Heat Wave Events over Georgia Since 1961: Climatology, Changes and Severity

Ina Keggenhoff,Mariam Elizbarashvili,Lorenz King

doi:10.3390/cli3020308

Abstract

The Caucasus Region has been affected by an increasing number of heat waves during the last decades, which have had serious impacts on human health, agriculture and natural ecosystems. A dataset of 22 homogenized, daily maximum (Tmax) and minimum (Tmin) air temperature series is developed to quantify climatology and summer heat wave changes for Georgia and Tbilisi station between 1961 and 2010 using the extreme heat factor (EHF) as heat wave index. The EHF is studied with respect to eight heat wave aspects: event number, duration, participating heat wave days, peak and mean magnitude, number of heat wave days, severe and extreme heat wave days. A severity threshold for each station was determined by the climatological distribution of heat wave intensity. Moreover, heat wave series of two indices focusing on the 90th percentile of daily minimum temperature (CTN90p) and the 90th percentile of daily maximum temperature (CTX90p) were compared. The spatial distribution of heat wave characteristics over Georgia showed a concentration of high heat wave amplitudes and mean magnitudes in the Southwest. The longest and most frequently occurring heat wave events were observed in the Southeast of Georgia. Most severe heat wave events were found in both regions. Regarding the monthly distribution of heat waves, the largest proportion of severe events and highest intensities are measured during May. Trends for all Georgia-averaged heat wave aspects demonstrate significant increases in the number, intensity and duration of low- and high-intensity heat waves. However, for the heat wave mean magnitude no change was observed. Heat wave trend magnitudes for Tbilisi mainly exceed the Georgia-averages and its surrounding stations, implying urban heat island (UHI) effects and synergistic interactions between heat waves and UHIs. Comparing heat wave aspects for CTN90p and CTX90p, all trend magnitudes for CTN90p were larger, while the correlation between the annual time-series was very high among all heat wave indices analyzed. This finding reflects the importance of integrating the most suitable heat wave index into a sector-specific impact analysis.

Highlights

Heat waves are among the most threatening meteorological hazards related to global warming posing impacts to society, economy and ecology
According to the Intergovernmental Panel on Climate Change (IPCC) anthropogenic influences on climate since the mid-20th century resulted in a change of frequency and intensity of daily temperature extremes and doubled the probability of occurrence of heat waves in some regions of the world [9] and the global averaged frequency, duration and intensity of heat waves are projected to increase [10,11,12,13]
The aim of this study is to provide a better understanding of the climatology and changes in the frequency, duration and intensity of summer heat wave events over Georgia and the case study Tbilisi, as the most urbanized city in Georgia

Summary

Introduction

Heat waves are among the most threatening meteorological hazards related to global warming posing impacts to society, economy and ecology. According to the Intergovernmental Panel on Climate Change (IPCC) anthropogenic influences on climate since the mid-20th century resulted in a change of frequency and intensity of daily temperature extremes and doubled the probability of occurrence of heat waves in some regions of the world [9] and the global averaged frequency, duration and intensity of heat waves are projected to increase [10,11,12,13]. The fact that in West Asia heat waves are likely to increase in frequency and/or duration, makes it even more important to investigate observed heat wave changes with special regards to regional impacts, the communities involved, and the climatic fields affected [13].

Objectives

Results

Conclusion