Seasonal Changes In Rainfall Research Articles

Do Longer Dry Spells Associated With Warmer Years Compound the Stress on Global Water Resources?

AbstractAvailability of water resources is significantly affected by changes in seasonal rainfall, with water often in short supply when most needed. The majority of current research focuses on the impacts of multiyear drought, using monthly or annual average rainfall to investigate impacts to water resources. Here, we use daily rainfall to evaluate changes in dry spells lengths, defined as the continuous number of days without rain, and investigate how these changes may impart stresses on water resources in warmer summer seasons globally. We use over 100 years of precipitation and temperature data across the world, arranged into warm and cold groups of years on the basis of mean summer temperature. These warm and cold groups are then compared to demonstrate an overwhelming tendency for warmer summers to contain longer dry spells globally. This difference in dry spell length in warmer summer seasons is argued to have far reaching ramifications in warmer summers. For some of the largest cities in the world, vulnerability of water resources, which is a measure of the magnitude or severity of the water availability deficit, is shown to be on average 30% higher due to longer seasonal dry spells in warmer summers. Such an impact points to a need to reassess water resources plans and policies to include the impacts of seasonal dry spells, especially relating to large urban populations around the world.

Nonstationary Runoff Responses Can Interact With Climate Change to Increase Severe Outcomes for Freshwater Ecology

AbstractClimate change is projected to impact multiple components of the flow regime. However, changes in some ecologically important aspects of flow seasonality and variability are not well‐represented by global climate models. We used a stress testing method and global sensitivity analysis to investigate whether interactions between five different, but plausible, change “dimensions” (hydroclimatic variables or relationships) led to worse ecological outcomes than individual changes. The five dimensions include changes in long‐term average rainfall and temperature, low‐frequency variability of rainfall, seasonality of rainfall, and the rainfall‐runoff relationship. Our case study involved regulated and unregulated sections of the Goulburn River, Australia. We found that four different modeled ecological outcomes (condition of small bodied fish, large bodied fish, in‐channel vegetation, and floodplain vegetation) are most sensitive to changes in long‐term average rainfall. Sensitivity to changes in rainfall seasonality depends on river characteristics and appears to be heavily dampened by regulation and actively managed environmental water. Changes to the rainfall‐runoff relationship (which may be triggered by long‐term drying) were found to greatly influence ecological outcomes, but remain poorly understood. However, when considering the worst outcomes that are likely to present severe threats to ecological survival, all five dimensions were significant. These worst outcomes only manifest under certain combinations of changes with interactive effects. These joint interactions have implications for climate risk assessments that do not consider multiple dimensions of change, particularly those aimed at evaluating and mitigating severe threats or extinction probability.

Changes in rainfall seasonality inferred from weathering and pedogenic trends in mid-Miocene paleosols of La Tatacoa, Colombia

