Types Of Seasonal Variation Research Articles

A Bayesian test for seasonality in medical data

In medical research, the results from seasonality analyses provide valuable information that eventually can help to clarify the etiology of poorly understood diseases. We present a Bayesian procedure for the analysis of seasonal variation in medical data. The method is a Bayesian version of a frequentist test that performs very well. Statistical seasonality analyses of medical data often involve a short time series, 12 observations with small amplitude and small sample size. Among the specialized procedures already developed for such analyses, only one is Bayesian; the method we present in this paper appears to be the second such Bayesian procedure. Easy to understand and apply, the method is versatile because it can be used to analyze different types of seasonal variation. We illustrate the procedure’s application with two examples of real data.

Pattern of dermatoses in preschool children in a teaching hospital in Uttarakhand, India

Introduction: Dermatoses are a common occurrence in preschool paediatric population in Uttarakhand. Objective: The present study was conducted, to document prevalence and the type of skin disorders prevalent in preschool age group children, attending dermatology OPD in a medical college in Uttarakhand, India. Material and Method: A total of 721 children up to 5 years of age, who presented with dermatoses in pediatric dermatology clinic of department of Dermatolgy Venereology and Leprology (DVL), SGRRIM and HS and associated Shri Mahant Indiresh Hospital, Dehradun, Uttarakhand, India, were selected between 06 Sep 2013 to 05 Sep 2014 in this prospective study. The diagnosis was based upon detailed clinical examination, necessary investigations and dysmorphologic features, if any. Results: Infections and infestations were commonest disorders contributing to 36.46% of all cases. Major infections/ infestations were viral (9.76%) followed by scabies (9.29%), fungal (9.01%) and bacterial (8.46%). Higher incidence of viral infection was due to outbreak of HFMD in months of Sep and Oct I 2013 in Dehradun. There was significant change in bacterial infections according to season. Bacterial infections were more common in summers and mansoon seasons. Fungal and viral infections did not show this type of seasonal variation. In our study most of parasitic skin infestations were due to scabies (9.43 %).Other important groups of dermatological disorders were dermatitis in 29.63% cases out of which seborrheic dermatitis (10.12%), atopic dermatitis(5.96%), Ptyriasis alba (5.96%), non specific eczema (3.46%) and contact dermatitis (2.77%). Other skin diseases included papular urticaria / insect dermatitis (8.46%), naevi / developmental lesions (4.02%), pigmentary disorders (3.32%), sweat gland disorders (2.08%) and miscellaneous group (6.38%) respectively. Pigmentary lesions prevalence was higher in girls. Conclusions: Infections and infestations were commonest cause of dermatoses in preschool children (36.46%), followed by dermatitis (29.63%). Bacterial infection showed seasonal variation and pigmentary lesions were more prevalent in female children.

Latitudinal effect on the diurnal variation of the F2 layer at low solar activity

The latitudinal effect on the diurnal variation of the F2 layer peak parameters at low solar activity was investigated. Our results reveal that the likelihood of the occurrence of a noon-bite out is reduced with increase in latitude. Beyond 21.770°N geomagnetic latitude, it is hardly noticed. Daytime maximum NmF2 peak occurs mostly after midday in the northern hemisphere. Similar variations occur in the southern hemisphere, although it varies with the seasons, and latitudes. The maximum ionization decreases with increase in latitude and NmF2 values during the equinoxes are higher than those of the solstice seasons, in the northern hemisphere. It is entirely different in the southern hemisphere. The rate of decay is faster during the solstice than during the equinoxes. Maximum hmF2 values occur at the equatorial ionosphere; the least is in the mid-latitude region. The time of formation and position of the EIA crests is observed to be asymmetric. It appears to be more consistent in the northern hemisphere than the south. These types of seasonal variations have been attributed to the daytime meridional wind, equatorial fountain effect and the location of the subsolar point in relation to the magnetic equator.

El análisis de la Variación Estacional en medicina

Se divulgan métodos recientes para el análisis de la variación estacional en medicina. Estos métodos son efectivos aun cuando los datos presentan pequeña amplitud y el tamaño de la muestra es bajo, dos características a menudo presentes cuando uno realiza este tipo de análisis. Los métodos tratan los dos casos: un solo grupo y múltiples grupos. Además, estos métodos sirven para analizar distintos tipos de variación estacional. La aplicación se ilustra por medio de ejemplos con datos reales.

Analysis of the relationship between the North Atlantic oscillation and sea‐level changes in northwest Europe

AbstractThe impact of the North Atlantic oscillation (NAO) on sea level around northern European coasts is explored on the basis of mean monthly sea level time series back to the 19th century at 10 sites. Two types of relationship with the NAO are found. Most of northern Europe shows a positive relationship with higher sea levels under stronger NAO conditions, which is clearer for the winter season. In contrast, a negative relationship exists to the south, covering southwest England. Both the relationships are variable in time and were enhanced during recent decades, possibly due to movements of the NAO‐related pressure centres. The analysis of the NAO and sea level variability in different frequency bands suggests that the relationship is strongest at the annual and interannual time scales at all sites. The NAO is also strongly correlated with decadal and longer term sea level changes in the Baltic Sea. The wavelet spectral power peaks at about 12 months for the NAO and 13–15 months for sea level. Unusually strong and weak annual cycles in sea level are closely related to two types of seasonal variation in the NAO. The anomalous annual cycles in sea level tend to lag those in the NAO by a month for most of the sites analysed, suggesting that sea level does not simply respond to the pressure forcing, but is additionally responsive to changes in thermal conditions and fluxes associated with the NAO. Copyright © 2004 Royal Meteorological Society.

