Local Climate Variability Research Articles

The 2018–2019 weak El Niño: Predicting the risk of a dengue outbreak in Machala, Ecuador

AbstractBetween October 2018 ‐ May 2019, sea surface temperature conditions in the central‐eastern tropical Pacific indicated a mild El Niño event. In May 2019, the global El Niño Southern Oscillation (ENSO) forecast consensus was that these generally weak warm patterns will persist at least until the end of the northern hemisphere summer. El Niño and its impact on local climatic conditions in southern coastal Ecuador influence the inter‐annual transmission of dengue fever in the region. In this study, we use an ENSO model to issue forecasts of El Niño for the year 2019, which are then used to predict local climate variables, precipitation and minimum temperature, in the city of Machala, Ecuador. All these forecasts are incorporated in a dengue transmission model, specifically developed and tested for this area, to produce out‐of‐sample predictions of dengue risk. Predictions are issued at the beginning of January 2019 for the whole year, thus providing the longest forecast lead time of 12 months. Preliminary results indicate that the mild and ongoing El Niño event did not provide the optimum climate conditions for dengue transmission, with the model predicting a very low probability of a dengue outbreak during the typical peak season in Machala in 2019. This is contrary to 2016, when a large El Niño event resulted in excess rainfall and warmer temperatures in the region, and a dengue outbreak occurred 3 months earlier than expected. This event was successfully predicted using a similar prediction framework to the one applied here. With the present study, we continue our efforts to build and test a climate service tool to issue early warnings of dengue outbreaks in the region.

Stochastic modeling of long-term wave climate based on weather patterns for coastal structures applications

Port development – as key aspect of sustained economic growth – implies large investments in coastal structures, increasing the risk of structural failures and operational stoppages due to coastal hazards. Then, this paper presents a new approach to statistically characterize and simulate the long-term wave climate to be applied in port risk assessment methodologies in a context of uncertainty. As a starting-point, the weather types framework is used, relating the multivariate and non-stationary climate conditions in an ocean site (the so-called predictand) to continuous-time Markov process of large-scale sea-level pressure and sea-level pressure gradient fields (the so-called predictor). Based on the predictor–predictand relationship, a comprehensive framework composed by three interlinking stochastic models is developed. Firstly, a statistical model describing the predictor is introduced. It is based on identifying representative daily mean synoptic circulation patterns (the so-called Weather Types, WTs) and its probabilistic chronology model at monthly time-scale. Secondly, a multivariate statistical model for the daily predictand is characterized by Gaussian copulas at WT-scale. Thirdly, a multivariate statistical model for downscaling predictand variables to hourly time-scale from daily data is developed. The results highlight that the proposed methodology is a powerful tool for coastal structures applications because disruptive events inducing reliability, functionality and operability failures can be studied simultaneously. The proposed climate-emulator models the long-term wave climate at hourly time-resolution but with a properly and accurate extreme value distribution, taking into account that the local wave climate variables are cross-correlated (4-dimensional compound events), auto-correlated (at daily time-scale) and non-stationary (intra-annual variability). The model is applied at a location in the South West of the Mediterranean basin for emulating wave and storm surge drivers. A cross-validation procedure is applied to verify accuracy of the model, showing a good agreement of the simulated data with the validation samples.

Numerical simulation of a geotextile soil wall considering soil-atmosphere interaction

This paper presents a numerical method for considering soil-atmosphere interaction applied to infiltration into an unsaturated geosynthetic reinforced soil wall and its effect on wall stability. A hypothetical nonwoven geotextile reinforced soil wall was subjected to simulated conditions of evaporation and precipitation over 2 years considering local climate variation in São Paulo city, Brazil. Net infiltration and actual evaporation were quantified inside and outside the reinforced zone, allowing for the assessment of changes in soil suction and factors of safety. The study discusses the implications of using in-plane draining reinforcements (e.g. nonwoven geotextiles) and soil-atmosphere effects. Results show that soil suction and factors of safety variation are more dependent on consecutive days of precipitation than on isolated heavy rainfalls. For the climate conditions considered in this study, results show that approximately 50% of the precipitation and potential evaporation transformed into net infiltration and actual evaporation, respectively. Additionally, the numerical results indicate that after the first wetting of the soil inside the reinforced soil zone, the evaporation to the atmosphere did not remove water from the inside of the geosynthetic reinforced wall because of the capillary break.

