Effects Of Transfer Model Of Shortwave Radiation On Temperature And Mixing In Upper Ocean

Solar radiation is the most important heat source of ocean,in which the energy with wavelengths of?400-700nm(visible domain),which can penetrate to some depth,accounts for 44%of total solar energy.The solar radiation penetrating sea surface would play an important role in the vertical temperature structure in upper ocean and photosynthesis of phytoplankton,which will further affect the thermal dynamic processes and ecosystem in mixed layer of ocean.So the studies of radiation transfer in upper ocean is an important part in study of ocean optics.The transmission of shortwave radiation under sea surface is influenced by several factors,including concentration of chlorophyll(Chl,mg m-3),Colored Dissolved Organic Matter(CDOM,m-1)and so on.In previous study,a variety of solar transmission parameterizations were used to simulate ocean radiant,in which the coefficients are dependent on water type,Chl or inherent optical properties(IOP).In present,most ocean models used the Paulson(1977)'s method to calculate the transmission,which is a multiple exponential terms equation whose coefficients are given as a function of Jerlov water type.It is computationally simple but failed to accurately represent optical properties.Both of these methods to calculate transfer of radiation by Chl and IOP from Ohlman(2003)and Lee(2005)had better accuracy and flexibility.But increased model accuracy is not believed to be worth the computational overhead in ocean models.To evaluate the influence of the difference of these 3 transmission equations on the ocean temperature,we built a 200m-depth 1-D ocean model based on ROMS,modified the calculation of radiation transmission and compared the temperature results of different transmission equation of shortwave radiation.Firstly,for the 4 testing stations with different water type,we compared the result from different transmission equations,and got the main findings as below:(1)the difference of transmission of shortwave radiation would affect the vertical temperature result,up to 1.5-2?.The change of temperature(higher or lower)is more dependent on the Tr calculated by 3 different equations.(2)The influence is more obvious at deeper water than near-surface water.The sensitivity analysis of the influence on temperature caused by transmission model to water type and radiation flux shows that:(1)The influence of different transmission equation on temperature would reach deeper water in clear water,but there is no obvious relation between the influence degree and water type.The difference caused by transmission equation is more dependent on the calculation result of Tr.(2)The influence degree on temperature caused by transmission equation is related to radiation flux.Where the latitude is lower,the difference of temperature of models using different equations would much more obvious than high latitude area.(3)In the comparison of model results of transmission equation using monthly variable data and fixed data,we found that the difference of Ohlmann's equation is more obvious.The temperature difference between monthly variable parameters and fixed parameters would be up to 0.5 ?.But in the same experiment,the temperature difference of Lee's equation is almost 0.It is speculated that it is because the change of chlorophyll is much higher than IOP in this station.