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A high resolution atmospheric modelling study was done for a 20-year recent historical period. The dynamic downscaling approach adopted used the Max Planck Institute Earth System Model (MPI-ESM) to drive the WRF running in climate mode. Three online nested domains were used covering part of the North Atlantic and Europe, with a resolution 81 km, and reaching 9 km in the innermost domain which covers the Iberian Peninsula. This paper presents the validation of the WRF configuration, which is based on historic simulations between 1986 and 2005 and observational datasets of near surface temperature and precipitation for the same period. The validation was done in terms of comparison of probability distributions between model results and observations, as daily climatologies, spatially averaged inside subdomains obtained with cluster analysis of the observations, for each of the four seasons. In addition, Taylor diagrams are presented for each of the seasons and subdomains. This validation approach was repeated with the results of a new WRF simulation with the same parameterisations but forced by the ERA-Interim reanalysis. The capacity of the MPI-ESM driven WRF configuration to compare with observations and in a manner similar to the ERA-Interim driven WRF, ensures the capacity of the configuration for climate and climate change studies. Considering the difficulty to simulate extremes in long term simulations, the results showed a comfortable comparison of both models (forced by climate model and reanalysis results) with observations. This provides us confidence on the continuity of using the MPI-ESM driven WRF configuration for climate studies. [ABSTRACT FROM AUTHOR]

Abstract: Regional impact assessments of climate change on hydrological extremes require robust examinations of climate model simulations. The climate models may satisfy mean statistics but fail to reproduce extreme quantiles which are crucial for applications of climate change impact analysis on water resources. Through statistical analysis, this paper evaluates and inter-compares the performance of Global Climate Model (GCM) simulations for their ability to predict changes in hydrological extremes for given locations or catchments in the Nile basin. Two catchments were considered: Katonga and Ruizi catchments in the Lake Victoria basin. Models that differ significantly from the observed extremes were considered unreliable for impact assessments on hydrological extremes. A graphical approach (rainfall quantile/frequency analysis), which allows for easy spotting of discordant models, in combination with several statistics, was used to evaluate 18 GCM control simulations against observed rainfall data. Standard deviation, coefficient of variation and root mean squared error (about the mean) of the observed rainfall, were used to derive error margins against which GCM simulations were evaluated. Model results outside the error margins were considered inconsistent with the observed rainfall. Model inter-comparison was also carried out for the rainfall change projections till the 2050s and 2090s through analysis of perturbations and percentage changes based on A1B, A2, and B1 SRES scenarios. It is noted that the GCM outputs are more consistent in reproducing rainfall signatures at annual aggregation level than at monthly aggregation levels with tendency of overestimation of the rainfall depths but with significant variation among different GCM simulations. The GCMs perform better in reproducing rainfall frequency with higher return periods compared with lower return periods. Most of the GCMs perform better for the wet months than the drier months. The GCMs CGCM3.2a, CM3.O, CM4.1, PCM1, CGCM3.1T47, MIROC3.2.HIRES, CCSM3.0 and FGOALS, are the most inconsistent with the observed rainfall for both catchments. Good performing models are MK3.5, MK3.0, ECHAM5, CM2.1U.H2 and CM2.0. In general, most GCMs perform poorly for both catchments. This signals the need for significant improvements in the rainfall modelling of the climate models for the study region. There is no strong evidence to suggest that GCM performance improves with higher spatial resolution. Models which are highly inconsistent with other models in reproducing the observed rainfall are not necessarily inconsistent with other models in the future projections. Differences in projections for the A1B, B2, and B1 scenarios were found to be smaller than the differences between the GCM simulations. [Copyright &y& Elsevier]

Abstract: Human activity is known to have an important impact both in the radiation budget and the hydrological cycle. One particular aspect is the increase of anthropogenic aerosols due to changes in land use and industrial activity. However the relation between aerosols and precipitation is still far from being fully understood due to the complexity of the mechanisms involved and the lack of sound data. A multi-sensor approach, combining instruments meant to study aerosols and others meant at the study of precipitation, is required to get a better insight on this phenomenon. The International Research Centre for Telecommunications and Radar (IRCTR) has developed a meteorological radar called IDRA (IRCTR Drizzle Radar) aimed at obtaining high resolution temporal and spatial measurements of all sorts of precipitation including those non-detectable by standard meteorological radar like drizzle. The measurements obtained by the system, coupled with data obtained by other sensors placed in the Cabauw Experimental Site for Atmospheric Research (CESAR) observatory (Cabauw, The Netherlands), are expected to provide crucial information for a better characterization of these mechanisms. The information obtained can be used for a better spatial planning in order to reduce the impact of human activity in the climate. This paper describes the relevant characteristics of the system, its signal processing and the products obtained. [Copyright &y& Elsevier]

