The drought in south-eastern Europe in the summer of 2017 heavily affected agricultural production, subsequently decreasing yields of maize. The European Drought Observatory provides Combined Drought Indicator for a 10-day period with coarse spatial resolution of 5 km, which is not localized on field level. It is derived from the combination of Standardized Precipitation Index (SPI), the Soil Moisture Index Anomaly (SMA), and the anomaly of the fraction of absorbed photosynthetically active radiation (FAPAR). Monitoring moisture levels in crops can provide timely information about the presence of abiotic stress in plants and improper development within a growing season. Heat stress and low levels of moisture in maize during summer can thereafter have detrimental consequences on yield. For that reason, in this study, the crop moisture level was estimated at specific parcels by calculating the normalized difference moisture index (NDMI) from Sentinel-2 multispectral imagery during summer months (June–July–August) and the time-series of NDMI were analyzed. Based on the average NDMI value in July, the crop moisture stress (CMS) index was calculated and divided into six classes. Maize yield data on parcel level were provided by an agricultural company for the period 2017 – 2021 in the Backa region of Vojvodina province, Serbia. Yield data for the period 2017-2020 were used to calculate average yield for each class of CMS, whereas yield data from 2021 were used for validation. Mean absolute error (MAE) and root-mean-square error (RMSE) were calculated and were around 1 t/ha. The results showed that the CMS values at a specific parcel could be used for within-season estimation of maize yield and the assessment of drought effects. Also, the CMS index was tested for the 2022 growing season which had drought hazard conditions in south-eastern Europe according to the European Drought Observatory. Expected maize yield reduction estimated for specific scouted fields showed substantial and below average yield values.

How to cite: Živaljević, B., Mimić, G., Blagojević, D., Marko, O., and Brdar, S.: Monitoring of agricultural drought using Crop Moisture Stress index and the estimation of resulting maize yield reduction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-181, https://doi.org/10.5194/egusphere-egu23-181, 2023.

Hydroclimatic extremes like droughts are among the main indicators of climate change in the mountains. They are often associated with elevation-dependent warming. However, terrain features and regional circulation patterns shape local spatial patterns of droughts in the midlatitude mountains. The northeastern area in the Carpathians is suggested to have a less prominent elevation-dependent warming signal in the recent investigations of climate change. Thus, the research aims at identifying the drought distribution response to the features mentioned in the Northeastern Carpathians based on Standardized Precipitation-Evapotranspiration Index (SPEI) and Standardized Precipitation Index (SPI). For the calculation of SPEI and SPI, a newly available homogenized dataset of long gridded time series of essential climate variables for Ukraine, covering the period of 1946–2020 at 0.1°×0.1° spatial resolution is tested. The comparison of both indicators at 3-, 6- at 12-month time scales within the defined period is provided. The interplay effect of the North Atlantic, Mediterranean, and Polar atmospheric circulations is found in different spatial drought patterns throughout the year on southeastern and northwestern macroslopes. Preliminary results confirm that the low-mountain areas with broad-leaf and mixed forests are most exposed to drought intensification especially in the closed inner valleys and on the border of the Western and Eastern Carpathians. The continentality is revealed in the insignificant drying of the low-mountain areas of the Northeastern Carpathians towards the east over time. 

How to cite: Kholiavchuk, D.: Spatial patterns of droughts in the Northeastern Carpathians, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-450, https://doi.org/10.5194/egusphere-egu23-450, 2023.

The anthropogenic impact on natural processes changing their intensity and even trends is evident and confirmed in many researches. The continuous population urban-to-rural and rural-to-urban movements bring a series of the other changes in the environment. This research estimates the impact of the changes of land use and land cover in a time interval of the last almost three decades (1990–2018) on the extreme runoff in more than 40 watersheds with a torrential water regime. Extreme rainfall episodes and watershed characteristics (steep slopes combined with the geology and soil cover of lower water infiltration as well as sparse vegetation cover and artificial and agricultural land use) are the triggers of occurrence of the torrential floods as the most frequent natural hazards in the Central Serbia. The focus is on the border regions of the Central Serbia, so the observed watersheds belong to the Drina river basin in the Western Serbia, the Timok and the Danube river basin in the Eastern Serbia and the Južna Morava river basin and the Egej basin in the Southern Serbia. The observed watersheds are selected according to the physical-geographical characteristics as well as their mentioning in the Inventory of the torrential floods in Serbia.

