scholarly journals Initial-Condition Sensitivities and the Predictability of Downslope Winds

2009 ◽  
Vol 66 (11) ◽  
pp. 3401-3418 ◽  
Author(s):  
Patrick A. Reinecke ◽  
Dale R. Durran
Keyword(s):  
Wave Breaking ◽  
Initial Conditions ◽  
Static Stability ◽  
Synoptic Scale ◽  
Wind Speeds ◽  
Downslope Winds ◽  
First Case ◽  
Downslope Wind ◽  
The Difference ◽  
Strong Winds

Abstract The sensitivity of downslope wind forecasts to small changes in initial conditions is explored by using 70-member ensemble simulations of two prototypical windstorms observed during the Terrain-Induced Rotor Experiment (T-REX). The 10 weakest and 10 strongest ensemble members are composited and compared for each event. In the first case, the 6-h ensemble-mean forecast shows a large-amplitude breaking mountain wave and severe downslope winds. Nevertheless, the forecasts are very sensitive to the initial conditions because the difference in the downslope wind speeds predicted by the strong- and weak-member composites grows to larger than 28 m s−1 over the 6-h forecast. The structure of the synoptic-scale flow one hour prior to the windstorm and during the windstorm is very similar in both the weak- and strong-member composites. Wave breaking is not a significant factor in the second case, in which the strong winds are generated by a layer of high static stability flowing beneath a layer of weaker mid- and upper-tropospheric stability. In this case, the sensitivity to initial conditions is weaker but still significant. The difference in downslope wind speeds between the weak- and strong-member composites grows to 22 m s−1 over 12 h. During and one hour before the windstorm, the synoptic-scale flow exhibits appreciable differences between the strong- and weak-member composites. Although this case appears to be more predictable than the wave-breaking event, neither case suggests that much confidence should be placed in the intensity of downslope winds forecast 12 or more hours in advance.

Does steep terrain influence tree stability? A field investigation

2005 ◽  
Vol 35 (10) ◽  
pp. 2360-2367 ◽  
Author(s):  
Bruce C Nicoll ◽  
Alexis Achim ◽  
Shaun Mochan ◽  
Barry A Gardiner
Keyword(s):  
Mineral Soil ◽  
Field Investigation ◽  
Picea Sitchensis ◽  
Risk Modelling ◽  
Tree Stability ◽  
Wind Speeds ◽  
Hinge Point ◽  
Downslope Winds ◽  
Downslope Wind ◽  
Steep Terrain

The anchorage of 40-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees grown in a plantation on a steep (ca. 30°) slope was compared with that of trees grown on an adjacent horizontal area. There was similar gleyed mineral soil on the sloping and horizontal areas. Trees were mechanically overturned using a winch, and anchorage was quantified by measuring load, stem angle, and tree dimensions. Trees on the slope were overturned upslope, downslope, or across-slope. Critical turning moments were calculated around the tree base and the actual hinge point. Critical wind speeds required to uproot or snap trees in this stand were modelled to compare the vulnerability of trees to upslope and downslope winds. No overall difference in anchorage was found between trees grown on the horizontal and sloping parts of the site. However, for trees on the slope, those pulled upslope showed significantly more resistance to overturning for a given stem mass than those pulled downslope. Critical turning moments calculated at the hinge point were smaller than those calculated at the stem base, but differences were small and had no effect on the comparison between treatments. Critical wind speeds for uprooting were estimated to be 28 m·s–1 for an upslope wind and 24 m·s–1 for a downslope wind on this site. The implications of these results are discussed in relation to windthrow-risk modelling and forest soil conservation.

scholarly journals Characteristics of Extratropical Cyclones That Cause Tornadoes in Italy: A Preliminary Study

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 180
Author(s):  
Eigo Tochimoto ◽  
Mario Marcello Miglietta ◽  
Leonardo Bagaglini ◽  
Roberto Ingrosso ◽  
Hiroshi Niino
Keyword(s):  
Environmental Conditions ◽  
Convective Available Potential Energy ◽  
Static Stability ◽  
Extratropical Cyclones ◽  
Cool Season ◽  
Southeastern Us ◽  
Different Seasons ◽  
The Difference ◽  
Upper Level ◽  
Strong Evaporation

