pinecone/core-2020-05-10-deduplication huggingface dataset:
Universal spectrum for interannual variability in COADS global air and sea-surface temperatures

Continuous periodogram spectral analyses of 28 years (1961-1988) of seasonal (September-November) mean COADS global surface (air and sea) temperature time-series show that the power spectra follow the universal inverse power law form of the statistical normal distribution. An inverse power law form for power spectra of temporal fluctuations implies long-range temperal correlation and is a signature of self-organized criticality. Universal quantification for self-organized criticality presented in this paper is consistent with a recently developed cell dynamical system model for atmospheric flows, which predicts such non-local connections as intrinsic to quantum-like mechanis governing flow dynamics. -from Author
Moisture transport into the Ethiopian highlands

The Ethiopian summer rains occur as air masses of various origins converge above the Ethiopian plateau. In this study, the relative importance of different moisture transport branches has been estimated using the Lagrangian trajectory model FLEXPART and ERA-Interim reanalysis data, to backtrack air reaching the northern Ethiopian highlands in July–August 1998–2008. The Indian Ocean, the Congo Basin and the Red Sea were found to be important moisture source regions, for air from the Indian Ocean aided by a considerable moisture uptake along routes across the African continent. The following main transport branches were identified: 1) flow from the Gulf of Guinea, 2) flow from the Indian Ocean, and 3) flow from the north; from the Mediterranean region across the Red Sea and the Arabian Peninsula. The largest contribution to the moisture transport into, and release of moisture within, the northern Ethiopian highlands, was associated with air traveling from the Indian Ocean and from the north. This was partly due to the relatively high mean specific humidity of this air, and partly because a large proportion of the air that reaches the highlands, follows these routes. As a total, the amount of moisture brought into the highlands from the north is 46 % higher than from the south, whereas the contribution to moisture release within the highlands is about equal for air coming from the south and from the north. While previous studies have emphasized the importance of the Gulf of Guinea, we find that despite the high specific humidity of the low-level flow of air from the Gulf of Guinea, the amount of moisture carried into and released within the northern Ethiopian highlands through this branch, is much smaller than from the other branches – about 1/8 of that from the Indian Ocean. This is due to fact that normally, only a small proportion of the air reaching Ethiopia comes from the Gulf of Guinea
An assessment of the role of homogenization protocol in the performance of daily temperature series and trends: Application to northeastern Spain

[EN] This paper gives the complete details of the protocols applied for developing a spatially and temporarily high-resolution dataset of temperature for northeastern Spain. Our methodologies used data from a large number of observatories (1583) spanning some portions of the period between 1900 and 2006. The raw dataset was first tested for internal and external consistency to check data quality. To improve data completeness, a linear regression model was then utilized to infill gaps in the daily temperature series using the best correlated data from nearby sites. Discontinuities in the reconstructed series were determined by combining the results of three homogeneity-relative tests: the Standard Normal Homogeneity Test (SNHT), the Eastrerling and Peterson two-phased regression method and the Vincent test. To assess the possible impact of data homogenisation on trends and statistical properties of the final series, a set of tests (e.g. semivariance models and L-moment statistics) was applied to the series before and after correction. Semivariance models suggest a significant improvement in the spatial dependence of the corrected dataset on both seasonal and annual timescales. Also, L-moments gave no evidence of significant changes in the probability distribution of daily temperature series after correction. Taken together, the newly compiled dataset seems to be more robust and reveals more coherent spatial and temporal patterns of temperature compared with the original dataset. From the temporal and spatial perspectives, the new dataset comprises the most complete register of temperature in northeast Spain (1900-2006), with a reasonably spatial coverage. Accordingly, this database can provide a more reliable base for studying temperature changes and variability in the region. This dataset can also be of particular relevance to a number of meteorological, ecological, hydrological and agricultural applications on local, regional and continental scales. Â© 2011 Royal Meteorological Society.We are indebted to the anonymous reviewers for their constructive comments which were most helpful in improving this paper. We would like to thank the Agencia Estatal de Meteorologia for providing the temperature data used in this study. This work has been supported by the research projects CGL2006-11619/HID, CGL2008- 01189/BTE, CGL2011-27574-CO2-02, CGL2011-27753- CO2-01 and CGL2011-27536 ﬁnanced by the Spanish Commission of Science and Technology; and also FEDER, EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250) ﬁnanced by the VII Framework Programme of the European Commission, La nieve en el Pirineo Aragones y su respuesta a ´ la variabilidad climatica, and Efecto de los escenarios ´ de cambio climatico sobre la hidrolog ´ ´ıa superﬁcial y la gestion de embalses del Pirineo Aragon ´ es, ﬁnanced by ´ Obra Social La Caixa and the Aragon Government and ´ Inﬂuencia del cambio climatico en el turismo de nieve, ´ CTTP01/10, ﬁnanced by the Comision de Trabajo de los ´ Pirineos.Peer Reviewe
Modelling variable glacier lapse rates using ERA-Interim reanalysis climatology: an evaluation at Vestari- Hagafellsjökull, Langjökull, Iceland

