Tellus (Tellus Dyn Meteorol Oceanogr)

Publications in this journal

• Article: Strong similarities between nighttime deposition velocities of carbonyl sulfide and molecular hydrogen inferred from semicontinuous atmospheric observations in Gif-sur-Yvette, Paris region.

  SAUVEUR BELVISO, MARTINA SCHMIDT, CAMILLE YVER, MICHEL RAMONET, VALERIE GROS, THOMAS LAUNOIS
  Tellus 09/2013;
• Source

  Available from: knmi.nl

  Article: Linear amplification of marginally neutral baroclinic waves

  Hylke de Vries, Martin Ehrendorfer
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  ABSTRACT: Baroclinic wave development is investigated for unstable parallel shear flows in the limit of vanishing normal-mode growth rate. This development is described in terms of the propagation and interaction mechanisms of two coherent structures, called counter-propagating Rossby waves (CRWs). It is shown that, in this limit of vanishing normal-mode growth rate, arbitrary initial conditions produce sustained linear amplification of the marginally neutral normal mode (mNM). This linear excitation of the mNM is subsequently interpreted in terms of a resonance phenomenon. Moreover, while the mathematical character of the normal-mode problem changes abruptly as the bifurcation point in the dispersion diagram is encountered and crossed, it is shown that from an initial-value viewpoint, this transition is smooth. Consequently, the resonance interpretation remains relevant (albeit for a finite time) for wavenumbers slightly different from the ones defining cut-off points. The results are further applied to a two-layer version of the classic Eady model in which the upper rigid lid has been replaced by a simple stratosphere.
  Tellus 04/2013;
• Article: Evaluation of the Earth Systems Research Laboratory’s global Observing System Simulation Experiment system

  Nikki Privé, Yuanfu Xie, John S. Woollen, Robert Atlas, Robbie E. Hood, Steven E. Koch
  Tellus 03/2013;
• Article: Assimilation of wind speed and direction observations: a new formulation and results from idealized experiments

  Xiang-Yu Huang, Feng Gao, Neil A. Jacobs, Hongli Wang
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  ABSTRACT: This article presents a new methodology for assimilating wind observations in their observed form of speed and direction, while taking into account both speed and direction error. It ensures the analysed speed and direction will be consistent with their background and observed values. The new formulation is implemented in the Weather Research and Forecasting Data Assimilation system, and idealised experiments are used to demonstrate the potential benefit. The results suggest that analyses from the new formulation are more reasonable when compared to the conventional methodology. The forecasts generated in these idealised experiments also demonstrate the value of this new formulation. Preliminary results from real data experiments are in general agreement with results presented here, and they will be reported in a following article.
  Tellus 01/2013;
• Article: Perturbing the potential vorticity field in mesoscale forecasts of two Mediterranean heavy precipitation events

  M. Vich, R. Romero, E. Richard, P. Arbogast, K. Maynard
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  ABSTRACT: In order to improve the quality of the Mediterranean high-impact weather (HIW) numerical predictions, this study proposes to modify the potential vorticity (PV) field of the model initial state, taking advantage of information provided by the water vapour (WV) channel of the METEOSAT-7 satellite. The implemented PV field modifications aim to reduce the mismatch between the upper-level PV features and the WV brightness temperatures guided by the known relation between these two fields (PV-WV technique). The PV-WV technique effectiveness is evaluated on two HIW events, and is also compared with two additional PV modification techniques from an earlier study. The chosen episodes occurred on 9–10 June 2000 and 9–10 October 2002 and produced heavy precipitation over both Spain and France. The main difference between these two episodes is found in the driving mechanism, a mesoscale cyclone for the June 2000 event and a larger low-pressure centre for the October 2002 case. The two additional PV modification techniques introduce perturbations along the zones highlighted by the MM5 adjoint model calculated sensitivity zones (PV-adjoint) and along the three-dimensional PV structure presenting the locally most intense values and gradients of the field (PV-gradient). A close examination of both case studies of the forecast rainfall fields and several objective verification indices show that the PV-WV technique performance exceeds the control (or non-perturbed) forecast skill while remaining inside the distribution obtained by both PV-gradient and PV-adjoint techniques. This PV-WV technique could be used to increase the ensemble spread introducing higher amplitude modifications. Thus, a more skilled ensemble prediction system could be built by taking advantage of the subjectivity inherent to this method (manual perturbations) and also of the uncertainty present in the initial state.
  Tellus 08/2012; 64:17224.
• Article: Simulation of surface temperature and ice cover of largenorthern lakes with 1-D models: a comparison withMODIS satellite data and in situ measurements

