Seasonal Transition Research Articles

Seasonal Migration Zone of Skipjack Tuna (Katsuwonus pelamis) in the South Java Sea Using Multisensor Satellite Remote Sensing

Skipjack tuna (Katsuwonus pelamis) is the most dominating tuna species caught in the Indian Ocean. However, tuna fishermen in the Indian Ocean still face difficulties determining potential skipjack tuna fishing grounds due to limited geographic information. An attempt to improve information regarding potential skipjack tuna fishing grounds is through modeling the SST, SSC, SSH, and SSS oceanographic parameters with skipjack tuna distribution using GIS. The characteristics of the skipjack tuna habitat can be found through the generalized additive model (GAM) statistical analysis using data of skipjack tuna catch and oceanographic parameters from satellite imagery. The integrated GIS and GAM methods can improve the study of the habitat of skipjack tuna species. Therefore, this research is aimed at analyzing the condition and SST, SSC, SSH, and SSS variations in 2016-2021 in the South Java Sea; at predicting the correlation of SST, SSC, SSH, and SSS towards skipjack tuna catch in 2016-2021 in the South Java Sea using GAM; and at creating a map of skipjack tuna seasonal migration zones. The data included skipjack tuna catches, number of trips, and skipjack tuna fishing coordinates in 2016-2021 from PPS Cilacap and PPP Pondokdadap. The oceanographic parameter data in 2016-2021 was derived from Aqua MODIS level 3 (SST and SSC) and CMEMS (SSH and SSS) satellite imagery. The results showed that the average values of oceanographic parameters at skipjack tuna fishing ground coordinates in the South Java Sea (2016-2021) were SST (26.050-30.816°C), SSC (0.094-0.564 mg/m3), SSH (0.268-0.639 m), and SSS (33.075-34.514 psu). The best GAM modeling was the combination of four oceanographic parameter variables with an AIC value of 45357.92. Skipjack tuna in the South Java Sea migrates southeast during the west monsoon season to the first transitional season and tends to migrate northwest during the east monsoon season to the second transitional season.

Monitoring Energy Balance, Turbulent Flux Partitioning, Evapotranspiration and Biophysical Parameters of Nopalea cochenillifera (Cactaceae) in the Brazilian Semi-Arid Environment.

The in-situ quantification of turbulent flux and evapotranspiration (ET) is necessary to monitor crop performance in stressful environments. Although cacti can withstand stressful conditions, plant responses and plant-environment interactions remain unclear. Hence, the objective of our study was to investigate the interannual and seasonal behaviour of components of the surface energy balance, environmental conditions, morphophysiological parameters, biomass yield and water relations in a crop of Nopalea cochenillifera in the semi-arid region of Brazil. The data were collected from a micrometeorological tower between 2015 and 2017. The results demonstrate that net radiation was significantly higher during the wet season. Latent heat flux was not significant between the wet season and dry season. During the dry-wet transition season in particular, sensible heat flux was higher than during the other seasons. We observed a large decline in soil heat flux during the wet season. There was no difference in ET during the wet or dry seasons; however, there was a 40% reduction during the dry-wet transition. The wet seasons and wet-dry transition showed the lowest Evaporative Stress Index. The plants showed high cladode water content and biomass during the evaluation period. In conclusion, these findings indicate high rates of growth, high biomass and a high cladode water content and explain the response of the cactus regarding energy partitioning and ET.

The Tibetan Plateau bridge: Influence of remote teleconnections from extratropical and tropical forcings on climate anomalies

