Severe convective storms and wind damage assessment over northwestern Poland

2020 ◽  
Author(s):  
Christelle Castet
Keyword(s):  
Large Scale ◽  
Surface Wind ◽  
Careful Analysis ◽  
Wind Damage ◽  
Primary Concern ◽  
Wind Fields ◽  
Convective Storms ◽  
Good Proxy ◽  
Northwestern Poland ◽  
Convective Cells

<p>Severe convective storms (SCS) cause widespread damages over Europe each year and can be responsible for billions of euros in losses. In addition, the expected increase in their frequency and intensity over the century represents a primary concern for insurers.</p><p>Parametric insurance, which compensates customers when an index reaches a predefined threshold, is a fast and transparent insurance solution, that requires a careful analysis of the risk and a correlation of the index with potential damages. For instance, to protect customers against wind related damages from SCS, an index based on wind speed could be used. Unfortunately, the modeling of precise surface wind fields associated with SCS remains a challenge and sources of observation are often patchy or not reliable. The goal is then to define a parameter that can be used to estimate the potential wind damage from SCS.</p><p>Relying on a 10-year climatology of lightning activity over Poland, our approach consists first in determining large scale environmental variables in the ERA5 reanalysis favorable to the occurrence of SCS. Then, a combination of variable is tested in correlation with wind related damages. Preliminary results suggest that lightning density is a good proxy to the intensity of convective cells, and to a lesser extent to wind related damages.</p>

scholarly journals Bi-modal Structure and Variability of Large-Scale Diabatic Heating in the Tropics

2009 ◽  
Vol 66 (12) ◽  
pp. 3621-3640 ◽  
Author(s):  
Chidong Zhang ◽  
Samson M. Hagos
Keyword(s):  
Large Scale ◽  
Diabatic Heating ◽  
Function Analysis ◽  
Surface Wind ◽  
Building Blocks ◽  
Wind Fields ◽  
Balanced Model ◽  
Heating Profiles ◽  
The Tropics ◽  
Rotated Empirical Orthogonal Function

Abstract Tropical diabatic heating profiles estimated using sounding data from eight field campaigns were diagnosed to document their common and prevailing structure and variability that are relevant to the large-scale circulation. The first two modes of a rotated empirical orthogonal function analysis—one deep, one shallow—explain 85% of the total variance of all data combined. These two modes were used to describe the heating evolution, which led to three composited heating profiles that are considered as prevailing large-scale heating structures. They are, respectively, shallow, bottom heavy (peak near 700 hPa); deep, middle heavy (peak near 400 hPa); and stratiform-like, top heavy (heating peak near 400 hPa and cooling peak near 700 hPa). The amplitudes and occurrence frequencies of the shallow, bottom-heavy heating profiles are comparable to those of the stratiform-like, top-heavy ones. The sequence of the most probable heating evolution is deep tropospheric cooling to bottom-heavy heating, to middle heavy heating, to stratiform-like heating, then back to deep tropospheric cooling. This heating transition appears to occur on different time scales. Each of the prevailing heating structures is interpreted as being composed of particular fractional populations of various types of precipitating cloud systems, which are viewed as the building blocks for the mean. A linear balanced model forced by the three prevailing heating profiles produces rich vertical structures in the circulation with multiple overturning cells, whose corresponding moisture convergence and surface wind fields are very sensitive to the heating structures.

scholarly journals Physical processes controlling the diurnal cycle of convective storms in the Western Ghats

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
U. V. Murali Krishna ◽  
Subrata Kumar Das ◽  
Sachin M. Deshpande ◽  
G. Pandithurai
Keyword(s):  
Diurnal Variation ◽  
Diurnal Cycle ◽  
Western Ghats ◽  
Large Scale ◽  
Monsoon Season ◽  
Surface Wind ◽  
Bimodal Distribution ◽  
Early Morning ◽  
Coastal Areas ◽  
Convective Storms

AbstractDiurnal variation of convective storms (CSs) during monsoon season and associated physical mechanisms are significantly important for accurate forecast of short-time and extreme precipitation. The diurnal cycle of CSs is investigated using ground-based X-band radar, Tropical Rainfall Measuring Mission Precipitation Radar, and reanalysis data during the summer monsoon (June–September of 2014) over complex mountain terrain of Western Ghats, India. Diurnally, CSs show a bimodal distribution in the coastal areas, but this bimodality became weak along the upslope regions and on the mountain top. The first occurrence mode of CSs is in the afternoon–evening hours, while the second peak is in the early-morning hours. The diurnal cycle’s intensity varies with location, such that it reaches maximum in the afternoon–evening hours and early morning on the mountain top and coastal areas, respectively. Two possible mechanisms are proposed for the observed diurnal variation in CSs (a) the radiative cooling effect and (b) the surface wind convergence induced by the interaction between land-sea breeze, local topography and large-scale monsoon winds. It is also observed that the CSs developed on the mountain top during afternoon–evening hours are deeper than those along the coast. The higher moisture in the lower- and mid-troposphere, higher instability and strong upward motion facilitate deeper CSs during afternoon–evening hours.

