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1.
Role of sea ice in air-sea exchange and its relation to sea fog   总被引：1，自引：0，他引：1  
Synchronous or quasi-synchronous stereoscopic sea-ice-air comprehensive observation was conducted during the First China Arctic Expedition in summer of 1999. Based on these data, the role of sea ice in sea-air exchange was studied. The study shows that the kinds, distribution and thickness of sea ice and their variation significantly influence the air-sea heat exchange. In floating ice area, the heat momentum transferred from ocean to atmosphere is in form of latent heat; latent heat flux is closely related to floating ice concentration; if floating ice is less, the heat flux would be larger. Latent heat flux is about 21 23.6 W*m-2, which is greater than sensible heat flux. On ice field or giant floating ice, heat momentum transferred from atmosphere to sea ice or snow surface is in form of sensible heat. In the floating ice area or polynya, sea-air exchange is the most active, and also the most sensible for climate. Also this area is the most important condition for the creation of Arctic vapor fog. The heat exchange of a large-scale vapor fog process of about 500000 km2 on Aug. 21 22,1999 was calculated; the heat momentum transferred from ocean to air was about 14.8×109 kW. There are various kinds of sea fog, radiation fog, vapor fog and advection fog, forming in the Arctic Ocean in summer. One important cause is the existence of sea ice and its resultant complexity of both underlying surface and sea-air exchange.  相似文献   

2.
Analysis of sensible heat flux(Qh),latent heat flux(Qe),Richardson number(Ri),bulk transport coefficient(Cd) and katabatic winds are presented by using the meteorological data in the near surface layer from an automatic weather station(AWS) in Princess Elizabeth Land,East Antarctica ice sheet and the data of corresponding period at Zhongshan station in 2002.It shows that annual mean air temperature at LGB69 is-25.6°C,which is 16.4°C lower than that at Zhongshan,where the elevation is lower and located on the coast.The temperature lapse rate is about 1.0°C/110 m for the initial from coast to inland.The turbulence heat flux at LGB69 displays obvious seasonal variations with the average sensible heat flux-17.9 W/m2 and latent heat flux-0.9 W/m2.The intensity(Qh Qe) of coolling source is-18.8 W/m2 meaning the snow surface layer obtains heat from atmosphere.The near surface atmosphere is near-neutral stratified with bulk transport coefficients(Cd) around 2.8×10-3,and it is near constant when the wind speed higher than 8 m/s.The speed and the frequency of easterly Katabatic winds at LGB69 were higher than that at Zhongshan Station.  相似文献   

3.
A two and a half layer oceanic model of wind-driven, thermodynamical general circulation is appliedto study the interannual oscillation of sea surface temperature (SST) in the South China Sea (SCS). Themodel consists of two active layers: the upper mixed layer (UML) and the seasonal thermocline, with themotionless abyss beneath them. The governing equations which include momentum, continuity and sea.temperature for each active layer, can describe the physics of Boussinseq approximation, reduced gravityand equatorial β-plane. The formulas for the heat flux at the surface and at the interface between twoactive layers are designed on the Haney scheme. The entrainment and detrainment at the bottom of theUML induces vertical transport of mass,momentum and heat, and couples of dynamic andthermodynamic effect.Using leap-frog integrating scheme and the Arakawa-C grid the model is forced bya time-dependent wind anomaly stress pattern obtained from category analysis of COADS. The numerical results indicate that t  相似文献   

4.
1　Introduction　TheMadden JulianOscillation (MJO)isastrongatmosphericconvection phenomenonoccurringovertheEasternIndianOceanandtheTropicalWesternPacific,usuallyinregionswithseasurfacetempera tures (SSTs)over 2 9℃ .Theeastwardmovingofalarge scalecirculat…  相似文献   