The authigenic clay mineral assemblage of paleosol profiles and trends in their bulk geochemical evolution provide insight into the intensity of past chemical weathering regimes. These climate-sensitive weathering products can be used to interpret regional changes of the soil moisture regime, which in turn reflects upon the nature of rainfall seasonality (e.g., unimodal vs. bimodal). A conspicuous color change in the overbank deposits and paleosols of the mid-Miocene Honda Group of La Tatacoa, Colombia, is suggestive of a climatic transition which affected the fauna of La Venta - a mid-Miocene fossiliferous site and significant component of the South American Land Mammal Age (SALMA) classification. This study aims to determine how the paleopedology of this region records the climatic transition that modified the annual patterns of rainfall and soil moisture, forcing a change from the gray-colored paleosols hosted by the La Victoria Formation (~13.6 to ~13.1 Myr) to the red-beds of the Villavieja Formation (~13.1 to 12.0 Myr). In the La Victoria profile, the pedogenic fraction of the clay assemblage indicates that vermiculite, chlorite/HIV mixed-layered clays and high concentrations of base cations (Ca2+, Mg2+, Na+) developed in a poorly drained paleosol under reducing (low Eh) and above-neutral pH conditions. By contrast, the presence of kaolinite, goethite and hematite in the red-beds paleosols implies more oxidizing conditions (high Eh), whereas pedogenic vermiculite and smectite suggest a pH close to or mildly below neutral. A common detrital source (parent material) is inferred for both sets of paleosols. However, more intense chemical weathering towards aluminium rich clay in the Villavieja red-bed fossil soils indicates a change in soil humidity from a poorly drained soil environment of a seasonally flooded wetland system to an alternating regime of humidity and drought on a better drained floodplain. The variation in soil moisture is consistent with a change in seasonality from a unimodal rainfall regime in the case of the La Victoria paleosols to bimodal conditions in the case of the paleosols of the Villavieja Fm. After the establishment of a fully glaciated Antarctica and the global climate transition into the Mi-4 glacial stage at ~13.1 Ma, an increased rate of continental weathering along the paleotropical fringe could have been caused by a stronger temperature gradient between the equator and South Pole, shifting the Intertropical Convergence Zone northward and the rainfall patterns with it.

Adaptation strategies for rainfed rice water management under climate change in Songkhram River Basin, Thailand

Abstract This study investigates the potential impacts of climate change on water resources and evaluates adaptation strategies on rainfed rice water management under climate change scenarios in the Songkhram River Basin, Thailand. The Soil and Water Assessment Tool (SWAT) model was used to project the future water availability under climate change scenarios for the period of 2020–2044. Future annual water availability is expected to remain unchanged due to unchanged future rainfall but expected to reduce from June to November due to changes in seasonal rainfall. The effects of supplying irrigation water to reduce the impact of climate change and increase rainfed rice production were evaluated. To increase the rice production by 15%, it is proposed to construct a reservoir with a capacity of below 65 MCM in each of the 15 sub-basins to fulfill the irrigation water requirements during the rainfed rice season. Alternatively, adaptation at the farm scale can be implemented by constructing ponds with a capacity of 900 m3 to store water for 1 ha of rice field to meet the potential rice yield during the non-rainfed rice season. The results of this study are helpful to policymakers in understanding the potential impacts of climate change and the formulation of adaptation strategies for water and rice sectors in the basin.

Investigating changes in rainfall seasonality across South Africa: 1987–2016

AbstractChanges in rainfall seasonality across South Africa may have detrimental impacts on crop yields and surface water supplies. Despite this, these have rarely been investigated across the South African summer‐, winter‐ and year‐round rainfall zones (SRZ, WRZ and YRZ respectively) using consistent methods. Rainfall seasonality changes are explored here using daily rainfall and temperature records for 1987–2016 from 46 meteorological stations spanning a grid across South Africa. Focusing on comparable methods that statistically define the SRZ, WRZ, YRZ, we apply a ratio of monthly rainfall: temperature and a percentile‐based wet‐season start‐ and end‐date metric, which each provide annual outputs of the degree of seasonality, and the timing, duration, magnitude and intensity of wet‐season rainfall. Although relatively few statistically significant trends are detected, some regional spatial patterns are evident. Trends for most locations across the southwestern Cape and western coast are indicative of a decrease in the strength of seasonality with a reduction in winter wet‐season rainfall, and are broadly consistent with observed and projected poleward dynamics of the southern hemisphere subtropical high‐pressure belt and mid‐latitude westerlies. Trends towards later wet‐season start‐dates together with a reduction in summer wet‐season rainfall amount are prominent across most of the interior and northeastern locations, and may be linked to Hadley cell expansion recorded in recent decades. Along the southern coast, trends towards an increase in the degree of seasonality together with a shorter wet‐season, concentrated around the winter months, are evident. If sustained, the trends quantified present a concerning outlook for continued crop production and water resource management, and thus warrant further investigations on rainfall seasonality shifts and the drivers thereof across southern Africa.

