Congo Basin rainfall climatology: can we believe the climate models?

Washington, Richard; James, Rachel; Pearce, H; Pokam, Wilfried M.; Moufouma-Okia, Wilfran

doi:10.1098/rstb.2012.0296

Cited by 210 publications

(236 citation statements)

References 26 publications

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“…During June and July, the average rainfall reaches its lowest level of around 2 mm day −1 . This cycle is similar to what was described by Washington et al (2013), who compared the Congo's rainfall climatology through several datasets from reanalysis and ensemble models. However, these authors argued that the maximum rainfall in the basin occurs from March to May and from September to November, while the minimum occurs in June-August.…”

Section: Resultssupporting

confidence: 82%

A Lagrangian perspective of the hydrological cycle in the Congo River basin

et al. 2017

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Abstract. The Lagrangian model FLEXPART is used to identify the moisture sources of the Congo River basin (CRB) and investigate their role in the hydrological cycle. This model allows us to track atmospheric parcels while calculating changes in the specific humidity through the budget of evaporation minus precipitation. This method permits the annual-scale identification of five continental and four oceanic principal regions that provide moisture to the CRB from both hemispheres over the course of the year. The most important is the CRB, which provides more than 50 % of the total atmospheric moisture contribution to precipitation over itself. Additionally, both the land that extends to the east of the CRB and the eastern equatorial South Atlantic Ocean are very important sources, while the Red Sea source is merely important in the (E − P ) budget over the CRB despite its high evaporation rate. The moisture-sink patterns over the CRB in air masses that were tracked forward in time from all the sources follow the latitudinal rainfall migration and are mostly highly correlated with the pattern of the precipitation rate, ensuring a link between them. In wet (dry) years, the contribution of moisture to precipitation from the CRB over itself increases (decreases). Despite the enhanced evaporative conditions over the basin during dry years, the vertically integrated moisture flux (VIMF) divergence inhibits precipitation and suggests the transport of moisture from the CRB to remote regions.

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Section: Resultssupporting

confidence: 82%

A Lagrangian perspective of the hydrological cycle in the Congo River basin

et al. 2017

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“…This may be in part attributable to the positive moist bias in the Congo basin in the ERA-Interim reanalysis (used as boundary data for the Congo simulation) when compared to other reanalyses (Washington et al, 2013). Despite the positive cloud fraction bias in both schemes, we find that the Thompson scheme compares better than the Morrison scheme against observed cloud fractions, largely due to the overproduction of upper-level ice in the Morrison scheme.…”

Section: Congo Supercell Ricomentioning

confidence: 62%

“…The model initial and boundary conditions were generated from ERAInterim reanalysis (Dee et al, 2011) starting at 00:00 UTC on 1 August 2007. The simulation start date was chosen to coincide with the onset of the seasonal peak in precipitation (Washington et al, 2013) and the simulation was integrated for 10 days (with a time step of 12 s) in order to identify the nature of the convection and its response to CDNC perturbations over timescales greater than that of the life cycle of any individual convective system. We use a horizontal grid length of 4 km and 30 vertical levels with the standard WRF stretched vertical grid.…”

Section: Model Configurationsmentioning

confidence: 99%

Uncertainty from the choice of microphysics scheme in convection-permitting models significantly exceeds aerosol effects

White

Gryspeerdt²,

Stier

et al. 2017

Atmos. Chem. Phys.

