Analysis of surface downwelling shortwave and longwave radiation for the European domain in the historical and future climate

Bilanca zračenja pri tlu izrazito je bitan faktor koji direktno utječe na klimu, a dolazno prizemno kratkovalno (RSDS) i dugovalno (RLDS) zračenje ključan su dio bilance zračenja pri tlu. U radu su analizirane vrijednosti RSDS i RLDS iz triju EURO-CORDEX regionalnih klimatskih modela (DMI-HIRHAM5, GERICS-REMO2015 i KNMI-RACMO22E) forsiranih s jednim globalni klimatskim modelom (MOHC-HadGEM2-ES). Analiza je rađena za europsku domenu (izuzev sjeverne Europe zbog manjeg broja dostupnih podataka), s posebnim fokusom na šire područje Republike Hrvatske. Za referentne vrijednosti RSDS i RLDS korišten je CLARA-A2 set podataka. Ispitane su sustavne pogreške svakog od modela te njihova prostorna razdioba. Regionalni klimatski modeli (RCMs) uglavnom podcjenjuju vrijednosti RSDS nad morem, dok nad kopnom precjenjuju, a najveće razlike između CLARA-A2 podataka i podataka RCMs mogu se vidjeti u proljeće i ljeti na područjima velikih nadmorskih visina, poput Alpa. Sustavne pogreške RLDS manje su te nemaju pravilnu razdiobu kao sustavne pogreške RSDS, a do blagih precjenjivanja RLDS dolazi iznad morskih površina. U radu je proučavan i signal budućih klimatskih promjena do kraja 21. stoljeća za scenarij RCP4.5. Usporedbom četiri dvadesetogodišnja klimatska razdoblja u budućnosti s referentnim razdobljem (1985.-2004.) uočeno je da sjeverni dio promatrane europske domene većinom bilježi pad RSDS, dok jugoistočni i zapadni dio bilježe porast RSDS. RCMs jednoglasno simuliraju porast RLDS u budućnosti, a najveći porast uočava se na prostoru Sredozemlja ljeti. Štoviše, promatrajući vremenski niz RLDS detektiran je statistički značajan porast RLDS (1,67-1,76 W/m2) za europsku domenu i (1,76-1,78 W/m2) za hrvatsku domenu. Ipak, generalno regionalni klimatski modeli sugeriraju stagnaciju RLDS nakon 2070. godine, što odgovara stagnaciji CO2 koncentracija za RCP4.5 scenarij. Za razliku od RLDS, RSDS ne bilježi jasan trend, iako određeni modeli sugeriraju blagi porast. Također, uočene su naznake posvjetljivanja (engl. brightening) od 2030.-ih do 2060.-ih, nakon kojih započinje razdoblje zatamnjivanja (engl. dimming).The surface radiation budget is a crucial factor that directly affects the climate, and surface downwelling shortwave (RSDS) and longwave (RLDS) radiation are essential parts of the surface radiation budget. In the thesis, RSDS and RLDS values from three EURO-CORDEX regional climate models (DMI-HIRHAM5, GERICS-REMO2015 and KNMI-RACMO22E) forced with one global climate model (MOHC-HadGEM2-ES) were analysed. The analysis was done for the European domain (except Northern Europe due to the smaller number of available data) with a particular focus on the wider area of the Republic of Croatia. The CLARA-A2 dataset was used for the reference values of RSDS and RLDS. Systematic errors of each model, as well as their spatial distribution, were examined. Regional climate models (RCMs) mostly underestimate RSDS values over the sea, while over the European land they overestimate RSDS values. The biggest differences between CLARA-A2 data and RCMs data can be seen in spring and summer in high-altitude areas, such as the Alps. Compared to RSDS errors, the systematic errors of the RLDS are usually lower. RLDS errors do not have a regular spatial distribution, as RSDS does, but the slight overestimations of RLDS over sea surfaces were noted. In the thesis, the signal of future climate changes until the end of the 21st century for RCP4.5 scenario was also explored. By comparing the reference period (1985-2004) with four twenty-year climate periods in the future, it was observed that the northern part of the observed European domain mostly recorded a decline in RSDS, while the southeastern and western parts recorded an increase in RSDS. RCMs unanimously simulate an increase in RLDS in the future with the largest increase in the Mediterranean area in the summer season. Moreover, observing the RLDS time series, the statistically significant increases in RLDS (1.67-1.76 W/m2) were detected for the European domain, as well as for the Croatian domain (1.76-1.78 W/m2). However, regional climate models suggest stagnation of RLDS after 2070, which corresponds to stagnation of CO2 concentrations for the RCP4.5 scenario. Unlike the RLDS, the RSDS does not show a clear trend, although some models suggest a slight increase. Furthermore, indications of the brightening period were observed from the 2030s to the 2060s, after which the dimming period can be noticed