A Weather-Type Classification and Its Application to Near-Surface Wind Climate Change Projections over the Adriatic Region

Andreina Belušić Vozila,Maja Telišman Prtenjak,Ivan Güttler

doi:10.3390/atmos12080948

Andreina Belušić Vozila, Maja Telišman Prtenjak + Show 1 more

Open Access

https://doi.org/10.3390/atmos12080948

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Abstract

The main goal of this study is to present a recently developed classification method for weather types based on the vorticity and the location of the synoptic centers relative to the Adriatic region. The basis of the present objective classification, applied to the Adriatic region, is the subjective classification developed by Poje. Our algorithm considered daily mean sea-level pressure and 500 hPa geopotential height to define one out of 17 possible weather types. We applied the algorithm to identify which weather type was relevant in the generation of the two typical near-surface winds over the Adriatic region, namely Bora and Sirocco. Two high-resolution (0.11°) EURO-CORDEX regional climate models were used, SMHI-RCA4 and DHMZ-RegCM4, forced by several CMIP5 global climate models and analyzed for two 30-year periods: near-present day and mid-21st century climate conditions under the high-end Representative Concentration Pathway (RCP8.5) scenario. Bora and Sirocco days were extracted for each weather type and a distribution over the 30-year period was presented. Our results suggest that in the winter season, climate model projections indicate a reduction in the main cyclonic types relevant in the formation of Bora over the entire Adriatic region and an increase in the number of anticyclonic types relevant in Sirocco events. In contrast, for the summer season, an increase in the main anticyclonic Bora-related weather types is found in the ensemble over the northern Adriatic region.

Highlights

Weather-type (WT) classification has been an active research topic since the 1950s [1,2]
We aimed to find a robust relation between the large-scale parameter, MSLP, and a parameter dependent on the small-scale influence, the near-surface wind field, over the Adriatic region
We have found that the pressure minima generating Bora in the northern Adriatic do not substantially change (±2 hPa) in the middle of the 21st century and could not be the reason for a larger mean wind speed in the northern Adriatic

Summary

Introduction

Weather-type (WT) classification has been an active research topic since the 1950s [1,2]. A comprehensive overview of different methodological approaches for circulation type classification and their application in different fields of research is provided by Huth [5]. Subjective methods [1] are based on the forecaster’s or researcher’s experience, while objective methods can be based on correlation [6], principal component analysis [7], or climate indices [8]. Each of these approaches has its pros and cons, and it is important to note that automatic methods, which are usually considered objective, inevitably have some subjective expert judgments, too

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