Frequency of Mountain Waves Over Kanto Area Revealed by Imaging Observations of OH Airglow

2021 ◽  
Author(s):  
Satoshi Ishii ◽  
Yoshihiro Tomikawa ◽  
Masahiro Okuda ◽  
Hidehiko Suzuki
Keyword(s):  
Spatial Scales ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Leeward Side ◽  
Mountainous Areas ◽  
Wind Fields ◽  
Mountain Waves ◽  
The World ◽  
Geostationary Meteorological Satellite ◽  
Good Proxy

Abstract Imaging observations of OH airglow were conducted at Meiji University, Japan (IN, mE), from May 2018 to December 2019. Mountainous areas, including Mt. Fuji, are located to the west of the imager, and westerly winds are dominant in the lower atmosphere throughout the year. Mountain waves (MWs) are generated on the leeward sides of mountains and occasionally propagate to the upper atmosphere. However, during the observation period (about 1 year and 8 months), only four possible MW events were identified. Based on previous reports, this incidence is considerably lower than expected. There are two possible reasons for the low incidence of MW events: (1) The frequency of MW excitation is small in the lower layers of the atmosphere, and/or (2) MWs do not propagate easily to the upper mesosphere due to background wind conditions. This study verified the likelihood of the former case. Under over-mountain airflow conditions, wavy clouds are often generated on the leeward side. Since over-mountain airflow is essential for the excitation of MWs, the frequency of wavy clouds in the lower atmosphere can be regarded as a measure of the occurrence of MWs. The frequency and spatial distribution of MWs around Japan were investigated by detecting the wavy clouds from color images taken by the Himawari-8 geostationary meteorological satellite (GSM-8) for one year in 2018. The wavy clouds were detected on more than 70 days a year around the Tohoku region, but just 20 days a year around Mt. Fuji. This suggests that few MWs are generated around Mt. Fuji. The differences between these two regions were examined focusing on the relationship between the local topography and dominant horizontal wind fields in the lower atmosphere. Specifically, the findings showed that the angle between the dominant horizontal wind direction and the orientation of the mountain ridge is a good proxy of the occurrence of wavy clouds, i.e., excitation of MWs in mountainous areas. We have also applied this proxy to topography in other areas of the world to investigate areas where MWs would be occurring frequently. Finally, we discuss the likelihood of "MW hotspots" at various spatial scales in the world.

scholarly journals Relationship between topography, tropospheric wind, and frequency of mountain waves in the upper mesosphere over the Kanto area of Japan

2022 ◽  
Vol 74 (1) ◽  
Author(s):  
Satoshi Ishii ◽  
Yoshihiro Tomikawa ◽  
Masahiro Okuda ◽  
Hidehiko Suzuki
Keyword(s):  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Observation Site ◽  
Mountain Waves ◽  
Westerly Winds ◽  
Geostationary Meteorological Satellite ◽  
Good Proxy ◽  
Low Incidence ◽  
Wind Profiles ◽  
Meteorological Satellite

AbstractImaging observations of OH airglow were performed at Meiji University, Japan (35.6° N, 139.5° E), from May 2018 to December 2019. Mountainous areas are located to the west of the imager, and westerly winds are dominant in the lower atmosphere throughout the year. Mountain waves (MWs) are generated and occasionally propagate to the upper atmosphere. However, only four likely MW events were identified, which are considerably fewer than expected. There are two possible reasons for the low incidence: (1) MWs do not propagate easily to the upper mesosphere due to background wind conditions, and/or (2) the frequency of MW excitation was low around the observation site. Former possibility is found not to be a main reason to explain the frequency by assuming typical wind profiles in troposphere and upper mesosphere over Japan. Thus, frequency and spatial distribution of orographic wavy clouds were investigated by analyzing images taken by the Himawari-8 geostationary meteorological satellite in 2018. The number of days when wavy clouds were detected in the troposphere around the observation site (Kanto area) was about a quarter of that around the Tohoku area. This result indicates that frequency of over-mountain flow which is thought to be a source of excitation of MWs is low in Kanto area. We also found that the angle between the horizontal wind direction in troposphere and the orientation of the mountain ridge is a good proxy for the occurrence of orographic wavy clouds, i.e., excitation of MWs. We applied this proxy to the topography around the world to investigate regions where MWs are likely to be excited frequently throughout the year to discuss the likelihood of "MW hotspots" at various spatial scale. Graphical Abstract

scholarly journals ST radar observations of atmospheric waves over mountainous areas: a review