Persistent Vegetation Greening and Browning Trends Related to Natural and Human Activities in the Mount Elgon Ecosystem

Many developing nations are facing severe food insecurity partly because of their dependence on rainfed agriculture. Climate variability threatens agriculture-based community livelihoods. With booming population growth, agricultural land expands, and natural resource extraction increases, leading to changes in land use and land cover characterized by persistent vegetation greening and browning. This can modify local climate variability due to changing land–atmosphere interactions. Yet, for landscapes with significant interannual variability, such as the Mount Elgon ecosystem in Kenya and Uganda, characterizing these changes is a difficult task and more robust methods have been recommended. The current study combined trend (Mann–Kendall and Sen’s slope) and breakpoint (bfast) analysis methods to comprehensively examine recent vegetation greening and browning in Mount Elgon at multiple time scales. The study used both Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) and Climate Hazards group Infrared Precipitation with Stations (CHIRPS) data and attempted to disentangle nature- versus human-driven vegetation greening and browning. Inferences from a 2019 field study were valuable in explaining some of the observed patterns. The results indicate that Mount Elgon vegetation is highly variable with both greening and browning observable at all time scales. Mann–Kendall and Sen’s slope revealed major changes (including deforestation and reforestation), while bfast detected most of the subtle vegetation changes (such as vegetation degradation), especially in the savanna and grasslands in the northeastern parts of Mount Elgon. Precipitation in the area had significantly changed (increased) in the post-2000 era than before, particularly in 2006–2010, thus influencing greening and browning during this period. The greenness–precipitation relationship was weak in other periods. The integration of Mann–Kendall and bfast proved useful in comprehensively characterizing vegetation greenness. Such a comprehensive description of Mount Elgon vegetation dynamics is an important first step to instigate policy changes for simultaneously conserving the environment and improving livelihoods that are dependent on it.

Different Predictors Shape the Diversity Patterns of Epiphytic and Non-epiphytic Liverworts in Montane Forests of Uganda.

We studied the influence of regional and local variables on the liverwort diversity within natural forest vegetation of Uganda to contribute to our understanding of the mechanisms and processes determining species richness. To this end, we compared the species richness distribution patterns of epiphytic and non-epiphytic liverworts (Marchantiophytina) in 24 plots in the forests of four Ugandan national parks. We recorded a total of 119 species and subspecies from 18 families, including 16 new species records for the country. We used generalized linear models (GLMs) and the relative variable importance of regional and local climatic and environmental variables to assess their respective impact on the species diversity. We found that the richness patterns of total and epiphytic richness were largely driven by regional climatic factors related to temperature and water-availability. In contrast, species diversity of non-epiphytic and rare species was additionally strongly determined by local-scale microhabitat factors such as height of forest canopy and slope inclination, reflecting the availability of suitable microhabitats. We conclude that macroclimatic variables perform well in predicting epiphytic liverwort richness, whereas the adequate prediction of non-epiphytic richness requires site-specific variables. Also, we propose that richness of epiphytic liverworts will be impacted more directly by climate change than richness of non-epiphytic and rare species.

Reference grass evapotranspiration with reduced data sets: Parameterization of the FAO Penman-Monteith temperature approach and the Hargeaves-Samani equation using local climatic variables