Characteristics of extratropical cyclones that cause tornadoes in Italy are investigated. Tornadoes between 2007 and 2016 are analyzed, and statistical analysis of the associated cyclone structures and environments is performed using the JRA-55 reanalysis. Tornadoes are distributed sporadically around the cyclone location within a window of 10° × 10°. The difference in the cyclone tracks partially explains the seasonal variability in the distribution of tornadoes. The highest number of tornadoes occur south of the cyclone centers, mainly in the warm sector, while a few are observed along the cold front. Composite mesoscale parameters are examined to identify the environmental conditions associated with tornadoes in different seasons. Potential instability is favorable to tornado development in autumn. The highest convective available potential energy (CAPE) in this season is associated with relatively high-temperature and humidity at low-levels, mainly due to the strong evaporation over the warm Mediterranean Sea. Upper-level potential vorticity (PV) anomalies and the associated cold air reduce the static stability above the cyclone center, mainly in spring and winter. On average, the values of CAPE are lower than for US tornadoes and comparable with those occurring in Japan, while storm relative helicity (SREH) is comparable with US tornadoes and higher than Japanese tornadoes, indicating that the environmental conditions for Italian tornadoes have peculiar characteristics. Overall, the conditions emerging in this study are close to the high-shear, low-CAPE environments typical of cool-season tornadoes in the Southeastern US.

scholarly journals Air Movement in Snow Due to Windpumping

1989 ◽  
Vol 35 (120) ◽  
pp. 209-213 ◽  
Author(s):  
S.C. Colbeck
Keyword(s):  
Pore Space ◽  
Barometric Pressure ◽  
Surface Flows ◽  
Wind Speeds ◽  
Compression And Expansion ◽  
Strong Winds ◽  
Pressure Changes ◽  
Low Amplitude ◽  
Pressure Perturbations ◽  
Rapid Pressure

Abstract Strong winds can disrupt the thermal regime in seasonal snow because of the variation in surface pressure associated with surface features like dunes and ripples. Topographical features of shorter wavelengths produce stronger surface flows, but the flow decays rapidly with depth. Longer-wavelength features produce weaker surface flows but the flow decays more slowly with depth. The flow may only be strong enough to disrupt the temperature field for features of wavelengths on the scale of meters or tens of meters at wind speeds of 10 m/s or more. Other possible causes of windpumping have been examined but they do not appear to be as significant. Rapid pressure perturbations due to turbulence produce very little displacement of the air because of the high frequency and low amplitude. Barometric pressure changes cause compression and expansion of the air in the pore space, but the rate is too low to have much effect.

Movement of Large Convective Rainstorms in Relation to Winds Aloft

1958 ◽  
Vol 39 (3) ◽  
pp. 129-136 ◽  
Author(s):  
C. W. Newton ◽  
Sey Katz
Keyword(s):  
Wind Speed ◽  
Wind Direction ◽  
Rainfall Data ◽  
Squall Lines ◽  
Hourly Rainfall ◽  
The Difference ◽  
Strong Winds

By means of hourly rainfall data from the Hydroclimatic Network, the motions of large rainstorms, of the kind associated with squall lines, are examined in relation to the winds aloft. Very little correlation is found between the speed of movement of the rainstorms and the wind speed at any level, although the fastest moving storms were associated with strong winds aloft. Significant correlation is found between direction of motion of rainstorms, and wind direction at 700 mb or higher levels. On the average, the rainstorms move with an appreciable component toward right of the wind direction. The difference between these results, and those from other studies based on small precipitation areas, is ascribed to propagation. The mechanism involved is discussed briefly.

scholarly journals Meteorological conditions over Antarctic blue-ice areas and their influence on the local surface mass balance

2001 ◽  
Vol 47 (156) ◽  
pp. 37-50 ◽  
Author(s):  
Richard Bintanja ◽  
Carleen H. Reijmer
Keyword(s):  
Mass Balance ◽  
Low Frequency ◽  
Meteorological Conditions ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Wind Speeds ◽  
Dry Conditions ◽  
The Difference ◽  
Sublimation Rates ◽  
Different Characteristics

AbstractThis paper addresses the causes of the prevailing meteorological conditions observed over an Antarctic blue-ice area and their effect on the surface mass balance. Over blue-ice areas, net accumulation is zero and ablation occurs mainly through sublimation. Sublimation rates are much higher than over adjacent snowfields. The meteorological conditions favourable for high sublimation rates (warm, dry and gusty) are due to the specific orographic setting of this blue-ice area, with usually a steep upwind mountainous slope causing strong adiabatic heating. Diabatic warming due to radiation, and entrainment of warm air from aloft into the boundary layer augment the warming. The prevailing warm, dry conditions explain roughly 50% of the difference in sublimation, and the different characteristics of blue ice (mainly its lower albedo) the other 50%. Most of the annual sublimation (∼70%) takes place during the short summer (mainly in daytime), with winter ablation being restricted to occasional warm, dry föhn-like events. The additional moisture is effectively removed by entrainment and horizontal advection, which are maximum over the blue-ice area. Low-frequency turbulent motions induced by the upwind mountains enhance the vertical turbulent transports. Strong gusts and high peak wind speeds over blue-ice areas cause high potential snowdrift transports, which can easily remove the total precipitation, thereby maintaining zero accumulation.

