Luzon Island Research Articles

The Tropical Diurnal Cycle under Varying States of the Monsoonal Background Wind

Abstract The impact of the environmental background wind on the diurnal cycle near tropical islands is examined in observations and an idealized model. Luzon Island in the northern Philippines is used as an observational test case. Composite diurnal cycles of CMORPH precipitation are constructed based on an index derived from the first empirical orthogonal function (EOF) of ERA5 zonal wind profiles. A strong precipitation diurnal cycle and pronounced offshore propagation in the leeward direction tends to occur on days with a weak, offshore prevailing wind. Strong background winds, particularly in the onshore direction, are associated with a suppressed diurnal cycle. Idealized high-resolution 2D Cloud Model 1 (CM1) simulations test the dependence of the diurnal cycle on environmental wind speed and direction by nudging the model base state toward composite profiles derived from the reanalysis zonal wind index. These simulations can qualitatively replicate the observed development, strength, and offshore propagation of diurnally generated convection under varying wind regimes. Under strong background winds, the land–sea contrast is reduced, which leads to a substantial reduction in the strength of the sea-breeze circulation and precipitation diurnal cycle. Weak offshore prevailing winds favor a strong diurnal cycle and offshore leeward propagation, with the direction of propagation highly sensitive to the background wind in the lower free troposphere. Offshore propagation speed appears consistent with density current theory rather than a direct coupling to a single gravity wave mode, though gravity waves may contribute to a destabilization of the offshore environment.

Summer Anticyclonic Eddies Carrying Kuroshio Waters Observed by a Large CPIES Array West of the Luzon Strait

Abstract The Kuroshio intrusion into the South China Sea (SCS) in summer is weak and has rarely been reported by in situ observations. Here, we describe a new form of Kuroshio water intrusion that is strongest during the summer, the North Luzon Warm Eddy (NLWE), which is an anticyclonic eddy originating north of Luzon Island. From early July to mid-September 2018, two NLWEs moving northwestward were captured by a mooring array consisting of 27 current- and pressure-recording inverted echo sounders (CPIESs). The three-dimensional CPIES estimates reveal that the NLWEs carried large amounts of saline Kuroshio waters (S > 34.7 psu) in the subsurface, which was also evidenced by Argo float profiles. The Kuroshio intrusion was confined to waters shallower than the 14.8°C isotherm. Historical data for NLWEs suggest that they occur mostly during the summer but are absent between November and March, which is attributed to seasonal wind stress curl (WSC). However, because the seasonal signal of WSC during summer is small, intraseasonal WSC is directly responsible for the generation of NLWEs. Significance Statement This paper describes a new type of Kuroshio water intrusion into the South China Sea (SCS)—the North Luzon Warm Eddy (NLWE), which is an anticyclonic eddy generated north of Luzon Island. The eddy mostly occurs during summer when the Kuroshio intrusion is commonly considered the weakest. From observations of a large CPIES array, we provide a cradle-to-grave picture of the NLWE. NLWEs are estimated to contribute almost half of the westward Luzon Strait transport during the summer and, as such, play an important role in the seasonal stratification and circulation in the northeastern SCS.

Luzon predators: Clues from a fossil with bite marks

Luzon Island remained isolated throughout its emergent history with its paleofauna often considered depauperate. However, the terrestrial vertebrate fossil record of the island is still poorly known. A new fossil-bearing paleochannel deposit was discovered in La Union Province, northwestern Luzon, Philippines. This paleochannel is inferred to be of Pleistocene age and has yielded fossils tentatively classified as a bovid (Bubalus sp.), a cervid (Rusa sp.), a suid (Sus sp.), and a large crocodile (Crocodylidae). Interestingly, a proximal fragment of the left tibia of a cervid shows multiple bite marks. This study analyzes the bite marks and modifications on the specimen to infer its possible trace maker and explore its implications in understanding the ancient predatory guild of Luzon. Three sets of modifications were recognized on the specimen, namely the bite marks, the broken proximal end and the dry bone fractures. A crocodilian agent for the bite marks is supported by the bisections, their occurrence in the paleofaunal assemblage and the fluvial setting of the deposit. However, an unknown carnivoran agent interpretation cannot be fully disregarded given the ambiguity of bisected marks and the possibly gnawed proximal end of the specimen. Unfortunately, given the lack of in situ context and apparent overprinting, the extent of the peri- and post-mortem modification remains uncertain which hinders the identification of the predatory agent. Verification of the observations reported in this study would require the systematic collection and detailed taphonomic analysis of additional fossil specimens from the deposit.

