Special Issue "African Rainfall Variability: Science and Society"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Meteorology".

Deadline for manuscript submissions: closed (31 October 2018).

Special Issue Editors

Prof. Dr. Rosalind Cornforth
Website
Guest Editor
The Walker Institute, University of Reading, Earley Gate, Reading, RG6 6BB, UK
Interests: improving understanding of the fundamental dynamics of African weather systems and downstream tropical cyclogenesis; developing user-centred integrated climate early warning systems, based on the Rainwatch AfClix monitoring/prediction platform; African rainfall variability and predictability of extreme precipitation events; knowledge Exchange and experiential learning for managing climate resilience; governance and decision-making for climate change adaptation
Dr. Aondover Tarhule
Website
Guest Editor
State University of New York (SUNY) at Binghamton, Couper Administration Building (AD), Room 134, The Graduate School, 4400 Vestal Parkway East, Binghamton, NY 13902,USA
Interests: hydrology; water resources,;stochastic hydrology; physical geography; water scarcity
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Special Issue Information

Dear Colleagues,

The Sahel-Soudano zone that spans North Africa, from Senegal to Ethiopia, has experienced pronounced climatic variability (and conflicts) for millennia. This home to 250 million people—one quarter of Africa’s population—is a fragile transition zone in environmental and human terms. From south-to-north, rainfall decreases from around 30 inches per year on average to essentially nothing. Back-to-back contrasting rain years (deficits in 2011, floods in 2012) left over 18 million people in the West African Sahel threatened by food shortages between 2012 and 2013, highlighting yet again the strong the dependence between livelihoods on rainfall in the region. Ironically (tragically, even), the stakeholders within the Sahel have less access to, and therefore use less, instrumental rainfall information for planning and management than almost anywhere else in the world. Furthermore, short-term weather and seasonal climate forecasting have limited skill for West Africa. Whilst many of the National Hydrological and Meteorological agencies are making impressive efforts to produce tailored climate forecasts for their stakeholders, most appear to be country specific.

Recognizing these constraints, this Special Issue presents the latest understanding of African rainfall variability and on-going efforts to translate this into useable information through knowledge co-production and dissemination, to assure content relevance and accuracy for intended purposes. Stakeholders must establish practical innovations to anticipate impending crises and work collaboratively across the region to share information and strengthen supporting infrastructure. Within this framework, timely access to user-relevant climate information, access to relevant and reliable forecasts, and the ability of stakeholders to act on that information through effective strategic partnerships will prove the difference between coping proactively with emerging climate challenges and perpetuating the cycle of climate triggers and crisis.

Prof. Dr. Rosalind Cornforth
Prof. Dr. Aondover Tarhule
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (4 papers)