  Homa Kheyrollah Pour, Claude R. Duguay, Andrey Martynov, Laura C. Brown
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  ABSTRACT: Lake Surface Temperature (LST) and ice phenology were simulated for various points differing in depth on Great Slave Lake (GSL) and Great Bear Lake (GBL), two large lakes located in the Mackenzie River Basin in Canada’s Northwest Territories, using the one-dimensional (1-D) Freshwater Lake model (FLake) and the Canadian Lake Ice model (CLIMo) over the 2002-2010 period, forced with data from three weather stations (Yellowknife, Hay River and Deline). LST model results were compared to those derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Earth Observing System Terra and Aqua satellite platforms. Simulated ice thickness and freeze-up/break-up dates were also compared to in situ observations. Both models showed a good agreement with daily average MODIS LSTs on an annual basis (0.935 ≤ relative index of agreement ≤ 0.984 and 0.94 ≤ mean bias error ≤ 4.83). The absence of consideration of snow on lake ice in FLake was found to have a large impact on estimated ice thicknesses (25 cm thicker on average by the end of winter compared to in situ measurements; 9 cm thicker for CLIMo) and break-up dates (6 days earlier in comparison with in situ measurements; 3 days later for CLIMo). The overall agreement between the two models and MODIS LST products during both the open water and ice seasons was good. Remotely sensed data are a promising data source for assimilation into NWP models, as they provide the spatial coverage that is not captured by in situ data.
  Tellus 03/2012; 64.
• Article: Simulation of surface temperature and ice cover of largenorthern lakes with 1-D models: a comparison withMODIS satellite data and in situ measurements

  H. KHEYROLLAH POUR, C. R. DUGUAY, A. MARTYNOV, L. C. BROWN
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  ABSTRACT: Lake surface temperature (LST) and ice phenology were simulated for various points differing in depth on Great Slave Lake and Great Bear Lake, two large lakes located in the Mackenzie River Basin in Canada’s Northwest Territories, using the 1-D Freshwater Lake model (FLake) and the Canadian Lake Ice Model (CLIMo) over the 2002�2010 period, forced with data from three weather stations (Yellowknife, Hay River and Deline). LST model results were compared to those derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Earth Observing System Terra and Aqua satellite platforms. Simulated ice thickness and freeze-up/break-up dates were also compared to in situ observations. Both models showed a good agreement with daily average MODIS LSTs on an annual basis (0.935 < relative index of agreement < 0.984 and 0.94 < mean bias error < 4.83). The absence of consideration of snow on lake ice in FLake was found to have a large impact on estimated ice thicknesses (25 cm thicker on average by the end of winter compared to in situ measurements; 9 cm thicker for CLIMo) and break-up dates (6 d earlier in comparison with in situ measurements; 3 d later for CLIMo). The overall agreement between the two models and MODIS LST products during both the open water and ice seasons was good. Remotely sensed data are a promising data source for assimilation into numerical weather prediction models, as they provide the spatial coverage that is not captured by in situ data.
  Tellus 02/2012; 64.
• Article: Numerical modelling of snow and ice thicknesses in Lake Vanajavesi, Finland

  Yang, M. Leppäranta, B. Cheng and Z. Li
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  ABSTRACT: Snow and ice thermodynamics was simulated applying a one-dimensional model for an individual ice season 2008�2009 and for the climatological normal period 1971�2000. Meteorological data were used as the model input. The novel model features were advanced treatment of superimposed ice and turbulent heat fluxes, coupling of snow and ice layers and snow modelled from precipitation. The simulated snow, snow�ice and ice thickness showed good agreement with observations for 2008�2009. Modelled ice climatology was also reasonable, with 0.5 cm d�1 growth in December�March and 2 cm d�1 melting in April. Tuned heat flux from waterto ice was 0.5 W m�2. The diurnal weather cycle gave significant impact on ice thickness in spring. Ice climatology was highly sensitive to snow conditions. Surface temperature showed strong dependency on thickness of thin ice (B0.5 m), supporting the feasibility of thermal remote sensing and showing the importance of lake ice in numerical weather prediction. The lake ice season responded strongly to air temperature: a level increase by 1 or 58C decreased the mean length of the ice season by 13 or 78 d (from 152 d) and the thickness of ice by 6 or 22 cm (from 50 cm), respectively.
  Tellus 01/2012;
• Article: North Atlantic Variability Driven by Atmospheric and Oceanic Stochastic Forcing in a Simple Box Model

  Legatt, I.V. Polyakov, U.S. Bhatt, X. Zhang
  Tellus 01/2012;
• Article: Snow and ice on Bear Lake (Alaska) – sensitivity experiments with two lake ice models.

  Semmler, B. Cheng, Y. Yang, L. Rontu
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  ABSTRACT: Snow and ice thermodynamics of Bear Lake (Alaska) are investigated with a simple freshwater lake model (FLake) and a more complex snow and ice thermodynamic model (HIGHTSI). A number of sensitivity experiments have been carried out to investigate the influence of snow and ice parameters and of different complexity on the results. Simulation results are compared with observations from the Alaska Lake Ice and Snow Observatory Network. Adaptations of snow thermal and optical properties in FLake can largely improve accuracy of the results. Snow-to-ice transformation is important for HIGHTSI to calculate the total ice mass balance. The seasonal maximum ice depth is simulated in FLake with a bias of �0.04m and in HIGHTSI with no bias. Correlation coefficients between ice depth measurements and simulations are high (0.74 for FLake and 0.9 for HIGHTSI). The snow depth simulation can be improved by taking into account a variable snow density. Correlation coefficients for surface temperature are 0.72 for FLake and 0.81 for HIGHTSI. Overall, HIGHTSI gives slightly more accurate surface temperature than FLake probably due to the consideration of multiple snow and ice layers and the expensive iteration calculation procedure.
  Tellus 01/2012;