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The objective of this study was to evaluate the performance of satellite rainfall estimates (Climate Hazards Group Infrared Precipitation with Stations version 2 (CHIRPSv2) and Multi-Source Weighted-Ensemble Precipitation version 2 (MSWEPv2) from 1981 to 2018 for monthly meteorological drought analysis over the Upper Blue Nile (UBN) basin. The reference for the performance evaluation was rainfall measured in situ selected with reference to the elevation zones of the basin: Highland, midland, and lowland. Both the measured and estimated rainfall datasets were aggregated by month at a spatial resolution of 10 km × 10 km with a temporal coverage of 38 years from 1981 to 2018 and evaluated with respect to raw precipitation statistics and the standardized precipitation index (SPI). The values of SPI were validated with reference to documented meteorological drought records of the country. The mean bias, correlation coefficient, probability of bias (PBias, %), mean error (ME, mm), and root mean square error (RMSE, mm) values across the elevation zones for CHIRPSv2 were found to be 1.07, 0.91, 6.75, 7.74, and 122.34, respectively. The corresponding values were 1.19, 0.87, 18.56, 19.54, and 130.26 for MSWEPv2. Based on this result, CHIRPSv2 was employed to analyze the magnitude of drought in the different elevation zones of the UBN. The magnitude (SPI) of monthly meteorological drought over the entire UBN basin from 1981 to 2018 ranged from 0 to −3.74. The strongest negative SPI value (−3.74) was observed in August 1984 in midland areas. The highest magnitude of drought was −3.0 in July 2015 over the highland and −3.03 in June 2015 over the lowland during 2014–2017. The observed drought was characterized by extreme, severe, and moderate levels. The mean frequency of severe/extreme meteorological drought in the 38-year period over the highland, midland, and lowland parts of the UBN ranged from 7% to 11%. The average of severe/extreme drought events in each of the elevation zones of the basin was 9%, that is, drought occurred almost every 10 years for all elevation zones of the basin. Over the 38-year period, severe/extreme drought occurred at the onset and/or offset time of rainy season over all elevation zones of the basin. The UBN is characterized as a drought-prone basin. However, the frequency and magnitude of drought could neither be described as a decreasing nor as an increasing linear trend. Thus, the farming practices in the basin need to be enhanced with an improved early warning system and drought-resistant seed technologies. [ABSTRACT FROM AUTHOR]

Many regions in Africa and the Middle East are vulnerable to drought and to water and food insecurity, motivating agency efforts such as the U.S. Agency for International Development's (USAID) Famine Early Warning Systems Network (FEWS NET) to provide early warning of drought events in the region. Each year these warnings guide life-saving assistance that reaches millions of people. A new NASA multimodel, remote sensing-based hydrological forecasting and analysis system, NHyFAS, has been developed to support such efforts by improving the FEWS NET's current early warning capabilities. NHyFAS derives its skill from two sources: (i) accurate initial conditions, as produced by an offline land modeling system through the application and/or assimilation of various satellite data (precipitation, soil moisture, and terrestrial water storage), and (ii) meteorological forcing data during the forecast period as produced by a state-of-the-art ocean-land-atmosphere forecast system. The land modeling framework used is the Land Information System (LIS), which employs a suite of land surface models, allowing multimodel ensembles and multiple data assimilation strategies to better estimate land surface conditions. An evaluation of NHyFAS shows that its 1-5-month hindcasts successfully capture known historic drought events, and it has improved skill over benchmark-type hindcasts. The system also benefits from strong collaboration with end-user partners in Africa and the Middle East, who provide insights on strategies to formulate and communicate early warning indicators to water and food security communities. The additional lead time provided by this system will increase the speed, accuracy, and efficacy of humanitarian disaster relief, helping to save lives and livelihoods. [ABSTRACT FROM AUTHOR]

