Length Of Spells Research Articles

Student Loans Under the Risk of Youth Unemployment

While most college graduates eventually find jobs that match their qualifications, the possibility of long spells of unemployment and/or underemployment—combined with ensuing difficulties in repaying student loans—may limit and even dissuade productive investments in human capital. The author explores the optimal design of student loans when young college graduates can be unemployed and reaches three main conclusions. First, the optimal student loan program must incorporate an unemployment compensation mechanism as a key element, even if unemployment probabilities are endogenous and subject to moral hazard. Second, despite the presence of moral hazard, a well-designed student loan program can deliver efficient levels of investments. Dispersion in consumption should be introduced so the labor market potential of any individual, regardless of the family’s financial background, is not impaired as long as the individual is willing to put forth the effort, both during school and afterward, when seeking a job. Third, the amounts of unemployment benefits and the debt repayment schedule should be adjusted with the length of the unemployment spell. As unemployment persists, benefits should decline and repayments should increase to provide the right incentives for young college graduates to seek employment.

Locked In? Noncompete Enforceability and the Mobility and Earnings of High-Tech Workers

We examine how the enforceability of noncompete contracts affects the length of job spells and the level of wages. We expect noncompete enforceability to lengthen job spells, but its impact on wage...

Regional Frequency Analysis of Extreme Dry Spells during Rainy Season in the Wei River Basin, China

Our research analyzes the regional changes of extreme dry spell, represented by the annual maximum dry spell length (noted as AMDSL) during the rainy season in the Wei River Basin (WRB) of China for 1960–2014 using the L-moments method. The mean AMDSL values increase from the west to the east of the WRB, suggesting a high dry risk in the east compared to the west in the WRB. To investigate the regional frequency more reasonably, the WRB is clustered into four homogenous subregions via theK-means method and some subjective adjustments. The goodness-of-fit test shows that the GEV, PE3, and GLO distribution can be accepted as the “best-fit” model for subregions 1 and 4, subregion 2, and subregion 3, respectively. The quantiles of AMDSL under various return levels figure out a similar spatial distribution with mean AMDSL. We also find that the dry risk in subregion 2 and subregion 4 might be higher than that in subregion 1. The relationship between ENSO events and extreme dry spell events in the rainy season with cross wavelet analysis method proves that ENSO events play a critical role in triggering extreme dry events during rainy season in the WRB.

Analyzing the Impacts of on Onset, Length of Growing Period and Dry Spell Length on Chickpea Production in Adaa District (East Showa Zone) of Ethiopia

Agriculture is essential for Ethiopian economy while the concerns of climate change impact on agriculture in developing countries have been increasing and this impact could influence agriculture production in a variety of ways. Rising in temperature and rainfall fluctuation patterns, including the amount of rainfall could adversely affect the productivity of crops. Among the various crops cultivated in the area chickpea productivity is paramount importance. Hence, the study is aimed at characterizing the climate of the study area and its impact on chickpea production. Accordingly, for the purpose of the study, climate, soil and chickpea experimental data (Arerti variety) were collected from Debrezeit Agricultural Research Center. Whereas Mann-Kendall test and Sen’s slope estimator, INISTAT+v.3.37 and Excel 2013 were used for analyzing rainfall and temperature variability including trends. Cropwat 8.0 was used to compute chickpea water requirement. The analysis results showed that the mean annual minimum and maximum temperature were 110°C and 260°C, respectively. While the mean annual total rainfall was about 830 mm with the growing period ranging from 99 to 215 days. The variability in start of the season for the stations was relatively high as compared to the end of the season. Crop water requirement of chickpea doesn’t vary by planting date in the study area and the total water requirement indicated on ranged between 340.6 mm and 346.7 mm during the growing season. Whereas, the effective rainfall which is the most determinant factor for yield is very variable by planting dates.

