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  1. Article: Playing the long game: Anticipatory action based on seasonal forecasts

    MacLeod, David / Kniveton, Dominic R. / Todd, Martin C.

    Climate risk management. 2021, v. 34

    2021  

    Abstract: Acting in advance of floods, drought and cyclones often requires decision-makers to work with weather forecasts. The inherently probabilistic nature of these forecasts can be problematic when deciding whether to act or not. Cost-loss analysis has ... ...

    Abstract Acting in advance of floods, drought and cyclones often requires decision-makers to work with weather forecasts. The inherently probabilistic nature of these forecasts can be problematic when deciding whether to act or not. Cost-loss analysis has previously been employed to support forecast based decision-making such as Forecast-based Financing (FbF), providing insight to when an FbF system has ‘potential economic value’ relative to a no-forecast alternative. One well-known limitation of cost-loss analysis is the difficulty of estimating losses (which vary with hazard magnitude and extent, and with the dynamics of population vulnerability and exposure). A less-explored limitation is ignorance of the temporal dynamics (sequencing) of costs and losses. That is, even if the potential economic value of a forecast system is high, the stochastic nature of the atmosphere and the probabilistic nature of forecasts could conspire over the first few forecasts to increase the expense of using the system over the no-forecast alternative. Thus, for a forecast-based action system to demonstrate value, it often needs to be used over a prolonged length of time. However, knowing exactly how long it must be used to guarantee value is unquantified. This presents difficulties to institutions mandated to protect those at risk, who must justify the use of limited funds to act in advance of a potential, but not definite disaster, whilst planning multi-year strategies. Here we show how to determine the period over which decision makers must use forecasts in order to be confident of achieving ‘value’ over a no-forecast alternative. Results show that in the context of seasonal forecasting it is plausible that more than a decade may pass before a FbF system will have some certainty of showing value, and that if a particular user requires an almost-certain guarantee that using a forecast will be better than a no-forecast strategy, they must hold out until a near-perfect forecast system is available. The implication: there is potential value in seasonal forecasts, but to exploit it one must be prepared to play the long game.
    Keywords climate ; decision making ; drought ; economic valuation ; risk ; risk management ; temporal variation
    Language English
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 2751138-8
    ISSN 2212-0963
    ISSN 2212-0963
    DOI 10.1016/j.crm.2021.100375
    Database NAL-Catalogue (AGRICOLA)

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  2. Article: Evaluating the sensitivity of robust water resource interventions to climate change scenarios

    Geressu, Robel Tilaye / Siderius, Christian / Rao Kolusu, Seshagiri / Kashaigili, Japhet / Todd, Martin C. / Conway, Declan / Harou, Julien J.

    Climate risk management. 2022, v. 37

    2022  

    Abstract: Water resource system planning is complicated by uncertainty on the magnitude and direction of climate change. Therefore, developments such as new infrastructure or changed management rules that would work acceptably well under a diverse set of future ... ...

    Abstract Water resource system planning is complicated by uncertainty on the magnitude and direction of climate change. Therefore, developments such as new infrastructure or changed management rules that would work acceptably well under a diverse set of future conditions (i.e., robust solutions) are preferred. Robust multi-objective optimisation can help identify advantageous system designs which include existing infrastructure plus a selected subset of new interventions. The method evaluates options using simulated water resource performance metrics statistically aggregated to summarise performance over the climate scenario ensemble. In most cases such ‘robustness metrics’ are sensitive to scenarios under which the system performs poorly and so results may be strongly influenced by a minority of unfavorable climate scenarios. Understanding the influence of specific climate scenarios on robust optimised decision alternatives can help better interpret their results. We propose an automated multi-criteria design-under-uncertainty sensitivity analysis formulation that uses multi-objective evolutionary algorithms to reveal robust and efficient designs under different samples of a climate scenario ensemble. The method is applied to a reservoir management problem in the Rufiji River basin, Tanzania, which involves the second largest dam in Africa. We find that solutions optimised for robustness under alternative groups of climate scenarios exhibit important differences. This becomes particularly decision-relevant if analysts and/or decision-makers have differing confidence levels in the relevance of certain climate scenarios. The proposed approach motivates continued research on how climate model credibility should inform climate scenario selection because it demonstrates the influence scenario selection has on recommendations arising from robust optimisation design processes.
    Keywords automation ; climate ; climate change ; climate models ; decision making ; infrastructure ; risk management ; uncertainty ; watersheds ; Tanzania
    Language English
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 2751138-8
    ISSN 2212-0963
    ISSN 2212-0963
    DOI 10.1016/j.crm.2022.100442
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: Dust aerosol emission over the Sahara during summertime from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations

    Todd, Martin C / Carolina Cavazos-Guerra

    Atmospheric environment. 2016 Mar., v. 128

    2016  

    Abstract: Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. ... ...