Abstract: Recent advances in GPS sensing technology and the availability of low-cost GPS receivers have allowed the continuous measurements of atmospheric water vapour in all weather conditions and on a global scale. This paper aims to analyze the variability of the Antarctic precipitable water vapour (PWV) observed by GPS receivers. In this contribution, the influence of terrestrial winds on the PWV variations is investigated where the climatology is extremely different from that in the Equatorial region. For this purpose, GPS and surface meteorological data for the period of 2003–2005 are analyzed. A significant diurnal variation in PWV was found over most of the sites with PWV difference increasing more than 0.50mm during summer compared to the winter times on a monthly analysis. Increase in Antarctic PWV evidently follows the variations of the surface temperature. In winter, the temperature increase will be lower by about 1°C and values of water vapour are 13% smaller than during summer months. The characteristics of Antarctic climate represented by the PWV variation show a seasonal dependence, higher (active) in summer and lower (inactive) in winter. It was found that the large decreases in the monthly mean PWV distribution were accompanied by strong winds above 10ms−1. [Copyright &y& Elsevier]

Abstract: In the framework of safe underground storage of radioactive waste in low-permeability layers, it is essential to evaluate the mobility of deep groundwaters over timescales of several million years. On these timescales, the environmental evolution of a repository should depend upon a range of natural processes that are primarily driven by climate and geomorphologic variations. In this paper, the response of the Paris basin groundwater system to variations in its hydrodynamic boundary conditions induced by past climate and geodynamic changes over the last five million years is investigated. A three-dimensional transient modelling of the Paris basin aquifer/aquitard system was developed using the code NEWSAM (Ecole des Mines de Paris, ENSMP). The geometry and hydrodynamic parameters of the model originate from a basin model, NEWBAS (ENSMP), built to simulate the geological history of the basin. Geomorphologic evolution is deduced from digital elevation model analysis, which allows to estimate river-valley incision and alpine surrection. Climate forcing results from palaeoclimate modelling experiments using the LMDz atmospheric general circulation model (Institut Pierre Simon Laplace) with a refined spatial resolution, for the present, the Last Glacial Maximum (21ka) and the Middle Pliocene Warmth (∼3Ma). The water balance is computed by the distributed hydrological model MODSUR (ENSMP). Results about the simulated evolution of piezometric heads in the system in response to the altered boundary conditions are presented, in particular in the vicinity of ANDRA’s Bure potential repository site within the Callovo-Oxfordian argillaceous layer. For the present, the comparison of head patterns between steady state and time dependent simulation shows little differences for aquifer layers close to the surface but suggests a transient state of the current system in the main aquitards of the basin and in the deep aquifers, characterized by abnormally low fluid potentials. The dependence of the boundary-induced transient effects on the hydraulic diffusivity is illustrated by means of a sensitivity study. [Copyright &y& Elsevier]

Abstract: By applying the wavelet formalism to sudden storm commencements and aa geomagnetic indices and solar total irradiation, as a proxy data for solar sources of climate-forcing, we have searched the signatures of those variables on the Northern Hemisphere surface temperature. We have found that cyclical behaviour in surface temperature is not clearly related to none of these variables, so we have suggested that besides them surface temperature might be related to Earth’s rotation rate variations. Also it has been suggested that in the long-term Earth’s rotation rate variations might be excited by geomagnetic storm time variations which, in turn, depends on solar activity. The study of these phenomena and its relationships is addressed in the present paper. With this purpose we perform an analysis of the evolution during the last 350years of the signals that conform the 11-year sunspot cycle maxima envelope for different time scales. The result is applied to analyze the relationship between long-term variations in sunspot number and excess of length of day; and to unearth the signature in surface temperature of this last from that of sudden storm commencement and aa geomagnetic indices and total solar irradiation. As solar dynamo experiments transient processes in all the time scales from seconds to centuries, Fourier analysis and its requirement for the process to be stationary is likely to produce spurious periodicities. We resort instead to wavelet formalism. By this representation we found that sunspot maxima envelope for the last 350years may be described by means of the superposition of two cycles – a decadal and a semi-secular one – and a secular trend. And that the changing amplitude and phase of the cycles are well reconstructed using the superposition of two wavelets with nearby periods. The strong temporal changes in amplitude of the cycles facilitate to detect its phase in a given time series. It is found that a strong semi-secular cycle in the sunspot maxima envelope that started during the 1705 chaotic transition having its maximum amplitude at the Dalton minimum, was mapped 94years later in Earth’s rotation rate and simultaneously in surface temperature. Also, there was a decrease (increase) of 0.022°C for each millisecond of decrease (increase) in the Earth’s rotation period for the semi-secular cycle as well as the secular trend. [Copyright &y& Elsevier]