Drought Hazard Mapping from Regional Climate Multimodel Ensemble over Spain

<p>Improving the knowledge about the impacts of climate change on extreme drought events at basin scale, is important for decision makers in order to develop drought contingency plans which are the leading edge of adaptive management strategy. Considering high-resolution grids of observed daily rainfall and information provided by latest-generation Regional Climate Models (RCMs), the changes in the spatio-temporal patterns of extreme droughts in peninsular Spain are assessed. The non-stationarity character of time series, due to climate and anthropogenic changes, is represented by probabilistic models considering the time evolution of probability density function (PDF) parameters fitted to annual maximum lengths of dry spells time series. By a PDF ensemble from 17 RCMs, the spatio-temporal variability exhibited by the RCMs is represented. Scoring of models is based in the goodness-of-fit to CDFs (cumulative distribution functions) of observed annual maximum dry spells lengths. The reliability and skills of RCMs are assessed, for building the PDF ensemble, at grid site for the study area. Therefore, by adjusting PDF to series of annual maximum dry spells lengths, applying GAMLSS and bootstrapping techniques, the assessment of regional changes and trends associated to high returns periods (<em>Tr</em> = 25 and 50 yr.) is assessed. In general, an intensification of drought events for 2050 horizon, in contrast with 1990, is expected. By increasing return periods, the length of the annual maximum dry spells rises, albeit with a smaller number of areas with significant differences. The areas prone to extreme droughts in mainland Spain are identified.</p>

Trends in precipitation indices at Akola

Climate warming observed over the past several years is consistently associated with changes in a number of components of the hydrological cycle. Precipitation is one of the important component of this cycle. Changes in mean and extreme values of precipitation will impact on rivers, agriculture, environment etc., which may be the serious issue. Therefore predicted trends of precipitation indices can be used to take proper decision for future. In this study the trends in different rainfall indices for the period 1974-2013 were examined for Akola rain gauge station. The meteorological data of rainfall were collected from Agro-Meteorological Observatory, Dr. PDKV Akola. The trends in monthly and annual precipitation indices were calculated statistically and represented graphically. The results showed that there were no significant changes in annual total precipitation within the last few years. In one day maximum rainfall, the decreasing trend was observed during months of monsoon and winter seasons, whereas increasing trends were found during summer months. Maximum number of months showed decreasing trend, especially during monsoon months in respect of consecutive 5days maximum rainfall. The precipitation decrease in August was compensated by a precipitation increase in September. The lengths of wet spells were increased with increase in length of dry spells.

Persistence of Hydrometeorological Droughts in the United Kingdom: A Regional Analysis of Multi-Season Rainfall and River Flow Anomalies

This paper investigates the spatial and temporal properties of persistent meteorological and hydrological droughts in the UK at national to sub-regional scales. Using 1961–1990 as the reference period, it is shown that the longest observed run of below average rainfall since the 1870s persisted for four years in northern England and parts of Scotland during 1892–1896. The longest observed run of below average discharge since the 1950s/1960s was found for some groundwater fed rivers in the English lowlands and lasted up to 5.5 years during 1988–1993. Distributions of dry-spell lengths were represented by a Markov model fit to each rainfall and discharge record. This model provides a good fit to observed geometric distributions of spell lengths and provides credible runs of below average river flows lasting up to a decade in some vulnerable catchments in southern England. Droughts of this persistence may not yet have occurred within the instrumented record but could have profound water management implications for the region. Predicted 100-year drought durations for catchments in northern England may not be as long but could have serious ramifications for surface water supplies. These findings point to a risk of irreversible drought impacts on aquatic communities that are simultaneously stressed by unsustainable abstractions, poor water quality and/or habitat modifications.

Dry spells assessment with reference to the maize crop in the Luvuvhu River catchment of South Africa

