Precipitation characteristics over Paradeep

The daily rainfall records since 1976 and the SRRG records after its installation in 1982 at Paradeep have been analysed and rainfall climatology has been worked out. The heaviest 24-hour rainfall recorded at the station is 264 mm on 4 June 1982. The mean annual rainfall is 1475 mm. January and December are near dry months while August is the wettest month getting about 339 mm rainfall. The variability of annual rainfall here is 20 %. Light rainspells giving a total rain of 10 mm or less form about 50% occasions in pre-monsoon period and 63% of occasions in monsoon period. The extended rainspells lasting for more than 4 hours form about 10% of occasions in pre-monsoon season and 6% occasions in monsoon season. While morning (04-08 hr IST) period gets the rainfall in both pre-monsoon and monsoon months, early night gets the peak rainfall activity during the pre-monsoon months.

Standardized Precipitation Index Comparison along the Limbe-Bamenda Axis of the Cameroon Gulf of Guinea

Mean monthly rainfall decline with continentality is a commonplace phenomenon that has been used in this study to compare its trend in Bamenda in the Western Highlands and Limbe on the Atlantic lowland coast. This study attempts to bridge some of the methodological gaps in the previous studies on rainfall variability in Cameroon that had emphasized only the inter-annual variability and coefficient of variation without focusing on the specific indices and contrasts between different ecological zones. In this study, a comparative analysis has been done of the standardized precipitation index (SPI) for Bamenda and Limbe, using data from 1985–2015. The analysis involved the mean annual rainfall (176.88 mm and 419.9 mm), its standard deviation (SD) (22.98 and 102.42), and the coefficient of variation (CV) (12.99% and 24.41%) for Bamenda and Limbe, respectively. The results show that the mean annual rainfall for Bamenda is decreasing, whereas that of Limbe is increasing. The mean SPI is –0.01 (mild dryness) and 0.02 (mild wetness) for Bamenda and Limbe, respectively. These results have far-reaching implications for the development of agriculture, water resources management, and other man-environment interaction variants.

Avaliação de metodologias de transferência de vazões de referência em bacias hidrográficas: sua aplicação na bacia do rio Japaratuba - Sergipe - Brasil

Para avaliar a disponibilidade de água e definir as áreas de inundação nas bacias hidrográficas, é necessário considerar a vazão mínima, média e máxima, denominadas de vazões de referência, e isto requer dados observados de vazão, que são bem escassos em bacias brasileiras, principalmente as pequenas e médias bacias. Para superar esta falta, utiliza-se dados de bacias contribuintes com comportamento hidrológico similar, que são transferidos por meio de operações matemáticas, utilizando variáveis físicas e climáticas. Tais procedimentos, geralmente, são mal avaliados quanto à sua precisão. Assim, objetivou avaliar a acurácia da estimação de cinco vazões de referência em quatro estações de medição dos dois principais afluentes do rio Japaratuba (Sergipe, Brasil), os rios Japaratuba-Mirim e Siriri. Os resultados mostraram diferentes comportamentos para as duas sub-bacia, quer seja pelas variáveis influentes, quer seja pelos efeitos antrópicos como a mudança no uso do solo que precisam ser melhor avaliados. Para a bacia do rio Japaratuba-Mirim a transferência de vazões mínimas e médias deve ser realizada considerando-se o produto área x precipitação média anual e para as vazões máximas deve-se considerar o comprimento do rio até a seção. Para a bacia do Siriri, os melhores resultados de transferência de vazões médias e máximas foram obtidos com o produto "área x precipitação média anual” e a variável "precipitação média anual" gerou um erro menor para as vazões mínimas. Assessing the reference flow transfer methodologies in watersheds: their application at Japaratuba River Basin – Sergipe State – BrazilA B S T R A C TIn order to evaluate the water availability and define the flood areas in the river basins, it is necessary to consider minimum, medium and maximum discharge, called reference flows requiring records on flow data, quite scarce in Brazilian river basin, mainly those of small and medium scale. To overcome this gap, data from nearby basins with similar hydrological behavior are used, based on mathematical operations involving physical and climatic variables of the contributing basins. However, these procedures are poorly evaluated for their accuracy. Thus, this study aimed to evaluate the accuracy of the estimation of five reference flows through the transfer of information, using physical and climatic variables in four gage stations of the main tributaries of the Japaratuba river basin (Japaratuba-Mirim and Siriri river) - Sergipe State, Brazil. The results showed different behaviors for the two sub-basins as for either by influential variables or by anthropic effects such as land use and land cover changes that need to be better evaluated. The flow transfer to the subbasin of the Japaratuba-Mirim river should be performed considering the product "Area x Mean annual rainfall" for minimum and medium flows. For maximum flows the "Length" of the basin should be considered. For the Siriri river basin, the "Mean annual rainfall" variable generated a smaller error in the minimum flows and the product "Area x Mean annual rainfall” led to better results for medium and maximum flows.Keywords: Water resource management; statistical hydrology; geographic information systems.