Recent advances in the bridging roles played by the Tibetan Plateau (TP) are reviewed in terms of the remote influence of circulation anomalies over the North Atlantic Ocean on Asian monsoon and El Niño-Southern Oscillation (ENSO) events, and in a clear link between the tropical oceans and Asian climate anomalies. The authors firstly introduce how the winter and spring anomalies in the North Atlantic Ocean affect the seasonal transition over the South Asian monsoon region and subsequent ENSO events on the interannual timescale. A distinct negative sensible heating-baroclinic structure in May over the TP is found to provide an intermediate bridging effect in this Atlantic-Asian-Pacific connection. In summer, the North Atlantic Oscillation is significantly correlated with the variations of East China summer rainfall, and it is the TP's latent heating that plays the bridging role within. On the other hand, such a TP bridging effect also exists in the connection from the tropical oceans to extreme precipitation events over eastern China in summer, and from the midlatitude wave train to the biweekly oscillation of South China rainfall in spring.摘要本文回顾了青藏高原桥梁作用方面的最新研究进展, 涉及北大西洋气候异常对春, 夏亚洲季风和厄尔尼诺-南方涛动 (ENSO) 事件的遥相关影响, 热带海洋异常和中国东部极端气候异常之间的联系以及华南春雨的季节内变化等. 介绍了年际时间尺度上, 冬-春季北大西洋海表温度强迫如何影响南亚季风的季节性转变以及随后ENSO事件的触发. 5月份青藏高原上空显著的负感热斜压结构, 为北大西洋影响亚洲季风和ENSO提供了桥梁效应. 夏季北大西洋涛动与华东夏季降水变化显著相关, 高原潜热在这一关系中起着桥梁作用. 另一方面, 这种高原桥梁效应也存在于从热带海洋异常到东亚夏季极端降水事件的连接中, 以及从中纬度波列到华南春雨准双周振荡的联系中.

Exergy analysis of a new spray cooling system-based PV/T and heat recovery with application in sow houses

The uncertain cooling effect and additional huge primary energy consumption caused by humidity regulation are currently the main problems of traditional environmental regulation systems in sow houses. In this study, a new spray cooling system is proposed based on PV/T and heat recovery in sow houses. Meanwhile, the mathematical models are established for its key equipment and their reliability is verified according to literature data. The results show that the maximum error is less than 14.5 % for the models. Based on the above models, the annual operation modes are determined for the new system. Specifically, its annual operation modes mainly include the cooling season, the heating season, the transitional spring and the transitional autumn. Meanwhile, the exergy loss and energy consumption are analyzed for the new system in four seasons through simulation. The results show that in the cooling and heating seasons, the exergy loss first decreases and then increases with the increase of spray power (SP) and mass flow rate of circulating water (MFRW). In the transition season, the exergy loss decreases with the increase of MFRW, while it first decreases and then increases with the increase of SP. However, the annual energy consumption increases with the increase of SP and MFRW. Aim at the minimum exergy loss of new system, its optimal control parameters are obtained in four seasons through optimization. Specifically, when the mass flow rate of supply air is the minimum ventilation rate required by sows, the optimal SP and MFRW are recommended as 40 kW and 12245 kg/h in the cooling and heating seasons, respectively. Meanwhile, they are recommended as 35 kW and 12245 kg/h in the transition season, respectively. The above research can provide guidance for the improvement of traditional spray cooling systems and the performance optimization of new system.

Multi‐model assessment of sub‐seasonal predictive skill for year‐round Atlantic–European weather regimes

AbstractThe prediction skill of sub‐seasonal forecast models is evaluated for seven year‐round weather regimes in the Atlantic–European region. Reforecasts based on models from three prediction centers are considered and verified against weather regimes obtained from ERA‐Interim reanalysis. Results show that predicting weather regimes as a proxy for the large‐scale circulation outperforms the prediction of raw geopotential height. Greenland blocking tends to have the longest year‐round skill horizon for all three models, especially in winter. On the other hand, the skill is lowest for the European blocking regime for all three models, followed by the Scandinavian blocking regime. Furthermore, all models struggle to forecast flow situations that cannot be assigned to a weather regime (so‐called no regime), in comparison with weather regimes. Related to this, variability in the occurrence of no regime, which is most frequent in the transition seasons, partly explains the predictability gap between transition seasons and winter and summer. We also show that models have difficulties in discriminating between related regimes. This can lead to misassignments in the predicted regime during flow situations in which related regimes manifest. Finally, we document the changes in skill between model versions, showing important improvements for the ECMWF and NCEP models. This study is the first multi‐model assessment of year‐round weather regimes in the Atlantic–European domain. It advances our understanding of the predictive skill for weather regimes, reveals strengths and weaknesses of each model, and thus increases our confidence in the forecasts and their usefulness for decision‐making.

