Number Of Rain Days Research Articles

A multiscale information theory approach to assess spatial–temporal variability of daily precipitation

Summary Information theory metrics are applied to ascertain the spatial and temporal variability of daily precipitation over the continental United States. Entropy is computed of the daily precipitation records and of the precipitation event size distribution. In addition, relative entropy is also computed between the two records and the Hurst exponent is calculated for comparison purposes. These values show little correlation with mean annual precipitation, number of rain days or station elevation. However, there is a clear spatial pattern in the precipitation and relative entropy fields corresponding to a breakpoint at approximately −95° longitude, which the Hurst exponent is not capable of resolving. Using wavelet multiresolution analysis and relative entropy, this breakpoint is shown to correspond to higher temporal variability (sub-monthly) in the western United States. In addition, scalewise mutual information content illustrates the general feature of three distinct scaling regions for precipitation: (1) synoptic (2–10 days), (2) monthly to annual times and (3) interannual variability. This analysis demonstrates the usefulness of an information theory approach to assessing the dynamics of precipitation.

Hydrological modeling of River Xiangxi using SWAT2005: A comparison of model parameterizations using station and gridded meteorological observations

Gridded climate data sets are widely used in the analysis, modeling and forecasting of the consequences of climate change. The objective of this study is to compare the impact of different climate datasets (station vs. gridded) on the parameterization of a hydrological model (developed using SWAT2005) of the River Xiangxi, the largest tributary of Yangtze River in the Hubei part of the Three Gorges Reservoir. Climate data used in this study derive from two sources: point daily observations from the Xingshan meteorological station (STN) and gridded (0.5° × 0.5°) monthly observations of the CRU TS3.0 global dataset (CRU) downscaled to daily data using a weather generator. Data from 1970 to 1974 were applied for sensitivity analyses and autocalibration and subsequently validate hindcasts over the period 1976–1986. Despite there being only slight differences in mean annual precipitation (1003 mm vs. 1052 mm) between STN and CRU, the data differ more in their estimates of the number of rain days (136 vs. 112) and wet days standard deviation (11.75 mm vs. 18.49 mm). The mean, maximum and minimum temperatures from CRU are all lower than those from STN. SWAT parameter sensitivity analysis results show slight differences in the relative rank of the most sensitive parameters, with the differences mainly caused by the lower temperature and more intensive rainfall in CRU relative to STN. Autocalibrated parameters showed very similar values, except for the surface runoff lag coefficient which is higher for the CRU dataset compared to that derived from the STN dataset. Statistic results for discharge simulated based on CRU compared rather well with that based on STN CRU as evaluated using the standard statistics of the Nash–Sutcliffe efficiency, coefficient of determination, and percent error. The sensitivity analysis and autocalibration tool embedded in SWAT2005 is a powerful utility in hydrological modeling of the River Xiangxi, and the CRU dataset appears to be appropriate for application to hydrological modeling in this case, thus providing a good basis for climate change studies.

Seasonal And Long Term Rainfall Trends In Calabar, Nigeria

Rain fall trends all over the world with the attendant socio-economic effects have taken unprecedented dimensions in recent times. Trend studies of this atmospheric parameter will enable us examine the nature of variationand possible causative agents. Both seasonal and long term trends of rain fall in Calabar between 1985 and 2003 have been examined. Monthly and annual rainfall totals, number of rain days and extreme rain fall indices were determined as secondary data and used for the analyses. SPSS statistical package was used to deseasolnalise the data and determine its trend. Both raw data and deseasonalised data were used to examine long term trends and both show some level of increase in rainfall of about 1.9mm and 300mm respectively. The results also show that rainfall has highly pronounced season. The seasonality of all the parameters namely total rainfall, total extreme rainfall, total number of rain days and number of extreme rain days were all similar, with a slight break in the month of August. This break introduces a week or more of drought which is essential for crop production, drying and storage of agricultural products and their by- products

Impact of Early Spring Weather Factors on the Risk of Tomato Spotted Wilt in Peanut.

