Modeling Mackerel Tuna (Euthynnus affinis) Habitat in Southern Coast of Java: Influence of Seasonal Upwelling and Negative IOD

We used fishery catch data from Cilacap Fishing Port and Copernicus data set in July 2016-December 2017 to investigate the impacts of Indian Ocean Dipole (IOD) on upwelling and mackerel tuna distribution in the southern coast of Java. This study implemented a Generalized Additive Model (GAM) for habitat prediction of mackerel tuna in the waters. The present study showed that the extreme negative IOD in 2016 caused a weaker southeasterly wind and even a reversal to the northwesterly wind, as seen off Sumatra in September 2016. The situation produced vertically mixed layer thickening and no upwelling during the southeast monsoon event 2016, consequently resulted in warmer temperature and fewer Chlorophyll-a (Chl-a) compared to the southeast monsoon event 2017. The mackerel tuna production significantly dropped in 2016 and rose in 2017, particularly during the upwelling event. The high Habitat Suitability Index (HSI) was found in southern Central Java in July 2017, expanded bigger in August 2017, and decreased in September 2017. During July and August 2016, the high HSI covered only a less area in the region and disappeared in September 2017. The high HSI indicates that the oceanographic factor is consistent with the catch probability of mackerel tuna.

The Strong Upwelling Event off the Southern Coast of Sri Lanka in 2013 and Its Relationship with Indian Ocean Dipole Events

ABSTRACTMultisource satellite remote sensing data have been used to analyze the strong upwelling event off the southern coast of Sri Lanka in 2013 and its relationship with Indian Ocean dipole (IOD) events. The upwelling area in 2013 is 5.7 times larger than that in a normal year and lasts from June to August, with the peaks of the cooling anomaly reaching −1.5°C and the positive chlorophyll a concentration anomaly exceeding 3.1 mg m−3. In 2013, the negative unseasonable IOD (IODJJA) event enhances the southwest monsoon, while the blocking of the monsoon wind by the island results in a stronger westerly/northwesterly wind stress off the southern coast of Sri Lanka and a weaker westerly/northwesterly wind stress over the eastern Sri Lanka waters. This causes stronger offshore transport and positive Ekman pumping off the southern coast, forming a strong upwelling event there. Further analysis indicates that the interannual variability of the upwelling, as represented by a newly constructed index based on satellite observations, is primarily caused by the variations of local wind associated with the IOD. The upwelling off the southern coast of Sri Lanka weakens (strengthens) in the positive (negative) IOD years. However, an analysis based on 21 IOD events during 1982–2019 demonstrates that the effects of the three types of IOD events, including IODJJA, prolonged IOD (IODLONG), and normal IOD (IODSON), on the upwelling are different. Compared to the IODSON events, the IODJJA and IODLONG events tend to have stronger influences due to their earlier developing phases.

Analysis of a Severe PM2.5 Episode in the Seoul Metropolitan Area in South Korea from 27 February to 7 March 2019: Focused on Estimation of Domestic and Foreign Contribution

In this study, domestic and foreign contributions to a severe PM2.5 episode in South Korea, in which “emergency reduction measures against particulate matter” were issued, were analyzed. During the period between 27 February and 7 March in 2019 when high PM2.5 concentrations occurred, the PM2.5 concentration in the Seoul metropolitan area (SMA) in South Korea was approximately 87.3 μg/m3 on average, and a severe PM2.5 concentration level of approximately 113.4 μg/m3 was observed between 3 March and 5 March. The results of the analysis conducted using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model and meteorological observation data showed that northwesterly wind or westerly winds were formed during the P1 and P3 periods when the PM2.5 concentration markedly increased. When the PM2.5 concentrations in East Asia were simulated using the Community Multiscale Air Quality (CMAQ), it was found that the high PM2.5 concentrations that occurred in the SMA of South Korea were mostly affected by PM2.5 transported over long distances and following atmospheric stagnation. When the domestic and foreign contributions were evaluated using the brute-force method (BFM), the foreign and domestic contribution concentrations were found to be 62.8 and 16.8 μg/m3, respectively, during the target period of this study. It was also found that the foreign contribution was 78.8%, while the domestic contribution was 21.2%.

