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[en] The possibility of detecting easterly propagating low frequency signals in the Southern Hemispheric circulation is explored in connection with the assessment of a possible seasonal rainfall forecast in central Chile. The analysis has focused on the seasonal variability associated with the biennial component of the Southern Oscillation (SO) and on the one resulting from superimposed intraseasonal oscillations, in relation with winter precipitation and individual rainfall events, respectively. Based on a previous work, relating wet winters to frequent blocks to the SW of South America during warm events of the SO, time-longitude cross sections of a 5-day average blocking index (BI) calculated from ECMWF 200 hPa daily hemispheric analyses for the period 1980-1987 are presented. A general eastward displacement of western and central Pacific positive BI areas seems to characterize the developing phase of warm SO events and vice versa, while intraseasonal variability patterns appear to be related to single rainstorms, either when the positive BI phase of the wave amplifies while crossing the western Pacific or when it reaches the far southeastern Pacific, frequently with a double block structure. It is concluded that the behaviour of both sources of variability is consistent with previously described teleconnection patterns for ENSO events in the southern winter, and that a primary prospect for winter precipitation and for the occurrence of relatively large individual rainstorms in central Chile could be obtained following the filtered BI and 500 hPa height anomalies in both time scales during the fall season. (author). 28 refs, 12 figs
[en] Intercropping forage legumes and cereal crops could assist smallholder farmers to increase the quantity and quality of livestock feeds per unit land particularly during dry season. Two studies were carried out in the upper midland zone (UM1) at Kisii (UM4) at Kitale to asses the effects of intercropping forage legumes and maize on maize grain yield and quantity of livestock feeds. In the first study, five annual/biannual legumes comprising of three- grain type and two herbaceous forage legumes were intercropped with maize at Kisii and Kitale. The second study involved three perennial forage legumes. Results of two cropping seasons at Kitale and three seasons in Kisii are reported.. Intercropping of grain type legume with maize had no significant effects on maize grain yield and stover DM yield at both sites.However, the herbaceous forage legumes (Dolichos lablab cv. Rongai and Macuma pururiens) significantly reduced maize grain yield compared to maize top dressed with 60 kg N ha-1 although maize stover and legume DM yields were not significantly affected. Total forage yields (maize stover + legume herbage) were significantly increased in forage legume intercrops (P < O.OO1). Perennial legumes did not significantly affect maize grain and stover yields during the establishment season. In subsequent seasons, continuous cropping of of maize in an already established Desmondium unicinatum plots significantly reduced maize grain yield, while defiliation of Desmondium uncinatum plots at regular intervals of six weeks did not significantly reduce maize grain yield. Decrease in maize grain yield were associated with legume herbage yields above 3 t ha-1. The results demonstrate that increased quantity and quality of dairy cattle feed may be achieved by intercropping forage legumes and maize although it may cause some reduction in maize yield. Practical implications of this technology in terms of economic evaluation are discussed significantly reduced maize grain yield. Decreases in maize green yield were associated with legume herbage yields above 3 t ha-1. The results demonstrate that increased quantity and quality of dairy cattle feed may be achieved by intercropping forage legumes and maize although it may cause reduction in maize yield. Practical implications of this technology in terms of economic evaluation are discussed
[en] Extra virgin olive oil was produced from olives of the two main varieties cultivated in the region of Rhytmaton in the Greek island of Crete named Throumbolia, and Koroneiki. The former is very famous due to the natural way of fruit debittering, while the latter is the most common olive variety cultivated in Northern Greece. The olives were harvested at three successive stages of ripening according to their skin color and the extra virgin olive oil was extracted using an experimental olive oil extraction mill at 30 degree centigrade. Peroxide value, UV absorption, acidity, fatty acid content and total polyphenols were measured and the contents of tyrosol, hydroxytyrosol 3,4- DHPEA-EDA, p-HPEA-EDA and 3,4-DHPEA-EA were determined by HPLC. The sterol fraction and the volatile component profile were determined by GC and SPME GC/MS, respectively. Throumbolia olive oil presented an extremely higher content of β-sitosterol and linoleic acid (n6) in comparison to the Koroneiki variety. The concentration of linoleic acid decreased in olive oils produced from both varieties in contrast to oleic acid which increased at the same time. Furthermore, the content of OH-tyrosol was higher, while the content of 3, 4-DHPEA-EDA and the total polyphenols was lower in Throumbolia olive oil than in olive oil produced from the Koroneiki variety. In general, significant differences were observed in all parameters between the olive oils produced from the two varieties during different stages of maturation. (Author) 41 refs.
