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Wednesday, 12 March 2014
11:15 - 12:45 Wind speed predictions: Are we at the limit of our knowledge or can we improve?
Resource Assessment  


Room: Ponent
Session description

No new long-term correction methods have appeared for years and it is possible that current techniques are optimal. There are several issues which affect any long-term correction analysis:

… from the mundane: the optimum reference period? how do we measure success? re-analysis data or ground based stations? non-integer years of data?

… to the exotic: atmospheric stability, climate change decadal variations, sun spots activity and solar cycles.

It is likely that long-term correction techniques which consider these may provide more reliable predictions than has previously been possible.

This session describes new long-term correction methodologies and compares the results with those of conventional methods. Innovative techniques to improve the representativeness of long-term data series are discussed, different long-term data series are compared and conclusions on the decadal-scale variability of the wind speed are presented. The overall objective of this session is to give insight on how these developments contribute to a greater certainty in future wind speed predictions.

Learning objectives

  • Evaluate innovative methods to improve the representativeness of long-term data series and the overall accuracy of long-term extrapolations
  • Compare new long-term correction methods to traditional methods
  • Understand how a more accurate description of the decadal-scale variability of the wind speed contributes to the reduction of the uncertainty in the long-term corrected wind speed
Lead Session Chair:
Sónia Liléo, Kjeller Vindteknikk AS, Sweden

Co-chair(s):
Steve Ross, 3Tier
Gil Lizcano Vortex, Belgium
Co-authors:
Lizcano Gil (1) F P
(1) Vortex, Brussels, Belgium (2) IC3, Barcelona, Spain

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Gil Lizcano has more that 15 years working on the climate and wind meteorology sector. He worked in both academia and private industry where he gained a combined experience in climate analysis and mesoscale wind modeling. He worked for six years at Environmental Change Institute at the University of Oxford, participating in different international projects dealing with climate change impact assessment.
In 2008, he joined Vortex and lead the companies R&D efforts. Among his responsibilities, he is in charge of providing a climate knowledge for the modeling lines implemented by Vortex.

Abstract

How many years are enough? Advancing knowledge of low frequency wind resource variability of wind conditions

Introduction

How many years of climate data are enough? This recurrent and polemical concern to define the optimal long-term reference period can be misunderstood if incomplete climate meaning is attached. Otherwise, any given answer could be based on a conservative precaution to avoid overestimating AEP, due to the limitation of observed data and our difficulties to deal with unexpected climate anomalies like trends or extremes seasons.
This work explores the implications that low frequency variability has on the long-term characterization of wind resource, with special attention to anomalous periods.

Approach

Different statistical techniques explore the role of internal climate variability as a driver of extreme annual anomalies in wind resources. Observational proxy such as the 20th Century and satellite-era latest reanalysis projects, and downscaled data from those reanalyses using the WRF mesoscale model are invaluable sources of information to study the implication of low frequency modes in the assessment of wind resource variability.

In a second stage, investigation of the operational seasonal and CMIP5 multi-model ensemble forecast datasets are carried out to understand and assess the skill and uncertainty of future predictions of changes in wind variability.

Main body of abstract

Many publications have highlighted the predominant role of the NAO as a low frequency modulator of inter-annual variability for European climates. Less understood is its actual role to change the inter-annual variability of the wind regimes across different decades.
The NAO, as a climate phenomenon, is characterised by two opposite phases acting as, for instance, as a switch for the passage of western mechanical energy to the continent (storms) and to allow/block the tropical warm water contents. Multiyear low and high wind periods can be, up to a certain level, associated with different states of the NAO affecting the distribution of European wind anomalies.

By using simple statistical techniques based on signal de-noising and composite analysis, qualitative relationship between NAO and the wind regimes is traced across the 20th Century, with a focus on changes in extreme seasonal amplitude and frequency. An impact assessment for the magnitude of the modulation is made for the last three decades using ERA-Interim and WRF downscaled data.
An uncertainty separation method based on the signal-to-noise approach, commonly employed for climate model research, is adapted to estimate long-term wind resource uncertainty, and providing a quantifiable contribution of each source to the overall uncertainty.

Conclusion

The work presents an analysis of the last 110 years of wind regime variability for Europe based on the information provided by the century-long re-analysis. The results underline the marked role of internal variability, represented by the NAO, to modulate the frequency and amplitude of anomalous high/low winter seasons. Examples of changes in the structure of its variability across different decades are shown. The implications of these modulations are translated to long-term uncertainty calculations. How many years are enough? It may be that the answer depends on the fraction of uncertainty or risk that we want to assume.


Learning objectives
- Provide a general overview of the role of inter-decadal climate variability to modulate wind regimes
- Understand why we should pay attention to the internal climate variability to narrow long-term uncertainty
- Show a practical study of a main climate mode of variability that has an effect across Europe
- Introduce some uncertainty measures of the natural climate variability for Europe, adapted to wind resource analysis