The main hydrological indicator whose changes are examined is the curve number that is used for the assessment of the hydrological response of the ungauged watershed in an event of extreme rainfall episode. The usage of curve number together with the watershed morphometric parameters (including rainfall data) enables the assessment of the maximal discharges in the flood event. The curve number is a core parameter of the Soil Conservation Service (SCS, today Natural Resources Conservation Service – NRCS) method whose value is in the defined range (0<CN<100) depending on land use. The lower CN, the lower runoff and the higher CN, the higher runoff.

The results revealed consequences of population movements, especially emigration in the last decades from the border regions in terms of changing the land use patterns, and consequently changing the curve number of watershed – its decline, CN_IID or growth, CN_IIG. The dominant decline of the curve numbers is recorded in more than 20 watersheds of the border Eastern and Southern Serbia known for its continuous depopulation processes in last several decades. This led to the abandonment of arable lands that turned to the transitional woodland-shrub and forest areas in the course of time which finally results in lowering of the peak discharges in the torrential flood events. The minor changes of the curve numbers of more than 10 watersheds are dominant in the Drina river basin. For the selected watersheds the changes (decrease/increase) of the maximal discharges of 100- and 200-year return period are calculated according to the land use in 1990 and 2018 and rainfall data up to 1990 and 2018. In the torrential flood mitigation, findings related to these spontaneous positive anthropogenic influence on declining the surface runoff should be followed by the implementation of a set of preventive measures in erosion and torrent control.

How to cite: Petrović, A. and Kostadinov, S.: The surface runoff response to land use changes in border watersheds of the Central Serbia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-762, https://doi.org/10.5194/egusphere-egu23-762, 2023.

Ten-day self-calibrating Palmer Drought Severity Index (scPDSI) has been computed, based on observed 10-day mean air temperature, relative humidity and precipitation totals, as a parameter of drought impact on grain yield of 32 marketleading maize hybrids in 2017 and 2018 over 8 experimental locations in Pannonian part of Croatia. In addition, time series of the same climate variables for the closest “official” weather stations of Croatian Meteorological and Hydrological Service (DHMZ) for the period 1981-2018 have been used for scPDSI calibration and calculation. According to 10-day scPDSI, 2018 showed to be a „regular year“ while 2017 had a „moderate drought“ causing a maize grain yield reduction of 13%, compared to 2018. In spite some differences in climate aridity of central and eastern Croatia, a significant correlation between summer months’10-day scPDSI and maize grain yield has been determined. The highest average correlation coefficients across all maize hybrids for three summer months were determined for the last decade (10-day period) of July and consecutive three decades in August. The dependence of grain yield on scPDSI value is not the same for all hybrids indicating various tolerances of different hybrids to drought stress. The grain yield reduction was primarily affected by insufficient grain filling (smaller 1000-kernel weight) and to some extent by reduction of number of grains. For practical use, within the set of given 32 tested hybrids, the level of determined drought tolerance of a hybrid has to be considered along with its relative grain yield performance.

How to cite: Pandžić, K., Likso, T., Pejić, I., and Šarčević, H.: Application of the Self-calibrated Palmer Drought Severity Index for Estimation of Drought Impact on Maize Grain Yield in Pannonian Part of Croatia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4482, https://doi.org/10.5194/egusphere-egu23-4482, 2023.

In the last few years, several works have studied rainfall regime changes with the increase of temperature as a result of global warming. These changes, documented mainly in northern Europe, still need to be clarified in the Mediterranean area. Many studies have identified sometimes contradictory trends according to the type of data used, the methodology, and the daily or subdaily types of events. Therefore, an in-depth investigation of the Mediterranean area is required for the definition of more certain future scenarios.

