We present a European land‐only daily high‐resolution gridded data set for precipitation and minimum, maximum, and mean surface temperature for the period 1950–2006. This data set improves on ...previous products in its spatial resolution and extent, time period, number of contributing stations, and attention to finding the most appropriate method for spatial interpolation of daily climate observations. The gridded data are delivered on four spatial resolutions to match the grids used in previous products as well as many of the rotated pole Regional Climate Models (RCMs) currently in use. Each data set has been designed to provide the best estimate of grid box averages rather than point values to enable direct comparison with RCMs. We employ a three‐step process of interpolation, by first interpolating the monthly precipitation totals and monthly mean temperature using three‐dimensional thin‐plate splines, then interpolating the daily anomalies using indicator and universal kriging for precipitation and kriging with an external drift for temperature, then combining the monthly and daily estimates. Interpolation uncertainty is quantified by the provision of daily standard errors for every grid square. The daily uncertainty averaged across the entire region is shown to be largely dependent on the season and number of contributing observations. We examine the effect that interpolation has on the magnitude of the extremes in the observations by calculating areal reduction factors for daily maximum temperature and precipitation events with return periods up to 10 years.
In this study, we present the collation and analysis of the gridded land‐based dataset of indices of temperature and precipitation extremes: HadEX2. Indices were calculated based on station data ...using a consistent approach recommended by the World Meteorological Organization (WMO) Expert Team on Climate Change Detection and Indices, resulting in the production of 17 temperature and 12 precipitation indices derived from daily maximum and minimum temperature and precipitation observations. High‐quality in situ observations from over 7000 temperature and 11,000 precipitation meteorological stations across the globe were obtained to calculate the indices over the period of record available for each station. Monthly and annual indices were then interpolated onto a 3.75° × 2.5° longitude‐latitude grid over the period 1901–2010. Linear trends in the gridded fields were computed and tested for statistical significance. Overall there was very good agreement with the previous HadEX dataset during the overlapping data period. Results showed widespread significant changes in temperature extremes consistent with warming, especially for those indices derived from daily minimum temperature over the whole 110 years of record but with stronger trends in more recent decades. Seasonal results showed significant warming in all seasons but more so in the colder months. Precipitation indices also showed widespread and significant trends, but the changes were much more spatially heterogeneous compared with temperature changes. However, results indicated more areas with significant increasing trends in extreme precipitation amounts, intensity, and frequency than areas with decreasing trends.
Key Points
We present the most comprehensive land‐based gridded dataset of climate extremes
Temperature extremes show consistent warming trends over the past century
Precipitation extremes are increasing in more areas than they are decreasing
In this study we introduce a daily high‐resolution land‐only observational gridded data set for sea level pressure covering the European region as a new addition to the E‐OBS gridded data sets of ...daily temperatures and precipitation amounts. This data set improves upon existing products in terms of spatial resolution and extent. The data set is delivered on the same four spatial resolutions as the other E‐OBS data sets: 0.25° by 0.25° and 0.5° by 0.5° on a regular latitude‐longitude grid and 0.22° by 0.22° and 0.44° by 0.44° on a rotated pole grid. We show that there is a good agreement in the long‐term mean and standard deviation with popular reanalysis grids. In areas with a relatively high number of stations, the gridded data is closer to the station data than the reanalysis products. There is also a very good agreement with daily weather charts for selected storm events.