For at least four decades, archaeologists have identified irrigation as playing a potentially major role in the rise of Aksumite civilization. Based on a systematic survey covering the area between Aksum and Yeha (Ethiopia), Joseph Michels proposed that large-scale irrigation systems introduced from Southwest Arabia contributed to the rise of Yeha as a major center of Pre-Aksumite civilization. To evaluate spatial patterning of archaeological sites with respect to water availability, this paper reports on results from archaeological survey of a 100 km2 region surrounding Yeha conducted by the Southern Red Sea Archaeological Histories (SRSAH) Project from 2009 to 2016. The SRSAH Project recorded 84 sites dating from the Pre-Aksumite to the Post-Aksumite periods (c.800 BCE to 900 CE). No ancient irrigation systems were identified and results do not show a correlation between archaeological sites and water resources. This suggests that irrigation was less important than Michels contended and that rainfed agriculture, terraces, and small-scale irrigation comparable with practices evident in the region today were sufficient to sustain ancient populations. [ABSTRACT FROM AUTHOR]

The association between elevation (agro-climatic zones, ACZs) and the mean annual total rainfall (MATRF) is not straightforward in different parts of the world. This study sought to estimate the amount of MATRF across four elevation zones of Jema watershed, which is situated in the northwestern highlands of Ethiopia, by employing an appropriate interpolation method. The elevation of the watershed ranges from 1895 to 3518 m a.s.l. For the sake of this study, 34 sample MATRF data were extracted from satellite and nearby gauge stations that were recorded from 1983 to 2010. These data sources were reconstructed by International Research Institute for Climate and Society at Columbia University, USA, at a scale of 10 km by 10 km. An elevation data set generated from a digital elevation model with 30-m resolution (DEM 30 m) was considered as a covariable to estimate the MATRF. To identify the optimal interpolation model, mean errors were computed using cross-validation statistics. The root-mean-square error (RMSE) analysis showed that ordinary cokriging (OCK) was the most accurate model with a predictive power of 87.3%. The root-mean-square standardized (RMSSE) analysis showed that the best precision value (0.72) occurred in OCK. Stable and Gaussian trend lines together with local polynomial types of trend removal, and an elliptical neighborhood search function could perform best to maximize the accuracy and the precision of estimating MATRF. Elevation, as a covariable, enhanced the degree of accuracy and precision of estimation. The value of the trend line function (least square) between the MATRF and elevation was very weak (R2 = 0.07), whereas the value of trend line function (least square) between the MATRF and the longitude coordinates (east–west direction) was medium (R2 = 0.34). The estimated MATRF for the entire watershed under study ranged from 1228 to 1640 mm. To conclude, elevation could contribute to the estimation of the MATRF. The value of the MATRF showed a declining pattern from the lower to higher elevation areas of the watershed. [ABSTRACT FROM AUTHOR]

Objective: This study investigated whether using thermometers clipped on workers' shoes would result in different heat exposure estimation and work-rest schedules compared with using area-level meteorological data alone. Methods: Alabama workers (n = 51) were individually monitored using thermometers on shoes. Wet bulb globe temperature (WBGT) was estimated using thermometer temperatures (WBGT [personal]) or nearby weather station temperatures (WBGT [WS]). Work-rest schedules were determined from WBGT, clothing, and hourly metabolic rates estimated from self-reported tasks and bodyweight. Results: The percent of hours exceeding the threshold limit value (TLV®, ACGIH, Cincinnati, OH) were estimated at 47.8% using WBGT (personal) versus 42.1% using WBGT (WS). For work-rest recommendations, more hours fell into the most protective schedule (0 to 15 min work/45 to 60 min rest) using WBGT (personal) versus WBGT (WS) (17.4% vs 14.4%). Conclusions: Temperatures from wearable thermometers, together with meteorological data, can serve as an additional method to identify occupational heat stress exposure and recommend work-rest schedules. [ABSTRACT FROM AUTHOR]

BACKGROUND: Environmental heat exposure is a public health concern. The impacts of environmental heat on mortality and morbidity at the population scale are well documented, but little is known about specific exposures that individuals experience. OBJECTIVES: The first objective of this work was to catalyze discussion of the role of personal heat exposure information in research and risk assessment. The second objective was to provide guidance regarding the operationalization of personal heat exposure research methods. DISCUSSION: We define personal heat exposure as realized contact between a person and an indoor or outdoor environment that poses a risk of increases in body core temperature and/or perceived discomfort. Personal heat exposure can be measured directly with wearable monitors or estimated indirectly through the combination of time-activity and meteorological data sets. Complementary information to understand individual-scale drivers of behavior, susceptibility, and health and comfort outcomes can be collected from additional monitors, surveys, interviews, ethnographic approaches, and additional social and health data sets. Personal exposure research can help reveal the extent of exposure misclassification that occurs when individual exposure to heat is estimated using ambient temperature measured at fixed sites and can provide insights for epidemiological risk assessment concerning extreme heat. CONCLUSIONS: Personal heat exposure research provides more valid and precise insights into how often people encounter heat conditions and when, where, to whom, and why these encounters occur. Published literature on personal heat exposure is limited to date, but existing studies point to opportunities to inform public health practice regarding extreme heat, particularly where fine-scale precision is needed to reduce health consequences of heat exposure. [ABSTRACT FROM AUTHOR]

