pinecone/core-2020-05-10-deduplication huggingface dataset:
A gridded hourly precipitation dataset for Switzerland using\ud
rain-gauge analysis and radar-based disaggregation

Rain gauges and weather radars both constitute important devices for operational precipitation monitoring. Gauges provide accurate yet spotty precipitation estimates, while radars offer high temporal and spatial resolution yet at a limited absolute accuracy. We propose a simple methodology to combine radar and daily rain-gauge data to build up a precipitation dataset with hourly resolution covering a climatological time period. The methodology starts from a daily precipitation analysis, derived from a dense rain-gauge network. A sequence of hourly radar analyses is then used to disaggregate the daily analyses. The disaggregation is applied such as to retain the daily precipitation totals of the rain-gauge analysis, in order to reduce the impact of quantitative radar biases. Hence, only the radar's advantage in terms of temporal resolution is exploited. In this article the disaggregation method is applied to derive a 15-year gridded precipitation dataset at hourly resolution for Switzerland at a spatial resolution of 2 km. Validation of this dataset indicates that errors in hourly intensity and frequency are lower than 25% on average over the Swiss Plateau. In Alpine valleys, however, errors are typically larger due to shielding effects of the radar and the corresponding underestimation of precipitation periods by the disaggregation. For the flatland areas of the Swiss Plateau, the new dataset offers an interesting quantitative description of high-frequency precipitation variations suitable for climatological analyses of heavy events, the evaluation of numerical weather forecasting models and the calibration/operation of hydrological runoff models
Estimation of the probable maximum precipitation in Barcelona (Spain)

The main objective of this study is to estimate the probable maximum precipitation (PMP) in Barcelona for durations ranging from 5 min to 30 h. To this end, rain records from the Jard´ı gauge of the Fabra Observatory located in Barcelona (1927–1992) and the urban pluviometric network supported by Clavegueram de Barcelona, S.A.\ud
(CLABSA, 1994–2007) were analysed. Two different techniques were used and compared: a physical method based on the maximization of actual storms, and the Hershfield’ statistical method. The PMP values obtained using the two techniques are very similar. In both cases, the expected increasing behaviour of the PMP with duration was found, with the increase especially notable for the mesoscale durations 2–9 h, and not significant from 12 h on up. This result seems to be related to the scale of the meteorological situations producing high intense rainfall amounts over our territory.Postprint (published version
Assessing trends in extreme precipitation events intensity and magnitude using non-stationary peaks-over-threshold analysis: a case study in northeast Spain from 1930 to 2006

35 Pags., 1 Tabl., 9 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0088Most applications of the extreme value (EV) theory have assumed stationarity, i.e. the statistical properties of the process do not change over time. However, there is evidence suggesting that the occurrence of extreme events is not stationary but changes naturally, as it has been found for many other climate variables. Of paramount importance for hazard analysis is whether the observed precipitation time series exhibit long-term trends or cycles; such information is also relevant in climate change studies. In this study, the theory of non-stationary extreme value (NSEV) analysis was applied to data series of daily precipitation using the peaks-over-threshold (POT) approach. A Poisson/generalized Pareto (P/GP) model, in which the model parameters were allowed to vary linearly with time, was fitted to the resulting series of precipitation event's intensity and magnitude. A log-likelihood ratio test was applied to determine the existence of trends in the model parameters. The method was applied to a case study in northeast Spain, comprising a set of 64 daily rainfall series from 1930 to 2006. Statistical significance was achieved in less than 5% of the stations using a linear non-stationary model at the annual scale, indicating that there is no evidence of a generalized trend in extreme precipitation in the study area. At the seasonal scale, however, a significant number of stations along the Mediterranean (Catalonia region) showed a significant decrease of extreme rainfall intensity in winter, while experiencing an increase in spring.This research has been supported by the following projects: CGL2008-00831/BTE, CGL2006-11619/HID, CGL2008-01189/BTE and CGL2008-1083/CLI funded by the Spanish Commission of Science and Technology and FEDER; EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1-212250) funded by the VII Framework Programme of the European Commission; ‘Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica’ and ‘La nieve en el Pirineo Aragonés: distribución espacial y su respuesta a las condiciones climáticas’ funded by ‘Obra Social La Caixa’ and the Aragón Government; and ‘Programa de grupos de investigación consolidados’ funded by the Aragón Government.Peer reviewe
Development and analysis of a 50-year high-resolution daily gridded precipitation dataset over Spain (Spain02)

