scholarly journals Observational study for strong downslope wind event under fine weather condition during ICE-POP 2018

2021 ◽  
Author(s):  
Chia-Lun Tsai ◽  
Kwonil Kim ◽  
Yu-Chieng Liou ◽  
Jung-Hoon Kim ◽  
YongHee Lee ◽  
...  
Keyword(s):  
Surface Wind ◽  
Weather Condition ◽  
Gradient Force ◽  
Mountain Range ◽  
Strong Wind ◽  
Mountainous Areas ◽  
Budget Analysis ◽  
Fine Weather ◽  
Wind Event ◽  
Downslope Wind

Abstract. A strong downslope wind event under fine weather condition on 13–15 February 2018 was examined by various observational and high resolution reanalysis datasets during the 2018 Winter Olympic and Paralympic games in Pyeongchang, Korea. High spatio-temporal resolution of wind information was obtained by Doppler lidars, automatic weather stations (AWS), wind profiler, and sounding observations under the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games (ICE-POP 2018). This study aimed to understand the possible generation mechanisms of localized strong wind event across high mountainous areas and in the lee side of mountains associated with the underlying large-scale pattern of a low-pressure system (LPS). The spatial distribution of linear trends for surface wind shows different patterns, exhibiting increased trend in the lee side and a persistent one in mountainous areas with the approaching LPS. Surface wind speed was intensified dramatically from ~3 to ~12 m s−1 (gust was stronger than 20 m s−1 above ground) at a surface station in the lee side (named as GWW). However, the mountainous station at DGW site appeared to have a persistently strong wind (~10 m s−1) during the research period. Budget analysis of horizontal momentum equation and local reanalysis data suggests that the pressure gradient force (PGF) derived by adiabatic warming along the downslope and subsequent hydraulic jump in the lee side of mountains was a main factor in the acceleration of the surface wind at the GWW site. Detailed analysis of the retrieved 3D winds reveals that the PGF also dominate at the DGW site, which causes the persistent strong wind that is related to the channeling effect across the valley areas in the mountain range. The observational evidence presented here shows that the different mechanisms in local areas under the same synoptic condition with LPS are important references in determining the strength and persistence of the orographic-induced strong winds under fine weather condition.

scholarly journals The Inland Eyewall Reintensification of Typhoon Fanapi (2010) Documented from an Observational Perspective Using Multiple-Doppler Radar and Surface Measurements

2015 ◽  
Vol 144 (1) ◽  
pp. 241-261 ◽  
Author(s):  
Yu-Chieng Liou ◽  
Tai-Chi Chen Wang ◽  
Pei-Yu Huang
Keyword(s):  
Large Scale ◽  
Doppler Radar ◽  
Mountain Range ◽  
Strong Wind ◽  
Horizontal Advection ◽  
Vertical Advection ◽  
Leading Role ◽  
Positive Vorticity ◽  
Budget Analysis ◽  
Western Side

Abstract This study documents observational changes in the eyewall of Typhoon Fanapi (2010) after landfall in Taiwan. The observations indicate that Fanapi’s eye and eyewall disappeared on the eastern side of Taiwan’s Central Mountain Range (CMR) after landfall, but reemerged on the western side of CMR. The cyclonic circulation, increasing wind speed, a low-level low pressure and high temperature zone, the associated updrafts and downdrafts, and surface pressure and rainfall measurements all support the existence of a reintensified eyewall. The storm slowed down during the redeveloping stage, thus prolonging the rainfall duration over Taiwan. On the western side of CMR a northwest–southeast-oriented rainband formed at an earlier stage, possibly due to the large-scale interaction between Fanapi’s remnant flow and the environment. However, the subsequent reintensification might be attributed to the interaction between the circulation and topography. This is supported by the finding that adjacent to CMR, strong wind develops vertically from lower levels, indicating that the reintensification appears to be initiated through a bottom-up process. A vorticity budget analysis shows that at lower layers the stretching mechanism plays a leading role in increasing positive vorticity, followed by the contributions from tilting and horizontal advection. The horizontal advection plays a comparable role to the vertical advection in increasing low- to midlevel vorticity. The vertical advection aloft is responsible for transporting the vorticity upward. Finally, this research provides a relatively rare documentation of the vortical hot towers (VHTs) over terrain using ground-based radars, in contrast to most previous studies focusing on maritime VHTs using simulations or aircraft measurements.

