scholarly journals Regional Variability of Rain Clouds in the Amazon Basin as Seen by a Network of Weather Radars

2016 ◽  
Vol 55 (12) ◽  
pp. 2657-2675 ◽  
Author(s):  
I. Saraiva ◽  
M. A. F. Silva Dias ◽  
C. A. R. Morales ◽  
J. M. B. Saraiva
Keyword(s):  
Heavy Rainfall ◽  
Amazon Basin ◽  
Radar Reflectivity ◽  
Northern Coast ◽  
Regional Variability ◽  
Convective Systems ◽  
Diurnal Cycles ◽  
Weather Radars ◽  
Vertical Distributions ◽  
The Vertical Distribution

AbstractA new dataset based on 5 yr of operational meteorological weather radars from the Amazon Protection System has enabled new knowledge in relation to rainfall in the Amazon basin. The rainy features are analyzed for 10 different regions in terms of the annual and diurnal cycles of radar reflectivity, as well as the vertical distribution, in addition to lightning data. Similarities between the annual and diurnal cycles are found in the northwestern and western, southwestern and southern, and northeastern and northern Amazon. Nocturnal peaks are found in stratiform fraction in the southern, southwestern, western, northwestern, northern, central western, and coastal regions. The convective fractions in the western, northwestern, northern, and central eastern regions also show nocturnal peaks. The radar reflectivity vertical distributions analysis indicates that in the northern coast close to Belém, heavy rainfall with deep convective systems is observed throughout the year, while heavy rainfall in the central Amazon close to Manaus, Tefé, and Santarém occurs in the dry season. More oceanic-like clouds are also observed there and in other locations on the northern coast like Macapá, where the frequency of lightning is quite low. São Gabriel da Cachoeira, located in the northwest portion of the Amazon basin, has a regime with rainfall in all seasons with a slight decrease from August to October when the systems become more convective and have more lightning.

scholarly journals An Observational Study of Mesoscale Convective Systems with Heavy Rainfall over the Korean Peninsula

2006 ◽  
Vol 21 (2) ◽  
pp. 125-148 ◽  
Author(s):  
Hyung Woo Kim ◽  
Dong Kyou Lee
Keyword(s):  
Observational Study ◽  
Korean Peninsula ◽  
Wind Shear ◽  
Heavy Rainfall ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Mesoscale Convective Systems ◽  
Low Level ◽  
Convective Systems ◽  
Mesoscale Convective

Abstract A heavy rainfall event induced by mesoscale convective systems (MCSs) occurred over the middle Korean Peninsula from 25 to 27 July 1996. This heavy rainfall caused a large loss of life and property damage as a result of flash floods and landslides. An observational study was conducted using Weather Surveillance Radar-1988 Doppler (WSR-88D) data from 0930 UTC 26 July to 0303 UTC 27 July 1996. Dominant synoptic features in this case had many similarities to those in previous studies, such as the presence of a quasi-stationary frontal system, a weak upper-level trough, sufficient moisture transportation by a low-level jet from a tropical storm landfall, strong potential and convective instability, and strong vertical wind shear. The thermodynamic characteristics and wind shear presented favorable conditions for a heavy rainfall occurrence. The early convective cells in the MCSs initiated over the coastal area, facilitated by the mesoscale boundaries of the land–sea contrast, rain–no rain regions, saturated–unsaturated soils, and steep horizontal pressure and thermal gradients. Two MCSs passed through the heavy rainfall regions during the investigation period. The first MCS initiated at 1000 UTC 26 July and had the characteristics of a supercell storm with small amounts of precipitation, the appearance of a mesocyclone with tilting storm, a rear-inflow jet at the midlevel of the storm, and fast forward propagation. The second MCS initiated over the upstream area of the first MCS at 1800 UTC 26 July and had the characteristics of a multicell storm, such as a broken areal-type squall line, slow or quasi-stationary backward propagation, heavy rainfall in a concentrated area due to the merging of the convective storms, and a stagnated cluster system. These systems merged and stagnated because their movement was blocked by the Taebaek Mountain Range, and they continued to develop because of the vertical wind shear resulting from a low-level easterly inflow.

