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This paper has investigated the impact of convective parameterization schemes (CPS) and land surface models (LSM) on the simulation of summer climate over the Democratic People’s Republic of Korea (DPR Korea) using the regional climate model (RegCM 4.7). The sensitivity experiments with two LSMs [Biosphere Atmosphere Transfer Scheme (BATS) and Community Land Model (CLM 3.5)] and four CPSs (Grell, Emanuel, Grell over land and Emanuel over ocean (GL_EO), Emanuel over land and Grell over ocean (EL_GO)) at 30 km horizontal resolution are carried out in summer (from June to August) for 10 years (2001–2010) for this purpose. The simulation results are compared with the available observation data provided from the State Hydro-Meteorological Administration of the DPR Korea (SHMAK). The results show that summer mean circulation patterns (SMCP) and summer averaged surface temperature (SAST) is well captured for most of the simulations, but summer rainfall is not well represented by RegCM 4.7. The performance of the CLM3.5 scheme is better in all the simulations than the BATS scheme. Among the CPSs, the EL_GO scheme shows the smallest biases in the simulation of SAST and summer rainfall. The simulations using EL_GO with CLM3.5 shows the best performance in simulating the SAST and summer rainfall over the study region among the considered CPSs and LSMs. These results will be helpful to improve the prediction of climate change over the DPR Korea.

The Pacific–Japan (PJ) pattern is a significant teleconnection influencing the East Asian summer climate across multiple timescales. Previous studies indicated that the tropical Pacific and Indian Ocean variability may largely contribute to the PJ variability, while the influence from the tropical Atlantic is relatively less understood. This study suggests that the tropical South Atlantic (TSA) sea surface temperature (SST) can drive the PJ pattern in boreal summer via analysis of observational and reanalysis datasets and numerical experiments. Multiple atmospheric dynamical processes and atmosphere–ocean interactions contribute to this teleconnection. The TSA warming excites a Kelvin wave pattern that propagates eastward to the tropical Indo-Western Pacific. The meridional gradient of Kelvin wave-induced easterly anomalies over the Western North Pacific (WNP) generates anticyclonic anomalies, further amplified by barotropic energy conversion, triggering a PJ-like circulation anomaly. Additionally, the easterly wind anomaly may heat the SST over the Maritime Continent through the wind-evaporation-SST effect, further enhancing the PJ pattern through diabatic heating. This finding builds a teleconnection from the tropical Atlantic to the East Asia summer climate and offers insights for additional predicational potentials for the East Asian summer monsoon. It might help to improve climate prediction and future projection in East Asia and have broad implications for agriculture, energy supply, and public health in this region.

This study investigates the coupled variability of temperature and precipitation in eastern China during summer using empirical orthogonal function (EOF) analysis to better understand and mitigate simultaneous occurrences of extreme events, such as compound droughts and heat waves. Two dominant modes are identified: the first exhibits a strong warming and drying trend in the region north of the Yangtze River, with the opposite occurring in the south; the second illustrates decadal oscillations in temperature and precipitation, alternating between cool-wet conditions and warm-dry conditions in southern China. The underlying mechanisms for these leading modes are revealed through correlation, composite analysis, and model simulations. The first mode is associated with a negative Pacific-Japan teleconnection in the lower atmosphere and a stationary Rossby wave train across Eurasia in the upper troposphere, which are influenced by global warming and sea surface temperature anomalies in the western North Atlantic. The second mode is linked to alternating active periods of the North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation (PDO). The NAO exerts a significant influence on the summer climate in eastern China during its active phases, while the PDO shows an opposite effect when the NAO is less active. These findings provide valuable implications for long-term planning and adaptation strategies to better cope with compound extreme events in eastern China.