The computation of the grass reference evapotranspiration with the FAO56 Penman-Monteith equation (PM-ETo) requires data on maximum and minimum air temperatures (Tmax, Tmin), actual vapour pressure (ea), shortwave solar radiation (Rs), and wind speed at 2 m height (u2). Nonetheless, related datasets are often not available, are incomplete, or have uncertain quality. To overcome these limitations, several alternatives were considered in FAO56, while many other procedures were tested and proposed in very numerous papers. The present study reviews the computational procedures relative to predicting the missing variables from temperature, i.e., the PM temperature approach (PMT), and estimating ETo with the Hargreaves-Samani (HS) equation. For the PMT approach, procedures refer to predicting: (a) the dew point temperature (Tdew) from the minimum or the mean air temperature; (b) shortwave solar radiation (Rs) from the air temperature difference (TD = Tmax-Tmin) combined with a calibrated radiation adjustment coefficient (kRs); and (c) wind speed (u2) using a default value or a regional or local average. The adequateness of computing Tdew from air temperature was reassessed and the preference for using an average u2 has been defined. To ease the estimation of Rs, for the PMT approach and the coefficient of the HS equation, multiple linear regression equations for predicting kRs were developed using local averages of the temperature difference (TD), relative humidity (RH) and wind speed as independent variables. All variables were obtained from the Mediterranean set of CLIMWAT climatic data. Two types of kRs equations were developed: climate-focused equations specific to four climate types - humid, sub-humid, semi-arid, and hyper-arid and arid -, and a global one, applicable to any type of climate. The usability of the kRs equations for the PMT and HS methods was assessed with independent data sets from Bolivia, Inner Mongolia, Iran, Portugal and Spain, covering a variety of climates, from hyper-arid to humid. With this purpose, ETo estimated with PMT and HS (ETo PMT and ETo HS) were compared with PM-ETo computed with full data sets to evaluate the usability of the kRs equations. Adopting the climate-focused kRs equations with ETo PMT, the RMSE averaged 0.59, 0.64, 0.65 and 0.72 mm d−1 for humid, sub-humid, semi-arid, and arid and hyper-arid climates, respectively, while the RMSE values relative to ETo HS when using the respective climate-focused kRs equations averaged 0.58, 0.60, 0.60 and 0.69 mm d−1 for the same climates. These results are similar to those obtained with the kRs global equation. The accuracy of the PMT approach when using the kRs equations was also evaluated when one, two, or all three Tdew, Rs and u2 variables are missing and the resulting goodness-of-fit indicators demonstrated the advantage of the combined use of observed and estimated weather variables. The usability of the kRs equations for an efficient parameterization of both the PMT approach and the HS equation is demonstrated with similar performance of PMT and HS procedures for a variety of climates. Because the ETo HS results depend almost linearly on temperature, the PMT approach, using estimates of the weather variables, is able to mitigate those temperature impacts, which trends may be contrary to those of other variables that determine ETo. The clear advantage of the PMT approach is that it allows using the available weather data in combination with estimates of the missing variables, which provides for more accurate ETo computations.

Future shift in winter streamflow modulated by the internal variability of climate in southern Ontario

Abstract. Fluvial systems in southern Ontario are regularly affected by widespread early-spring flood events primarily caused by rain-on-snow events. Recent studies have shown an increase in winter floods in this region due to increasing winter temperature and precipitation. Streamflow simulations are associated with uncertainties mainly due to the different scenarios of greenhouse gas emissions, global climate models (GCMs) or the choice of the hydrological model. The internal variability of climate, defined as the chaotic variability of atmospheric circulation due to natural internal processes within the climate system, is also a source of uncertainties to consider. Uncertainties of internal variability can be assessed using hydrological models fed by downscaled data of a global climate model large ensemble (GCM-LE), but GCM outputs have too coarse of a scale to be used in hydrological modeling. The Canadian Regional Climate Model Large Ensemble (CRCM5-LE), a 50-member ensemble downscaled from the Canadian Earth System Model version 2 Large Ensemble (CanESM2-LE), was developed to simulate local climate variability over northeastern North America under different future climate scenarios. In this study, CRCM5-LE temperature and precipitation projections under an RCP8.5 scenario were used as input in the Precipitation Runoff Modeling System (PRMS) to simulate streamflow at a near-future horizon (2026–2055) for four watersheds in southern Ontario. To investigate the role of the internal variability of climate in the modulation of streamflow, the 50 members were first grouped in classes of similar projected change in January–February streamflow and temperature and precipitation between 1961–1990 and 2026–2055. Then, the regional change in geopotential height (Z500) from CanESM2-LE was calculated for each class. Model simulations showed an average January–February increase in streamflow of 18 % (±8.7) in Big Creek, 30.5 % (±10.8) in Grand River, 29.8 % (±10.4) in Thames River and 31.2 % (±13.3) in Credit River. A total of 14 % of all ensemble members projected positive Z500 anomalies in North America's eastern coast enhancing rain, snowmelt and streamflow volume in January–February. For these members the increase of streamflow is expected to be as high as 31.6 % (±8.1) in Big Creek, 48.3 % (±11.1) in Grand River, 47 % (±9.6) in Thames River and 53.7 % (±15) in Credit River. Conversely, 14 % of the ensemble projected negative Z500 anomalies in North America's eastern coast and were associated with a much lower increase in streamflow: 8.3 % (±7.8) in Big Creek, 18.8 % (±5.8) in Grand River, 17.8 % (±6.4) in Thames River and 18.6 % (±6.5) in Credit River. These results provide important information to researchers, managers, policymakers and society about the expected ranges of increase in winter streamflow in a highly populated region of Canada, and they will help to explain how the internal variability of climate is expected to modulate the future streamflow in this region.

