scholarly journals Observations of an elevated rotor and precipitation processes decoupled during a mountain wave event in the Eastern Pyrenees (Cerdanya-2017 Field Experiment) 

2021 ◽  
Author(s):  
Mireia Udina ◽  
Joan Bech ◽  
Sergi Gonzalez ◽  
Alexandre Paci ◽  
Laura Trapero ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Doppler Radar ◽  
Horizontal Distance ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Eastern Pyrenees ◽  
Precipitation Processes ◽  
Wave Event ◽  
Wave Induced ◽  
K Band

<p>The study documents the formation of a rotor underneath the mountain waves generated the 15 January 2017 over the eastern Pyrenees (near the border between France, Spain and Andorra) during the Cerdanya-2017 field campaign. The event was characterized by strong winds, mountain waves and relevant snow accumulation over the Cerdanya valley and the eastern Pyrenees. The evolution and location of the mountain waves and precipitation structure were studied using high temporal resolution data from a UHF wind-profiler and a vertically pointing K-band Doppler radar, separated a few kilometres in horizontal distance.</p><p>A mountain wave was detected in the morning and shortened slightly in the afternoon when a transient rotor was formed disconnected from the surface flow (Udina et al. 2020). A strong turbulence zone was identified at the upper edge of the mountain wave, above the rotor, a feature observed in previous studies. The mountain wave and rotor induced circulation was favoured by the valley shape and the second mountain ridge location, in addition to the weak and variable winds, established during the sunset close to the valley surface. In addition, we find decoupling between precipitation processes and mountain wave induced circulations. During the studied event, mountain wave wind circulations and low-level turbulence do not affect neither the snow crystal riming or aggregation along the vertical column nor the surface particle size distribution of the snow. This study illustrates that precipitation profiles and mountain induced circulations may be decoupled which can be very relevant for either ground-based or spaceborne remote sensing of precipitation (Gonzalez et al 2019). This research is supported by CGL2015-65627-C3-1-R, CGL2015- 65627-C3-2-R (MINECO/FEDER), CGL2016-81828-REDT and RTI2018- 098693-B-C32 (AEI/FEDER).</p><p>References:</p><p>Gonzalez, S., Bech, J., Udina, M., Codina, B., Paci, A., & Trapero, L. (2019). Decoupling between precipitation processes and mountain wave induced circulations observed with a vertically pointing K-band doppler radar. <em>Remote Sensing</em>, <em>11</em>(9), 1034.</p><p>Udina, M., Bech, J., Gonzalez, S., Soler, M. R., Paci, A., Miró, J. R., Trapero, L., Donier, J.M., Douffet, T., Codina, B., Pineda, N. (2020). Multi-sensor observations of an elevated rotor during a mountain wave event in the Eastern Pyrenees. <em>Atmospheric Research</em>, <em>234</em>, 104698.</p>

scholarly journals Decoupling between Precipitation Processes and Mountain Wave Induced Circulations Observed with a Vertically Pointing K-Band Doppler Radar

2019 ◽  
Vol 11 (9) ◽  
pp. 1034 ◽  
Author(s):  
Sergi Gonzalez ◽  
Joan Bech ◽  
Mireia Udina ◽  
Bernat Codina ◽  
Alexandre Paci ◽  
...  
Keyword(s):  
Doppler Radar ◽  
Microwave Radiometer ◽  
Mountain Range ◽  
Mountain Wave ◽  
Vertical Column ◽  
Mountain Waves ◽  
Low Level ◽  
Eastern Pyrenees ◽  
Microphysical Processes ◽  
Wave Induced

Recent studies reported that precipitation and mountain waves induced low tropospheric level circulations may be decoupled or masked by greater spatial scale variability despite generally there is a connection between microphysical processes of precipitation and mountain driven air flows. In this paper we analyse two periods of a winter storm in the Eastern Pyrenees mountain range (NE Spain) with different mountain wave induced circulations and low-level turbulence as revealed by Micro Rain Radar (MRR), microwave radiometer and Parsivel disdrometer data during the Cerdanya-2017 field campaign. We find that during the event studied mountain wave wind circulations and low-level turbulence do not affect neither the snow crystal riming or aggregation along the vertical column nor the surface particle size distribution of the snow. This study illustrates that precipitation profiles and mountain induced circulations may be decoupled which can be very relevant for either ground-based or spaceborne remote sensing of precipitation.

scholarly journals Mountain waves modulate the water vapor distribution in the UTLS