Abstract: This paper investigates whether it is possible to find a solar signature in the current Earth’s climatic warming. The attempt seems audacious as, on one hand, solar output variability on the atmosphere is far to be understood, and on the other hand, there is evidence that most of the warming observed over the last 50 years can be attributed to human activities. However, series of the annual global average temperature, from 1861 up to now are available, showing periods of warming and cooling that are statistically significant. From recent findings, it is also known that solar irradiance shows a variability and can be modeled today with a good accuracy over the last century. The idea was to compare the likelihood linear trends shown in the climatic data with those of the irradiance, during same well defined time ranges. Changes from 1861 to 1975 show an unexpected remarkable correlation, whereas the period 1976–2000 completely deviates from the previous analysis. The 1861–1975 set of data supports the suggestion of an influence of solar irradiance on global climate, which was checked as a natural forcing: the response is found to be λ =0.46°C/Wm−2, a quite reasonable value, bearing in mind the imprecision in the irradiance modeling. This analysis is also discussed in the scope of other forcings and uncertainties in the data. [Copyright &y& Elsevier]

Abstract: Climate related issues, agro-metheorological ones included, are significant at European Union level due to their borderless nature. Their management is performed within different contexts, nevertheless the post important is the environmental aspect. However, from policy point of view one can differentiate between two major areas: regulation and research. The purpose of this paper is to give an overview of both research policy related aspects as well as achievements in the near past within the Framework Programme 4 and 5 for research. The research policy aspect is outlined by the broad fields incorporated in the base texts for which applications were requested, while the achievements are presented in terms of selected projects and their focused action field, i.e. what the factual response was against the formulated policy. [Copyright &y& Elsevier]

It has been identified that, long-term climatic changes (Pleistocene ice ages) have been caused by periodic changes in the distribution of incoming solar radiation due to the variations in the earth’s orbital geometry, that is the tilt, precision of equinoxes and eccentricity which take place with periodicity ranging from 41 to 9508 thousand years. However, it has been considered that the major potential mechanism of climate change over the next few hundred years will be anthropogenic green house gas warming up. A number of gases that occur naturally in the atmosphere in small quantities are known as ”greenhouse gases. Water vapour, carbon dioxide, ozone, methane, and nitrous oxide trap solar energy in much the same way as do the glass panes of a greenhouse or a closed automobile. This natural greenhouse gases effect has kept the earth’s atmosphere some 30°C hotter, than it would otherwise be, making it possible for humans to exist on earth. Human activities, however, are now raising the concentrations of these gases in the atmosphere and thus increasing their ability to trap energy. The enhanced greenhouse gas effect is expected to cause high temperature increase globally (1–3.5°C) and this will lead to an increase in precipitation in some regions while other regions will experience reduced precipitation (±20%). The impact of expected climate change will affect almost all the sectors of the human endeavor. However, the major purpose of this project is to evaluate the impact of climate change on hydrology and water resources and establish the appropriate adaptation strategies for Swaziland. The impact of climate change on hydrology and water resources will be evaluated using General Circulation Model results (rainfall, potential evapotranspiration, air temperature, etc.) as inputs to a rainfall runoff model. Water use in all the sectors of the human endeavor will be determined in order to establish the water availability given different climate change scenarios. Three catchments have been selected for this exercise. This paper therefore, presents the background information, objectives and significance of the study, literature review, methodology, data collection and processing. [Copyright &y& Elsevier]