Agricultural productivity in South Africa is negatively affected by drought as a result of frequent periodic dry spells and increasing crop water demands resulting in poor crop development and low yields. Thus, we embarked on this study which aims at investigating dry spell occurrences in relation to growing season of maize in the Luvuvhu River Catchment. Daily rainfall data (1945–2014) from 12 stations which represent the catchment fairly well was utilized in this study. Three consecutive planting dates were staggered based on three consecutive onsets of the rainy season. Dry spells were categorized into three groups: short, medium and long dry spells. The data was then subjected to theoretical distribution fitting using the Anderson–Darling goodness-of-fit test; and probabilities of occurrence were computed using a probabilistic model that best fits the data. Trend analysis was performed on the frequency of dry spells per growing period using the non-parametric Spearman's rank correlation test. Out results indicated high probabilities (≥80%) of short dry spells at all the stations irrespective of the timing of planting. Further analysis revealed that a risk of yield reduction with planting following the first onset of rains was higher than that with planting following the second and third onsets. In order to minimize this risk, farmers can be advised to plant between mid-November to mid-December. Trend analysis indicated no trend for all the various dry spell lengths except for Thohoyandou with a decreasing trend and Sigonde with a weak increasing trend in long dry spells. Such findings can be used to describe drought conditions for improvement of agricultural productivity and food security, in a given area.

Forest tree growth response to hydroclimate variability in the southern Appalachians.

Climate change will affect tree species growth and distribution; however, under the same climatic conditions species may differ in their response according to site conditions. We evaluated the climate-driven patterns of growth for six dominant deciduous tree species in the southern Appalachians. We categorized species into two functional groups based on their stomatal regulation and xylem architecture: isohydric, diffuse porous and anisohydric, ring porous. We hypothesized that within the same climatic regime: (i) species-specific differences in growth will be conditional on topographically mediated soil moisture availability; (ii) in extreme drought years, functional groups will have markedly different growth responses; and (iii) multiple hydroclimate variables will have direct and indirect effects on growth for each functional group. We used standardized tree-ring chronologies to examine growth of diffuse-porous (Acer, Liriodendron, and Betula) and ring-porous (Quercus) species vs. on-site climatic data from 1935 to 2003. Quercus species growing on upslope sites had higher basal area increment (BAI) than Quercus species growing on mesic, cove sites; whereas, Acer and Liriodendron had lower BAI on upslope compared to cove sites. Diffuse-porous species were more sensitive to climate than ring porous, especially during extreme drought years. Across functional groups, radial growth was more sensitive to precipitation distribution, such as small storms and dry spell length (DSL), rather than the total amount of precipitation. Based on structural equation modeling, diffuse-porous species on upslope sites were the most sensitive to multiple hydroclimate variables (r(2) =0.46), while ring-porous species on upslope sites were the least sensitive (r(2) =0.32). Spring precipitation, vapor pressure deficit, and summer storms had direct effects on summer AET/P, and summer AET/P, growing season small storms and DSL partially explained growth. Decreasing numbers of small storms and extending the days between rainfall events will result in significant growth reduction, even in regions with relatively high total annual rainfall.

Subsidies promote use of drought tolerant maize varieties despite variable yield performance under smallholder environments in Malawi

This study used a three-year panel dataset for 350 Malawian farm households to examine the potential for widespread adoption of drought tolerant (DT) maize varieties, a technology that holds considerable promise for helping smallholder farmers in Sub-Saharan Africa (SSA) adapt to drought risk. Regression results revealed that DT maize cultivation increased substantially from 2006 to 2012, with the main driver being the Malawi Farm Input Subsidy Program. Recently experienced drought and farmer risk aversion stimulated adoption of DT maize. In yield performance, improved maize varieties performed significantly better than local maize during the 2011/12 drought year. However, DT maize did not perform significantly better than other improved maize varieties used in Malawi, which is in contradiction to results obtained from on-station and on-farm trials. A plausible explanation is that the severe drought in Malawi in the 2011/12 season occurred early in the rainy season and DT maize primarily provides an advantage in the case of late droughts during the silking/grain filling stage of the crop. Preliminary results herein suggest that it was lack of rainfall in December 2011 that constrained maize yield while rainfall in January and February was less limiting. Additionally, the length of the longest dry spells in December and February further strengthens the evidence in favor of this explanation, but further research is needed to reach a conclusion.

