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[en] An agro-climatic study was carried out in eastern Indian state of Bihar (middle Indo-Gangetic Plains) to identify optimum planting schedules and water availability of rainfed crops based on moisture availability index (MAI), i.e., the ratio of weekly assured rainfall and potential evapotranspiration (PET) for delineating safe growing period and crop production potential at micro-level in order to develop climate smart agricultural production system. For this purpose, historical weekly rainfall data for a period ranging from 30 to 55 years of 110 rain-gauge stations and normal weekly PET were employed. The assured weekly rainfall at different probability levels, viz. 25, 50, and 75%, was computed employing incomplete gamma distribution technique. The study revealed that at 50% probability (i.e., 50 out of 100 years), the sowing window of rainfed crops with MAI ≥ 0.33 ranged from 19 to 24 SMW (standard meteorological week) over different districts in Zone I (North west alluvial plains), 18 to 23 SMW in Zone II (North east alluvial plains), 23–24 SMW in Zone IIIA (Part of South Bihar alluvial plains), and 24–25 SMW in Zone IIIB (Part of South Bihar alluvial plains). The districts under Zone II recorded the earliest sowing week for starting sowing of rainfed crops, and the most delayed start of sowing was recorded in the districts under Zone IIIB at all probability levels. Kishanganj District recorded the highest duration of water availability followed by West Chamaparan District at all MAI and probability levels. In terms of longer length of water availability and higher values of MAI, Zone II appeared to be the most potential agroclimatic zone followed by Zone I and Zone IIIA. The Zone IIIB was adjudged as the least potential Zone in terms of shorter water availability period for rainfed crop production.
[en] Rainfall is one of the most important components of the hydrological system and the understanding of its spatio-temporal variability is of fundamental importance for the management of hydrographic basins, especially those located in the semi-arid region of Brazil. In this way, the objective of this work is to analyze and classify the historical series of precipitation as to their profiles and trends in the Watershed of Riacho do Navio (WRN), located in the Pernambuco State. Data from the plains of Betânia and Airi, both with a series of more than 30 years of precipitation records. The total annual, monthly, maximum rainfall in a single day and number of rainy days were organized to fit the Gumbel, in order to classify the years of very dry to very rainy ones by the quantis technique and trend determination by the nonparametric test of Mann-Kendall. The pluviometric stations of Betânia and Airi presented 15.8 and 15.5% of the series considered as very dry years, with an average precipitation of 191.0 and 308.1 mm, respectively. The Mann-Kendall test identified a decrease in total annual rainfall, with a reduction of -52.7 mm (-11%) for the Bethany station and -82.2 mm (-10%) for Airi, in 30 years. The decrease in the number of days with precipitation in 30 years is 6 days for Bethany and 20 days for Airi. The reduction of rainfall and the number of rainy days, will probably imply a reduce the surface water and groundwater in WRN and, consequently, there may be changes in the dynamics of the native vegetation and soil erosion increase, causing difficult in the yield to rainfed agriculture from this region. (author)
[en] Soil temperature, an important indicator of climate change, has rarely explored due to scarce observations, especially in the Tibetan Plateau (TP) area. In this study, changes observed in five meteorological variables obtained from the TP between 1960 and 2014 were investigated using two non-parametric methods, the modified Mann–Kendall test and Sen’s slope estimator method. Analysis of annual series from 1960 to 2014 has shown that surface (0 cm), shallow (5–20 cm), deep (40–320 cm) soil temperatures (ST), mean air temperature (AT), and precipitation (P) increased with rates of 0.47 °C/decade, 0.36 °C/decade, 0.36 °C/decade, 0.35 °C/decade, and 7.36 mm/decade, respectively, while maximum frozen soil depth (MFD) as well as snow cover depth (MSD) decreased with rates of 5.58 and 0.07 cm/decade. Trends were significant at 99 or 95% confidence level for the variables, with the exception of P and MSD. More impressive rate of the ST at each level than the AT indicates the clear response of soil to climate warming on a regional scale. Monthly changes observed in surface ST in the past decades were consistent with those of AT, indicating a central place of AT in the soil warming. In addition, with the exception of MFD, regional scale increasing trend of P as well as the decreasing MSD also shed light on the mechanisms driving soil trends. Significant negative-dominated correlation coefficients (α = 0.05) between ST and MSD indicate the decreasing MSD trends in TP were attributable to increasing ST, especially in surface layer. Owing to the frozen ground, the relationship between ST and P is complicated in the area. Higher P also induced higher ST, while the inhibition of freeze and thaw process on the ST in summer. With the increasing AT, P accompanied with the decreasing MFD, MSD should be the major factors induced the conspicuous soil warming of the TP in the past decades.