Climate Conditions at Perennially Ice-Covered Lake Untersee, East Antarctica

2015 ◽  
Vol 54 (7) ◽  
pp. 1393-1412 ◽  
Author(s):  
Dale T. Andersen ◽  
Christopher P. McKay ◽  
Victor Lagun
Keyword(s):  
Wind Speed ◽  
Austral Summer ◽  
Solar Flux ◽  
East Antarctica ◽  
Daily Maximum ◽  
Mean Annual Temperature ◽  
Secondary Source ◽  
Climate Conditions ◽  
Wind Speeds ◽  
Strong Winds

AbstractIn November 2008 an automated meteorological station was established at Lake Untersee in East Antarctica, producing a 5-yr data record of meteorological conditions at the lake. This dataset includes five austral summer seasons composed of December, January, and February (DJF). The average solar flux at Lake Untersee for the four years with complete solar flux data is 99.2 ± 0.6 W m−2. The mean annual temperature at Lake Untersee was determined to be −10.6° ± 0.6°C. The annual degree-days above freezing for the five years were 9.7, 37.7, 22.4, 7.0, and 48.8, respectively, with summer (DJF) accounting for virtually all of this. For these five summers the average DJF temperatures were −3.5°, −1.9°, −2.2°, −2.6°, and −2.5°C. The maximum (minimum) temperatures were +5.3°, +7.6°, +5.7°, +4.4°, and +9.0°C (−13.8°, −12.8°, −12.9°, −13.5°, and −12.1°C). The average of the wind speed recorded was 5.4 m s−1, the maximum was 35.7 m s−1, and the average daily maximum was 15 m s−1. The wind speed was higher in the winter, averaging 6.4 m s−1. Summer winds averaged 4.7 m s−1. The dominant wind direction for strong winds is from the south for all seasons, with a secondary source of strong winds in the summer from the east-northeast. Relative humidity averages 37%; however, high values will occur with an average period of ~10 days, providing a strong indicator of the quasi-periodic passage of storms across the site. Low summer temperatures and high wind speeds create conditions at the surface of the lake ice resulting in sublimation rather than melting as the main mass-loss process.

INHERITED FACTOR-VII DEFECT IN A NEGRO FAMILY

PEDIATRICS ◽  
1961 ◽  
Vol 27 (2) ◽  
pp. 204-213
Author(s):  
Helen I. Glueck ◽  
James M. Sutherland
Keyword(s):  
Prothrombin Time ◽  
Factor Vii ◽  
Homozygous State ◽  
Control Value ◽  
One Stage ◽  
First Case ◽  
Severe Deficiency ◽  
Low Levels ◽  
The Difference ◽  
The One

A case of factor-VII deficiency of a congenital nature in a Negro male child has been reported. As far as can be determined, this is the first case reported in this race. The defect was detected at 6 hours of age. Prothrombin, as contrasted to factor VII, after initially low levels normally found in infants, rose to adult levels. The patient's one-stage prothrombin time has ranged between 25 to 35 second (normal 11 to 12 seconds). In spite of this, he has never shown any manifestations of hemorrhage. The patient's family was studied and the findings indicate that the patient's defect represented a homozygous state and that both parents with a less severe deficiency were heterozygous for the trait. The defect is an autosomal disorder directly inherited. It is clinically apparent and easily detected only in the homozygous state. The heterozygous state is characterized by a very slight prolongation of the one-stage prothrombin time, the difference from the control value being so minimal as to be overlooked. In one subject studied, an aunt of the propositus, the quantitative defect (42% of normal) could not be regularly detected by the usual methods. Only by using the plasma of the propositus as the test plasma, was the defect in her plasma detected, thus explaining the transmission of the trait to her offspring. These findings explain the difficulties previously encountered in understanding the inheritance of the disorder.

scholarly journals Internal volumetric heat generation and heat capacity prediction during a material electromagnetic treatment process using hybrid algorithms

2018 ◽  
Vol 38 (1) ◽  
pp. 74-82
Author(s):  
Edgar García-Morantes ◽  
Iván Amaya-Contreras ◽  
Rodrigo Correa-Cely
Keyword(s):  
Inverse Problem ◽  
Heat Capacity ◽  
Electromagnetic Field ◽  
Heat Generation ◽  
Initial Conditions ◽  
Limited Range ◽  
First Case ◽  
Realistic Situation ◽  
Wide Range ◽  
Volumetric Heat Generation