This article was published in the serial International Journal of Climatology [Wiley  © Royal Meteorological Society]. The definitive version is available at: http://dx.doi.org/10.1002/joc.3440The near-surface air temperature lapse rate is an important tool for spatially distributing temperatures in snow- and ice-melt models, but is difficult to parameterize, as it is not simply correlated with boundary-layer meteorological variables, such as temperature itself. This contribution quantifies spring-autumn lapse rate variability over 5 years at Vestari-Hagafellsjökull, a southerly outlet of Langjökull in Iceland. It is observed that summer lapse rates (0.57 °C 100 m) are significantly lower than non-summer rates, and are also lower than the Saturated Adiabatic Lapse Rate (SALR), which is often adopted in melt models. This is consistent with reduced near-surface temperature sensitivity to free-atmosphere temperature change during the occurrence of melting. A Variable Lapse Rate (VLR) regression model is calibrated with standardized, 750 hPa temperature anomalies derived from ERA-Interim climatology, which is shown to be highly significantly correlated with near-surface temperatures. The modelled VLR overestimates cumulative June-September Positive Degree Days (PDDs) by 3% when used to extrapolate temperatures from 1100 to 500 m a.s.l. on the glacier, whereas the SALR overestimates cumulative PDDs by 14%. ERA-Interim data therefore appear to offer a good representation of free-atmosphere temperature variability over Vestari-Hagafellsjökull, and the modelling approach offers a simple means of improving lapse rate parameterizations in melt models. © 2012 Royal Meteorological Society
Climatology and recent increase of westerly winds over the Amundsen Sea derived from six reanalyses

The observed acceleration of glaciers from West Antarctica into the Amundsen Sea is estimated to be contributing 6% to current sea-level rise with the estimated potential to add 0.24 m to global sea level. Stronger westerly winds over the Amundsen Sea can increase the flow of relatively warm ocean water to the base of ice shelves that flow from glaciers into the Amundsen Sea. Thinning of the glaciers caused by this warming is a potentially important factor in driving the observed acceleration of glaciers. However, the climatology of winds in the region has not been extensively studied due to a lack of in situ observational long-term records. Here six different reanalysis datasets are assessed (CFSR, ERA-40, ERA-Interim, JRA-25, MERRA and NNR1) to determine a best estimate of variability and change since 1979 when the widespread monitoring of the atmosphere from satellites was introduced. A comparison with independent mean sea-level pressure data from ice drifting buoys shows that ERA-Interim is clearly the most accurate at capturing the details of individual weather systems over the neighbouring Bellingshausen Sea, implying that it is also accurate over the Amundsen Sea. In terms of climatological means, the five recently-produced (after ∼2000) reanalysis datasets show only small differences. Decadal variations of westerly winds congruent with the observed increases in the southern annular mode (SAM) index are a consistent feature across the reanalysis datasets. In particular, the strong seasonal dependence of observed trends in the SAM (i.e. significant positive trends in the summer and autumn in recent decades) is also seen in the strength of westerly winds over the Amundsen Sea. In terms of year-to-year variability, the annual mean westerly winds over the Amundsen Sea were found to be significantly correlated with the SAM in summer (r = 0.35; p≤0.05) and El Nino-Southern Oscillation in spring (September to November) (r = 0.41; p≤0.05)
Significant reduction of cold temperature extremes at Faraday/Vernadsky station in the Antarctic Peninsula

This study examines the daily observed temperature at the Faraday/Vernadsky station in the Antarctic Peninsula for the period February 1947 through January 2011. Faraday/Vernadsky is experiencing a significant warming trend of about 0.6 °C/decade over the last few decades. Concurrently, the magnitude of extremely cold temperatures has reduced while there is no evidence for an increase of the annual maximum temperature. An empirical mode decomposition reveals that most of the temperature variability occurs on intraannual time scales and that changes in the magnitude of the annual cycle can be explained by a simple periodic stochastic process. Extremely cold temperatures below a threshold follow a generalised Pareto distribution (GPD) with a negative shape parameter and thus are bounded. We find that the extremely cold behaviour in the first half of the record is significantly different from the second half. At the same time there is no evident increase of warm temperatures or in the location of the maximum of the temperature probability distribution. These findings provide evidence that at Faraday/Vernadsky, it is the change in the shape of the temperature distribution that has substantially contributed to the observed warming over the last few decades. Furthermore, we find evidence for clustering of extreme cold events and show that they are predictable a few days in advance using a precursor-based prediction scheme
Bias correction of daily precipitation simulated by a regional climate model: a comparison of methods