2017 ◽  
Author(s):  
Romy Heller ◽  
Christiane Voigt ◽  
Stuart Beaton ◽  
Andreas Dörnbrack ◽  
Stefan Kaufmann ◽  
...  
Keyword(s):  
Water Vapor ◽  
New Zealand ◽  
Vertical Transport ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Wave Event ◽  
Transport And Mixing ◽  
Vapor Distribution

Abstract. The water vapor distribution in the upper troposphere/lower stratosphere region (UTLS) has a strong impact on the atmospheric radiation budget. Transport and mixing processes on different scales mainly determine the water vapor concentration in the UTLS. Here, we investigate the effect of mountain waves on the vertical transport and mixing of water vapor. For this purpose we analyse measurements of water vapor and meteorological parameters recorded by the DLR Falcon and NSF/NCAR GV research aircraft taken during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) in New Zealand. By combining different methods, we develop a new approach to quantify location, direction and irreversibility of the water vapor transport during a strong mountain wave event on 4 July 2014. A large positive vertical water vapor flux is detected above the Southern Alps extending from the troposphere to the stratosphere in the altitude range between 7.7 and 13.0 km. Wavelet analysis for the 8.9 km altitude level shows that the enhanced upward water vapor transport above the mountains is caused by mountain waves with horizontal wavelengths between 22 and 60 km. A downward transport of water vapor with 22 km wavelength is observed in the lee-side of the mountain ridge. While it is a priori not clear whether the observed fluxes are irreversible, low Richardson numbers derived from dropsonde data indicate enhanced turbulence in the tropopause region related to the mountain wave event. Together with the analysis of the water vapor to ozone correlation we find indications for vertical transport followed by irreversible mixing of water vapor. For our case study, we further estimate greater than 1 W m−2 radiative forcing by the increased water vapor concentrations in the UTLS above the Southern Alps of New Zealand resulting from mountain waves relative to unperturbed conditions. Hence, mountain waves have a great potential to affect the water vapor distribution in the UTLS. Our regional study may motivate further investigations of the global effects of mountain waves on the UTLS water vapor distributions and its radiative effects.

scholarly journals Influence of mountain waves and NAT nucleation mechanisms on polar stratospheric cloud formation at local and synoptic scales during the 1999-2000 Arctic winter

2005 ◽  
Vol 5 (3) ◽  
pp. 739-753 ◽  
Author(s):  
S. H. Svendsen ◽  
N. Larsen ◽  
B. Knudsen ◽  
S. D. Eckermann ◽  
E. V. Browell
Keyword(s):  
Winter Season ◽  
Temperature Fluctuations ◽  
Mountain Wave ◽  
Data Set ◽  
Mountain Waves ◽  
Ice Particles ◽  
Wave Forecast ◽  
Synoptic Conditions ◽  
Nucleation Mechanisms ◽  
Wave Induced

Abstract. A scheme for introducing mountain wave-induced temperature pertubations in a microphysical PSC model has been developed. A data set of temperature fluctuations attributable to mountain waves as computed by the Mountain Wave Forecast Model (MWFM-2) has been used for the study. The PSC model has variable microphysics, enabling different nucleation mechanisms for nitric acid trihydrate, NAT, to be employed. In particular, the difference between the formation of NAT and ice particles in a scenario where NAT formation is not dependent on preexisting ice particles, allowing NAT to form at temperatures above the ice frost point, Tice, and a scenario, where NAT nucleation is dependent on preexisting ice particles, is examined. The performance of the microphysical model in the different microphysical scenarios and a number of temperature scenarios with and without the influence of mountain waves is tested through comparisons with lidar measurements of PSCs made from the NASA DC-8 on 23 and 25 January during the SOLVE/THESEO 2000 campaign in the 1999-2000 winter and the effect of mountain waves on local PSC production is evaluated in the different microphysical scenarios. Mountain waves are seen to have a pronounced effect on the amount of ice particles formed in the simulations. Quantitative comparisons of the amount of solids seen in the observations and the amount of solids produced in the simulations show the best correspondence when NAT formation is allowed to take place at temperatures above Tice. Mountain wave-induced temperature fluctuations are introduced in vortex-covering model runs, extending the full 1999-2000 winter season, and the effect of mountain waves on large-scale PSC production is estimated in the different microphysical scenarios. It is seen that regardless of the choice of microphysics ice particles only form as a consequence of mountain waves whereas NAT particles form readily as a consequence of the synoptic conditions alone if NAT nucleation above Tice is included in the simulations. Regardless of the choice of microphysics, the inclusion of mountain waves increases the amount of NAT particles by as much as 10%. For a given temperature scenario the choice of NAT nucleation mechanism may alter the amount of NAT substantially; three-fold increases are easily found when switching from the scenario which requires pre-existing ice particles in order for NAT to form to the scenario where NAT forms independently of ice.