This work considers the estimation of internal volumetric heat generation, as well as the heat capacity of a solid spherical sample, heated by a homogeneous, time-varying electromagnetic field. To that end, the numerical strategy solves the corresponding inverse problem. Three functional forms (linear, sinusoidal, and exponential) for the electromagnetic field were considered. White Gaussian noise was incorporated into the theoretical temperature profile (i.e. the solution of the direct problem) to simulate a more realistic situation. Temperature was pretended to be read through four sensors. The inverse problem was solved through three different kinds of approach: using a traditional optimizer, using modern techniques, and using a mixture of both. In the first case, we used a traditional, deterministic Levenberg-Marquardt (LM) algorithm. In the second one, we considered three stochastic algorithms: Spiral Optimization Algorithm (SOA), Vortex Search (VS), and Weighted Attraction Method (WAM). In the final case, we proposed a hybrid between LM and the metaheuristics algorithms. Results show that LM converges to the expected solutions only if the initial conditions (IC) are within a limited range. Oppositely, metaheuristics converge in a wide range of IC but exhibit low accuracy. The hybrid approaches converge and improve the accuracy obtained with the metaheuristics. The difference between expected and obtained values, as well as the RMS errors, are reported and compared for all three methods.

scholarly journals Relationship between Sea Surface Drag Coefficient and Wave State

2021 ◽  
Vol 9 (11) ◽  
pp. 1248
Author(s):  
Jian Shi ◽  
Zhihao Feng ◽  
Yuan Sun ◽  
Xueyan Zhang ◽  
Wenjing Zhang ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Momentum Flux ◽  
Sea Surface ◽  
Sea Spray ◽  
Wave Age ◽  
High Wind ◽  
Surface Drag ◽  
Wave State ◽  
Wind Speeds ◽  
Strong Winds

The sea surface drag coefficient plays an important role in momentum transmission between the atmosphere and the ocean, which is affected by ocean waves. The total air–sea momentum flux consists of effective momentum flux and sea spray momentum flux. Sea spray momentum flux involves sea surface drag, which is largely affected by the ocean wave state. Under strong winds, the sea surface drag coefficient (CD) does not increase linearly with the increasing wind speed, namely, the increase of CD is inhibited by strong winds. In this study, a sea surface drag coefficient is constructed that can be applied to the calculation of the air–sea momentum flux under high wind speed. The sea surface drag coefficient also considers the influence of wave state and sea spray droplets generated by wave breaking. Specially, the wave-dependent sea spray generation function is employed to calculate sea spray momentum flux. This facilitates the analysis not only on the sensitivity of the sea spray momentum flux to wave age, but also on the effect of wave state on the effective CD (CD, eff) under strong winds. Our results indicate that wave age plays an important role in determining CD. When the wave age is >0.4, CD decreases with the wave age. However, when the wave age is ≤0.4, CD increases with the wave age at low and moderate wind speeds but tends to decrease with the wave age at high wind speeds.

scholarly journals Clinical Characteristics and CT Manifestations of 143 Patients With 2019 Novel Coronavirus Disease (COVID-19) in Taizhou City, Zhejiang, China

2020 ◽  
Author(s):  
Yani Kuang ◽  
Susu He ◽  
Shuangxiang Lin ◽  
Rui Zhu ◽  
Rongzhen Zhou ◽  
...  
Keyword(s):  
Clinical Symptoms ◽  
Protein A ◽  
Clinical Manifestations ◽  
Imaging Features ◽  
First Case ◽  
Severe Group ◽  
Laboratory Examinations ◽  
The Difference ◽  
Severity Of The Disease ◽  
Novel Coronavirus

Abstract Background: In December 2019, the first case of pneumonia associated with the SARS-CoV-2 was found in Wuhan and rapidly spread throughout China, so data are needed on the affected patients. The purpose of our study was to find the clinical manifestations and CT features of COVID-19.Methods: All patients with COVID-19 in Taizhou city were retrospectively included and divided into non-severe group and severe group according to the severity of the disease. The clinical manifestations, laboratory examinations and imaging features of COVID-19 patients were analyzed, and the differences between the two groups were compared.Results: A total of 143 laboratory-confirmed cases were included in the study, including 110 non-severe patients and 33 severe patients. The median age of patients was 47 (range 4–86 years). Fever (73.4%) and cough (63.6%) were the most common initial clinical symptoms. Between two groups of cases, the results of aspartate transaminase, creatine kinase and lactate dehydrogenase, serum albumin, CR, glomerular filtration rate, amyloid protein A, fibrinogen, calcitonin level and oxygen partial pressure, IL – 10, absolute value of CD3, CD4, CD8 were different, and the difference was statistically significant (P < 0.05). Therefore, these quantitative indicators can be used to help assess the severity. On admission, the CT showed that the lesions were mostly distributed in the periphery of the lung or subpleural (135 cases (98%)), and most of lesions presented as patchy (81%), mixed density (63%) shadow. Consolidation (68% vs 41%), bronchial inflation signs (59% vs 41%), and bronchiectasis (71% vs 39%) were more common in the severe group.Conclusions: Most of the cases of COVID-19 in Taizhou have mild symptoms and no death. In addition to clinical symptoms, some laboratory tests (such as absolute values of CD4 and CD8) and CT findings can be used to assess the severity of the disease.

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