A multi-timescale optimal operation strategy for an integrated energy system considering integrated demand response and equipment response time

The response potential of demand-side resources is becoming increasingly significant in integrated energy system (IES) operations. In addition, to ensure the effective participation of system devices, their actual responsiveness at different timescales should be considered. Based on these considerations, this paper proposes an IES multi-timescale operation optimization strategy that incorporates multiple forms of integrated demand response (IDR) and considers the response characteristics of the equipment. First, the multi-timescale characteristics of IDR are analyzed. Moreover, a multi-timescale operation model of IES that comprises day-ahead, intraday, and real-time stages is further established. In the day-ahead dispatch, a low-carbon economic scheduling model is developed by considering the shifting demand response (DR) and the cost of carbon emissions. In the intraday scheduling, noting that cooling and heat energy transmission possess slow dynamic characteristics, a rolling optimization model for cooling/heating coupled equipment considering load shedding and substituting DR is established. In real-time scheduling, the output of electric/gas coupled equipment is adjusted. Finally, an industrial park-type IES in northern China was selected as an example for a case study. The results show that (1) the IDR multi-timescale response strategy can exploit different types of demand-side flexibility resources. After implementing the shifting DR, the peak-to-valley difference of the electric load curve was reduced by 20%, and the total system cost was reduced by 2.3%. After implementing load shedding, the maximum load differences per unit period of the electric, heat, and cooling load curves decreased by 18.7%, 40.0%, and 68.9%, respectively. (2) By refining the timescale of IES optimization, the proposed model can effectively ensure the energy supply and demand balance of the system under different load scenarios and reduce the system operation cost. After applying the model to simulation in three typical days (transition season, summer, and winter), the penalty costs of lost loads reduce by ¥3650, ¥3807, and ¥3599, respectively, and the total system costs decrease by 17.4%, 16.1%, and 16.2%, respectively.

Spatial and Temporal Variability of the Thermohaline Structure of Waters in the Antarctic Sound

The sea straits of the Antarctic Peninsula region are characterized by intense currents, the presence of sea ice and large icebergs, strong tides, and many other factors that form the thermohaline structure of the waters in this region and its temporal variability. The existence of local ecological communities depends on the thermohaline properties of the waters in the straits that determines the relevance of this work. From this point of view, the Antarctic Sound, which connects the Bransfield Strait with the western part of the Weddell Sea, stands out in particular. Based on new field data, a description of the thermohaline structure of this strait is given. Unique data from autonomous sensors installed on marine mammals were used for the first time and made it possible to track changes in the waters throughout the year. The transitional seasons, as well as the general boundaries of the thermohaline characteristics of the waters in the strait, have been determined. The spatial, seasonal and interannual variability of the thermohaline structure of the waters in the strait was studied on the basis of data over the last 40 years.

Attribution analysis of water use efficiency in tropical rubber plantations during drought-monsoon season transition

Understanding the water use efficiency (WUE) of rubber plantations to seasonal fluctuations is critical for understanding the water, energy, and carbon cycle in tropical regions. In this study, we examine the exchange of water and heat fluxes between land and atmosphere in rubber plantation ecosystems during monsoon and drought seasons, employing data collected from eddy covariance towers. Further attribution analysis demonstrates that drought-induced alterations in the water use efficiency are predominantly governed by changes in surface resistance (positive contribution). The contributions of incoming shortwave radiation are virtually counteracted by air temperature and longwave radiation. It is noteworthy that the light use efficiency presents the most conspicuous negative contribution; however, this effect is predominantly counterbalanced by vapor pressure deficit (VPD) and aerodynamic resistance. The elevated water use efficiency (WUE) observed in rubber plantation ecosystems during the drought season raises concerns regarding the potential implications of anthropogenic forests on food and water security in tropical regions.