FIRST RECORD OF HOYA MELIFLUA (BLANCO) MERR. (APOCYNACEAE, ASCLEPIADOIDEAE) IN THE NATURAL ECOSYSTEMS OF BATANGAS IN LUZON ISLAND, PHILIPPINES, WITH NOTES ON ASSOCIATED FLORA

The Philippine islands host a significantly high concentration of native and endemic Hoya species. However, there are no previous records of this genus in the natural ecosystems within the province of Batangas, Luzon Island. The present study pioneered the exploration of Hoya plants and their associated communities in Batangas. A route-walk method was employed within the forests of Lobo, Batangas, to document Hoya species. Morphological characteristics, habitat, host plants, substrates, and associated flora were also recorded. Only one species was identified, Hoya meliflua (Blanco) Merr., with material deposited in the Batangas State University – The National Engineering University Lobo Campus Herbarium (Reg. #: Pasado 001). The morphology and other plant references and databases confirmed its identity. The study found that the individuals of H. meliflua in Lobo inhabit the secondary riverine forests along ecotourism sites, with Schizostachyum textorium (Blanco) Merr., Ficus balete Merr., Tectona philippinensis Benth. & Hook.f. ex Merr. and Pterospermum diversifolium Blume as the major host plants. The assessment of the associated flora revealed 46 species, of which 100% were natives, 13% were Philippine endemics, and 14% were threatened nationally and internationally. The conservation of H. meliflua in Batangas can be improved by mainstreaming its importance as an ornamental plant and a key biodiversity species within ecotourism sites. Further studies can help in revealing the presence of other Hoya spp. on the island.

MARINDUK ISLAND IN THE PHILIPPINES FROM THE POSITION OF GEOGRAPHY OF TOURISM

The Marinduque Island, which is a part of the Marinduque province, is a small but densely populated island within the Luzon Islands Group. The island surrounded by the water of the Sibuan Sea, the island has an area of 959 square kilometers and a population of 245 000 people. Flat plains, low coasts, low slope plains, mangrove forests and hilly lands constitute the most important natural elements of the Marinduque Island. There are many bays, beaches, atoll, cliffs, capes, coral and mangrove forests on the coast of the island. In this study, the geographical location of the Marinduque Island and its general geographical features have been explicated, and the main tourism elements of the island have been briefly discussed. We have tried to examine the main physical and human characteristics of the island by identifying its tourism potential. Furthermore, the main accommodation facilities, beaches and hotels located on the east and west coasts of the island have been identified. The main purpose of this study is to introduce the tourism potential and natural beauties of this Philippine island, which is not well-known among the foreign tourists and to offer new holiday options for the inquisitive tourists.

Caloglossa fluviatilis Krayesky, Fredericq & J.N.Norris (Delesseriaceae, Rhodophyta) from Bataan province, Luzon Island, Philippines, a new country record

Caloglossa fluviatilis is one of the least known freshwater algal species of its genus, having been reported from its type locality in Pedro Miguel, Republic of Panama, and Chalakkudy and Periyar Rivers in the State of Kerala, India. This study presents a new locality record of the species from Bataan province on the island of Luzon, Philippines. C. fluviatilis is characterised by having (1) a thallus having a width at the internode region narrower than 1.0 mm, (2) moderate development of adventitious secondary branches at the node, and (3) fewer than eight rhizoidal filaments arising from pericentral cells at the node. Indeed, this Philippine population of C. fluviatilis has helped fill the gaps and extended the distribution of the species to the western Pacific region. Further studies and reassessment of freshwater Caloglossa specimens will contribute to further understanding of these little-known genus members.