Temporal inventory of glaciers in the Suru sub-basin, western Himalaya: impacts of regional climate variability

Abstract. The importance of updated knowledge about the glacier extent and characteristics in the Himalaya cannot be overemphasized. Availability of precise glacier inventories in the latitudinally diverse western Himalayan region is particularly crucial. In this study we have created an inventory of the Suru sub-basin in the western Himalaya for the year 2017 using Landsat Operational Land Imager (OLI) data. Changes in glacier parameters have also been monitored from 1971 to 2017 using temporal satellite remote-sensing data and limited field observations. Inventory data show that the sub-basin has 252 glaciers covering 11 % of the basin, having an average slope of 25±6∘ (standard deviations have been italicized throughout the text) and dominantly north orientation. The average snow line altitude (SLA) of the basin is 5011±54 m a.s.l. with smaller (47 %) and cleaner (43 %) glaciers occupying the bulk area. Long-term climate data (1901–2017) show an increase in the mean annual temperature (Tmax⁡ and Tmin⁡) of 0.77 ∘C (0.25 and 1.3 ∘C) in the sub-basin, driving the overall glacier variability in the region. Temporal analysis reveals a glacier shrinkage of ∼6±0.02 %, an average retreat rate of 4.3±1.02 m a−1, debris increase of 62 % and a 22±60 m SLA increase in the past 46 years. This confirms their transitional response between the Karakoram and the Greater Himalayan Range (GHR) glaciers. Besides, glaciers in the sub-basin occupy two major ranges, the GHR and Ladakh Range (LR), and experience local climate variability, with the GHR glaciers exhibiting a warmer and wetter climate as compared to the LR glaciers. This variability manifests itself in the varied response of GHR and LR glaciers. While the GHR glaciers exhibit an overall rise in SLA (GHR: 49±69 m; LR: decrease of 18±50 m), the LR glaciers have deglaciated more (LR: 7 %; GHR: 6 %) with an enhanced accumulation of debris cover (LR: 73 %; GHR: 59 %). Inferences from this study reveal prevalence of glacier disintegration and overall degeneration, transition of clean ice to partially debris-covered glaciers, local climate variability and non-climatic (topographic and morphometric)-factor-induced heterogeneity in glacier response as the major processes operating in this region. The Shukla et al. (2019) dataset is accessible at https://doi.org/10.1594/PANGAEA.904131.

Changes of crop failure risks in the United States associated with large-scale climate oscillations in the Atlantic and Pacific Oceans

