Next Article in Journal
The Uncharacteristic Occurrence of the June 2013 Biomass-Burning Haze Event in Southeast Asia: Effects of the Madden-Julian Oscillation and Tropical Cyclone Activity
Previous Article in Journal
An Integrated Wind Risk Warning Model for Urban Rail Transport in Shanghai, China
Open AccessArticle

Diurnal Valley Winds in a Deep Alpine Valley: Observations

1
Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt, Germany
2
Federal Office of Meteorology and Climatology, MeteoSwiss, 1530 Payerne, Switzerland
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Atmosphere 2020, 11(1), 54; https://doi.org/10.3390/atmos11010054
Received: 8 December 2019 / Revised: 23 December 2019 / Accepted: 27 December 2019 / Published: 1 January 2020
(This article belongs to the Section Meteorology)
Diurnal valley winds frequently form over complex topography, particularly under fair weather conditions, and have a significant impact on the local weather and climate. Since diurnal valley winds result from complex and multi-scale interactions, their representation in numerical weather prediction models is challenging. Better understanding of these local winds based on observations is crucial to improve the accuracy of the forecasts. This study investigates the diurnal evolution of the three-dimensional mean wind structure in a deep Alpine valley, the Rhone valley at Sion, using data from a radar wind profiler and a surface weather station operated continuously from 1 September 2016 to 17 July 2017. In particular, the wind profiler data was analyzed for a subset of days on which fair weather conditions allowed for the full development of thermally driven winds. A pronounced diurnal cycle of the wind speed, as well as a reversal of the wind direction twice per day is documented for altitudes up to about 2 km above ground level (AGL) in the warm season and less than 1 km AGL in winter. The diurnal pattern undergoes significant changes during the course of the year. Particularly during the warm-weather months of May through to September, a low-level wind maximum occurs, where mean maximum up-valley velocities of 8–10 m s−1 are found between 15–16 UTC at altitudes around 200 m AGL. In addition, during nighttime, a down-valley jet with maximum wind speeds of 4–8 m s−1 around 1 km AGL is found. A case study of a three-day period in September 2016 illustrates the occurrence of an elevated layer of cross-valley flow around 1–1.5 km AGL. View Full-Text
Keywords: valley wind; diurnal cycle; radar wind profiler; alpine valley; cross-valley flow valley wind; diurnal cycle; radar wind profiler; alpine valley; cross-valley flow
Show Figures

Figure 1

MDPI and ACS Style

Schmid, F.; Schmidli, J.; Hervo, M.; Haefele, A. Diurnal Valley Winds in a Deep Alpine Valley: Observations. Atmosphere 2020, 11, 54.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop