Three types of positive Indian Ocean dipoles and their relationships with the South Asian summer monsoon

The relationship between the Indian Ocean dipole (IOD) and the South Asian summer monsoon (SASM), which remains a subject of controversy, was investigated using data analyses and numerical experiments. We categorized IOD events according to their sea surface temperature anomaly (SSTA) pattern: Type-W and Type-E are associated with stronger SSTA amplitudes in the western and eastern poles of the IOD, respectively, while Type-C has comparable SSTA amplitudes in both poles during boreal autumn. Type-W is associated with a weak SASM from May to summer, which contributes to substantial warming of the western pole in autumn; the east–west SST gradient linked to the warming of the western pole causes weak southeasterly wind anomalies off Sumatra and feeble and cold SSTAs in the eastern pole during the mature phase. Type-E is associated with a strong SASM and feeble warming of the western pole; interaction between the strong SASM and cold SSTAs in the eastern pole in summer results in strong southeasterly wind anomalies off Sumatra and substantial cooling of the eastern pole during the mature phase. For Type-C, warming of the western pole and cooling of the eastern pole develop synchronously without apparent SASM anomalies, and reach comparable intensities during the mature phase. Observations and numerical simulation results both indicate the role of disparate SASM anomalies in modulating SSTA patterns during the development of positive IODs. Warming of the tropical Indian Ocean becomes established in the winter and spring following Type-W and Type-C IODs, but not following Type-E events.

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.

Wind-Driven Coastal Upwelling near Large River Deltas in the Laptev and East-Siberian Seas

The Lena, Kolyma, and Indigirka rivers are among the largest rivers that inflow to the Arctic Ocean. Their discharges form a freshened surface water mass over a wide area in the Laptev and East-Siberian seas and govern many local physical, geochemical, and biological processes. In this study we report coastal upwelling events that are regularly manifested on satellite imagery by increased sea surface turbidity and decreased sea surface temperature at certain areas adjacent to the Lena Delta in the Laptev Sea and the Kolyma and Indigirka deltas in the East-Siberian Sea. These events are formed under strong easterly and southeasterly wind forcing and are estimated to occur during up to 10%–30% of ice-free periods at the study region. Coastal upwelling events induce intense mixing of the Lena, Kolyma, and Indigirka plumes with subjacent saline sea. These plumes are significantly transformed and diluted while spreading over the upwelling areas; therefore, their salinity and depths abruptly increase, while stratification abruptly decreases in the vicinity of their sources. This feature strongly affects the structure of the freshened surface layer during ice-free periods and, therefore, influences circulation, ice formation, and many other processes at the Laptev and East-Siberian seas.

Influence of meteorological conditions on the concentration of NO2 and NOx in northwest Poland in relation to wind direction

Influence of meteorological conditions on the concentration of NO2 and NOx in northwest Poland in relation to wind direction The aim of the work was to assess the temporal distribution of NO2 and NOx concentration in relation to wind direction and to determine the effect of major meteorological elements on the size of NO2 and NOx concentration in northwest Poland. In the area of the research, in the period from 1st May 2005 to 30th April 2007 the highest average concentration of NO2 and NOx, both during cold and warm half-years, occurred with southeasterly wind, and the lowest with south-westerly wind for NO2 and with north-easterly wind for NOx. The highest determination coefficients and, at the same time, the smallest estimation errors for multiple regression equations, describing the dependence of the concentration of NO2 and NOx from meteorological elements, were obtained with westerly wind in the cold half-year and with south-westerly wind in the warm half-year.