Rain Spells Research Articles

A look at driving rain spells at three cities in Great Britain

In this article, driving rain spell amounts are calculated from hourly wind and rainfall data for three cities in Great Britain, and comparisons are made with average annual driving rain values, also from hourly wind and rainfall data. The results show that the maximum observed driving rain spell intensities versus wall angles are qualitatively similar to angular distributions of annual driving rain both at and between the stations. For driving rain spell intensity expressed as the average number of exceedances of a threshold spell intensity value versus wall angle, results are both qualitatively and quantitatively very similar to angular distributions of annual driving rain. This suggests that average annual driving rain might be useful as a proxy measure of spell driving rain intensity in situations where relative risk of repeated penetration of masonry walls in building facades is of interest but quantitative spell data are not available.

An analytical study of rainfall pattern over Chennai

The spells of daily rainfall received at Nungambakkam and Meenambakkam observatories located in Chennai for ten year period have been analysed. The study reveals that the spells have three distinct patterns with February and March having negligible spells while April to September being 15 to 20 percent and from October to January having very high values. The spells that occur during southwest monsoon season are having high consistency of occurrence during evening, night and early morning where as the spells during northeast monsoon are equally spread during the whole day. Frequency of one or two spells per day is more during the months January to September. There is significant increase in the value of two spells and more during October to December. In the months of June to September more than 65 percent of the rainy days, the duration of rainfall in a day is less than 2 hours while October to December the value of percentage is below fifty. The number of spells of rainfall with amount of rainfall less than two millimeters is about 55 percent throughout the year. The intensity of spells of rain of less than 7 millimeters per hour ranges from 60 to 70 percent for all the months except for the month of March.

Time evolution of rain drop spectra over Cuddalore in coastal Tamilnadu

A disdrometer has been installed at Meteorological Office, Cuddalore in Coastal Tamilnadu during first week of April 2002. This paper attempts to describe an overview of the technicalities and facilities available in this disdrometer besides describing the results of the rain drop size distribution(DSD) from May to August 2002 covering parts of pre-monsoon (March – May) and southwest monsoon (June – September) season. The rain accumulation as measured by the disdrometer matches perfectly with the surface rain gauge measured amount for the rain rate upto 66 mm/hr. The contrasting features of rain spells over Cuddalore, a coastal station in southern peninsular India are clearly brought out in terms of DSDs albeit the rain amount during these period in the year 2002 was very subdued. The modal rain rate was less than 6 mm/hr (84% frequency) followed by 10-40 mm/hr (11%). The concentration of drops, specifically the concentration of larger drops, per rain spell is higher during June - August than during May. The modal class of drop size has an average diameter of 1.116 and 1.912 mm. Both exponential and log-normal distribution seem to be fitting well with the DSD. The rain rate derived from the moment 3.67 (m3.67) of the moment generating function (MGF) of the lognormal distribution function agrees reasonably well with the disdrometer measured rain rate for both the seasons considered. The variability of rain rate, in one minute interval, clearly reveals how the radar derived rainfall accumulation may go wrong even presuming that one uses a perfect Z – R relationship. This suggests the need for understanding the DSD and the micro-physical processes that cause the variability of concentration of drops more precisely to estimate the rain rate and warns about the need for very frequent low elevation radar scans for estimating the rain accumulation.

Analysis of beginning, end, and length of the rainy season along a Mediterranean–arid climate transect for geomorphic purposes

Geomorphic processes are controlled by rainfall, particularly in Mediterranean semi-arid and the arid regions. From a geomorphological aspect the characteristics of rainstorms and dry spells in these regions should be analysed as they might explain these processes. As a part of such analysis the beginning, end, and length of the rainy season should be determined. Eleven stations along a climatic transect extending from Judean Mountains with a Mediterranean climate to the Dead Sea arid region in Israel were studied. The beginning, end, and length of the rainy season, based on rainfall data for 30 years, are presented for daily rainfall and for accumulated rainfall within a rain spell (ARWS), and for different thresholds that might be used for different geomorphic processes. The results show that: (1) a close linear relationship exists between the beginning and end dates, as well as the rainy season's length, and the various rainfall thresholds; (2) as rainfall threshold increases the rainy season begins later, ends earlier, and consequently it is shorter in length; (3) likewise, as aridity increases the rainy season begins later, ends earlier, and it is shorter in length; and (4) the differences increase as the threshold increases. The regression line slopes emphasized a distinction between the two climatic regions, the Mediterranean and the arid region.