In this study, we examined a database with more than 1,000 raingauges and thermometers in northern and central Italy to analyze the rapid extreme precipitation events (EPEs) in relation to temperature. This large database covers a low rainfall accumulation period (RAP) that allowed us to study the relationship between temperature and rainfall and to distinguish rapid from long events related to rainfall intensity. 

The results show different relationships between rainfall and temperature regarding seasons, RAPs, rainfall intensity, and geographical factors. The high spatial density of the database made it possible to identify spatial clusters with homogenous characteristics influenced mainly by geographical factors. With an increase in temperature, the wet season is characterized by a general increase in rainfall with a higher surge for intense and fast events. Instead, the dry season shows a general rainfall decrease for less intense and longer events, but an increase in rapid and more intensive rainfall events. This outcome has further implications involving a future decrease in water availability and an increase of the EPEs, causing an extremization of the climate during the dry season for northern and central Italy.

How to cite: Luppichini, M., Bini, M., Giannecchini, R., and Zanchetta, G.: The effects of the temperature increase on the rainfall regimes in north-central Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5430, https://doi.org/10.5194/egusphere-egu23-5430, 2023.

Floods are natural phenomena, which can turn into disasters and cause widespread damage, health problems and deaths. This is particularly the case where rivers have been denied from their natural floodplains and are limited by embankments, and where housing and industrial buildings have been constructed in areas that are naturally liable to flooding. However, during the last few decades, flood observations from different parts of Europe do not show a clear increase in flood occurrence rate (Blöschl et al., 2019). In the present paper we present longer-term records of winter and summer floods in one of the largest river of Southeast Europe, the Sava River for the 1926-2021 period. We analysed three group of events that were based on three flood protection levels in Republic of Serbia defined for Sremska Mitrovica station. Regular protection level is set at 4120 m³/s and emergency flood defense level which is set at 5120 m³/s, that is, minor events are up to the regular protection level, strong events are up to the emergency level and extreme events are above emergency flood defense level. For the past 95 years, we find a decrease in both summer and winter flood occurrence rates. The reduction in winter flood occurrence can partly be attributed to reduced amount of precipitation during this period of the year. Further, on the basis of these data and methods, we find that for the Sava River can be stated the following: (1) downward but not significant trends in winter flood risk during the observed period, (2) Downward trends of summer floods was also observed, with only strong events being statistically significant. This decrease can be partially due to a projected decrease in cyclone frequency in the Mediterranean region. Presented results clearly demonstrate decreasing flood occurrence rate of the Sava River, as a consequence of decreasing precipitation and increasing evaporation (due to increasing temperature). 

References

Blöschl, G., Hall, J., Parajka, J., Perdigão, A. P. R., Merz, B., Arheimer, B., Aronica, T. G., Bilibashi, A., Bonacci, O., Borga, M., Čanjevac, I., Castellarin, A., Chirico, B. G., Claps, P., Fiala, K., Frolova, N., Gorbachova, L., Gül, A., Hannaford, J., Harrigan, S., Kireeva, M., Kiss, A., Kjeldsen, R. T., Kohnová, S., Koskela, J. J., Ledvinka, O., Macdonald, N., Mavrova-Guirguinova, M., Mediero, L., Merz, R., Molnar, P., Montanari, A., Murphy, C., Osuch, M., Ovcharuk, V., Radevski, I., Rogger, M., Salinas, L. J., Sauquet, E., Šraj, M., Szolgay, J., Viglione, A., Volpi, E., Wilson, D., Zaimi, K. & Živković, N. (2019). Changing climate both increases and decreases European river floods. Nature 573 (7772), 108–111. https://doi.org/10.1038/s41586-019-1495-6.

Acknowledgements

This research was supported by ExtremeClimTwin project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 952384.

How to cite: Leščešen, I., Basarin, B., Mudelsee, M., and Wilby, R. L.: Is the flood occurrence rate decreasing in Southeast Europe?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6031, https://doi.org/10.5194/egusphere-egu23-6031, 2023.