Regions that produce a large supply of agriculture commodities can be susceptible to crop failure, thus causing concern for global food security. The contiguous United States, as one of the major agricultural producers in the world, is influenced by several large-scale climate oscillations that contribute to climate variability: Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), El-Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Pacific-North American (PNA). Since local weather conditions are associated with these climate oscillations through teleconnections, they are potentially causing changes of crop failure risks. The objective of this study is to assess climate-induced changes of annual crop failure risks for maize and winter wheat from 1960 to 2016, by analyzing the associations of large-scale climate oscillations with the frequency of crop failure in the rainfed regions of the United States using a Bayesian approach. The analysis revealed that crop failure frequencies showed contrast spatial patterns and different extent under different climate oscillation phases. Among individual oscillations, the positive PNA and negative AMO resulted in the most substantial increase in maize and winter wheat crop failures over a high percentage of climate divisions, respectively. Among oscillation combinations, the positive AMO and negative PDO and the positive AMO and positive PDO resulted in the highest percentage of climate divisions experiencing significant increase of maize and winter wheat crop failures, respectively. Random forest models with climate oscillations accurately predicted probabilities of crop failure, with the inclusion of local surface climate variables decreased or increased the predictive accuracy, depending on regions. These results revealed the plausible drivers of long-term changes of U.S. crop failure risks and underscore the importance for improving climate oscillation forecasting for early warning of food insecurity.

Wintry habitat selection of the Zapallaren tree iguana (Liolaemus zapallarensis, Müller & Hellmich, 1933) and its abundance in Changa beach, Coquimbo, northern Chile

Urban development modifies the habitat of reptiles where we expect, the individuals to select available sites with the quality necessary for their permanence. The aim of this study was to determine the variables that favored the habitat selection and abundance of The Zapallaren Tree Iguana Liolaemus zapallarensis, an endemic species of Chile, during a winter season in Changa beach, Coquimbo, in northern Chile. Between June and September 2017, we made 30 random visits to 18 plots of 900 m2 each. We estimated a resource selection probability function for presence-absence and abundance data using local habitat (e.g. slope, distance from the protection wall to the sea at low tide, interior height of the wall, mean height of the vegetation, rocky surface, and vegetal surface) and climatic variables (temperature, atmospheric pressure, direction and wind speed, solar radiation, and mean cloudiness) as predictors. Vegetation cover was the most important habitat variable explaining the presence of L. zapallarensis. In addition, increase in cloudiness and wind speed decreased the probability of selection. Manly’s selectivity measure varied according to the established home ranges and the availability ratios within them. Finally, increase in cloudiness and wind speed decreased the abundance. Overall, our results show that the characteristics related to habitat and local climate influences the resource selection that favors the survival of reptiles. This work shows that beach sectors in urban contexts under anthropic pressure have important available resources that favor the presence and abundance of reptiles.

Anticipating urbanization-led land cover change and its impact on local climate using time series model: a study on Dhaka city

Urbanization-led changes in natural landscape often result in environmental degradation and subsequently contribute to local climate variability. Therefore, apart from global climate change, Dhaka city’s ongoing rapid urban growth may result in altering future local climate patterns significantly. This study explores transition relationships between urbanization (population), land cover, and climate (temperature) of Dhaka city beginning in 1975 through to forecast scenarios up to 2035. Satellite image, geographic, demographic, and climatic data were analyzed. Change in core urban land cover (area) was regarded as a function of population growth and was modeled using linear regression technique. The study developed and validated a time series (ARIMA) model for predicting mean maximum temperature change where (forecasted) land cover scenarios were regressors. Throughout the studied period, the city exhibited an increasing urbanization trend that indicated persistent growth of core urban land cover in future. As a result, the city’s mean maximum temperature was found likely to increase by around 1.5-degree Celsius during 2016–2035 on average from that of observed 1996–2015 period. It is expected that findings of this study may help in recognizing urbanization-led climate change easily, which is crucial to effective climate change management actions and urban planning.

Effects of Climate Variability on the Annual and Intra-annual Ring Formation of Pinus merkusii growing in Central Thailand

