Study On Air-sea Heat Flux Characteristics Of Nordic Sea Based On Buoy Observation And Reanalysis Data Set

As the only channel for the North-Atlantic Current to enter the polar region,the Nordic Sea is the most important channel for the radial heat transport in the subpopulation of the northern hemisphere.In the process of transporting the heat inside the ocean to continue to release to the atmosphere in sensible and latent way,as the northern hemisphere to drive high-latitude atmospheric circulation of an important part.The study shows that the Nordic sea area is the core area of the Arctic Oscillation and the North Atlantic Oscillation.The air-sea turbulent heat exchange process affects the energy balance of the interface in the Nordic sea;On the other hand,the change of air-sea turbulent heat exchange can lead to the cooling of thesea surface,which causes the abnormal change of the upper ocean heat content,and then has an indirect effect on the formation of deep water in the North Atlantic.The changes in the heat transport of the Nordic Sea are also closely related to the cyclone activity in the Greenland Sea,while the changes in the path and intensity of the cyclone activity in the Greenland Sea affect the liquid water transport and sea ice changes in the Arctic Atlantic sector.Therefore,the study of the Nordic sea-air heat flux has an important contribution to the study of the large-scale atmospheric circulation in the northern hemisphere.At the same time,the change of turbulent heat flux at air-sea interface is of great significance to the study of ocean and atmospheric circulation model,the study of sea-air interaction,and the evaluation of numerical weather forecasting model.The study of the air-sea heat flux in the Nordic sea-air interface requires the reanalysis data.However,there are uncertainties in the existing sea-air flux data sets(including satellite remote sensing inversion data and reanalysis data).The main reason for the deviation is that the estimation of the surface roughness parameters in the bulk algorithm,it is not accurate enough;secondly it is the measurement error of the air-sea interface elements need for calculating the heat flux.Therefore,it is very urgent and important to make full use of the observation data of buoy to improve the method of estimating air-sea heat flux,and to verify and compare the relevant data products.For the first time in China,23 days of continuous on-site buoy observation was carried out in the northwestern Lofoten Basin(5°E,70°N).Based on the obtained data,this paper firstly analyzes and describes the obtained data and calculates the turbulent heat flux in the sea surface.The relationship between sea surface elements and heat flux and the short-term characteristics of heat transport during the observation were further analyzed:the sea surface sensible heat flux is-5.21~41.15W/m~2,the latent heat flux is-3.59~82.81W/m~2.The ocean is positive to the atmosphere,indicating that the heat flux of the Lofoten basin is dominated by the ocean to the atmosphere.Both show an increasing trend,the latent heat flux is an average of 3.4 times that of the sensible heat flux.The temperature difference between sea and air is the dominant factor in the influence of heat transmission in the northwestern Haworthan basin.Under low and medium wind conditions,the difference of atmospheric humidity is the dominant factor of latent heat flux.Power spectrum analysis showed that the sensible heat flux had a major cycle of 15.4 days,while the latent heat flux had a major cycle of 15.4 days and a high frequency period of about 3 days.Secondly,the data of the four sets of reanalysis data sets(ERA-Interim,OAFlux,NCEP1 and NCEP2)are compared and evaluated in the high latitudes by using the obtained data:The results of the four types of reanalysis data sets have a good correlation with the measured values of 10m wind speed,2m atmospheric temperature and 2m air ratio.From the statistical characteristics,the data of ERA-Interim and OAFlux are superior to NCEP1 and NCEP2 in this summer,and the maximum difference between the four types of data sets and the measured sea surface temperature is the sea surface temperature.ERA-Interim is more sensitive to changes in sea surface high frequency fluctuations.The cause of the sensible heat flux is due to the overestimation or underestimation of the sea surface temperature and the skin temperature.ERA-Interim estimates the sensible heat better than the other three.The estimation of latent heat is also increasing when the latent heat value is large.Among them,NCEP1 and NCEP2 are obviously overestimated to ERA-Interim and OAFlux,and these errors should be from the sea surface wind and sea surface than the estimated deviation of wet.OAFlux estimates the latent heat better than the other three.Finally,this paper analyzes the seasonal variation and long-term spatiotemporal variation of the Nordic Sea by using the best ERA-Interim monthly data consistent with the measured data.The results show that the Nordic Sea as a global ocean a few strong sea-air coupling waters,sensible heat and latent heat release are greater than 0all year round(the ocean is positive for the atmosphere).Three heat fluxes reached their maximum in winter and the smallest in summer,and changes in the year showed a single peak cyclical changes.The sensible heat of different seasonal distributions showed significant zonal changes,while latent heat season changes are more changes in the meridian.The largest change in sensible heat is the warm current return area on the west side of Svalbard Island.The largest change in latent heat is the Sispabe Bergen flow through the waters and western Iceland,southern waters,latent heat fluctuations are only half of the sensible heat.The contribution of the first modal variance of the EOF to the first day of the net heat flux is 48.25%,which represents the spatial variation of the Nordic sea-level anomaly,in which the cold waters of the East Greenland are the most obvious sea in the positive and negative anomalies.The annual average of the time series indicates that the first mode is gradually changing from positive anomalies to negative anomalies,and the overall trend of net heat is also reduced from the side.The second modal and third modal contribution rates are12.5%and 11.1%,respectively,and the spatial representation of the north-south dipole and the east-west seesaw distribution,where the second mode has a significant period of about four years.The time series of the third modality and the NAO index have a correlation of 0.6,indicating that the pressure changes caused by the North Atlantic Oscillation have a significant effect on the aerial heat transport in the Nordic Sea.