Peanut growers in the southeastern United States have suffered significant economic losses due to spotted wilt caused by Tomato spotted wilt virus (TSWV). The virus is transmitted by western flower thrips, Frankliniella occidentalis, and tobacco thrips, F. fusca, and was first reported in the southeast in 1986. The severity of this disease is extremely variable in individual peanut fields, perhaps due to the sensitivity of the vector population to changing weather patterns. The objective of this study was to investigate the impact of early spring weather on spotted wilt risk in peanut. On-farm surveys of spotted wilt severity were conducted in Georgia peanut fields in 1998, 1999, 2002, 2004, and 2005. The percent spotted wilt intensity (%) for cv. Georgia Green was recorded and categorized into three intensity levels: low, moderate, and high. Meteorological data were obtained from the Georgia Automated Environmental Monitoring Network for the period between March 1 and April 30. Statistical analysis was conducted to identify weather variables that had significant impact on spotted wilt intensity. The results indicated a high probability of spotted wilt if the number of rain days during March was greater than or equal to 10 days and planting was before 11 May or after 5 June. The total evapotranspiration in April (>127 mm) and the average daily minimum temperature in March (>6.8°C) similarly increased the risk of spotted wilt. Knowing in advance the level of spotted wilt risk expected in a peanut field could assist growers with evaluating management options and significantly improve the impact of their decisions against spotted wilt risk in peanut.

Pheno-morphological and agronomic diversity among Scorpiurus muricatus (Fabaceae) natural populations collected in Sicily

SUMMARYPrickly scorpion's tail (Scorpiurus muricatus L.) is a self-reseeding annual legume widely distributed in natural pastures of the Mediterranean area and appreciated by farmers for its productivity, forage quality and palatability. Twenty-eight natural populations were collected throughout Sicily in 2005; two field experiments were carried out in 2005/06 in a hilly area of the Sicilian inland to assess the genetic variation based on pheno-morphological and agronomic characters. The pheno-morphological traits observed were analysed using a principal component analysis (PCA). The first four components of PCA (eigenvalues >1) explained 0·84 of the total variation. Similarities obtained by PCA were investigated by means of cluster analysis, which clearly identified five clusters.The pheno-morphological and agronomic traits were mainly affected by latitude of the collection site (0·69 of the correlations were significant), spring rainfall (0·63) and rain days per year (0·63). Altitude was not significantly correlated with any of the traits.A strong positive correlation was found between the days to the first flower and spring rainfall at the collection site. Populations originating from subhumid or dry-subhumid Mediterranean climate zones showed greater leaf dimensions when compared with those originating from semi-arid zones. Seed weight decreased with increasing number of rain days per year and spring rainfall. Populations from drier environments showed, on the whole, a more prostrate growth habit. Dry matter yield at spring cut exhibited a significant correlation with latitude (positive) and longitude (negative). Seed production was highly correlated with spring rainfall, number of rain days per year and latitude of collection site. The presence of a large diversity among populations appears to be valuable when searching for suitable S. muricatus material to exploit in pastures and crop–livestock farming systems of Mediterranean areas.

Analytical derivation of the Budyko curve based on rainfall characteristics and a simple evaporation model

The Budyko curve is often used to estimate the actual evaporation as a function of the aridity index in a catchment. Different empirical equations exist to describe this relationship; however, these equations have very limited physical background. The model concept presented in this paper is physically based and uses only measurable parameters. It makes use of two types of evaporation: interception and transpiration. It assumes that interception can be modeled as a threshold process on a daily time scale. If multiplied with the rainfall distribution function, integrated, and multiplied with the expected number of rain days per month, the monthly interception is obtained. In a similar way, the monthly interception can be upscaled to annual interception. Analogous to the interception process, transpiration can be modeled as a threshold process at a monthly time scale and can be upscaled by integration and multiplication with the expected number of rain months. The expected rain days per month are modeled in two ways: as a fixed proportion of the monthly rainfall and as a power function based on Markov properties of rainfall. The latter is solved numerically. It appears that on an annual basis the analytical model does not differ much from the numerical solution. Hence, the analytical model is used and applied on 10 locations in different climates. This paper shows that the empirical Budyko curve can be constructed on the basis of measurable parameters representing evaporation threshold values and the expected number of rain days and rain months and, in addition, a monthly moisture carryover amount for semiarid zones.