12 páginas, 11 figuras, 1 tabla.In this paper, we present a new publicly available high-resolution daily precipitation gridded dataset developed for peninsular Spain and the Balearic islands using 2756 quality-controlled stations (this dataset is referred to as Spain02). The grid has a regular 0.2° (approx. 20 km) horizontal resolution and spans the period from 1950 to 2003. Different interpolation methods were tested using a cross-validation approach to compare the resulting interpolated values against station data: kriging, angular distance weighting, and thin plane splines. Finally, the grid was produced applying the kriging method in a two-step process. First, the occurrence was interpolated using a binary kriging and, in a second step, the amounts were interpolated by applying ordinary kriging to the occurrence outcomes. This procedure is similar to the interpolation method used to generate the E-OBS gridded data—the state-of-the-art publicly available high-resolution daily dataset for Europe—which was used in this study for comparison purposes. Climatological statistics and extreme value indicators from the resulting grid were compared to those from the 25 km E-OBS dataset using the observed station records as a reference. Spain02 faithfully reproduces climatological features such as annual precipitation occurrence, accumulated amounts and variability, whereas E-OBS has some deficiencies in the southern region. When focusing on upper percentiles and other indicators of extreme precipitation regimes, Spain02 accurately reproduces the amount and spatial distribution of the observed extreme indicators, whereas E-OBS data present serious limitations over Spain due to the sparse data used in this region. As extreme values are more sensitive to interpolation, the dense station coverage of this new data set was crucial to get an accurate reproduction of the extremes.We acknowledge Spanish Ministry of Medio Ambiente y\ud
Medio Rural y Marino (Exp. 200800050084078) and the\ud
E-OBS dataset from the EU-FP6 project ENSEMBLES.Peer reviewe
Multi-model forecast skill for mid-summer rainfall over southern Africa

Southern African December-January-February (DJF) probabilistic rainfall forecast skill is assessed over a 22-year retroactive test period (1980/1981 to 2001/2002) by considering multi-model ensembles consisting of downscaled forecasts from three of the DEMETER models, the ECMWF, Météo-France and UKMO coupled ocean-atmosphere general circulation models. These models are initialized in such a way that DJF forecasts are produced at an approximate 1-month lead time, i.e. forecasts made in early November. Multi-model forecasts are obtained by: i) downscaling each model's 850 hPa geopotential height field forecast using canonical correlation analysis (CCA) and then simply averaging the rainfall forecasts; and ii) by combining the three models' 850 hPa forecasts, and then downscaling them using CCA. Downscaling is performed onto the 0.5° × 0.5° resolution of the CRU rainfall data set south of 10° south over Africa. Forecast verification is performed using the relative operating characteristic (ROC) and the reliability diagram. The performance of the two multi-model combinations approaches are compared with the single-model downscaled forecasts and also with each other. It is shown that the multi-model forecasts outperform the single model forecasts, that the two multi-model schemes produce about equally skilful forecasts, and that the forecasts perform better during El Niño and La Niña seasons than during neutral years.This work was partly sponsored by the Water Research Commission of South Africa (project K5/1492).http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0088hb201
Transient changes in flood frequency and timing in Britain under potential projections of climate change

