A Simple Method Based on Routine Observations to Nowcast Down-Valley Flows in Shallow, Narrow Valleys

Duine, Gert‐Jan; Hedde, Thierry; Roubin, Pierre; Durand, Pierre

doi:10.1175/jamc-d-15-0274.1

Cited by 10 publications

(21 citation statements)

References 29 publications

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“…The aim of this study is to build an ANN, using simulated variables (from operational WRF forecasts outputs) as predictors and observations as ground truth (temporary observations used to train the ANN). This study advances the nowcasting work of Duine et al [31] and Dupuy et al [22] by using a combined ANN and numerical simulation technique to forecast local winds by correcting mesoscale simulations.…”

Section: Introductionmentioning

confidence: 78%

“…Therefore, our forecast evaluation mainly focuses on wind. Nevertheless, being aware that stability is the main trigger of down-valley winds [31], the atmospheric stratification is evaluated as well.…”

Section: Forecast Evaluationmentioning

confidence: 99%

“…Duine et al [31] performed a first step toward downscaling to local winds on the Cadarache site. They developed a method for nowcasting the occurrence of down-valley winds which form under stable conditions in the small Cadarache valley using observations from the KASCADE campaign.…”

Section: Introductionmentioning

confidence: 99%

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Valley Winds at the Local Scale: Correcting Routine Weather Forecast Using Artificial Neural Networks

et al. 2021

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In regions of complex topography, local flows are difficult to forecast on a routine basis, especially in stable conditions, due to the coarse resolution of operational models. The Cadarache valley (southeastern France) features this sort of complex topography. The Weather Research and Forecasting (WRF) model is run daily to forecast the weather in this region with a horizontal resolution of 3 km. Such a resolution cannot resolve all topography details of the small Cadarache valley, and therefore its local wind patterns. Other variables, however, that are less dependent on the subgrid topography, are satisfactorily forecasted, and used as inputs to an artificial neural network (ANN) designed to reproduce wind observations inside the valley from WRF forecasts. A variable selection procedure identified 5 key input variables that best drive the ANN. With respect to the WRF output, the ANN significantly improves forecasted low-level winds, both for speed and direction. This study demonstrates the potential for the ANN technique to be used as a correcting tool to forecast weather conditions at the local scale when numerical modeling is performed at a resolution too coarse to take into account the effect of local topography.

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Section: Introductionmentioning

confidence: 78%

Section: Forecast Evaluationmentioning

confidence: 99%

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Valley Winds at the Local Scale: Correcting Routine Weather Forecast Using Artificial Neural Networks

et al. 2021

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“…down‐valley and opposite to the daytime direction. This weak drainage flow will, hereafter, be referred to as the Cadarache down‐valley (CDV) wind, and is primarily thermally driven (Duine et al , 2016). Whenever strong Mistral events occurred (e.g.…”

Section: Resultsmentioning

confidence: 99%

“…This mechanism is anyway mostly found in valleys with moderate and cloudy climates, whilst the Cadarache region mainly experiences clear skies. From Figure (e), forced chanelling cannot be fully excluded as a mechanism, but the CV flows are primarily thermally driven (Duine et al , 2016).…”

Section: Resultsmentioning

confidence: 99%

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Duine

Hedde

Roubin

et al. 2017

Quart J Royal Meteoro Soc

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Wind patterns in main and tributary valley systems undergo diurnal variations that are very dependent on the valley's dimensions. Characterizing the down‐valley winds is important for pollutant dispersion studies. It is also a challenge for numerical simulations. This paper uses KASCADE (KAtabatic winds and Stability over CAdarache for Dispersion of Effluents) observations to describe down‐valley flow development and characteristics in two intersecting, shallow valleys of different sizes located in the pre‐alpine region of southeast France. The Durance Valley and its tributary valley, the Cadarache Valley, are different in depth (200 and 100 m depth, respectively), slope (0.2 and 1.2°), width (5–8 and 1–2 km) and length (>50 and 6 km). Both down‐valley flows were dominant features for the period of measurements. The distinct valley scales lead to different characteristics: the smaller Cadarache down‐valley wind is primarily thermally driven and attains wind speeds of up to 1–4 m s−1 with its jet nose at around 30 m in height above ground. The flow at that height initiates 2 h after sensible heat flux turnover, a time‐scale which relates to a linear wave solution for along‐valley winds. The Durance down‐valley wind involves larger scales –for both terrain features and large‐scale circulation –and is related to a mountain‐to‐plain circulation. Therefore its onset occurs with a delay of ∼6 h after sunset. It reaches speeds of 4–8 m s−1 and a depth of 175–225 m above ground. Its highest occurrence is just after sunrise. Between the two valley winds, a shear layer is observed, the origin of which could be a combination of a Cadarache valley flow return current and a Durance down‐valley wind stream redirected by orography.

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Spatial variability in winter mass balance on Storglaciären modelled with a terrain-based approach

2022

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Although most processes governing the surface mass balance on mountain glaciers are well understood, the causes and extent of spatial variability in accumulation remain poorly constrained. In the present study, we couple an energy balance–snow and firn mass-balance model to terrain-based modelling routines estimating mass redistribution by snowdrift, preferential deposition and avalanching. We find this newly coupled model improves the spatial accuracy of winter balance simulations on Storglaciären, Sweden, while retaining versatility and a low computational cost. Accumulation on Storglaciären is primarily driven by direct precipitation, which is locally increased due to small-scale orographic effects. Wind-driven snow transport leads to substantial deposition in the accumulation zone and slight erosion in the ablation zone. Avalanching is the smallest contributor to winter balance, but cannot be neglected. The role of mass transporting processes in maintaining the current mass equilibrium on Storglaciären highlights the necessity to understand the links between climatic predictors and accumulation in order to accurately assess climate sensitivity.

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A Simple Method Based on Routine Observations to Nowcast Down-Valley Flows in Shallow, Narrow Valleys

Cited by 10 publications

References 29 publications

Valley Winds at the Local Scale: Correcting Routine Weather Forecast Using Artificial Neural Networks

Valley Winds at the Local Scale: Correcting Routine Weather Forecast Using Artificial Neural Networks

Characterization of valley flows within two confluent valleys under stable conditions: observations from the KASCADE field experiment

Spatial variability in winter mass balance on Storglaciären modelled with a terrain-based approach

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