scholarly journals Air-Sea Interactions over Eddies in the Brazil-Malvinas Confluence

2021 ◽  
Vol 13 (7) ◽  
pp. 1335
Author(s):  
Ronald Souza ◽  
Luciano Pezzi ◽  
Sebastiaan Swart ◽  
Fabrício Oliveira ◽  
Marcelo Santini
Keyword(s):  
Latent Heat ◽  
Large Scale ◽  
Surface Wind ◽  
Heat Fluxes ◽  
Lower Atmosphere ◽  
Meteorological Variables ◽  
Global Ocean ◽  
Study Region ◽  
Cold Core

The Brazil–Malvinas Confluence (BMC) is one of the most dynamical regions of the global ocean. Its variability is dominated by the mesoscale, mainly expressed by the presence of meanders and eddies, which are understood to be local regulators of air-sea interaction processes. The objective of this work is to study the local modulation of air-sea interaction variables by the presence of either a warm (ED1) and a cold core (ED2) eddy, present in the BMC, during September to November 2013. The translation and lifespans of both eddies were determined using satellite-derived sea level anomaly (SLA) data. Time series of satellite-derived surface wind data, as well as these and other meteorological variables, retrieved from ERA5 reanalysis at the eddies’ successive positions in time, allowed us to investigate the temporal modulation of the lower atmosphere by the eddies’ presence along their translation and lifespan. The reanalysis data indicate a mean increase of 78% in sensible and 55% in latent heat fluxes along the warm eddy trajectory in comparison to the surrounding ocean of the study region. Over the cold core eddy, on the other hand, we noticed a mean reduction of 49% and 25% in sensible and latent heat fluxes, respectively, compared to the adjacent ocean. Additionally, a field campaign observed both eddies and the lower atmosphere from ship-borne observations before, during and after crossing both eddies in the study region during October 2013. The presence of the eddies was imprinted on several surface meteorological variables depending on the sea surface temperature (SST) in the eddy cores. In situ oceanographic and meteorological data, together with high frequency micrometeorological data, were also used here to demonstrate that the local, rather than the large scale forcing of the eddies on the atmosphere above, is, as expected, the principal driver of air-sea interaction when transient atmospheric systems are stable (not actively varying) in the study region. We also make use of the in situ data to show the differences (biases) between bulk heat flux estimates (used on atmospheric reanalysis products) and eddy covariance measurements (taken as “sea truth”) of both sensible and latent heat fluxes. The findings demonstrate the importance of short-term changes (minutes to hours) in both the atmosphere and the ocean in contributing to these biases. We conclude by emphasizing the importance of the mesoscale oceanographic structures in the BMC on impacting local air-sea heat fluxes and the marine atmospheric boundary layer stability, especially under large scale, high-pressure atmospheric conditions.

Early Accusations of Well Poisoning against Jews: Medieval Reality or Historiographical Fiction?

2016 ◽  
Vol 22 (5) ◽  
pp. 517-539
Author(s):  
Tzafrir Barzilay
Keyword(s):  
Early Modern ◽  
Fourteenth Century ◽  
Large Scale ◽  
Eleventh Century ◽  
Early Modern Period ◽  
Careful Analysis ◽  
Modern Period ◽  
Reliable Evidence

This article reexamines the idea prevalent in existing historiography that Jews were accused of well poisoning before 1321. It argues that the historians who studied the origins of such accusations were misled by sources written in the early modern period to think that Jews were charged with well poisoning as early as the eleventh century. However, a careful analysis of the sources reveals that there is little reliable evidence that such cases happened before the fourteenth century, much less on a large scale. Thus, the conclusions of the article call for a new chronology of well-poisoning charges made against Jews, starting closer to the fourteenth century.

scholarly journals Influence of El Niño Wind Stress Anomalies on South Brazil Bight Ocean Volume Transports

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Luiz Paulo de Freitas Assad ◽  
Carina Stefoni Böck ◽  
Rogerio Neder Candella ◽  
Luiz Landau
Keyword(s):  
Stress Field ◽  
Interannual Variability ◽  
Wind Stress ◽  
Large Scale ◽  
Time Lag ◽  
Surface Wind ◽  
Circulation Model ◽  
Volume Transport ◽  
Wind Stress Field ◽  
Volume Transports

The knowledge of wind stress variability could represent an important contribution to understand the variability over upper layer ocean volume transports. The South Brazilian Bight (SBB) circulation had been studied by numerous researchers who predominantly attempted to estimate its meridional volume transport. The main objective and contribution of this study is to identify and quantify possible interannual variability in the ocean volume transport in the SBB induced by the sea surface wind stress field. A low resolution ocean global circulation model was implemented to investigate the volume transport variability. The results obtained indicate the occurrence of interannual variability in meridional ocean volume transports along three different zonal sections. These results also indicate the influence of a wind driven large-scale atmospheric process that alters locally the SBB and near-offshore region wind stress field and consequently causes interannual variability in the upper layer ocean volume transports. A strengthening of the southward flow in 25°S and 30°S was observed. The deep layer ocean volume transport in the three monitored sections indicates a potential dominance of other remote ocean processes. A small time lag between the integrated meridional volume transports changes in each monitored zonal section was observed.