February

This chapter describes snow in the east country in February. In the beginning, static air from cold Arctic collided with a wet west front. Snowflakes fell heavily, resulting to eight inches of snow by morning. In the village, small children hauled sledges; others shoveled drives. Next morning, twice the car was ice-stranded; all puddles were frozen. Whole fields of winter wheat were yellowed by frost. Meanwhile, in Boxford high street, most shop fronts became private houses and people stayed inside. In the valley, there was a relentless wall of cold northwesterly wind. The chapter also recounts a gathering at Snape Maltings for Place: Taking the Waters, which was an exploration of the warp of water and the coast's liminal zones.

Late Quaternary chronology of major dune ridge development in the northeast Rub' al-Khali, United Arab Emirates

The northeastern sector of the Rub' al-Khali desert in the eastern United Arab Emirates (UAE) is dominated by large NE–SW trending dune ridges orientated perpendicular to the currently prevailing northwesterly wind regime. In this study, extensive use has been made of artificially exposed sections through these major dune ridges that reveal internal sedimentary structures and allow an intensive, high-resolution sampling programme to be carried out. Here, we present the optical dating results for samples from 7 sections. The results indicate that dune activity and preservation occurred within the periods 7–3 ka, 16–10 ka and 22–20 ka with evidence of earlier preservation during marine oxygen isotope stages MIS 3 and 5, with net accumulation rates in the range 2.2–25 m.ka− 1. In several instances, hiatuses in the preserved record of dune accumulation coincide with stratigraphic bounding surfaces visible in the exposed section profiles with associated truncation of internal sedimentary structures. Caution must be exercised when interpreting such gaps in the recorded accumulation chronologies of these dunes since these may simply constitute phases of low preservation potential rather than phases of low aeolian activity. Other factors such as sediment supply and availability in relation to sea-level dynamics may be significant and are also considered.

Comparison of East Asian winter monsoon indices

Four East Asian winter monsoon (EAWM) indices are compared in this paper. In the research periods, all the indices show similar interannual and decadal-interdecadal variations, with predominant periods centering in 3–4 years, 6.5 years and 9–15 years, respectively. Besides, all the indices show remarkable weakening trends since the 1980s. The correlation coefficient of each two indices is positive with a significance level of 99%. Both the correlation analyses and the composites indicate that in stronger EAWM years, the Siberian high and the higher-level subtropical westerly jet are stronger, and the Aleutian low and the East Asia trough are deeper. This circulation pattern is favorable for much stronger northwesterly wind and lower air temperature in the subtropical regions of East Asia, while it is on the opposite in weaker EAWM years. Besides, EAWM can also exert a remarkable leading effect on the summer monsoon. After stronger (weaker) EAWM, less (more) summer precipitation is seen over the regions from the Yangtze River valley of China to southern Japan, while more (less) from South China Sea to the tropical western Pacific.

Some Observations of the Mountain Wave in Eastern Colorado

Observations of the mountain wave that forms just to the east of the north-south mountain range in eastern Colorado were collected over a four-year period. Analysis of the circulation in the middle troposphere shows that mountain waves in general and strong waves in particular are more likely to form with a northwesterly wind than with wind from any other direction.

Heavy Snowstorms at Blue Hill (Boston), Mass.*

During the 24 hours before the all-snow storms (of which there were 12), the pressure on Mt. Washington (elevation 6,288 ft. and 142 miles to the north) rises, the usually prevailing strong northwesterly wind drops sharply, and the temperature mostly shows a rise from a low value. Before heavy snow mixed or alternating with rain (4 storms), the pressure on Mt. Washington starts high and falls, the temperature is moderate, and the wind velocity is comparatively low, frequently with southerly or easterly components.