Observation of Arctic surface currents using data from a surface drifting buoy

During the 10th Chinese Arctic scientific expedition carried out in the summer of 2019,the surface current in the high-latitude areas of the Arctic Ocean was observed using a self-developed surface drifting buoy,which was initially deployed in the Chukchi Sea.The buoy traversed the Chukchi Sea,Chukchi Abyssal Plain,Mendeleev Ridge,Makarov Basin,and Canada Basin over a period of 632 d.After returning to the Mendeleev Ridge,it continued to drift toward the pole.Overall,the track of the buoy reflected the characteristics of the transpolar drift and Chukchi Slope Current,as well as the inertial flow,cross-ridge surface flow,and even the surface disorganized flow for some time intervals.The results showed that:(1)the transpolar drift mainly occurs in the Chukchi Abyssal Plain,Mendeleev Ridge,and western Canada Basin to the east of the ridge where sea ice concentration is high,and the average northward flow velocity in the region between 79.41°N and 86.32°N was 5.1 cm/s;(2)the average surface velocity of the Chukchi Slope Current was 13.5 cm/s,and while this current moves westward along the continental slope,it also extends northwestward across the continental slope and flows to the deep sea;and(3)when sea ice concentration was less than 50%,the inertial flow was more significant(the maximum observed inertial flow was 26 cm/s,and the radius of the inertia circle was 3.6 km).

Surface circulation derived from drifting buoys in mid- and low-latitude Pacific

A dataset of drifting buoys from the Marine Environmental Data Service of Canada was analyzed to map surface circulation of the Pacific. More information of the surface circulation than that acquired before was reported in this paper, showing clear and strong western boundary currents, equato- rial currents, and subtropical gyres in the North and South Pacific regions in velocity field, with a more systematic structure in the North Pacific.

Extreme air-sea turbulent fluxes during tropical cyclone Barijat observed by a newly designed drifting buoy

Using in situ observations collected by a drifting air-sea interface buoy(DrIB)in the northern South China Sea from August 30 to September 13,2018,the extreme air-sea turbulent fluxes that occurred from September 8 to 13 during tropical cyclone(TC)Barijat were investigated.The most striking features were substantial increases in momentum and heat fluxes,with maximum increases of 10.8 m s−1 in the wind speed(WS),0.73 N m^(-2)in the wind stress,68.1 W m^(-2)in the sensible heat fluxes(SH)and 258.8 W m^(-2)in the latent heat fluxes(LH).The maximum WS,wind stress,SH and LH values amounted to 15.3 m s−1,0.8 N m^(-2),70.9 W m^(-2)and 329.9 W m^(-2),respectively.Using these new DrIB observations,the performance of two state-of-the-art,high-resolution reanalysis products,ERA5 and MERRA2,was assessed.The consistency of the observed values with ERA5 was slightly better than with MERRA2,reflected in higher correlations but both products underestimated the WS during TC conditions.In calm weather conditions,the turbulent heat fluxes were overestimated,because they simulated a too dry and cold atmospheric state,enhancing the air-sea differences in temperature and humidity.Considering that an accurate representation of the air-sea turbulent and momentum fluxes is essential for understanding and predicting ocean and atmospheric variability,our findings indicate that more high-quality temperature and relative humidity observations are required to evaluate and improve existing reanalysis products.

Data Quality Control Method of a New Drifting Observation Technology Named Drifting Air-Sea Interface Buoy

An integral quality control(QC)procedure that integrates various QC methods and considers the design indexes and operational status of the instruments for the observations of drifting air-sea interface buoy was developed in the order of basic in-spection followed by targeted QC.The innovative method of combining a moving Hampel filter and local anomaly detection com-plies with statistical laws and physical processes,which guarantees the QC performance of meteorological variables.Two sets of observation data were used to verify the applicability and effectiveness of the QC procedure,and the effect was evaluated using the observations of the Kuroshio Extension Observatory buoy as the reference.The results showed that the outliers in the time series can be correctly identified and processed,and the quality of data improved significantly.The linear correlation between the quality-controlled observations and the reference increased,and the difference decreased.The correlation coefficient of wind speed before and after QC increased from 0.77 to 0.82,and the maximum absolute error decreased by approximately 2.8ms^(-1).In addition,air pressure and relative humidity were optimized by 10^(-3)–10^(-2) orders of magnitude.For the sea surface temperature,the weight of coefficients of the continuity test algorithm was optimized based on the sea area of data acquisition,which effectively expanded the applicability of the algorithm.

