Naslov
The effect of winter and summer NAO on summer urban heat load in Zagreb

Autori
Nimac, Irena ; Herceg Bulić, Ivana ; Žuvela- Aloise, Maja ; Žgela, Matej

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Meteorološki izazovi 8 - Zrak koji udišemo, zrak koji prognoziramo, Kratki sazetci / - , 2022, 32-32

Skup
Meteorološki izazovi 8 - Zrak koji udišemo, zrak koji prognoziramo

Mjesto i datum
Zagreb, Hrvatska, 28.04.2022. - 29.04.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Domaća recenzija

Ključne riječi
Urban heat load, North-Atlantic Oscillation, Urban heat island

Sažetak
In this study the effect of North-Atlantic Oscillation (NAO) over Zagreb area is investigated. Specifically, the role of indirect (lagged) and direct NAO effect are analyzed by different combinations of winter (wNAO) and summer (sNAO) NAO index. Based on the measurements at station Zagreb-Maksimir in the period 1949-2019, significant correlation is obtained between sNAO index and number of summer days (Tx25). However, when wNAO index was additionally included in multiple linear regression (MLR), even stronger correlation is found with all MLR coefficients being significant. It is demonstrated that the combination of positive wNAO followed by negative sNAO results in the strongest increase in heat load compared to the reference situation, while the opposite combination leads to the strongest decrease. Combinations of the same polarity of wNAO and sNAO phases are generally associated with weak response due to their opposing effect on temperature and precipitation over area under the study. This change in the amplitude of the heat load is also confirmed in simulations made by urban climate model. However, modelling approach enabled us to investigate the spatial variability of the Tx25 field over Zagreb. It is found that NAO combination leading to longer dry conditions results in weaker spatial gradient of the Tx25 due to decreased cooling efficiency of vegetation. Mentioned results indicate the importance of slower components of climate system, in this case soil. The assumption that soil moisture is significant link between wNAO and summer heat load is confirmed by analogue analysis based on standardized precipitation evapotranspiration index (SPEI) determined for station Zagreb-Maksimir. Furthermore, impact of drought conditions on spatial variability of the urban heat load is confirmed by the analysis of Landsat-8 land surface temperature data. The results of this research might be useful for urban climate mitigation purposes, especially for planning of irrigation of vegetation in situations when seasonal forecasts indicate warmer and drier conditions.

Izvorni jezik
Engleski

Znanstvena područja
Geofizika

POVEZANOST RADA