Environmental and Earth Sciences

Abstract: Observed temperature trends provide a basis for understanding climate change and planning for adaptation to its impacts. However, estimated trends can vary substantially according to the tem-poral and spatial characteristics of the observations analysed. Here, an assessment is made of the spatial and temporal variation of observed surface temperature trends across South Africa using daily observations from a fixed network of 123 stations for 1996–2025. The analysis involves mean temperature, mean daily maximum and minimum temperatures, and warm and cold extremes, i.e., annual maximum and minimum temperatures. The methods comprise trend estimations of progres-sively shorter and moving 10-year periods, and a quadratic assessment of trend curvature. The re-sults indicate widespread warming overall, but with substantial spatial heterogeneity, including localised areas where temperature trends are negative, suggesting cooling over the analysis period. For mean temperature, the median long-term trend is 0.28 °C/decade across the stations, with 55.3% showing statistically significant warming. However, for daytime maximum temperature the median trend is 0.51 °C/decade with 72.4% of stations showing statistically significant positive trends. Sub-stantial spatial and temporal sensitivity of estimated trends to the analysis period were found, with short-term trends varying markedly among periods and regions. The median of the average tem-perature trend was +0.44 °C/decade for 2011–2025 but declined to essentially zero for 2016–2025. The strongest long-term warming occurs predominantly in the northern interior of South Africa, but the spatial distribution of trend curvature differs from that of the overall warming trend. Evidence of significant positive trend curvature was found for a relatively small number of stations. The findings demonstrate that a single trend estimate can provide an incomplete representation of observed cli-mate change and that trend magnitude, temporal variability and changes in rate should be consid-ered separately. The results provide an observational basis for more robust climate-risk assessment and planning in various climate-sensitive sectors.

Abstract: Global climate change and anthropogenic forcing have intensified extreme heatwave activity across the West African Sahel. However, quantifying heatwave severity in da-ta-sparse regions like Burkina Faso—which spans distinct semi-arid and Sudanian climatic zones, remains a challenge. In this study, we adapted the daily Heat Wave Magnitude Index (HWMId) by calculating calendar-day-specific 25th and 75th percen-tile thresholds alongside a 40 °C absolute boundary using multi-satellite assimilated ERA5 2-meter maximum air temperature (T2m) reanalysis data from 2001 to 2025. The resulting heatwave magnitude time series was evaluated against the Relative Oceanic Niño Index (RONI) to investigate delayed teleconnections with the El Niño–Southern Oscillation (ENSO). The analysis identified a peak teleconnection when RONI led Burkina Faso heatwave conditions with an 8-month lag. Independent of background global warming, equatorial Pacific ENSO dynamics accounted for approximately 14% of the residual variance in regional heatwave severity. These findings demonstrate that satellite-assimilated reanalysis, combined with detrended ENSO metrics, provides an actionable 8-month seasonal forecasting window to support disaster response and public health preparedness across the Sahel.

Abstract: We constructed a two-dimensional lightning location network, FULMO (Fuji-centered Lightning Monitoring), from Boltek LRX-1 receivers around Mt. Fuji in central Japan. These receivers observe lightning electromagnetic waves mainly in the very low frequency and low frequency (VLF/LF) band, and locations are obtained by time-of-arrival. Performance was evaluated against the Japanese Lightning Detection Network (JLDN). With six operational stations, the relative detection efficiency was 52.6% for JLDN cloud-to-ground (CG) strokes and 22.6% for intracloud (IC) discharges; the median location difference for CG strokes was 1.60 km. The difference depended strongly on station geometry: 0.85 km where the largest angular gap between azimuthally adjacent stations, as seen from the discharge, was <180°, and 6.53 km where that gap was ≥180°, the smaller value corre-sponding to discharges inside the group. Five features of the LRX-1 specification limit research use: the catalog carries a systematic timing offset of −0.99898 s requiring correction before catalog matching; it provides no quality index for the azimuthal distribution of contributing stations; it records only four station identifiers per location although more can contribute, leaving that distri-bution unknown; it does not discriminate CG from IC discharges; and it gives no polarity. We rec-ommend that the manufacturer address these points.

