Long-term rainfall trends in Serra da Mantiqueira Environmental Protection Area, southeast Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Trends in Mean Annual Streamflows in Serra da Mantiqueira Environmental Protection Area

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A quantitative state and transition model for the Mitchell grasslands of central western Queensland

Concerns of reduced productivity and land degradation in the Mitchell grasslands of central western Queensland were addressed through a range monitoring program to interpret condition and trend. Botanical and eclaphic parameters were recorded along piosphere and grazing gradients, and across fenceline impact areas, to maximise changes resulting from grazing. The Degradation Gradient Method was used in conjunction with State and Transition Models to develop models of rangeland dynamics and condition. States were found to be ordered along a degradation gradient, indicator species developed according to rainfall trends and transitions determined from field data and available literature. Astrebla spp. abundance declined with declining range condition and increasing grazing pressure, while annual grasses and forbs increased in dominance under poor range condition. Soil erosion increased and litter decreased with decreasing range condition. An approach to quantitatively define states within a variable rainfall environment based upon a time-series ordination analysis is described. The derived model could provide the interpretive framework necessary to integrate on-ground monitoring, remote sensing and geographic information systems to trace states and transitions at the paddock scale. However, further work is needed to determine the full catalogue of states and transitions and to refine the model for application at the paddock scale.

Estimation of the extreme flash flood evolution in Barcelona county from 1351 to 2005

Every year, flash floods cause economic losses and major problems for undertaking daily activity in the Catalonia region (NE Spain). Sometimes catastrophic damage and casualties occur. When a long term analysis of floods is undertaken, a question arises regarding the changing role of the vulnerability and the hazard in risk evolution. This paper sets out to give some information to deal with this question, on the basis of analysis of all the floods that have occurred in Barcelona county (Catalonia) since the 14th century, as well as the flooded area, urban evolution, impacts and the weather conditions for any of most severe events. With this objective, the identification and classification of historical floods, and characterisation of flash-floods among these, have been undertaken. Besides this, the main meteorological factors associated with recent flash floods in this city and neighbouring regions are well-known. On the other hand, the identification of rainfall trends that could explain the historical evolution of flood hazard occurrence in this city has been analysed. Finally, identification of the influence of urban development on the vulnerability to floods has been carried out. Barcelona city has been selected thanks to its long continuous data series (daily rainfall data series, since 1854; one of the longest rainfall rate series of Europe, since 1921) and for the accurate historical archive information that is available (since the Roman Empire for the urban evolution). The evolution of flood occurrence shows the existence of oscillations in the earlier and later modern-age periods that can be attributed to climatic variability, evolution of the perception threshold and changes in vulnerability. A great increase of vulnerability can be assumed for the period 1850¿1900. The analysis of the time evolution for the Barcelona rainfall series (1854¿2000) shows that no trend exists, although, due to changes in urban planning, flash-floods impact has altered over this time. The number of catastrophic flash floods has diminished, although the extraordinary ones have increased.

Impacts of 20th century aerosol emissions on the South Asian monsoon in the CMIP5 models

Comparison of single-forcing varieties of 20th century historical experiments in a subset of models from the Fifth Coupled Model Intercomparison Project (CMIP5) reveals that South Asian summer monsoon rainfall increases towards the present day in Greenhouse Gas (GHG)-only experiments with respect to pre-industrial levels, while it decreases in anthropogenic aerosol-only experiments. Comparison of these single-forcing experiments with the all-forcings historical experiment suggests aerosol emissions have dominated South Asian monsoon rainfall trends in recent decades, especially during the 1950s to 1970s. The variations in South Asian monsoon rainfall in these experiments follows approximately the time evolution of inter-hemispheric temperature gradient over the same period, suggesting a contribution from the large-scale background state relating to the asymmetric distribution of aerosol emissions about the equator. By examining the 24 available all-forcings historical experiments, we show that models including aerosol indirect effects dominate the negative rainfall trend. Indeed, models including only the direct radiative effect of aerosol show an increase in monsoon rainfall, consistent with the dominance of increasing greenhouse gas emissions and planetary warming on monsoon rainfall in those models. For South Asia, reduced rainfall in the models with indirect effects is related to decreased evaporation at the land surface rather than from anomalies in horizontal moisture flux, suggesting the impact of indirect effects on local aerosol emissions. This is confirmed by examination of aerosol loading and cloud droplet number trends over the South Asia region. Thus, while remote aerosols and their asymmetric distribution about the equator play a role in setting the inter-hemispheric temperature distribution on which the South Asian monsoon, as one of the global monsoons, operates, the addition of indirect aerosol effects acting on very local aerosol emissions also plays a role in declining monsoon rainfall. The disparity between the response of monsoon rainfall to increasing aerosol emissions in models containing direct aerosol effects only and those also containing indirect effects needs to be urgently investigated since the suggested future decline in Asian anthropogenic aerosol emissions inherent to the representative concentration pathways (RCPs) used for future climate projection may turn out to be optimistic. In addition, both groups of models show declining rainfall over China, also relating to local aerosol mechanisms. We hypothesize that aerosol emissions over China are large enough, in the CMIP5 models, to cause declining monsoon rainfall even in the absence of indirect aerosol effects. The same is not true for India.