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Abstract. This study investigates the hydrometeor development and response to cloud droplet number concentration (CDNC) perturbations in convection-permitting model configurations. We present results from a real-data simulation of deep convection in the Congo basin, an idealised supercell case, and a warm-rain large-eddy simulation (LES). In each case we compare two frequently used double-moment bulk microphysics schemes and investigate the response to CDNC perturbations. We find that the variability among the two schemes, including the response to aerosol, differs widely between these cases. In all cases, differences in the simulated cloud morphology and precipitation are found to be significantly greater between the microphysics schemes than due to CDNC perturbations within each scheme. Further, we show that the response of the hydrometeors to CDNC perturbations differs strongly not only between microphysics schemes, but the inter-scheme variability also differs between cases of convection. Sensitivity tests show that the representation of autoconversion is the dominant factor that drives differences in rain production between the microphysics schemes in the idealised precipitating shallow cumulus case and in a subregion of the Congo basin simulations dominated by liquidphase processes. In this region, rain mass is also shown to be relatively insensitive to the radiative effects of an overlying layer of ice-phase cloud. The conversion of cloud ice to snow is the process responsible for differences in cold cloud bias between the schemes in the Congo. In the idealised supercell case, thermodynamic impacts on the storm system using different microphysics parameterisations can equal those due to aerosol effects. These results highlight the large uncertainty in cloud and precipitation responses to aerosol in convectionpermitting simulations and have important implications not only for process studies of aerosol-convection interaction, but also for global modelling studies of aerosol indirect effects. These results indicate the continuing need for tighter observational constraints of cloud processes and response to aerosol in a range of meteorological regimes.

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“…James, Washington, & Rowell, 2014). This is due to a combination of factors, such as poor observational records, high levels of interannual and decadal climate variability that are poorly simulated, and a low level of investment in climate science (Kusangaya, Warburton, Archer van Garderen, & Jewitt, 2014;Shongwe, van Oldenborgh, van den Hurk, de Boer, Coelho, & van Aalst, 2009;Washington, James, Pearce, Pokam, & Moufouma-Okia, 2013). There is a pressing need for climate information to inform national-level planning, and policy and decision making across a range of sectors, environments, and socio-political settings (Jones, Roux, Scott, & Tanner, 2014;Vaughan & Dessai, 2014), to support future climate-resilient development and to help safeguard promising trends of economic development across the region.…”

Section: Introductionmentioning

confidence: 99%

Identifying climate services needs for national planning: insights from Malawi

et al. 2015

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The importance of climate services, i.e. providing targeted, tailored, and timely weather and climate information, has gained momentum, but requires improved understanding of user needs. This article identifies the opportunities and barriers to the use of climate services for planning in Malawi, to identify the types of information that can better inform future adaptation decisions in sub-Saharan Africa. From policy analysis, stakeholder interviews, and a national workshop utilizing serious games, it is determined that only 5-10 day and seasonal forecasts are currently being used in government decision making. Impediments to greater integration of climate services include spatial and temporal scale, accessibility, timing, credibility and the mismatch in timeframes between planning cycles (1-5 years) and climate projections (over 20 years). Information that could more usefully inform planning decisions includes rainfall distribution within a season, forecasts with 2-3 week lead times, likely timing and location of extreme events in the short term (1 -5 years), and projections (e.g. rainfall and temperature change) in the medium term (6 -20 years). Development of a national set of scenarios would also make climate information more accessible to decision makers, and capacity building around such scenarios would enable its improved use in short-to medium-term planning. Improved climate science and its integration with impact models offer exciting opportunities for integrated climate-resilient planning across sub-Saharan Africa. Accrual of positive impacts requires enhanced national capacity to interpret climate information and implement communication strategies across sectors. Policy relevanceFor climate services to achieve their goal of improving adaptation decision making, it is necessary to understand the decision making process and how and when various types of weather and climate information can be incorporated. Through a case study of public sector planning in Malawi, this article highlights relevant planning and policy-making processes. The current use of weather and climate information and needs, over various timescales -sub-annual to short term (1-5 years) to medium term (6 -20 years) -is outlined. If climate scientists working with boundary organizations are able to address these issues in a more targeted, sector-facing manner they will improve the uptake of climate services and the likelihood of climate-resilient decisions across sub-Saharan Africa.

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Congo Basin rainfall climatology: can we believe the climate models?

Cited by 210 publications

References 26 publications

A Lagrangian perspective of the hydrological cycle in the Congo River basin

A Lagrangian perspective of the hydrological cycle in the Congo River basin

Uncertainty from the choice of microphysics scheme in convection-permitting models significantly exceeds aerosol effects

Identifying climate services needs for national planning: insights from Malawi

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