The contribution of non‐tropical cyclone vortices to the rainfall of the Philippines

AbstractWeaker disturbances than tropical cyclones (TCs) such as tropical depressions and cold surges can significantly induce heavy rainfall and flooding events over the Philippines. However, the analysis of these disturbances including their rainfall contributions are often neglected in previous studies. As the first attempt to address this research gap, this study investigates the rainfall contribution of non‐TC vortices over the Philippines from 1979 to 2020. Only those rainfall‐producing non‐TC vortices that formed and appeared within a 500‐km radius from the Philippine coastline were examined in this study. A total of 7,686 non‐TC vortex days (50% of the total days during the analysis period) were identified. The mean rainfall contribution of these non‐TC vortices was found to be highest over the northeastern Mindanao Island (80–90% of the mean daily rainfall) and lowest over the central and western regions of Luzon Island (50–60%). Seasonal analysis of the occurrence frequency of these vortices shows that they are most frequent during the December–February (DJF) season. In this season, the rainfall contribution may increase to 50–80% of the mean daily rainfall over the whole country, while in the other seasons, the rainfall contribution may only increase to as much as 60%. Higher frequency of extreme rainfall days associated with these non‐TC vortices were also found during the DJF season. The frequency of occurrence and percentage rainfall contribution of these non‐TC vortices in relation to the different phases of the Boreal Summer Intraseasonal Oscillation (BSISO) during boreal summer (June–October) and the Madden–Julian Oscillation (MJO) during boreal winter (December–April) were also examined. Higher frequency and percentage rainfall contribution over the country were found during Phases 4–6 of both the BSISO and MJO, during which their respective active convections transition from the Maritime Continent to the western North Pacific.

Along-Strike Variation of Seismicity Near the Extinct Mid-Ocean Ridge Subducted Beneath the Manila Trench

AbstractThe change in seismic activity is explored using data recorded by ocean-bottom seismometers (OBSs) and permanent seismic stations near the extinct Mid-Ocean ridge of the South China Sea (SCS) and the Manila trench. We apply the machine learning–based algorithm EQTransformer to the OBS dataset for seismic event detection and phase picking and then evaluate the precision and compare the time residuals between automatic and manual picks. We derive a catalog of earthquakes in the region and find bending-fault earthquakes in the outer rise at the northern of the Huangyan (Scarborough) Seamount chain, where no historical seismicity was reported in the routine catalog. Abundant outer-rise earthquakes occurred on both sides of the Huangyan (Scarborough) Seamounts chain, but the focal depths vary along the trench. The Wadati–Benioff zone of the eastward subducted SCS oceanic lithosphere can be clearly identified. The focal depths are down to ∼100 km near Luzon island at ∼16° N but deepen southward to a depth of ∼180 km at ∼14° N. Dips of the slab also steepen from north to south, indicating along-strike changes in the geometry of the Manila megathrust.

An earthquake-triggered submarine mass failure mechanism for the 1994 Mindoro tsunami in the Philippines: Constraints from numerical modeling and submarine geomorphology