Heavy rainfall in the northern coast of Ecuador in the aftermath of El Niño 2015/2016 and its predictability 

2021 ◽  
Author(s):  
Luis E. Pineda ◽  
Juan Changoluisa ◽  
Ángel G. Muñoz
Keyword(s):  
Heavy Rainfall ◽  
Heavy Rain ◽  
Rainfall Anomaly ◽  
Precipitation Event ◽  
Lead Times ◽  
Northern Coast ◽  
Atmospheric Conditions ◽  
The North ◽  
Ensemble Mean ◽  
Rainfall Anomalies

<p>In January 2016, a high precipitation event (HPE) affected the northern coast of Ecuador leading to devastating flooding in the Esmeraldas’ river basin. The HPE appeared in the aftermath of the 2015/2016 El Niño as an early onset of heavy rainfalls otherwise expected in the core rainy season (Mar-Apr). Using gauge data, satellite imagery and reanalysis we investigate the daily and ‘weather-within-climate’ characteristics of the HPE and its accompanying atmospheric conditions. The convective storms developed into a mesoscale convective complex (MCC) during nighttime on 24<sup>th</sup> January. The scale size of the heavy rainfall system was about 250 km with a lifecycle lasting 16 hours for the complete storm with 6 hours of convective showers contributing to the HPE. The genesis of the MCC was related to above-normal moisture and orographic lifting driving convective updrafts; the north-south mountain barrier acted as both a channel boosting upslope flow when it moves over hillslopes; and, as a heavy-rain divide for inner valleys. The above normal moisture conditions were favored by cross-time-scale interactions involving the very strong El Niño 2015/2016 event, an unusually persistent Madden–Julian oscillation (MJO) in phases 3 and 6, remotely forced by tropical synoptic scale disturbances. In the dissipation stage, a moderate low-level easterly shear with wind velocity of about 10 m/s moved away the unstable air and the convective pattern disappear on the shore of the Esmeraldas basin.</p><p> </p><p>We use ECMWF re-forecast from the Sub-seasonal to Seasonal (S2S) prediction project dataset and satellite observations to investigate the predictability of the HPE. Weekly ensemble-mean rainfall anomaly forecasts computed from raw (uncorrected) S2S reforecast initialized on 31st Dec 2015, 7th, 14th and 21st Jan 2016 are used to assess the occurrence of rainfall anomalies over the region. The reforecast represents consistently, over all lead times, the spatial pattern of the HPE. Also, the ensemble-mean forecast shows positive rainfall anomalies at times scales of 1-3 weeks (0-21 days) at nearly all initialization dates and lead times, predicting this way successfully the timing and amplitude of the highest HPE leading the 25th January flood.</p>

scholarly journals Cause Analysis on Eastward Movement of Southwest China Vortex and Its Induced Heavy Rainfall in South China

2015 ◽  
Vol 2015 ◽  
pp. 1-22 ◽  
Author(s):  
Yongren Chen ◽  
Yueqing Li ◽  
Tianliang Zhao
Keyword(s):  
South China ◽  
Heavy Rainfall ◽  
Southwest China ◽  
Dominant Role ◽  
Vertical Wind Shear ◽  
Heavy Rain ◽  
Convective Systems ◽  
Rainfall Occurrence ◽  
Positive Vorticity ◽  
Upper Level Jet

The movement of southwest China vortex (SWV) and its heavy rainfall process in South China had been investigated during June 11–14, 2008. The results show that under the steering of upper-level jet (ULJ) and mid-level westerly trough, SWV moved eastward from southern Sichuan Plateau, across eastern Yunnan-Guizhou Plateau to South China, forming an obvious heavy rain belt. SWV developed in the large storm-relative helicity (SRH) environment, as environmental wind field continuously transferred positive vorticity to it to support its development. The thermodynamic structures of distinctive warm (cold) advections in front (rear) of the SWV movement are also important factors for the SWV evolutions with a southwest low-level jet (LLJ) and vertical wind shear. SWV development was associated with the distributions of negative MPV1 (the barotropic item of moist potential vorticity) and positive MPV2 (the baroclinic item of it). The MPV1 and MPV2 played the dominant role in the formation and the evolution of SWV, respectively. The mesoscale convective systems (MCSs) frequently occurred and persisted in water vapor convergence areas causing the severe heavy rainfall. The areas of high moist helicity divergence and heavy rainfall are consistent, and the moist helicity divergence could be a good indicator for heavy rainfall occurrence.

The Bow and Arrow Mesoscale Convective Structure

2013 ◽  
Vol 141 (5) ◽  
pp. 1648-1672 ◽  
Author(s):  
Kelly M. Keene ◽  
Russ S. Schumacher
Keyword(s):  
Heavy Rainfall ◽  
Prediction Models ◽  
Weather Prediction ◽  
Warm Season ◽  
Severe Weather ◽  
Cold Pool ◽  
Horizontal Shear ◽  
Convective Systems ◽  
Wind Speeds ◽  
Bow And Arrow