A Case Study of Strong Wind Event over Yeongdong Region on March 18-20, 2020

2021 ◽  
Vol 42 (5) ◽  
pp. 479-495
Author(s):  
Bo-Yeong Ahn ◽  
Yoo-Jun Kim ◽  
Baek-Jo Kim ◽  
Yong-Hee Lee
Keyword(s):  
Strong Wind ◽  
Wind Event

scholarly journals Short-term changes in the mesozooplankton community and copepod gut pigment in the Chukchi Sea in autumn: reflections of a strong wind event

2015 ◽  
Vol 12 (13) ◽  
pp. 4005-4015 ◽  
Author(s):  
K. Matsuno ◽  
A. Yamaguchi ◽  
S. Nishino ◽  
J. Inoue ◽  
T. Kikuchi
Keyword(s):  
Atmospheric Turbulence ◽  
Chukchi Sea ◽  
Strong Wind ◽  
Calanoid Copepods ◽  
Mesozooplankton Community ◽  
Chl A ◽  
Wind Event ◽  
Food Requirement ◽  
Copepodid Stage ◽  
Gut Pigment

Abstract. To evaluate the effect of atmospheric turbulence on a marine ecosystem, high-frequency samplings (two to four times per day) of a mesozooplankton community and the gut pigment of dominant copepods were performed at a fixed station in the Chukchi Sea from 10 to 25 September 2013. During the study period, a strong wind event (SWE) was observed on 18 September. After the SWE, the biomass of chlorophyll a (Chl a) increased, especially for micro-size (> 10 μm) fractions. The zooplankton abundance ranged from 23 610 to 56 809 ind. m−2 and exhibited no clear changes as a result of the SWE. In terms of abundance, calanoid copepods constituted the dominant taxa (mean: 57 %), followed by barnacle larvae (31 %). Within the calanoid copepods, small-sized Pseudocalanus spp. (65 %) and large-sized C. glacialis (30 %) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with the SWE. The dominance of accumulated lipids in C5 and C6 females with immature gonads indicated that they were preparing for seasonal diapause. The gut pigment of C. glacialis C5 was higher at night and was correlated with ambient Chl a (Chl a, and a significant increase was observed after the SWE (2.6 vs. 4.5 ng pigment ind.−1). The grazing impact by C. glacialis C5 was estimated to be 4.14 mg C m−2 day−1, which corresponded to 0.5−4.6 % of the biomass of the micro-size phytoplankton. Compared with the metabolic food requirement, C. glacialis feeding on phytoplankton accounted for 12.6 % of their total food requirement. These facts suggest that C. glacialis could not maintain their population by feeding solely on phytoplankton and that other food sources (i.e., microzooplankton) must be important in autumn. As observed by the increase in gut pigment, the temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition.

scholarly journals The Synoptic and Mesoscale Evolution Accompanying the 2018 Camp Fire of Northern California

2020 ◽  
pp. 1-45
Author(s):  
Clifford F. Mass ◽  
David Ovens
Keyword(s):  
Sierra Nevada ◽  
Northern California ◽  
Wind Event ◽  
Downslope Wind

CapsuleThe Camp Fire of November 2018 was associated with a strong, well-forecast, downslope wind event over the western slopes of the Sierra Nevada near Paradise, California.

The Probability Distribution of Land Surface Wind Speeds

2011 ◽  
Vol 24 (15) ◽  
pp. 3892-3909 ◽  
Author(s):  
Adam H. Monahan ◽  
Yanping He ◽  
Norman McFarlane ◽  
Aiguo Dai
Keyword(s):  
Boundary Layer ◽  
Weibull Distribution ◽  
Land Surface ◽  
Wind Shear ◽  
Surface Wind ◽  
Nocturnal Boundary Layer ◽  
Global Network ◽  
Strong Wind ◽  
Wind Speeds ◽  
Tropospheric Wind

Abstract The probability density function (pdf) of land surface wind speeds is characterized using a global network of observations. Daytime surface wind speeds are shown to be broadly consistent with the Weibull distribution, while nighttime surface wind speeds are generally more positively skewed than the corresponding Weibull distribution (particularly in summer). In the midlatitudes, these strongly positive skewnesses are shown to be generally associated with conditions of strong surface stability and weak lower-tropospheric wind shear. Long-term tower observations from Cabauw, the Netherlands, and Los Alamos, New Mexico, demonstrate that lower-tropospheric wind speeds become more positively skewed than the corresponding Weibull distribution only in the shallow (~50 m) nocturnal boundary layer. This skewness is associated with two populations of nighttime winds: (i) strongly stably stratified with strong wind shear and (ii) weakly stably or unstably stratified with weak wind shear. Using an idealized two-layer model of the boundary layer momentum budget, it is shown that the observed variability of the daytime and nighttime surface wind speeds can be accounted for through a stochastic representation of intermittent turbulent mixing at the nocturnal boundary layer inversion.