From individual behaviour to population pattern: weather-dependent foraging and breeding performance in black kites

The links between weather and animal behaviour in population processes have received relatively little attention. I studied the effect of weather conditions on foraging and breeding performance of a medium-sized raptor, the black kite, Milvus migrans. The frequency of prey capture attempts and their likelihood of success increased with temperature and declined with rainfall. Kites used flight styles involving a higher energy expenditure in less favourable weather. Nestling provisioning rates declined during rain spells. More kites hunted during periods of favourable weather and after periods with a high frequency of successful prey capture attempts by conspecifics; this result suggested that individuals may fine-tune their foraging effort to the expected foraging reward. Such compensatory behavioural adjustments may increase species resilience to climate change. The behaviourally mediated effects of weather on prey availability translated into population effects. Yearly weather conditions during the last stage of the prelaying period affected population-level productivity, probably through an effect on female body condition mediated by male provisioning capability and hunting yield. The predicted effects of climate change on kites may already be occurring, with progressively earlier laying and northward range expansion. These results confirm the need to pay greater attention to behaviourally mediated effects of climate on populations, particularly when individuals make compensatory adjustments that may enhance resilience to climate change. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Ecology of Cichla monoculus (Osteichthyes: Cichlidae) from a reservoir in the semi-arid region of Brazil

The ecology of the freshwater fish Cichla monoculus Spix et Agassiz, 1831 (Osteichthyes: Cichlidae) was investigated in the Campo Grande Reservoir, Northeast Brazil. Rainfall, temperature, pH, dissolved oxygen and electrical conductivity of the water were recorded monthly. Fish collected on a monthly basis were measured, weighed, dissected, sexed and the stages of maturation of the gonads were assessed by macro and microscopic means. The semi-arid study region had short spells of rain interspaced with dry seasons. A positive correlation was observed between rainfall and air and water temperatures and electrical conductivity of the water. The study population had an extended spawning season, with peak of reproductive activity coinciding with low water temperatures. Males were longer and heavier than females on an average and were larger at onset of sexual maturity. The size frequency distributions of the oocytes indicate that C. monoculus is a multiple spawner with an estimated batch fecundity of 3100. Condition factor showed an inverse relationship with gonad size during maturation in both sexes and spent fish were in poor condition. In mature males, lipid stores in the post-occipital cephalic protuberance, a secondary sexual characteristic developed during the reproductive phase, were depleted in spent individuals. The success of this fish is attributed to its reproductive capacity and to the phenotypic plasticity that allows it to adapt to the harsh ecological conditions that prevail in the semi-arid region of Northeast Brazil.

Reproductive ecology of a neotropical cichlid fish, Cichla monoculus (Osteichthyes: Cichlidae).

The reproductive ecology of the freshwater fish Cichla monoculus Spix, 1831 (Osteichthyes: Cichlidae) was investigated in the Campo Grande Reservoir, Northeast Brazil. Rainfall, temperature, pH, dissolved oxygen and electrical conductivity of the water were recorded monthly. Fish collected on a monthly basis were measured, weighted, dissected, sexed and the stage of maturation of the gonads were assessed by macro and microscopic means. The semi-arid study region has short spells of rain of 2-3 months duration interspersed with dry seasons. A positive correlation was observed between rainfall and air and water temperatures and conductivity of the water. The study population had an extended spawning season, with peak reproductive activity coinciding with low water temperatures. Males were longer and heavier than females on average and were larger at onset of sexual maturity. The size frequency distributions of the oocytes indicate that C. monoculus is a multiple spawner with an estimated batch fecundity of 3100. Condition factor showed an inverse relationship in relation to gonad size during maturation in both sexes and spent fish were in poor condition. In mature males, lipid stores in the post-occipital cephalic protuberance, a secondary sexual characteristic developed during the reproductive phase, which depleted in spent individuals. The success of this fish is attributed to its reproductive capacity and to the phenotypic plasticity that allows it to adapt to the harsh ecological conditions that prevail in the semi-arid region of Northeast Brazil.

Distribution of stable isotopes in arid storms

Temporal distributions of the isotopic composition in arid rain storms and in the associated runoff were investigated in a small arid rocky basin in Israel. Customized rain and runoff samplers provided sequential water samples hermetically sealed in high-density PVC bags. In several storms where the runoff was isotopically depleted, compared with the rainfall, the difference could not be explained by fractionation effects occurring during overland flow. A water-balance study relating the runoff discharge to rainfall over a rocky watershed showed that the entire discharge is produced by a very small segment (1–2 mm) of the rain storm. The major objective, therefore, was to provide quantitative relations between segments of rainfall (rain showers and rain spells) and runoff. The time distribution of the composition of stable isotopes (oxygen and hydrogen) was used to quantify the correlation between the rain spell's amount and the consequent runoff. The aim of this work was to (a) utilize the dynamic variations in the isotopic composition in rainfall and runoff and model the magnitude of surface-storage capacity associated with runoff processes of overland flow, and (b) characterize the isotopic composition of the percolating water with respect to the isotopic distribution in rainfall and runoff events. The conceptual model postulates an isotopic mixing of overland flow with water within the depression storage. A transport model was then formulated in order to estimate the physical watershed parameters that control the development of overland flow from a certain rainfall period. Part I (this paper) presents the results and the assessment of the relative depression storage obtained from oxygen-18 and deuterium analyses that lead to the physical and mathematical formulation of a double-component model of kinematic-wave flow and transport, which is presented in Part II (accompanying paper).