Climate change could have dramatic consequences for the earth's environment, especially its hydrology, yet the ‘noise’ of natural climate variability can mask the impacts of climate change on shorter time scales, and can act (in an unpredictable way) to enhance or reduce its effect in any given period in the future. Thus, impact studies based on time slices, which look at modelled differences between baseline (e.g. 1961–1990) and future (e.g. 2070–2099) periods, can be misleading. This paper makes use of three new transient climate projections, from a perturbed parameter ensemble of a regional climate model (RCM) covering the period 1950–2099, to investigate transient changes in flood frequency and timing for two example catchments in England. Annual maximum (AM) time series are extracted from modelled flow timeseries (for hourly, daily mean and running 30-day mean flows). The AM series are analysed in terms of flood frequency (using a fitted generalised logistic distribution) and timing in a 30-year moving window. A non-linear trend analysis is performed on the derived time series, with permutation testing to estimate statistical significance. The results show that changes over the period are often non-linear, and vary considerably in size and statistical significance according to catchment, flow time step and RCM ensemble member. The relative effects of the three RCM ensemble members are consistent with their relative climate sensitivities. A nationwide analysis, using daily mean flows from a grid-based runoff and routing model for the UK with one of the RCM ensemble members, was consistent with the catchment results in terms of direction of trends, but generally gave trends of a higher magnitude, indicating the presence of some hydrological model structure uncertainty. The nationwide results suggest increased flood risk across much of the country
Tropical systems from the southwest Indian Ocean making landfall over the Limpopo River Basin, southern Africa : a historical perspective

The study provides perspective on the contribution of landfalling tropical systems (cyclones, depressions, storms and lows) from the southwest Indian Ocean (SWIO) towards rainfall over the eastern interior of southern Africa, over the period 1948-2008. Although these systems contribute to < 10% of the annual rainfall occurring over the region, their relative contribution to local and widespread heavy rainfall events is shown to be highly significant. About 50% of widespread heavy rainfall events over northeastern South Africa are caused by landfalling tropical systems. Fourier analysis performed on the time series of rainfall occurring over notheastern South Africa in association with these systems reveals the existence of a quasi-18-year cycle. The cycle coincides with the well-known quasi-18-year Dyer-Tyson cycle in rainfall over the summer rainfall region of South Africa. These results suggest that atmospheric and surface conditions leading to wet phases of the Dyer-Tyson cycle also favour the landfall and subsequent westward movement of tropical systems from the SWIO over southern Africa – and their eventual contribution to rainfall over northeastern South Africa and southern Zimbabwe.Water Research Commission,
South Africa (WRC Project No. K5/1847).http://www3.interscience.wiley.com/journal/4735/hom
Tropical Pacific-North Pacific teleconnection in a coupled GCM: Remote and local effects

The connection between Tropical Pacific and North Pacific variability is investigated in a state-of-the art coupled ocean-atmosphere model, comparing two 20th century simulations at T30 and T106 atmospheric horizontal resolutions. Despite a better simulation of the frequency and the spatial distribution of the Tropical Pacific anomalies associated with the El Nino Southern Oscillation (ENSO) in the high-resolution experiment, the response in the North Pacific is scarcely different from the low-resolution experiment where the ENSO variability is weaker and at higher than
observed frequency. In the North Pacific, the response of surface atmospheric fields to the variability in the Tropical
Pacific appears to be affected by local coupling processes significantly different in the two experiments. The coupling
between sea level pressure (SLP) and sea surface temperature (SST) in the North Pacific as well as the influence of the
Tropical Pacific SST has been measured here by means of the ‘coupled manifold’ technique. In the low-resolution case
the SLP variances linked to the fraction of North Pacific SST not influenced by the Tropical Pacific are weak suggesting
that the remote influence is strong, consistently with the observations. On the contrary, in the high-resolution experiment
the fractions and the patterns of the SLP variances due to the Tropical Pacific SST and those linked to the North Pacific
SST are comparable. In the latter case, model systematic errors in the northwestern Pacific influences the local coupling
processes thus triggering the remote response. We conclude that an increased atmospheric horizontal resolution does not
reduce the coupled model systematic errors in the representation of the teleconnection between the North and the Tropical
Pacific and that the validation of coupled models has to consider both remote and local processes
Tracking mesoscale convective systems in the Sahel: relation between cloud parameters and precipitation