Tsunamis have been known to result from a wide range of phenomena, such as earthquakes, volcanic eruptions, submarine mass failures, and meteorite impacts. Of earthquake-generated tsunamis, those arising from strike-slip mechanisms are less common, with the 1994 Mindoro tsunami in the Philippines among the few known examples. The 1994 Mindoro tsunami followed a Mw 7.1 earthquake along the right-lateral Aglubang River Fault. The tsunami affected the coasts surrounding the Verde Island Passage, one of the Philippines’ insular seas located between the islands of Luzon and Mindoro, and east of the West Philippine Sea margin. A total of 78 lives were lost due to the earthquake and tsunami, with 41 being directly attributed to the tsunami alone. Despite the close spatial and temporal association between the 1994 Mindoro earthquake and tsunami, previous numerical modeling suggests the need for other contributing mechanisms for the 1994 tsunami. In this study, we conducted submarine geomorphological mapping of the South Pass within the Verde Island Passage, with particular focus on identifying possible submarine mass failures. Identification of submarine features were based on Red Relief Image Map (RIMM), Topographic Position Index (topographic position index)-based landform classification, and profile and plan curvatures derived from high-resolution bathymetry data. Among the important submarine features mapped include the San Andres submarine mass failure (SASMF). The San Andres submarine mass failure has an estimated volume of 0.0483 km3 and is located within the Malaylay Submarine Canyon System in the Verde Island Passage, ∼1 km offshore of San Andres in Baco, Oriental Mindoro. We also explored two tsunami models (EQ-only and EQ+SMF) for the 1994 Mindoro tsunami using JAGURS. The source mechanisms for both models included an earthquake component based on the Mw 7.1 earthquake, while the EQ+SMF also included an additional submarine mass failure component based on the mapped San Andres submarine mass failure. Modeled wave heights from the EQ-only model drastically underestimates the observed wave heights for the 1994 Mindoro tsunami. In contrast, the EQ+SMF model tsunami wave height estimates were closer to the observed data. As such, we propose an earthquake-triggered, submarine mass failure source mechanism for the 1994 Mindoro tsunami.

The 30 years drought: Updating records on the Uropodina fauna of the Philippines

The majority of published records of Uropodina in the Philippines were by Hirschmann and his colleagues in the late 1980s to early 1990s. Most of these records were from the country’s largest Island, Luzon (34 of 51 species) especially around the province of Laguna. Although acarine diversity in the Philippines is considered as better-known than that of neighboring countries in Southeast Asia, no additional records of Uropodina have been published after 1992, a 30-year drought. In January and February of 2016, we conducted collections in several parts of Luzon Island as part of a larger study on uropodine phylogeny. In the current study, we present initial results from this expedition on uropodine diversity, based on morphospecies. We’ve identified at least 52 species from 23 genera in 12 families including possible new country records for 5 genera and 3 families. We provide new insights on the group’s diversity by comparing numbers from the current study to previous records. The aim is to use these results as benchmark for further studies on the systematics of Uropodina in the Philippines. 

DNA Barcoding of Scoliid Wasps (Hymenoptera: Scoliidae) From Selected Sites in Luzon Island, Philippines

DNA Barcoding of Scoliid Wasps (Hymenoptera: Scoliidae) From Selected Sites in Luzon Island, Philippines

Design and experimental research of a novel deep-sea self-sustaining profiling float for observing the northeast off the Luzon Island

To understand the physical ocean laws of ocean circulation in the deep ocean below 2000 m, a profiling float named FUXING is presented to meet the deep-ocean observation requirements at a depth of 4000 m. First, to meet the low energy consumption and buoyancy regulation stability of the profiling float, the low–power buoyancy adjustment process of FUXING is effectively solved by introducing the external seawater pressure as the driving force. Then, to reduce the energy consumption of the single profile for the profiling float, the optimization of the oil draining adjustment mode in the floating process is studied. Simultaneously, a buoyancy-driven system characterization test was performed to examine the buoyancy adjustment of FUXING. When the frequency of oil draining is 15 times, the total energy consumption of FUXING is the lowest. Finally, FUXING was deployed in the northeast off the Luzon Island to validate the feasibility and reliability. The at-sea experiments indicated that the optimized oil draining adjustment mode can reduce the total energy consumption in the floating process by more than 20%. The profile data showed that the outer sea water gradually mixes with the South China Sea water after passing through the northeast off the Luzon Island.

