Trends of Rainfall Onset, Cessation, and Length of Growing Season in Northern Ghana: Comparing the Rain Gauge, Satellite, and Farmer’s Perceptions

Rainfall onset and cessation date greatly influence cropping calendar decisions in rain-fed agricultural systems. This paper examined trends of onsets, cessation, and the length of growing season over Northern Ghana using CHIRPS-v2, gauge, and farmers’ perceptions data between 1981 and 2019. Results from CHIRPS-v2 revealed that the three seasonal rainfall indices have substantial latitudinal variability. Significant late and early onsets were observed at the West and East of 1.5° W longitude, respectively. Significant late cessations and longer growing periods occurred across Northern Ghana. The ability of farmers’ perceptions and CHIRPS-v2 to capture rainfall onsets are time and location-dependent. A total of 71% of farmers rely on traditional knowledge to forecast rainfall onsets. Adaptation measures applied were not always consistent with the rainfall seasonality. More investment in modern climate information services is required to complement the existing local knowledge of forecasting rainfall seasonality.

Flood inundation and broader ecosystem service modelling in a data-sparse catchment; application of LUCI to Marokopa, NZ

<p>Event magnitude, societal vulnerability, and exposure define hazard impact. In New Zealand, flooding is the most common and damaging hazard at the decadal scale. Residents within the Marokopa catchment (west coast of the Waikato region) identify flood and erosion as significant local hazards. Flooding is influenced by a diverse range in factors, from environmental factors in the catchment, such as hydrology and climate, to socio-political policies and community awareness. Each of these factors is themselves influenced by climate change, and therefore requires study at the local and national scales. A mixed-methods approach was used to analyse flood and erosion through application of the Land Use and Capability Indicator (LUCI). Qualitative analysis along with rainfall-runoff, inundation, and holistic ecosystem service (ES) modelling are used to evaluate both flood and erosion extent, but also influencing factors. This research used a unique, mixed-methods approach to research a traditionally quantitative topic, improve on the understanding of karstic rainfall-runoff modelling and support LUCI development through application in a geomorphologically distinct location. Local knowledge facilitated both temporal and spatial outlining of flood and erosion extent at macro and catchment-scales. Bespoke rainfall-runoff modelling of the Marokopa upper catchment defined localised rainfall, seasonality and the karstic system as significant influences on runoff, with poor to excellent model-fit. Preliminary inundation findings outlined tidal, upper catchment bank-overflow, and overland flow as significant mechanisms of flooding. Finally, flood and erosion mitigation ecosystem services were modelled, with synergistic comparisons also analysed. Priority areas for future land management and hazard mitigation investment include the Marokopa floodplains ~5 km inland from the coast. Novel integration of physical and social observations outlines current flood risk extent and evaluates factors which contribute to flooding, providing a thorough knowledge base for future flood modelling within the Marokopa catchment.</p>

Flood inundation and broader ecosystem service modelling in a data-sparse catchment; application of LUCI to Marokopa, NZ

<p>Event magnitude, societal vulnerability, and exposure define hazard impact. In New Zealand, flooding is the most common and damaging hazard at the decadal scale. Residents within the Marokopa catchment (west coast of the Waikato region) identify flood and erosion as significant local hazards. Flooding is influenced by a diverse range in factors, from environmental factors in the catchment, such as hydrology and climate, to socio-political policies and community awareness. Each of these factors is themselves influenced by climate change, and therefore requires study at the local and national scales. A mixed-methods approach was used to analyse flood and erosion through application of the Land Use and Capability Indicator (LUCI). Qualitative analysis along with rainfall-runoff, inundation, and holistic ecosystem service (ES) modelling are used to evaluate both flood and erosion extent, but also influencing factors. This research used a unique, mixed-methods approach to research a traditionally quantitative topic, improve on the understanding of karstic rainfall-runoff modelling and support LUCI development through application in a geomorphologically distinct location. Local knowledge facilitated both temporal and spatial outlining of flood and erosion extent at macro and catchment-scales. Bespoke rainfall-runoff modelling of the Marokopa upper catchment defined localised rainfall, seasonality and the karstic system as significant influences on runoff, with poor to excellent model-fit. Preliminary inundation findings outlined tidal, upper catchment bank-overflow, and overland flow as significant mechanisms of flooding. Finally, flood and erosion mitigation ecosystem services were modelled, with synergistic comparisons also analysed. Priority areas for future land management and hazard mitigation investment include the Marokopa floodplains ~5 km inland from the coast. Novel integration of physical and social observations outlines current flood risk extent and evaluates factors which contribute to flooding, providing a thorough knowledge base for future flood modelling within the Marokopa catchment.</p>

Intensity of land use by pasture as result of pedogeoclimatic characteristics and anthropogenic management

