A Hydrometeorological Analysis of Venezuelan Rainfall *

1949 ◽  
Vol 30 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Robert D. Fletcher
Keyword(s):  
Correlation Coefficient ◽  
Drainage Basin ◽  
Intertropical Convergence Zone ◽  
Annual Rainfall ◽  
Trade Wind ◽  
Convergence Zone ◽  
Trade Winds ◽  
Weather Model ◽  
The Mean ◽  
Meteorological Analysis

A meteorological analysis is made of the general rainstorm of June 9–12, 1945, which produced substantial streamflow measurements over the Rio Tuy drainage basin of Venezuela. In this storm it appears that the intertropical convergence zone (ITC), in combination with the orography of the basin, was the weather model responsible for the rain. There is shown to be a high correlation (a coefficient of 0.73) between the mean-annual-rainfall pattern and that of the June 9–12 storm. The same correlation coefficient is found between the mean-annual pattern and that of another storm which occurred between June 28 and July 2, 1945. It is concluded that most general rainstorms over the Rio Tuy Basin occur when the ITC, oriented such that the trade winds are blowing almost directly from the east, lies just south of the basin; that the isohyetal patterns which result are very much alike; and that the magnitude of the rainfall varies with the strength of the trade-wind current flowing over the basin.

scholarly journals Climatologia da pluviometria do município de Teresina, Piauí, Brasil

2016 ◽  
Vol 11 (4) ◽  
pp. 135
Author(s):  
Hudson Ellen Alencar Menezes ◽  
Raimundo Mainar de Medeiros ◽  
José Lucas Guilherme Santos
Keyword(s):  
Water Resources ◽  
Rainfall Variability ◽  
Intertropical Convergence Zone ◽  
Atmospheric Dynamics ◽  
Rainfall Data ◽  
Annual Rainfall ◽  
Convergence Zone ◽  
Northeast Brazil ◽  
Urban Structures ◽  
Urbanized Areas

<p>As variações nas precipitações refletem claramente a dinâmica atmosférica da região, marcada pela intensa variabilidade, onde se observa a atuação da Zona de Convergência Intertropical (ZCIT) com sua atuação entre os meses de janeiro a março, sendo esse período mais chuvoso. As variabilidades espaço temporal no comportamento das chuvas tem sido analisadas e diagnosticadas por vários autores no Nordeste do Brasil (NEB), portanto objetivou-se diagnosticar a variabilidade dos índices pluviométricos em Teresina no Estado do Piauí no período de 1913 a 2010. A análise do comportamento da precipitação nas cidades de grande e médio porte é de extrema importância para o gerenciamento dos recursos hídricos, uma vez que se trata de áreas densamente urbanizadas. Muitas vezes, sem uma estruturação urbana adequada, estas cidades se encaixam perfeitamente nesse contexto. Foram utilizados dados mensais observados e anuais de precipitação pluviométrica no período de 1913 a 2010, com 97 anos de observações. Os resultados mostraram a recorrência de valores máximos de precipitação anual dentro de um intervalo de 18, 11 e 8 anos. Na análise dos desvios-padrões, os resultados mostraram predominância dos desvios negativos em relação aos desvios positivos.</p><p align="center"><strong><em>Climatology of rainfall in the Teresina city, Piauí state, Brazil</em></strong></p><p>Variations in precipitation clearly reflect the atmospheric dynamics of the region, marked by intense variability, where we observe the performance of the Intertropical Convergence Zone (ITCZ) with his performance in the months of January-March, this being more rain tem period. The timeline of rainfall variability in behavior has been analyzed and diagnosed by several authors in Northeast Brazil (NEB), so let's study this variability between the periods 1913 to 2010 of Teresina city.  The behavior of rainfall in cities large and medium sized is of utmost importance to the managerial of water resources, since it is densely urbanized areas. Often without adequate urban structures these cities fit perfectly in this context. We used observed monthly and annual rainfall data for the period 1913-2010, 97 years of observations. The results showed recurrence of maximum values of annual precipitation an interval of 18, 11 and 8 years. In the analysis of standard deviations, the results showed a predominance of negative deviations from the positive deviations.<strong></strong></p><p align="center"><strong><em><br /></em></strong></p>

scholarly journals Is the Recent Increasing Trend of Rainfall over Northeast Brazil Related to Sub-Saharan Drought?