Managing nitrogen environmental impacts to improve green technical efficiency in Philippines rice cultivation

The efficient use of nitrogen fertilisers is a global priority to optimise the economic and environmental outcomes of farming. This paper is the first to consider pollution in the form of nitrous oxide emissions and excess nitrogen to analyse technical efficiency (TE) in farming. This is done by extending the two-stage double bootstrap Data Envelopment Analysis to explicitly model nitrogen pollutants as undesirable outputs. We compared green TE (when undesirable pollutants are considered) and conventional TE (without pollutants) using a case study of 33 rice-producing provinces in the Philippines. Provinces in Mindanao, Luzon, and Visayas islands experienced improvements in green TE but stagnant conventional TE from 2006 to 2017. Although transplanting rice seedlings (rather than direct sowing of seeds) improved both green and conventional TE, seed quality was also identified as an important factor for green TE but not for conventional TE. Our analysis has implications for sustainable rice production and such analysis can be extended to other crops. To advance the effective green transformation of rice production, future research should analyse farm-level data to understand farmers’ decisions regarding seed quality, crop establishment method and nitrogen fertiliser application to devise comprehensive farm integrated management plans.

The Diurnal Variation of the Evaporation Duct Height and Its Relationship With Environmental Variables in the South China Sea

Based on data from the European Centre for Medium-Range Weather Forecasts (ECMWF) ECWMF ERA5 Reanalysis (ERA-5) and the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) datasets, the diurnal variation of the evaporation duct height (EDH) in the South China Sea (SCS) and its relationship with environmental variables using the Naval Postgraduate School (NPS) model are analyzed, discussed, and presented. The findings are given as follows. First, the EDH diurnal variations are primarily influenced by the sea-land thermal contrast, with the major influencing variables being the relative humidity (RH) and the near-surface wind speed (WS), followed by the air-sea temperature difference (ASTD). Secondly, the areas where the EDH and the RH are highly correlated are mostly in northern SCS, and the two variables are negatively correlated. Besides, in southeastern SCS, the EDH has a greater and positive correlation with the WS. Seasonal changes can be found in areas where the EDH is highly correlated with the ASTD, primarily to the northwest of Luzon Island in winter and the east coast of Vietnam in summer. Finally, the spatial patterns of the EDH first mode in the SCS present a monopolar structure with the strong loading in northern SCS.

Observation of Bottom-Trapped Topographic Rossby Waves to the West of the Luzon Strait, South China Sea

Abstract Topographic Rossby waves (TRWs) play an important role in deep-ocean dynamics and abyssal intraseasonal variations. Observational records from 15 current- and pressure-recording inverted echo sounders (CPIESs) and two moorings deployed in the northern Manila Trench (MT), South China Sea (SCS), for over 400 days were utilized to analyze the widely existing near-21-day bottom-trapped TRWs in the trench. The TRWs were generally generated in winter and summer, dominated by perturbations in the upper ocean. Kuroshio intrusion and its related variabilities contributed to the perturbations in winter, whereas the perturbations generated north of Luzon Island dominated in summer. Eddies north of Luzon propagated northwestward in the summer of 2018; however, these eddies caused the Kuroshio meanderings in the Luzon Strait (LS) in the summer of 2019. The variations in the Kuroshio path and the Kuroshio-related eddies induced TRWs in the deep ocean in regions with steep topography. However, the spatiotemporal distributions of TRWs were complex owing to the propagation of the waves. Some cases of TRWs showed no relation to the local upper-layer perturbations but propagated from adjacent regions. Some of these TRWs were induced by perturbations in the upper ocean in adjacent regions, and propagated anticlockwise in the MT with shallow water to their right, while others may be related to the intraseasonal variations in deep-water overflow in the LS and propagated northward. This study suggests that the Kuroshio and Kuroshio-related eddies significantly contribute to the dynamic processes associated with intraseasonal variations in the deep SCS through the generation of TRWs. Significance Statement Topographic Rossby waves (TRWs) are fluctuations generated when water columns travel across sloping topography under potential vorticity conservation. Based on observations of 15 current- and pressure-recording inverted echo sounders (CPIESs) and two moorings in the northern Manila Trench (MT) in the South China Sea (SCS), TRWs with periods of approximately 21 days were observed and analyzed. This study describes the generation, propagation, and spatiotemporal distribution of TRWs west of the LS and confirms that regional Kuroshio meanderings and upper eddies play important roles in the dynamic processes associated with intraseasonal variations in the deep SCS; the study may thus contribute to knowledge on the dynamic response of the abyssal current to mesoscale perturbations in the upper ocean.