Components of rainy seasons’ variability in Equatorial East Africa: onset, cessation, rainfall frequency and intensity

The inter-annual and spatial variability of different rainfall variables is analysed over Equatorial East Africa (Kenya and northeastern Tanzania). At the station level, three variables are considered: the total precipitation amount (P), the number of rain days (NRD) and the daily rainfall intensity (INT). Using a network of 34 stations, inter-station correlations (1958–1987) are computed for each of these variables. The spatial coherence of monthly or seasonal P and NRD is always much higher than that of rainfall intensity. However, large variations in spatial coherence are found in the course of the seasonal cycle. Coherence is highest at the peak of the short rains (October–December) and low during the long rains (March–May), except at its beginning. The inter-annual variability of the onset and cessation of the rains is next considered, at the regional scale, and the study extended to 2001. In the long rains, the onset and cessation dates are independent of NRD and INT during the rainy season. Hence, the long rains seasonal rainfall total depends on a combination of virtually unrelated factors, which may account for the difficulty in its prediction. However, the onset, which exhibits a large inter-annual variability and a strong spatial coherence, has a prime role. Conversely, in the short rains, though the onset is again more decisive than the cessation, the different intra-seasonal descriptors of the rains are more strongly inter-related.

Historical analysis of the first rain event and the number of rain days in the western part of Palakkad gap, South India

This article was submitted without an abstract, please refer to the full-text PDF file.

Monthly fluctuations in radial growth of individual lobes of the lichenParmelia conspersa (Erhr. ex Ach.) Ach.

The radial growth (RG) of 120 lobes from 35 thalli of the foliose lichenParmelia conspersa (Ehrh. ex Ach.) Ach. was studied monthly over 22 months in south Gwynedd, Wales, UK. Autocorrelation analysis of each lobe identified three patterns of fluctuation: I) random fluctuations (58% of lobes), 2) a cyclic pattern of growth (23% of lobes), and 3) fluctuating growth interrupted by longer periods of very low or zero growth (19% of lobes). In 80% of thalli, two or three patterns of fluctuation were present within the same thallus. Growth fluctuations were correlated with climatic variables in 31% of lobes, most commonly with either total rainfall or number of rain days per month. Lobes correlated with climate were not associated with a particular type of growth fluctuation. RG of a lobe was positively correlated with the degree of bifurcation of the lobe tip. It is hypothesised that lobes ofP. conspersa exhibit a cyclic pattern of growth due in part to lobe division. The effects of climate, periods of zero growth, and microvariationsin the environment of a lobe are superimposed on this cyclic pattern resulting in the random growth of many lobes. Random growth fluctuations may contribute to the maintenance of thallus symmetry inP. conspersa.

Fumonisins in Maize in Relation to Climate, Planting Time and Hybrids in Two Agroecological Zones in Zambia

Field experiments in the high rainfall zone (HRZ) and the medium rainfall zone (MRZ) in Zambia were designed to determine the natural occurrence of fumonisins (FB(1-2)) in Zambian maize hybrids, accumulation of FB(1-2) resulting from artificial inoculation with Fusarium verticillioides and effects of climate and planting time on FB(1-2) in maize. Combined FB(1-2) concentrations varied from 0 to 13,050 ng/g, with an overall mean of 666 ng/g. Maize from the HRZ had low incidences of FB(1-2)-positive samples (mean 41%) which contained FB(1-2) below 500 ng/g. In the MRZ, higher incidences (mean 97%) and concentrations (40% of samples >1,000 ng/g) were recorded in two out of three years. There was no correlation between mean location FB(1-2) concentrations in individual years and precipitation, number of rain days or monthly precipitation. Postponing the planting time with 10 or 20 days did not significantly affect FB(1-2) concentration, but it reduced the yields in some years.

Do weak AR4 models bias projections of future climate changes over Australia?