Grass pollen is the main cause of hay fever and allergic asthma in warm temperate climates during summer. The aim of this study was to determine the content of group 5 major allergens in pollen grains of agriculturally important grass species/cultivars. For each cultivar flowering dates and pollen production of cut anthers were observed in the field and in a climate chamber, respectively. An ELISA was used to quantify the group 5 allergens (Phl p5) in pollen extracts which were gained from the grass species Kentucky bluegrass, perennial rye grass, timothy, cocksfoot, annual / Italian rye grass, hybrid rye grass and festulolium. The group 5 allergen content of species varied between 0.01 ng (Kentucky bluegrass) and 0.06 ng (timothy) per pollen grain. On cultivar level the pollen allergenic content differed up to 74-times within the selected grass species. Results from this study might be helpful for the reduction of allergen exposure coming from agriculture grass production e.g. by an adapted grass selection or by the cultivation of grasses with low allergenic content in plant breeding.

Storm clouds frequently form in the summer period in temperate climate zones. Studies on these inaccessible and short-lived atmospheric habitats have been scarce. We report here on the first comprehensive biogeochemical investigation of a storm cloud using hailstones as a natural stochastic sampling tool. A detailed molecular analysis of the dissolved organic matter in individual hailstones via ultra-high resolution mass spectrometry revealed the molecular formulae of almost 3000 different compounds. Only a small fraction of these compounds were rapidly biodegradable carbohydrates and lipids, suitable for microbial consumption during the lifetime of cloud droplets. However, as the cloud environment was characterized by a low bacterial density (Me = 1973 cells/ml) as well as high concentrations of both dissolved organic carbon (Me = 179 µM) and total dissolved nitrogen (Me = 30 µM), already trace amounts of easily degradable organic compounds suffice to support bacterial growth. The molecular fingerprints revealed a mainly soil origin of dissolved organic matter and a minor contribution of plant-surface compounds. In contrast, both the total and the cultivable bacterial community were skewed by bacterial groups (γ-Proteobacteria, Sphingobacteriales and Methylobacterium) that indicated the dominance of plant-surface bacteria. The enrichment of plant-associated bacterial groups points at a selection process of microbial genera in the course of cloud formation, which could affect the long-distance transport and spatial distribution of bacteria on Earth. Based on our results we hypothesize that plant-associated bacteria were more likely than soil bacteria (i) to survive the airborne state due to adaptations to life in the phyllosphere, which in many respects matches the demands encountered in the atmosphere and (ii) to grow on the suitable fraction of dissolved organic matter in clouds due to their ecological strategy. We conclude that storm clouds are among the most extreme habitats on Earth, where microbial life exists.

This study investigates the summer climate variability over Korea that is associated with diverse features of El Niño-Southern Oscillation (ENSO) evolution. Four different ENSO evolution features were analyzed, and the related Korean climate variability during July and August are investigated. The two evolution phases in which El Niño transitions into La Niña and El Niño develops from a neutral state show roughly similar circulation features in affecting the Korean summer climate, but with opposite signs. During the transition of El Niño into La Niña (after El Niño develops from a neutral state), the positive (negative) western North Pacific anticyclonic circulation anomaly directly affects Korea in August, producing a significant warm (cold) surface air temperature (SAT) anomaly in Korea. Notably, the SAT that occurs in July generally exhibits an opposite tendency to that of August in Korea, displaying subseasonal variations. However, the persistent phases of La Niña and El Niño exhibit distinctive features from the two transition phases mentioned. During the persistent La Niña phase, the Pacific-Japan like atmospheric circulation pattern affects Korea, showing a significant warm SAT anomaly over Korea in July, and a roughly similar situation with opposite signs is observed in the persistent El Niño phase. In these cases, the Korean SAT in August exhibits similar anomalies to July. The distinctive variability in the summer climate of Korea during the diverse ENSO evolution phases presented in this study provides a statistical basis for understanding the Korean summer climate in relation to ENSO.