Comprehensive Marine Observing Experiment Based on High-Altitude Large Unmanned Aerial Vehicle(South China Sea Experiment2020 of the “Petrel Project”)

In collaboration with 12 other institutions, the Meteorological Observation Center of the China Meteorological Administration undertook a comprehensive marine observation experiment in the South China Sea using the Yilong-10 high-altitude large unmanned aerial vehicle(UAV). The Yilong-10 UAV carried a self-developed dropsonde system and a millimeter-wave cloud radar system. In addition, a solar-powered unmanned surface vessel and two drifting buoys were used. The experiment was further supported by an intelligent, reciprocating horizontal drifting radiosonde system that was deployed from the Sansha Meteorological Observing Station, with the intent of producing a stereoscopic observation over the South China Sea. Comprehensive three-dimensional observations were collected using the system from 31 July to2 August, 2020. This information was used to investigate the formation and development processes of Typhoon Sinlaku(2020). The data contain measurements of 21 oceanic and meteorological parameters acquired by the five devices, along with video footage from the UAV. The data proved very helpful in determining the actual location and intensity of Typhoon Sinlaku(2020). The experiment demonstrates the feasibility of using a high-altitude, large UAV to fill in the gaps between operational meteorological observations of marine areas and typhoons near China, and marks a milestone for the use of such data for analyzing the structure and impact of a typhoon in the South China Sea. It also demonstrates the potential for establishing operational UAV meteorological observing systems in the future, and the assimilation of such data into numerical weather prediction models.

Variation of Sea Ice Temperature from CHINARE 2003 and Its Application on Sea Ice Model Evaluation

Variation of vertical profiles of sea ice temperature and adjacent atmosphere and ocean temperatures were measured by ice drifting buoys deployed in the northeast Chukchi Sea as part of the 2003 Chinese Arctic Research Expedition.The buoy observations (September 2003 to February 2005) show that the cooling of the ice began in late September,propagated down through the ice,reaching the bottom of the ice in December,and continued throughout the winter.In winter 2003/04,some obvious warmings were observed in the upper portion of the ice in response to major warmings in the overlying atmosphere associated with the periodicity of storms in the northeast Chukchi Sea.It is found that the melt season at the buoy site in 2004 was about 15% longer than normal.The buoy observed vertical ice temperature profiles were used as a diagnostic for sea ice model evaluation.The results show that the simulated ice temperature profiles have large discrepancies as compared with the observations.

A Study of Transport and Impact Strength of Fukushima Nuclear Pollutants in the North Pacific Surface

Based on the statistics of surface drifter data of 1979-2011 and the simulation of nuclear pollutant particulate move- merits simulated using high quality ocean reanalysis surface current dataset, the transport pathways and impact strength of Fuku-shima nuclear pollutants in the North Pacific have been estimated. The particulates are used to increase the sampling size and en- hance the representativeness of statistical results. The trajectories of the drifters and particulates are first examined to identify typical drifting pathways. The results show that there are three types of transport paths for nuclear pollutants at the surface： 1） most pollutant particles move eastward and are carried by the Kuroshio and Kuroshio-extension currents and reach the east side of the North Pacific after about 3.2-3.9 years; 2） some particles travel with the subtropical circulation branch and reach the east coast of China after about 1.6 years according to one drifter trajectory and about 3.6 years according to particulate trajectories; 3） a little of them travel with local, small scale circulations and reach the east coast of China after about 1.3-1.8 years. Based on the par-tieulates, the impact strength of nuclear pollutants at these time scales can be estimated according to the temporal variations of relative concentration combined with the radioactive decay rate. For example, Cesium-137, carried by the strong North Pacific current, mainly accumulates in the eastern North Pacific and its impact strength is 4% of the initial level at the originating Fuku- shima area after 4 years. Due to local eddies, Cesium-137 in the western North Pacific is 1% of the initial pollutant level after 1.5 years and continuously increases to 3% after 4 years. The vertical movement of radioactive pollutants is not taken into account in the present study, and the estimation accuracy would be improved by considering three-dimensional flows.

Estimation of buoy drifting based on adaptive parameter-varying time scale Kalman filter

To solve Kalman filter with dynamic time scale problem,an adaptive parameter-varying time scale kalman filter(APVTS-KF)is designed.An adaptive mechanism for choosing the covariance of state noise is designed.APVTS-KF is used to estimate the buoy drifting trajectory with different report intervals.Position drifting data of four buoys are used to test the proposed algorithm.The influence of report interval,drifting distance,adaptive factor and noise covariance are analysed and compared.The experimental results and error analysis show that APVTS-KF is better than other algorithms in trajectory estimation.Thus,Kalman filtering can be used for accurate trajectory estimation in the actual situation of buoy drifting with dynamic time intervals.

An ensemble estimation of impact times and strength of Fukushima nuclear pollution to the east coast of China and the west coast of America

Based on the statistics of all surface drifting buoys of 1978-2011 and Lagrangian tracers simulated from high quality ocean reanalysis currents,the impact times and strength of Fukushima nuclear pollution to the east coast of China and the west coast of America have been estimated.Under the circumstances of the radioactive pollutants drifting in the ocean surface,preliminary research results show that while the tracers took about 4 years to reach the west coast of USA,there are two types of tracers to carry out Fukushima nuclear pollutants to reach the east coast of China,corresponding to 1.5-year recirculation gyre transport and 3.5-year subtropical circulation transport.The distributions of the impact strength at these time scales are given according to the variation of relative number concentration with time combined with the decaying rate of radioactive matter.For example,starting from 1% at 1.5-year,of the initial level at the originating area of Fukushima nuclear pollution,the impact strength of Cesium-137 in the South China Sea continuously increases up to 3% by 4 years,while the impact strength of Cesium-137 in the west coast of America is as high as 4% due to the role of strong Kuroshio-extension currents as a major transport mechanism of nuclear pollutants for that area.