Water States - Corrected Reflectance (VIIRS / Suomi-NPP)

Overview and Intended Use This visualization represents a "false color" band combination (Red = M3, Green = I3, Blue = M11) of data collected by the VIIRS instrument on the joint NASA/NOAA Suomi-NPP satellite. The imagery is most useful for distinguishing water in its various states (e.g. liquid, ice, and snow). For example, clouds over snow, ice cloud versus water cloud; or floods from dense vegetation. At its highest resolution, this visualization represents the underlying data scaled to a resolution of 250m per pixel at the equator. The VIIRS Corrected Reflectance product retains visible aerosols for a natural-looking visualization, though gross atmospheric effects (e.g. Rayleigh scattering) have been removed. The following guidelines will aid in understanding this visualization. See here for additional information on how this "false color" band combination highlights these physical characteristics of the Earth. Thick ice and snow appear a vivid red (or dark pink), while ice crystals in clouds will appear pinkish. Vegetation will appear green. Naturally bare soil, like a desert, will appear bright cyan. Liquid water on the ground will appear very dark, while water droplets in clouds will appear white. Sediments in water will appear dark red. Multi-Spectral Bands The following table lists the VIIRS bands that are utilized to create this visualization. See here for a full description of all VIIRS bands. Band Description Wavelength (µm) Resolution (m) I3 Shortwave IR (Red) 1.58 - 1.64 375 M3 Visible (reflective) 0.478 - 0.488 750 M11 Shortwave IR 2.23 - 2.28 750 Temporal Coverage and Limitations of Use By default, this layer will display the imagery currently available for today’s date. The update frequency of the imagery is a "daily composite" that is assembled from hundreds of individual data files. When viewing imagery for “today,” you may notice that only a portion of the map has imagery. This is because the visualization is continually updated as the satellite collects more data. To view imagery over time, you can update the layer properties to enable time animation and configure time settings. The current version of this layer is available from present back to November 24th, 2015. In the coming months, this will be extended to the start of the mission (October 28th, 2011). Source: NASA Global Imagery Browse Services (GIBS), NASA Worldview, & NASA LANCE This visualization is provided through the NASA Global Imagery Browse Services (GIBS), which are a set of standard services to deliver global, full-resolution satellite imagery for hundreds of NASA Earth science datasets and science parameters. Through its services, and the NASA Worldview client, GIBS enables interactive exploration of NASA's Earth imagery for a broad range of users. The data and imagery are generated within 3 hours of acquisition through the NASA LANCE capability. Esri and NASA Collaborative Services This visualization is made available through an ArcGIS image service hosted on Esri servers and facilitates access to a NASA GIBS service endpoint. For each image service request, the Esri server issues multiple requests to the GIBS service, processes and assembles the responses, and returns a proper mosaic image to the user. Processing occurs on-the-fly for each and every request to ensure that any update to the GIBS imagery is immediately available to the user. As such, availability of this visualization is dependent on both the Esri and the NASA GIBS services.概述及预期用途 本可视化图像采用NASA与NOAA联合研制的Suomi-NPP卫星上搭载的可见光红外成像辐射仪（Visible Infrared Imaging Radiometer Suite, VIIRS）所采集的数据，采用假彩色（false color）波段组合方案（红色通道对应M3波段、绿色通道对应I3波段、蓝色通道对应M11波段）。该影像在区分不同物态水体（如液态水、海冰与积雪）方面具备优异的区分能力，例如可用于区分积雪上空云层、冰云与水云，或是区分洪涝区域与茂密植被。 本可视化图像的最高分辨率等效于赤道地区每像素250米的原始数据采样分辨率。VIIRS校正反射率产品保留了可见气溶胶信息以呈现自然视觉效果，同时已去除瑞利散射等显著大气干扰效应。下文将提供本可视化图像的解读指南，可点击此处查阅该假彩色波段组合如何凸显地球物理特征的更多细节。 厚层冰盖与积雪呈鲜亮红色（或深粉色），云层中的冰晶则呈淡粉色；植被呈现绿色；自然裸露的土壤（如沙漠）呈亮青色；地表液态水呈深暗色，云层中的水滴则呈白色；水体中的沉积物呈暗红色。 多光谱波段 下表列出了用于生成本可视化图像的VIIRS波段，完整VIIRS波段说明可点击此处查阅。 | 波段编号 | 波段描述 | 波长范围（μm） | 空间分辨率（m） | |---------|---------|--------------|----------------| | I3 | 短波红外（红色通道） | 1.58 - 1.64 | 375 | | M3 | 可见光（反射型） | 0.478 - 0.488 | 750 | | M11 | 短波红外 | 2.23 - 2.28 | 750 | 时间覆盖范围与使用限制 默认情况下，本图层将显示当前日期下可用的影像数据。该影像采用每日合成更新机制，由数百份独立数据文件拼接生成。当查看“今日”影像时，可能仅能看到部分地图区域覆盖影像，这是因为卫星持续采集数据，可视化图像也会随新数据的获取而逐步更新。若需查看历史时段的影像，可通过更新图层属性启用时间动画并配置时间参数。 当前版本的本图层可回溯至2015年11月24日获取，未来数月内将扩展至任务启动之初（2011年10月28日）。 数据来源：NASA全球影像浏览服务（NASA Global Imagery Browse Services, GIBS）、NASA Worldview及NASA LANCE 本可视化图像通过NASA全球影像浏览服务（GIBS）提供，该服务提供标准化接口，可交付数百套NASA地球科学数据集与科学参数对应的全球全分辨率卫星影像。通过其服务接口与NASA Worldview客户端，GIBS可为广泛用户群体提供NASA地球影像的交互式浏览功能。 依托NASA LANCE技术，数据与影像可在采集后3小时内完成生成。 Esri与NASA联合服务 本可视化图像通过部署于Esri服务器的ArcGIS影像服务提供，可对接NASA GIBS服务端点。每一次影像服务请求，Esri服务器都会向GIBS服务发起多组请求，对响应结果进行处理与拼接后，向用户返回完整的镶嵌影像。所有请求均采用实时在线处理模式，以确保GIBS影像的任何更新均可立即对用户可用。因此，本可视化图像的可用性同时依赖于Esri服务与NASA GIBS服务。