A numerical simulation of a strong wind event in January 2013 at King Sejong station, Antarctica

2019 ◽  
Vol 145 (720) ◽  
pp. 1267-1280
Author(s):  
Hataek Kwon ◽  
Sang‐Jong Park ◽  
Solji Lee ◽  
Baek‐Min Kim ◽  
Taejin Choi ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Strong Wind ◽  
Wind Event

scholarly journals Classification of Active Fires and Weather Conditions in the Lower Amur River Basin

2020 ◽  
Vol 12 (19) ◽  
pp. 3204
Author(s):  
Hiroshi Hayasaka ◽  
Galina V. Sokolova ◽  
Andrey Ostroukhov ◽  
Daisuke Naito
Keyword(s):  
River Basin ◽  
Boreal Forests ◽  
Weather Condition ◽  
Weather Forecast ◽  
Weather Conditions ◽  
Amur River Basin ◽  
Fire Weather ◽  
Strong Wind ◽  
Amur River ◽  
Active Fire

Most wildland fires in boreal forests occur during summer, but major fires in the lower Amur River Basin of the southern Khabarovsk Krai (SKK) mainly occur in spring. To reduce active fires in the SKK, we carried out daily analysis of MODIS (Moderate Resolution Imaging Spectroradiometer) hotspot (HS) data and various weather charts. HS data of 17 years from 2003 were used to identify the average seasonal fire occurrence. Active fire-periods were extracted by considering the number of daily HSs and their continuity. Weather charts, temperature maps, and wind maps during the top 12 active fire-periods were examined to clarify each fire weather condition. Analysis results showed that there were four active fire-periods that occurred in April, May, July, and October. Weather charts during the top active fire-periods showed active fires in April and October occurred under strong wind conditions (these wind velocities were over 30 km h−1) related to low-pressure systems. The very active summer fire at the end of June 2012 occurred related to warm air mass advection promoted by large westerly meandering. We showed clear fire weather conditions in the SKK from March to October. If a proper fire weather forecast is developed based on our results, more efficient and timely firefighting can be carried out.

scholarly journals Case Study of a Barrier Wind Corner Jet off the Coast of the Prince Olav Mountains, Antarctica

2012 ◽  
Vol 140 (7) ◽  
pp. 2044-2063 ◽  
Author(s):  
Melissa A. Nigro ◽  
John J. Cassano ◽  
Matthew A. Lazzara ◽  
Linda M. Keller
Keyword(s):  
Strong Wind ◽  
Ice Shelf ◽  
Maximum Wind ◽  
Ross Ice Shelf ◽  
Wind Speeds ◽  
Wind Event ◽  
Transantarctic Mountains ◽  
Upper Level ◽  
Forcing Mechanisms

Abstract The Ross Ice Shelf airstream (RAS) is a barrier parallel flow along the base of the Transantarctic Mountains. Previous research has hypothesized that a combination of katabatic flow, barrier winds, and mesoscale and synoptic-scale cyclones drive the RAS. Within the RAS, an area of maximum wind speed is located to the northwest of the protruding Prince Olav Mountains. In this region, the Sabrina automatic weather station (AWS) observed a September 2009 high wind event with wind speeds in excess of 20 m s−1 for nearly 35 h. The following case study uses in situ AWS observations and output from the Antarctic Mesoscale Prediction System to demonstrate that the strong wind speeds during this event were caused by a combination of various forcing mechanisms, including katabatic winds, barrier winds, a surface mesocyclone over the Ross Ice Shelf, an upper-level ridge over the southern tip of the Ross Ice Shelf, and topographic influences from the Prince Olav Mountains. These forcing mechanisms induced a barrier wind corner jet to the northwest of the Prince Olav Mountains, explaining the maximum wind speeds observed in this region. The RAS wind speeds were strong enough to induce two additional barrier wind corner jets to the northwest of the Prince Olav Mountains, resulting in a triple barrier wind corner jet along the base of the Transantarctic Mountains.