Quantifying the effects of future changes in the frequency of precipitation extremes is a key challenge in assessing the vulnerability of hydrological systems to climate change but is difficult as climate models do not always accurately simulate daily precipitation. This article compares the performance of four published techniques used to reduce\ud
the bias in a regional climate model precipitation output: (1) linear, (2) nonlinear, (3) γ -based quantile mapping and\ud
(4) empirical quantile mapping. Overall performance and sensitivity to the choice of calibration period were tested\ud
by calculating the errors in the first four statistical moments of generated daily precipitation time series and using a cross-validation technique. The study compared the 1961–2005 precipitation time series from the regional climate model HadRM3.0-PPE-UK (unperturbed version) with gridded daily precipitation time series derived from rain gauges for seven catchments spread throughout Great Britain. We found that while the first and second moments of the precipitation frequency distribution can be corrected robustly, correction of the third and fourth moments of the distribution is much more sensitive to the choice of bias correction procedure and to the selection of a particular calibration period. Overall, our results demonstrate that, if both precipitation data sets can be approximated by a γ -distribution, the γ -based quantilemapping technique offers the best combination of accuracy and robustness. In circumstances where precipitation data sets cannot adequately be approximated using a γ -distribution, the nonlinear method is more effective at reducing the bias, but the linear method is least sensitive to the choice of calibration period. The empirical quantile mapping method can be highly accurate, but results were very sensitive to the choice of calibration time period. However, it should be borne\ud
in mind that bias correction introduces additional uncertainties, which are greater for higher order moments
Optimization of the geopotential heights information used in a rainfall-based weather patterns classification over Austria

International audienceClassifications of atmospheric circulation patterns are useful tools to improve the description of the climate of a given region and the analysis of meteorological situations. In particular, weather patterns (WP) classifications could be used to improve the description of spatial heavy rainfall. Here, a bottom up approach, previously used to build WP classification in France, is applied for the definition of a WP classification useful for the description of Austrian heavy rainfall. The optimal spatial extent and the optimal position of the geopotential fields to be taken into account for a WP classification is studied. The proposed WP classification is shown to be coherent with the general knowledge on synoptic situations responsible for heavy rainfall over Austria. Moreover, the classification has good performances in term of heavy rainfall spatial description compared to 152 COST 733 classifications defined in the same region. In particular, we show that the choice of spatial extent of the geopotential fields, their position and their characteristics is relevant for capturing physical information on synoptic situations responsible for heavy rainfall and that it can improve weather pattern classification performances
Assessing the capability of multi-scale drought datasets to quantify drought severity and to identify drought impacts: An example in the Ebro Basin

Assessing the risk, the severity and the likely evolution of droughts are key tasks for improving preparedness of regions prone to drought conditions, and mitigation of drought consequences. The access to real-time and high-quality climatic information is essential for this purpose. Different climatic databases are being developed and made available on real time by climatic research institutions, but their capability for quantifying droughts characteristics including severity, or spatio-temporal variability, is uncertain given their low spatial resolution. In this study, we assessed the capability of three databases with contrasted spatial resolution for measuring spatial and temporal variability of drought occurrence. The standardized precipitation index, calculated for each database, showed that the low resolution datasets allow an acceptable measurement of the magnitude, intensity and duration of droughts, while failing mostly in detecting the spatial patterns of the specific drought episodes. Moreover, the capability of the datasets for assessing the impacts of droughts on surface hydrology and tree growth was examined. Results confirmed the usefulness of the drought index for assessing drought impacts on water resources and forest ecosystems even when low resolution databases are used. © 2012 Royal Meteorological Society.This work has been supported by the research projects CGL2008-01189/BTE, CGL2011-27574-CO2-02 and CGL2011-27536 financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1-212250) financed by the VII Framework Programme of the European Commission, ‘Efecto de los escenarios de cambio climático sobre la hidrología superficial y la gestión de embalses del Pirineo Aragonés’ financed by ‘Obra Social La Caixa’ and the Aragón Government and Influencia del cambio climático en el turismo de nieve, CTTP01/10, Financed by the Comisión de Trabajo de los Pirineos.Peer Reviewe
The Amundsen Sea low

