MODIS/Aqua L3 Value-added Aerosol Optical Depth - NRT

MODIS was launched aboard the Terra satellite on December 18, 1999 (10:30 am equator crossing time) as part of NASA's Earth Observing System (EOS) mission. MODIS with its 2330 km viewing swath width provides almost daily global coverage. It acquires data in 36 high spectral resolution bands between 0.415 to 14.235 micron with spatial resolutions of 250m(2 bands), 500m(5 bands),and 1000m (29 bands). MODIS sensor counts, calibrated radiances, geolocation products and all derived geophysical atmospheric and ocean products are archived at various DAACs and has been made available to public since April 2000. The shortname for this level-3 MODIS aerosol product is MYDAODHD. The Naval Research Laboratory and the University of North Dakota developed this value-added aerosol optical depth dataset based on MODIS Level 2 aerosol products. The MYDAODHD is a gridded product and is specifically designed for quantitative applications including data assimilation and model validation. It is available through LANCE-MODIS. It offers several enhancements over the MODIS Level 2 data on which it is based. These enhancements include stringent filtering to reduce outliers, eliminate cloud contamination, and exclude conditions where aerosol detection is likely to be inaccurate; reduction of systematic biases over land and ocean by empirical corrections; reduction of random variation in AOD values by spatial averaging; quantitative estimation of uncertainty for each AOD data point. The MxDAODHD granules are produced every six hours, and time-stamped 00:00, 06:00, 12:00, and 18:00 (all times UTC). Each granule includes MODIS observations from +/-3 hours from the timestamp (e.g. 12:00 product includes MODIS data from 09:00-15:00 UTC). Production is initiated as soon as the Level 2 inputs become available in the LANCE system.MODIS作为美国国家航空航天局（NASA）地球观测系统（Earth Observing System, EOS）任务的一部分，于1999年12月18日搭载Terra卫星发射（赤道过境时间为上午10:30）。MODIS具备2330公里的观测幅宽，可实现近乎每日的全球覆盖。它在0.415至14.235微米范围内的36个高光谱分辨率波段采集数据，空间分辨率分别为250米（2个波段）、500米（5个波段）和1000米（29个波段）。MODIS传感器计数、校准辐射率、地理定位产品及所有衍生的地球物理大气与海洋产品均存档于多个分布式活动档案中心（Distributed Active Archive Centers, DAACs），并自2000年4月起向公众开放获取。 该3级MODIS气溶胶产品的简称是MYDAODHD。美国海军研究实验室（Naval Research Laboratory）与北达科他大学（University of North Dakota）基于MODIS 2级气溶胶产品开发了此增值气溶胶光学深度数据集。MYDAODHD是一种网格产品，专为数据同化和模型验证等定量应用设计。该产品可通过LANCE-MODIS获取。相较于其基于的MODIS 2级数据，该产品具有多项增强特性：包括通过严格滤波减少异常值、消除云污染并排除气溶胶检测可能不准确的情况；通过经验校正降低陆地与海洋区域的系统偏差；通过空间平均减少气溶胶光学深度（Aerosol Optical Depth, AOD）值的随机波动；以及对每个AOD数据点进行不确定性的定量估计。 MxDAODHD颗粒产品每6小时生成一次，时间戳为00:00、06:00、12:00和18:00（均为协调世界时，Coordinated Universal Time, UTC）。每个颗粒包含时间戳前后±3小时内的MODIS观测数据（例如，12:00的产品包含09:00-15:00 UTC的MODIS数据）。一旦LANCE系统中2级输入数据可用，便立即启动产品生成。