[en] Accurately estimating the surface fluxes of over the heterogeneous land surface in Tibetan Plateau will be helpful to advance the understanding of its influence on regional climate and hydrology. This paper presents a study on the spatial heterogeneity of land surface parameters in terms of the spatial variability and spatial structure of land surface parameters and the influence on surface fluxes over a typical land surface in Tibetan Plateau. The results suggest that the sensible heat fluxes (H) and latent heat fluxes (LE) in the study area in the rain and dry seasons show apparent spatial variabilities due to the spatial heterogeneity in the leaf area index (LAI) and land surface undulations. The relative frequency distribution of H and LE at the spatial resolution of 30 m suggests that the spatial variability of surface fluxes has a close relationship with the spatial heterogeneity of land surface temperature (LST) and LAI. The variogram analyses of LST, LAI, H, and LE in the study area in rain season indicate that the spatial structures of LST and LAI are different and the spatial structures of H and LE are strongly influenced by the spatial structures of LST and LAI in both rain and dry seasons. The optimal pixel sizes for LST, LAI, H, and LE in the study area are 506, 156, 500, and 225 m in the rain season. The optimal pixel sizes for LST, H, and LE in the study area are 165, 165, and 162 m in the dry season. An analysis of the relative frequency distributions (RFDs) of the LST, LAI, H, and LE at different spatial resolutions in the rain and dry seasons reveals that their values at the maximum relative frequency keep stable although their spatial variabilities become weak as the spatial resolution decreases. The averages of LST, LAI, H, and LE of different spatial resolutions of the study area in rain and dry seasons vary within small ranges, suggesting that the influence of spatial resolution on the averaged land surface parameters and surface fluxes in the study area is small. This work will be helpful for the accurate estimation of the surface fluxes over a large heterogeneous land surface for regional climate modeling in Tibetan Plateau.
[en] Sparse gauge networks in Sub-Saharan Africa (SSA) limit our ability to identify changing precipitation extremes with in situ observations. Given the potential for satellite and satellite-gauge precipitation products to help, we investigate how daily gridded gauge and satellite products compare for seven core climate change precipitation indices. According to a new gauge-only product, the Rainfall Estimates on a Gridded Network (REGEN), there were notable changes in SSA precipitation characteristics between 1950 and 2013 in well-gauged areas. We examine these trends and how these vary for wet, intermediate, and dry areas. For a 31 year period of overlap, we compare REGEN data, other gridded products and three satellite products. Then for 1998–2013, we compare a set of 12 satellite products. Finally, we compare spatial patterns of 1983–2013 trends across all of SSA. Robust 1950–2013 trends indicate that in well-gauged areas extreme events became wetter, particularly in wet areas. Annual totals decreased due to fewer rain days. Between 1983 and 2013 there were positive trends in average precipitation intensity and annual maximum 1 d totals. These trends only represent 15% of SSA, however, and only one tenth of the main wet areas. Unfortunately, gauge and satellite products do not provide consensus for wet area trends. A promising result for identifying regional changes is that numerous satellite products do well at interannual variations in precipitation totals and number of rain days, even as well as some gauge-only products. Products are less accurate for dry spell length and average intensity and least accurate for annual maximum 1 d totals. Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis (3B42-V7) and Climate Hazards center Infrared Precipitation with Stations (CHIRPS v2.0) ranked highest for multiple indices. Several products have seemingly unrealistic trends outside of the well-gauged areas that may be due to influence of non-stationary systematic biases. Social media abstract. Sparse data show increasing Africa rainfall extremes and satellite products fill some missing pieces. (letter)
[en] According to the statistics and collation of data on the main hydrological disasters that occurred in Urumqi from 1949 to 2015, the risk characteristics of the main hydrological disasters in the city are identified and analyzed to reveal the distribution of local hydrological hazard risk based on the comprehensive disaster risk assessment theory for historical disasters. The research findings are as follows: (1) the main hydrological disasters in Urumqi are caused by floods, snow, and droughts, among which floods have the greatest risk, while the risk of droughts is minimal. (2) There are various and complex types of flood disasters in Urumqi, which have frequent occurrences, a wide range of influence, and easily cause secondary disasters. Snow disasters are complex and diverse, with frequent occurrences. Moreover, there are varied and complex types of drought disasters in Urumqi, which have frequent occurrences. Drought disasters in Urumqi, which last for a long time, have enormous effects on agricultural and forestry crops, while the frequencies of frost and hail disasters in Urumqi are lower. (3) Historical hydrological disasters in Urumqi mainly occurred from May to August and November to March of the following year, which are high-frequency months for hydrological disasters. (4) Flood disasters in Urumqi occur every 1.59 years, on average, while snow disasters in Urumqi occur every 1.65 years, on average. Additionally, flood and snow disasters could easily occur in the next 15 years. (5) The hydrological disaster environment in Urumqi is mainly affected by local temperature, sunshine, elevation, topography, precipitation, plant resources, and the social economy.