2000 ◽  
Vol 18 (7) ◽  
pp. 750-765 ◽  
Author(s):  
J. Röttger
Keyword(s):  
Middle Atmosphere ◽  
Lower Atmosphere ◽  
Mountainous Areas ◽  
Wave Processes ◽  
Mountain Areas ◽  
Mountain Waves ◽  
Propagating Waves ◽  
Lee Waves ◽  
Tropopause Region ◽  
Energy And Momentum

Abstract. Lee and mountain waves are dominant dynamic processes in the atmosphere above mountain areas. ST VHF radars had been intensively used to investigate these wave processes. These studies are summarized in this work. After discussing features of long-period quasi-stationary lee waves, attention is drawn to the frequent occurrence of freely propagating waves of shorter periods, which seem to be more common and characteristic for wave processes generated over mountainous areas. Characteristics of these waves such as their relation to the topography and background winds, the possibility of trapping by and breaking in the tropopause region and their propagation into the stratosphere is investigated. These orographically produced waves transport energy and momentum into the troposphere and stratosphere, which is considered an important contribution to the kinetic energy of the lower atmosphere. The occurrence of inertia-gravity waves in the stratosphere had been confused with lee waves, which is discussed in conclusion. Finally further questions on mountain and lee waves are drawn up, which remain to be solved and where investigations with ST radars could play a fundamental role.Key words: Meteorology and atmospheric dynamics (Middle atmosphere dynamics; Waves and tides; Instruments and techniques)

scholarly journals Verification of Near Surface Wind Patterns in Germany using Clear Air Radar Echoes

2021 ◽  
Author(s):  
Sebastian Buschow ◽  
Petra Friederichs
Keyword(s):  
Spatial Scales ◽  
Surface Wind ◽  
Horizontal Wind ◽  
Data Sets ◽  
Grey Zone ◽  
Wind Fields ◽  
Validation Data ◽  
Near Surface ◽  
Radar Echoes ◽  
Wind Patterns

Abstract. The verification of high-resolution meteorological models requires highly resolved validation data and appropriate tools of analysis. While much progress has been made in the case of precipitation, wind fields have received less attention, largely due to a lack of spatial measurements. Clear-sky radar echoes could be an unexpected part of the solution by affording us an indirect look at horizontal wind patterns: Regions of horizontal convergence attract non-meteorological scatterers such as insects; their concentration visualizes the structure of the convergence field. Using a two-dimensional wavelet transform, this study demonstrates how divergences and reflectivities can be quantitatively compared in terms of their spatial scale, (horizontal) anisotropy and direction. A long-term validation of the highly resolved regional reanalysis COSMO-REA2 against the German radar composite RADOLAN shows surprisingly close agreement. Despite theoretically predicted problems with simulations in or near the ‘grey-zone’ of turbulence, COSMO-REA2 is shown to produce a realistic diurnal cycle of the spatial scales larger than 8 km. In agreement with the literature, the orientation of the patterns in both data-sets closely follows the mean wind direction. Conversely, an analysis of the horizontal anisotropy reveals that the model has an unrealistic tendency towards highly linear, roll like patterns early in the day.

scholarly journals Characteristics of Stratospheric Winds over Jiuquan (41.1°N, 100.2°E) Using Rocketsonde Data in 1967–2004

2017 ◽  
Vol 34 (3) ◽  
pp. 657-667 ◽  
Author(s):  
Z. Sheng ◽  
J. W. Li ◽  
Y. Jiang ◽  
S. D. Zhou ◽  
W. L. Shi
Keyword(s):  
Zonal Wind ◽  
Middle Atmosphere ◽  
Correlation Coefficients ◽  
Meridional Wind ◽  
Horizontal Wind ◽  
Cycle Period ◽  
Observation Data ◽  
Wind Fields ◽  
Zonal Winds ◽  
Model Research