Recent Rainfall Variability Over a Dryland Ecosystem of North Western India

In this study, an attempt has been made to examine the recent rainfall variability by means of daily rainfall data of 33 well spread stations over dryland ecosystem of Rajasthan in north western India during 1961-2017. For trend analysis, Mann-Kendall, Sen’s slope estimator and simple linear regression test have been used (at 95% confidence level). The results have shown a high interannual variability in rainfall occurrence varying from 277 mm (in year 2002) to 839 mm (in year 1975) with mean of 583 mm over this dryland ecosystem. Most of the rainfall deficit years have occurred with El-Nino years. The mean annual rainfall has shown a marginal non-significant upward trend over the ecosystem. The station-wise mean annual rainfall has revealed a significant rising trend over Barmer, Churu, Ganganagar, Jaisalmer and Pratapgarh stations. Interestingly, three year running average has shown a cyclic pattern of rainfall over dryland ecosystem under the changing climatic conditions. The spatial pattern has exhibited that the mean annual rainfall decreases from east and south east (more than 850 mm) to west and north west (less than 400 mm), which is mainly associated with the presence of Aravalli Mountains spreading north east to south west in central Rajasthan. Remarkably, majority of stations positioned in western parts of dryland ecosystem have shown increasing rainfall trends, whereas some stations located in eastern parts have recorded a non-significant declining trend. The magnitude of significant rising trend has varied from 5.34 mm/year (Pratapgarh station) to 2.17 mm/year (Jaisalmer station). Also, the frequency of heavy rainfall events has shown a positive trend with significant increasing trends over Bharatpur, Jaisalmer and Pratapgarh stations, whereas Bundi station has shown significant decreasing trend.

Cymbopogon citratus (lemongrass).

Genetics: The chromosome number reported for C. citratus is 2n = 40 (Flora of China, 2016). Reproductive biologyIn most places Cymbopogon citratus flowers very rarely or not at all. It mostly reproduces vegetatively (Oyen, 1999). Physiology and phenology: In China, C. citratus has been recorded flowering and fruiting during summer (Flora of China, 2016). Longevity: Cymbopogon citratus has a life-span of 4-6 years (Oyen, 1999). Environmental requirements: Cymbopogon citratus grows best under sunny, warm and humid conditions at elevations below 750 m, with mean annual temperatures ranging from 23°C to 30°C and mean annual rainfall between 2500-3000 mm. It is adapted to grow on a wide variety of soils types, but prefers well-drained soils with pH ranging from 5.5 to 7.5. However, this species has been recorded growing in Australia on clay soils with pH=9.6. It does not tolerate saline soils or frosty conditions (Oyen, 1999).

Evaluating climate effects over long-term salts accumulation in hyperarid soils using stochastic modeling

<p>Hyperarid (< 80 mm yr<sup>-1</sup>) soils in hot deserts are characterized by accumulations of soluble salts (gypsum and halite) in diagnostic horizons as a result of limited moisture availability. In most desert terrains, the source for pedogenic gypsum and halite is atmospheric dust and rainwater. The interplay between climatic properties such as frequency and intensity of rain events, rainfall composition, dust flux, and evaporation rates, govern the depth and concentration of these salts. Better understanding of these relationships can improve our estimation of regional paleoenvironmental and paleoclimate conditions. Up to date, only empirical correlations between annual rainfall and pedogenic salt horizons are available.</p><p>The goals of this study are to: 1) quantify rates of pedogenic gypsum accumulation with time and the role of controlling climatic conditions that govern its accumulation, 2) estimate the most likely climatic scenarios that led to the formation of the diagnostic gypsic horizon developed in late Pleistocene (~ 60 ka) abandoned alluvial fan surfaces in the hyperarid Negev desert,  southern Israel. To achieve these goals, we constructed a compartment model that simulates gypsum accumulation in soil and tests its sensitivity to various changes in the long-term climate properties. The model predicts gypsum content and depth of accumulation in the soil profile over thousands of years and more. The input parameters are stochastically simulated rainstorms, evaporation, dust flux, and sulfate concentration in rainwater, at daily time steps. The model was tested and calibrated using data of Holocene (< 11 ka) soil profiles developed on stable alluvial fans in the hyperarid Negev. With the assumption that the climate during the Holocene was not much different than today (i.e., mean annual rainfall < 50 mm). Sensitivity analyses indicate that gypsum accumulation is highly sensitive to mean annual rainfall and sulfate concentration in rainwater. Synthetic gypsum profiles were calculated using different climate scenarios and compared to late Pleistocene soils. Our results suggest that: (a) gypsum accumulation in late Pleistocene soils cannot occur simply by extending current climate conditions for a much longer duration. (b) The plausible climate scenarios for the late Pleistocene must include additional rain input (1.5 – 2.0 times than mean annual rainfall today) and increased sulfate concentration in rainwater (2.0 – 2.5 times than today) to successfully reconstruct the observed accumulated gypsum in mature (60 – 12 Ka) soil profiles.</p>

