MODIS/Aqua Calibrated Radiances 5-Min L1B Swath 1km - NRT

The MODIS Level 1B Near Real Time (NRT) data set contains calibrated and geolocated at-aperture radiances for 36 discrete bands located in the 0.4 to 14.4 micron region of electromagentic spectrum. These data are generated from the MODIS Level 1A scans of raw radiance and in the process converted to geophysical units of W/(m^2 um sr). In addition, the Earth Bi-directional Reflectance Distribution Function (BRDF) may be determined for the solar reflective bands (1-19, 26) through knowledge of the solar irradiance (e.g., determined from MODIS solar diffuser data, and from the target illumination geometry). Additional data are provided including quality flags, error estimates and calibration data. Visible, shortwave infrared, and near infrared measurements are only made during the daytime, while radiances for the thermal infrared region (bands 20-25, 27-36) are measured continuously. Channel locations for MODIS are as follows: Band Center Wavelength (um) Primary Use---- ---------------------- -----------1 0.620 - 0.670 Land/Cloud Boundaries2 0.841 - 0.876 Land/Cloud Boundaries3 0.459 - 0.479 Land/Cloud Properties4 0.545 - 0.565 Land/Cloud Properties5 1.230 - 1.250 Land/Cloud Properties6 1.628 - 1.652 Land/Cloud Properties7 2.105 - 2.155 Land/Cloud Properties8 0.405 - 0.420 Ocean Color/Phytoplankton9 0.438 - 0.448 Ocean Color/Phytoplankton10 0.483 - 0.493 Ocean Color/Phytoplankton11 0.526 - 0.536 Ocean Color/Phytoplankton12 0.546 - 0.556 Ocean Color/Phytoplankton13 0.662 - 0.672 Ocean Color/Phytoplankton14 0.673 - 0.683 Ocean Color/Phytoplankton15 0.743 - 0.753 Ocean Color/Phytoplankton16 0.862 - 0.877 Ocean Color/Phytoplankton17 0.890 - 0.920 Atmospheric Water Vapor18 0.931 - 0.941 Atmospheric Water Vapor19 0.915 - 0.965 Atmospheric Water Vapor20 3.660 - 3.840 Surface/Cloud Temperature21 3.929 - 3.989 Surface/Cloud Temperature22 3.929 - 3.989 Surface/Cloud Temperature23 4.020 - 4.080 Surface/Cloud Temperature24 4.433 - 4.498 Atmospheric Temperature25 4.482 - 4.549 Atmospheric Temperature26 1.360 - 1.390 Cirrus Clouds27 6.535 - 6.895 Water Vapor Profile28 7.175 - 7.475 Water Vapor Profile29 8.400 - 8.700 Water Vapor Profile30 9.580 - 9.880 Ozone Overburden31 10.780 - 11.280 Surface/Cloud Temperature32 11.770 - 12.270 Surface/Cloud Temperature33 13.185 - 13.485 Cloud Top Altitude34 13.485 - 13.785 Cloud Top Altitude35 13.785 - 14.085 Cloud Top Altitude36 14.085 - 14.385 Cloud Top Altitude Channels 1 and 2 have 250 m resolution, channels 3 through 7 have 500m resolution, and the rest have 1 km resolution. However, for the MODIS L1B 1 km product, the 250 m and 500 m band radiance data and their associated uncertainties have been aggregated to 1km resolution. Thus the entire channel data set is referenced to the same spatial and geolocation scales. Separate L1B products are available for the 250 m channels (MYD02QKM) and 500 m channels (MYD02HKM) that preserve the original resolution of the data. Spatial resolution for pixels at nadir is 1 km, degrading to 4.8 km in the along-scan direction at the scan extremes. However, thanks to the overlapping of consecutive swaths and respectively pixels there, the resulting resolution at the scan extremes is about 2km. A 55 degree scanning pattern at the EOS orbit of 705 km results in a 2330km orbital swath width and provides global coverage every one to two days. A single MODIS Level 1B granule will nominally contain a scene built from 203 scans (or swaths) sampled 1354 times in the cross-track direction, corresponding to approximately 5 minutes worth of data. Since an individual MODIS scan (or swath) will contain 10 along-track spatial elements, the scene will be composed of (1354 x 2030) pixels, resulting in a spatial coverage of (2330 km x 2030 km). Due to the MODIS scan geometry, there will be increasing overlap occurring beyond about 25 degrees scan angle. To summarize, the MODIS L1B 1 km data product consists of: 1. Calibrated radiances and uncertainties for (2) 250 m reflected solar bands aggregated to 1km resolution 2. Calibrated radiances and uncertainties for (5) 500 m reflected solar bands aggregated to 1 km resolution 3. Calibrated radiances and uncertainties for (13) 1 km reflected solar bands and (16) infrared emissive bands 4. Geolocation subsampled at every 5th pixel across and along track 5. Satellite and solar angles subsampled at the above frequency 6. Comprehensive set of file-level metadata summarizing the spatial, temporal and parameter attributes of the data, as well as auxiliary information pertaining to instrument status and data quality characterization. The MODIS L1B data are stored in the Earth Observing System Hierarchical Data Format (HDF-EOS) which is an extension of HDF as developed by the National Center for Supercomputer Applications (NCSA) at the University of Illinois. A typical file size will be approximately 260 MB. Environmental information derived from MODIS L1B measurements will offer a comprehensive and unprecedented look at terrestrial, atmospheric, and ocean phenomenology for a wide and diverse community of users throughout the world. The Shortname for this product is MYD021KM

