The Clouds and the Earth's Radiant Energy System program,which uses the Moderate Resolution Imaging Spectroradiometer(CM),has been updated with the launch of new satellites and the availability of newly upgraded radiation data.The spatial and temporal variability of daily averaged synoptic 1-degree CM version 3(CMv3)(old)and version 4(CMv4)(new)downwelling shortwave(QS)and longwave radiation(QL)data in the global tropical oceans spanning 30°S-30°N from 2000 to 2017 is investigated.Daily in situ data from the Global Tropical Moored Buoy Array were used to validate the CM data from 2000 to 2015.When compared to CMv3,both QS and QL in CMv4 show significant improvements in bias,root-mean-square error,and standard deviations.Furthermore,a long-term trend analysis shows that QS has been increasing by 1 W m^(−2) per year in the Southern Hemisphere.In contrast,the Northern Hemisphere has a−0.7 W m^(−2) annual decreasing trend.QS and QL exhibit similar spatial trend patterns.However,in the Indian Ocean,Indo-Pacific warm pool region,and Southern Hemisphere,QL spatial patterns in CMv3 and CMv4 differ with an opposite trend(0.5 W m^(−2)).These annual trends in QS and QL could cause the sea surface temperature to change by−0.2 to 0.3℃per year in the tropical oceans.These results stress the importance of accurate radiative flux data,and CMv4 can be an alternative to reanalysis or other model-simulated data.
The three-stream radiation transfer model is used to investigate the fluctuation in the underwater diffuse attenuation coefficient of downwelling irradiance in the polar ocean with a high solar zenith angle and different direct radiation proportions.First,the applicability of the three-stream radiation model in the polar region is validated by using 18 in situ observation data from September to October 2009 in the Beaufort Sea.Statistics show that in the absence of sea ice,the average relative errors between the simulation and observation values for 490 nm downwelling irradiance (E_(d)(490)) and its diffuse attenuation coefficient (K_(d)(490)) are 7.04%and 9.88%,respectively.At the stations surrounded by sea ice,the radiation is relatively small due to ice blocking,and the average relative errors simulated by the model reach 15.89%and 15.55%,respectively.Second,simulations with different chlorophyll concentrations and different proportions of direct radiation reveal that a high solar zenith angle has a greater impact on K_(d)(490) in the surface water.K_(d)(490) is less affected by the light field (affected by the solar zenith angle and the proportion of direct radiation) at depths greater than 30 m,and meets the linear relationship with the inherent optical parameters(the sum of the absorption coefficient and backscattering coefficient).The surface K_(d)(490) is still consistent with that at a depth of more than 50 meters under a high solar zenith angle,implying that the surface K_(d)(490) can also be considered as an inherent optical parameter at a high solar zenith angle (greater than 60 degrees).The relative error of obtaining surface K_(d)(490) by using the linear relationship at the 50 m layer is found to be less than 8%in the seawater with chlorophyll concentration greater than0.05 mg m^(-3).The effect of the solar zenith angle and proportion of direct radiation can be ignored when measuring the diffuse attenuation coefficient in the polar region.Finally,the model can correct the ice-induced fluctuation in
Based on observational evidence and the known physical characteristics of surface gravity waves, an argument is made that downwelling is not a significant feature over the life history of these waves under the usual conditions existing in the open oceans. Since it has recently been predicted that upwelling due to surface gravity waves should occur within a storm at sea, when the waves are growing in amplitude, the contrast is explained. As a result the importance of the upwelling concept due to waves in stimulating biological productivity is further emphasized, and the possibility for reducing global warming is worth repeating.
For the Pearl River plume, the supercritical, distinct plume front appears in downwelling-favorable winds, which is easily observed due to the distinct boundary between the plume water and the ambient water. In this paper, in situ and satellite observations of a plume front are utilized to explore the Pearl River plume front properties under the downwelling-favorable winds. Field observations clearly show frontal structure, especially the two-layer structure in the plume water and the downward-motion of water in the frontal region. The Advanced Synthetic Aperture Radar(ASAR) images are also analyzed to unveil the plume front: there is a white stripe on the west side out of the river mouth under downwelling-favorable winds, which is identified as a supercritical plume front, and the width of the plume front is about 250 m. The normalized velocity gradient shows the intense velocity convergence in the front region. Also, analyses of ASAR images imply that the river discharge plays an important role in controlling the location and shape of the front.
The diffuse attenuation coefficient （Kd） for downwelling irradiance is calculated from solar irradiance data measured in the Arctic Ocean during 3rd and 4th Chinese National Arctic Research Expedition （CHINARE）, including 18 stations and nine stations selected for irradiance profiles in seawater respectively. In this study, the variation of attenuation coefficient in the Arctic Ocean was studied, and the following results were obtained. First, the relationship between attenuation coefficient and chlorophyll concentration in the Arctic Ocean has the form of a power function. The best fit is at 443 nm, and its determination coefficient is more than 0.7. With increasing wavelength, the determination coefficient decreases abruptly. At 550 nm, it even reaches a value lower than 0.2. However, the exponent fitted is only half of that adapted in low-latitude ocean because of the lower chlorophyll-specific absorption in the Arctic Ocean. The upshot was that, in the case of the same chlorophyll concentration, the attenuation caused by phytoplankton chlorophyll in the Arctic Ocean is lower than in low-latitude ocean. Second, the spectral model, which exhibits the relationship of attenuation coefficients between 490 nm and other wavelength, was built and provided a new method to estimate the attenuation coefficient at other wavelength, if the attenuation coefficient at 490 nm was known. Third, the impact factors on attenuation coefficient, including sea ice and sea water mass, were discussed. The influence of sea ice on attenuation coefficient is indirect and is determined through the control of enter- ing solar radiation. The linear relationship between averaging sea ice concentration （ASIC, from 158 Julian day to observation day） and the depth of maximum chlorophyll is fitted by a simple linear equation. In addition, the sea water mass, such as the ACW （Alaskan Coastal Water）, directly affects the amount of chlo- rophyll through taking more nutrient, and results in the higher attenuation coefficient in the
