The authors propose a new climatic drought index: the standardized precipitation evapotranspiration index (SPEI). The SPEI is based on precipitation and temperature data, and it has the advantage of combining multiscalar character with the capacity to include the effects of temperature variability on drought assessment. The procedure to calculate the index is detailed and involves a climatic water balance, the accumulation of deficit/surplus at different time scales, and adjustment to a log-logistic probability distribution. Mathematically, the SPEI is similar to the standardized precipitation index (SPI), but it includes the role of temperature. Because the SPEI is based on a water balance, it can be compared to the self-calibrated Palmer drought severity index (sc-PDSI). Time series of the three indices were compared for a set of observatories with different climate characteristics, located in different parts of the world. Under global warming conditions, only the sc-PDSI and SPEI identified an...

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A Multiscalar Drought Index Sensitive to Global Warming: The Standardized Precipitation Evapotranspiration Index

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

The Intergovernmental Panel on Climate Change (IPCC) Technical Paper Climate Change and Water draws together and evaluates the information in IPCC Assessment and Special Reports concerning the impacts of climate change on hydrological processes and regimes, and on freshwater resources – their availability, quality, use and management. It takes into account current and projected regional key vulnerabilities, prospects for adaptation, and the relationships between climate change mitigation and water. Its objectives are:

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Climate change and water.

Climate change 2014 - Synthesis Report

The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

The influence of climate change on heating and cooling energy demand in Ireland is investigated using a small ensemble of regional climate simulation datasets driven by the ERA-40 reanalysis data and by the global climate model ECHAM5-OM1 assuming three different greenhouse gas emission scenarios. Simple relationships between commonly used temperature-based indices and heating/cooling energy demand have been used. It has been shown previously that these relationships are highly correlated even though other parameters such as wind speed, sunniness and cost of energy also influence consumption. Results suggest that the heating energy demand has already slightly decreased in the south of the country for the time period 1981–2000 compared to that in 1961–1980, although the difference might not be a robust signal because of the relatively short averaging time period of 20 years and the model uncertainty, which is in the same order as the simulated changes. However, a clear trend of decreasing heating energy demand is predicted for the rest of this century using longer averaging periods of 40 years. Whereas air conditioning is not an issue in Ireland's current climate, a weak demand might develop towards the end of this century in the southeast of the country in summer. Copyright © 2009 Royal Meteorological Society

Influence of climate change on heating and cooling energy demand in Ireland.

[1] The influence of an increased sea surface temperature (SST) on the frequency and intensity of cyclones over the North Atlantic is investigated using two data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by reanalysis data for May to December 1985–2000 at the lateral and lower boundaries, using SST and lateral boundary temperatures. A realistic interannual variation in tropical storm and hurricane counts is simulated. In an idealized sensitivity experiment, SSTs and boundary condition temperatures at all levels are increased by 1 K to ensure that we can distinguish the SST from other factors influencing the development of cyclones. An increase in the count of strong hurricanes is simulated. There is not much change in the location of hurricanes. Generally weaker changes are seen in the extratropical region and for the less extreme events. Increases of 9% in the count of extratropical cyclones and 39% in the count of tropical cyclones with wind speeds of at least 18 m/s are found.

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Regional model simulation of North Atlantic cyclones: Present climate and idealized response to increased sea surface temperature

Improving the ocean and atmosphere in a coupled ocean–atmosphere model by assimilating satellite sea-surface temperature and subsurface profile data

Despite global warming and Arctic sea-ice loss, on average the Antarctic sea-ice extent has not declined since 1979 when satellite data became available. In contrast, climate model simulations tend to exhibit strong negative sea-ice trends for the same period. This Antarctic sea-ice paradox leads to low confidence in 21st-century sea-ice projections. Here we present multi-resolution climate change projections that account for Southern Ocean mesoscale eddies. The high-resolution configuration simulates stable September Antarctic sea-ice extent that is not projected to decline until the mid-21st century. We argue that one reason for this finding is a more realistic ocean circulation that increases the equatorward heat transport response to global warming. As a result, the ocean becomes more efficient at moderating the anthropogenic warming around Antarctica and hence at delaying sea-ice decline. Our study suggests that explicitly simulating Southern Ocean eddies is necessary for providing Antarctic sea-ice projections with higher confidence. 

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Delayed Antarctic sea-ice decline in high-resolution climate change simulations

The Rotated Empirical Orthogonal Function (REOF) method was used to analyse the annual and interannual variability of the precipitation patterns over Ireland as simulated by the Rossby Centre Regional Climate Model Version 2 (RCA2) for the period 1961–2000. The annual and monthly precipitation results show that the model captures the major spatial pattern of each month, but the simulation shows a larger percentage of the variance explained by the leading spatial pattern and tends to have a less pronounced seasonal cycle compared to the observations. The simulation for the wet winter season is in slightly better agreement with the observations compared with the drier summer season. Spatial analysis of the monthly precipitation over a 40-year period shows two major patterns. The first, showing a precipitation maximum in the southwest, is well simulated; the second, showing a maximum in the west and northwest, shows a strongly increasing trend, which is slightly underestimated in the model simulation. Both patterns show seasonal and interannual variability. The wavelet energy density analysis shows that the interannual variability is more important than the seasonal one. In general, the model captures the major spatial and seasonal patterns observed between 1961 and 2000 but slightly overestimates monthly average precipitation levels. Copyright © 2005 Royal Meteorological Society.

Tido Semmler

Papers

Influence of climate change on heating and cooling energy demand in Ireland.

Regional model simulation of North Atlantic cyclones: Present climate and idealized response to increased sea surface temperature

Improving the ocean and atmosphere in a coupled ocean–atmosphere model by assimilating satellite sea-surface temperature and subsurface profile data

Delayed Antarctic sea-ice decline in high-resolution climate change simulations

Validation of simulated precipitation patterns over Ireland for the period 1961–2000