Impact of Seasonal Snow‐Cover Change on the Observed and Simulated State of the Atmospheric Boundary Layer in a High‐Altitude Mountain Valley

AbstractThe structure and evolution of the atmospheric boundary layer (ABL) under clear‐sky fair weather conditions over mountainous terrain is dominated by the diurnal cycle of the surface energy balance and thus strongly depends on surface snow cover. We use data from three passive ground‐based infrared spectrometers deployed in the East River Valley in Colorado's Rocky Mountains to investigate the response of the thermal ABL structure to changes in surface energy balance during the seasonal transition from low to high snow cover. Temperature profiles were retrieved from the infrared radiances using the optimal estimation physical retrieval Tropospheric Remotely Observed Profiling via Optimal Estimation. A nocturnal surface inversion formed in the valley during clear‐sky days, which was subsequently mixed out during daytime with the development of a convective boundary layer when snow cover was low. Over high snow cover, a very shallow convective boundary layer formed, above which the inversion persisted through the daytime hours. We compare these observations to NOAA's operational High‐Resolution‐Rapid‐Refresh model and find large warm biases on clear‐sky days resulting from the model's inability to form strong nocturnal inversions and to maintain the stable stratification in the valley during daytime when there was snow on the ground. We suggest several factors contributing to the large model errors. These are (a) the inability of the model to represent well‐developed thermally driven flows likely due to the too coarse horizontal grid spacing (3 km), (b) too much convective mixing during daytime, and (c) too strong vertical coupling between the valley atmosphere and the free troposphere.

Production volume of mackarel tuna (Euthynnus affinis) as a one of fisheries commodity in Singkawang City

The purpose of this study was to observe the production volume and production value of mackerel tuna (Euthynnus affinis) during 2018 – 2020 in Singkawang City. Mackerel tuna (Euthynnus affinis) is one of the main fisheries commodities in Singkawang City that is included in the pelagic fish species in the Scombridae family. The capture of this fish species occurs throughout the year which is marked by the volume of production that is always there every month. The production volume of mackerel tuna (Euthynnus affinis) fluctuates every year, both monthly and annually. Where, the value depends on seasonal conditions and is dominantly high during the western and transitional seasons, which is as much as 12% and 13%. Meanwhile, during the western season, mackerel tuna (Euthynnus affinis) production volume is always low with a dominance of 3%. The values range from 2,836 kg – 38,963 kg which is found in August and November. The production value of mackerel tuna (Euthynnus affinis) also follows the pattern of production volume. The production value will be high if the production volume is high. The production value ranges from IDR 66,936,000 – IDR 839,534,000.

Performance and optimization of a new spray cooling system with PV/T and heat recovery in sow houses: A case study in Nanchang, China

The uncertain cooling effect and additional huge primary energy consumption (EC) caused by humidity regulation are currently the main problems of traditional air-conditioning systems in sow houses. In this paper, a new spray cooling system (NSCS) is developed based on PV/T and heat recovery in sow houses. Compared with traditional spray cooling systems, the cooling efficiency of new system can be significantly improved due to solar dehumidification and its EC can be reduced due to PV/T and heat recovery. Meanwhile, the mathematical models are established for its key equipment and their reliability is verified according to literature data. The results show that the maximum error is less than 7.2 % for the models. Aiming at the maximum utilization rate of cooling and heating equipment, the annual operation modes are determined for NSCS based on the above models. The results show that cooling season is from May 21st to September 25th, heating season is from January 1st to March 16th and from November 1st to December 31st, and the transitional spring and autumn are from March 17th to May 20th and from September 26th to October 31st, respectively. Meanwhile, the optimal spray cooling power (SCP) and mass flow rate of circulating water (MFCW) are obtained by analyzing the operation characteristics of NSCS in cooling and heating seasons. The results show that in cooling and heating seasons, it is suggested to use the minimum ventilation required by sows (42763.5 kg/h) for the ventilation rate of NSCS. Meanwhile, the optimal SCP and MFCW are recommended as 40 kW and 12245 kg/h, respectively. Finally, the matching between exergy efficiency (EE) and EC is analyzed for NSCS in transition season through simulation. The operational control methods are further proposed for NSCS in transition season through optimization. The results show that in transition season, increasing mass flow rate of supply air (MFSA) and reducing equipment power are the operational control methods to obtain the optimal performance and minimum EC of NSCS. Specifically, in the transitional spring, the optimal MFSA, SCP and MFCW are recommended as 47812.0 kg/h, 30 kW and 10245 kg/h, respectively. In the transitional autumn, they are recommended as 55806.3 kg/h, 25 kW and 7245 kg/h, respectively. The above conclusions can provide new ideas for the development of new energy-saving air-conditioning systems in sow houses, and guide the operation control and performance optimization of NSCS.