How did sediments disperse and accumulate in the oceanic basin, South China Sea

Quantification of the sedimentary accumulation and dispersion process of the South China Sea (SCS) not only establishes an important part on the “source-to-sink” process in Southeast Asia, but also sheds lights on the submarine slope failure and associated submarine canyon/channels formation. Based on geological interpretations of more than 30 multichannel seismic profiles covering the whole oceanic basin with constraints from IODP Expedition drilling results, we calculated the sediment budget of the oceanic basin since the Oligocene on a million-year geological scale. Sediment isopach maps in different geological time were reconstructed to understand the controlling factors dominating the Cenozoic sedimentary accumulation and dispersion process, as well as the possible sedimentary provenances. Results show that the sediment budget of the whole oceanic basin increased gradually with time, although the rate has not been consistent over time. It was complicated by regional tectonics, including the spreading of the SCS, the uplift of the Tibet Plateau and Taiwan, changes in the Asian monsoon, rerouting and organization of the river systems, and sea level changes. Submarine channel/canyon systems developed in the continental margin acted as the major conduits for terrestrial sediments discharging into the oceanic basin. We observe two decrease trends in sediment accumulation rates occurred in the Southwest Sub-basin during the Late Miocene, and in the Northwest Sub-basin during the Pliocene. The former might be related with the local rifting event in the Mekong Shelf, which trapped most of the terrestrial input. While the later was due to the retreat of the Central Canyon and Pearl River Canyon in the Late Pliocene. Sediment isopach maps indicate that the sediment accumulation was dominantly in the northern flank of the SCS oceanic basin before the Late Miocene, with the depocenters generally distributed at the mouth of the channel/canyon systems and slope foot area near basement highs; the main depocenters gradually migrated to the southern flank of the basin since the Pliocene. This is likely due to an increase sediment from the Mekong River and the high sea level. An exception is the development of a new depocenter in the northeast related with the Taiwan orogeny. The primary sediment provenances include South China, Tibet Plateau, Indo-China Peninsula, and Taiwan Island, with minor contributions from the Hainan Island, Palawan, Luzon Islands, as well as local basement highs developed on the continental margin.

Crustal structure of the northern Manila subduction zone: Is thinned continental crust or oceanic crust subducting beneath the Luzon arc and forearc?

Forward and inverse P-wave velocity models along an E-W 280-km-long wide-angle reflection/refraction profile at 21°N across the northeastern South China Sea margin and Manila subduction zone reveal a 10–12 km thick thinned continental crust (TCC) located west of the Manila transcurrent fault (MTF) and Manila slab. The TCC is divided in two parts separated by the intra-continental velocity difference boundary (VDB). West of the VDB, the TCC is located above a high velocity layer (HVL). East of the VDB, the TCC consists of three layers: an undefined body with a velocity inversion at its base above the upper and lower crusts. The VDB and MTF merge east of the Hengchun peninsula showing that the TCC located east of the VDB decreases in size and disappears to the north. The distribution of earthquakes (EQs) shows that ∼80 km of crust have subducted east of the MTF since the onset of Luzon arc collision with Eurasia at ∼7 Ma. All published tomographies suggest the subduction of oceanic crust (OC). However, due to crustal corrections, up to a maximum width of 40 km of TCC might eventually exist in the upper part of the Manila slab instead of OC. Two end-members with 40 km of TCC or not in the upper part of the Manila slab were restored at ∼7 Ma. Since that time, the north Luzon island moved ∼600 km in the northwest while part of this motion was absorbed near the Hengchun peninsula by shrinking of Eurasia TCC, resulting in a ∼ 20° clockwise rotation of the Manila slab and MTF. Small Luzon arc blocks started to rotate 10°-30° clockwise at ∼7 Ma below northern Taiwan, 3–4 Ma in the Coastal range and 1 Ma in Lutao and Lanyu islands and not south of the Hengchun peninsula. Thus, both the clockwise rotation of the individual Luzon arc blocks and of the Manila slab and MTF might explain the collision process of the Luzon arc with the Eurasia continent.