The movement and distribution of water in the hydrologic cycle is affected by the level and type of land surface parameters. Thus accurate representation of the physical and biological features of the landscape within a watershed is required. A strong link exists between climate variability and the resulting changes in such land surface parameters as energy, land-cover and surface microclimates. Imagery from Landsat and other satellites provide land-cover and surface microclimate information with high temporal and spatial accuracy. This paper utilizes the land surface temperature (LST) derived from the thermal band of Landsat images and Normalized Difference Vegetation Index (NDVI) derived from its red and near-infrared bands to further improve land-cover and surface microclimate mapping. Remotely-sensed spatially distributed surface latent and sensible heat fluxes were also estimated. The study was conducted on 10,200 km2 watershed area of the Red River of the North Basin, North Dakota/Minnesota. Over the period of 1974–2002, seven images from Landsat Multispectral Scanner, Thematic Mapper and Enhanced Thematic Mapper plus sensors were used. Landsat images were processed using an unsupervised classification. Corrected LST and NDVI, which indicate a strong relationship with the land-cover data, were identified using scattergrams. Surface microclimate parameters (fractional vegetation cover, FVC and fractional impervious surface, FIS area) were estimated and their spatial and temporal distributions determined. Surface energy fluxes (latent and sensible heat) were assessed over space and time. The results indicate that vegetation cover (FVC > 0.5) increased from 7% in 1974 to 33% in 2002 due to cropland farming in the Red River Valley and an increase in impervious areas (FIS > 0.5) (by 79% from 1974 to 2001) attributed to the growing cities in the valley for the period of study. The study also indicated an increase in sensible and latent heat fluxes from 1998 to 2002 for areas classified as developed and cropland, respectively. Hydrograph analysis of the flow at Grand Forks gauging station also indicated runoff response of the basin has increased between 1993 and 2002 with all years having percent runoff greater than 10% compared to only 35% of the years between 1974 and 1993. [Copyright &y& Elsevier]

Analysis of the response to climate change and sea-level rise requires a link from climate change science to the resulting impacts and their policy implications. This paper explores the impacts of sea-level rise, particularly increased coastal flooding due to storm surges. In particular, it asks the simple question “how much will projected global sea-level rise exacerbate coastal flood problems, if ignored?” This is an important question to the intergovernmental process considering climate change. Further many countries presently ignore sea-level rise in long-term coastal planning, even though global sea levels are presently slowly rising.Using the model of Nicholls et al. [Global Environmental Change 9 (1999) S69], the analysis considers the flood impacts of sea-level rise on an “IS92a world” based on a consistent set of scenarios of global-mean sea-level rise, subsidence (where appropriate), coastal population change (usually increase), and flood defence standards (derived from GDP/capita). Two of the protection scenarios consider the possible upgrade of flood defences, but no allowance for global-mean sea-level rise is allowed to ensure consistency with the question being investigated. This model has been validated against national- and regional-scale assessments indicating that the relative results are reasonable, and the absolute results are of the right order of magnitude.The model estimates that 10 million people experienced flooding annually in 1990. It also predicts that the incidence of flooding will change without sea-level rise due to changes to the other three factors. Taking the full range of scenarios considered by 2100 the number of people flooded could be from 0.4 to 39 million/year. All the sea-level rise scenarios would cause an increase in flooding during the 21st century if measures to adapt to sea-level rise are not taken. However, there are significant uncertainties and the number of people who are estimated to experience flooding in 2100 is 16–388 million for the mid (55-cm) global-mean sea-level rise scenarios, and up to 510 million people/year for the high (96-cm) scenario. These results suggest that sea-level rise could be a significant problem if it is ignored, and hence it needs to be considered within the policy process considering climate change in terms of mitigation (reducing greenhouse gas emissions) and adaptation (improved coastal management and planning) needs. [Copyright &y& Elsevier]

This paper describes a topoclimatic analysis that was carried out during the first year of the DIsGELO project. A climatological study and an orographical analysis were carried out, in order to identify frost-prone areas in Emilia-Romagna region (Italy). The former was used to identify and characterise the frost events in the period March–April 1987–2000 for 161 meteorological stations. A synthetic frost risk index, taking into account both temperatures and phenological conditions (expressed by decade number) was devised. For every station we computed both the synthetic frost risk index and the mean minimum temperature. The analysis of the digital elevation model provided some orographical variables: slope, aspect, absolute and relative altitude above valley bottom, valley width, closeness to the sea, and new variables specifically devised to evaluate surface roughness in the plain areas. Maps were then created for every variable and values were obtained for every station by means of a geographic information system. The study area was divided into two domains, the hill zone and the plain, and for each the correlation between the climatological and orographical variables was computed and geostatistical techniques were applied to create some temperature and frost risk climatological maps. For the hills of Emilia-Romagna, a significant correlation was found between the mean minimum temperature during frost events and two orographical factors: the relative altitude above the valley bottom and the closeness to the sea. For the plain no significant correlation was found up to now, probably due to the insufficient detail in the data, so some arbitrary coefficients, based on former practical experience, were added in order to take into account two other orographical factors describing the presence of hollows and knolls. An exponential relationship between the mean minimum temperature and the synthetic frost index was then used to obtain a preliminary frost risk map. [Copyright &y& Elsevier]