In May 2014, the Balkan Region experienced exceptionally heavy rainfall. Between May 14 and May 19, 2014, there was a devastating flood in Serbia, Croatia, and Bosnia & Herzegovina. The event shattered a number of historical records and seriously endangered economies across the region. The close proximity of human settlements, infrastructure (houses, buildings, bridges), and agricultural land to flood plains further amplified the destructive effects. Although atmospheric thermodynamic and dynamic processes were used to describe this exceptional rainfall event, there was no mention of how climate change may have contributed to it. We show that the probability of this brief and powerful event occurring without human-caused climate change were incredibly low. Our research aims to demonstrate how climate change may have affected the likelihood that this extreme rainfall event will occur as well as to outline the difficulties in doing so. This was accomplished using the methods recommended by the World Weather Attribution (WWA) group. We examine whether and how much human-caused climate change has affected the likelihood and intensity of the rainfall over the Balkans as well as the peak 5-day precipitation in order to achieve this. We consider both historical weather data and climate models with and without anthropogenic forcing. The findings suggested that one of the key elements in determining event likelihood calculations is domain selection. Given the current situation and the possibility for further excessive rainfall over the Balkans, it is critical to enhance water management and lessen vulnerability to extreme rainfall.

Acknowledgement:
This research was supported by ExtremeClimTwin project, which has received funding from the
European Union’s Horizon 2020 research and innovation programme under grant agreement No 952384.

How to cite: Podraščanin, Z., Basarin, B., Iles, C., and Daloz, A. S.: Attribution of extreme rainfall associated with the Balkans floods of May 2014, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11863, https://doi.org/10.5194/egusphere-egu23-11863, 2023.

Waterlogging or inland flooding occurs when excess water accumulates in the soil, leading to saturated conditions and reduced oxygen levels. Waterlogging affects lowlands, flat terrain and alluvial plains with limited runoff and increased water accumulation, which is typical for large parts of the Pannonian and Peripannonian regions of Hungary, Serbia and Croatia. These inundations cause substantial problems, primarily in agriculture trough crop loss, soil degradation and pollution, as well as damage to infrastructure and various socio-economic challenges.

Precipitation is the primary climatic factor that affects waterlogging, in combination with air temperature, humidity, evaporation, and other local hydrogeological, pedological, geomorphological and anthropogenic factors.

Changes in atmospheric circulation patterns influence the amount, intensity, and seasonality of precipitation which determine the extent and duration and subsequent negative impact of inland flooding.

Based on climate reanalysis data (ERA5) and regional climate models we examined precipitation trends in the period from 1950 to 2022 and from 2023 to 2070. Having the most significant effect on waterlogging the amount and intensity of precipitation in winter and spring season were assessed in detail. While the models indicate generally less rainfall in the future, the seasonal distribution and the increase in frequency of extreme precipitation events will favor the periodic occurrence of waterlogging in the region in the comming decades. The results of this study can be implemented in planning agricultural and water management activities.

Acknowledgements:

This research was supported by ExtremeClimTwin project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 952384.

How to cite: Mesaroš, M., Pavić, D., and Leščešen, I.: Effects of changing atmospheric circulation patterns on waterlogging potential in Southeast Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14880, https://doi.org/10.5194/egusphere-egu23-14880, 2023.

How to cite: Bueechi, E., Fischer, M., Crocetti, L., Trnka, M., Zappa, L., Grlj, A., and Dorigo, W.: Maize and wheat yield forecasting in the Pannonian Basin using extreme gradient boosting and its performance in years of severe drought, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15519, https://doi.org/10.5194/egusphere-egu23-15519, 2023.

The extreme discharges in the Danube Lower Basin, highlighted by the Generalized Extreme Value theory, were analyzed by their internal and external drivers. For the former, some large and regional scales climate indices, such as the North Atlantic Oscillation (NAO), the Greenland-Balkan Oscillation (GBO), and the Palmer type drought indices, respectively, were used. For the latter the sunspot number (SSN) time series was considered.

Wavelet coherence for multiple variables, different types of filters and regression models were applied.

The results obtained in this study depend on the season, and can be beneficial for different decision-makers for a good management of water resources in case of extreme events.

How to cite: Mares, C., Mares, I., Dobrica, V., and Demetrescu, C.: On external and internal drivers of extreme discharges in the Danube Lower Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6044, https://doi.org/10.5194/egusphere-egu23-6044, 2023.