City Wind Impact on Air Pollution Control for Urban Planning with Different Time-Scale Considerations: A Case Study in Chengdu, China

Economic development and fast growing urbanization in China have caused severe air pollution, with frequent pollution episodes endangering the health of inhabitants and disturbing social activities, and as an expanding metropolis, Chengdu has suffered ever since. The concentration variations of main air pollutants, such as PM10, PM2.5 and NO2, often show periodicity because of meteorological impact and anthropic activities, and display orientation discrepancies due to influences of wind speed (WS), frequency and pollutant sources. These features have complicated the mechanisms of pollution episodes and deepened the difficulty in pollution control evaluation. The WS has significant influences on the periodicity and orientation variations in pollutant concentrations, and quantifying the influence of which is of high significance and provides sustainable foundations for pollution alleviation strategies. Different time-scale cycles (i.e., Diurnal, weekly, seasonal and annual), along with the WS, wind frequency, wind and spatial orientations in urban areas, were analyzed in this paper. Results show that the periodicity of diurnal, seasonal and annual cycles is remarkable, and weekly cycle is obvious by adding the influence of the WS in 16 orientations. The WS has direct impacts on pollutants varying in the range of 1.5–2.5 m/s, and has a remarkable diffusion effect on pollutants once above 2.5 m/s. Over heavy pollution hours in diurnal, weekly, annual cycles and transitional seasons, the WS had more significant influences on pollutants, and whereas the wind frequency is not the main impact factor for orientation variations. For Chengdu, the northeast orientation is suitable to construct a wind panel with a remarkable diffusion effect on pollutants, while air pollutions in the northwest and southwest orientations were severe with the WS below 1.5 m/s, and pollution diffusion in the north-northwest orientation was the worst. This work can provide guidance and reference for urban planning optimization and air environment protection in cities with air quality control considerations impacted by city wind.

Estimation Of Pelagic Fishing Area in Banten’s Southern Sea

The purpose of this research are to determine the average distribution of SST, chlorophyll-a, and see surface currents, and analyze the relationship between them with pelagic fish catches as an analysis material for determining pelagic fishing area in Banten’s Southern Sea. Data collected includes SST and chlorophyll-a using Aqua MODIS images data and and see surface currents data from Copernicus Marine Data for 6 years. The data was processed to produce the value of each parameter and then analyzed the parameters with the catches and determine the potential pelagic fishing area. The results showed that the SST throughout 2016 had a relatively high value allegedly due to the negative Indian Ocean Dipole (IOD). During the eastern until the end of second transitional season in 2019 there was a positive IOD which caused SST to decrease and chlorophyll-a to be larger than in other fishing seasons. See surface currents in the western season tend to be larger than in other fishing seasons. SST and chlorophyll-a have a stronger relationship with catches than see surface currents. The potential fishing area are around Tanjung Mantiyung, Muara Binuangeun, dan Tanjung Panto.

Changes in atmospheric moisture transport over tropical South America: an analysis under a climate change scenario

Warming induced by increased greenhouse gas emissions is intensifying the global water cycle and increasing the water vapor content of the global atmosphere. However, there is a lack of scientific literature assessing how regional atmospheric moisture transport and recycling will change in a warming climate. This work analyzes the projections of atmospheric moisture transport and recycling over tropical South America by the end of the twenty-first century (2070–2100) under a climate change scenario (RCP8.5). We used the Dynamic Recycling Model to estimate atmospheric moisture contributions to the region considering input data from the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis and 11 models included in the Fifth Phase of the Coupled Model Intercomparison Project. Projected increases of precipitable water in tropical South America are linked with increased evaporation from the oceans. However, those projections also indicate (1) reductions in the precipitation contributed by the main atmospheric moisture sources to the continental regions of tropical South America, (2) reductions of total precipitation, and (3) reductions of recycled precipitation over the region. The largest reductions of precipitation recycling are projected over the southern Amazon during the dry-to-wet transition season (about 31%) and the northern Amazon during its dry season (about 25%). This is particularly relevant since the southern Amazon has experienced the occurrence of longer dry seasons during the recent decades and has been highlighted as a hotspot of climate change.