    Abstract Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. Inadequate surface observations ensure that satellite data remain the primary source of this information over extensive and remote desert regions. Here, we develop estimates of the relative magnitude of active dust emission over the Sahara desert based on data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Utilising the unique vertical profile of aerosol characteristics provided by CALIOP our algorithm identifies emission from aerosol extinction and lidar backscatter in the near surface layers. From the long-term CALIOP archive of day and night-time orbits over 2006–13 we construct coarse resolution maps of a new dust emission index (DEI) for the Sahara desert during the peak summer dust season (June to September). The spatial structure of DEI indicates highest emission over a broad zone focused on the border regions of Southern Algeria, Northern Mali and northwest Niger, displaced substantially (∼7°) to the east of the mean maximum in satellite-derived aerosol optical depth. In this region night-time emission exceeds that during the day. The DEI maps substantially corroborate recently derived dust source frequency count maps based on back-tracking plumes in high temporal resolution SEVIRI imagery. As such, a convergence of evidence from multiple satellite data sources using independent methods provides an increasingly robust picture of Saharan dust emission sources. Various caveats are considered. As such, quantitative estimates of dust emission may require a synergistic combined multi-sensor analysis.
    Keywords aerosols ; algorithms ; atmospheric chemistry ; climate ; climate models ; dust emissions ; extinction ; information sources ; lidar ; orbits ; remote sensing ; summer ; weather ; Algeria ; Mali ; Niger ; Sahara Desert
    Language English
    Dates of publication 2016-03
    Size p. 147-157.
    Publishing place Elsevier Ltd
    Document type Article
    ZDB-ID 216368-8
    ISSN 0004-6981 ; 1352-2310
    ISSN 0004-6981 ; 1352-2310
    DOI 10.1016/j.atmosenv.2015.12.037
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: Towards drought impact-based forecasting in a multi-hazard context

    Boult, Victoria L. / Black, Emily / Saado Abdillahi, Halima / Bailey, Meghan / Harris, Clare / Kilavi, Mary / Kniveton, Dominic / MacLeod, David / Mwangi, Emmah / Otieno, George / Rees, Elizabeth / Rowhani, Pedram / Taylor, Olivia / Todd, Martin C.

    Climate risk management. 2022, v. 35

    2022  

    Abstract: The lives and livelihoods of people around the world are increasingly threatened by climate-related risks as climate change increases the frequency and severity of high-impact weather. In turn, the risk of multiple hazards occurring simultaneously grows ... ...

    Abstract The lives and livelihoods of people around the world are increasingly threatened by climate-related risks as climate change increases the frequency and severity of high-impact weather. In turn, the risk of multiple hazards occurring simultaneously grows and compound impacts become more likely. The World Meteorological Organization (WMO) proposed the use of multi-hazard impact-based forecasting (IbF) to better anticipate and reduce the impacts of concurrent hazards, but as yet, there are few operational examples in the humanitarian sector. Drought is particularly susceptible to multi-hazard influences. However, challenges encountered in the development of drought IbF systems – including poor understanding of compound impacts and specific hazard-focused mandates – raise important questions for the feasibility of multi-hazard IbF as envisioned by the WMO. With these challenges in mind, we propose an interim approach in which real-time assessment of dynamic vulnerability provides a context for drought-based IbF. The incorporation of dynamic vulnerability indicators account for the local effects of non-drought hazards, whilst the use of a drought-based system facilitates effective intervention. The proposed approach will improve our understanding of compound events, enhance adoption of IbF in the humanitarian sector, and better mitigate the impacts of concurrent hazards.
    Keywords climate ; climate change ; drought ; risk ; risk management
    Language English
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 2751138-8
    ISSN 2212-0963
    ISSN 2212-0963
    DOI 10.1016/j.crm.2022.100402
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: Mainstreaming forecast based action into national disaster risk management systems: experience from drought risk management in Kenya