Abstract The accurate prediction of warm-season convective systems and the heavy rainfall and severe weather associated with them remains a challenge for numerical weather prediction models. This study looks at a circumstance in which quasi-stationary convection forms perpendicular to, and above the cold-pool behind strong bow echoes. The authors refer to this phenomenon as a “bow and arrow” because on radar imagery the two convective lines resemble an archer’s bow and arrow. The “arrow” can produce heavy rainfall and severe weather, extending over hundreds of kilometers. These events are challenging to forecast because they require an accurate forecast of earlier convection and the effects of that convection on the environment. In this study, basic characteristics of 14 events are documented, and observations of 4 events are presented to identify common environmental conditions prior to the development of the back-building convection. Simulations of three cases using the Weather Research and Forecasting Model (WRF) are analyzed in an attempt to understand the mechanisms responsible for initiating and maintaining the convective line. In each case, strong southwesterly flow (inducing warm air advection and gradual isentropic lifting), in addition to directional and speed convergence into the convective arrow appear to contribute to initiation of convection. The linear orientation of the arrow may be associated with a combination of increased wind speeds and horizontal shear in the arrow region. When these ingredients are combined with thermodynamic instability, there appears to be a greater possibility of formation and maintenance of a convective arrow behind a bow echo.

scholarly journals Diet of Bryconops alburnoides and B. caudomaculatus (Osteichthyes: Characiformes) in the region affected by Balbina Hydroelectric Dam (Amazon drainage, Brazil)

2008 ◽  
Vol 6 (2) ◽  
pp. 237-242 ◽  
Author(s):  
Cylene C. da Silva ◽  
Efrem J. G. Ferreira ◽  
Cláudia P. de Deus
Keyword(s):  
Heavy Rainfall ◽  
Amazon Basin ◽  
Relative Volume ◽  
Fish Diet ◽  
Frequency Of Occurrence ◽  
Important Data ◽  
Hydroelectric Dam ◽  
Morisita Index ◽  
Terrestrial Insects ◽  
And Behavior

The study of fish diet and its interaction with the environment provides important data on ecology and behavior, as fish face varying environmental and food availability conditions. The aim of the present study was to determine the diet of Bryconops caudomaculatus and Bryconops alburnoides, as well as to assess its seasonal variation, within the area influenced by Balbina Hydroelectric Dam (BHD), in the Uatumã River (Amazon Basin, Brazil). Collections were carried out every two months from April 2005 to February 2007, using gill nets with mesh sizes ranging from 12 to 60 mm between opposite knots. Two methods were used for determining diet: frequency of occurrence and relative volume, which were used to calculate the alimentary index (IAi). Diet similarity between species was analyzed by applying the Morisita index. Bryconops alburnoides ingested 12 items and B. caudomaculatus 10, with a 59% similarity between ingested items. Terrestrial insects for B. alburnoides and immature insects for B. caudomaculatus were the main items in their diets, and therefore, they were considered insectivorous. The seasonal composition of the diet of B. alburnoides was influenced by environmental factors, and in spite of the dominance of immature insects, it had a significant number of terrestrial insects during the heavy rainfall periods.

scholarly journals Regional co-variability of spatial and temporal soil moisture–precipitation coupling in North Africa: an observational perspective

2018 ◽  
Vol 22 (6) ◽  
pp. 3275-3294 ◽  
Author(s):  
Irina Y. Petrova ◽  
Chiel C. van Heerwaarden ◽  
Cathy Hohenegger ◽  
Françoise Guichard
Keyword(s):  
Soil Moisture ◽  
North Africa ◽  
Deep Convection ◽  
Sensible Heat Flux ◽  
Arid Environment ◽  
The South ◽  
Regional Variability ◽  
Convective Systems ◽  
The North ◽  
Temporal Coupling

Abstract. The magnitude and sign of soil moisture–precipitation coupling (SMPC) is investigated using a probability-based approach and 10 years of daily microwave satellite data across North Africa at a 1∘ horizontal scale. Specifically, the co-existence and co-variability of spatial (i.e. using soil moisture gradients) and temporal (i.e. using soil moisture anomaly) soil moisture effects on afternoon rainfall is explored. The analysis shows that in the semi-arid environment of the Sahel, the negative spatial and the negative temporal coupling relationships do not only co-exist, but are also dependent on one another. Hence, if afternoon rain falls over temporally drier soils, it is likely to be surrounded by a wetter environment. Two regions are identified as SMPC “hot spots”. These are the south-western part of the domain (7–15∘ N, 10∘ W–7∘ E), with the most robust negative SMPC signal, and the South Sudanese region (5–13∘ N, 24–34∘ E). The sign and significance of the coupling in the latter region is found to be largely modulated by the presence of wetlands and is susceptible to the number of long-lived propagating convective systems. The presence of wetlands and an irrigated land area is found to account for about 30 % of strong and significant spatial SMPC in the North African domain. This study provides the first insight into regional variability of SMPC in North Africa, and supports the potential relevance of mechanisms associated with enhanced sensible heat flux and mesoscale variability in surface soil moisture for deep convection development.