The performance investigation on a multifunctional wall with photo-thermal catalytic blinds for heating, shading and formaldehyde removal

A novel multifunctional wall with photo-thermal catalytic blinds (PTC-Blind/TW) for heating, shading and formaldehyde removal was proposed. The system can realize indoor air purification all year by using solar energy, space heating in winter and cooling in summer simultaneously. The hybrid wall system was built and thermal and formaldehyde degradation performance was tested experimentally. The coupled heat, mass and reaction dynamic model was established and experimentally verified. Based on the model, the optimal blind angle control strategy was studied when the system runs in different cities all year. Main results were: (1) Under the solar radiation of 300–900 W/m2, the thermal efficiency, formaldehyde single-through convention and CADR of system were in the range of 20–40%, 30–60% and 20–80 m3/h respectively. (2) For the thermal and purification performance of the system, the fitted degree R2 between the simulation results and the experimental results reaches 80–90%. (3) The optimal blind turning angle operation strategy in Nanjing, Beijing, Xining and Guangzhou was obtained. (4) When applied optimal operation strategy in four cities, the total generated clean air annually, reduced heating loads in winter seasons and reduced cooling loads in summer and transition seasons were in range of 0.8–1.7*104 m3/m2, 86.3–739.5 MJ/m2 and 261.2–388.5 MJ/m2 respectively.

Kedalaman Klorofil Maksimum Selama Musim Peralihan II dan Implikasinya untuk Perikanan Tuna di Laut Banda

The Deep chlorophyll maximum (DCM) in the Banda Sea during the second transitional season (October 2015) was relatively shallow (25 - 64 m) above the mixed layer and far from the base of the euphotic layer or compensation depth. Its presence was identical to the depth of nitraclin injected into the mixed layer as a result of upwelling generated by internal waves. The contribution of these waves to the increase in Banda Sea fertility calculated using ocean color data is 56.87%. This phenomenon is due to the shallow optical depth of the satellite (20-25 m) while high chlorophyll-a concentrations are below. DCM was also associated with the swimming layer of Madidihang (Thunnus albacares) (34 - 68 m) caught with longline gear during the same period.

Karakteristik Fisik Perairan Selatan Kabupaten Kepulauan Tanimbar pada Musim Transisi II

This study investigated the characteristics of stratification and vertical stability of southern waters of Tanimbar Islands Regency. CTD Data from World Ocean Database 2018 especially November 1995 to represent second transitional season were utilized in this study. The CTD data were processed using Ocean Data View. This study showed that vertically the temperature of the surface layer ranged between 29 to 30 oC and the thickness of surface mixed layer was found to be 44 m. The thermocline layer has temperature ranging between 12 to 28 oC and a maximum depth of 306 m. Below thermocline layer temperature reduced to reach less than 7 oC (depth > 500 m). On the halocline layer, a high saline water was found between 66 - 94 m depth and was located on the southern part between Barbar Islands and Tanimbar Islands. Water mass was found to be unstable in the mixing layer.

Land use scenarios, seasonality, and stream identity determine the water physicochemistry of tropical cloud forest streams.