Aster kantoensis Kitam., an endangered flood plain endemic plant in Japan: Its ability to form persistent soil seed banks

We examined dormancy/germination traits of the seeds of Aster kantoensis, an endangered local endemic on the gravelly flood plains of a few eastern central Japanese rivers, to assess its ability to form persistent soil seed banks in its natural habitats. Immediately after the seed collection from the largest remaining population of the River Tama in early winter, the seeds showed a low level of relative dormancy, which disappeared within a month under the prevailing conditions in the natural habitat. After a few months' dry chilling storage, the seeds became germinable over a wide temperature range, i.e. 6–36°C. The seeds showed neither requirement for temperature fluctuation nor sensitivity to leaf canopy light. The thermal time required for 50% germination at temperatures below 30°C was less than 70 Kd (Kelvin days calculated with a base temperature of 5°C). Since such requirements for germination of seeds naturally dispersed and overwintered will be satisfied by a spell of spring rain, we cannot expect the formation of persistent soil seed banks. Correspondingly, after spring germination, no or negligible firm intact seeds could be detected in the surface soils sampled. Safe-sites for the recruitment of the species are known to be new areas created by fluvial disturbance, which may occur sporadically in space and time. Without persistent soil seed banks, successful dispersal of the seeds to these safe-sites is of crucial importance for the persistence of the metapopulation composed of ephemeral subpopulations. Recent decrease in the colonization rate of new subpopulations due to diminishing seed sources might accelerate the decline of the metapopulation. To break the extinction vortex in which the species has been involved, we propose human-aided seed dispersal to safe-sites in order to strengthen the conservation of this threatened species.

Intraseasonal wind anomalies related to wet and dry spells during the ?long? and ?short? rainy seasons in Kenya

The largest part of Kenya exhibits two major rainy seasons, the March–May «long rains» and the October–December «short rains», both related to the passage of the ITCZ, but differing in the amount of rainfall recorded and its interannual variability. In order to investigate whether these differences also apply at intraseasonal time-scales, daily rainfall data for the peak month of each rainy season (April and November) were collected for 7 consecutive years (1982–1988). The network comprises 68 stations, from which a classification of the spatial patterns of daily rainfall anomalies has been performed. Wind anomalies corresponding to the various rainfall types and to specific regional rainfall departures were determined using four pilot balloon stations and one radiosonde station. They revealed that there exist significant differences between upper-air circulation anomalies exhibited in the «long» and «short» rainy seasons, especially as far as rain spells in the Eastern Highlands are concerned. In that region, easterly anomalies in the «short rains» period are associated with an increase in rainfall. During the «long rains», enhanced easterlies more generally coincide with an overall drop of convection in the country. In Western Kenya, wet conditions are more systematically associated to westerly wind anomalies.

Compounding in Qafar

The language described in this chapter is spoken by at least three million people who call themselves Qafar, though earlier European writers and travelers usually referred to them as Danakil. The Qafar inhabit that vast tract of land which stretches from the Red Sea coast south and west as far as the scarplands of the Ethiopian Plateau, an area generally referred to as the Danakil Depression. With the exception of narrow belts of luxuriant jungle along the banks of rivers, such as the Awash and the Mille, which descend into the Depression, the country is largely desert; though even quite short spells of rain can bring grass and other transient plant life back into some parts. Although Qafar living in large coastal towns such as Djibouti and Assab and those on the Red Sea coast who live by fishing have clearly abandoned past oralism as a way of life, the majority of Qafar remain pastoralists, and pastoralism is strongly reflected in the lexicon of their language.