The research clarifies which climatic factors induce annual and intra-annual ring formation in merkus pine (Pinus merkusii) growing in the low lying plains of central Thailand and reconstructs the past climate by using climate modelling derived from climate-growth response. Not only are climate variations longer than a century in central Thailand explained, but the study also explores for the first time the variability in climate using the formation of intra-annual rings in Thai merkus pines. The tree-ring analysis of wood core samples indicated that the pine stand was more than 150 years old with the oldest tree being 191 years old. The annual variation in tree growth significantly correlated with local climate variables, the number of rainy days in each year (r=0.520, p<0.01) and the extreme maximum temperature in April (r=-0.377, p<0.01). The regional climate of the Equatorial Southern Oscillation in March (EQ_SOIMarch) also highly correlated with the pine growth (r=0.360, p<0.01). The climate reconstruction indicated a declining trend in the number of rainy days during the 20th century and a decline in the number of rainy days was observed during the first and second decades of the 21st century, respectively, while the past climate reconstruction of maximum temperature in April and EQ SOIMarch indicated a decline during the previous century and an increase in this century. A multiple regression analysis indicated that the extreme maximum temperature, which declined at the beginning of the wet season and increased around the transitional period of the late rainy and the cold seasons, influenced the formation of intra-annual rings (r2=40.5%, p<0.05). It can be summarized that the number of rainy days increasing in each year associated with the declining temperature at the beginning of the wet season indicated a rapid growth in P. merkusii, while the anomalous temperature declining at the beginning and increasing at the end of the wet season was the main factor inducing the intra-annual ring formation. Therefore the activity of forest and planation management, especially in the watering at the beginning of the wet season when anomalous increased temperature occurred, shall be specified in the forest management plan in order to increase annual pine growth and wood formation.

Factors Shaping Breeding Phenology in Birds: An Assessment of Two Sympatric Acrocephalus Warblers with Different Life Histories

Timing of reproduction is a critical life-history trait and implies major fitness consequences. Differences in life history strategies can lead to different responses to the same environmental conditions even among closely related species. Investigating the factors affecting the timing of reproduction in closely related and sympatric species may help understanding the relationship between different life history traits and species-specific responses to ecological factors. We investigated the effects of season (photoperiod), local climatic variability and prey abundance on the breeding season of two sympatric insectivorous birds that differ in the timing of reproduction and moult and have different migration strategies: the Moustached Warbler Acrocephalus melanopogon and the Eurasian Reed-warbler Acrocephalus scirpaceus. During a five-year period, breeding phenology was determined by examining bird incubation patches during standardised captures and food availability was assessed by invertebrate sampling. Time, mean temperatures and the abundance of some prey taxa were inter-correlated and all contributed to influence the breeding phenology of both species according to partial least squares regression analysis. Besides some interspecific differences in the effect of environmental factors on the breeding phenology, we found strong similarities between the patterns observed in the two warblers. This suggests that, in spite of interspecific differences in life history, the ecological mechanisms shaping reproduction phenology are similar in the two warblers and the same environmental factors are involved in determining the timing of their reproduction.—Ceresa, F., Belda, E.J., Brambilla, M., Gómez, J., Mompó, C. & Monrós, J.S. (2020). Factors shaping breeding phenology in birds: an assessment of two sympatric Acrocephalus warblers with different life histories. Ardeola, 67: 371-385.

Using proverbs to study local perceptions of climate change: a case study in Sierra Nevada (Spain)

Local communities’ dependence on the environment for their livelihood has guided the development of indicators of local weather and climate variability. These indicators are encoded in different forms of oral knowledge. We explore whether people recognize and perceive as accurate one type of such forms of oral knowledge, climate-related proverbs. We conducted research in the Alta Alpujarra Occidental, Sierra Nevada, Spain. We collected locally recognized proverbs and classified them according to whether they referred to the climatic, the physical, or the biological system. We then conducted questionnaires (n = 97) to assess informant’s ability to recognize a selection of 30 locally relevant proverbs and their perception of the accuracy of the proverb. Climate-related proverbs are abundant and relatively well recognized even though informants consider that many proverbs are not accurate nowadays. Although proverbs’ perceived accuracy varied across informant’s age, level of schooling, and area of residence, overall proverb’s lack of reported accuracy goes in line with climate change trends documented by scientists working in the area. While our findings are limited to a handful of proverbs, they suggest that the identification of mismatches and discrepancies between people’s reports of proverb (lack of) accuracy and scientific assessments could be used to guide future research on climate change impacts.