High-resolution stable isotope profiles of modern elephant (Loxodonta africana) tusk dentin and tail hair from Kenya: Implications for identifying seasonal variability in climate, ecology, and diet in ancient proboscideans

Stable isotope ratios in tissues of large mammalian herbivores record diet and climate information integrated over large spatial areas and can be used to study modern and fossil ecosystems. Sound interpretation of data requires that tissue growth rates be determined accurately and that ecological and behavioral variables that influence stable isotope ratios of tissues be measured and related to experienced environmental conditions assessed through field observations, remote sensing data, and meteorological records. If well-understood in modern herbivores, stable isotopes from closely-related extinct taxa have tremendous potential for resolving paleodiet, paleoenvironment, and paleoclimate of terrestrial ecosystems. We present multiyear, high-resolution (i.e., weekly) stable isotope records from bioapatite in tusk dentin (δ13Cdentin and δ18Odentin) and tail hair (δ13Chair and δ15Nhair) of an African elephant (Loxodonta africana) from Kenya that was fitted with a GPS collar intermittently over a five year period and observed for nearly a decade. GPS and observational data provide behavioral, life history, and location information. Normalized Difference Vegetation Index (NDVI), precipitation, and isotopic data from plants and water provide further constraints for interpreting isotope profiles. We determine tusk and hair growth rates using a combination of histological and geochemical approaches, including bomb-curve radiocarbon, that confirm approximately weekly resolution in the stable isotope profiles. Tusk dentin isotope profiles spanning the periods 1982 to 1987 and 2000 to 2006 record weekly variability in δ13Cdentin, where increases of up to 4.5‰ from baseline values due to diet switches from predominantly C3 browsing to mixed C3 browsing and C4 grazing occur during the twice-yearly (biannual) rainy seasons. The δ13Chair values show a similar trend. The δ13C profiles served as a proxy for seasonal changes in rainfall, vegetation, and diet. The δ18O of tusk bioapatite varied approximately biannually up to 5‰, likely reflecting increases in the proportion of plant water ingested during the wet season. Using a least squares inverse filter, we show that NDVI can be used to predict δ13C of dentin and vice versa, offering the possibility to reconstruct seasonal changes in vegetation and rainfall in the geologic past. Our results demonstrate that high-resolution tusk isotope profiles serve as a proxy for seasonality of diet and precipitation, and thus can be used to reconstruct aspects of elephant life history, vegetation, and climate at unprecedented resolution from modern and fossil proboscidean samples.

SUSLE: a slope and seasonal rainfall-based RUSLE model for regional quantitative prediction of soil erosion

The Revised Universal Soil Loss Equation (RUSLE) models are most widely used for quantitative prediction of soil erosion. However, these models have many shortcomings. For example, the annual total rainfall is often adopted, ignoring the inhomogeneity of seasonal rainfall. The adopted vegetation coverage indexes (VCIs) are usually the annual average vegetation coverage or VCIs obtained by monitoring on a specific day, ignoring the seasonal changes in VCIs during the year. In addition, the impact of slope on the conservation practices factor is not considered. To overcome these problem, this study aims to propose a seasonal and slope factor-based RUSLE (SUSLE) model that considers the seasonal changes in rainfall and VCIs and the effect of slope on the conservation practices factor. Based on GIS and remote sensing, the quantitative prediction of soil erosion in Ningdu County, Jiangxi Province, in 2017 is taken as a case study. The traditional RUSLE model and the proposed SUSLE model are analyzed and compared. Results show that the overall distribution characteristics of soil erosion in the two models are similar that the SUSLE model is more consistent than the RUSLE model in all erosion levels and that the prediction performances of the SUSLE model in the very low, moderate, and high erosion levels are better than those of the RUSLE model. The distribution characteristics of soil erosion in different periods and the relationships between soil erosion and environmental factors (e.g., slope and land use) under the SUSLE model are discussed. The results show that the maximum erosion area occurred in spring and the minimum area in autumn; the soil erosion amount on slopes of 8~25° reached 65.14% of the total amount; bare grassland and cultivated land are the main land cover types impacted by soil erosion in Ningdu County.