[en] Based on an analysis of hindcasts from a seasonal forecast system, complemented by the analysis of a large ensemble of AMIP simulations, possible causes for skillful prediction of the winter Arctic Oscillation (AO) on a seasonal time-scale are analyzed. The possibility that the recent increase in AO skill could be due to model improvements, or due to changes in the persistence characteristics of the AO, is first discounted. The analysis then focuses on exploring the possibility that the recent increase in prediction skill in AO may be due to sampling variations or could have physical causes. Temporal variations in AO skill due entirely to sampling alone cannot be discounted as this is a fundamental constraint on verifications over a short time-series. This notion is supported from theoretical considerations, and from the analysis of the temporal variations in the perfect model skill where substantial variations in skill due to sampling alone are documented. As for the physical causes, the analysis indicates possible links in the prediction skill of AO with the SST forcing from the tropics, particularly related to the SST variations associated with the Trans-Niño Index (TNI). Interannual and low frequency variations in the TNI could have contributed to similar temporal variations in AO skill. For example, a dominance of central Pacific El Niño events after 2000 (a reflection of low-frequency variations in TNI) coincided with an increase in the prediction skill of AO. The analysis approach and results provide an avenue for further investigations; for example, model simulations forced with the SST pattern associated with the TNI, to establish or reaffirm causes for AO skill.
[en] Trends in extreme temperature and rainfall were analyzed for two Caribbean islands in close proximity: Tobago (Crown Point) and Trinidad (Piarco) for the most recent period 1985–2015 using daily data. Most annual extreme temperature indices at Crown Point show no significant warming. However, warming at Crown Point manifests during the wet season and strongly in September. In contrast, most extreme temperature indices at Piarco show significant warming trends on annual and seasonal scales as well as for most months. Extreme precipitation indices show few trends. For Crown Point, trends indicate an increase in annual precipitation totals and extremely wet days were observed, whereas no significant trends in annual indices were found for Piarco. The greatest 5-day rainfall amounts were found to increase during the dry season at both sites. When compared to previous regional studies, this specific territory approach highlights that most indices with no significant regional trends also do not show trends at the local scale. Furthermore, differences in trends between these two nearby sites, 80 km apart, indicate that there is a spatial variation in warming trends.
[en] In this study, the trends of the annual and seasonal temperature and its variations are explored in the Tamil Nadu State of India. In order to find the trend direction and the magnitude of change across the state during 1969–2016, the mean maximum temperature (MMaxT), mean minimum temperature (MMinT), and mean annual temperature (MAT) of 17 climatological stations are analyzed. Evidently, the increasing trends in MMaxT, MMinT, and MAT are observed at the majority of the stations. Approximately 82% of the total stations have shown a significant positive trend in MAT and MMaxT at the 95% confidence level. The MAT has increased up to 1.4 °C with a variation in the rate of change from 0.01 to 0.29 °C per decade. MMaxT has shown a significant increase with a variation in the rate of change from 0.01 to 0.54 °C per decade for the last 47 years. However, MMinT has shown an increasing trend in 13 stations and a decreasing trend in 4 stations with a variation in the rate of change from − 0.05 to 0.31 °C per decade. In the recent decades, the majority of the stations have experienced high warm and the year 2016 is observed to be the warmest year. Based on a spatial scale, temperature differences have been observed between coastal and inland stations. The majority of the coastal stations have shown a high increase in MMaxT as compared to the inland and hill stations. On the contrary, the inland stations have shown a high increase in MMinT as compared to the coastal stations. A more definite increasing trend is observed during the winter and postmonsoon seasons followed by the monsoon season.
[en] Two stations located in the oriental part of the Mitidja plain were studied. The first one is situated in Ramdhania and the second in Baraki. During the spring period, the study of Lanius meridionalis pellets demonstrates that, in both stations, the relative values of the consumed biomass are high: 46.3% in Ramdhania and 76.1% in Baraki (A.R. % > 2xm; m=25%). During the winter period, Ramdhania station is still strongly represented (45.8%). This rate is weaker in Baraki station (3.9%). The other seasons (summer and autumn) are sightly represented. (author)