Key Points
New observational daily sea level pressure grid (E‐OBS extension)
Comparison of in situ grid with reanalysis grids
Comparison with individual storm events
Changes in diurnal temperature range (DTR) over global land areas are compared from a broad range of independent data sets. All data sets agree that global‐mean DTR has decreased significantly since ...1950, with most of that decrease occurring over 1960–1980. The since‐1979 trends are not significant, with inter‐data set disagreement even over the sign of global changes. Inter‐data set spread becomes greater regionally and in particular at the grid box level. Despite this, there is general agreement that DTR decreased in North America, Europe, and Australia since 1951, with this decrease being partially reversed over Australia and Europe since the early 1980s. There is substantive disagreement between data sets prior to the middle of the twentieth century, particularly over Europe, which precludes making any meaningful conclusions about DTR changes prior to 1950, either globally or regionally. Several variants that undertake a broad range of approaches to postprocessing steps of gridding and interpolation were analyzed for two of the data sets. These choices have a substantial influence in data sparse regions or periods. The potential of further insights is therefore inextricably linked with the efficacy of data rescue and digitization for maximum and minimum temperature series prior to 1950 everywhere and in data sparse regions throughout the period of record. Over North America, station selection and homogeneity assessment is the primary determinant. Over Europe, where the basic station data are similar, the postprocessing choices are dominant. We assess that globally averaged DTR has decreased since the middle twentieth century but that this decrease has not been linear.
Key Points
It is virtually certain globally diurnal temperature range declined since 1950
Large differences/method sensitivities preclude assessment of DTR before 1950
In some regions DTR has very likely increased in the last two to three decades
ABSTRACT
Significant trends in precipitation extremes over Europe since the middle of the 20th century have been found in earlier studies. Most of these studies are based on descriptive indices of ...moderate extremes that occur on average a few times per year. Here we have analyzed rarer precipitation events which occur on average once in 5, 10 and 20 years in the 1950s and 1960s using extreme value theory. We have focused on the 1‐d and 5‐d precipitation amounts in Northern and Southern Europe in all four seasons. Changes over the time period 1951–2010 are studied by considering five consecutive 20‐year time intervals with 10‐year overlap. Despite considerable decadal variability, our results indicate that 5‐, 10‐ and 20‐year events of 1‐d and 5‐d precipitation for the first 20‐year period generally became more common during this 60‐year period. For all regions, seasons and return periods, the median reduction in return period between the first and last 20‐year periods is ∼21% with variations between a decrease of ∼2% and ∼58%.
ABSTRACT
Observational analyses of changing climate extremes over the West Africa region have been limited by the availability of long and high‐quality datasets. To help address this gap, a climate ...extremes indices workshop was held in the Gambia in December 2011 with participants from 14 West African countries. The resulting analysis utilized 15 annual indices derived from observed daily temperatures and 10 annual indices derived from observed daily precipitation. The analysis was conducted for 166 meteorological stations in 13 countries for 2 periods: 1960–2010 and 1981–2010. The analyses of trends in the annual mean temperature indices have identified statistically significant increases of 0.16 °C/decade and 0.28 °C/decade for mean annual maximum and mean annual minimum temperatures, respectively, averaged over all available land stations in the region during the last 50 years. The seasonal‐temperature‐related indices show significant patterns of warming in all seasons. The annual mean of daily minimum temperature has increased more than the annual mean of daily maximum temperature leading to a decreasing trend in the diurnal temperature range. Warm days and warm nights have become more frequent, and cold days and cold nights have become less frequent. The analyses of precipitation‐based indices indicate spatially non‐coherent changes throughout the study area with few statistically significant trends over the longer period. Exceptions to this are the simple daily intensity index and maximum 5‐day precipitation, which show significant increasing regional trends over both the shorter and longer periods. Additionally, over the recent period (1981–2010) most of the precipitation related indices show significant trends towards wetter conditions. However, this period of increased rainfall follows a decade of significantly drier conditions in the region – it is not clear whether the recent upward trends reflect the ‘recovery’ from this long drought period or represents a long‐term response to warming.
Climate extremes indices were derived from daily temperature and precipitation data from 166 observing stations in 13 West African countries, and combined to provide a regional assessment of changing extremes for 1960–2010 and 1981–2010. Statistically significant warming trends indicate more frequent warm days and nights and less frequent cold days and nights. Precipitation‐based indices indicate weak spatial patterns with few significant trends over 1960–2010, but over 1981–2010 show significant trends towards wetter conditions.