scholarly journals Inclusion of mountain wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry–climate model

2014 ◽  
Vol 14 (12) ◽  
pp. 18277-18314 ◽  
Author(s):  
A. Orr ◽  
J. S. Hosking ◽  
L. Hoffmann ◽  
J. Keeble ◽  
S. M. Dean ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Temperature Fluctuations ◽  
Horizontal Resolution ◽  
Measured Temperature ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Wave Induced ◽  
The Antarctic

Abstract. An important source of polar stratospheric clouds (PSCs), which play a crucial role in controlling polar stratospheric ozone depletion, is from the temperature fluctuations induced by mountain waves. However, this formation mechanism is usually missing in chemistry–climate models because these temperature fluctuations are neither resolved nor parameterised. Here, we investigate the representation of stratospheric mountain wave-induced temperature fluctuations by the UK Met Office Unified Model (UM) at high and low spatial resolution against Atmospheric Infrared Sounder satellite observations for three case studies over the Antarctic Peninsula. At a high horizontal resolution (4 km) the mesoscale configuration of the UM correctly simulates the magnitude, timing, and location of the measured temperature fluctuations. By comparison, at a low horizontal resolution (2.5° × 3.75°) the climate configuration fails to resolve such disturbances. However, it is demonstrated that the temperature fluctuations computed by a mountain wave parameterisation scheme inserted into the climate configuration (which computes the temperature fluctuations due to unresolved mountain waves) are in excellent agreement with the mesoscale configuration responses. The parameterisation was subsequently used to compute the local mountain wave-induced cooling phases in the chemistry–climate configuration of the UM. This increased stratospheric cooling was passed to the PSC scheme of the chemistry–climate model, and caused a 30–50% increase in PSC surface area density over the Antarctic Peninsula compared to a 30 year control simulation.

scholarly journals Mountain-wave-induced polar stratospheric clouds and their representation in the global chemistry model ICON-ART

2021 ◽  
Vol 21 (12) ◽  
pp. 9515-9543
Author(s):  
Michael Weimer ◽  
Jennifer Buchmüller ◽  
Lars Hoffmann ◽  
Ole Kirner ◽  
Beiping Luo ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Scale Effects ◽  
Hot Spot ◽  
Orthogonal Polarization ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Stratospheric Clouds ◽  
Wave Induced ◽  
The Antarctic

Abstract. Polar stratospheric clouds (PSCs) are a driver for ozone depletion in the lower polar stratosphere. They provide surface for heterogeneous reactions activating chlorine and bromine reservoir species during the polar night. The large-scale effects of PSCs are represented by means of parameterisations in current global chemistry–climate models, but one process is still a challenge: the representation of PSCs formed locally in conjunction with unresolved mountain waves. In this study, we investigate direct simulations of PSCs formed by mountain waves with the ICOsahedral Nonhydrostatic modelling framework (ICON) with its extension for Aerosols and Reactive Trace gases (ART) including local grid refinements (nesting) with two-way interaction. Here, the nesting is set up around the Antarctic Peninsula, which is a well-known hot spot for the generation of mountain waves in the Southern Hemisphere. We compare our model results with satellite measurements of PSCs from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and gravity wave observations of the Atmospheric Infrared Sounder (AIRS). For a mountain wave event from 19 to 29 July 2008 we find similar structures of PSCs as well as a fairly realistic development of the mountain wave between the satellite data and the ICON-ART simulations in the Antarctic Peninsula nest. We compare a global simulation without nesting with the nested configuration to show the benefits of adding the nesting. Although the mountain waves cannot be resolved explicitly at the global resolution used (about 160 km), their effect from the nested regions (about 80 and 40 km) on the global domain is represented. Thus, we show in this study that the ICON-ART model has the potential to bridge the gap between directly resolved mountain-wave-induced PSCs and their representation and effect on chemistry at coarse global resolutions.

scholarly journals Influence of mountain waves and NAT nucleation mechanisms on Polar Stratospheric Cloud formation at local and synoptic scales during the 1999–2000 Arctic winter