    Mwangi, Emmah / Taylor, Olivia / Todd, Martin C. / Visman, Emma / Kniveton, Dom / Kilavi, Mary / Ndegwa, William / Otieno, George / Waruru, Shamton / Mwangi, John / Ambani, Maurine / Abdillahi, Halima / MacLeod, David / Rowhani, Pedram / Graham, Richard / Colman, Andrew

    Climate and development. 2022 Sept. 14, v. 14, no. 8

    2022  

    Abstract: Drought and food security crises heighten risks to lives and livelihoods in East Africa. In recent years, a shift towards acting in advance of such events has gained momentum, notably among the humanitarian and development community. This shift is ... ...

    Abstract Drought and food security crises heighten risks to lives and livelihoods in East Africa. In recent years, a shift towards acting in advance of such events has gained momentum, notably among the humanitarian and development community. This shift is premised on tools that link climate forecasts with pre-agreed actions and funding, known as Forecast-based Action (FbA), or anticipatory action more widely. While FbA approaches have been developed by a number of humanitarian agencies, the key to scaling-up is mainstreaming these approaches into national risk management systems. This paper addresses this gap in the context of drought risk management in Kenya. We analyse Kenya's current drought management system to assess the potential usability of climate forecast information within the existing system, and outline steps towards improved usability of climate information. Further, we note the critical importance of enabling institutions and reliable financing to ensure that information can be consistently used to trigger early action. We discuss the implications of this for scaling-up FbA into national risk management systems.
    Keywords climate ; drought ; food security ; management systems ; risk management ; Kenya
    Language English
    Dates of publication 2022-0914
    Size p. 741-756.
    Publishing place Taylor & Francis
    Document type Article
    ISSN 1756-5537
    DOI 10.1080/17565529.2021.1984194
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Uncertainty assessment in river flow projections for Ethiopia’s Upper Awash Basin using multiple GCMs and hydrological models

    Chan, Wilson C. H / Thompson, Julian R / Taylor, Richard G / Nay, Alistair E / Ayenew, Tenalem / MacDonald, Alan M / Todd, Martin C

    Hydrological sciences journal. 2020 July 26, v. 65, no. 10

    2020  

    Abstract: Uncertainty in climate change impacts on river discharge in the Upper Awash Basin, Ethiopia, is assessed using five MIKE SHE hydrological models, six CMIP5 general circulation models (GCMs) and two representative concentration pathways (RCP) scenarios ... ...

    Abstract Uncertainty in climate change impacts on river discharge in the Upper Awash Basin, Ethiopia, is assessed using five MIKE SHE hydrological models, six CMIP5 general circulation models (GCMs) and two representative concentration pathways (RCP) scenarios for the period 2071–2100. Hydrological models vary in their spatial distribution and process representations of unsaturated and saturated zones. Very good performance is achieved for 1975–1999 (NSE: 0.65–0.8; r: 0.79–0.93). GCM-related uncertainty dominates variability in projections of high and mean discharges (mean: –34% to +55% for RCP4.5, – 2% to +195% for RCP8.5). Although GCMs dominate uncertainty in projected low flows, inter-hydrological model uncertainty is considerable (RCP4.5: –60% to +228%, RCP8.5: –86% to +337%). Analysis of variance uncertainty attribution reveals that GCM-related uncertainty occupies, on average, 68% of total uncertainty for median and high flows and hydrological models no more than 1%. For low flows, hydrological model uncertainty occupies, on average, 18% of total uncertainty; GCM-related uncertainty remains substantial (average: 28%).
    Keywords analysis of variance ; basins ; climate change ; hydrologic models ; model uncertainty ; river flow ; Ethiopia
    Language English
    Dates of publication 2020-0726
    Size p. 1720-1737.
    Publishing place Taylor & Francis
    Document type Article
    Note NAL-AP-2-clean
    ISSN 2150-3435
    DOI 10.1080/02626667.2020.1767782
    Database NAL-Catalogue (AGRICOLA)

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  7. Article: Rainfall-derived growing season characteristics for agricultural impact assessments in South Africa

    Ambrosino, Chiara / Chandler, Richard E / Todd, Martin C

    Theoretical and applied climatology. 2014 Feb., v. 115, no. 3-4

    2014  

    Abstract: Precipitation variability imposes significant pressure in areas where agricultural practice is dominated by smallholder farmers who are dependent on subsistence farming. Advances in the understanding of this variability, in both time and space, have an ... ...