We develop a climatology of the Amundsen Sea low (ASL) covering the period 1979–2008 using ECMWF operational and reanalysis fields. The depth of the ASL is strongly influenced by the phase of the Southern annular mode (SAM) with positive (negative) mean sea level pressure anomalies when the SAM is negative (positive). The zonal location of the ASL is linked to the phase of the mid-tropospheric planetary waves and the low moves west from close to 110°W in January to near 150°W in June as planetary waves 1 to 3 amplify and their phases shift westwards. The ASL is deeper by a small, but significant amount, during the La Niña phase of El Niño-Southern Oscillation (ENSO) compared to El Niño. The difference in depth of the low between the two states of ENSO is greatest in winter. There is no statistically significant difference in the zonal location of the ASL between the different phases of ENSO. Over 1979–2008 the low has deepened in January by 1.7 hPa dec−1 as the SAM has become more positive. It has also deepened in spring and autumn as the semi-annual oscillation has increase in amplitude over the last 30 years. An increase in central pressure and eastward shift in March has occurred as a result of a cooling of tropical Pacific SSTs that altered the strength of the polar front jet
The effect of moisture transport variability on Ethiopian summer precipitation

The main rainy season in Ethiopia occurs during the northern hemisphere summer, when air masses carrying moisture from the Indian Ocean, the Gulf of Guinea, the African continent, the Red Sea, and the Mediterranean Sea, converge above the Ethiopian mountain plateau. In this study, the variability in different branches of this transport has been studied using the Lagrangian trajectory model FLEXPART and ERA-Interim reanalysis data for July–August 1998–2008. The largest relative fluctuations occur in the normally limited transport from the Gulf of Guinea, whereas smaller relative changes in the larger branches from the Indian Ocean and the regions to the north, often have greater effects. Wet/dry summer months in the northern Ethiopian highlands were associated with increased/reduced transport of moisture from the south, with consequent changes in the release of moisture in the region. In dry months, the moisture transport from the south was reduced to 85 % of its mean, and in wet months increased to 107 %. The increased transport in wet months could be attributed to low-level westerly anomalies above Central Africa – increasing moisture transport from the Gulf of Guinea and in most cases also from the Indian Ocean – and with enhanced southerlies along the coast of East Africa, increasing the transport from the Indian Ocean. The amount of moisture transported into the highlands from the north could not be consistently associated with wet and dry months, but in most cases the release of moisture in air coming from the north contributed to the resulting precipitation anomaly. The release of moisture in the northern branch was reduced to 94 % of its mean in dry months, and increased to 111 % in wet months. This may be an effect of altered convergence associated with changes in the transport from the south
Background Ozone Level in the Sydney basin: assessment and trend analysis

It has been recognized that the background ozone concentration in urban areas is changing over the years. This article aims to determine the background ozone level (BOL) using ambient air quality data measurements collected at some monitoring stations in the Sydney basin, Australia. A definition of background ozone in the context of the Sydney region is proposed. With this definition, it is possible to estimate the background ozone using ambient measurements of ozone and its precursors. The trend of the BOL is also estimated from the temporal ambient monitoring records as of early 1998-2005. These ozone level changes at different monitoring stations are assessed using the linear regression method. The results are shown to vary between different monitoring sites. This demonstrates that the local conditions at each site are important in determining as to whether an air quality management plan for reducing the ozone level to below the exceedance level is effective and achievable or not. Furthermore, the results obtained are compared with those obtained by the ClappJenkin method, which is based on the relationship between oxidant and nitrogen oxides, assuming a stationary state of photochemical smog function
A climatology of strong wind events at McMurdo station, Antarctica

The first climatology of strong wind events (SWEs) at McMurdo station, Antarctica based on the in situ observations and reanalysis fields is presented. SWEs occur throughout the year, but with a minimum during the summer. They are associated with negative mean sea level pressure (MSLP) and upper height anomalies across the Ross Sea/Ice Shelf, as well as positive temperature anomalies at the station. Wind directions during SWEs exhibit a bimodal distribution of 135–180° and 45–90°. This distribution occurs because of the interaction of the predominantly southerly flow with the orography of Black and White Island and Minna Bluff. The east-northeast flow is associated with winds that are deflected around the orography, while the more southerly events have sufficient energy to override the barriers. The bimodal wind distribution is most common during the winter season since the southerly flow is stronger as a result of deeper cyclonic systems. SWEs also occur when there are large, positive MSLP anomalies at McMurdo station as ridges of high pressure build from the interior and enhance the pressure gradient between the continental high and offshore lows. The interannual variability in the number of winter SWEs is large. Years with many SWEs are associated with a deep climatological low centred over the north eastern Ross Ice Shelf. Years with few winter SWEs have a weakened mid-tropospheric vortex over the Ross Ice Shelf. There are periods when the index of the El Niño-Southern Oscillation (ENSO) correlates with the number of SWEs. However, the links are not statistically significant in the longer term. A similar link was also observed between the Southern Annular Mode (SAM) and the interannual variability in the number of SWEs. The relationship was found to be stronger when the phase of ENSO and the SAM were the same