Recent observed and simulated changes in precipitation over Africa

Multiple observational data sets and atmosphere-only simulations from the Coupled Model Intercomparison Project Phase 5 are analyzed to characterize recent rainfall variability and trends over Africa focusing on 1983–2010. Data sets exhibiting spurious variability, linked in part to a reduction in rain gauge density, were identified. The remaining observations display coherent increases in annual Sahel rainfall (29 to 43 mm yr−1 per decade), decreases in March–May East African rainfall (−14 to −65 mm yr−1 per decade), and increases in annual Southern Africa rainfall (32 to 41 mm yr−1 per decade). However, Central Africa annual rainfall trends vary in sign (−10 to +39 mm yr−1 per decade). For Southern Africa, observed and sea surface temperature (SST)-forced model simulated rainfall variability are significantly correlated (r~0.5) and linked to SST patterns associated with recent strengthening of the Pacific Walker circulation.

Precipitation variability in Sao Paulo State, Brazil

The State of Sao Paulo is the richest in Brazil, responsible for over 30% of the Brazilian gross rate. It has a population of around 30 million and its economy is based on agriculture and industrial products. Any change in climate can have a profound influence on the socio-economics of the State. In order to determine changes in total and extreme rainfall over Sao Paulo State, climate change indices derived from daily precipitation data were calculated using specially designed software. Maps of trends for a subset of 59 rain gauge stations were analysed for the period 1950-1999 and also for a subset of this period, 1990-1999, representing more recent climate. A non-parametric Mann-Kendall test was applied to the time series. Maps of trends for six annual precipitation indices (annual total precipitation (PRCPTOT), very heavy precipitation days (R20mm), events greater than the 95th percentile (R95p), maximum five days precipitation total (RX5day), the length of the largest wet spell (CWD) and the length of the largest dry spell (CDD)) were analysed for the entire period. These exhibited statistically significant trends associated with a wetter climate. A significant increase in PRCPTOT, associated with very heavy precipitation days, were observed at more than 45% of the rain gauge stations. The Mann-Kendall test identified that the positive trend in PRCPTOT is possibly related to the increase in the R95p and R20mm indices. Therefore, the results suggest that there has been a change in precipitation intensity. In contrast, the indices for the more recent shorter time series are significantly different to the longer term indices. The results indicate that intense precipitation is becoming concentrated in a few days and spread over the period when the CDD and R20mm indices show positive trends, while negative ones are seen in the RX5day index. The trends found could be related to many anthropogenic aspects such as biomass burning aerosols and land use.

Las inundaciones en la ciudad de La Plata. Su análisis en relación con las precipitaciones durante las últimas décadas del siglo XX

En la cuenca del Plata, durante las últimas dos décadas del siglo XX, se desarrollaron importantes inundaciones producto de los cambios ocurridos en el sistema climático global y, como el área del Gran La Plata (partidos de Berisso, Ensenada y La Plata) no escapa a este problema, se ha tomado como caso para nuestra investigación. Se analiza la distribución temporal de las precipitaciones en la ciudad de La Plata (provincia de Buenos Aires, Argentina), para el período comprendido entre las últimas décadas del siglo XX y la actualidad. En el Gran La Plata el problema de las inundaciones es resultado de la confluencia de tres factores: las precipitaciones (sobre todo cuando se producen con gran intensidad), las napas freáticas que han aumentado su presión hacia arriba por haberse elevado y la sudestada que provoca la crecida de los ríos. El estudio se realizó considerando los valores diarios de precipitación disponibles para la localidad, brindados por estación meteorológica La Plata Aero, dependiente del Servicio Meteorológico Nacional, y los datos de inundaciones obtenidos del diario "El Día", de circulación local. La variación temporal se estudió a escala anual y mensual, detectándose cambios en monto e intensidad que, además de responder al incremento de las precipitaciones acaecido en la pradera pampeana en las últimas décadas, son una llamada de atención para la planificación de futuros emprendimientos en la ciudad y toma de decisiones en el caso de eventos hidrológicos extremos, como es el caso de las inundaciones. En los resultados de este análisis se observó que las inundaciones en la década 1971 - 1980 fueron 25, y que se incrementaron a 78 en la última década estudiada (1991-2000).