AbstractStratospheric winds play a significant role in middle atmosphere dynamics, model research, and carrier rocket experiments. For the first time, 65 sets of rocket sounding experiments conducted at Jiuquan (41.1°N, 100.2°E), China, from 1967 to 2004 are presented to study horizontal wind fields in the stratosphere. At a fixed height, wind speed obeys the lognormal distribution. Seasonal mean winds are westerly in winter and easterly in summer. In spring and autumn, zonal wind directions change from the upper to the lower stratosphere. The monthly zonal mean winds have an annual cycle period with large amplitudes at high altitudes. The correlation coefficients for zonal winds between observations and the Horizontal Wind Model (HWM) with all datasets are 0.7. The MERRA reanalysis is in good agreement with rocketsonde data according to the zonal winds comparison with a coefficient of 0.98. The sudden stratospheric warming is an important contribution to biases in the HWM, because it changes the zonal wind direction in the midlatitudes. Both the model and the reanalysis show dramatic meridional wind differences with the observation data.

scholarly journals Frequency variations of gravity waves interacting with a time-varying tide

2013 ◽  
Vol 31 (10) ◽  
pp. 1731-1743 ◽  
Author(s):  
C. M. Huang ◽  
S. D. Zhang ◽  
F. Yi ◽  
K. M. Huang ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Frequency Variation ◽  
Time Varying ◽  
Transient Nature ◽  
Critical Layers ◽  
Favorable Conditions ◽  
Frequency Variations

Abstract. Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

scholarly journals Verifying Operational Forecasts of Land–Sea-Breeze and Boundary Layer Mixing Processes

2020 ◽  
Vol 35 (4) ◽  
pp. 1427-1445
Author(s):  
Ewan Short
Keyword(s):  
Boundary Layer ◽  
Diurnal Cycle ◽  
Spatial Scales ◽  
Sea Breeze ◽  
Absolute Error ◽  
Wind Fields ◽  
Mixing Processes ◽  
Relative Contribution ◽  
The Mean ◽  
Diurnal Wind

AbstractForecasters working for Australia’s Bureau of Meteorology (BoM) produce a 7-day forecast in two key steps: first they choose a model guidance dataset to base the forecast on, and then they use graphical software to manually edit these data. Two types of edits are commonly made to the wind fields that aim to improve how the influences of boundary layer mixing and land–sea-breeze processes are represented in the forecast. In this study the diurnally varying component of the BoM’s official wind forecast is compared with that of station observations and unedited model guidance datasets. Coastal locations across Australia over June, July, and August 2018 are considered, with data aggregated over three spatial scales. The edited forecast produces a lower mean absolute error than model guidance at the coarsest spatial scale (over 50 000 km2), and achieves lower seasonal biases over all spatial scales. However, the edited forecast only reduces errors or biases at particular times and locations, and rarely produces lower errors or biases than all model guidance products simultaneously. To better understand physical reasons for biases in the mean diurnal wind cycles, modified ellipses are fitted to the seasonally averaged diurnal wind temporal hodographs. Biases in the official forecast diurnal cycle vary with location for multiple reasons, including biases in the directions that sea breezes approach coastlines, amplitude biases, and disagreement in the relative contribution of sea-breeze and boundary layer mixing processes to the mean diurnal cycle.

scholarly journals Identifying Potential Landslides by Stacking-InSAR in Southwestern China and Its Performance Comparison with SBAS-InSAR

2021 ◽  
Vol 13 (18) ◽  
pp. 3662
Author(s):  
Lele Zhang ◽  
Keren Dai ◽  
Jin Deng ◽  
Daqing Ge ◽  
Rubing Liang ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Detailed Comparison ◽  
Performance Comparison ◽  
Small Displacement ◽  
Mountainous Areas ◽  
Technical Requirements ◽  
Local Residents ◽  
Time Series Method ◽  
Sbas Insar ◽  
High Consistency

Landslide disasters occur frequently in the mountainous areas in southwest China, which pose serious threats to the local residents. Interferometry Synthetic Aperture Radar (InSAR) provides us the ability to identify active slopes as potential landslides in vast mountainous areas, to help prevent and mitigate the disasters. Quickly and accurately identifying potential landslides based on massive SAR data is of great significance. Taking the national highway near Wenchuan County, China, as study area, this paper used a Stacking-InSAR method to quickly and qualitatively identify potential landslides based on a total of 40 Sentinel SAR images acquired from November 2017 to March 2019. As a result, 72 active slopes were successfully detected as potential landslides. By comparing the results from Stacking-InSAR with the results from the traditional SBAS-InSAR (Small Baselines Subset) time series method, it was found that the two methods had a high consistency, with 81.7% potential landslides identified by both of the two methods. A detailed comparison on the detection differences was performed, revealing that Stacking-InSAR, compared to SBAS-InSAR may miss a few active slopes with small spatial scales, small displacement levels and the ones affected by the atmosphere, while it has good performance on poor-coherence regions, with the advantages of low technical requirements and low computation labor. The Stacking-InSAR method would be a fast and powerful method to qualitatively and effectively identify potential landslides in vast mountainous areas, with a comprehensive understanding of its specialty and limitations.