Recent changes in Arctic temperature extremes: warm and cold spells during winter and summer

In the Arctic, climate change manifests with the strongest warming trends on the globe, especially in the cold season. It is under debate if climate extremes change similarly strong. Our study provides detailed regional information about two selected temperature extreme indices in the Arctic, namely warm and cold spells in winter and summer. We analyze their temporal evolution and variability from 1979–2013, based on daily station data and ERA-Interim reanalysis. Calculated trends from both datasets suggest a widespread decrease of cold spells in winter and summer of up to −4 days/decade, with regional patches where trends are statistically significant throughout the Arctic. Winter trends are spatially heterogeneous, the reanalysis also shows small areas with statistically significant increases of cold spells throughout Siberia. Calculated changes in warm spells from both datasets are mostly small throughout the Arctic (less than ±1 day/decade) and statistically not significant. Remarkable exceptions are the Lena river basin in winter with a statistically significant decrease of up to −1.5 days/decade and areas in Scandinavia with statistically significant increases of up to 2.5 days/decade in winter and summer (again from both datasets). From the analysis of spell lengths, we find that there are no shifts from longer to shorter spells or vice versa with time, but long cold spells (events lasting for more than 15 days) disappear almost completely after the year 2000. There is a distinct inter-annual and decadal variability in the spells, which hinders the detection of significant trends for all spell categories in all regions.

An evaluation of persistent meteorological drought using a homogeneous Island of Ireland precipitation network

ABSTRACTThis paper investigates the spatial and temporal properties of persistent meteorological droughts using the homogeneous Island of Ireland Precipitation (IIP) network. Relative to a 1961–1990 baseline period it is shown that the longest observed run of below average precipitation since the 1850s lasted up to 5 years (10 half‐year seasons) at sites in southeast and east Ireland, or 3 years across the network as a whole. Dry spell and wet spell length distributions were represented by a first‐order Markov model which yields realistic runs of below average rainfall for individual sites and IIP series. This model shows that there is relatively high likelihood (p = 0.125) of a 5‐year dry spell at Dublin, and that near unbroken dry runs of 10 years or more are conceivable. We suggest that the IIP network and attendant rainfall deficit modelling provide credible data for stress testing water supply and drought plans under extreme conditions.

Assessing Nonstationary Spatial Patterns of Extreme Droughts from Long-Term High-Resolution Observational Dataset on a Semiarid Basin (Spain)

In basins of South-eastern Spain; such as the semiarid Segura River Basin (SRB), a strong decrease in runoff from the end of the 1970s has been observed. However, in the SRB the decreasing trend is not only related with climate variability and change, also with intensive reforestation aimed at halting desertification and erosion, whichever the reason is, the default assumption of stationarity in water resources systems cannot be guaranteed. Therefore there is an important need for improvement in the ability of monitoring and predicting the impacts associated with the change of hydrologic regimes. It is thus necessary to apply non-stationary probabilistic models, which are able to reproduce probability density functions whose parameters vary with time. From a high-resolution daily gridded rainfall dataset of more than five decades (1950−2007), the spatial distribution of lengths of maximum dry spells for several thresholds are assessed, applying Generalized Additive Models for Location Scale and Shape (GAMLSS) models at the grid site. Results reveal an intensification of extreme drought events in some headbasins of the SRB important for water supply. The identification of spatial patterns of drought hazards at basin scale, associated with return periods; contribute to designing strategies of drought contingency preparedness and recovery operations, which are the leading edge of adaptation strategies.

Matching and Winning? The Impact of Upper and Middle Managers on Firm Performance in Major League Baseball

We investigate the joint impact of managers at different hierarchical levels on firm performance in Major League Baseball. We separately quantify the contribution of upper and middle managers and the impact of their match quality—the degree to which managers cooperate effectively across layers to impact firm success. We establish that match quality is a statistically significant and economically meaningful driver of firm performance. Higher-quality managers tend to be matched together across levels and achieve higher match quality during their joint employment. Match quality does not improve over the length of a joint employment spell, but lower match quality is found in pairs with more divergent educational attainment and prior strategic approaches. Hence, match quality is partly innate, and manager pairings may have difficulty improving their cooperation through learning. When we control for match quality, we find significantly lower estimates of heterogeneity in manager ability compared with commonly used estimators of managerial impact. Still, both middle and upper managers retain a meaningful impact on firm performance. This paper was accepted by Bruno Cassiman, business strategy.