[en] The extent to which statistical bias-adjusted outputs of two regional climate models alter the projected change signals for the mean (and extreme) rainfall and temperature over the Volta Basin is evaluated. The outputs from two regional climate models in the Coordinated Regional Climate Downscaling Experiment for Africa (CORDEX-Africa) are bias adjusted using the quantile mapping technique. Annual maxima rainfall and temperature with their 10- and 20-year return values for the present (1981–2010) and future (2051–2080) climates are estimated using extreme value analyses. Moderate extremes are evaluated using extreme indices (viz. percentile-based, duration-based, and intensity-based). Bias adjustment of the original (bias-unadjusted) models improves the reproduction of mean rainfall and temperature for the present climate. However, the bias-adjusted models poorly reproduce the 10- and 20-year return values for rainfall and maximum temperature whereas the extreme indices are reproduced satisfactorily for the present climate. Consequently, projected changes in rainfall and temperature extremes were weak. The bias adjustment results in the reduction of the change signals for the mean rainfall while the mean temperature signals are rather magnified. The projected changes for the original mean climate and extremes are not conserved after bias adjustment with the exception of duration-based extreme indices.
[en] A new low-cost L1/L2c receiver board is presented in this short letter, along with its first tests. The main strength of the board is its low price tag (around 200 EUR, in quantities of hundreds) as an effective dual-frequency receiver. The effectiveness of the receiver was at first proven by a pedestrian walk experiment on a closed loop, allowing the evaluation of closure errors. Raw measurements were collected and processed in a real-time scenario through a variometric approach implemented in VADASE software. Epoch-by-epoch velocities were estimated on the basis of dual-frequency phase observations and then the trajectory was reconstructed by numerical integration of the estimated velocities. A horizontal closure error lower than 25 cm was achieved; also, a global assessment of the overall 3D trajectory was carried out, performing a comparison to a standard differential solution with respect to a permanent GNSS station, and standard deviations of the differences between 10 and 20 cm for the 3D components (east, north and up) were achieved. Further, static experiments, both in terms of relative positioning and water vapor monitoring by precise point positioning, confirmed the good performance of the new receiver, with coordinates repeatability of a few millimetres for daily solutions, and estimated water vapor behaviour compatible with local rain events. (paper)
[en] Natural hazards, such as high winds, heavy rains and ice melting, can easily trigger the rockfall which usually leads to great personal injuries and property loss; therefore, the rockfall protection is of great significance and necessity. Among the types of protection, the flexible protection occupies a beneficial condition of application. This paper indicates the basics of flexible protection which includes its classification and advantages, subsequently, analyzing the mechanism of both active protection and passive protection, and then systematically summarizing the research accomplishments, and puts forward the research direction of the flexible protection, including: (1) apart from the traditional rigid protection, the flexible protection has a wide range of advantages, which makes the flexible protection a new and effective protective structure in the rockfall protection; (2) the current researches reveal that though the scholars have done a variety of achievements of flexible protection, there is still a lack of precise simulation of the whole model and local test of the component; (3) putting forward the prospective research direction minutely in both active protection and passive protection.
[en] This paper explores the traditional indicators that small-scale farmers in Gaza province in southern Mozambique use to predict drought events on their rain-fed farms. It analyzes the contextual situation regarding the accuracy and reliability of the traditional prediction methods under the current weather and conditions of climate uncertainty and variability, and the opportunities that their prediction methods can bring to reduce their current and future exposure and vulnerabilities to drought. Farmers use a total of 11 traditional environmental indicators to predict drought, either individually or combined, as required to increase their prediction certainty. However, the farmers perceive that current unpredictability, variability, and changes in weather and climate have negatively affected the interpretation, accuracy, and reliability of most of their prediction indicators, and thus their farming activities and their ability to predict and respond to drought. This, associated with the reduced number of elders in the community, is causing a decline in the diversity, and complexity of interpretation of indicators. Nonetheless, these difficulties have not impeded farmers from continuing to use their preferred prediction methods, as on some occasions they continue to be useful for their farming-related decisions and are also the main, or sometimes only, source of forecast. Considering the role these methods play in farmers’ activities, and the limited access to meteorological forecasts in most rural areas of Mozambique, and the fact that the weather and climate is expected to continually change, this paper concludes that it is important to enhance the use of traditional prediction methods. However, the increase of the accuracy and reliability, and continued existence of the methods depends on the farmers’ own abilities to enhance, preserve, and validate them by tailoring the traditional methods used to work with the new environmental, weather, and climatic conditions, or through the development of new methods.