The article focuses on the U.S. National Aeronautics and Space Administration (NASA's) Precipitation Measurement Missions (PMM). NASA determines the success and relevance of its missions by understanding and quantifying how the data are applied within different communities of end users, including national weather and hydrology agencies.

Human disturbances of waterways in Ethiopian highlands have increased throughout the last century due to population growth and increased land use. Despite this, there is a lack of knowledge on macroinvertebrate responses to human disturbances and the application of biological monitoring in tropical highland waterways in general. In this study, we have evaluated the human impact on the ecological integrity of the Chemoga River catchment in the Choke mountain watershed in the northwestern region of the Ethiopian Blue Nile highlands. During wet and dry seasons the water quality and macroinvertebrate assemblages were assessed. Multivariate statistics and Canonical Correspondence Analysis (CCA) were used to identify factors influencing macroinvertebrate community structures in highland streams in the northwest regions of Ethiopia. A total of 66 taxa of benthic macroinvertebrates were recorded, among which Diptera (38%) and Coleoptera (21%) were the most dominant. The results revealed a severe decrease in the ecological integrity of the Chemoga River in terms of macroinvertebrate composition at higher altitude. The ordination and cluster analysis clearly indicates extremely low macroinvertebrate diversity at sites where human impact is severe and a strong effect of altitude. These results highlight the need to protect the highland waterways of the Blue Nile area and that of similarly degraded watersheds in the Ethiopian highlands. [ABSTRACT FROM AUTHOR]

With support from NASA's Modeling and Analysis Program, we have recently developed the NASA Unified-Weather Research and Forecasting model (NU-WRF). NU-WRF is an observation-driven integrated modeling system that represents aerosol, cloud, precipitation and land processes at satellite-resolved scales. “Satellite-resolved” scales (roughly 1–25 km), bridge the continuum between local (microscale), regional (mesoscale) and global (synoptic) processes. NU-WRF is a superset of the National Center for Atmospheric Research (NCAR) Advanced Research WRF (ARW) dynamical core model, achieved by fully integrating the GSFC Land Information System (LIS, already coupled to WRF), the WRF/Chem enabled version of the GOddard Chemistry Aerosols Radiation Transport (GOCART) model, the Goddard Satellite Data Simulation Unit (G-SDSU), and custom boundary/initial condition preprocessors into a single software release, with source code available by agreement with NASA/GSFC. Full coupling between aerosol, cloud, precipitation and land processes is critical for predicting local and regional water and energy cycles. [ABSTRACT FROM AUTHOR]

Abstract: In dynamic coastal systems such as the Chesapeake Bay, limited coverage and frequency of in situ measurements often makes generalizability of regional forecasting systems difficult. Satellite-derived environmental variables have the potential to address this problem, but satellite datasets suffer from incomplete coverage as well: atmospheric conditions—most notably cloud cover—lead to data gaps that significantly hinder the broad application of satellite-informed predictions. In this study, the Chesapeake Bay estuary was used as a model “test bed” to which we applied the power of near real-time satellite-derived observations to the issue of water quality monitoring. To use remote sensing in support of spatially complete estimates of salinity and temperature in the Bay, we tested geospatial interpolation techniques as a method for filling gaps and minimizing errors in the satellite record. These interpolated values were then compared to the output of a regional hydrodynamic model in order to assess the relative value of each method for generating inputs into various modeling applications. Results show that MODIS-derived salinity and temperature can be interpolated with acceptable accuracy in the Bay, with a mean absolute error of 1.88psu and 0.60°C. These errors differed systematically from ChesROMS errors both spatially and seasonally, with higher errors for salinity and lower errors for temperature at most sampling stations throughout the year. This suggests that the two techniques offer complementary information that can be applied to ecological monitoring systems in complex estuaries like Chesapeake Bay. [Copyright &y& Elsevier]