Analysis of severe rainstorms over gujarat and punjab during the 1993 monsoon

Severe rain spells, which occurred in 1993 monsoon season over the Indian region, were examined for hydrometeorological analysis. It was seen that during 9–12 July, heavy to very heavy rainfall was reported by many stations in the north-west Indian region of Gujarat, Punjab, and Haryana. This heavy rainspell gave two separate rainstorm patterns: one over the Gujarat region, and other over the Punjab and Haryana region. Both these rainstorms have been analysed by the depth-area-duration technique. The areal rainfall data obtained from the analysis have been compared with similar data of past severe rainstorms of the respective region. The analysis has shown that the 9–12 July 1993 rainstorm, although not as severe as past rainstorms, yielded areal rain depths of 12·4, 23·2, and 28·4 cm in 1, 2, and 3 days in Gujarat and 13·4, 19·8, and 30·3 cm over Punjab and Haryana, respectively, over an area of 50 000 km2.

Intraseasonal variations of June?September rainfall and upper-air circulation over Kenya

In the Northern Summer, Kenya is located under the influence of the divergent Indian monsoon flow, and therefore is dry except for two separate areas: the coastal strip and the western regions. Analysis of daily rainfall data for June–September 1982 to 1988 has revealed that, although there are many distinct rainfall events between the two regions, an out-of-phase relationship is also evident, rain on the Coast being frequently accompanied by a drop in the precipitation over the Rift Valley area. It is shown that two types of wind forcing accompany these patterns. Alternating westerly and easterly anomalies at the 700 hPa level are associated with persistent wet and dry conditions (respectively) in western Kenya, and the opposite along the Coast. Large speed increases of the cross-equatorial low-level jet over Mombasa are followed by short rain spells in this latter region. These observations are thought to reflect the importance of an influx of moist unstable air from the west, linked to the West African monsoon, to ensure heavy rainfall over the Highlands. Variations in the low-level jet speed, which cannot be easily followed downstream, also have a significant, but less persistent impact on rainfall in the two regions.

Electrical, microphysical and dynamical observations in summer monsoon clouds

Electrical, microphysical and dynamical conditions in ground-based clouds were studied using the observations carried out at Mahabaleshwar (17°56′N, 73°40′E; 1382 m ASL), a hill station, during the summer monsoon season of 1977. There is a significant correlation between the rain intensity and the corresponding atmospheric electric potential gradient. The diurnal curves of rainfall and negative electric potential gradient exhibited two peaks. The peak in rainfall during the morning hours and the afternoon peak in electric potential gradient were statistically significant. The early morning peak in rainfall was attributed to the enhanced convergence caused by the radiational imbalance in the cloud and cloud-free regions during active monsoon conditions. The afternoon peak in the electric potential gradient was attributed to the cloud formation due to convection. The atmospheric electric potential gradient showed sign reversal from its normal fair weather positive to negative at the time of the onset of rain. The reversal of the electrical potential gradient and the incidence of positively charged raindrops at the surface were almost simultaneous. Positive raindrop charges were recorded 1–2 minutes prior to the occurrence of negative electric potential gradient showing a steep increase during heavy rain spells. The raindrop charges were predominantly positive. The possible physical mechanisms for electrification of monsoon clouds have been discussed. The cloud condensation nuclei and surface temperature also showed peaks during the morning hours. The microphysical observations suggest that the rain formation takes place in monsoon clouds both by the collision-coalescence and ice crystal processes. A simple 1-D model was used to compute different cloud physical parameters. For a cloud with its top at 9 km the precipitation efficiency is in the range 60–70% of the adiabatic liquid water content. It has an average rainfall rate of 15 mm hr −1, vertical velocity of 3–5 m s −1 and average life time of 30 minutes.

MOBILITY AND DISSIPATION OF METALAXYL IN TOBACCO SOILS

Soil thin layer chromatography studies showed that metalaxyl (methyl-N-(2,6-dimethylphenyl)-N-(2-methoxyacetyl)alaninate) was similar to 2,4-D and more mobile than pyrazone > permethrin. Soil column studies indicated that approximately 0, 9, 73 and 83% of the applied fungicide leached through a 25-cm soil column after being subjected to 5, 10, 15 and 20 cm of simulated rainfall, respectively. A study on the effects of sequential periods of rain and dry spells on movement of metalaxyl showed that the fungicide was leached with each 5 cm simulated rainfall but moved upward during the dry cycle. There was no leachate from soil columns that received four increments of 5 cm of simulated rainfall alternated with a 48-h drying cycle. However, approximately 32% of the applied metalaxyl was leached through soil columns that received similar rainfall treatment alternated with a 24-h drying cycle. Field plot studies indicated that most of the soil-incorporated metalaxyl remained in the upper 0–30 cm, with approximately 10% being leached into the 30- to 45-cm zone. The half-life of metalaxyl in soil from field plots and six growers’ farms ranged from 3 to 5 wk. Metalaxyl acid, a possible metabolite, was not detected in any of the soil samples. Metalaxyl and its acid were not detected in either the water or sediment of Big Creek which drains the tobacco region.Key words: Metalaxyl, mobility, persistence, environmental contamination