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Research

Open AccessArticle
Projected Changes in Intra-Season Rainfall Characteristics in the Niger River Basin, West Africa
Atmosphere 2018, 9(12), 497; https://doi.org/10.3390/atmos9120497 - 14 Dec 2018
Cited by 3 | Viewed by 1858
Abstract
The magnitude and timing of seasonal rainfall is vitally important to the health and vitality of key agro-ecological and social-economic systems of the Niger River Basin. Given this unique context, knowledge concerning how climate change is likely to impact future rainfall characteristics and [...] Read more.
The magnitude and timing of seasonal rainfall is vitally important to the health and vitality of key agro-ecological and social-economic systems of the Niger River Basin. Given this unique context, knowledge concerning how climate change is likely to impact future rainfall characteristics and patterns is critically needed for adaptation and mitigation planning. Using nine ensemble bias-corrected climate model projection results under RCP4.5 and RCP8.5 (RCP—Representative Concentration Pathway) emissions scenarios at the mid-future time period, 2021/2025-2050 from the Coordinated Regional Climate Downscaling Experiments (CORDEX) dataset; this study provides a comprehensive analysis of the projected changes in rainfall characteristics in three agro-ecological zones of the Niger River Basin. The results show an increase in the average rainfall of about 5%, 10–20% and 10–15% for the Southern Guinea, Northern Guinea and Sahelian zones, respectively, relative to the baseline, 1981/1985–2005. On the other hand, the change in future rainfall intensities are largely significant and the frequency of rainfall at the low, heavy and extreme rainfall events in the future decrease at most locations in the Niger River Basin. The results also showed an increase in the frequency of moderate rainfall events at all locations in the basin. However, in the Northern Guinea and Sahel locations, there is an increase in the frequency of projected heavy and extreme rainfall events. The results reveal a shift in the future onset/cessation and a shortening of the duration of the rainy season in the basin. Specifically, the mean date of rainfall onset will be delayed by between 10 and 32 days. The mean onset of cessation will also be delayed by between 10 and 21 days. It is posited that the projected rainfall changes pose serious risks for food security of the region and may require changes in the cropping patterns and management. Full article
(This article belongs to the Special Issue African Rainfall Variability: Science and Society)
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Open AccessArticle
Downscaling Atmosphere-Ocean Global Climate Model Precipitation Simulations over Africa Using Bias-Corrected Lateral and Lower Boundary Conditions
Atmosphere 2018, 9(12), 493; https://doi.org/10.3390/atmos9120493 - 12 Dec 2018
Cited by 3 | Viewed by 1273
Abstract
A prequel study showed that dynamic downscaling using a regional climate model (RCM) over Africa improved the Goddard Institute for Space Studies Atmosphere-Ocean Global Climate Model (GISS AOGCM: ModelE) simulation of June–September rainfall patterns over Africa. The current study applies bias corrections to [...] Read more.
A prequel study showed that dynamic downscaling using a regional climate model (RCM) over Africa improved the Goddard Institute for Space Studies Atmosphere-Ocean Global Climate Model (GISS AOGCM: ModelE) simulation of June–September rainfall patterns over Africa. The current study applies bias corrections to the lateral and lower boundary data from the AOGCM driving the RCM, based on the comparison of a 30-year simulation to the actual climate. The analysis examines the horizontal pattern of June–September total accumulated precipitation, the time versus latitude evolution of zonal mean West Africa (WA) precipitation (showing monsoon onset timing), and the latitude versus altitude cross-section of zonal winds over WA (showing the African Easterly Jet and the Tropical Easterly Jet). The study shows that correcting for excessively warm AOGCM Atlantic sea-surface temperatures (SSTs) improves the simulation of key features, whereas applying 30-year mean bias corrections to atmospheric variables driving the RCM at the lateral boundaries does not improve the RCM simulations. We suggest that AOGCM climate projections for Africa should benefit from downscaling by nesting an RCM that has demonstrated skill in simulating African climate, driven with bias-corrected SST. Full article
(This article belongs to the Special Issue African Rainfall Variability: Science and Society)
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Open AccessArticle
Space-Time Variability of the Rainfall over Sahel: Observation of a Latitudinal Sharp Transition of the Statistical Properties
Atmosphere 2018, 9(12), 482; https://doi.org/10.3390/atmos9120482 - 07 Dec 2018
Cited by 1 | Viewed by 1040
Abstract
The rain statistics of 0–45° N area including equatorial, Sahelian, and mid-latitude regions, are studied using the probability distributions of the duration of rainy and dry events. Long time daily data set from ground measurements and satellite observations of rain fields are used. [...] Read more.
The rain statistics of 0–45° N area including equatorial, Sahelian, and mid-latitude regions, are studied using the probability distributions of the duration of rainy and dry events. Long time daily data set from ground measurements and satellite observations of rain fields are used. This technique highlights a sharp latitudinal transition of the statistics between equatorial and all other regions (Sahel, mid-latitude). The probability distribution of the 8° S to 8° N latitude band shows a large-scale organization with a slow decreasing (power law decrease) distributions for the time and space size of rain events. This observation is in agreement with a scaling, or macro turbulent, behavior of the equatorial regions rain fields. For the Sahelian and mid-latitude regions, our observations are clearly not in agreement with this behavior. They show that the largest rain systems have a limited time and space size (well described with a decreasing exponential distribution). For these non-equatorial regions it is possible to define a local characteristic duration and a characteristic horizontal size of the large rain events. These characteristics time and space scales of observed mesoscale convective systems could be a sensible indicator for the detection of the possible trend of rain distribution properties due to anthropogenic influence. Full article
(This article belongs to the Special Issue African Rainfall Variability: Science and Society)
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Open AccessArticle
Extreme Rainfall and Flooding over Central Kenya Including Nairobi City during the Long-Rains Season 2018: Causes, Predictability, and Potential for Early Warning and Actions
Atmosphere 2018, 9(12), 472; https://doi.org/10.3390/atmos9120472 - 30 Nov 2018
Cited by 14 | Viewed by 3741
Abstract
The Long-Rains wet season of March–May (MAM) over Kenya in 2018 was one of the wettest on record. This paper examines the nature, causes, impacts, and predictability of the rainfall events, and considers the implications for flood risk management. The exceptionally high monthly [...] Read more.
The Long-Rains wet season of March–May (MAM) over Kenya in 2018 was one of the wettest on record. This paper examines the nature, causes, impacts, and predictability of the rainfall events, and considers the implications for flood risk management. The exceptionally high monthly rainfall totals in March and April resulted from several multi-day heavy rainfall episodes, rather than from distinct extreme daily events. Three intra-seasonal rainfall events in particular resulted in extensive flooding with the loss of lives and livelihoods, a significant displacement of people, major disruption to essential services, and damage to infrastructure. The rainfall events appear to be associated with the combined effects of active Madden–Julian Oscillation (MJO) events in MJO phases 2–4, and at shorter timescales, tropical cyclone events over the southwest Indian Ocean. These combine to drive an anomalous westerly low-level circulation over Kenya and the surrounding region, which likely leads to moisture convergence and enhanced convection. We assessed how predictable such events over a range of forecast lead times. Long-lead seasonal forecast products for MAM 2018 showed little indication of an enhanced likelihood of heavy rain over most of Kenya, which is consistent with the low predictability of MAM Long-Rains at seasonal lead times. At shorter lead times of a few weeks, the seasonal and extended-range forecasts provided a clear signal of extreme rainfall, which is likely associated with skill in MJO prediction. Short lead weather forecasts from multiple models also highlighted enhanced risk. The flood response actions during the MAM 2018 events are reviewed. Implications of our results for forecasting and flood preparedness systems include: (i) Potential exists for the integration of sub-seasonal and short-term weather prediction to support flood risk management and preparedness action in Kenya, notwithstanding the particular challenge of forecasting at small scales. (ii) We suggest that forecasting agencies provide greater clarity on the difference in potentially useful forecast lead times between the two wet seasons in Kenya and East Africa. For the MAM Long-Rains, the utility of sub-seasonal to short-term forecasts should be emphasized; while at seasonal timescales, skill is currently low, and there is the challenge of exploiting new research identifying the primary drivers of variability. In contrast, greater seasonal predictability of the Short-Rains in the October–December season means that greater potential exists for early warning and preparedness over longer lead times. (iii) There is a need for well-developed and functional forecast-based action systems for heavy rain and flood risk management in Kenya, especially with the relatively short windows for anticipatory action during MAM. Full article
(This article belongs to the Special Issue African Rainfall Variability: Science and Society)
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