Regional climate projections using climate models commonly use an “all-model” ensemble based on data sets such as the Intergovernmental Panel on Climate Change’s (IPCC) 4th Assessment (AR4). Some regional assessments have omitted models based on specific criteria. We use a criteria based on the capacity of climate models to simulate the observed probability density function calculated using daily data, model-by-model and region-by-region for each of the AR4 models over Australia. We demonstrate that by omitting those climate models with relatively weak skill in simulating the observed probability density functions of maximum and minimum temperature and precipitation, different regional projections are obtained. Differences include: larger increases in the mean maximum and mean minimum temperatures, but smaller increases in the annual maximum and minimum temperatures. There is little impact on mean precipitation but the better models simulate a larger increase in the annual rainfall event combined with a larger decrease in the number of rain days. The weaker models bias the amount of mean warming towards lower increases, bias annual maximum temperatures to excessive warming and bias precipitation such that the amount of the annual rainfall event is under-estimated. We suggest that omitting weak models from regional scale estimates of future climate change helps clarify the nature and scale of the projected impacts of global warming.

A Predictive Model for Spotted Wilt Epidemics in Peanut Based on Local Weather Conditions and the Tomato spotted wilt virus Risk Index

Tomato spotted wilt virus (TSWV), a member of the genus Tospovirus (family Bunyaviridae), is an important plant virus that causes severe damage to peanut (Arachis hypogaea) in the southeastern United States. Disease severity has been extremely variable in individual fields in Georgia, due to several factors including variability in weather patterns. A TSWV risk index has been developed by the University of Georgia to aid peanut growers with the assessment and avoidance of high risk situations. This study was conducted to examine the relationship between weather parameters and spotted wilt severity in peanut, and to develop a predictive model that integrates localized weather information into the risk index. On-farm survey data collected during 1999, 2002, 2004, and 2005 growing seasons, and derived weather variables during the same years were analyzed using nonlinear and multiple regression analyses. Meteorological data were obtained from the Georgia Automated Environmental Monitoring Network. The best model explained 61% of the variation in spotted wilt severity (square root transformed) as a function of the interactions between the TSWV risk index, the average daily temperature in April (TavA), the average daily minimum temperature between March and April (TminMA), the accumulated rainfall in March (RainfallM), the accumulated rainfall in April (RainfallA), the number of rain days in April (RainDayA), evapotranspiration in April (EVTA), and the number of days from 1 January to the planting date (JulianDay). Integrating this weather-based model with the TSWV risk index may help peanut growers more effectively manage tomato spotted wilt disease.

Knowledge gaps in bryophyte distribution and prediction of species-richness

Knowledge of the distribution of species is fundamental to their conservation. Hence, it is important to understand the completeness of distribution inventories and the location of the main gaps. In an attempt to do this within an area of north-west England, this study builds a model which predicts bryophyte species-richness in 1220 tetrads (2 × 2 km squares) based upon their environmental characteristics, then compares predictions with current knowledge. The number of raindays (≥1 mm rain) each year was clearly the most important predictor of species-richness, followed by total nitrogen deposition and percentage cover of broad-leaved woodland. The main gaps in the current inventories are located and an assessment is made of their overall completeness. Suggestions for improvements in predicting bryophyte species-richness at tetrad resolution are provided.

Trends in timing of migration of south-western Australian birds and their relationship to climate

The influence of climate on the timing of migration of Australian birds is poorly understood, particularly in Western Australia and for waterfowl. This paper examines a new dataset, comprising presence—absence records of 20 species of waterbirds and landbirds at Middlesex, south-western Australia, for the period 1973–2000. Considering only species with sufficient records to determine trends, over this period nine of 19 species (47%) had significantly altered arrival times (five arriving earlier and four later); seven of 17 species (41%) had significant changes in departure dates (four departing later, three earlier); and eight of 17 (47%) species had significantly different season lengths (the period spent at Middlesex, with five spending more time at Middlesex). Generally, changes in the timing of regular seasonal movements were consistent among species that arrived or departed in similar seasons, with species that arrive in spring tending to arrive earlier, while species arriving in autumn and winter arrived later. Trends were generally more pronounced in spring-arriving species, though strong trends were also seen in other seasons. This region experienced significant reductions in the number of rain-days and increased minimum temperature over the study period. For many Middlesex species, particularly waterbirds, precipitation changes appeared to have a greater influence on changes in migration timing than temperature, though some species also appeared to respond to changes in extreme temperatures. This differs from many northern hemisphere studies, where changes in mean, maximum, or minimum temperature were associated with changes in migration timing.