scholarly journals Analyzing the basic meteorological aspects of a particulate air pollution episode over the industrial area of Northwestern Greece during the November of 2009

2013 ◽  
Vol 15 (2) ◽  
pp. 241-253 ◽  
Keyword(s):  
Air Pollution ◽  
Particulate Matter ◽  
Wind Field ◽  
Lower Troposphere ◽  
Airborne Particulate Matter ◽  
Radical Change ◽  
Industrial Area ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Pollution Episode

The complex terrain basin of Amyntaio – Ptolemais – Kozani in Western Macedonia of Greece is an area characterized by increased industrial activity and therefore it demands continuous and assiduous environmental monitoring. A prolonged particulate matter air pollution episode was recorded in the area during November 2009. Basic meteorological aspects are analyzed, during the episode period. Daily and hourly PM10 and PM2.5 concentration measurements were used along with surface and lower atmosphere hourly meteorological parameters from 13 measuring stations. The observational data were supported by data produced by the meteorological component of an air pollution model. The overall analysis showed that the episode was primarily the result of the synoptic setting of the middle and lower troposphere. An Omega blocking pattern which gradually transformed to a high-over-low pattern prevailed over central and southern Europe during the episode’s period. The examination of the vertical wind field in the lower troposphere and appropriate stability indices, revealed a continuous absence of significant convection. The weak horizontal wind field near the surface and the reduced mixing height combined with the lack of synoptic forcing resulted in the trapping of the pollutants in the lower troposphere and the recording of increased airborne particulate matter concentrations. The radical change of the synoptic setting in the first days of December marked the end of the episode.

Impacts of Assimilating Measurements of Different State Variables with a Simulated Supercell Storm and Three-Dimensional Variational Method

2013 ◽  
Vol 141 (8) ◽  
pp. 2759-2777 ◽  
Author(s):  
Guoqing Ge ◽  
Jidong Gao ◽  
Ming Xue
Keyword(s):  
Potential Temperature ◽  
Three Dimensional ◽  
Horizontal Wind ◽  
Cold Pool ◽  
State Variables ◽  
Wind Fields ◽  
Simulation Experiments ◽  
Supercell Storm ◽  
The Impact ◽  
Analysis Quality

Abstract This paper investigates the impacts of assimilating measurements of different state variables, which can be potentially available from various observational platforms, on the cycled analysis and short-range forecast of supercell thunderstorms by performing a set of observing system simulation experiments (OSSEs) using a storm-scale three-dimensional variational data assimilation (3DVAR) method. The control experiments assimilate measurements every 5 min for 90 min. It is found that the assimilation of horizontal wind can reconstruct the storm structure rather accurately. The assimilation of vertical velocity , potential temperature , or water vapor can partially rebuild the thermodynamic and precipitation fields but poorly retrieves the wind fields. The assimilation of rainwater mixing ratio can build up the precipitation fields together with a reasonable cold pool but is unable to properly recover the wind fields. Overall, data have the greatest impact, while have the second largest impact. The impact of is the smallest. The impact of assimilation frequency is examined by comparing results using 1-, 5-, or 10-min assimilation intervals. When is assimilated every 5 or 10 min, the analysis quality can be further improved by the incorporation of additional types of observations. When are assimilated every minute, the benefit from additional types of observations is negligible, except for . It is also found that for , , and measurements, more frequent assimilation leads to more accurate analyses. For and , a 1-min assimilation interval does not produce a better analysis than a 5-min interval.

Determining wind fields in atmospheric mountain waves using sailplane flight data

2012 ◽  
Author(s):  
Ni Zhang ◽  
Rick P. Millane ◽  
Einar Enevoldson ◽  
James E. Murray
Keyword(s):  
Wind Fields ◽  
Mountain Waves ◽  
Flight Data
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