    Abstract Precipitation variability imposes significant pressure in areas where agricultural practice is dominated by smallholder farmers who are dependent on subsistence farming. Advances in the understanding of this variability, in both time and space, have an important role to play in increasing the resilience of agricultural systems. The need is particularly pressing in regions of the world such as the African continent, which is already affected by multiple stresses including poverty and economic and political instability. In this paper, we explore the use of generalised linear models (GLMs) for this purpose, via a case study from north-east South Africa. A GLM is used to link the local rainfall variability to large-scale climate drivers identified from previous subcontinental-scale analyses, and the ability of the resulting model to simulate precipitation features that are relevant in agricultural applications is evaluated. We focus in particular on a set of growing season indices, proposed for the investigation of intraseasonal characteristics relevant for maize production in the region. Seven indices were computed from spatially averaged daily rainfall series from nine stations in the study area. As a first attempt to use GLMs for this type of application, the results are encouraging and suggest that the models are able to reproduce a range of agriculture-relevant indices. However, further research into spatial correlation structure is recommended to improve the multisite generation of the rainfall-derived characteristics.
    Keywords case studies ; climate ; crop production ; economics ; farmers ; growing season ; linear models ; politics ; poverty ; rain ; simulation models ; space and time ; subsistence farming ; South Africa
    Language English
    Dates of publication 2014-02
    Size p. 411-426.
    Publishing place Springer-Verlag
    Document type Article
    ZDB-ID 1463177-5
    ISSN 1434-4483 ; 0177-798X
    ISSN (online) 1434-4483
    ISSN 0177-798X
    DOI 10.1007/s00704-013-0896-y
    Database NAL-Catalogue (AGRICOLA)

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  8. Book ; Online: Are Kenya Meteorological Department heavy rainfall advisories useful for forecast-based early action and early preparedness for flooding?

    MacLeod, David / Kilavi, Mary / Mwangi, Emmah / Ambani, Maurine / Osunga, Michael / Robbins, Joanne / Graham, Richard / Rowhani, Pedram / Todd, Martin C.

    eISSN: 1684-9981

    2021  

    Abstract: Preparedness saves lives. Forecasts can help improve preparedness by triggering early actions as part of pre-defined protocols under the Forecast-based Financing (FbF) approach; however it is essential to understand the skill of a forecast before using ... ...

    Abstract Preparedness saves lives. Forecasts can help improve preparedness by triggering early actions as part of pre-defined protocols under the Forecast-based Financing (FbF) approach; however it is essential to understand the skill of a forecast before using it as a trigger. In order to support the development of early-action protocols over Kenya, we evaluate the 33 heavy rainfall advisories (HRAs) issued by the Kenya Meteorological Department (KMD) during 2015–2019. The majority of HRAs warn counties which subsequently receive heavy rainfall within the forecast window. We also find a significant improvement in the advisory ability to anticipate flood events over time, with particularly high levels of skill in recent years. For instance actions with a 2-week lifetime based on advisories issued in 2015 and 2016 would have failed to anticipate nearly all recorded flood events in that period, whilst actions in 2019 would have anticipated over 70 % of the instances of flooding at the county level. When compared against the most significant flood events over the period which led to significant loss of life, all three such periods during 2018 and 2019 were preceded by HRAs, and in these cases the advisories accurately warned the specific counties for which significant impacts were recorded. By contrast none of the four significant flooding events in 2015–2017 were preceded by advisories. This step change in skill may be due to developing forecaster experience with synoptic patterns associated with extremes as well as access to new dynamical prediction tools that specifically address extreme event probability; for example, KMD access to the UK Met Office Global Hazard Map was introduced at the end of 2017. Overall we find that KMD HRAs effectively warn of heavy rainfall and flooding and can be a vital source of information for early preparedness. However a lack of spatial detail on flood impacts and broad probability ranges limit their utility for systematic FbF approaches. We conclude with suggestions for making the HRAs more useful for FbF and outline the developing approach to flood forecasting in Kenya.
    Subject code 333
    Language English
    Publishing date 2021-01-25
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Book ; Online: The early summertime Saharan heat low

    Alamirew, Netsanet K. / Todd, Martin C. / Ryder, Claire L. / Marsham, John H. / Wang, Yi

    eISSN: 1680-7324

    sensitivity of the radiation budget and atmospheric heating to water vapour and dust aerosol

    2018  

    Abstract: The Saharan heat low (SHL) is a key component of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, ...

