REDUCING WARM BIAS OVER THE NORTH-EASTERN EUROPE IN A REGIONAL CLIMATE MODEL

Large warm bias in near-surface temperature during winter was detected over northeastern Europe in simulations with RegCM4 regional climate model when compared to observational dataset. Modifications to alleviate warm bias included reductions of the low-level cloud cover fraction and the minimum turbulent mixing in stable planetary boundary layer. When implemented, these modifications reduced warm bias up to 50% and did not degrade, or substantially impact, the variables analyzed outside the region and season considered. Validations of the planetary boundary layer and cloud features were limited due to unavailability of appropriate observational data at climatological timescales

Očekivano toplinsko opterećenje Dubrovnika, Osijeka, Rijeke, Zadra i Zagreba prema projekcijama regionalnih klimatskih modela

This paper examines the expected future heat load in five Croatian cities: Dubrovnik, Zadar, Rijeka, Zagreb, and Osijek. The heat load is estimated by temperature-related climate indices and mean, maximum and minimum daily temperatures obtained by climate simulations using two different regional climate models (DHMZ-RegCM4 and SMHI-RCA4) with a horizontal resolution of 12.5 km, forced with two global climate models (EC-EARTH and MPI-ESM-MR/LR) for two different greenhouse gas concentration scenarios (RCP4.5 and RCP8.5). By comparing these variables for the period 2041–2070 with respect to the current climate (defined as that of the period 1991–2020), a significant increase in mean, maximum and minimum temperatures was observed in all analysed combinations of regional and global climate models for all analysed cities. Although there is a difference in results depending on the combination of regional and global models, the largest increase is mainly found in the warm part of the year (April-October), with the strongest warming of Dubrovnik and Rijeka. Due to similar trends in minimum and maximum temperatures, the trend in the daily temperature range is weak. Under warmer climate conditions, the number of days with a maximum air temperature above 25 °C increases in all considered cities (especially in Dubrovnik), as does the number of days with a minimum air temperature exceeding 20 °C (especially in Rijeka and Zadar). Furthermore, a reduction in the number of days with maximum and minimum temperatures below 0 °C is projected for all cities. Nevertheless, some differences are found between coastal and inland cities caused by local factors.U ovom radu ispitano je očekivano buduće toplinsko opterećenje u pet hrvatskih gradova: Dubrovniku, Zadru, Rijeci, Zagrebu i Osijeku. Toplinsko opterećenje je procijenjeno pomoću temperaturnih klimatskih indeksa te srednjih, maksimalnih i minimalnih dnevnih temperatura na temelju simulacija dvaju regionalnih klimatskih modela horizontalne rezo-lucije 12,5 km (DHMZ-RegCM4 i SMHI-RCA4), uz rubne uvjete dobivene dvama globalnim klimatskim modelima (EC-EARTH i MPI-ESM-MR/LR), za dva različita scenarija koncentracija stakleničkih plinova (RCP4.5 i RCP8.5). Uspoređivanjem ovih varijabli za razdoblje 2041.–2070. u odnosu na klimu iz razdoblja 1991.–2020., uočen je značajan porast srednjih, maksimalnih i minimalnih temperatura u svim analiziranim kombinacijama regionalnih i globalnih klimatskih modela za sve promatrane gradove. Iako postoje određene razlike u rezultatima ovisno o kombinaciji regionalnog i globalnog modela, najviše se ističe porast u toplom dijelu godine (travanj-listopad) s najvećim iznosima za Dubrovnik i Rijeku. Zbog približno jednakih trendova maksimalne i minimalne temperature, trend dnevnih raspona temperature je malog iznosa. U uvjetima toplije klime se u svim promatranim gradovima povećava broj dana s maksimalnom temperaturom zraka iznad 25 °C (posebice u Dubrovniku) i broj dana s minimalnom temperaturom iznad 20 °C (osobito u Rijeci i Zadru). Nadalje, u svim je gradovima dobiveno smanjenje broja dana s maksimalnom i minimalnom temperaturom ispod 0 °C. Ipak, uočavaju se određene razlike između kontinentalnih i obalnih gradova koje su uvjetovane lokalnim faktorima