Exploring the Combined Effect of Urbanization and Climate Variability on Urban Vegetation: A Multi-Perspective Study Based on More than 3000 Cities in China

More than 3000 cities in China were used to study the effect of urbanization and local climate variability on urban vegetation across different geographical and urbanization conditions. The national scale estimation shows that China’s urban vegetation depicts a trend of degradation from 2000 to 2015, especially in developed areas such as the Yangtze River Delta. According to the panel models, the increase of precipitation (PREC), solar radiation (SRAD), air temperature (TEMP), and specific humidity (SHUM) all enhance urban vegetation, while nighttime light intensity (NLI), population density (POPDEN), and fractal dimension (FRAC) do the opposite. The effects change along the East–West gradient; the influences of PREC and SHUM become greater, while those of TEMP, SRAD, NLI, AREA, and FRAC become smaller. PREC, SHUM, and SRAD play the most important roles in Northeast, Central, and North China, respectively. The role of FRAC and NLI in East China is much greater than in other regions. POPDEN remains influential across all altitudes, while FRAC affects only low-altitude cities. NLI plays a greater role in larger cities, while FRAC and POPDEN are the opposite. In cities outside of the five major urban agglomerations, PREC has a great influence while the key factors are more diversified inside.

Sub-monthly evolution of the Caribbean Low-Level Jet and its relationship with regional precipitation and atmospheric circulation

The summer spatial structure and sub-monthly temporal evolution of one of the key dynamical features of Central American climate, the Caribbean Low-Level Jet (CLLJ), is investigated by means of extended empirical orthogonal functions (EEOFs). The Caribbean 925-hPa zonal wind from the CFSR reanalysis for the period 1979 – 2010 is used for the analysis. This approach reveals new insights into the dynamical processes and spatio-temporal evolution of the CLLJ summer intensification, and through lead and lag linear regressions, significant climate links in the broader Caribbean region are identified. The results show that the CLLJ generates significant precipitation and temperature responses with a distinct temporal evolution over the Caribbean-Atlantic domain to that over the tropical Pacific, which hints at different underlying controlling mechanisms over these two large-scale regions. These anomalies are linked with the mid and upper tropospheric circulation, where a vertical cell over the Caribbean (ascending at the jet exit and subsiding at its entrance) varies in phase with large-scale divergence over the Pacific Ocean. Extratropical hemispheric-wide waves and the weakening of a thermal low in northeast Mexico-central US are identified as potential triggering factors for the CLLJ summer intensification. Two leading modes of tropical variability, El Niño Southern Oscillation and the Madden-Julian Oscillation, are found to modulate the CLLJ by intensifying it and prolonging its life cycle. Details of the underlying mechanisms are provided. These results help to advance the understanding of the processes that modulate local climate variations, which is an important issue in view of the rapid climate change the region is undergoing.

New specimen of Dinodontosaurus (Therapsida, Anomodontia) from west-central Argentina (Chañares Formation) and a reassessment of the Triassic Dinodontosaurus Assemblage Zone of southern South America

The Chañares Formation is known worldwide for its diverse tetrapod assemblage, including representatives of proterochampsid archosauromorphs, early offshoots of the crocodilian lineage, precursors of the dinosaurian lineage, and dicynodont and cynodont therapsids. The dicynodont Dinodontosaurus, originally described nearly 80 years ago, is the most common dicynodont therapsid in the assemblage. Here we present a new specimen of this taxon, focusing on the basicranium structure using 3D modeling and digital segmentation of the individual bones to provide a novel description of this region of the skull. Among the newly-recognized anatomical structures are a rod-like pila antotica in the prootic, the presence of a dorsal conical projection of the parasphenoid, and the anterior extension of the supraoccipital between the prootic and the parietal. The Chañares tetrapod assemblage was historically correlated with the Dinodontosaurus Assemblage Zone of Southern Brazil, originally due to the presence of this large dicynodont, as well as the cynodont Massetognathus, and more recently by absolute dates of the fossil-bearing strata. Both assemblages are similar in diversity and taxonomy, particularly in their non-mammalian therapsids; however their body-size distributions are very different. These differences in body-size are likely not reflecting a taphonomic bias but local variations in climate that promoted more open landscapes in southern Brazil in contrast to western Argentina, where more humid conditions prevailed during the early Late Triassic.