2004 ◽  
Vol 4 (4) ◽  
pp. 4581-4609 ◽  
Author(s):  
S. H. Svendsen ◽  
N. Larsen ◽  
B. Knudsen ◽  
S. D. Eckermann ◽  
E. V. Browell
Keyword(s):  
Large Scale ◽  
Winter Season ◽  
Temperature Fluctuations ◽  
Mountain Wave ◽  
Data Set ◽  
Mountain Waves ◽  
Ice Particles ◽  
Wave Forecast ◽  
Nucleation Mechanisms ◽  
Wave Induced

Abstract. A scheme for introducing mountain wave-induced temperature pertubations in a microphysical PSC model has been developed. A data set of temperature fluctuations attributable to mountain waves as computed by the Mountain Wave Forecast Model (MWFM-2) has been used for the study. The PSC model has variable microphysics, enabling different nucleation mechanisms for nitric acid trihydrate, NAT, to be employed. In particular, the difference between the formation of NAT and ice particles in a scenario where NAT formation is not dependent on preexisting ice particles, allowing NAT to form at temperatures above the ice frost point, Tice, and a scenario, where NAT nucleation is dependent on preexisting ice particles, is examined. The performance of the microphysical model in the different microphysical scenarios and a number of temperature scenarios with and without the influence of mountain waves is tested through comparisons with lidar measurements of PSCs made from the NASA DC-8 on 23 and 25 January during the SOLVE/THESEO 2000 campaign in the 1999–2000 winter and the effect of mountain waves on local PSC production is evaluated in the different microphysical scenarios. Mountain wave-induced temperature fluctuations are introduced in vortex-covering model runs, extending the full 1999–2000 winter season, and the effect of mountain waves on large-scale PSC production is estimated in the different microphysical scenarios.

Multi-sensor observations of an elevated rotor during a mountain wave event in the Eastern Pyrenees

2020 ◽  
Vol 234 ◽  
pp. 104698 ◽  
Author(s):  
Mireia Udina ◽  
Joan Bech ◽  
Sergi Gonzalez ◽  
Maria Rosa Soler ◽  
Alexandre Paci ◽  
...  
Keyword(s):  
Mountain Wave ◽  
Eastern Pyrenees ◽  
Wave Event

scholarly journals Mountain waves modulate the water vapor distribution in the UTLS

2017 ◽  
Vol 17 (24) ◽  
pp. 14853-14869 ◽  
Author(s):  
Romy Heller ◽  
Christiane Voigt ◽  
Stuart Beaton ◽  
Andreas Dörnbrack ◽  
Andreas Giez ◽  
...  
Keyword(s):  
Water Vapor ◽  
New Zealand ◽  
Vertical Transport ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Wave Event ◽  
Transport And Mixing ◽  
Vapor Distribution

Abstract. The water vapor distribution in the upper troposphere–lower stratosphere (UTLS) region has a strong impact on the atmospheric radiation budget. Transport and mixing processes on different scales mainly determine the water vapor concentration in the UTLS. Here, we investigate the effect of mountain waves on the vertical transport and mixing of water vapor. For this purpose we analyze measurements of water vapor and meteorological parameters recorded by the DLR Falcon and NSF/NCAR Gulfstream V research aircraft taken during the Deep Propagating Gravity Wave Experiment (DEEPWAVE) in New Zealand. By combining different methods, we develop a new approach to quantify location, direction and irreversibility of the water vapor transport during a strong mountain wave event on 4 July 2014. A large positive vertical water vapor flux is detected above the Southern Alps extending from the troposphere to the stratosphere in the altitude range between 7.7 and 13.0 km. Wavelet analysis for the 8.9 km altitude level shows that the enhanced upward water vapor transport above the mountains is caused by mountain waves with horizontal wavelengths between 22 and 60 km. A downward transport of water vapor with 22 km wavelength is observed in the lee-side of the mountain ridge. While it is a priori not clear whether the observed fluxes are irreversible, low Richardson numbers derived from dropsonde data indicate enhanced turbulence in the tropopause region related to the mountain wave event. Together with the analysis of the water vapor to ozone correlation, we find indications for vertical transport followed by irreversible mixing of water vapor. For our case study, we further estimate greater than 1 W m−2 radiative forcing by the increased water vapor concentrations in the UTLS above the Southern Alps of New Zealand, resulting from mountain waves relative to unperturbed conditions. Hence, mountain waves have a great potential to affect the water vapor distribution in the UTLS. Our regional study may motivate further investigations of the global effects of mountain waves on the UTLS water vapor distributions and its radiative effects.

