Yu Hongbin, Tan Qian, Chin Mian, Remer Lorraine A, Kahn Ralph A, Bian Huisheng, Kim Dongchul, Zhang Zhibo, Yuan Tianle, Omar Ali H, Winker David M, Levy Robert, Kalashnikova Olga, Crepeau Laurent, Capelle Virginie, Chedin Alain
Earth Sciences Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
Bay Area Environmental Research Institute, Petaluma, California, USA.
J Geophys Res Atmos. 2019 Jul 27;124(14):7975-7996. doi: 10.1029/2019JD030574. Epub 2019 Jul 12.
Deposition of mineral dust into ocean fertilizes ecosystems and influences biogeochemical cycles and climate. In-situ observations of dust deposition are scarce, and model simulations depend on the highly parameterized representations of dust processes with few constraints. By taking advantage of satellites' routine sampling on global and decadal scales, we estimate African dust deposition flux and loss frequency (LF, a ratio of deposition flux to mass loading) along the trans-Atlantic transit using the three-dimensional distributions of aerosol retrieved by spaceborne lidar (CALIOP) and radiometers (MODIS, MISR, and IASI). On the basis of a ten-year (2007-2016) and basin scale average, the amount of dust deposition into the tropical Atlantic Ocean is estimated at 136 - 222 Tg yr. The 65-83% of satellite-based estimates agree with the in-situ climatology within a factor of 2. The magnitudes of dust deposition are highest in boreal summer and lowest in fall, whereas the interannual variability as measured by the normalized standard deviation with mean is largest in spring (28-41%) and smallest (7-15%) in summer. The dust deposition displays high spatial heterogeneity, revealing that the meridional shifts of major dust deposition belts are modulated by the seasonal migration of the intertropical convergence zone (ITCZ). On the basis of the annual and basin mean, the dust LF derived from the satellite observations ranges from 0.078 to 0.100 d, which is lower than model simulations by up to factors of 2 to 5. The most efficient loss of dust occurs in winter, consistent with the higher possibility of low-altitude transported dust in southern trajectories being intercepted by rainfall associated with the ITCZ. The satellite-based estimates of dust deposition can be used to fill the geographical gaps and extend time span of in-situ measurements, study the dust-ocean interactions, and evaluate model simulations of dust processes.
矿物尘埃在海洋中的沉降为生态系统提供养分，并影响生物地球化学循环和气候。对尘埃沉降的实地观测很少，而模型模拟依赖于对尘埃过程高度参数化的表示，且约束条件很少。通过利用卫星在全球和年代尺度上的常规采样，我们利用星载激光雷达（CALIOP）和辐射计（MODIS、MISR和IASI）反演的气溶胶三维分布，估算了跨大西洋运输过程中非洲尘埃的沉降通量和损失频率（LF，沉降通量与质量负荷之比）。基于十年（2007 - 2016年）和盆地尺度的平均值，热带大西洋的尘埃沉降量估计为136 - 222太克/年。65 - 83%基于卫星的估计值与实地气候学数据在2倍的范围内相符。尘埃沉降量在北半球夏季最高，秋季最低，而以归一化标准差与平均值衡量的年际变率在春季最大（28 - 41%），夏季最小（7 - 15%）。尘埃沉降表现出高度的空间异质性，表明主要尘埃沉降带的经向移动受到热带辐合带（ITCZ）季节性迁移的调节。基于年度和盆地平均值，卫星观测得出的尘埃LF范围为0.078至0.100天，比模型模拟结果低2至5倍。尘埃最有效的损失发生在冬季，这与南部轨迹中低空传输的尘埃更有可能被与ITCZ相关的降雨拦截相一致。基于卫星的尘埃沉降估计可用于填补实地测量的地理空白、延长时间跨度，研究尘埃 - 海洋相互作用，并评估尘埃过程的模型模拟。