2006 ◽  
Vol 19 (17) ◽  
pp. 4448-4453 ◽  
Author(s):  
V. Brahmananda Rao ◽  
Emanuel Giarolla ◽  
Mary T. Kayano ◽  
Sergio H. Franchito
Keyword(s):  
Correlation Coefficient ◽  
Confidence Level ◽  
Correlation Coefficients ◽  
Intertropical Convergence Zone ◽  
Convergence Zone ◽  
Northeast Brazil ◽  
Increasing Trend ◽  
Rainfall Variations ◽  
Sub Saharan ◽  
Normal Rainfall

Abstract In recent years, there has been an increase in rainfall over northeast Brazil (Nordeste), while over the sub-Saharan region there has been a drought. The correlation coefficients between the 11-yr running means of the rainfall series over the two regions are significant (at the 95% confidence level by a two-sided t test), suggesting that both trends are related. The rainfall variations over the two regions are connected to the position of the intertropical convergence zone (ITCZ) over the Atlantic. A more southward (northward) position of the ITCZ is favorable for higher than normal rainfall over Nordeste (sub-Sahara). The correlation coefficient between the position of the ITCZ over the Atlantic and the rainfall over Nordeste (sub-Sahara) is negative (positive) and highly significant, reaching values over 0.9. Thus, this study suggests that a more southward than normal location of the ITCZ in the Atlantic may be the cause for the recent increasing (decreasing) trend of rainfall over Nordeste (sub-Sahara).

scholarly journals One-year analysis of rain and rain erosivity in a tropical volcanic island from UHF wind profiler measurements

2013 ◽  
Vol 6 (2) ◽  
pp. 3249-3277 ◽  
Author(s):  
A. Réchou ◽  
M. Plu ◽  
B. Campistron ◽  
R. Decoupes
Keyword(s):  
Kinetic Energy ◽  
Rain Rate ◽  
Cold Front ◽  
Deep Convection ◽  
Trade Wind ◽  
Energy Fluxes ◽  
Trade Winds ◽  
Rainfall Events ◽  
The Mean ◽  
One Year

Abstract. La Réunion is a volcanic island in a tropical zone, which soil undergoes intense erosion. The possible contribution of rainfall to erosion is analyzed and quantified using one year of UHF radar profiler data located at sea level. Measurements of reflectivity, vertical and horizontal wind allow, with suitable assumptions, to determine raindrop vertical and horizontal energy fluxes, which are both essential parameters for erosion. After calibration of radar rain rates, one-year statistics between May 2009 to April 2010 allow to identify differences in rain vertical profiles depending on the season. During the cool dry season, the mean rain rate is less than 2.5 mm h−1 as high as 1.25 km and it decreases at higher altitudes due to the trade winds inversion. During the warm moist season, the mean rain rate is nearly uniform from ground up to 4 km, around 5 mm h−1. The dynamical and microphysical properties of rainfall events are investigated on three cases that are representative of meteorological events in La Réunion: summer deep convection, a cold front and a winter depression embedded in trade winds. For intense rainfall events, the rain rate deduced from the gamma function is in agreement with the rain rate deduced from the mere Marshall Palmer exponential relationship. For less intense events, the gamma function is necessary to represent rain distribution. The deep-convection event is associated to strong reflectivity reaching as high as 10 km, and strong negative vertical velocity. Wind shear is responsible for a deficiency of radar rain detection at the lower levels. During a cold front event, strong reflectivities reach the trade wind inversion (around 4 km high). The trade wind depression generates moderate rain only as high as 2 km. For all the altitudes, the horizontal kinetic energy fluxes are one order of magnitude stronger that than the vertical kinetic energy fluxes. A simple relationship between the reflectivity factor and vertical kinetic energy fluxes is found for each case study.