MODIS近实时一级B数据集包含位于电磁频谱0.4至14.4微米区域内的36个离散波段的校准和地理定位入射辐射亮度。这些数据源自MODIS一级A扫描的原始辐射亮度，并在转换过程中转换为地物理单位W/(m^2 um sr)。此外，通过了解太阳辐照度（例如，从MODIS太阳漫射器数据以及目标照明几何形状中确定），可以确定太阳反射波段（1-19，26）的地球双向反射分布函数（BRDF）。数据还包括质量标志、误差估计和校准数据。仅在白天进行可见光、短波红外和近红外测量，而热红外区域（波段20-25，27-36）的辐射亮度则持续测量。MODIS的通道位置如下：

波段 中心波长（um） 主要用途---- ---------------------- -----------
1 0.620 - 0.670 陆地/云边界2 0.841 - 0.876 陆地/云边界3 0.459 - 0.479 陆地/云特性4 0.545 - 0.565 陆地/云特性5 1.230 - 1.250 陆地/云特性6 1.628 - 1.652 陆地/云特性7 2.105 - 2.155 陆地/云特性8 0.405 - 0.420 海洋颜色/浮游植物9 0.438 - 0.448 海洋颜色/浮游植物10 0.483 - 0.493 海洋颜色/浮游植物11 0.526 - 0.536 海洋颜色/浮游植物12 0.546 - 0.556 海洋颜色/浮游植物13 0.662 - 0.672 海洋颜色/浮游植物14 0.673 - 0.683 海洋颜色/浮游植物15 0.743 - 0.753 海洋颜色/浮游植物16 0.862 - 0.877 海洋颜色/浮游植物17 0.890 - 0.920 大气水汽18 0.931 - 0.941 大气水汽19 0.915 - 0.965 大气水汽20 3.660 - 3.840 表面/云温度21 3.929 - 3.989 表面/云温度22 3.929 - 3.989 表面/云温度23 4.020 - 4.080 表面/云温度24 4.433 - 4.498 大气温度25 4.482 - 4.549 大气温度26 1.360 - 1.390 高层云27 6.535 - 6.895 水汽垂直分布28 7.175 - 7.475 水汽垂直分布29 8.400 - 8.700 水汽垂直分布30 9.580 - 9.880 臭氧层31 10.780 - 11.280 表面/云温度32 11.770 - 12.270 表面/云温度33 13.185 - 13.485 云顶高度34 13.485 - 13.785 云顶高度35 13.785 - 14.085 云顶高度36 14.085 - 14.385 云顶高度

通道1和2的分辨率为250米，通道3至7的分辨率为500米，其余通道的分辨率为1公里。然而，对于MODIS L1B 1公里产品，250米和500米波段辐射亮度及其相关不确定性已汇总至1公里分辨率。因此，整个通道数据集均参照相同的空间和地理定位尺度。可单独获取针对250米通道（MYD02QKM）和500米通道（MYD02HKM）的L1B产品，以保留数据的原始分辨率。下行视角像素的空间分辨率为1公里，在扫描极端方向上降至4.8公里。然而，由于连续条带和相应像素的重叠，扫描极端方向上的分辨率约为2公里。在地球观测系统（EOS）轨道上55度的扫描模式，在705公里的轨道高度上产生2330公里的轨道条带宽度，并能每隔一至两天实现全球覆盖。单个MODIS一级B数据块通常包含由203个扫描（或条带）组成的一个场景，这些扫描在横向上采样1354次，相当于大约5分钟的数据。由于单个MODIS扫描（或条带）将包含10个沿轨道的空间元素，因此场景将由（1354 x 2030）个像素组成，从而实现（2330 km x 2030 km）的空间覆盖。由于MODIS扫描几何形状，在约25度扫描角之外将出现越来越大的重叠。总之，MODIS L1B 1公里数据产品包括：

1. 聚合至1公里分辨率的（2）个250米反射太阳波段和（5）个500米反射太阳波段的校准辐射亮度和不确定性
2. 聚合至1公里分辨率的（13）个1公里反射太阳波段和（16）个红外辐射波段的校准辐射亮度和不确定性
3. 在横向上和沿轨道方向上每5个像素进行地理定位子采样
4. 在上述频率下进行卫星和太阳角度的子采样
5. 综合的文件级元数据，总结数据的空间、时间和参数属性，以及有关仪器状态和数据质量表征的辅助信息。

MODIS L1B数据存储在地球观测系统分层数据格式（HDF-EOS）中，该格式是美国伊利诺伊大学国家超级计算应用中心（NCSA）开发的HDF的扩展。典型文件大小约为260 MB。从MODIS L1B测量中获得的环境信息将为全球范围内广泛而多样的用户群体提供对陆地、大气和海洋现象的全面且前所未有的观察。本产品的简称是MYD021KM。