Study of frequency of wet and dry spells over Nasik district

Frequencies of wet and dry spells at eight stations Dindori, Peillt, Chandor Yeola Kalwan,. Sinnar, Satana and Nasik in Nasik district for the southwest monsoon period are 'studied. The study is based on the daily rainfall data of the stations for 50 years from 1921 to 1970. It is seen that the frequencies of rain spells of less than five days are common and high for all stations and there is a general decrease in the frequencies for spells more than five days. The same analogy is noticed in dry spells also. The effect of persistence, the number of runs of different durations expected only on chance are a.1so worked out for both wet and dry spells for all the stations. The effect of orography on the frequencies is very well reflected, lower wet spells being more on the windward side facilities to of the hills and higher dry spells in the rain shadow region.

Space-Age Europe: Gaullism, Euro-Gaullism, and the American Dilemma

It is a far cry from Cape Kennedy, wrote a correspondent for the New York Times. are no neon signs, no drive-ins-and no night clubs. There are only some scattered huts and towers, lost in a desolate flatland as big as New Jersey, its pebbly floor covered with a pale green haze after a spell of rain. In the huts, which are filled with electronic equipment, one can hear, almost any morning, a calm young voice on a loudspeaker saying 'dix, neuf, huit, sept ...' In the distance a needle with a tail of fire slowly rises above the desert and roars into the sky.' The site was Hammaguir, an adobe village where sheep, goats, and a few dromedaries nosed about in the brittle weeds. Colomb-Bechar, the nearest town, lay 80 miles to the north, itself 700 miles into the Sahara from Algiers. Nearby, the parallel lines of an abandoned railroad vanished into the dunes, perhaps to meet at infinity, an artifact of France's first stab at a colonial dream, the trans-Saharan railway. In 1965, the imperative of international competition had brought France's finest engineers back into a desolation that proved congenial to the most advanced technology even as it swallowed the remains of an earlier industrial revolution. For the Algerian civil war prepared the return of Charles de Gaulle, who forestalled a military threat to overthrow the Fourth Republic by overthrowing it himself and pledged to

1982年12月13日～25日にマレーシア半島東岸とシンガポールに発生した豪雨の解析

The meridional wind compnents and the vertical p-velocities over the east coast of Peninsular Malaysia and Singapore were computed for the period of the heavy rain spells from 13th to 25th December 1982. The relationship between the heavy rain spells and the Hadley cell was investigated. The following significant features are noted : (1) The formation of the heavy rain spells over the east coast of Peninsular Malaysia and Singapore are mainly caused by strong upward motions of moist air in the southern branch of the Hadley cell. (2) The maximum upward velocities in mid-troposphere are caused by the combination of strong low-level convergence and the initial appearance of the equatorial cell in the southern branch of the Hadley cell.

Calibration d'un radar météorologique pour la mesure des précipitations. Premiers résultats en région parisienne

The object of this study is to examine all the possibilities of quantitative precipitation estimation by use of a meteorological radar. We have based our researches on reflectivity data from the Dammartin-en-Goelle radar (10 cm) and measurements of precipitation intensity from rain-gauge recordings and rain-gauges in the Paris area. Hourly comparisons taken at random (53 stations) between radar hyetographs and rain-gauges recordings have made it possible to highlight several problems encountered in radar measurement (the importance of the Z-R (Marshall-Palmer) relationship, ground echoes, masking effects, distance effects on the radar, uniform calibration procedures) and to derive criteria concerning the choice of a minimum, representative calibration network. We have also conducted initial tests to validate random radar measurement (with uniform, regionalised calibration by a sub-network (64 stations)) with three days' uninterrupted operation of the radar and a dense network of rain-gauges (270). Reconstructed situations effected at points not used for calibration purposes were compared with the actual rain-gauge recordings. For these three days' only the regionalised calibration technique gave results equivalent to those from a conventional (Spline) interpolation method using the calibration sub-network only. Only systematisation of the calibration and validation procedures described to other rain spells and for a more extensive network of recording rain-gauges can lead to definite conclusions. Special estimations of rainfall are also required and here a correctly calibrated radar should be more effective.

Computing a Probability Distribution for the Start of the Rains from a Markov Chain Model for Precipitation

The start of the rains is defined to be the first day, or two-day rain spell, in which greater than a specified total amount of rain occurs. A method of calculating the probability distribution of the start of the rains from a Markov chain model of the daily precipitation is given. The application of this method is illustrated with data from Samaru, Nigeria.