Variability in the Italian population of Gnomonia leptostyla, homothallism and resistance of Juglans species to anthracnose

SummaryIsolations of Gnomonia leptostyla were carried out in 13 plantations of Juglans regia distributed throughout Italy, including Sardinia and Sicily. Mean diameter of colonies grown in vitro at 22°C and sporulation of 191 isolates, grouped by site of collection, were compared. Four groups of isolates, from environmentally diverse sites, were more thoroughly investigated for the effect of temperature (from 10 to 30°C, 5°C increment) on growth and sporulation. Colony growth of isolates within groups correlated with temperature and environmental parameters at the site of collection, such as temperature, rainfall, number of rain days per month and per year, and altitude. Altitude and mean temperature in April correlated with colony growth. In general, the isolates that grew significantly more slowly were from sites with colder early springs and higher altitudes. More significant data were obtained comparing isolates from different sites obtained from the same walnut cultivar or population. The host source was more significantly correlated with colony growth within the same site of collection. Acervular conidiomata were abundantly produced by all isolates at 22°C in darkness after 21 days, while protoperithecia were produced within 2 months by most isolates, under the same conditions. Similarly, the four groups of isolates tested at different temperatures produced conidiomata at 20 and 25°C, but not at 10, 15 and 30°C. After 2 months, protoperithecia were present in most isolates at 20°C, very few at 25 and 15°C, and no production was recorded at 10 and 30°C. Fertile perithecia with asci and ascospores were produced, after 3 months at 10°C in darkness, by six homothallic isolates out of 38 tested. In general, perithecia were larger than protoperithecia both in ascocarp diameter and in neck length. Ascocarp diameter, width of asci and length of ascopores of in vitro‐produced perithecia were larger than those of perithecia produced in nature. The latter showed a neck length longer than in vitro‐produced perithecia. Virulence of isolates when inoculated on J. regia was correlated with colony growth rate, but rated independently for homothallic or heterothallic isolates. A preliminary screening for sources of resistance to anthracnose in the genus Juglans showed J. sieboldiana and J. cinerea to be highly resistant and both J. nigra and J. hindsii to be highly susceptible to the disease. Juglans regia showed an intermediate response of susceptibility to anthracnose.

<i>Short communication</i> First rainfall data from the KZN Drakensberg escarpment edge (2002 and 2003)

Rainfall measured on the KwaZulu-Natal Drakensberg escarpment, the first from above 2 800m a.s.l., are presented from two locations. Total rainfall at the top of Sani Pass (2 850 m a.s.l.) in the southern Drakensberg was 742 mm in 2002, while the January months of 2002 and 2003 averaged 109 mm. Rainfall on Sentinel Peak (3 165 m a.s.l.) in the northern KZN Drakensberg during 2003 totalled 765 mm and 145 mm was measured in January 2003. Recorded rainfall was marginally lower than, but within 6% of, rainfall recorded at adjacent lower altitude Drakensberg stations over the same period. The number of rain days increased marginally with altitude and the data suggest that even though the amount of rainfall on the escarpment is similar to that at lower altitude, the frequency of rainfall events is higher on the escarpment. Although 2002 and 2003 were dryer than normal years in the region, comparisons between these data and prior estimations, where rainfall was expected to range between 1 500 and 2 000 mm/a, shows that totals for the summit of the escarpment could have been over-estimated in the past. Measurement of rainfall is ongoing. Water SA Vol.31 (3) 2005: pp.399-402

Spatial and temporal variability of precipitation maxima during 1960–2005 in the Yangtze River basin and possible association with large-scale circulation

