We have studied the spatiotemporal characteristics of ozone concentration over Ethiopia using Ozone Mapper and Profiling Suite (OMPS) Satellite measurements. Daily total column ozone measurements of 252 data points with spatial resolution 1 ◦ × 1 ◦ for the study area and its surrounding during the period 2012 – 2020 have been analyzed. We investigated the spatial variation over the region from longitudinal and latitudinal bands separately by assessing existence of mean difference among different bands using multicomparison analysis of variance technique and determined the clusters in the region. For the temporal variability, we employed timeseries analysis and decomposed the ozone concentration series for each class into seasonal, trend and residual components. We have found that the total column ozone concentration has a maximum value of 301DU during summer on August 18, 2013 and a minimum value of 216DU during winter on February 03, 2013 over the study period. The 95% confidence level of the overall mean of total column ozone concentration during the study period was found to be (261 . 28 ± 4 . 2)DU . Our spatial data analysis revealed that the spatial distribution of ozone over Ethiopia can be classified into three major regions: Southern Cluster (4 . 5 ◦ N − 8 . 5 ◦ N & 32 . 5 ◦ E − 47 . 5 ◦ E ) , North–Eastern Cluster (9 . 5 ◦ N to 14 . 5 ◦ N & 41 . 5 ◦ E − 47 . 5 ◦ E ) and North–Western Cluster (9 . 5 ◦ N − 14 . 5 ◦ N & 32 . 5 ◦ E − 40 . 5 ◦ E ). We also checked the degree of determination among bands in same cluster to see if the concentration of ozone in one band can be explained by the concentration in a another band for each cluster and confirmed the reliability of the classification. From the timeseries analysis, we made an assessment of spectral periodogram for each cluster and obtained a single Fourier power peak with frequency of f = 0 . 002768 Hz , which indicated that the ozone concentration has an annual cyclic behavior in the region. A truncated Fourier series fit is made to determine the annual seasonal component. The non-parametric Mann-Kendall’s trend test with a 95% confidence level of significant indicated a decreasing linear trend with a depletion rate of 0.77 DU/yr, 0.73 DU/yr, and 0.43 DU/yr over North–Western, North–Eastern & Southern clusters respectively. The analysis of residuals result for each cluster indicated that the standardized residuals are normally distributed and white noises. Hence, the model considered is reliable.
The fourth version of the International Center for Theoretical Physics (ICTP) Regional Climate Model (RegCM4) model is evaluated for its performance over Upper Blue Nile River Basin Region (UBNRBR). The model rainfall captured the observed spatial and temporal variability of rainfall over the basin during the spring (MAM) and summer (JJA) seasons. The simulation dataset is generated using the RegCM4 for the period 1982-2009. The UBNRBR is first divided into 14 homogeneous regions using criteria including Rotated Empirical Orthogonal Function (REOF), spatial correlation and topographical features. Spatially averaged observed and simulated rainfall time series are then generated and analyzed for each region. Standardized rainfall anomalies of the observations and the simulated data are highly correlated over most of central regions, while a weak correlation is found over the east border regions of the basin. The dominant modes of rainfall variability are identified using REOF. The first leading patterns of rainfall and upper wind (averaged between 100 and 300 hpa) are highly correlated and exhibit similar features between simulated and observed dataset over the basin. Similarly, the first loading pattern of low level wind (averaged between 850 and 1000 hpa) exhibits a dipole structure across the southwestern and southeastern regions of the UBNRBR. The correlations with significant rotated principal components (RPCs) across gridded gauge, and model rainfall fields with that of low-and upper level winds show the presence of significant relationship (correlation exceeding ~0.6). Overall, that the RegCM4 shows a good performance in simulating the spatial and temporal variability of precipitation over UBNRBR.
The Upper Blue Nile river basin (uBN) is vital to three countries' water, food, and energy security (Ethiopia, Sudan, and Egypt). It is also a region with substantial interannual precipitation variability and the potential for significant climate change in coming decades. The El Niño-Southern Oscillation (ENSO) affects both variability and trends in uBN precipitation, with El Niño episodes historically connected with below-average rainfall. In this context, this study seeks to: (a) examine the representation of ENSO-uBN rainfall teleconnections in simulations from the sixth Coupled Model Intercomparison Project (CMIP6), as compared to the previous generation of models (CMIP5); (b) distinguish between teleconnections during the peak of the rainy season (July-August [JA]) and the agriculturally critical end-of-season rains (September-October [SO]); (c) investigate evidence for Tropical Easterly Jet (TEJ) mediation of these teleconnections in CMIP6 versus CMIP5 and for both peak rains and end of the rainy season. Using a subset of high performing models, we find that CMIP6 simulations of uBN precipitation show somewhat less bias than CMIP5 for JA total rainfall, and that correlations with ENSO have become more consistent across models, but that differences between CMIP5 and CMIP6 are modest.CMIP6 simulations, like CMIP5, overestimate SO rainfall and suggest a stronger ENSO association in SO than is indicated by observations. Model representation of the TEJ and its association with both ENSO and uBN precipitation show no systematic change between CMIP5 and CMIP6. The mediating influence of the TEJ appears to be more important in JA than SO.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.