Extreme Temperature Events in Serbia in Relation to Atmospheric Circulation

In this study, extremely warm and cold temperature events were examined based on daily maximum (Tx) and minimum (Tn) temperatures observed at 11 stations in Serbia during the period 1949–2018. Summer days (SU), warm days (Tx90), and heat waves (HWs) were calculated based on daily maximum temperatures, while frost days (FD) and cold nights (Tn10) were derived from daily minimum temperatures. Absolute maximum and minimum temperatures in Serbia rose but were statistically significant only for Tx in winter. Positive trends of summer and warm days, and negative trends of frost days and cold nights were found. A high number of warm events (SU, Tx90, and HWs) were recorded over the last 20 years. Multiple linear regression (MLR) models were applied to find the relationship between extreme temperature events and atmospheric circulation. Typical atmospheric circulation patterns, previously determined for Serbia, were used as predictor variables. It was found that MLR models gave the best results for Tx90, FD, and Tn10 in winter.

Marine heatwaves and cold-spells, and their impact on fisheries in the southern North Sea

<p>The marine environment experiences temperature variability both in the short and long term due to a combination of variable surface heating, ocean transport and mixing effects. The impact of temperature anomalies on the marine ecosystem depends on their duration and amplitude compared with timescales of the ecological response and the susceptibility of various components of the ecosystem to the change. Even relatively short events can affect reproduction and growth, and potentially cause mortality when organism tolerance limits are exceeded.<br>We focus on sustained (lasting longer than 5 days) temperature events that are extreme relative to the phase of the seasonal cycle and consider both heatwaves and cold-spells. We used daily-mean near-bed temperatures from the CMEMS (https://marine.copernicus.eu/) northwest European Shelf reanalysis and analysis/forecast simulations to identify heatwaves and cold-spells for the period 1993 to 2019. Monthly fisheries landings data for 1993 to 2016 from the Cefas Fisheries Activity Database for England and Wales (https://www.gov.uk/guidance/fishing-activity-and-landings-data-collection-and-processing) were analysed to identify potential impacts of the extreme temperature events on fish and shellfish.<br>Widespread heatwaves and cold-spells occurred in the southern North Sea throughout the period 1993 to 2019 but with no significant trends in the extent or magnitude of events. Winter cold-spells occurred in 1994, 1996, 1997, 2010, 2011, 2013 and 2018 and there were widespread heatwaves in 1998, 2002, 2003, 2006, 2007 and 2014 to 2019. Statistical analysis of the fisheries landings data identified a link between extreme temperature events and key fish and shellfish stocks in the North Sea. Catches of sole and sea bass increased in years with cold-spells, while catches of red mullet and edible crabs decreased. For heatwaves, the impact on fisheries catch data lagged the temperature events by five years: sole, European lobster and sea bass catches increased whilst red mullet catches reduced. </p>