Although mesoscale convective systems (MCSs) are the main source of precipitation in the semi-arid Sahel region, the relationship between MCS characteristics and their generated precipitation remain unclear. However, a thorough understanding of this relation is essential to work towards a classification scheme for MCSs and eventually to improve quantitative precipitation estimates in which cloud parameters are used as proxy variables for the total or maximum intense rainfall from a system. Accordingly, this study aims to analyse the cloud parameters and rain variables distributions and their concurrence before quantifying the relationships between them. This is done using hourly EUMETSAT's Meteosat-8 infrared (10.8 µm) images, 3-hourly precipitation data from National Aeronautics and Space Administration (NASA)'s Tropical Rainfall Measuring Mission and an MCS tracking algorithm. The period of interest extends from 1 June till 22 September 2006 and the area of interest covers the Lake Chad region. Results indicate that MCSs in the Sahel region generally show a maximum cloud coverage around 57 000 km2, a life duration of 9 h, an embedded convective core during 6 h and precipitation peaks around 12.3 mm h−1. A recurrent sequence of cloud and rain variables is also noticed; maximum in cloud coverage is mostly preceded by a minimum in brightness temperature in the cold convective core and is followed by a peak in precipitation. Longer-lived and larger MCSs as well as MCSs embedding very cold and long-lived convective cores exhibit an increased likelihood to induce more intense precipitation. Focussing on the characteristics of the cold convective core rather than on the characteristics of the entire system appears to be more relevant to predict the precipitation as the former are better correlated with the generated precipitation and can be used as proxy parameter for estimations of maximum intense precipitation using two-dimensional nonlinear regression models. Copyright © 2011 Royal Meteorological Societystatus: publishe
The relationship between Lamb weather types and long-term changes in flood frequency, River Eden, UK

This is a "preprint" of an article published in the International Journal of Climatology at: http://dx.doi.org/10.1002/joc.2415Research has found that both flood magnitude and frequency in the UK may have increased over the last five decades. However, evaluating whether or not this is a systematic trend is difficult because of the lack of longer records. Here we compile and consider an extreme flood record that extends back to 1770. Since 1770, there have been 137 recorded extreme floods. However, over this period, there is not a unidirectional trend of rising extreme flood risk over time. Instead, there are clear flood-rich and flood-poor periods. Three main flood-rich periods were identified: 1873–1904, 1923–1933, and 1994 onwards. To provide a first analysis of what is driving these periods, and given the paucity of more sophisticated datasets that extend back to the 18th century, objective Lamb weather types were used. Of the 27 objective Lamb weather types, only 11 could be associated with the extreme floods during the gauged period, and only 5 of these accounted for >80% of recorded extreme floods The importance of these five weather types over a longer timescale for flood risk in Carlisle was assessed, through calculating the proportion of each hydrological year classified as being associated with these flood-generating weather types. Two periods clearly had more than the average proportions of the year classified as one of the flood causing weather types; 1900–1940 and 1983–2007; and these two periods both contained flood-rich hydrological records. Thus, the analysis suggests that systematic organisation of the North Atlantic climate system may be manifest as periods of elevated and reduced flood risk, an observation that has major implications for analyses that assume that climatic drivers of flood risk can be either statistically stationary or are following a simple trend
Seasonal relationships between Indian summer monsoon rainfall and the Southern Oscillation.

Association between the all-India summer monsoon (June to September) rainfall and an index of the Southern Oscillation (SO) is studied in relation to the vagaries of the monsoon rainfall and the seasonal characteristics of the SO. The SOI values of different months and standard seasons show opposite tendencies during deficient and excess years of all-India monsoon rainfall. The correlation coefficients between the all-India monsoon rainfall series and the SOIs of summer monsoon, autumn and winter minus spring seasons are significant at the 1 per cent level
Some features of the south-west monsoon rainfall of Cochin and Minicoy ( India).