Assessing the impact of seasonal-rainfall anomalies on catchment-scale water balance components

Abstract. Although water balance components at the catchment scale are strongly related to annual rainfall, the availability of water resources in Mediterranean catchments also depends on rainfall seasonality. Observed seasonal anomalies in historical records are fairly episodic, but an increase in their frequency might exacerbate water deficit or water excess if the rainy season shortens or extends its duration, e.g., due to climate change. This study evaluates the sensitivity of water yield, evapotranspiration, and groundwater recharge to changes in rainfall seasonality by using the Soil Water Assessment Tool (SWAT) model applied to the upper Alento River catchment (UARC) in southern Italy, where a long time series of daily rainfall is available from 1920 to 2018. We compare two distinct approaches: (i) a “static” approach, where three seasonal features (namely rainy, dry, and transition fixed-duration 4-month seasons) are identified through the standardized precipitation index (SPI) and (ii) a “dynamic” approach based on a stochastic framework, where the duration of two seasons (rainy and dry seasons) varies from year to year according to a probability distribution. Seasonal anomalies occur when the transition season is replaced by the rainy or dry season in the first approach and when season duration occurs in the tails of its normal distribution in the second approach. Results are presented within a probabilistic framework. We also show that the Budyko curve is sensitive to the rainfall seasonality regime in UARC by questioning the implicit assumption of a temporal steady state between annual average dryness and the evaporative index. Although the duration of the rainy season does not exert a major control on water balance, we were able to identify season-dependent regression equations linking water yield to the dryness index in the rainy season.

Assessing the impacts of climate change on aerobic rice production using the DSSAT-CERES-Rice model

AbstractThis study assessed the impacts of climate change on aerobic rice production using the DSSAT-CERES-Rice model. Actual data observed from four cropping seasons in two sites were used for calibration and validation. Four Representative Concentration Pathway scenarios were used to simulate climate change. The optimum planting windows were simulated across these scenarios. Results showed that DSSAT-CERES-Rice could adequately simulate aerobic rice production. Changes in seasonal rainfall and increases in temperature especially during dry seasons adversely affected aerobic rice production. Reduction of rainfall during the wet seasons favored aerobic rice production. Yield losses are twice as large as gains. Changes in climate could cause yield improvements to decline from 83% to 53% and yield reductions to increase from 150% to 177% towards the end of the 21st century. Selecting the best planting windows could optimize production to avoid huge economic losses. Optimum planting windows were simulated during normal, dry, and wet climate conditions. The derived set of genetic coefficients could be used to assess various aerobic rice farm crop and nutrient management strategies as well as other climate and soil conditions. The long-term projections on aerobic rice production could guide policy and decision-makers on designing long-term climate change adaptation and mitigation plans and programs.

Rainfall as a driver of seasonality in parasitism

Parasite burdens are known to vary seasonally in wildlife, and rainfall is one key aspect of seasonality that has been linked to parasitism in a range of systems. Rainfall can have immediate effects on parasitism rates by affecting parasite survival and movement in the environment, or it can have delayed effects by affecting host susceptibility to parasites through changes in host body condition or immune function. In this study, we examined how helminth infection in a wild ungulate (Grant's gazelle, Nanger granti) is impacted by seasonal changes in rainfall. We looked at how the burdens of three helminth parasites varied in relation to current (immediate effect) and prior (delayed effect) rainfall by comparing parasite fecal egg and larval counts to rainfall 0, 1, and 2 months prior to parasite sampling. We found burdens of all three parasites to be negatively associated with rainfall, and that delayed effects were stronger than immediate effects. Our findings implicate rainfall as a driver of seasonal variation in infection and suggest one important mechanism may be through delayed effects on host susceptibility.