A comparative study on nitrogen-concentration dynamics in surface water in a heterogeneous landscape

With point-source pollution controlled effectively, nonpoint-source pollution, especially that resulting from agricultural land, has become the main factor affecting surface water. Much attention has been focused on the impact of fertilizer and pesticide application, wastewater irrigation, and land management on pollutant transport. However, landscape pattern also plays an important role in pollutant transport and detention. Landscape types may be classified into two parts: source and sink landscapes, based on their functions in pollutant transport and detention. As a major contributor to eutrophication of waterbodies, nitrogen loss with runoff has received particular attention when studying nonpoint-source pollution. In this study, four watersheds in the upper parts of the Yuqiao Reservoir Basin, Zuihua, Hebei Province, China, were chosen in order to study the relationship between landscape pattern and nitrogen-concentration dynamics. The results indicate that (1) nitrogen concentration in surface water within different seasons in the rainfall-normal year is higher than that in the rainfall-deficit year and (2) the variation of nitrogen concentration within different seasons in the rainfall-deficit year is smaller compared with that in the rainfall-normal year in which two types of seasonal variation on nitrogen concentration are presented. The first variation occurs when nitrogen concentration is lowest in the dry season, and rises rapidly from the dry season to rainy season and then declines quickly from the rainy season to mean-flow season. This mainly occurs in those areas where most source landscapes are close to the monitored waterbody. The second variation occurs when nitrogen concentration is low in the dry season, increases rapidly in the rainy season but does not reach its peak value until the mean flow season. The second variation occurs in those areas where source landscape types are spread over the whole watershed. There is no clear relationship between watershed shape, relative importance of landscape types, and nitrogen concentration; however, the spatial distribution of source and sink landscape types in the watershed has a strong impact on the nitrogen concentration in surface water.

CH 4 emission and oxidation in Chinese rice paddies

In the paper, the characteristics of CH4 emission from the rice paddies, its temporary and spatial variations as well as factors regulating CH4 emission and oxidation are reviewed with an emphasis on CH4 emission from rice paddies in China. The observed four types of diel variation and two type of seasonal variation can be explained by the variations of methane production in the soil and the transport efficiencies of the three transport routs. The inter-annual variation of CH4 emission from rice fields is significant, but the process causing this change is very complicated and unclear based on the available data at present. The large special variation, more than 10 times difference, of the total season methane emissions observed in various rice fields in China, is largely attributed to soil type difference although both soil physics and chemistry are important. Rice growing activities regulate the diel and seasonal variation patterns of the methane emissions. Drainage of flooded water may significantly reduce the emission. Organic fertilizer may enhance the emission, while some of the chemical fertilizers may reduce the emission. Local climate conditions, average temperature and annual rainfall, may be responsible for part of the observed year to year differences of the total season emission. Estimates of total emissions of CH4 from Chinese rice fields, based on field measurement and model calculation, are 9.7–12.7 Tg/year and 8.17–10.52 Tg/year respectively, for the year of 1994. Oxidation of CH4 reduces the emission of CH4 produced in the soil of rice field to the atmosphere. The most likely sites for CH4 oxidation in rice fields are the water–soil interface and the rhizosphere. When the flood water dries up in irrigated fields, the oxidation of CH4 in the soil is more important and can partially explain the lower emission rates during the last period before harvest in most experiments. The magnitude of oxidation in the rhizosphere is not well known. Good correlation between methane reduction and O2 mixing ratio in the soil has been found in most soil types. Methane oxidation rate is mainly controlled by the gas transport resistance in the soil. The oxidation rate increases with the increase of temperature in the temperature range of 5–36 °C.

Arctic sea-ice oscillation: regional and seasonal perspectives

AbstractVariability of the sea-ice cover (extent) in the Northern Hemisphere (Arctic and subpolar regions) associated with the Arctic Oscillation (AO) is investigated using historical data from 1901 to 1997. A principal-component analysis (empirical orthogonal functions (EOFs)) was applied to sea-ice area (SIA) anomalies for the period 1953−95. The leading EOF mode for the SI A anomaly shows an in-phase fluctuation in response to the AO and is called the Arctic sea-ice oscillation (ASIO). Arctic sea ice experiences seasonal variations that differ in timing and magnitude. Four types of seasonal variation are identified in the Arctic sea ice, and are superimposed on long-term interannual to decadal variability. Consistent with the total Arctic SIA anomaly eight regional SIA anomalies have shown significant in-phase decrease (downward trend) since 1970, possibly part of a very long-term (century) cycle. Thus, it is recommended that SIA anomalies in the sensitive seasons be used to better capture interannual, interdecadal and longer (century) variability. Major decadal and interdecadal time-scales of SIA anomalies are found at 12−14 and 17−20 years. In the Sea of Okhotsk, a century time-scale is evident. The reduction rate (negative trend) of the total Arctic sea-ice cover in the last three decades is −4.5% per decade, with the summer rate being the highest (-10.2% per decade). The contribution to this total reduction varies from region to region, with sea-ice cover in the Greenland and Norwegian Seas experiencing the highest reduction rate of −20.2 % per decade.

