) spectrum from the EOLE Lagrangian balloons in the low stratosphere
- 2004
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Ingår i: Journal of the Atmospheric Sciences. - 0022-4928 .- 1520-0469. ; 61:23, s. 2936-2942
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Tidskriftsartikel (refereegranskat)abstract
- The EOLE experiment is revisited to study turbulent processes in the lower stratosphere circulation from a Lagrangian viewpoint and to resolve a discrepancy on the slope of the atmospheric energy spectrum between the work of Morel and Larcheveque and recent studies using aircraft data. Relative dispersion of balloon pairs is studied by calculating the finite-scale Lyapunov exponent, an exit-time-based technique that is particularly efficient in cases in which processes with different spatial scales are interfering. The main goal is to reconciliate the EOLE dataset with recent studies supporting a k(-5/3) energy spectrum in the 100-1000-km range. The results also show exponential separation at smaller scales, with a characteristic time of order 1 day, and agree with the standard diffusion of about 10(7) m(2) s(-1) at large scales. A remaining question is the origin of a k(-5/3) spectrum in the mesoscale range between 100 and 1000 km.
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| 4. |
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| 5. |
- Strom, L, et al.
(författare)
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Observed dynamics of coastal flow at Cape Mendocino during Coastal Waves 1996
- 2001
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Ingår i: Journal of the Atmospheric Sciences. - : AMER METEOROLOGICAL SOC. - 0022-4928 .- 1520-0469. ; 58:9, s. 953-977
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Tidskriftsartikel (refereegranskat)abstract
- Airborne in situ and remote meteorological measurements from around Cape Mendocino, California, sampled during the Coastal Waves 1996 field program are analyzed for three different days: 7, 12, and 26 June 1996. Two days conformed to typical summertime co
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| 6. |
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| 7. |
- Tjernstrom, Michael, et al.
(författare)
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Simulations of supercritical flow around points and gapes in a coastal atmosphere
- 2000
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Ingår i: Journal of the Atmospheric Sciences. - : AMER METEOROLOGICAL SOC. - 0022-4928 .- 1520-0469. ; 57:1, s. 108-135
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Tidskriftsartikel (refereegranskat)abstract
- Fully 3D nonlinear model simulations for supercritical flow along locations at the California coast, at Cape Mendocino, and Point Sur,are presented the model results are objectively and subjectively verified against measurements from the Coastal Waves 199
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| 8. |
- Zilitinkevich, SS, et al.
(författare)
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Scaling reasoning and field data on the sea surface roughness lengths for scalars
- 2001
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Ingår i: Journal of the Atmospheric Sciences. - : AMER METEOROLOGICAL SOC. - 0022-4928 .- 1520-0469. ; 58:3, s. 320-325
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Tidskriftsartikel (refereegranskat)abstract
- The heat and mass transfer over the sea is considered in terms of the sea surface roughness lengths for scalars, z(OT) for potential temperature theta, and z(Oq) for specific humidity q, or alternatively, in terms of the roughness-layer scalar increments,
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