scholarly journals Mountain-wave induced polar stratospheric clouds and their representation in the global chemistry model ICON-ART

2020 ◽  
Author(s):  
Michael Weimer ◽  
Jennifer Buchmüller ◽  
Lars Hoffmann ◽  
Ole Kirner ◽  
Beiping Luo ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Climate Models ◽  
Hot Spot ◽  
Heterogeneous Reactions ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Stratospheric Clouds ◽  
Wave Induced ◽  
The Antarctic

Abstract. Polar stratospheric clouds (PSCs) are a driver for ozone depletion in the lower polar stratosphere. They provide surfaces for heterogeneous reactions activating chlorine and bromine reservoir species during the polar night. PSCs are represented in current global chemistry-climate models, but one process is still a challenge: the representation of PSCs formed locally in conjunction with unresolved mountain waves. In this study, we present simulations with the ICOsahedral Nonhydrostatic modelling framework (ICON) with its extension for Aerosols and Reactive Trace gases (ART) that include local grid refinements (nesting) with two-way interaction. Here, the nesting is set up around the Antarctic Peninsula which is a well-known hot spot for the generation of mountain waves in the southern hemisphere. We compare our model results with satellite measurements from the Cloud-Aerosol LIdar with Orthogonal Polarisation (CALIOP) and the Atmospheric InfraRed Sounder (AIRS). We study a mountain wave event that took place from 19 to 29 July 2008 and find similar structures of PSCs as well as a fairly realistic development of the mountain wave in the Antarctic Peninsula nest. We compare a global simulation without nesting with the nested configuration to show the benefit. Although the mountain waves cannot be resolved adequately in the used global resolution (about 160 km), their effect from the nested regions (about 80 and 40 km) on the global domain is represented. Thus, we show in this study that by using the two-way nesting technique the gap between directly resolved mountain-wave induced PSCs and their representation and effect on chemistry in coarse global resolutions can be bridged by the ICON-ART model.

scholarly journals On High Winds and Foehn Warming Associated with Mountain-Wave Events in the Western Foothills of the Southern Appalachian Mountains

2009 ◽  
Vol 24 (1) ◽  
pp. 53-75 ◽  
Author(s):  
David M. Gaffin
Keyword(s):  
Source Region ◽  
Appalachian Mountains ◽  
Return Flow ◽  
Mountain Wave ◽  
Mountain Waves ◽  
Southern Appalachian Mountains ◽  
Low Level ◽  
Southern Appalachian ◽  
Wave Induced ◽  
High Winds

Abstract Extremely high winds of 40–49 m s−1 [90–110 miles per hour (mph)] were reported across the western foothills of the southern Appalachian Mountains on 22–23 December 2004, 17 October 2006, 24–25 February 2007, and 1 March 2007. The high winds in all four of these events were determined to be the result of mountain waves, as strong southeast winds became perpendicular to the mountains with a stable boundary layer present below 750 hPa and a veering wind profile that increased with height. Adiabatic warming of the descending southeasterly winds was also observed at the Knoxville airport during all four events (although of varying intensities), with the 850-hPa air mass immediately upwind of the Smoky Mountains determined to be the source region of these foehn winds. An interesting similarity among these four events was the location of the strongest 850-hPa winds northwest of the region, with a rapidly decreasing speed gradient observed over the mountains. These 850-hPa winds northwest of the mountains were also stronger than the 700-hPa winds in the region. It was hypothesized that strong low-level divergence developed in the foothills, as the stronger 850-hPa winds on the western side accelerated away from the mountains while the mountains prevented a rapid return flow from the eastern side. This low-level divergence likely helped to further strengthen the mountain-wave-induced mesolow and high winds in the western foothills. A 12-yr climatology of high wind events induced by mountain waves at Cove Mountain was also constructed. This climatology revealed that these events occurred primarily at night between November and March. Composite maps of mountain-wave events that produced warning-level and advisory-level winds revealed that an axis of stronger 850-hPa winds was typically located west of the mountains (away from the foothills). This finding (using reanalysis data instead of model data) further suggested that low-level divergence normally contributed to the intensity of mountain-wave-induced mesolows and winds in the western foothills of the southern Appalachian Mountains.

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