Offshore winds obtained from a network of wind‐profiler radars during HyMeX

Saïd, F.; Campistron, Bernard; Delbarre, Hervé; Canut, Guylaine; Doerenbecher, Alexis; Durand, Pierre; Fourrié, Nadia; Lambert, Dominique; Legain, D.

doi:10.1002/qj.2749

Cited by 15 publications

(29 citation statements)

References 56 publications

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“…Among them, several wind profilers were deployed along the northwestern Mediterranean coast, including a UHF profiler in Ile du Levant (see Figure for location). It provides valuable information on the vertical wind profile in the lower half of the troposphere just upstream of the Var region at 55 levels every 4 min (Saïd et al , ). The Water Vapour and Aerosol Lidar (WALI: Chazette et al , ) was operated in Ciutadella (Menorca, Balearic Islands; see Figure for location) and the water vapour and temperature Raman lidar system (BASIL: Di Girolamo et al , ) in Candillargues (see Figure for location).…”

Section: Iop13 Overviewmentioning

confidence: 99%

Role of moisture patterns in the backbuilding formation of HyMeX IOP13 heavy precipitation systems

Duffourg

Lee

Ducrocq

et al. 2018

Quart J Royal Meteoro Soc

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International audienceMediterranean regions are regularly affected by heavy convective precipitation. During the Hydrological Cycle in the Mediterranean Experiment Intensive Observation Period 13 (HyMeX-IOP13), the multi-platform observation strategy allowed analysing the backbuilding convective systems which developed on 14 October 2012 as well as the associated moisture structures in the environment upstream of convection.The numerical simulation at 2.5-km horizontal resolution succeeds in reproducing the location and time evolution of the observed heavy precipitation systems and the main characteristics of the marine air mass. Convection develops in Southeastern France over the foothills closest to the coast when a moist conditionally unstable marine boundary layer topped by particularly dry air masses is advected inland. Cold air formed by evaporative cooling under the precipitating cells flows down the valleys slowly shifting the location of the backbuilding convective cells from the mountainsides to the coast and over the sea. Surface observations confirm that these simulated backbuilding mechanisms describe realistically the processes involved in the maintenance of the heavy precipitation event.A lagrangian analysis shows that the moisture supply to the convective system is provided by the moist conditionally unstable marine boundary layer while the dry air masses above are involved in the cold pool formation. Four days before the event, both, the dry and the moist air masses, come from the Atlantic Ocean in the lower half of the troposphere. The dry air mass involved in the cold pool formation results from both the advection of mid-level air masses and the drying of low-level air masses lifted up over Spain. For the moist air mass feeding the backbuilding convective systems, most of the air parcels overpass France before travelling almost 48 hours in the lowest 1000m above the Mediterranean. About 50 % of the moisture supply to the precipitating system originates from the evaporation over the sea

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Section: Iop13 Overviewmentioning

confidence: 99%

Role of moisture patterns in the backbuilding formation of HyMeX IOP13 heavy precipitation systems

Duffourg

Lee

Ducrocq

et al. 2018

Quart J Royal Meteoro Soc

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“…The progressive change of moist to dry air is accompanied by a subsidence of the boundary layer. At 1800 UTC 12 October 2012 strong winds (in excess of 15 m s −1 ) extend up to 4 km, possibly as a result of the merging of Tramontane and Mistral in the proximity of Candillargues (see also Saïd et al (2016)). These results are also confirmed by the observations performed by another UHF wind profiler located in the Rhône valley, east of Candillargues, showing a strong northerly flow starting at 1800 UTC 12 October 2012 (not shown).…”

Section: Case-study On 10-12 October 2012mentioning

confidence: 99%

“…Mistral and Tramontane bring cold and dry continental air over the sea and are frequently observed to extend a few hundred kilometres off the coast (Jansa, 1987;Georgelin and Richard, 1996;Drobinski et al, 2001Drobinski et al, , 2005Guénard et al, 2005Guénard et al, , 2006, and, especially in the winter, generate intense air-sea heat exchanges (Flamant, 2003;Rainaud et al, 2015;Saïd et al, 2016) and sea surface cooling (Schott et al, 1996), which strongly impacts the coastal ocean dynamics (Estournel et al, 2003;Lebeaupin-Brossier et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Observation of low‐level wind reversals in the Gulf of Lion area and their impact on the water vapour variability

Girolamo

Flamant

Cacciani

et al. 2016

Quart J Royal Meteoro Soc

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International audienceWater vapour measurements from a ground-based Raman lidar and an airborne differential absorption lidar, complemented by high resolution numerical simulations from two mesoscale models (AROME-WMED and Meso-NH), are considered to investigate three transition events from Mistral/Tramontane to southerly marine flow taking place in the Montpellier region (Southern France) in the time frame September-October 2012, during the Hydrological Cycle in the Mediterranean Experiment Special Observation Period 1. Low-level wind reversals associated with these transitions are found to have a strong impact on water vapour transport, leading to a large variability of the water vapour vertical and horizontal distributions. Water vapour mixing ratio within the boundary layer is found to vary from typical values in the range 4–8 g kg−1 during the northerly Mistral/Tramontane flows to values in the range 8–15 g kg−1 during the southerly marine flows. The increase/decrease in water vapour mixing ratio within the boundary layer may be abrupt and marked during these transition periods, with values increasing-decreasing by a factor of 2 to 4 within 1 hour. The high spatial and temporal resolutions of the lidar data allow monitoring the time evolution of the water vapour field during these transitions from predominantly northerly Mistral/Tramontane flow to a predominantly southerly flow, permitting to identify the quite sharp separation between these flows, which is also satisfactorily well captured by the mesoscale models. Water vapour measurements from the ground-based lidar are complemented by particle backscatter measurements from the same system, which allow also revealing the significant variability in the aerosol and cloud fields associated with these transition events

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“…Both profilers are five-beam model PCL 1300 manufactured by Degreane. A detailed description of the WPRs, their main working parameters and the processing methods are provided in Saïd et al (2016). Both radars were operated almost continuously at both sites over long periods (exceeding 18 months).…”

Section: Instrumentsmentioning

confidence: 99%

“…The purpose of the consensus data processing is to determine the meteorological spectral peak among the four more powerful peaks of the Doppler spectra at each range gate. The method is fully described in Saïd et al (2016). Special care was devoted to the separation between the meteorological peak and ground clutter echoes or the separation of individual echoes from a multiple-echo peak.…”

Section: Radar Data Processingmentioning

confidence: 99%

High-resolution humidity profiles retrieved from wind profiler radar measurements

Saïd

Campistron²,

Girolamo

2018

Atmos. Meas. Tech.

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Abstract. The retrieval of humidity profiles from wind profiler radars has already been documented in the past 30 years and is known to be neither as straightforward and nor as robust as the retrieval of the wind velocity. The main constraint to retrieve the humidity profile is the necessity to combine measurements from the wind profiler and additional measurements (such as observations from radiosoundings at a coarser time resolution). Furthermore, the method relies on some assumptions and simplifications that restrict the scope of its application. The first objective of this paper is to identify the obstacles and limitations and solve them, or at least define the field of applicability. To improve the method, we propose using the radar capacity to detect transition levels, such as the top level of the boundary layer, marked by a maximum in the radar reflectivity. This forces the humidity profile from the free troposphere and from the boundary layer to coincide at this level, after an optimization of the calibration coefficients, and reduces the error. The resulting mean bias affecting the specific humidity profile never exceeds 0.25 g kg −1 . The second objective is to explore the capability of the algorithm to retrieve the humidity vertical profiles for an operational purpose by comparing the results with observations from a Raman lidar.

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Offshore winds obtained from a network of wind‐profiler radars during HyMeX

Cited by 15 publications

References 56 publications

Role of moisture patterns in the backbuilding formation of HyMeX IOP13 heavy precipitation systems

Role of moisture patterns in the backbuilding formation of HyMeX IOP13 heavy precipitation systems

Observation of low‐level wind reversals in the Gulf of Lion area and their impact on the water vapour variability

High-resolution humidity profiles retrieved from wind profiler radar measurements

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