Očekivano toplinsko opterećenje Dubrovnika, Osijeka, Rijeke, Zadra i Zagreba prema projekcijama regionalnih klimatskih modela

This paper examines the expected future heat load in five Croatian cities: Dubrovnik, Zadar, Rijeka, Zagreb, and Osijek. The heat load is estimated by temperature-related climate indices and mean, maximum and minimum daily temperatures obtained by climate simulations using two different regional climate models (DHMZ-RegCM4 and SMHI-RCA4) with a horizontal resolution of 12.5 km, forced with two global climate models (EC-EARTH and MPI-ESM-MR/LR) for two different greenhouse gas concentration scenarios (RCP4.5 and RCP8.5). By comparing these variables for the period 2041–2070 with respect to the current climate (defined as that of the period 1991–2020), a significant increase in mean, maximum and minimum temperatures was observed in all analysed combinations of regional and global climate models for all analysed cities. Although there is a difference in results depending on the combination of regional and global models, the largest increase is mainly found in the warm part of the year (April-October), with the strongest warming of Dubrovnik and Rijeka. Due to similar trends in minimum and maximum temperatures, the trend in the daily temperature range is weak. Under warmer climate conditions, the number of days with a maximum air temperature above 25 °C increases in all considered cities (especially in Dubrovnik), as does the number of days with a minimum air temperature exceeding 20 °C (especially in Rijeka and Zadar). Furthermore, a reduction in the number of days with maximum and minimum temperatures below 0 °C is projected for all cities. Nevertheless, some differences are found between coastal and inland cities caused by local factors.U ovom radu ispitano je očekivano buduće toplinsko opterećenje u pet hrvatskih gradova: Dubrovniku, Zadru, Rijeci, Zagrebu i Osijeku. Toplinsko opterećenje je procijenjeno pomoću temperaturnih klimatskih indeksa te srednjih, maksimalnih i minimalnih dnevnih temperatura na temelju simulacija dvaju regionalnih klimatskih modela horizontalne rezo-lucije 12,5 km (DHMZ-RegCM4 i SMHI-RCA4), uz rubne uvjete dobivene dvama globalnim klimatskim modelima (EC-EARTH i MPI-ESM-MR/LR), za dva različita scenarija koncentracija stakleničkih plinova (RCP4.5 i RCP8.5). Uspoređivanjem ovih varijabli za razdoblje 2041.–2070. u odnosu na klimu iz razdoblja 1991.–2020., uočen je značajan porast srednjih, maksimalnih i minimalnih temperatura u svim analiziranim kombinacijama regionalnih i globalnih klimatskih modela za sve promatrane gradove. Iako postoje određene razlike u rezultatima ovisno o kombinaciji regionalnog i globalnog modela, najviše se ističe porast u toplom dijelu godine (travanj-listopad) s najvećim iznosima za Dubrovnik i Rijeku. Zbog približno jednakih trendova maksimalne i minimalne temperature, trend dnevnih raspona temperature je malog iznosa. U uvjetima toplije klime se u svim promatranim gradovima povećava broj dana s maksimalnom temperaturom zraka iznad 25 °C (posebice u Dubrovniku) i broj dana s minimalnom temperaturom iznad 20 °C (osobito u Rijeci i Zadru). Nadalje, u svim je gradovima dobiveno smanjenje broja dana s maksimalnom i minimalnom temperaturom ispod 0 °C. Ipak, uočavaju se određene razlike između kontinentalnih i obalnih gradova koje su uvjetovane lokalnim faktorima