Abstract: Low-cost optical particle sensors are widely used for ambient PM_2.5 measurements, but internal heating can raise sample temperature and reduce relative humidity (RH) before optical detection. We measured air temperature in the particle detection zone (PDZ) of the Plantower PMS5003 (PMS), both standalone and within a PurpleAir (PA) monitor. Laboratory measurements demonstrated greater PDZ warming within the PA than in the standalone PMS. A wraparound USB heater was applied to PAs to reproduce the low sample-RH conditions used by regulatory PM_2.5 monitors and nephelometers. Field experiments in Santa Rosa, California, compared standalone PMS, unheated PA, and heated PA measurements; a second experiment in Winston-Salem, North Carolina, compared heated and unheated PAs with a Teledyne T640x PM_2.5 monitor. External heating substantially reduced PDZ RH and lowered reported PM_2.5 at elevated ambient RH. Internal heating in a standard PA also reduced reported PM_2.5 relative to a standalone PMS, consistent with partial removal of hygroscopic aerosol water before optical detection. Computational fluid-dynamics and heat-transfer simulations characterized internal airflow, residence time, and temperature distributions, providing a physical framework for interpreting the measurements.

Abstract: Cut-off lows (COLs) are recurrent synoptic-scale systems over southern Africa and are frequently associated with high-impact weather, yet their propagation and persistence remain challenging to predict. This study investigates the dynamical structure and evolution of two representative COL events using reanalysis data, with emphasis on geopotential height, sea-level pressure, and three-dimensional potential vorticity (PV) diagnostics. Synoptic identification and PV-based analyses are used to characterise the vertical structure, cold-core development, jet interaction, and propagation of systems. Both events exhibit classical COL characteristics, including closed mid-tropospheric circulation, vertically coherent PV anomalies, and pronounced cold-core structures, but differ substantially in their propagation behaviour. The first event exhibits a deeper and more vertically stacked PV anomaly with limited interaction with the upper-level jet, resulting in quasi-stationary behaviour and prolonged persistence. In contrast, the second event exhibits a more symmetric and comparatively shallower PV structure that remains dynamically coupled to the mid- to upper-tropospheric jet, promoting enhanced downstream advection and a more progressive evolution. Vertical cross-section analyses indicate that the depth and coherence of the cold core, together with the degree of jet–PV interaction, are important factors in modulating COLs propagation and longevity. These results demonstrate the importance of a three-dimensional PV perspective for understanding COLs dynamics over southern Africa and highlight how differences in large-scale dynamical coupling can influence their propagation and predictability.

Abstract: The ionospheric quasi-biennial oscillation (QBO) is the sum of the solar QBO and the terrestrial QBO from below. In the present study, we focus on the QBO modulations of diurnal variations in mesospheric temperature and in the daily range of total electron content (ΔTEC) values at low latitudes. The diurnal tide (DW1) in mesospheric temperature is observed by the Aura Microwave Limb Sounder (Aura/MLS) from 2004 to 2021 and shows a dominant modulation at the QBO period of 28 months. This QBO modulation is transfered into the equatorial ionosphere by diurnal electric currents in the ionospheric dynamo region and the equatorial plasma fountain effect. Thus, the QBO modulation of the ΔTEC variation is partly generated by the terrestrial QBO from below. We decomposed the observed ionospheric QBO in ΔTEC from Global Navigation Satellite System (GNSS) into the terrestrial QBO part (from Aura/MLS) and the solar QBO part where the latter is derived from the QBO modulation of the solar flux at 10.7 cm (F10.7). The magnitude of the terrestrial QBO is 34% of the magnitude of the solar QBO in its effect on diurnal TEC variation. The supercomposition of terrestrial and solar QBO explains 81% of the ionospheric QBO signal in ΔTEC. The correlation between the QBO modulation in ΔTEC and solar flux F10.7 is 0.97. The maximal cross-correlation between the mesospheric QBO modulation in DW1 and the stratospheric QBO modulation in zonal wind is 0.97 with a certain phase lag.