Downslope Flows on a Low-Angle Slope and Their Interactions with Valley Inversions. Part II: Numerical Modeling

2008 ◽  
Vol 47 (7) ◽  
pp. 2039-2057 ◽  
Author(s):  
Shiyuan Zhong ◽  
C. David Whiteman
Keyword(s):  
Wind Speed ◽  
Pressure Gradient ◽  
Buoyancy Force ◽  
Atmospheric Modeling ◽  
Gradient Force ◽  
Ambient Atmosphere ◽  
Pressure Gradient Force ◽  
Small Contribution ◽  
Downslope Winds ◽  
Downslope Wind

Abstract The characteristics of well-developed downslope winds observed by tethered balloon soundings at multiple locations over a low-angle slope in the Salt Lake Valley are studied using the Regional Atmospheric Modeling System (RAMS). The model successfully simulated the key properties of the observed wind and temperature structure and evolution and provided insight into the forcing mechanisms. The results show that, although the slope angle is only 1.6°, the buoyancy force associated with the local temperature perturbation caused by nocturnal cooling of the slope surface is capable of producing the unusually strong and deep downslope winds observed by the tethersondes. The hypothesis that the flow is produced locally by the temperature deficit is further confirmed by analysis of the momentum budget that indicates a very small contribution from advection to the downslope mass flux. The analysis also reveals the importance of the along-slope pressure gradient force, which has been neglected by some previous investigators. On an isolated slope, the pressure gradient force, which develops as the downslope-flow layer deepens with downslope distance, is important mostly in the upper part of the downslope wind layer where it counterbalances the buoyancy force. On a slope in a valley, the pressure gradient force interacts with the valley inversion to produce intermittency in the downslope jet and may also significantly slow the flow as the inversion strengthens during the night. The simulations for two different observational nights indicate that the maximum downslope wind speed is sensitive to ambient stability, with near-neutral ambient stability yielding a stronger downslope jet than does a more stable ambient atmosphere. Sensitivity studies suggest that an increase in down-valley winds leads to a decrease in the maximum downslope wind speed and an increase in the thickness of the downslope wind layer. An increase in slope roughness, on the other hand, increases the height of the downslope jet but has little effect on other properties. The downslope wind is stronger over a gentle 1.6° slope than over a much steeper slope of 11°, mainly because of the combination of the stronger buoyancy and weaker pressure gradient over the gentle slope.

scholarly journals A regional real-time forecast of marine boundary layers during VOCALS-REx

2011 ◽  
Vol 11 (2) ◽  
pp. 421-437 ◽  
Author(s):  
S. Wang ◽  
L. W. O'Neill ◽  
Q. Jiang ◽  
S. P. de Szoeke ◽  
X. Hong ◽  
...  
Keyword(s):  
Real Time ◽  
Large Scale ◽  
Marine Boundary Layer ◽  
Surface Wind ◽  
Lower Troposphere ◽  
Temporal Distribution ◽  
Satellite Observations ◽  
Naval Research ◽  
Strong Wind

Abstract. This paper presents an evaluation and validation of the Naval Research Laboratory's COAMPS® real-time forecasts during the VOCALS-REx over the area off the west coast of Chile/Peru in the Southeast Pacific during October and November 2008. The analyses focus on the marine boundary layer (MBL) structure. These forecasts are compared with lower troposphere soundings, in situ surface measurements, and satellite observations. The predicted mean MBL cloud and surface wind spatial distributions are in good agreement with the satellite observations. The large-scale longitudinal variation of the MBL structure along 20° S is captured by the forecasts. That is, the MBL height increases westward toward the open ocean, the moisture just above the inversion decreases, and the MBL structure becomes more decoupled offshore. The observed strong wind shear across the cloud-top inversion near 20° S was correctly predicted by the model. The model's cloud spatial and temporal distribution in the 15 km grid mesh is sporadic compared to satellite observations. Our results suggest that this is caused by grid-scale convection likely due to a lack of a shallow cumulus convection parameterization in the model. Both observations and model forecasts show wind speed maxima near the top of MBL along 20° S, which is consistent with the westward upslope of the MBL heights based on the thermal wind relationship. The forecasts produced well-defined diurnal variations in the spatially-averaged MBL structure, although the overall signal is weaker than those derived from the in situ measurements and satellite data. The MBL heights are generally underpredicted in the nearshore area. An analysis of the sensitivity of the MBL height to horizontal and vertical grid resolution suggests that the underprediction is likely associated with overprediction of the mesoscale downward motion and cold advection near the coast.

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