Weakly nonlinear Prandtl model for simple slope flows

The Prandtl model couples, probably in the most succinct way, basic boundary-layer dynamics and thermodynamics for pure anabatic and katabatic flows over inclined surfaces by assuming a one-dimensional steady-state balance between buoyancy and turbulent friction. Although the classic Prandtl model is linear, having an a priori assigned vertically constant eddy diffusivity and heat conductivity, K, in this analytic work we partly relax both of these restrictions. The first restriction is loosened by using a weakly nonlinear approach where a small parameter, ε, controls feeding of the flow-induced potential temperature gradient back to the environmental potential temperature gradient, because the former, below the katabatic jet, can be 20-50 times stronger than the latter, background or free-flow gradient. An appropriate range of values for ε, controlling the weak nonlinearity for pure katabatic flow, is provided. In this way, the near-surface potential temperature gradient becomes stronger and the corresponding katabatic jet somewhat weaker (at a slightly lower height) than that in the classic Prandtl solution. The second restriction is partly relaxed by using a prescribed, gradually varying K with distance from the underlying surface, all within the usual validity of the zero-order Wentzel-Kramers-Brillouin approximation to solve the coupled differential equations. The new model is compared with the glacier wind data from the Pasterze experiment (PASTEX-94), Austria. Further discussion includes gradient Richardson number consideration and an application to simple anabatic flows. The model may be applied for estimation and interpretation of the wind affecting glacier mass balance and air pollution

RegCM4 simulacije za potrebe prilagodbe klimatskim promjenama: nivo 2

oai:repozitorij.meteo.hr:meteo_11U ovom repozitoriju možete naći pristup klimatskim simulacijama obavljenim za potrebe izrade Nacrta Strategije prilagodbe klimatskim promjenama (MZOE, 2017). Vlasnik podataka je MZOE. Više detalja o Nacrtu Strategije prilagodbe klimatskim promjenama dostupno je na adresi: http://prilagodba-klimi.hr/ Specifični skup podataka (tzv. nivo 2) sadrži izvorne rezultate modela RegCM4 na čitavoj domeni (Europa i susjedna područja), svakih 3h, za sve prizemne varijable unutar tzv. SRF datoteka. Za izlaz modela RegCM4 na čitavoj domeni (Europa i susjedna područja), svaka 6h, za sve 3D varijable unutar tzv. ATM i RAD datoteka koristiti skup podataka nivo 3 (prema posebnom zahtjevu: https://repozitorij.meteo.hr/protokol-pristupa-podacima)

RegCM4 simulacije za potrebe prilagodbe klimatskim promjenama: nivo 1

U ovom repozitoriju možete naći pristup klimatskim simulacijama obavljenim za potrebe izrade Nacrta Strategije prilagodbe klimatskim promjenama (MZOE, 2017). Vlasnik podataka je MZOE. Više detalja o Nacrtu Strategije prilagodbe klimatskim promjenama dostupno je na adresi: http://prilagodba-klimi.hr/ Specifični skup podataka (tzv. nivo 1) sadrži dnevne srednjake izvornih rezultata na širem području Hrvatske. Za rezultate na finijoj vremenskoj skali te na čitavom području Europe uzeti u obzir tzv. nivo 2.Skup simulacija obavljen je regionalnim klimatskim modelom RegCM4 (Giorgi i sur., 2012) za razdoblje 1971. do 2070. na prostornoj rezoluciji 12.5 km, te za razdoblje 1971.-2099./2100. na prostornoj rezoluciji 50 km. Kao rubni uvjeti korišteni su rezultati CMIP5 globalnih klimatskih modela: EC-EARTH, HadGEM2-ES, CNRM-CM5 i MPI-ESM-MR. Do simulirane 2005. godine globalni klimatski modeli i RegCM4 koriste izmjerene koncentracije stakleničkih plinova, a za razdoblje poslije 2005. pretpostavljena su dva IPCC scenarija: RCP4.5 i RCP8.5 (Moss i sur., 2010). Simulacije RegCM4 modelu su obavljene prema preporukama i dizajnu CORDEX i EURO-CORDEX inicijativa

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

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