Abstract: Current theories attribute a decisive role in the formation of extreme events to the meanders formed by jet streams when they slow down. These meanders are thought to foster the de-velopment of persistent atmospheric blocking patterns, impeding the westerly flow that carries mild oceanic air while channeling extremely cold, dense Arctic air toward mid-latitudes. It is as if, once released from the "barrier" holding it back, polar air rapidly flows southward via advection. Here, we propose complementing this intuitive, simplify-ing, and holistic approach. The method relies on both the resonant forcing of tropospheric multifrequency Rossby waves into harmonic modes and a joint analysis of the time lag between geostrophic wind velocity anomalies at the tropopause and geopotential height anomalies at the mid-tropopause. This analysis utilizes cross-wavelet coherence and phase—relative to a common reference—for geostrophic wind velocity and geopotential height within the 8.6–17.1-day and 17.1–34.2-day period bands that govern blocking pro-cesses. By establishing causal links, the study demonstrates the importance of geostrophic wind velocity anomalies—associated with polar vortices and polar jet streams—in the formation of mid-latitude geopotential height anomalies. The findings reveal that the his-toric cold wave striking North America in January and February 2026—resulting from a split in the stratospheric polar vortex—was driven by a vast annular high-pressure system acting as an anticyclone. Similarly, the successive heatwaves experienced by Europe dur-ing the summer of 2026 resulted from coupled eddy systems arising from the interaction between geostrophic winds associated, on the one hand, with a southward-shifted lobe of the tropospheric polar vortex and, on the other, with the displaced polar jet stream.

Abstract: This study uses data from the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) over 1981-2024 to examine the temporal and spatial coherence of precipitation regimes in West Africa. Using unsupervised clustering approaches, we distinguished four different precipitation regimes; Wettest, Transitional, Dry, and Very Dry. We compared these regimes to the Köppen climate classification zones to determine how well they corresponded. The study found a moderate correlation (Cramér’s V = 0.224) and a substantial correlation (Chi-square = 86.07, p < 0.0001) between the Köppen classifications and precipitation regimes derived from CHIRPS. Precipitation varies across the Köppen climate classification zones, such as the Tropical Rainforest (Af) and Hot Semi-Arid (BSh), in which drying and recovery were identified using standardised residuals and difference analyses. Conversely, certain zones, such as the Mediterranean, showed surprising classifications that called for further research. Analysis of temporal trends revealed regional variations in precipitation. Significantly, the Tropical Savanna (Aw) and Hot Semi-Arid (BSh) zones showed modest negative trends, indicating possible localised drying. In contrast, the Tropical Monsoon (Am) and Humid Subtropical (Cfa) zones showed positive trends, suggesting a progressive increase in precipitation. These results highlight the value of CHIRPS data in identifying subtle precipitation trends and their correspondence with accepted climatic categories, providing vital information for regional climate assessments and resource management plans.

Abstract: The stratospheric spring transition is the seasonal breakdown of the wintertime polar vortex and the progressive weakening of the westerly jet. It is a key dynamical event influencing stratosphere–troposphere coupling and medium-range weather predictability. Despite its importance, observational characterization of this transition is generally limited over the central Mediterranean area, a region of complex orography. In this study, we present an analysis of stratospheric wind structure derived from a series of radiosonde profiles at Decimomannu station (Sardinia, Italy) during May 2025. Soundings at 00 and 12 UTC provide vertical profiles of temperature, wind speed and direction, and relative humidity extending to the lower stratosphere. This dataset provides an observational perspective on the spring transition over the western Mediterranean, where orographic forcing from the Sardinian highlands and mesoscale marine circulation may locally modulate stratospheric wave activity. The main aim is the characterization of the mean zonal and meridional wind profiles in the stratosphere (15–20 km) and analysis of the temporal evolution of the zero-wind line, i.e., the altitude at which the zonal wind reverses sign, as a direct proxy for the progress of the spring transition. Finally, inertia-gravity wave activity was investigated by isolating wind perturbations from a slowly varying background estimated via a vertical running mean. Hodograph analysis of the residual profiles allows estimation of kinetic energy density and the orientation of dominant wave packets in the lower stratosphere. Results are expected to contribute to the observational characterization of this transitional regime and to serve as a reference for the validation of high-resolution NWP ICON simulations at the regional scale.