Probable Causes for the 1972 Red Tide in the Cape Ann Region of the Gulf of Maine

1973 ◽  
Vol 30 (9) ◽  
pp. 1363-1366 ◽  
Author(s):  
Hugh Francis Mulligan
Keyword(s):  
Deep Water ◽  
Heavy Rainfall ◽  
Gulf Of Maine ◽  
Red Tide ◽  
Hydrographic Data ◽  
Water Development ◽  
Seed Population ◽  
Causative Factors ◽  
Vertical Distributions

Hydrographic data and spatial, temporal, and vertical distributions of Gonyaulax tamarensis are presented from the vicinity of Cape Ann, Massachusetts in summer of 1972. When considered together with available meteorological records, these data provide information on probable causes and development of the September 1972 red tide bloom in the Gulf of Maine. An upwelling of deep water, development of a "seed" population of G. tamarensis during unusually dry weather in August, and heavy rainfall in September are suggested as the three causative factors.

Radar Reflectivity of Lightning Flashes in Stratiform Regions of Mesoscale Convective Systems

2019 ◽  
Vol 124 (24) ◽  
pp. 14114-14132
Author(s):  
Fei Wang ◽  
Hengyi Liu ◽  
Wansheng Dong ◽  
Yijun Zhang ◽  
Wen Yao ◽  
...  
Keyword(s):  
Radar Reflectivity ◽  
Mesoscale Convective Systems ◽  
Convective Systems ◽  
Mesoscale Convective

scholarly journals Mesoscale Convective Systems: A Case Scenario of the ‘Heavy Rainfall’ Event of 15–20 January 2013 over Southern Africa

Climate ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 73
Author(s):  
Modise Wiston ◽  
Kgakgamatso Marvel Mphale
Keyword(s):  
Atlantic Ocean ◽  
Southern Africa ◽  
Heavy Rainfall ◽  
Rainfall Event ◽  
Mesoscale Convective Systems ◽  
Heavy Rainfall Event ◽  
Convergence Zone ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Upper Level

Southern east Africa is prone to some extreme weather events and interannual variability of the hydrological cycle, including tropical cyclones and heavy rainfall events. Most of these events occur during austral summer and are linked to shifts in the intertropical convergence zone, changes in El Niño Southern Oscillation signatures, sea surface temperature and sea level pressure. A typical example include mesoscale convective systems (MCSs) that occur between October and March along the eastern part, adjacent to the warm waters of Mozambique Channel and Agulhas Current. In this study we discuss a heavy rainfall event over southern Africa, focusing particularly on the period 15–20 January 2013, the period during which MCSs were significant over the subcontinent. This event recorded one of the historic rainfalls due to extreme flooding and overflows, loss of lives and destruction of economic and social infrastructure. An active South Indian Convergence Zone was associated with the rainfall event sustained by a low-level trough linked to a Southern Hemisphere planetary wave pattern and an upper-level ridge over land. In addition, also noteworthy is a seemingly strong connection to the strength of the African Easterly Jet stream. Using rainfall data, satellite imagery and re-analysis (model processed data combined with observations) data, our analysis indicates that there was a substantial relation between rainfall totals recorded/observed and the presence of MCSs. The low-level trough and upper-level ridge contributed to moisture convergence, particularly from tropical South East Atlantic Ocean, which in turn contributed to the prolonged life span of the rainfall event. Positive temperature anomalies favored the substantial contribution of moisture fluxes from the Atlantic Ocean. This study provides a contextual assessment of rainfall processes and insight into the physical control mechanisms and feedback of large-scale convective interactions over tropical southern Africa.

Variations of the Local Failure Pressure With Depth Through First-Year and Multi-Year Ice

1988 ◽  
Vol 110 (2) ◽  
pp. 159-168 ◽  
Author(s):  
D. Blanchet
Keyword(s):  
Ice Thickness ◽  
First Year ◽  
Strain Rates ◽  
Failure Pressure ◽  
Pressure Profiles ◽  
Vertical Distributions ◽  
Pressure Area ◽  
Ice Floes ◽  
Ice Pressure ◽  
The Vertical Distribution

Typical vertical distributions of the failure pressure in an ice sheet are presented. The distributions, derived for intermediate strain rates, are a function of many parameters, namely, the salinity, the temperature, the type of ice, the location of the ice pressure area through the ice thickness, the thickness of ice, the density, and the crack and flaw distributions. Two combinations of these parameters lead to “representative” summer and winter vertical ice pressure profiles for 8 and 2-m thick ice floes. The importance of the vertical distribution of the failure pressure inside an ice cover is fundamental for two reasons. The change in the eccentricity of the resultant of the load induces changes in failure mode and load transmission to the structure. This nonuniform distribution will create nonsimultaneous failure and the ice pressure on the structure will not be hydrostatically distributed over a given area.

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