Multifractality and autoregressive processes of dry spell lengths in Europe: an approach to their complexity and predictability

Dry spell lengths, DSL, defined as the number of consecutive days with daily rain amounts below a given threshold, may provide relevant information about drought regimes. Taking advantage of a daily pluviometric database covering a great extension of Europe, a detailed analysis of the multifractality of the dry spell regimes is achieved. At the same time, an autoregressive process is applied with the aim of predicting DSL. A set of parameters, namely Hurst exponent, H, estimated from multifractal spectrum, f(α), critical Holder exponent, α 0, for which f(α) reaches its maximum value, spectral width, W, and spectral asymmetry, B, permits a first clustering of European rain gauges in terms of the complexity of their DSL series. This set of parameters also allows distinguishing between time series describing fine- or smooth-structure of the DSL regime by using the complexity index, CI. Results of previous monofractal analyses also permits establishing comparisons between smooth-structures, relatively low correlation dimensions, notable predictive instability and anti-persistence of DSL for European areas, sometimes submitted to long droughts. Relationships are also found between the CI and the mean absolute deviation, MAD, and the optimum autoregressive order, OAO, of an ARIMA(p,d,0) autoregressive process applied to the DSL series. The detailed analysis of the discrepancies between empiric and predicted DSL underlines the uncertainty over predictability of long DSL, particularly for the Mediterranean region.

Climate extremes in multi-model simulations of stratospheric aerosol and marine cloud brightening climate engineering

Abstract. Simulations from a multi-model ensemble for the RCP4.5 climate change scenario for the 21st century, and for two solar radiation management (SRM) schemes (stratospheric sulfate injection (G3), SULF and marine cloud brightening by sea salt emission SALT) have been analysed in terms of changes in the mean and extremes of surface air temperature and precipitation. The climate engineering and termination periods are investigated. During the climate engineering period, both schemes, as intended, offset temperature increases by about 60 % globally, but are more effective in the low latitudes and exhibit some residual warming in the Arctic (especially in the case of SALT which is only applied in the low latitudes). In both climate engineering scenarios, extreme temperature changes are similar to the mean temperature changes over much of the globe. The exceptions are the mid- and high latitudes in the Northern Hemisphere, where high temperatures (90th percentile of the distribution) of the climate engineering period compared to RCP4.5 control period rise less than the mean, and cold temperatures (10th percentile), much more than the mean. This aspect of the SRM schemes is also reflected in simulated reduction in the frost day frequency of occurrence for both schemes. However, summer day frequency of occurrence increases less in the SALT experiment than the SULF experiment, especially over the tropics. Precipitation extremes in the two SRM scenarios act differently – the SULF experiment more effectively mitigates extreme precipitation increases over land compared to the SALT experiment. A reduction in dry spell occurrence over land is observed in the SALT experiment. The SULF experiment has a slight increase in the length of dry spells. A strong termination effect is found for the two climate engineering schemes, with large temperature increases especially in the Arctic. Globally, SULF is more effective in reducing extreme temperature increases over land than SALT. Extreme precipitation increases over land is also more reduced in SULF than the SALT experiment. However, globally SALT decreases the frequency of dry spell length and reduces the occurrence of hot days compared to SULF.

Youth Unemployment After Apprenticeship Training and Individual, Occupation, and Training Employer Characteristics

SummaryThis paper analyses the risk of unemployment, unemployment duration, and the risk of longterm unemployment immediately after apprenticeship graduation. Unemployed apprenticeship graduates constitute a large share of unemployed youth in Germany but unemployment incidence within this group is unequally distributed. Our paper extends previous research in three dimensions. It shows that (i) individual productivity assessment of the training firm, (ii) initial selection into high reputation training firms and occupations, and (iii) adverse selection of employer moving graduates are correlated with unemployment after apprenticeship graduation. The empirical evidence is obtained from the second longitudinal version of the linked employer-employee panel data from the IAB (LIAB). This large data set allows us to calculate the exact unemployment spell length of apprenticeship graduates. In addition, we can include individual, employer, occupation as well as industrial relation characteristics before and after apprenticeship graduation into our list of explanatory variables for unemployment risk. We show in several robustness checks that our results are remarkably stable when we vary the employees included in the sample, the definition of unemployment, and the list of explanatory variables.