Abstract: Under global warming, compound extreme events threaten ecosystems and socio-economic systems more than individual extremes. As a typical arid and semi-arid region, Northwest China has witnessed continuous increases in concurrent summer hot and drought conditions, threatening regional water security, agriculture and ecological stability. Based on observation and reanalysis data since 1961, this paper reviews recent progress on the definition, spatiotemporal variation and formation mechanisms of Summer Compound Hot-Drought Extreme Events (CHDEE) in Northwest China. Results show that the fusion scheme of daily drought and heatwave indicators, as well as the Copula joint probability framework, perform well in regional CHDEE detection. CHDEE frequency has increased significantly, with a pronounced acceleration since the late 1990s. Spatially, CHDEE show a pattern of high values in the west and low values in the east. Affected areas expand from the arid core to the northern margins and southern high-altitude regions. CHDEE are controlled by multi-scale factors: the westerly circulation, the East Asian summer monsoon and the thermal forcing of the Tibetan Plateau. The positive soil moisture–temperature feedback is the key amplification mechanism. Current studies still lack unified definitions, and the mechanisms over complex terrain remain unclear. Future work should strengthen multi-source data fusion and develop physics-informed AI prediction methods.

Abstract: We present a novel simple parametric tomographic technique allowing to derive the cloud extinction coefficient fields from the measured cloud dimensions and optical thickness (COT). The currently available cloud tomographic algorithms are based on either least-square fit over multi-dimensional space of cloud spatial configurations or on a simpler technique using Radon transform. Both approaches are computatially extensive and require radiometric measurements made with high angular resolution. This raises questions about their applicability to satellite data analysis. In this study we propose a simpler and much more robust parametric alternative to these algorithms that is based on the internal structures found in LES-generated clouds. This approach is analytical, thus, computationally fast, and has a potential of application to airborne and satellite observations in real time.

Abstract: Vegetation and snow cover over the Tibetan Plateau (TP) strongly regulate land–atmosphere energy and water exchanges and alter the thermal forcing of the TP and thereby influence regional climate. Against the background of climate change, pronounced vegetation greening has been observed and is projected to continue in the future. However, the potential impacts of increased non-growing-season vegetation, particularly exposed withered grass stems, on winter snow cover and regional climate remain poorly understood. Using numerical experiments conducted with the Community Earth System Model version 2.2 (CESM2.2), we investigate the effects of increased withered grass stems (WGS) over the TP on winter snow cover fraction, the surface energy budget, atmospheric circulation, precipitation, and near-surface air temperature. The results show that increased WGS reduces the winter-mean snow cover fraction by approximately 11.1%, with the largest decrease occurring in December (16.7%), primarily over the central and eastern TP. Greater exposure of WGS above the snow-pack lowers surface albedo and increases net shortwave radiation, thereby enhancing surface diabatic heating. The enhanced thermal forcing induces warming in the low-er-to-middle troposphere over the TP and its southern flank, but cooling to the north. Correspondingly, at 500 hPa, anticyclonic circulation anomalies develop to the south of the TP, while cyclonic anomalies occur to the north. These circulation changes further modify large-scale horizontal heat and moisture transport. Enhanced moisture convergence leads to increased winter precipitation over the Yangtze River basin, regions to its south, and the western TP, whereas enhanced moisture divergence contributes to reduced precipitation over the eastern Indochina Peninsula and adjacent regions. The cooling north of the TP is mainly associated with anomalous horizontal heat transport, whereas warming over the TP is directly related to the WGS-induced reduction in surface albedo and increase in net surface radiation. These results highlight that changes in non-growing-season vegetation can substantially modify wintertime thermal forcing over the TP through vegetation–snow–surface energy interactions and, in turn, exert considerable impacts on atmospheric circulation and regional climate over surrounding and downstream regions.

Abstract: This study investigates the thermal behavior of three Lufft CHM15k ceilometers at ACTRIS observational platforms and evaluates statistical associations between housekeeping temperatures and attenuated backscatter. The instruments are deployed at RADO-Galati and RADO-Bucharest (Romania) and AGORA Granada (Spain). External, internal, optical-module, and detector temperatures from 14 July 2023 to 14 July 2025 were analyzed using Pearson and sliding-window correlations, while time–range correlations assessed associations with the SNR-screened and smoothed attenuated backscatter coefficient. Long-term analysis showed strong external–internal thermal coupling, with clearer seasonal modulation at the Romanian sites than at AGORA–Granada. Five warm- and five cold-season days from 2024 were analyzed per platform. Across the three sites, 51 contiguous regions with strong correlations (|PCC| ≥ 0.8) and at least 50 connected hour–range cells were identified; 47 occurred during warm-season cases and four during cold-season cases. Significant associations were concentrated mainly at lower measurement ranges and extended farther during warm-season cases. These correlations do not demonstrate direct temperature-induced modification of atmospheric backscatter because common diurnal atmospheric variability may contribute. Systematic housekeeping-parameter monitoring can support quality control, preventive maintenance, and resource-efficient operation of long-term atmospheric remote-sensing networks, strengthening sustainable environmental monitoring and resilient research infrastructure relevant to the Sustainable Development Goals (SDGs).