A nine-year (2010–2018) field study in the Debre Mawi watershed was conducted to understand the effect of governmentally-imposed and farmer-initiated conservation practices. The watershed is in the sub-humid Ethiopian Highlands which experience high and increasing erosion rates despite years of conservation efforts. Consequently, reservoirs are filling up with sediment and soil degradation is enhanced, calling for the evaluation of conservation practices currently in use. The few past long-term experimental studies on structural practices are inconclusive. In addition, only anecdotal information is available for streamflow and sediment loss. Precipitation, stream discharge, and suspended sediment concentrations were recorded manually in the Debre Mawi watershed during the nine-year period. Groundwater depth and total saturated area measurements were taken for selected periods. From 2012 to 2014, government-mandated conservation practices were constructed, which consisted of 50-cm-deep infiltration furrows with bunds downslope. These furrows were filled in with sediment by 2018. At the same time, the acreage of eucalyptus trees planted by farmers on the most vulnerable lands tripled to 5% of the total area with most trees fully grown in 2018. Runoff coefficients and sediment concentrations decreased steadily throughout the nine years. In the saturated bottomlands, the observations suggested that government-sponsored infiltration furrows in the saturated bottomlands were ineffective and may concentrate flows and enhance gully erosion, while eucalyptus trees appear effective. The results of this observational study point to both the potential benefits of conservation practices in this sub-humid tropical highland region and to emerging long-term risks. If structural conservation is to be pursued in watersheds like Debre Mawi, due attention must be given to the safe removal of excess water from the valley bottoms. The vegetative farmer-initiated practice of planting eucalyptus trees effectively reduced streamflow and erosion, but at the same time, might dry up wells during the dry monsoon phase which should be investigated further. Image 1 • Acreage of eucalyptus planted by farmers increased three-fold in nine years. • Observed runoff and sediment yield declined with increased acreage of eucalytus. • Dry phase eucalyptus evaporation delayed saturation excess runoff in rain phase. • Infiltration furrows were not maintained, filled up, and appeared ineffective. • Groundwater irrigation is feasible when lava dikes block subsurface downhill flow. [ABSTRACT FROM AUTHOR]

• Our precipitation isotope data shows the need for high-frequency spatial sampling. • Daily δ18O precip values decrease by >8‰ synchronously at 3 stations in August 2013. • The northwestern highland stations show similar seasonal trends in δ18O precip. • Seasonality of δ18O precip at Jijiga is less distinct than in northwest highlands. • Storm intensity and convection likely explain seasonal isotope variations. Stable isotopes of oxygen (δ18O) and deuterium (δ2H) in precipitation are used as tracers of the hydrologic cycle in studies of both past and present climate. In Ethiopia, a drought sensitive region where direct observations of climate are limited, understanding the stable isotopic composition of precipitation can provide an integrated view of the hydroclimate today and help interpret records of climate variability in the past. To date, the isotopic composition of precipitation in Ethiopia is known primarily from monthly precipitation collections from one long-term monitoring station in Addis Ababa. Here we report δ18O and δ2H values of precipitation from a 16-month long sampling campaign at four stations in Ethiopia that represent different climate regimes. Precipitation samples collected at daily, weekly and monthly intervals between August 2012 and November 2013 at these stations exhibit a large range of δ18O (−12.6 to +10.3‰), δ2H (−91.8‰ to +80.8‰), and d-excess values (−9.9‰ to +29.9‰). The four stations have similar amount-weighted mean δ18O values, but exhibit different seasonal patterns in δ18O values as clearly shown in daily and weekly data. The most striking feature of this dataset is the synchronous decrease in δ18O values in daily and weekly precipitation samples from the three stations in the northwestern highlands (Gondar, Debre Markos, Jimma) during the first three weeks of August 2013. This decrease in δ18O values does not correlate strongly to precipitation amount but it is likely due to a combination of increased storm intensity and deep convection at the time of lower δ18O values of precipitation. Our high-resolution dataset provides new insights into the controls on the isotopic composition of rainfall in Ethiopia and how we might use it to understand hydroclimate variability today and in the past. [ABSTRACT FROM AUTHOR]