Smallholder Farmers\u2019 perception and adaptation to climate variability and change in Fincha sub-basin of the Upper Blue Nile River Basin of Ethiopia

Climate variability and change make agricultural sector a risky venture for smallholders’ farmers. This paper presents an assessment of smallholder farmers’ perceptions of climate variability and change, associated impacts on agricultural sector and the adaptive responses given in Fincha’a sub-basin of the Blue Nile River Basin of Ethiopia. We interviewed 380 head of households selected through systematic random sampling from eight Kebeles, two each from highland, midland, wetland, and lowland agro-ecosystems. Furthermore, focus group discussion and key informant interviews also performed to supplement and substantiate the quantitative data. Descriptive statistics used to summarize quantitative data and χ2 tests used to measure significance. The result revealed that increased temperature, frequency and severity of extreme weather events (drought and flood), and overall change in seasonality of rainfall over the last 20 years is a widely held perception. The associated impacts on agriculture include decline in length of growing period, the decreased and variability of water availability, increased crop damage by insects, pests, disease and weeds. In response, farmers practiced different adaptation measures like modification in crop and livestock production practices, and investment in land and water management activities at household and community level. The study also revealed the presence of multiple barriers that hindered the adoption of adaptation measures. To meet the impending challenges, situate by climate variability and change the adaptation measures implemented until now is not adequate. There is also extrication between farmers’ perceptions of climate variability and change, and actual adaptation level. Despite significant number of farmers’ perceived changes in temperature (about 93%) and rainfall (about 88%), the number of farmers adopted certain adaptation measures are below average. These necessitate the need for planned interventions to identify and support effective adaptation measures.

Reproductive activity patterns of four species of Cinnamomum in Purwodadi Botanic Garden

The aims of this study were to know flowering and fruiting pattern of the four Cinnamomum and their response in relation to seasonal change in rainfall, temperature and air humidity in Purwodadi Botanic Garden. The vegetative and reproductive activities were observed once per week based on the abundance of leaves, flowers and fruits using a scoring method from 0-4, for 6-8 years of observations. The rainfall per month, temperature, and humidity were simultaneously recorded. Data were analysed by Principal Component Analyses to determine the microclimate variables that have correlation to the reproductive activity patterns of all four species. Most species started flower budding during Juni – August, except C. burmanii which produced flowers 2-3 times per year in small quantity. Flowering of C. burmanii showed positively correlations with rainfall intensity, while flowering the other three species did not relate to microclimate in PBG. Six dry months preceding a long dry season in 2015 caused C. burmanii did not produce flowers and fruits.

Climatological seasonal changes of wind and rainfall in the Philippines

AbstractClimatological seasonal changes of rainfall and lower tropospheric circulation in and around the Philippines are analysed by utilizing the TRMM 3B42 to obtain the 5‐day mean rainfall and ERA‐Interim wind data for the period 1998–2013. In particular, climatological onset and withdrawal processes of the southwest (SW) and northeast (NE) monsoon are investigated. It is found that the onset of the SW monsoon occurs abruptly in mid‐May almost simultaneously over the Philippines except in the southern region. The start of the SW monsoon in the Philippines occurs earlier in the north than in the south. In addition, a climatological increase in rainfall on the west coast precedes the SW monsoon arrival by approximately two pentads, due to tropical cyclone influences in some years. After the SW monsoon onset, the monsoon trough is located over the southern Philippines. In mid‐June, the monsoon trough begins to deepen, and migrates northward to the central Philippines, and easterly winds intrude shortly to the northern Philippines. Then, the entire Philippines is covered by the summer monsoon westerly in early July, which is followed by the rainfall peak over the west coast region occurring in early August. The SW monsoon begins to retreat from the north in mid‐September, and fully retreats from the Philippines rather suddenly in late September. In general, the rainfall amount in the west coastal region remains high for approximately 2 months after this wind reversal, showing relatively larger post monsoon rainfall due mainly to tropical cyclone effects. During the NE monsoon season, the rainfall centre in the east coast is located in the northern and central region until mid‐December. Afterwards it is anchored in the southern region from late December to mid‐March, indicating the fully established NE monsoon season.