The Relationship of Leadership Style to Commitment: Choreographers and Student Dancers’ Perspective

There have been numerous studies that were already conducted concerning the relationship between styles of leadership and commitment from various disciplines; however, there are only a few to no investigations performed regards to dance space. This present study aimed to determine the relationship between the leadership styles of choreographers and the commitment of student dancers from various Higher Education Institutions (HEIs) on the entire island of Luzon in the Philippines. The gathering of data has been conducted via an online survey using LSQ and OCQ to 105 choreographers and 228 student dancers. The findings revealed that most of the choreographers apply the democratic leadership style; while the commitment level of student dancers is moderately high. Moreover, no relationship between the leadership style and commitment was observed which accepted the null hypothesis tested for this study. Based on the yielded results, leadership and management development programs are recommended to choreographers for them to be educated on what appropriate and effective leadership style they can practice, to heighten commitment and improve their relationship with student dancers. Additionally, programs to intensify the commitment of student dancers are highly suggested. Conducting a similar study is highly recommended to support or refute the findings of this research.

Philippine Catholic Festivals during the COVID-19 Pandemic: Performing Live in the ‘New’ Normal

On 16 March 2020, then Philippine President Rodrigo Duterte imposed the Enhanced Community Quarantine putting the main island of Luzon – where Manila, the National Capital Region, is located – on a total lockdown to protect the spread of COVID-19. The lockdown restricted mobility, social gatherings were prohibited, and everyone was mandated to stay inside their homes. Moreover, there was a temporary closure of what were considered as non-essential establishments, including religious institutions. Being a predominantly Roman Catholic nation, religious rituals and festivals were heavily affected by the lockdown. Many of its ritualistic and festive performances involve human contact, which serves as the faithful’s direct and intimate relationship to the heavens. This essay interrogates how cultural festivals in the Philippines, mostly organised by the Church, adapted to the global health crisis. It reflects how the adaptations challenged and recontextualised the understanding of the live vis-à-vis the context of the digital or the virtual. Finally, a preliminary speculation on the future of the religious festivals in the Philippines is provided as a concluding reflection.

Spatial and seasonal variations of near-inertial kinetic energy in the upper South China Sea: Role of synoptic atmospheric systems

The spatial distribution and seasonal variation of near-inertial kinetic energy (NIKE) in the upper ocean of the South China Sea (SCS) are examined using the Global 1/12° Analysis Hybrid Coordinate Ocean Model and the Navy Coupled Ocean Data Assimilation reanalysis product. The annual mean NIKE in the upper SCS is characterized by a rapid decay with depth and a southwestward decrease from the west of Luzon Island to the southern SCS, reflecting the pattern of near-inertial energy input by the atmospheric wind field. Owing to the changes of near-inertial wind forcing as well as the mixed layer depth, NIKE in the upper SCS exhibits a pronounced seasonal cycle. The magnitude of mixed layer NIKE averaged in the SCS in November-January is found to be approximately twice of that in April-June. Further analysis shows that the variation of near-inertial wind forcing in the SCS can, to a large extent, be explained by northerly cold surges during the winter SCS monsoon and strong tropical cyclones from the Tropical Pacific. In addition, the wind reversal during the monsoon transitional period and the low-level convergence formed by the elevated terrain of islands also contribute to oceanic near-inertial energy in the SCS.