Accumulated snow amounts are a key climate change indicator. It combines the competing effects of climate change‐driven changes in precipitation and stronger snowmelt related to increasing ...temperatures. Here we provide observational evidence from a pan‐European in situ data set that mean snow depth generally decreases stronger than extreme snow depth. Widespread decreases in maximum and mean snow depth were found over Europe, except in the coldest climates, with an average decrease of −12.2%/decade for mean snow depth and −11.4%/decade for maximum snow depth since 1951. These trends accelerated after the 1980s. This has strong implications for the availability of freshwater in spring, while extremes in snow depth, usually very disruptive to society, are decreasing at a slower pace.
Plain Language Summary
Changes in snow accumulation are a climate change indicator. Global warming brings more extreme precipitation, and higher temperatures lead to less snow accumulation. Studies of the future climate indicate that under strong warming of the planet, extremes of snowfall will decrease less than the average snowfall. In this study, we show that snow accumulation is already dramatically decreasing over Europe, which has strong implications for the availability of freshwater during the melt period in spring. However, extreme snow accumulation, which is usually very disruptive to society, is decreasing at a slower pace.
Key Points
A widespread decrease of mean and extreme snow depth is observed over Europe
Extreme snow depth is decreasing less fast than mean snow depth
There is an acceleration of the decrease after the 1980s
Global radiation is a fundamental source of energy in the climate system. A significant impact of global radiation on temperature change is expected due to the widespread dimming/brightening ...phenomenon observed since the second half of the twentieth century. This work describes the analysis of 312 stations with sunshine duration (SD) series, a proxy for global radiation, and temperature series in the European Climate Assessment & Dataset (ECA&D) with data over the period 1961–2010. The relationship between SD and temperature series is analyzed for four temperature variables: maximum (Tmax), minimum (Tmin), mean temperature (Tmean), and diurnal temperature range (DTR). The analyses are performed on annual and seasonal basis. The results show strong positive correlations between SD and temperatures over Europe, with highest correlation for DTR and Tmax during the summer period. These results confirm the strong relationship between SD and temperature trends over Europe since the second half of the twentieth century. This study supports previous suggestions that dimming (brightening) has partially decreased (increased) temperatures thereby modulating the greenhouse gas induced warming rates over Europe.
Key Points
Strong relationship between sunshine duration and temperatures in Europe
DTR and Tmax show the strongest signal, especially in summer
Dimming/brightening has modulated temperature decadal changes since the 1960s
Trends in indices of climate extremes are studied on the basis of daily series of temperature and precipitation observations from more than 100 meteorological stations in Europe. The period is ...1946–99, a warming episode. Averaged over all stations, the indices of temperature extremes indicate “symmetric” warming of the cold and warm tails of the distributions of daily minimum and maximum temperature in this period. However, “asymmetry” is found for the trends if the period is split into two subperiods. For the 1946–75 subperiod, an episode of slight cooling, the annual number of warm extremes decreases, but the annual number of cold extremes does not increase. This implies a reduction in temperature variability. For the 1976–99 subperiod, an episode of pronounced warming, the annual number of warm extremes increases 2 times faster than expected from the corresponding decrease in the number of cold extremes. This implies an increase in temperature variability, which is mainly due to stagnation in the warming of the cold extremes.
For precipitation, all Europe-average indices of wet extremes increase in the 1946–99 period, although the spatial coherence of the trends is low. At stations where the annual amount increases, the index that represents the fraction of the annual amount due to very wet days gives a signal of disproportionate large changes in the extremes. At stations with a decreasing annual amount, there is no such amplified response of the extremes.
The indices of temperature and precipitation extremes in this study were selected from the list of climate change indices recommended by the World Meteorological Organization–Commission for Climatology (WMO–CCL) and the Research Programme on Climate Variability and Predictability (CLIVAR). The selected indices are expressions of events with return periods of 5–60 days. This means that the annual number of events is sufficiently large to allow for meaningful trend analysis in ∼50 yr time series. Although the selected indices refer to events that may be called “soft” climate extremes, these indices have clear impact relevance.
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