Modelling of Land-Use/Land-Cover Change and Its Impact On Local Climate of Klang River Basin

Land-use and land-cover (LULC) change has significant effect on local climate variables such as temperature and rainfall as it alters the energy budget, water budget and atmospheric variables. Past studies have shown urban areas can result in high temperature and alter rainfall amounts and intensity. This study therefore looks at spatio-temporal change in land-use/land-cover, and trends in precipitation and temperature for the Klang river basin. The aim of the study is to determine the effects of these changes in land-use on precipitation and temperature trends. Precipitation data was tested using the Mann-Kendall statistics test. Precipitation amount and two precipitation indices (simple day intensity index (SDII) and R95p) for the full year period and both the monsoons and inter-monsoon periods are tested. For temperature, land surface temperature maps of the study area for the years 1999, 2006 and 2017 was created from the thermal band of the images. Remote sensing is used for modelling spatio-temporal changes in LULC of Klang river basin using multi-temporal LandSat dataset (1999, 2006, and 2017). The LULC modelling shows an increase in urban area of 51.5% from 1999-2017, and decrease in natural vegetation 17.6% and cultivated land 35%. The results of precipitation analysis show a mixture of both positive (increasing) and negative (decreasing) trends for stations in the study area, and for temperature there is an increase of 10.1 °C in maximum temperature from 1999-2017. The correlation test shows a positive correlation between precipitation and temperature, but the relationship is not significant. The LULC change has significant impact on temperature; however, the increasing temperature has an insignificant positive correlation with rainfall. This could indicate that the change in rainfall is mostly due to other factors.

Bird nest orientation and local temperature: an analysis over three decades.

Different studies around the world have shown that the orientation of birds' nests depends on local climate variables such as temperature, wind, and rainfall (e.g. Facemire et al. 1990, Wiebe 2001, Burton 2007, Hartman and Oring, 2003, Landler et al. 2014, Schaaf et al. 2018). These local climate variables, in particular temperature, may cause variations in nest orientation between different geographical areas. For example, in temperate regions, bird species that build enclosed nests tend to orient their nests towards the sun to increase the temperature inside the nests. On the other hand, in tropical regions, the nest entrances are directed away from the sun to avoid heating (Wiebe 2001, Burton 2007, Schaaf et al. 2018). In this way, birds achieve thermal conditions more conducive to incubation and offspring growth (McGowan et al. 2004, Mainwaring et al. 2014).

Experimental evidence indicates variable responses to forest disturbance and thermal refugia by two plethodontid salamanders

Understanding how natural and anthropogenic disturbances affect sensitive species is critical to support conservation programs as land use activities and climatic conditions change. Forest management provides a range of ecosystem services to expanding human populations including production of substantial amounts of woody biomass, thereby reducing area under management and increasing opportunity for conservation designations. However, relatively little experimental information is available to describe how manipulating habitat at multiple scales may affect spatial and temporal variation in populations of climate-sensitive forest taxa. We conducted a Before-After Control-Impact experiment over seven years to evaluate responses of two species of Plethodontid salamanders in operational treatment (harvest, replanting, and herbicide application) and control units, Oregon, USA. In addition, we capitalized on existing variation in downed wood size and accounted for potential behavioral responses to evaluate the thermal refugia hypothesis. For Oregon slender salamanders (Batrachoseps wrighti), mean plot-level occupancy (90% CRI) was increased an estimated 11% (1.11; 0.62–2.1) and estimated mean abundance reduced 16% (0.84; 0.54–1.4) post-harvest. For Ensatina (Ensatina eschscholtzii), mean occupancy was reduced an estimated 80% (0.20; 0.08–0.47) and estimated mean abundance reduced 63% (0.37; 0.22–0.65) post-harvest. We found strong evidence of positive associations for both species with downed wood amount. As predicted, we found ambient temperatures to be higher in harvest than control units. Also, internal downed wood temperatures were warmer in harvested units, suggesting these structures may not have provided adequate thermal refugia. Application of an experimental framework provided evidence about both stand and structure level responses to active management. Habitat structures did not appear to buffer against substantial variation in local climate but evidence was equivocal about importance of these structures to population retention. Monitoring of recruitment and retention of downed wood through subsequent rotations can provide critical information to reduce trade-offs between wood production and conservation of climate sensitive taxa.