Statistical downscaling of meteorological time series and climatic projections in a watershed in Turkey

In this study, meteorological time series from five meteorological stations in and around a watershed in Turkey were used in the statistical downscaling of global climate model results to be used for future projections. Two general circulation models (GCMs), Canadian Climate Center (CGCM3.1(T63)) and Met Office Hadley Centre (2012) (HadCM3) models, were used with three Special Report Emission Scenarios, A1B, A2, and B2. The statistical downscaling model SDSM was used for the downscaling. The downscaled ensembles were put to validation with GCM predictors against observations using nonparametric statistical tests. The two most important meteorological variables, temperature and precipitation, passed validation statistics, and partial validation was achieved with other time series relevant in hydrological studies, namely, cloudiness, relative humidity, and wind velocity. Heat waves, number of dry days, length of dry and wet spells, and maximum precipitation were derived from the primary time series as annual series. The change in monthly predictor sets used in constructing the multiple regression equations for downscaling was examined over the watershed and over the months in a year. Projections between 1962 and 2100 showed that temperatures and dryness indicators show increasing trends while precipitation, relative humidity, and cloudiness tend to decrease. The spatial changes over the watershed and monthly temporal changes revealed that the western parts of the watershed where water is produced for subsequent downstream use will get drier than the rest and the precipitation distribution over the year will shift. Temperatures showed increasing trends over the whole watershed unparalleled with another period in history. The results emphasize the necessity of mitigation efforts to combat climate change on local and global scales and the introduction of adaptation strategies for the region under study which was shown to be vulnerable to climate change.

A Longitudinal Causal Analysis of Impact Made by Collaborative Engagement and Service Receipt on Likelihood of Substantiated Re-Report.

In a temporal-ordering causal analysis, we explored impacts of parent's receipt of services and caseworker-parent collaborative engagement on substantiated child maltreatment re-report. Our sample of 2,368 parents came from the National Survey of Child and Adolescent Well-Being. Using generalized estimating equations, we found likelihood of substantiated re-report to drop significantly in association with collaborative engagement, length of current in-home spell, and family income. In turn, parental alcohol dependence, initial substantiated sexual maltreatment, and prior in-home spells were linked to increased likelihood. Practice implications are discussed.

Daily rainfall data to identify trends in rainfall amount and rainfall-induced agricultural events in the Nuba Mountains of Sudan

Widely variable inter- and intra-seasonal rainfall increases risks of agricultural production in the Nuba Mountains of Sudan, which are one of the country's most vulnerable areas with respect to climate change. This study aims to identify trends in rainfall amount at different temporal resolutions as well as changes and probabilities of rainfall-induced agricultural events. Long-term daily rainfall records (60 years) from two weather stations, Kadugli and Rashad, were computed to daily, monthly and annual values and rainfall-induced events were computed using the INSTAT + software. Subsequently, these calculated values and events were checked for possible monotonic trends from 1950 to 2009 and 1970 to 2009 by Mann–Kendall tests.Over the period from 1970 to 2009, annual rainfall showed no statistically significant change for either station. However, during this period an increase of low rainfall events (>0.85 mm to ≤3 mm) by 15 days coinciding with a decline in the number of medium daily rainfall classes (>10 mm to ≤20 mm) by 4 days was observed in Rashad. This increase is of concern since low rainfall events do not contribute to the crop water balance and therefore may thus be largely irrelevant for rainfed farmers' crop production. Furthermore, daily rainfall data enabled frequency calculations of a successful or failed start of the growing season, of high intensity rainfall events (90th, 95th and 99th percentiles) and of different dry spell length classes (>7, >14 and >21 days; 1 to ≤7 days, 8 to ≤14, 15 to ≤21 and >21). Additionally, probability calculations of the minimum lengths of growing season and the occurring of dry spell lengths based on specific dates were conducted. Since for these rainfall-induced agricultural events either no statistically significant changes or trends resulting only in minor changes of probabilities were observed, our risk statements seem to be reliable for the next years. The results of this study may contribute to a better assessment of crop management risks under rainfed farming in the Nuba Mountains.