Abstract: How far can reservoir operation displace a river's calendar? We address the question with 92 years of monthly discharge on the Naryn, the transboundary artery of the Syr Darya basin, together with 46 years of release data and two years of daily reservoir balances. Annual flow shows no trend, yet the centre of timing of flow moved from late June to mid January, a displacement of 165 days (bootstrap 95% interval 158 to 173) that inverts the hydrograph and far exceeds the week-scale timing shifts reported for climate-driven change. A phase and concentration decomposition separates this rotation from an earlier flattening; change points near 1986, 1990 and 1994, confirmed by independent segmentation methods, coincide with the documented transition from irrigation-oriented to energy-oriented operation. Roughly 4.8 km³ per year (4.0 to 5.6) now arrives outside the growing season. The evidence identifies reservoir operation as the dominant driver of the inversion and quantifies the seasonal redistribution at the centre of a thirty year allocation dispute.

Abstract: Ephemeral channels in Arequipa (Peru) convey floods and lahars during the rainy season. On 19 and 22 February 2026, tributaries of the Chullo channel on Chachani volcano’s southern flank became active, but the origin of the triggering rainfall was unknown. This study characterises both episodes from the continental to the local scale and assesses whether they shared a common moisture origin. We combined CHIRPS v3 precipitation, NCEP/NCAR R1 reanalysis, 54 backward trajectories with moisture bookkeeping, GOES-19 infrared imagery and Air Mass RGB composites. February 2026 rainfall (412.8 mm) was 145% above the 1991–2020 mean, and seven-day antecedent rainfall was larger before 22 February. Air arrived from the east on 19 February and from the southeast on 22 February, yet in both episodes most arriving moisture (63% and 96%) was gained over the preceding five days along mainly continental paths. Air Mass imagery showed a continuous tropical air mass from the tropical Atlantic to the southern Andes and dry air aloft over the adjacent Pacific. The second episode had stronger vapour transport and colder cloud tops (−74.2 vs. −55.2 °C). The Chullo activation reflected afternoon convection over wet antecedent conditions, fed by continental moisture compatible with a remote Atlantic origin.

Abstract: Ozone (O₃) pollution exhibits complex processes and characteristics across short-term, seasonal, and long-term temporal scales. Existing studies have predominantly focused on individual scales, highlighting the need for further exploration of response relationships across different scales. This study focuses on East Asia (105° to 125°E, 20° to 42.5°N), integrating daily three-dimensional field data of O₃, NO₂, HCHO, and isoprene from the ECMWF EAC4 reanalysis dataset, along with ERA5 meteorological data, covering the period from 2017 to 2025. Treating O3 and its major precursors as an integrated analytical object, a dual-layer Gaussian low-pass filter was applied to decompose standardized pollutant fields into short-term (ST), seasonal (SN), and long-term (LT) components. Joint Empirical Orthogonal Function (EOF) decomposition was then employed to extract spatial modes and principal component time series reflecting the co-evolution of ozone and precursors at each scale. PINN was incorporated to explore potential physical drivers underlying each mode, while rolling multivariate Ordinary Least Squares (OLS) regression and CNN-BiLSTM neural network were jointly applied to investigate cross-scale response intensity β and its time-varying characteristics. Results indicate that: (1) modal coupling relationships across temporal scales are continuously evolving, with traditional single-factor dominated patterns giving way to multi-factor synergistic modes; (2) cross-scale interactions are themselves changing, and neglecting their evolution may systematically misestimate risks; (3) only the first long-term mode exhibits a marginally significant upward trend (p = 0.048), while change point detection at 2019 and 2022 closely coincides with major emission reduction policy milestones. Continued cross-scale research is essential for adaptive ozone control strategies.