Land use is a major factor determining stream water physicochemistry. However, most streams move from one land use type to another as they drain their watersheds. Here, we studied three land use scenarios in a tropical cloud forest zone in Mexico. We addressed three main goals, to: (1) assess how land use scenarios generate different patterns in stream physicochemical characteristics; (2) explore how seasonality (i.e., dry, dry-to-wet transition, and wet seasons) might result in changes to those patterns over the year; and (3) explore whether physicochemical patterns in different scenarios resulted in effects on biotic components (e.g., algal biomass). We studied Tropical Mountain Cloud Forest streams in La Antigua watershed, Mexico. Streams drained different three scenarios, streams with (1) an upstream section draining forest followed by a pasture section (F-P), (2) an upstream section in pasture followed by a forest section (P-F), and (3) an upstream forest section followed by coffee plantation (F-C). Physicochemistry was determined at the upstream and downstream sections, and at the boundary between land uses. Measurements were seasonal, including temperature, dissolved oxygen, conductivity, and pH. Water was analyzed for suspended solids, alkalinity, silica, chloride, sulfate, magnesium, sodium, and potassium. Nutrients included ammonium, nitrate, and phosphorus. We measured benthic and suspended organic matter and chlorophyll. Streams presented strong seasonality, with the highest discharge and suspended solids during the wet season. Scenarios and streams within each scenario had distinct physicochemical signatures. All three streams within each scenario clustered together in ordination space and remained close to each other during all seasons. There were significant scenario-season interactions on conductivity (F = 9.5, P < 0.001), discharge (F = 56.7, P < 0.001), pH (F = 4.5, P = 0.011), Cl- (F = 12.2, P < 0.001), SO42- (F = 8.8, P < 0.001) and NH4+ (F = 5.4, P = 0.005). Patterns within individual scenarios were associated with stream identity instead of land use. Both P-F and F-C scenarios had significantly different physicochemical patterns from those in F-P in all seasons (Procrustes analysis, m12 = 0.05-0.25; R = 0.86-0.97; P < 0.05). Chlorophyll was significantly different among scenarios and seasons (F = 5.36, P = 0.015, F = 3.81, P = 0.42, respectively). Concentrations were related to physicochemical variables more strongly during the transition season. Overall, land use scenarios resulted in distinctive water physicochemical signatures highlighting the complex effects that anthropogenic activities have on tropical cloud forest streams. Studies assessing the effect of land use on tropical streams will benefit from assessing scenarios, rather than focusing on individual land use types. We also found evidence of the importance that forest fragments play in maintaining or restoring stream water physicochemistry.

Atmospheric controls on the Terra Nova Bay polynya occurrence in Antarctica

Polynyas, or ice-free regions within the sea ice pack, are a common occurrence around Antarctica. A recurrent and often large polynya is the Terra Nova Bay Polynya (TNBP), located on the western side of the Ross Sea just off Victoria Land. In this study, we investigate the atmospheric conditions leading to the occurrence of the TNBP and its spatial variability, as estimated using satellite-derived ice surface temperature and sea ice concentration data. A cluster analysis revealed that katabatic winds descending the Transantarctic Mountains, account for about 45% of the days when the TNBP exceeded its 2010–2017 mean extent plus one standard deviation. Warmer and more moist air intrusions from lower-latitudes from the Pacific Ocean, which are favoured in the negative phase of the Southern Annular Mode, play a role in its expansion in the remaining days. This is more frequent in the transition seasons, when such events are more likely to reach Antarctica and contribute to the occurrence and the widening of the polynya. In-situ weather data confirmed the effects of the mid-latitude air intrusions, while sea ice drifts of up to 25 km day−1 cleared the ice offshore and promoted the widening of the polynya starting from the coastal areas. Knowing the atmospheric factors involved in the occurrence of coastal polynyas around Antarctica is essential as it helps in improving their representation and predictability in climate models and hence advance the models’ capabilities in projecting Antarctic sea ice variability.

Footprints of El Niño La Niña on the evolution of particulate matter over subtropical Island Taiwan

Particulate matter (PM) pollution has become a major problem worldwide, with significant adverse health impacts, but the climatology of annual variations in and the effect of climate change on PM levels are still not comprehensively evaluated. Here we show that the vertical motions of the East Asian winter and summer monsoons regulate the annual variation in PM over Taiwan. The PM pollution season starts and ends earlier during El Niño episodes than during La Niña episodes. Furthermore, the onset, active, break, revival, and retreat phases of the PM pollution lifecycle are innovatively defined. Our results demonstrate that the annual seasonal cycle dominates wintertime PM pollution climate development during the active phase with a minor modulation by El Niño and La Niña episodes, whereas October and March, the seasonal transition periods, are significantly modulated by these two episodes. The findings suggest a new dimension of PM pollution research—the lifecycle evolution effect.