Changes in mechanisms and intensity of Western U.S. floods, 1960-2013

2021 ◽  
Author(s):  
Jessica Fayne ◽  
Huilin Huang ◽  
Mike Fischella ◽  
Yufei Liu ◽  
Zhaoxin Ban ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
Critical Factor ◽  
Flood Frequency ◽  
Atmospheric Rivers ◽  
Convective Storms ◽  
Noticeable Increase ◽  
Complex Interactions ◽  
Different Types ◽  
The Impact

<p>Extreme precipitation, a critical factor in flooding, has selectively increased with warmer temperatures in the Western U.S. Despite this, the streamflow measurements have captured no noticeable increase in large-scale flood frequency or intensity. As flood studies have mostly focused on specific flood events in particular areas, analyses of large-scale floods and their changes have been scarce. For floods during 1960-2013, we identify six flood generating mechanisms (FGMs) that are prominent across the Western U.S., including atmospheric rivers and non-atmospheric rivers, monsoons, convective storms, radiation-driven snowmelt, and rain-on-snow, in order to identify to what extent different types of floods are changing based on the dominant FGM. The inconsistency between extreme precipitation and lack of flood increase suggests that the impact of climate change on flood risk has been modulated by hydro-meteorological and physiographic processes such as sharp increases in temperature that drive increased evapotranspiration and decreased soil moisture. Our results emphasize the importance of FGMs in understanding the complex interactions of flooding and climatic changes and explain the broad spatiotemporal changes that have occurred across the vast Western U.S. for the past 50 years.</p>

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 Characteristics of Strong Updrafts in Precipitation Systems over the Central Tropical Pacific Ocean and in the Amazon

2005 ◽  
Vol 44 (5) ◽  
pp. 731-738 ◽  
Author(s):  
Nicholas F. Anderson ◽  
Cedric A. Grainger ◽  
Jeffrey L. Stith
Keyword(s):  
Mass Flux ◽  
Large Scale ◽  
Tropical Rainfall Measuring Mission ◽  
Maximum Speed ◽  
Tropical Pacific Ocean ◽  
Wet Season ◽  
Average Speed ◽  
Convective Storms ◽  
Similarities And Differences

Abstract Airborne in situ measurements of updrafts in tropical convective storms were analyzed to determine the similarities and differences between updrafts in a tropical continental and a tropical oceanic region. Two hundred fifteen updraft cores from the Tropical Rainfall Measuring Mission (TRMM) component of the Large Scale Biosphere–Atmosphere (LBA) experiment (tropical continental wet season) and 377 updraft cores from the Kwajalein Experiment (KWAJEX) (tropical oceanic) were analyzed in a similar manner to that of previous studies of tropical updrafts. Average speed, maximum speed, width, and mass flux of the updraft cores from the TRMM-LBA and KWAJEX were generally similar to each other and also were similar to results from previous studies of tropical updrafts.

scholarly journals Mechanism of large-scale flow reversals in turbulent thermal convection

2018 ◽  
Vol 4 (11) ◽  
pp. eaat7480 ◽  
Author(s):  
Yin Wang ◽  
Pik-Yin Lai ◽  
Hao Song ◽  
Penger Tong
Keyword(s):  
Thermal Convection ◽  
Large Scale ◽  
Careful Analysis ◽  
Extreme Value Statistics ◽  
Convection Cell ◽  
Heat Accumulation ◽  
Thermal Plumes ◽  
Minute Amount ◽  
Large Scale Flow ◽  
Experimental Findings

It is commonly believed that heat flux passing through a closed thermal convection system is balanced so that the convection system can remain at a steady state. Here, we report a new kind of convective instability for turbulent thermal convection, in which the convective flow stays over a long steady “quiet period” having a minute amount of heat accumulation in the convection cell, followed by a short and intermittent “active period” with a massive eruption of thermal plumes to release the accumulated heat. The rare massive eruption of thermal plumes disrupts the existing large-scale circulation across the cell and resets its rotational direction. A careful analysis reveals that the distribution of the plume eruption amplitude follows the generalized extreme value statistics with an upper bound, which changes with the fluid properties of the convecting medium. The experimental findings have important implications to many closed convection systems of geophysical scale, in which massive eruptions and sudden changes in large-scale flow pattern are often observed.

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