In the world, the most significant change in the ecosystems structure is the conversion from natural land surface into cultivated systems. In 2018, 26.8% of the Brazilian territory was occupied by agricultural activities, from which 73% is pasture. Considering that the management adopted in Brazilian pastures is incipient and leads to degradation, there is a need to characterize the state of the pastures to diagnose the intensity of this use on the soil. However, the diagnosis of large areas using satellites with more detailed resolution is limited by cloud coverage and low temporal resolution. In this sense, the present work aims to diagnose the intensity of land use by pastures (ILUP) in large areas based on the mosaic of images from Landsat 8 (LS8), Landsat 7 (LS7), Sentinel-2 (S2), and MODIS. The methodology consists of harmonizing the NDVI from LS7 and S2 satellites with LS8. For MODIS, the harmonization was carried out based on ILUP obtained previously from NDVI LS8. The methodology was applied at the Doce river basin (DRB). The combination of different sensors allowed to overcome the cloud coverage limitation. DRB has 61.3% of its area occupied by pastures and 78.2% of them have some degree of degradation. ILUP was dependent on DRB’s pedological and climatic characteristics. This dependence is enhanced due to pasture management in the basin, mainly characterized by continuous grazing, which commonly leads to overgrazing scenarios. The areas with great rainfall seasonality and associated with Acrisols/Cambisols are the most susceptible to degradation.

Multiple adaptive solutions to face climatic constraints: novel insights in the debate over the role of convergence in local adaptation

The extent to which genomic convergence shapes locally adapted phenotypes in different species remains a fundamental question in evolutionary biology. It would help assessing the relative role of historical contingencies versus determinism in evolution. To bring new insights to this debate we set up a framework which aimed to compare the adaptive trajectories of two domesticated mammal species co-distributed in diversified landscapes. We sequenced the genomes of 160 sheep and 161 goats extensively managed along environmental gradients, including temperature, rainfall, seasonality and altitude, to identify genes and biological processes shaping local adaptation. Allele frequencies at adaptive loci were rarely found to vary gradually along environmental gradients, but rather displayed a discontinuous shift at the extremities of environmental clines. Of the more than 430 adaptive genes identified, only 6 were orthologous between sheep and goats and those responded differently to environmental pressures, suggesting different adaptive mechanisms in these two closely related species. Such diversity of adaptive pathways may result from a high number of biological functions involved in adaptation to multiple eco-climatic gradients, and provides more arguments for the role of contingency and stochasticity in adaptation rather than repeatability and determinism.

South African Winter Rainfall Zone Shifts: A Comparison of Seasonality Metrics For Cape Town From 1841-1899 and 1933-2020

Mounting evidence across South Africa’s southwestern winter rainfall zone (WRZ) reflects consistent drying since ~1980 and projected trends suggest this will continue. However, limited evidence exists for the region’s rainfall seasonality changes. To improve our understanding of these WRZ drying trends, especially within the context of Cape Town’s 2015-2017 “Day Zero” drought, it is necessary to explore long-term rainfall seasonality trends. Thus, we use the longest WRZ meteorological record from the South African Astronomical Observatory (SAAO) in Cape Town to investigate rainfall seasonality shifts during 1841-2020. Consistent with recorded poleward migrations of the subtropical high-pressure belt and mid-latitude westerlies, known drivers behind the drought and drying trends, calculated trends demonstrate strengthening of WRZ conditions, primarily from a later start-date trend leading to a shorter wet-season. Long-term drying trends are quantified for the wet- and dry-seasons, however, analysis of trend evolution reveals much variability, reflecting that drying has only persisted since ~1892. Comparative analyses of the first and last 59 years of 1841-2020 reveals a rainfall decline of ~10% across both seasons – highlighting that the extreme “Day Zero” drought was not only driven by wet-season rainfall declines. Results demonstrate that these drying trends were consistently driven by a long-term decline in rain day counts and a more recent decline in average rainfall per rain day. Correspondence between our results and projected rainfall seasonality trends suggests the trends we quantified will likely continue, thus improvements and continuation of existing water conservation and management strategies are imperative for Cape Town.

A 18,000 yr record of tropical land temperature, convective activity and rainfall seasonality from the maritime continent

The maritime continent exports an enormous amount of (latent) heat and moisture to the rest of the globe via deep atmospheric convection. How this export has changed through time under evolving boundary conditions, including the inundation of former Sundaland, is critical for the understanding of global climate dynamics. Given its size, relatively few high-resolution and continuous records exist of past hydroclimate, while terrestrial paleotemperature records are still completely absent from the region. In this study we present a 18,000-year multi-proxy record obtained from a lake sediment at the NW corner of former Sundaland. We found that rainfall seasonality was very important over the entire deglacial period, evidenced by biomass burning and C4 vegetation, despite rising atmospheric CO2 levels and increasing humidity that normally promotes C3 rainforests. The strong seasonality was reduced only upon ongoing inundation of Sundaland, with a clear inflection point around the Older Dryas event (13.8 ka BP), indicating a distinct system change. Land temperatures during the last stadial periods were 5°C colder than today’s 27°C. Temperatures rose gradually during the early Holocene to reach 29°C between 7-2 ka BP, accompanied by increasing convection, both driven by insolation power during the wet season. Convection decreased with lowering wet-season (autumn) insolation during the Meghalayan period, concurrent with the known increase of ENSO variability and Northern Hemisphere climate cooling and drying. Our results provide further insight in the role of Sundaland - turned maritime continent for the global climate system in response to sea level rise and orbital forcing.