Resolving seasonal rainfall changes in the Middle East during the last interglacial period

Paleorainfall proxy records from the Middle East have revealed remarkable patterns of variability since the penultimate glacial period (140 ka), but the seasonality of this signal has been unresolvable. Here, seasonal-resolution oxygen isotope data from Soreq Cave speleothems suggest that summer monsoon rainfall periodically reaches as far north as Israel-well removed from the modern monsoon-at times (∼125, 105 ka) that overlap with evidence for some of the earliest modern human migrations out of Africa. These seasonal proxy data are corroborated by seasonal-resolution model output of the amount and oxygen-isotope ratio of rainfall from an isotope-enabled climate model. In contrast to the modern regional climate where rainfall is delivered predominantly in winter months along westerly storm tracks, the model suggests that during extreme peaks of summer insolation-as occurs during the last interglacial (e.g., 125, 105 ka)-regional rainfall increases due to both wetter winters and the incursion of summer monsoons. This interpretation brings clarity to regional paleoproxy records and provides important environmental context along one potential pathway of early modern human migration.

Evaluation of district-level rainfall characteristics over Odisha using high-resolution gridded dataset (1901–2013)

In the present global warming era, exploring the regional/district-level changes in rainfall patterns/events is highly essential for understanding the diverse characteristics of rainfall, which will be value added for the policy planning for rainfed agricultural-based states like Odisha, a region that is also highly prone to flood and droughts. Since most of the global and continental scale climate studies rarely contribute for such planning of agro-economic states of India like Odisha, there is a colossal necessity for the analysis of rainfall characteristics at regional/district level. In the present study, the rainfall characteristics at district level over Odisha are extensively evaluated for winter (JF), pre-monsoon (MAM), monsoon (JJAS) and post-monsoon (OND) using India Meteorological Department high-resolution gridded rainfall analysis dataset for the period 1901–2013. The El Nino Southern Oscillation (ENSO) influence on the district-level seasonal rainfall during four distinctive seasons has also been studied. The results suggest that the frequency of various categorical rainfall events and associated seasonal rainfall patterns over Odisha is highly heterogeneous and varies from season to season in magnitude and similar statements can be highlighted for inter-annual variability and coefficient of variation. Although the seasonal rainfall time series is significantly persistent in most of the districts during all the seasons, it is manifested to the normal distribution in majority of districts only for JJAS. Statistical analysis infers that most of the districts possess reasonable abrupt changes in seasonal rainfall during mid- and late twentieth century. A significant increasing (decreasing) trend in the frequency of high-intensity (low-intensity and wet days) rainfall events over most parts of Odisha is observed for all the seasons. A notable decreasing trend in seasonal rainfall is perceived over southern districts during MAM (7–21 mm) and OND (23–49 mm), western districts during MAM (2–41 mm) and JJAS (6–309 mm) and most of the districts during JF (6–46 mm), while increasing trend is prominent over coastal and northern Odisha during MAM (7–46 mm), northern coastal Odisha during JJAS (25–175 mm), northern and northern coastal Odisha during OND (2–64 mm). It has been noticed that the ENSO influence on seasonal rainfall is insignificant during summer monsoon, while it is notable during the other seasons. This study is very useful in determining the effects and assists the risk management for various sectors in acclimating innovative technologies for a sustainable future in the present global warming era.