    Abstract The Saharan heat low (SHL) is a key component of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quantify the independent effects of variability in dust and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Algeria (21.4° N, 0.9° E), close to the SHL core for June 2011. Overall, we find dust aerosol and water vapour to be of similar importance in driving variability in the top-of-atmosphere (TOA) radiation budget and therefore the column-integrated heating over the SHL (∼ 7 W m −2 per standard deviation of dust aerosol optical depth – AOD). As such, we infer that SHL intensity is likely to be similarly enhanced by the effects of dust and water vapour surge events. However, the details of the processes differ. Dust generates substantial radiative cooling at the surface (∼ 11 W m −2 per standard deviation of dust AOD), presumably leading to reduced sensible heat flux in the boundary layer, which is more than compensated by direct radiative heating from shortwave (SW) absorption by dust in the dusty boundary layer. In contrast, water vapour invokes a radiative warming at the surface of ∼ 6 W m −2 per standard deviation of column-integrated water vapour in kg m −2 . Net effects involve a pronounced net atmospheric radiative convergence with heating rates on average of 0.5 K day −1 and up to 6 K day −1 during synoptic/mesoscale dust events from monsoon surges and convective cold-pool outflows (<q>haboobs</q>). On this basis, we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. Depending on the synoptic context over the region, processes driving variability involve both independent effects of water vapour and dust and compensating events in which dust and water vapour are co-varying. Forecast models typically have biases of up to 2 kg m −2 in column-integrated water vapour (equivalent to a change in 2.6 W m −2 TOA net flux) and typically lack variability in dust and thus are expected to poorly represent these couplings. An improved representation of dust and water vapour and quantification of associated radiative impact in models is thus imperative to further understand the SHL and related climate processes.
    Subject code 333
    Language English
    Publishing date 2018-01-31
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  10. Book ; Online: The summertime Saharan heat low

    Alamirew, Netsanet K. / Todd, Martin C. / Ryder, Claire L. / Marsham, John M. / Wang, Yi

    eISSN: 1680-7324

    Sensitivity of the radiation budget and atmospheric heating to water vapor and dust aerosol

    2017  

    Abstract: The Saharan heat low (SHL) is a key component of the West African climate system and an important driver of the West African Monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, ...

    Abstract The Saharan heat low (SHL) is a key component of the West African climate system and an important driver of the West African Monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quantify the independent effects of variability in dust and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Algeria (0.9E, 21.4N), close to the SHL core, for June 2011. Overall, we find dust aerosol and water vapour to be of similar importance in driving variability in the top of atmosphere (TOA) radiation budget and therefore the column integrated heating over the SHL (~7 W m −2 per standard deviation of dust AOD). As such we infer that SHL intensity is likely to be similarly enhanced by the effects of dust and water vapour surge events. However, the details of the processes differ. Dust generates substantial radiative cooling at the surface (~11 W m −2 per standard deviation of dust AOD), presumably leading to reduced sensible heat flux into the boundary layer, which is more than compensated by direct radiative heating from SW absorption by dust in the dusty boundary layer. In contrast water vapour invokes a longwave radiative warming of at the surface of ~6 W m −2 per standard deviation of column integrated water vapour in Kg m −2 . Net effects involve a pronounced net atmospheric radiative convergence with heating rates on average of 0.5 K day −1 and up to 6 K day −1 during synoptic/meso-scale dust events from monsoon surges and convective cold pool outflows (‘haboobs’). On this basis we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. Depending on the synoptic context over the region processes driving variability involve both independent effects of water vapour and dust and compensating events in which dust and water vapour are co-varying. Forecast models typically have biases of up to 2 kg m −2 in column integrated water vapour (equivalent to a change in 2.6 W m −2 TOA net flux) and typically lack variability in dust, and so are expected to poorly represent these couplings. An improved representation dust and water vapour and quantification of associated radiative impact is thus imperative in quest for the answer to what remains to be uncertain related with the climate system of the SHL region.
    Subject code 333
    Language English
    Publishing date 2017-05-15
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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