Abstract: The Zero-Degree Level (ZDL) serves as a critical boundary for aircraft structural icing in the presence of supercooled droplets. Understanding its spatiotemporal evolution is crucial for evaluating mid-tropospheric thermal shifts and aviation safety. Using ERA5 reanalysis data (1990–2024) across 38 Greek airports, this study analyzes trend dynamics of mean freezing levels and lower-tail cold extremes (Q25) via Mann-Kendall and Sen’s slope methods. Overall, the 0°C isotherm exhibits a systematic upward shift within a 10,000–14,000 ft Mean envelope (with Q25 values extending down to 6,500–8,500 ft), showing statistically significant warming trends across over 80% of stations. Crucially, the Q25 threshold displays a lower rate of long-term shifting than the mean, governed by strong seasonal asymmetries. November acts as the primary warming hotspot (Q25 up to +63 ft/yr), indicating delayed early-winter cold-air outbreaks, whereas September exhibits trend stagnation. Winter shows strong intra-seasonal contrasts, transitioning from January cold-tail stationarity to widespread February warming. Spring functions as a thermal bridge toward summer’s elevated freezing levels (&gt;15,000 ft Mean). Spatially, maritime sectors benefit from sea-surface thermal buffering, whereas enclosed northern inland basins display persistent cold-air pooling. Operationally, these shifts displace the primary structural icing window (0°C to -20°C) to higher flight levels.

Abstract: Atmospheric turbulence is a major hazard for commercial flight operations. As a result, reliable and easily interpretable meteorological forecast data for this hazard is paramount to the safety of aircraft, crew and passengers. To meet this requirement, Deutscher Wetterdienst (DWD) has further improved their forecast products by blending the traditional deterministic numerical weather prediction of the Eddy-Dissipation-Parameter (EDP) with the probabilistic forecast to exceed the severe turbulence threshold of the EDP from its operational ensemble prediction system (EPS). Building on those results and inspired by an agile co-design approach with key users, a turbulence advisory was conceived which condenses three-dimensional spatial information into two dimensions in order to further support situational awareness and complement traditional aeronautical meteorological charts. In this technical note, the necessity for products of this kind is motivated and their design and specifications are briefly explained.

Abstract: Cold-pool structure controls the confinement of wintertime ozone and its precursors in Utah’s Uinta Basin. Previous studies have documented difficulty capturing stable cold pools in meteorological models, complicating air-quality simulations when pollutants disperse too readily. Herein, we evaluate the meteorology behind one such high-ozone event on 2 February 2013 withWeather Research and Forecasting (WRF) simulations; chemistry is not simulated. We test sensitivity to Global Forecast System (GFS) or North American Mesoscale (NAM) forcing, domain feedback, boundary-layer and surface-layer schemes, slope-aware radiation, and terrain datasets (fine versus coarse). Across five hourly samples, GFS-driven runs were warmer at the evaluated surface sites, had an approximately 3.6K smaller 50–500m potential-temperature endpoint difference, and a 0.8–1.0ms−1 larger layermean wind-vector magnitude than feedback-matched NAM runs. GFS also retained less mean heat deficit, indicating a weaker modelled cold pool. Heat deficit increased in all four runs from 1400 to 1800 UTC, hence the product separation suggests a state difference without demonstrated faster cold-pool erosion. Toggling feedback and parameterisation settings yielded smaller responses; terrain fineness produced spatial responses that station comparisons could miss. The results guide diagnostics for subsequent air-chemistry modelling, while leaving initial versus lateral forcing, cold-pool depth and basin export for future studies.

Abstract: The present study aimed to evaluate the climatic suitability of Actinidia arguta (mini kiwifruit) across Europe. We first calibrated a species distribution model (SDM) on occurrence records from the native East Asian range and then transferred it to the European domain. Alongside standard bioclimatic variables, we incorporated a custom spring frost indicator into the modeling workflow. The five algorithms (GLM, RF, MAXNET, GAM, GBM) showed moderate-to-good predictive performance, with mean validation TSS values ranging from 0.618 to 0.656 and mean AUC values from 0.884 to 0.912. Temperature seasonality (BIO4) was the most influential predictor, with precipitation of the warmest quarter (BIO18) and spring minimum temperature (spring_min) showing similarly high secondary importance. Spatial projections indicated broad areas of climatic suitability across Central and Southeastern Europe; however, a considerable share of these suitable areas also coincided with zones where temperatures during critical phenological stages of A. arguta regularly fall to potentially damaging levels. Taken together, these results indicate that climatic suitability alone tends to overestimate actual cultivation potential, and that the risk of late-spring frost must be treated as an explicit component of any species distribution modeling framework for perennial crops.