Temporal Trends in Agriculturally Relevant Climate Indicators across Nine Agroecosystems of Turkey

An interaction of trends in a multitude of climate indicators dictate how agricultural production and resource use will be affected. Turkish agroecosystems have not been evaluated for climate trends, especially focusing on spatial and temporal domains relevant for agricultural production. Long-term (1981–2017) temporal trends in agriculturally relevant climate indicators [maximum (T_max), minimum (T_min), and mean (T_avg) air temperatures, diurnal temperature range (DTR), growing degree-days (GDD), precipitation, incoming shortwave radiation (R_s), relative humidity (RH), wind speed (u₂), saturated and actual vapor pressure (e_s and e_a), vapor pressure deficit (VPD), grass-and alfalfa-reference evapotranspiration (ET_o and ET_r), and aridity index (AI)] across Turkey (Turkiye) were quantified and analyzed using the NASA-POWER dataset at 0.58 ☓ 0.58 grid cells (n = 323) for nine agricultural zones (AZs) in Turkey. At the growing-season scale, T_min, T_max, T_avg,GDD,e_s, e_a,VPD,R_s, precipitation, RH, and AI showed statistically significant positive trends at 100%, 76%, 100%, 100%, 94%, 98%, 22%, 83%, 33%, 10%, and 13% of Turkey’s terrestrial area, respectively. Negative trends were observed in growing-season-scale DTR, u₂,ET_o,andET_r at 38%, 38%, 10%, and 18% of the total terrestrial area, respectively. At the annual scale, ETo and ETr showed increasing trends over 37% and 19% of the area, respectively. Evaporative demand showed national mean trends of-2.6 and-4.1 mm yr^-1 during the growing season, respectively. Aegean AZ showed the most negative trends in growing-season ETo and ETr. The national mean magnitude in annual total precipitation (4.7 mm yr^-1) was 39% greater than that in growing-season total precipitation (3.4 mm yr^-1).