5.
A time-dependent, three-dimensional finite difference model is presented for simulating the stratifiedYellow Sea and northem East China Sea. The mode is forced by time-dependent observed wind, surfaceflux of heat, and tidal turbulence. With this model, momentum and temperature distribution can be computed,and an approximation for the sub-grid scale effects is introduced by the use of mass and momentumexchange coefficients. The vertical exchanges are quite dependent on these assumed coefficents, whichare complicated functions of the turbulence energy of tide and wind, of the stratified strength and otherfactors. This model was applied to describe the mechanics of the variations in strength and thickness ofthe thermocline covering almost the whole Yellow Sea and northern East Chna Sea in summer. Comparisonsof the computed output with obtained survey data led to some important conclusions.  相似文献   

6.
Estimates of near surface layer parameters over 78°N drifting ice in ice camp over the Arctic ocean are made using bulk transfer methods with the data from the experiments operated by the Chinese Arctic Scientific Expedition in August 22-September 3,2003.The results show that the net radiation received by the snow surface is only 3.6 W/m2,among which the main part transported into atmosphere in term of sensible heat and latent heat,which account for 52% and 31% respectively,and less part being transported to deep ice in the conductive process.The bulk transfer coefficient of momentum is about 1.16×10-3 in the near neutral layer,which is a little smaller than that obtained over 75°N drifting ice.However,to compare with the results observed over 75°N drifting ice over the Arctic Ocean in 1999,it can be found that the thermodynamic and momentum of interactions between sea and air are significant different with latitudes,concentration and the scale of sea ice.It is very important on considering the effect of sea-air-ice interaction over the Arctic Ocean when studying climate modeling.  相似文献   

7.
The Chinese east coastal areas and marginal seas are foggy regions.The development of effective forecasting methodsrests upon a comprehensive knowledge of the fog phenomena.This study provides new observations associated with the sea fogsover the northwestern Yellow Sea by means of L-band radar soundings with a high vertical resolution of 30 m.The monthly tem-perature lapse rate,the Richardson Numbers,and the humidity show obvious seasonal variations in the lower level of the planetaryboundary layer (PBL) that are related to the onset,peak and end of the Yellow Sea fog season.The typical pattern of stratification forthe sea fog season in the northwestern Yellow Sea is that a stable layer of about 400 m thick caps a 150 m conditionally unstable layer.Besides,the differences between fogs and stratus clouds in terms of humidity,turbulence and temperature are analyzed,which is ofsignificance for sea fog forecast and detection by satellites.The thickness of the sea fogs varies in different stages of the fog season,and is associated with the temperature inversion.The numerical simulation proves that the seasonal variations obtained by the radarwell represent the situations over the Yellow Sea.  相似文献   

8.
With a global GSSTF2 and NCEP/NCAR reanalysis database and observation data at the Yong Xing station of Xisha Island in the South China Sea, we simulated the turbulent sensible and latent heat flux at sea surface in Chinese and neighboring seas (hereafter termed as China seas) using a common bulk method with some improved parameters. Comparing the simulated results with the observed and reanalyzed data, the improvement yielded higher accuracy, a smaller mean square deviation within 10 W/m2, and a smaller average relative error at about 25%. In addition, spatial resolution was improved to 0.1°×0.1°. The simulation is able to replay the main features of regional and seasonal variation in turbulent heat fluxes, and also the general pattern of heat flux changes during the summer monsoon outbreak in the South China Sea.  相似文献   

9.
To study the potential effect of sea spray on the evolution of typhoons,two kinds of sea spray flux parameterizationschemes developed by Andreas (2005) and Andreas and Wang (2006) and Fairall et al.(1994) respectively are incorporated into theregional atmospheric Mesoscale Model version 3.6 (MM5V3) of Pennsylvania State University/National Center for AtmosphericResearch (PSU/NCAR) and the coupled atmosphere-sea spray modeling system is applied to simulate a Western Pacific super ty-phoon Ewiniar in 2006.The simulation results demonstrate that sea spray can lead to a significant increase in heat fluxes at theair-sea interface and the simulated typhoon's intensity.Compared with the results without sea spray,the minimum sea level pressurereduces about 8hPa after taking account of sea spray by Fairall et al.'s parameterization (1994) and about 5hPa by Andreas' (2005)and Andreas and Wang's (2006) parameterization at the end of the model integration,while the maximum 10m wind speed increasesabout 17% and 15% on average,respectively,through the entire simulation time period.Taking sea spray into account also causessignificant changes in Tropical Cyclone (TC) structure due to an enhancement of water vapor and heat transferred from the sea sur-face to the air; therefore,the center structure of the typhoon becomes more clearly defined and the wind speed around the typhooneye is stronger in numerical experiments.The simulations show that different sea spray flux parameterizations make different modifications to the TC structure.  相似文献   