Several characteristics of the SW monsoon rainfall of the low latitude stations of Cochin (coastal) and Minicoy (island) have been studied using the hyetograms of these stations for the 10yr period 1973-1982. Both stations exhibit diurnal variations of rainfall with maximum activity in the post-midnight hours and minimum in the afternoon hours. The amplitude of the diurnal variation increases for rain events of increasing intensities. The integrated duration of the seasonal rainfall is about 250h at Cochin and 110h at Minicoy. Half the total rain from heavy falls is received in a 5th of the total duration; half the total duration accounts for only a 5th of the total rain from light falls
The onset of the southwest monsoon over Kerala: 1901-1980

Utilising daily mean rainfall from dense rain gauge networks, the dates of onset of the southwest monsoon over south and north Kerala have been derived on the basis of objective criteria for the years 1901 to 1980. These dates have been compared with the onset dates as per records of the India Meteorological Department. Statistics of the onset dates are presented. The mean onset date for south Kerala is found to be 30 May and for north Kerala 1 June with a standard deviation of about 9 days in both cases. The sharp increase in rainfall that heralds the onset of the monsoon is highlighted by superposed epoch analysis. The prevailing notion that rainfall from pre-monsoon thunderstorms progressively increases and merges with the monsoon rainfall is shown to be not valid
Statistical distribution of daily rainfall and its association with the coefficient of variation of rainfall series

The study focuses attention on the normalized rainfall curve (NRC) depicting the association between cumulated percentage rain amount (x) and cumulated percentage number of rain days (y) of the rainfall series. It is shown that the NRC is uniquely determined by the coefficient of variation (CV) of the rainfall series. There is no universal NRC that can represent all rainfall regimes. The equation x=y exp-b(100-y)c, where b and c are two empirical constants, gives a good analytical representation of the NRCs over a wide range of CV values of the rainfall series. This analytical equation is able to account for the occurrence of high rainfall intensities towards the upper extremity of the NRC for rainfall series with high values of CV
Preliminary measurements of net radiation and evaporation over bare soil and fallow bushland in the Sahel

Net radiation and evaporation are compared over two contrasting land surfaces, fallow bushland and bare soil, in Niger, West Africa. Data are presented for 6 days, before and after a large rainstorm (39 mm), which illustrate how evaporation from the bush vegetation changed little in comparison with the larger change in evaporation observed over the bare soil. Net radiation over the bush vegetation was 20 per cent greater than that over the dry bare soil, but only 12 per cent greater than that over wet bare soil. These differences are consistent with the expected difference in albedo and surface temperature of the two surface
Some aspects of daily rainfall distribution over India during the south-west monsoon season

This paper presents the results of an analysis of the daily rainfall at 365 Indian stations for the 80-year period, 1901-1980. The rainfall data relate to the south-west monsoon season June to September (122 days), which accounts for the major part of the annual rainfall over most parts of the country. The coefficient of variation (CV) of the daily rainfall series varies between 100 and 230 at individual stations, with nearly half the number of stations having CV values in the range 130-150. The number of days of significant rainfall (days with rainfall greater than the mean intensity per rain-day) constitute about 30 of the total number of rain-days and account for about 75 of the seasonal rainfall at almost all the stations
Indian summer monsoon rainfall and 200-mbar meridional wind index: application for long-range prediction

The relationship between all-India monsoon (June-September) rainfall (R) and the wind index Vm) is negative (correlation coefficient = -0.72) and is significant at the 0.1 level and the regression equation based on this data, for the period 1964-1988, is R=86.98-2.44 Vm. The stability and consistency of the relationship between rainfall and the wind index have been examined over sliding widths of 15 and 21 years, and the relationship is found to be significant at the 1 level for all windows of 21-yr widths. The meridional wind index shows a good potential in the long-range prediction scheme of the Indian monsoon rainfall, along with other parameters