Summary This study investigated spatial and temporal patterns of trends of the precipitation maxima (defined as the annual/seasonal maximum precipitation) in the Yangtze River basin for 1960–2005 using Mann–Kendall trend test, and explored association of changing patterns of the precipitation maxima with large-scale circulation using NCEP/NCAR reanalysis data. The research results indicate changes of precipitation maxima from relative stable patterns to the significant increasing/decreasing trend in the middle 1970s. With respect to annual variability, the rainy days are decreasing and precipitation intensity is increasing, and significant increasing trend of precipitation intensity was detected in the middle and lower Yangtze River basin. Number of rain days with daily precipitation exceeding 95th and 99th percentiles and related precipitation intensities are in increasing tendency in summer. Large-scale atmospheric circulation analysis indicates decreasing strength of East Asian summer monsoon during 1975–2005 as compared to that during 1961–1974 and increasing geopotential height in the north China, South China Sea and west Pacific regions, all of which combine to negatively impact the northward propagation of the vapor flux. This circulation pattern will be beneficial for the longer stay of the Meiyu front in the Yangtze River basin, leading to more precipitation in the middle and lower Yangtze River basin in summer months. The significant increasing summer precipitation intensity and changing frequency in the rain/no-rain days in the middle and lower Yangtze River basin have potential to result in higher occurrence probability of flood and drought hazards in the region.

Saprophytic Colonization of Citrus Twigs by Diaporthe citri and Factors Affecting Pycnidial Production and Conidial Survival.

Melanose, caused by Diaporthe citri, produces reddish brown lesions on the fruit, leaves, and twigs of citrus trees, and greatly reduces the marketability of fresh fruit. Most of the inoculum is produced in pycnidia on dead twigs in the tree canopy, which exude large numbers of conidia in slimy masses. In this study, detached twigs inoculated with conidia were readily colonized and produced large numbers of pycnidia within 30 to 40 days when they were soaked 3 to 4 h on alternate days. Conidial production was measured by wetting twigs in a rain tower periodically and collecting the conidia in the runoff water. Production began after 80 days and continued for nearly 300 days. In other experiments, production of mature pycnidia on detached twigs was greatest at 94 to 100% relative humidity (RH) and at 28°C. Low RH and temperature, however, favored survival of conidia in exuded masses on twigs. In the field, colonization of detached twigs by D. citri was high in rainy season, moderate in spring and early fall, and minimal in late fall and winter. Twig colonization was positively related to the number of rain days and average temperature, but not to total rainfall. In another experiment, inoculated twigs placed in the tree canopy developed pycnidia and then produced conidial masses for about 200 days. D. citri is a serious pathogen, but a weak parasite, that survives primarily by colonization and reproduction on dead twigs.

MM5 simulations of interannual change and the diurnal cycle of southern African regional climate

Two cumulus convection and two planetary boundary layer schemes are used to investigate the climate of southern Africa using the MM5 regional climate model. Both a wet (1988/89) and a dry (1991/92) summer (December–February, DJF) rainfall season are simulated and the results compared with three different observational sources: Climate Research Unit seasonal data (precipitation, 2 m surface temperature, number of rain days), satellite-derived diurnal precipitation and the Surface Radiation Budget diurnal short-wave fluxes and optical depth. Using the ETA model boundary layer in MM5 simulates too much incident short-wave radiation at the surface at 12 UTC, whereas the medium range forecast model boundary layer yields a diurnal cycle of short-wave radiation closer to the observed. The Betts-Miller convection scheme in MM5 simulates peak rainfall later in the day and less rain days than observed, whereas when using the Kain-Fritsch convection scheme a peak rainfall earlier in the day and more rain days than observed are simulated. The intensity of the hydrological cycle is therefore dependent on the choice of convection scheme, which in turn is further modified by the boundary layer scheme. Precipitation during the wet 1988/89 season is reasonably captured by most simulations, though using the Betts-Miller scheme more accurately simulates rainfall during the dry 1991/92 season. Mean DJF biases in the surface temperature and diurnal temperature range are consistent with biases in the number of rain days and the diurnal cycles of surface moisture and energy.

A Sudden Change In Rainfall Characteristics In Amman, Jordan During The Mid 1950s

This study examines recent changes, trends and fluctuations in the total rainfall and number of rainy days at Amman Airport Meteorological (AAM) station in Jordan during the period 1922-2003. The occurrence of abrupt changes and trends were examined and identified using the Pettitt test, a combination of cumulative sum charts (CUSUM) and bootstrapping and the sequential version of Mann-Kendall rank tests. A sudden change and shift in the average of the total rainfall and annual number of rain days occurred in 1957. Annual total rainfall series from Madaba and Mafraq stations are also analyzed and showed similar change and shift points as that which appeared in AAM station. The analysis prevail a decline in the total rainfall and number of rain days in the second half of the past centaury.