Land has an important role in the climate system. Its spatial and temporal variability exceeds the ocean’s. Roughness properties and participation of land in the moisture exchange process underline its importance. Because of increasing land degradation and land use change in the last century a better understanding of these processes is required. For this purpose several new modelling approaches have been developed recently. Population of high and middle latitudes has to face additional problems: frozen soil, snowpack and ice cover of the surface change its characteristic features. The latest IPCC assessment report (2001) also emphasises the importance of the above mentioned processes.In the frame of a research project on renewable energy sources which is specially focused on potential usage of wind energy, a linear spectral wind model has been applied and tested for different types of terrain conditions. In this paper effects of agricultural land use variations on wind fields are discussed. Comparative case studies were carried out to analyse the applicability of the WAsP model on different terrain conditions. [Copyright &y& Elsevier]

To represent objective characteristics of circulation patterns, the spectral structure of both stratospheric and tropospheric fields is analysed in terms of spherical harmonic coefficients. The aim of this study is to compare the long-term behaviour of circulation patterns and their connections to some “extra-terrestrial” influence and circulation indices as well. A huge database of reanalyses from NCEP is used with appropriate spectral coefficients available for period 1948-now four times per day in 28 levels for relative vorticity, divergence, temperature, etc. Temporal analysis of significant spherical harmonics is introduced as well as the comparison of their changes with respect to the changes of solar activity and the phase of QBO. Generally, these wavenumbers mark no or a little positive trends, but for some distinctive wavenumbers representing individual patterns of polar vortex shape negative trend can be seen as well at the first part of time series. Changes with respect to solar activity cycle and QBO phase are presented for whole spectral domain not too well expressed, quite significant results are analysed for a few distinct wavenumbers, mainly in case of separation of time series for 1948–1972 and 1973–1997 periods. Moreover, long-term natural variability connected to the extra-terrestrial influence is studied as well as interannual variability with the emphasis to the QBO. Cross-correlation analysis shows significant difference for selected wavenumbers against solar flux F10.7 in separated periods with some correlation for the first one and rather no significant correlation for the second period. Long-term changes in the variability of the circulation patterns are analysed by means of wavelet analysis access to the series of selected wavenumbers displaying development of some periodicities in time. The connection with the tropospheric circulation is also discussed in terms of coefficients of spherical harmonics mostly for all cases in this study. The paper does not provide definite evidence for connections of atmospheric circulation with decadal solar variability, finally, this could be hardly achieved by statistical analysis only, but the aim of this study is to show possible connections between some helio-geophysical or extra-terrestrial parameters and circulation parameters and their long-term changes with emphasis to some distinctive circulation patterns or shapes of polar vortex. [Copyright &y& Elsevier]

Causes leading to global mean sea surface temperature (GT) variability and to variations of the global circulation including the North Atlantic Oscillation (NAO) and El Nin˜o (EN) events are examined. Statistically significant correlation coefficients between these variables were found and their relations are discussed with the aim to show possible causes leading to general year-to-year variability and to the global warming. At the same time, the results contribute to the verification of the hypothesis as given in our previous papers. We have suggested a link of processes generated by geomagnetic forcing that is followed by dramatic shifts in the atmospheric circulation patterns. At times of low geomagnetic activity in winter the meridional flow prevails contributing to the strong heat exchange of air between low and high latitudes. The arctic air penetrates from polar areas and participates in the cooling of middle latitudes; the NAO winter index (WI) is negative. At times of high geomagnetic activity the Icelandic low intensifies and influences the strengthening of the zonal flow in the Northern Hemisphere; the NAO WI is positive. A continuous zone of high pressure originates along middle latitudes and a little north–south motion of air takes place. In mid-latitudes above-normal temperatures occur while in polar areas the values are below normal. The strong Australian high at times of low geomagnetic activity seems to initiate EN events while the zonal flow in the Southern Hemisphere intensifies monsoon rains in the Indian Ocean when geomagnetic activity is high. EN and NAO events are shown to take part in the variability of GT. Controversial problems are discussed as well. [Copyright &y& Elsevier]