Agricultural community-based impact assessment and farmers’ perception of climate change in selected Ecological Zones in Nigeria

Background The impacts of climate change are affecting sustenance and livelihood of many rural farmers in Africa. The majority of these farmers have low adaptive capacity. This study investigates climate change impacts, farmers’ perception, adaptation options and barriers to adaptation in three selected ecological zones in Nigeria using three staple crops. Rainfall and temperature data of over 35 years were analysed using ANOVA, Mann Kendall and Sen’s Slope Analysis. Farmers’ perception of climate change and cropping experiences were assessed with the aid of a well-structured questionnaire, semi-structured interview and focus group discussion. Results The results of the study revealed high variability in the annual and monthly rainfall and temperature during the study period. The highest annual maximum temperature was recorded in Kwara with Tmax > 32 ℃. Though, there appeared to be spatial and temporal variations in rainfall in the study area, the highest was in Ogun with mean annual rainfall = 1586.9 mm and lowest in Kwara with mean annual rainfall = 1222.6 mm. Generally the Mann Kendall and Sen's slope analysis revealed general increase in the minimum and maximum temperature, while rainfall revealed generally downward trend. The study revealed a difference in farmers’ perception but nearly 74% of farmers perceived that climate is changing, which is affecting their farming activities. Nearly 70% claimed that lack of financial capital is the major barrier to climate change adaptation. Conclusions The study concludes that rainfall and temperature variability have significantly impacted cropping and that farmers are aware of long-term changes in temperature and rainfall, but some are unable to identify those changes as climate change. There is a need for affordable and available improved seedlings and variety of crops that can adapt to climate change conditions.

The convexity of carbonate hilltops: 36Cl constraints on denudation and chemical weathering rates and implications for hillslope curvature

Carbonate hillslopes are often soil mantled and display a classic convex morphology. In this study we examine controls on carbonate hillslope denudation and morphology using a modified regolith mass balance equation to account for chemical weathering and dust input—two fluxes that are commonly neglected in settings with silicate-dominated bedrock. We utilize seven study sites in the Eastern Mediterranean across a significant gradient in the mean annual rainfall and dust deposition flux. Combining cosmogenic 36Cl-derived hilltop denudation rates with an estimate of the regolith chemical depletion and the quantified fraction of dust in the regolith we predict hilltop curvature and compare our predictions with observations based on high-resolution airborne LiDAR (light detection and ranging). Denudation rates vary from 5 to 210 mm/k.y. and increase with mean annual rainfall. Less resistant carbonates (chalk) experience faster denudation rates relative to more resistant dolo-limestone and are less prone to chemical weathering. Soil production exhibits a humped dependency on soil thickness. The observed hilltop curvature varies as a function of rainfall and dust flux with a minimum at sub-humid sites. While trends in hilltop convexity are often solely attributed to variations in erosion rate, our results illustrate the additional effects of dust production and chemical depletion. Our mass balance model implies that drier sites in the south probably experienced a more intricate history of regolith production due to dust flux fluctuations. Thus, by incorporating dust flux and chemical weathering to the classic hillslope evolution model we are able to identify a complex relation between hilltop curvature, soil production, and climate.

Supplemental Material: The convexity of carbonate hilltops: 36Cl constraints on denudation and chemical weathering rates and implications for hillslope curvature

Figure S1: 36Cl denudation rates vs. mean annual rainfall of samples categorized by hillslope position and samples types; Figure S2: fd and CDF vs. mean annual rainfall, derived from immobile elements; Figure S3: Values of soil creep efficiency (K) vs. mean annual rainfall, estimated from numerical modelling and steady state, table with coordinates of study sites location; Figure S4: Photographs of hard dolo-limestone and soft chalk rocks; Figure S5: Mean hillslopes slope vs. mean relief.

Supplemental Material: The convexity of carbonate hilltops: 36Cl constraints on denudation and chemical weathering rates and implications for hillslope curvature

Figure S1: 36Cl denudation rates vs. mean annual rainfall of samples categorized by hillslope position and samples types; Figure S2: fd and CDF vs. mean annual rainfall, derived from immobile elements; Figure S3: Values of soil creep efficiency (K) vs. mean annual rainfall, estimated from numerical modelling and steady state, table with coordinates of study sites location; Figure S4: Photographs of hard dolo-limestone and soft chalk rocks; Figure S5: Mean hillslopes slope vs. mean relief.