Assessing the impacts of climate change on dependable flow and potential irrigable area using the SWAT model. The case of Maasin River watershed in Laguna, Philippines

Seasonal changes in rainfall and temperature brought about by climate change affect water resources availability for rice production areas. There are currently no published applications of the soil and water assessment tool (SWAT) model on quantified effects of climate variability on irrigation service areas for rice production. The study assessed the impacts of climate change on dependable flow and potential irrigable areas of the Maasin River in Laguna, Philippines. Projected variations of rainfall and temperature in 2020 and 2050 developed using PRECIS model based on special report on emission scenarios were employed. The SWAT model was then used to simulate stream flow for each climate change scenario, from which dependable flows were quantified using flow duration analysis. Diversion water requirements for the rice areas in the watershed were determined using CROPWAT. Based on dependable flows and irrigation demand, the potential irrigable areas were estimated. Calibration and validation of the SWAT model showed satisfactory performance in stream flow simulations. The dependable flow in irrigation systems may decline by more than 50% in 2020 and by as much as 97% in 2050, because of seasonal changes in rainfall. In effect, the potential irrigable area may decrease to less than half of the current service area depending on the level of greenhouse gases emissions. SWAT water balance projections suggest surface runoff during wet seasons and increase annual groundwater recharge are possible sources of supplemental irrigation. Provisions of suitable storage reservoir facilities and groundwater development projects will alleviate water scarce conditions. The study demonstrated a technique that may be applied in other irrigation systems in the Philippines and in other countries to quantify the effects of climate change on dependable flows and potential irrigable areas. It can serve as an input to water resources planning and policy recommendations for climate change adaptation and risk reduction strategies. This technique can also be used to assess water resources in other perennial rivers and its viability for the development of new irrigation systems in the Philippines.

English

Climate change and variability threatens food security globally making life uncertain mostly for agro-pastoral communities in semi-arid areas. This has necessitated exploration of designed pathways with potentials to increase resilience among agro-pastoralists. This work investigates agro-pastoralists’ innovative pathways for enhancing resilience to the impacts of climate change and variability in Kiteto and Kilindi districts. Mixed method research approach under correlation case study design was employed. Primary data were collected using household survey which sampled 384 households, Focus group discussion (n=6), in-depth interviews (key informants) and field visits. Descriptive statistics and thematic analysis were used in analyzing and presenting the findings. Majority of the respondents (81%) noted a decline and changes in seasonal rainfall and amount and increase in temperature trends (91.4%) in their areas for the past 30 years linked to reduced livestock production and cereals and pulses crop yields. These findings corroborate that from the Tanzania meteorological data (TMA). About 91.1% of the respondents said the major impacts of climate change and variability are decline in grazing/pasture lands, cultivated lands and water resources causing decreasing number of their livestock and crop productivity, ultimately food insecurity for a decade. To increase resilience, agro-pastoralists developed different innovative pathways, though most are similar. The main innovated pathways were livestock seasonal mobility, construction of traditional water points (Njoro), traditional grazing management system through traditional by-laws for pastures conservation/rotational use, growing of droughts-resistant mixed crops, Maasai traditional constructed water reservoirs (Mboutu), reducing stock numbers by selling, drought-tolerant forage species(cactus plants for Animal’s fodder), keeping mixtures of herds and women transporting water by donkeys from traditional wells/Njoro. Government and other stakeholders are called upon to improve agro-pastoralists’ adaptive capacity and increase households’ food security status in the study areas.   Key words: Agro-pastoralist, climate change, climate variability, pathways, Njoro, Mboutu, Alalili, lopolol, Kiteto District, Kilindi District.