Las inundaciones en la ciudad de La Plata. Su análisis en relación con las precipitaciones durante las últimas décadas del siglo XX

En la cuenca del Plata, durante las últimas dos décadas del siglo XX, se desarrollaron importantes inundaciones producto de los cambios ocurridos en el sistema climático global y, como el área del Gran La Plata (partidos de Berisso, Ensenada y La Plata) no escapa a este problema, se ha tomado como caso para nuestra investigación. Se analiza la distribución temporal de las precipitaciones en la ciudad de La Plata (provincia de Buenos Aires, Argentina), para el período comprendido entre las últimas décadas del siglo XX y la actualidad. En el Gran La Plata el problema de las inundaciones es resultado de la confluencia de tres factores: las precipitaciones (sobre todo cuando se producen con gran intensidad), las napas freáticas que han aumentado su presión hacia arriba por haberse elevado y la sudestada que provoca la crecida de los ríos. El estudio se realizó considerando los valores diarios de precipitación disponibles para la localidad, brindados por estación meteorológica La Plata Aero, dependiente del Servicio Meteorológico Nacional, y los datos de inundaciones obtenidos del diario "El Día", de circulación local. La variación temporal se estudió a escala anual y mensual, detectándose cambios en monto e intensidad que, además de responder al incremento de las precipitaciones acaecido en la pradera pampeana en las últimas décadas, son una llamada de atención para la planificación de futuros emprendimientos en la ciudad y toma de decisiones en el caso de eventos hidrológicos extremos, como es el caso de las inundaciones. En los resultados de este análisis se observó que las inundaciones en la década 1971 - 1980 fueron 25, y que se incrementaron a 78 en la última década estudiada (1991-2000).

Las inundaciones en la ciudad de La Plata. Su análisis en relación con las precipitaciones durante las últimas décadas del siglo XX

En la cuenca del Plata, durante las últimas dos décadas del siglo XX, se desarrollaron importantes inundaciones producto de los cambios ocurridos en el sistema climático global y, como el área del Gran La Plata (partidos de Berisso, Ensenada y La Plata) no escapa a este problema, se ha tomado como caso para nuestra investigación. Se analiza la distribución temporal de las precipitaciones en la ciudad de La Plata (provincia de Buenos Aires, Argentina), para el período comprendido entre las últimas décadas del siglo XX y la actualidad. En el Gran La Plata el problema de las inundaciones es resultado de la confluencia de tres factores: las precipitaciones (sobre todo cuando se producen con gran intensidad), las napas freáticas que han aumentado su presión hacia arriba por haberse elevado y la sudestada que provoca la crecida de los ríos. El estudio se realizó considerando los valores diarios de precipitación disponibles para la localidad, brindados por estación meteorológica La Plata Aero, dependiente del Servicio Meteorológico Nacional, y los datos de inundaciones obtenidos del diario "El Día", de circulación local. La variación temporal se estudió a escala anual y mensual, detectándose cambios en monto e intensidad que, además de responder al incremento de las precipitaciones acaecido en la pradera pampeana en las últimas décadas, son una llamada de atención para la planificación de futuros emprendimientos en la ciudad y toma de decisiones en el caso de eventos hidrológicos extremos, como es el caso de las inundaciones. En los resultados de este análisis se observó que las inundaciones en la década 1971 - 1980 fueron 25, y que se incrementaron a 78 en la última década estudiada (1991-2000).

XRF-scanned elemental concentrations from sediment cores off Peru

We present a high-resolution marine record of sediment input from the Guayas River, Ecuador, that reflects changes in precipitation along western equatorial South America during the last 18ka. We use log (Ti/Ca) derived from X-ray Fluorescence (XRF) to document terrigenous input from riverine runoff that integrates rainfall from the Guayas River catchment. We find that rainfall-induced riverine runoff has increased during the Holocene and decreased during the last deglaciation. Superimposed on those long-term trends, we find that rainfall was probably slightly increased during the Younger Dryas, while the Heinrich event 1 was marked by an extreme load of terrigenous input, probably reflecting one of the wettest period over the time interval studied. When we compare our results to other Deglacial to Holocene rainfall records located across the tropical South American continent, different modes of variability become apparent. The records of rainfall variability imply that changes in the hydrological cycle at orbital and sub-orbital timescales were different from western to eastern South America. Orbital forcing caused an antiphase behavior in rainfall trends between eastern and western equatorial South America. In contrast, millennial-scale rainfall changes, remotely connected to the North Atlantic climate variability, led to homogenously wetter conditions over eastern and western equatorial South America during North Atlantic cold spells. These results may provide helpful diagnostics for testing the regional rainfall sensitivity in climate models and help to refine rainfall projections in South America for the next century.