scholarly journals Objective Identification of the Intertropical Convergence Zone: Climatology and Trends from the ERA-Interim

2014 ◽  
Vol 27 (5) ◽  
pp. 1894-1909 ◽  
Author(s):  
Gareth Berry ◽  
Michael J. Reeder
Keyword(s):  
Climate Model ◽  
Southern Oscillation ◽  
Weather Prediction ◽  
Lower Troposphere ◽  
Intertropical Convergence Zone ◽  
Eastern Pacific ◽  
Tropical Cyclogenesis ◽  
Convergence Zone ◽  
Operational Forecasts ◽  
The Mean

Abstract An objective method for the identification of the intertropical convergence zone (ITCZ) in gridded numerical weather prediction datasets is presented. This technique uses layer- and time-averaged winds in the lower troposphere to automatically detect the location of the ITCZ and is designed for use with datasets including operational forecasts and climate model output. The method is used to create a climatology of ITCZ properties from the Interim ECMWF Re-Analysis (ERA-Interim) dataset for the period 1979–2009 to serve as an indicator of the technique's ability and a benchmark for future comparisons. The automatically generated objective climatology closely matches the results from subjective studies, showing a seasonal cycle in which the oceanic ITCZ migrates meridionally and the land-based ITCZ features are predominantly summertime phenomena. Composites based on the phase of the El Niño–Southern Oscillation index show a major shift in the mean position and changes in intensity of the ITCZ in all ocean basins as the index varies. Under La Niña conditions, the ITCZ intensifies over the Maritime Continent and eastern Pacific, where the ITCZ weakens over the central and equatorial eastern Pacific. An analysis of changes in the ITCZ and its divergence during the period 1979–2009 indicates that the mean position of the ITCZ shifts southward in the western Pacific and a broad global intensification of the convergence into ITCZ regions. The relationship between tropical cyclogenesis and the ITCZ is also examined, finding that more than 50% of all tropical cyclones form within 600 km of the ITCZ.

The climate of Aldabra Atoll

1971 ◽  
Vol 260 (836) ◽  
pp. 67-91 ◽  
Keyword(s):  
Annual Rainfall ◽  
Trade Wind ◽  
Positive Pressure ◽  
Wet Season ◽  
Climatic Effects ◽  
Early Afternoon ◽  
Summer Maximum ◽  
The Mean ◽  
Maximum Temperatures ◽  
Instrumental Records