10.
The energy budget and regulating factors were investigated over an estuarine wetland during one year of continuous measurement in 2006.The results show that the seasonal changes of the energy fluxes and Bowen ratio(β) were greatly affected by incoming shortwave radiation and canopy growth.During the non-growing season and early-growing season, sensible heat(H) dominated the energy flux, and β could reach a maximum of 2.5, while during most of the growing season, latent heat dominated the energy flux and β fluctuated from 0.4 to 1.0.The energy budget ratio in growing season was about 0.76, and the value would be higher if heat exchange during tidal flooding was in-cluded.During tidal flooding days, β was slightly higher than that at exposure days in most cases.Vegetation cover seems exert little effect on energy partitioning except in March when the standing dead grass intercepted the incoming radiation that might reach the soil surface and reduce the turbulence between soil and atmosphere, thus suppressing the evaporation from the soil though the soil mositure was high at that time.  相似文献   

11.
The South China Sea (SCS) is significantly influenced by El Niño and the Southern Oscillation (ENSO) through ENSO-driven atmospheric and oceanic changes. We analyzed measurements made from 1960 to 2004 to investigate the interannual variability of the latent and sensible heat fluxes over the SCS. Both the interannual variations of latent and sensible heat fluxes are closely related to ENSO events. The low-pass mean heat flux anomalies vary in a coherent manner with the low-pass mean Southern Oscillation Index (SOI). Time lags between the heat flux anomalies and the SST anomalies were also studied. We found that latent heat flux anomalies have a minimum value around January of the year following El Niño events. During and after the mature phase of El Niño, a change of atmospheric circulation alters the local SCS near-surface humidity and the monsoon winds. During the mature phase of El Niño, the wind speed decreases over the entire sea, and the air-sea specific humidity difference anomalies decreases in the northern SCS and increases in the southern SCS. Thus, a combined effect of wind speed anomalies and air-sea specific humidity difference anomalies results in the latent heat flux anomalies attaining minimum levels around January of the year following an El Niño year.  相似文献   

12.
Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.  相似文献   

13.
In this paper, fluxes of momentum and sensible heat are discussed with the data collected by tethered balloon sounding system over the Philippine Sea during the cruise of the R/VSCIENCE 1 from September through October in 1987. These fluxes were calculated using the semempirical flux-profile relationships of Monin-Obkhov similarity theory with observed data. The friction velocityU. was determined by the observed data's least-square fit with the similarity formulae under stable, neutral and unstable conditions. The roughnessZ 0 was determined byZ 0=a1 (U*/g), then substituted into the similarity formulae to computeU * again. The final values ofU * andZ 0 could be determined through this iteration. The flux temperatureθ * was calculated from the temperature profile withZ 0 determined above. Finally the fluxes of momentum and sensible heat, and the drag coefficientC D were obtained by computation withU * θ * and the wind speed (U 10) at 10 meters above the sea surface. Contribution No. 2220 from the Institute of Oceanology, Chinese Academy of Sciences. This project was supported by the National Natural Science, Foundation of China (No. 049176255).  相似文献   

14.
1 IntroductionGreen house gases, such as CO2,CH4, N2O and so on are released to the atmosphereconstantly by human activities. These gases insert positive radiative forcing to the climate.Meanwhile, aerosol, which are also released by human activities, ins…  相似文献   