Long term trends of seasonal and monthly rainfall in different intensity ranges over Indian subcontinent

In general Indian summer monsoon rainfall did not show any significant trend in all Indian summer monsoon rainfall series, however, it was reported that the ISMR is subjected to spatial trends. This paper made an attempt to bring out long term trends of different intensity classes of summer monsoon rainfall in different regions of Indian subcontinent. The long term trend of seasonal and monthly rainfall were also made using the India Meteorological Department gridded daily rainfall data with a spatial resolution of 1° × 1° latitude-longitude grid for the period from 1st January, 1901 to 31st December, 2003. The summer monsoon rainfall shows an increasing trend in southeast, northwest and northeast regions, whereas decreasing trend in the central and west coastal regions. In monthly scale, July rainfall shows decreasing trend over west coastal and central Indian regions and significant increasing trend over northeast region at 0.1% significant level. During the month August, decreasing trend is observed in the west coastal stations at 10% significant level. In most of the stations, mean daily rainfall shows an increasing trend for low and very high intense rainfall. For the moderate rainfall, the trend is different for different regions. In the central and southern regions the trend of moderate and moderately high classes show increasing trend. And for the high and very high intensity classes, the trend is decreasing significantly. In the northeastern regions, above 10 mm/day rainfall shows significantly increasing trend with 0.1% significant level.

Long-term Trends in Magnitude and Frequency of Extreme Rainfall Events in Florida

This study computed trends in extreme precipitation events of Florida for 1950-2010. Hourly aggregated rainfall data from 24 stations of the National Climatic Data Centre were analyzed to derive time-series of extreme rainfalls for 12 durations, ranging from 1 hour to 7 day. Non-parametric Mann-Kendall test and Theil-Sen Approach were applied to detect the significance of trends in annual maximum rainfalls, number of above threshold events and average magnitude of above threshold events for four common analysis periods. Trend Free Pre-Whitening (TFPW) approach was applied to remove the serial correlations and bootstrap resampling approach was used to detect the field significance of trends. The results for annual maximum rainfall revealed dominant increasing trends at the statistical significance level of 0.10, especially for hourly events in longer period and daily events in recent period. The number of above threshold events exhibited strong decreasing trends for hourly durations in all time periods.

Mark-recapture may reveal more about ecology than about population trends: Demography of a threatened ghost bat (Macroderma gigas) population

Since European settlement in Australia, the geographical range of ghost bats (Macroderma gigas) has contracted northwards. Ghost bats are thought to occur in disjunct populations with little interpopulation migration, raising concerns over the current status and future viability of the southernmost colony, which has also been threatened by mining activity. To address these concerns, demographic parameters of the southernmost colony were estimated from a mark-recapture study conducted during 1975-1981. Female bats gave birth to a single young in late spring, but only 40% (22-70%, 95% CI) of females bred in their second year, increasing to 93% (87-97%, 95% CI) for females greater than or equal to 2 years old. Sixty-five percent of juveniles caught were female. Annual adult survival ranged between 0.57-0.77 for females and 0.43-0.66 for males, and was lowest over winter-spring and greatest in autumn-winter. Juvenile survival for the first year ranged between 0.35-0.46 for females and 0.29-0.42 for males. Adult survival varied among seasons, was negatively associated with rainfall, but was not associated with temperature beyond being lower in late winter. Poor survival may result from the inferior daytime roosts that bats must use if water seepage forces them to leave their normal roosts. Although these age-specific rates of fecundity and survival suggested a declining population, mark-recapture estimates of the population trend indicated stability over the study period. Counts at daytime roosts also suggested a population decline, but were considered unreliable because of an increasing tendency of bats to avoid detection. It is therefore likely that some assumptions in estimating survival were violated. These results provide a caution against the uncritical use of population projections derived from mark-recapture estimates of demographic parameters, and the use of untested indices as the basis for conservation decisions.

Spatial and seasonal trends of a natural population of Biomphalaria occidentalis in northeastern Argentina

This study aims to analyze the age of a population of Biomphalaria occidentalis on a pound of Riachuelo river basin, wich is one of the three most important Middle Paraná river affluents in Corrientes province. Samples were drawn from three stations, were spatial and temporal numerical variations of the snail, as well as its relation with different environmental parameters, mainly temperature, rainfall, pH and conductivity, were analyzed. Snail abundance is given in number of individuals/hour. The differences between the three sampling stations, estimated by nonparametric tests, was nonsignificant. A relative scale to the greatest shell diameter was employed to build the age pyramids. Temporal fluctuations of snail abundance correlated negatively with the highest monthly accumulated temperatures (P < 0.05). Although different floristic compositions were observed at the three stations, no significant numerical variations were detected in B. occidentalis spatial distribution. Reproductive activity took place between March-April and November with overlapping cohort system. During summer (December-Febuary) mortality increased along with temperature and reproductive activity was not evident.