Differentiated responses of nonstructural carbohydrate allocation to climatic dryness and drought events in the Inner Asian arid timberline

Isolated patchy forests in the arid timberline of Inner Asia are facing increasing risk of forest mortality with increasing drought frequency. The allocation of nonstructural carbohydrates (NSC) helps forests adapt to increasing drought. Previous studies that focused on site-level observations of NSC responses to changes in seasonal rainfall suggested that NSC in branches and stems showed no difference under different levels of drought stress. We conducted large-scale sampling of Larix sibirica-dominated forest patches of different sizes at 7 sites with different mean annual precipitation (MAP) in northern Mongolia in August 2017. Results showed that MAP determines the leaf and stem soluble sugar (SS), leaf and branch starch concentrations of Larix sibirica. The branch stores more starch at lower MAP. A comparison of seasonal NSC dynamics between wetter and dryer sites in the arid timberline of northern China shows that starch in stems is significantly higher for both Pinus sylvestris var. mongolica and Betula platyphylla at drier sites in the dry year 2017 than the normal year 2016. Our two lines of evidence suggest that the enhanced shoot starch allocation is an immediate response of trees to drought, rather than an adaptation strategy to regional climate dryness, although a spatial pattern may exist.

A MCDM-based framework for selection of general circulation models and projection of spatio-temporal rainfall changes: A case study of Nigeria

A multi-criteria decision-making approach was used for the selection of GCMs for Nigeria based on their ability to replicate historical rainfall estimated using three entropy-based feature selection methods namely, Entropy Gain (EG), Gain Ratio (GR), and Symmetrical Uncertainty (SU). Performances of four bias correction methods were compared to identify the most suitable method for downscaling and projection of rainfall using the selected GCMs. Random forest (RF) regression was used for the generation of the multi-model ensemble (MME) average of projected rainfall. The ensemble projections for each of the representative concentration pathways (RCPs) 2.6, 4.5, 6.0, and 8.5 were computed and compared with global precipitation climatology centre (GPCC) historical rainfall of Nigeria to assess the percentage changes in annual rainfall with 95% level of confidence at different ecological zones for three future periods 2010–2039, 2040–2069, and 2070–2099. Quantile regression was used to assess the changes in seasonal rainfall at 95% confidence interval over the present century. The results revealed that MRI-CGCM3, HadGEM2-ES, CSIRO-Mk3-6-0 and CESM1-CAM5 are the most suitable GCMs for the projection of rainfall in Nigeria. The linear scaling method was found as the most suitable approach for downscaling of rainfall in terms of all the statistical indices used. It was found to downscale rainfall with normalized root mean square error (NRMSE) in the range of 30.7–44.0%, while Nash-Sutcliff efficiency (NSE) was between 0.81 and 0.91, and modified coefficient of agreement (md) was between 0.82 and 0.88. Projection of rainfall showed no significant change in Nigeria over the century under RCP 2.6, 4.5 and 6.5, while RCP 8.5 showed a decrease in the last part of the century (2070–2099). The seasonal changes in rainfall showed an increase in rainfall in the range of 0–20% in most parts of the north. The methodology in this study can reduce the uncertainty inherent in climate change projection and produce better projection of possible spatial and temporal changes in annual and seasonal rainfall.

Uncertainty in Estimated Trends Using Gridded Rainfall Data: A Case Study of Bangladesh

This study assessed the uncertainty in the spatial pattern of rainfall trends in six widely used monthly gridded rainfall datasets for 1979–2010. Bangladesh is considered as the case study area where changes in rainfall are the highest concern due to global warming-induced climate change. The evaluation was based on the ability of the gridded data to estimate the spatial patterns of the magnitude and significance of annual and seasonal rainfall trends estimated using Mann–Kendall (MK) and modified MK (mMK) tests at 34 gauges. A set of statistical indices including Kling–Gupta efficiency, modified index of agreement (md), skill score (SS), and Jaccard similarity index (JSI) were used. The results showed a large variation in the spatial patterns of rainfall trends obtained using different gridded datasets. Global Precipitation Climatology Centre (GPCC) data was found to be the most suitable rainfall data for the assessment of annual and seasonal rainfall trends in Bangladesh which showed a JSI, md, and SS of 22%, 0.61, and 0.73, respectively, when compared with the observed annual trend. Assessment of long-term trend in rainfall (1901–2017) using mMK test revealed no change in annual rainfall and changes in seasonal rainfall only at a few grid points in Bangladesh over the last century.