A better anticipation of high-impact heat and drought on human activity is the underlying motivation of many climate studies focused on the summer season. Although a large body of research has already highlighted the prominent impact of soil moisture anomalies on summer mid-latitudes climate variability and predictability, it still leaves room for a wide range of uncertainty and sometimes contradictions. The present work aims at revisiting soil moisture sensitivity studies by comparing an idealized ensemble model experiment in which soil moisture conditions are prescribed with a reference experiment in which soil moisture evolves freely. Two regional climate models centered over Europe contribute to these experiments and generate very similar results. Simulations with constrained soil moisture display significantly increased correlation between observed and simulated seasonal anomalies of maximum temperature, precipitation and surface solar radiation, as compared to the reference experiment. This widespread increase is not restricted to regions already known as hot-spots of land–atmosphere coupling such as southern Europe, where the evapotranspiration rate is mainly driven by soil moisture. In spite of a limited change in the ensemble spread, the sensitivity experiments show a substantially modified magnitude of temperature and precipitation variability. A focus on two case studies reveal contrasting results for the 2003 and 2010 heat waves. These results stress the prominent role of soil moisture as a boundary condition of the climate system in Europe, including regions that have not been highlighted by previous sensitivity works.

Climate models exhibit biases in the mean state and in variability across different regions of the Earth. For example, atmosphere-only models have a poleward bias in summertime jet streams across the Northern Hemisphere (NH). This can result from many processes, including misrepresentation of Rossby waves that can propagate in different directions and thereby interact with jet streams. However, Rossby-wave biases can result from biased background state of the climate system as well. The propagation speed of Rossby waves depends on jet stream strength, thus a poleward displacement of the jet stream can hinder westward propagation of Rossby waves at higher latitudes and displace eastward propagating Rossby waves (downstream development). These biases then impact other regions resulting in biased atmospheric circulation across the NH. Indeed, in this study we confirm this via regional nudging experiments within the Norwegian Earth System Model. Namely, nudged horizontal winds over the North Pacific can improve Rossby wave statistics and thereby atmospheric circulation over Eurasia (i.e., upstream). However, nudging over the North Atlantic has little effect on boreal summer atmospheric circulation. This implies that improving biases over the North Pacific is crucial for a better representation of modelled boreal summer circulation over Eurasia.

In the context of global warming, how to measure summer climate suitability at a local scale is important for meteorological services. Considering meteorological and ecological conditions, body comfort, and the atmospheric environment, an assessment method for summer climate suitability for Zhejiang Province is proposed. In this paper, a summer suitable index (SSI) for Zhejiang is calculated, including four secondary indices: a summer cool index (SCI), a comfort days index (CDI), a good air days index (GADI) and a vegetation cover index (VCI). Using a local evaluation criterion, summer climate suitable areas are distinguished objectively according to the SSI. The results show that especially suitable regions account for 4.97% of Zhejiang Province, very suitable regions account for 22.2%, suitable regions account for 39.58%, and general regions account for 33.25%. The summer climate suitable areas are located mainly in high mountains and hills and coastal island areas while plain areas cannot be considered a suitable destination for summer tourism. By comparison and discussion, the SSI is demonstrated to capture summer climate suitability well. In contrast to a fixed evaluation index, benchmark values obtained for the SSI depend on the local climate and the index is straightforward to apply.

In this study, the effect of glazing-to-total-wall-area ratio on the thermal performance of different wall materials is numerically investigated in terms of heat transmission load. The investigation was performed for a South-facing wall in Elazig, Turkey. The heat transmission load through walls and windows are determined separately for summer and winter climate conditions. In this analysis, the frame area of the window is not considered. Therefore, whereas the glazing area on uninsulated and insulated walls is increased from 0% to 100%, the heat gain and losses are calculated separately according to the glazing type. The transmission loads through the wall are determined by an implicit finite difference procedure under steady periodic conditions. Concrete, briquettes, bricks, and autoclaved aerated concrete are selected as structure materials. Results show that in the uninsulated wall, the wall material affected the glazing area, whereas in the insulated wall, the effect of wall material on glazing area is insignificant.