15.
Effects caused by precipitation on the measurements of three-dimensional sonic anemometer are analyzed based on a field observational experiment conducted in Maoming, Guangdong Province, China. Obvious fluctuations induced by precipitation are observed for the outputs of sonic anemometer-derived temperature and wind velocity components. A technique of turbulence spectra and cospectra normalized in the framework of similarity theory is utilized to validate the measured variables and calculated fluxes. It is found that the sensitivity of sonic anemometer-derived temperature to precipitation is significant, compared with that of the wind velocity components. The spectra of wind velocity and cospectra of momentum flux resemble the standard universal shape with the slopes of the spectra and cospectra at the inertial subrange, following the-2/3 and-4/3 power law, respectively, even under the condition of heavy rain. Contaminated by precipitation, however, the spectra of temperature and cospectra of sensible heat flux do not exhibit a universal shape and have obvious frequency loss at the inertial subrange. From the physical structure and working principle of sonic anemometer, a possible explanation is proposed to describe this difference, which is found to be related to the variations of precipitation particles. Corrections for errors of sonic anemometer-derived temperature under precipitation is needed, which is still under exploration.  相似文献   

16.
We analyzed interdecadal variability of the South China Sea monsoon and its relationship with latent heat flux in the Pacific Ocean, using NCEP wind field and OAFlux heat flux datasets. Results indicate that South China Sea monsoon intensity had an obvious interdecadal variation with a decreasing trend. Variability of the monsoon was significantly correlated with latent heat flux in the Kuroshio area and tropical Pacific Ocean. Variability of latent heat flux in the Kuroshio area had an interdecadal increasing trend, while that in the tropical Pacific Ocean had an interdecadal decreasing trend. Latent heat flux variability in these two sea areas was used to establish a latent heat flux index, which had positive correlation with variability of the South China Sea monsoon. When the latent heat flux was 18 months ahead of the South China Sea monsoon, the correlation coefficient maximized at 0.58 (N=612), with a 99.9% significance level of 0.15. Thus, it is suggested that latent heat flux variability in the two areas contributes greatly to interdecadal variability of the South China Sea monsoon.  相似文献   

17.
Oceanic contribution to the poleward heat flux in the climate system includes two components: the sensible heat flux and the latent heat flux. Although the latent heat flux has been classified as atmospheric heat flux exclusively, it is argued that oceanic control over this component of poleward heat flux should play a critically important role. The so-called swamp ocean model practice is analyzed in detail, and the critical role of oceanic circulation in the establishment of the meridional moisture transport is emphasized.  相似文献   

18.
Oceanic contribution to the poleward heat flux in the climate system includes two components： the sensible heat flux and the latent heat flux. Although the latent heat flux has been classified as atmospheric heat flux exclusively, it is argued that oceanic control over this component of poleward heat flux should play a critically important role. The so-called swamp ocean model practice is analyzed in detail, and the critical role of oceanic circulation in the establishment of the meridional moisture transport is emphasized.  相似文献   

19.
1 Introduction Most of the solar radiation that ecosystem seizes is con- sumed on latent, sensible and soil heat flux. Among them, latent heat flux shares the biggest part (Gutierrez and Meizer, 1994; Ham et al., 1991; Rachidi et al., 1993). The radiation budget and the energy balance are crucial to water conversion and effective water utilization. Also, they are important parts of research of water-saving ag- riculture (Mo et al., 1997). At present, the researches on radiation budget and e…  相似文献   

20.
In this paper, the International Comprehensive Ocean and Atmosphere Data Set(ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the meteorological and oceanic conditions for sea fog formation. Sea fog over the Northern Atlantic mainly occurs over middle and high latitudes. Sea fog occurrence frequency over the western region of the Northern Atlantic is higher than that over the eastern region. The season for sea fog occurrence over the Northern Atlantic is generally from April to August. When sea fogs occur, the prevailing wind direction in the study area is from southerly to southwesterly and the favorable wind speed is around 8 m s-1. It is most favorable for the formation of sea fogs when sea surface temperature(SST) is 5℃ to 15℃. When SST is higher than 25℃, it is difficult for the air to get saturated, and there is almost no report of sea fog. When sea fogs form, the difference between sea surface temperature and air temperature is mainly-1 to 3℃, and the difference of 0℃ to 2℃ is the most favorable conditions for fog formation. There are two types of sea fogs prevailing in this region: advection cooling fog and advection evaporating fog.  相似文献   

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