Mechanism of Suspended Sediment Supply to Headwater Rivers and Its Seasonal Variation in West Central Hokkaido, Japan.

Source of suspended sediment was identified from grain size distribution in two headwater basins in West Central Hokkaido, Japan. The fine grains in river bed sediment were supplied to the river water as suspended sediment in the early snowmelt season, whereas those in hillslope sediment were washed out into the rivers in the summer rainy season. The fine grains probably accumulated in the bed sediment during winter, and were stirred up into river water as the river discharge increased. Since the fine grains in the river bed sediment were gradually exhausted, further stirring up could occur only when the river discharge exceeded that season's previous maximum. The fine grains in the hillslope sediment were most likely to be stored during the dry period from May to July, only to be washed away during the summer rainy season. Thus the suspended sediment supply from the hillslope is sparse in the snowmelt season. This type of seasonal variation in suspended sediment supply is probably common to headwater basins in the cold and humid climate of West Central Hokkaido, Japan.

Deseasonalization of mortality in the world.

The statistical analysis of the seasonal variation of mortality in the 1960's in Japan and the Western countries reveals that the seasonal variation curve has become much flatter in the cold regions (Scandinavia, USA, Canada) and that deaths remain concentrated in winter in the comparatively warm region (Japan and the West Europe). Both types of seasonal variation have undergone chronological changes from decade to decade. In the USA the former seasonal type curve has become so flat that mortality might well be said to have been "deseasonalized", while in the other regions the concentration of deaths in the cold season has been growing more conspicuous in recent years. All this can be ascribed to the differences in the system of room heating.

死亡の季節変動の統計的解析

Based upon their previous studies in the concentration of deaths in winter in Japan and the West European countries, on the one hand, and, on the other hand the considerable moderation of seasonal variation in mortality, or rather “ deseasonalization ” of deaths, in the Scandinavian countries and the United States in this paper the authoresess attempt to analyze quantitatively the difference between these two types of seasonal variation in mortality and specifically the geographical difference in relationship between mortality (stroke and infant) and temperature in the three cities of London, Tokyo and New York, and they sincerely want to build up one of the groundworks necessary for long-term biometerorological forecast. For such statistical analysis, census method II and covariance analysis in the twoway layout are used.1. As for the seasonal variation of mortality, time series analysis appears to be the effective statistical methods. Thus, census method II has been adopted to analyze a time series of stroke mortality. Generally, the time series is composed of the trend cycle (TC) the seasonal variationcomponent (S) and the irregular component (I), but the second named alone is studied in this paper because it calls for serious considerations from the biometeorological standpoint. The time series cycle of the seasonal variation component is naturally regular in the three cities, but the amplitude is much smaller in New York than in London and Tokyo. The correlation coefficient between stroke mortality and temperature in terms of the seasonalcomponent comes at -0.9709 for Tokyo, or slightly larger than -0.9281 for London and -0.9015 for New York. As there is some time lag between mortality and temperature, the correlation coefficients are calculated with one to five months shifted, and it is seen that the coefficient is the largest for Tokyo in case there is no time lag, and that it appears to reach the peak, if half a month is shifted, for London and New York. Details of the time series analysiswith census method II will be published later.2. Covariance analysis indicates that there is no significant difference among the three cities between the regression equation of mortality (stroke and infant) on temperature in spring and that in autumn in the 1960's, so the changes per 10°C in the death rate are calculated by average regression coefficient. Mortality is inversely related to temperature, and the increase or decrease per 10°C in the death rate for stroke turns out to be larger than that for infant mortality in the three cities. In both Tokyo and London, the rise of the death rate for stroke in autumn is considerably large, or 24.0% and 32.4%, respectively, contrasted to only 8.3% in New York (over three and four times larger, respectively).As for infants, the mortality rate decreases or increases very slightly (not more than 1.5%) in New York along with the ups and downs of temperature. The corresponding rate of increase or decrease comes at about 8-9% in London. In Tokyo, however, the infant death rate declines by about 16.0% with tempearture up 10°C and goes up by as much as 17.5% with the similar drop of temperature.The changes in death rate with the variation of temperature turn out to be the smallest in New York among the three municipalities. All this clearly indicates that central heating, widely adopted in the American city, has brought about favorable bearings upon mortality, especially that of infants who can live in the artificial climate. It is also to be noted that mortality from stroke undergoes much larger changes with the ups and downs of temperature in London than in Tokyo, and vice versa in the case of infant mortality.