Meteorological observations made by members of the expedition since August 1967 are the first to appear from Aldabra which cover a sufficient time span to merit analysis. Data for the period November 1967 to October 1968 are compared with marine derived parameters available from climatological atlases. Aldabra experiences a 5- or 6-month wet season in most years and its climate may be classified as V 2 /V 3 . During midsummer 1967/8 a marked positive pressure anomaly was observed: this coincided with a 3-month failure of the monsoon. For 7 months of the year the southeast trade winds blow, with a constancy of more than 90%. Summer maximum temperatures average 32 °C (90 °F) at the Settlement synoptic station, but this station is atypical for much of the atoll where maximum temperatures are about 3 °C lower. Winter minimum temperatures average 22 °C (72 °F). The annual pattern of temperature fluctuation for Picard compares most closely with the Comoro Islands. Summer maxima are identical with Diégo Suarez values; winter minima with the Seychelles. The highest and lowest shade temperatures recorded in the year were 36.3 °C (97.4 °F) and 19.5 °C (67.1 °F). The diurnal temperature range varies little throughout the year, averaging 6.5 °C, though extremes of 11 °C are occasionally recorded. Lagoon water temperatures are tidally controlled. At springs mean values may exceed the local air shade temperature by more than 3 °C. This could lead to very high temperatures in the lagoon in summer, but the exact magnitude must be ascertained from future observations. Sunshine measurements have not yet been made on the atoll. Calculations of probable monthly sunshine totals based on cloud observations show that October is clearly the sunniest month with a computed average of 8.6 h/day; January and April are least sunny, with 5.4 h/day. The annual total calculated for Aldabra (2400 h average; 2100 h 1967/8) is considerably at variance with regional values shown on world maps of climatology (indicating 1800 h). This can be resolved only by obtaining instrumental records from the island. The mean annual rainfall of 670 mm (26.5 in) derived from 7 years records is strikingly lower than atlas predictions. It places Aldabra in the most arid sector of the western Indian Ocean. From 1950 to 1960 a sequence of pairs of wet and dry years can be discerned, with extreme yearly totals of 1200 and 350 mm (47 and 14 in). The monsoon may occasionally be as short as 2 months, and droughts of 3 months or more are recorded during the trades. In 1967/8 summer rainfall showed a continental-type bimodal distribution, though on average it shows a broad plateau tending towards a late summer maximum (cf. Lindi, Tanzania). In 1967/8, 42% of the yearly rainfall fell on 5 days as violent showers with more than 40 mm (1.6 in). Local climatic effects were investigated from an auxiliary meteorological station set up at Middle Camp, Passe Houareau. In October 1968 the mean trade-wind speed exceeded 9 m s -1 (19 knots) from 08h00 to 13h00; which indicates a tendency to underestimate its strength considerably when observing at Settlement. Appreciable east—west variation in rainfall totals occurred. It is this essential to evaluate any precipitation gradient which may exist during the monsoon, for rainfall totals from Picard may bear little relation to the southeastern region. Analysis of autographic charts indicates that relative humidity varies from stable night values of around 93% to minima of 70% during early afternoon. In late September/October, values as low as 50% have been recorded. A strongly semi-diurnal distribution of rainfall is shown by Dines tilting syphon raingauge charts, which correlates with the S 2 atmospheric tide. During the monsoon frequency of rain shows a pre-dawn maximum: during the trades a pre-dusk maximum, which is not typical of a truly oceanic atoll.

Orographic Precipitation in the Tropics: The Dominica Experiment

2012 ◽  
Vol 93 (10) ◽  
pp. 1567-1579 ◽  
Author(s):  
Ronald B. Smith ◽  
Justin R. Minder ◽  
Alison D. Nugent ◽  
Trude Storelvmo ◽  
Daniel J. Kirshbaum ◽  
...  
Keyword(s):  
Forced Convection ◽  
Droplet Diameter ◽  
Cloud Droplet ◽  
Heavy Rain ◽  
Trade Wind ◽  
Orographic Precipitation ◽  
Trade Winds ◽  
The Mean ◽  
The Tropics ◽  
Neutrally Buoyant

The Dominica Experiment (DOMEX) took place in the eastern Caribbean from 4 April to 10 May 2011 with 21 research flights of the Wyoming King Air and several other observing systems. The goal was an improved understanding of the physics of convective orographic precipitation in the tropics. Two types of convection were found. During a period of weak trade winds, diurnal thermal convection was seen over Dominica. This convection caused little precipitation but carried aloft air with island-derived aerosol and depleted CO2. During periods of strong trades, mechanically forced convection over the windward slopes brought heavy rain to the high terrain. This convection was “seeded” by trade-wind cumuli or neutrally buoyant cool wet patches of air. In this mechanically forced convection, air parcels did not touch the island surface to gain buoyancy so no island-derived tracers were lofted. With fewer aerosols, the mean cloud droplet diameter increased from 15 to 25 μm. Plunging airflow and a wake were found in the lee of Dominica. The DOMEX dataset will advance our understanding and test our theories of cumulus triggering and aerosol influence on precipitation.

6. Weather in the tropics

2017 ◽  
Author(s):  
Storm Dunlop
Keyword(s):  
Winter Season ◽  
Walker Circulation ◽  
Intertropical Convergence Zone ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Trade Winds ◽  
Northern Summer ◽  
The Indian Ocean ◽  
Convergence Zones ◽  
The Tropics

‘Weather in the tropics’ considers the weather systems between the two subtropical anticyclones, lying at approximately latitudes 30 °N and S. The trade winds consist of air that flows out of the subtropical anticyclones towards the equatorial trough. They are strongest in the winter season, tending to weaken during the summer. The northern and southern hemisphere trade winds converge at the Intertropical Convergence Zone, whose position is variable. The South Pacific Convergence Zone is closely associated with the changes involved in the Walker Circulation and El Niño events. The convergence zones over the Indian Ocean show major changes in location during the northern summer, and these are related to seasonal monsoons.

2. The circulation of the atmosphere

2017 ◽  
Author(s):  
Storm Dunlop
Keyword(s):  
Intertropical Convergence Zone ◽  
Hadley Cell ◽  
Convergence Zone ◽  
Coriolis Effect ◽  
Pressure Gradients ◽  
Trade Winds ◽  
Polar Cell ◽  
The Earth ◽  
Specific Temperature ◽  
Temperature And Pressure

‘The circulation of the atmosphere’ outlines the general model of the movement of air around the Earth. There are three circulation cells either side of the equator: the Hadley cell (nearest to the equator) and the polar cell, driven by specific temperature and pressure gradients, and the Ferrel cell between them. It describes global pressure patterns and the Coriolis effect, which results in south-westerly trade winds in the northern hemisphere and north-westerly trade winds in the southern. Also described are the Intertropical Convergence Zone, the polar easterlies, the westerlies, and how air moves around high- and low-pressure regions. The action of the surface winds also produces the various ocean currents.

THE EFFECT OF ALTERATION OF THYROXINE BINDING CAPACITY ON THE DIALYZABLE AND ABSOLUTE FRACTIONS OF TRIIODOTHYRONINE IN CIRCULATION

1973 ◽  
Vol 72 (2) ◽  
pp. 265-271 ◽  
Author(s):  
J. H. Dussault ◽  
D. A. Fisher ◽  
J. T. Nicoloff ◽  
V. V. Row ◽  
R. Volpe
Keyword(s):  
Correlation Coefficient ◽  
Inverse Relationship ◽  
Binding Capacity ◽  
Hormone Concentration ◽  
Thyroxine Binding Globulin ◽  
Serum Thyroxine ◽  
A Value ◽  
The Mean ◽  
Male Subjects ◽  
Female Subjects

ABSTRACT In order to determine the effect of alterations in binding capacity of thyroxine binding globulin (TBG) on triiodothyronine (T3) metabolism, studies were conducted in 10 patients with idiopathically low (7 subjects) or elevated (3 subjects) TBG levels and 10 subjects given norethandrolone (7 male subjects) or oestrogen (3 female subjects). Measurements of serum thyroxine (T4) concentration, maximal T4 binding capacity, serum T3 concentration and per cent dialyzable T3 were conducted. Serum T3 was measured both by chemical and radioimmunoassay methods. In patients with idiopathically low TBG, the mean serum T4 concentration was low (2.4 μg/100 ml), the mean serum T3 level low (55 ng/100 ml), the mean per cent dialyzable T3 increased (0.52%), and the calculated free T3 concentration normal (186 pg/100 ml). In patients with idiopathically high TBG levels the mean T4 concentration was high (10.3 μg/100 ml), the mean T3 level slightly elevated (127 ng/100 ml), the% dialyzable T3 low (0.10%) and the calculated free T3 concentration low normal (123 pg/100 ml). The correlation coefficient between the per cent dialyzable T3 and maximal TBG binding capacity in the 20 subjects was 0.68, a value significant at the P < 0.01 level. Thus, alterations in binding capacity of TBG seem to influence T3 and T4 metabolism similarly; the inverse relationship between the % of dialyzable hormone and total hormone concentration tends to keep the absolue levels of free hormones stable.

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