ECMWF GloFAS - Harvey+Irma Flood Area Grids

These datasets were obtained from ECMWF/GloFAS on November 13, 2017, to include the flood forecast (area grid) for Hurricanes Harvey and Irma in the USA from August 15 - September 15, 2017. These are contained in netCDF files, one per day.

Note that while folders and files may have the words "areagrid_for_Harvey" in the name, all the data here are for the southeast USA, encompassing both Harvey and Irma impact areas.

Dataset variables:
- dis = forecasted discharge (for all forecast step 1+30 as initial value and 30 daily average values, with ensemble members as 1+50 where the first is the so-called control member and the 50 perturbed members)
- ldd = local drainage direction within routing model
- ups = upstream area of each point within routing model
- rl2,rl5,rl20 = forecast exceedance thresholds for 2-, 5- and 20-year return period flows, based on gumbel distribution from ERA-interim land reanalysis driven through the lisflood routing.

Models used (see [1] for further details):
- Hydrology: River discharge is simulated by the Lisflood hydrological model (van der Knijff et al., 2010) for the flow routing in the river network and the groundwater mass balance. The model is set up on global coverage with horizontal grid resolution of 0.1° (about 10 km in mid-latitude regions) and daily time step for input/output data.
- Meteorology: To set up a forecasting and warning system that runs on a daily basis with global coverage, initial conditions and input forcing data must be provided seamlessly to every point within the domain. To this end, two products are used. The first consists of operational ensemble forecasts of near-surface meteorological parameters. The second is a long-term dataset consistent with daily forecasts, used to derive a reference climatology.

Suggestions for usage:
- Selected software: ArcGIS or QGIS
- Select dis for example, then any of the bands (51*31 in total), then set the range manually to 0-1000 or something like that.

Agency:
GloFAS [1]
From its public website: "The Global Flood Awareness System (GloFAS), jointly developed by the European Commission and the European Centre for Medium-Range Weather Forecasts (ECMWF), is independent of administrative and political boundaries. It couples state-of-the art weather forecasts with a hydrological model and with its continental scale set-up it provides downstream countries with information on upstream river conditions as well as continental and global overviews. GloFAS produces daily flood forecasts in a pre-operational manner since June 2011."

References
[1] GloFAS home page [http://www.globalfloods.eu/]

本数据集于2017年11月13日从欧洲中期天气预报中心（ECMWF）/全球洪水预警系统（GloFAS）获取，涵盖2017年8月15日至9月15日期间美国哈维飓风与艾尔玛飓风对应的洪水预报（区域网格）数据。数据以网络通用数据格式（netCDF）存储，每日对应一个文件。

需注意：尽管文件夹与文件名中可能包含"areagrid_for_Harvey"字样，但本数据集所有数据均覆盖美国东南部区域，涵盖哈维飓风与艾尔玛飓风的影响范围。

数据集变量如下：
- dis：预报流量（涵盖所有1至30个预报步长作为初始值，以及30个日平均值；集合成员共1+50个，其中第一个为所谓的控制成员，其余50个为扰动成员）
- ldd：汇流模型内的局部排水方向
- ups：汇流模型内各点位的上游集水面积
- rl2、rl5、rl20：对应2年一遇、5年一遇、20年一遇流量的预报超越阈值，该阈值基于通过Lisflood汇流模型驱动的ERA-Interim陆面再分析数据的耿贝尔分布计算得到。

所用模型（详细信息参见[1]）：
- 水文模型：河川径流由Lisflood水文模型（van der Knijff等，2010）模拟，用于河网汇流与地下水质量平衡计算。该模型采用全球覆盖范围设置，水平网格分辨率为0.1°（中纬度区域约为10 km），输入/输出数据的时间步长为日尺度。
- 气象数据：为搭建一套可每日运行的全球覆盖预报预警系统，需为域内所有点位无缝提供初始条件与输入强迫数据。为此采用两类数据产品：第一类为近地面气象参数的业务化集合预报；第二类为与每日预报一致的长期数据集，用于推导参考气候学特征。

使用建议：
- 推荐软件：ArcGIS或QGIS
- 以dis变量为例，选择任意波段（总计51×31个波段）后，可手动将数值范围设置为0-1000或类似区间。

数据提供机构：
GloFAS [1]
其官方网站表述如下：全球洪水预警系统（GloFAS）由欧盟委员会与欧洲中期天气预报中心（ECMWF）联合开发，不受行政与政治边界限制。该系统将先进的天气预报与水文模型相结合，凭借其大陆级别的覆盖范围，可为下游国家提供上游河流水情信息，以及大陆与全球尺度的水情概览。自2011年6月起，GloFAS以准业务化方式每日生成洪水预报。

参考文献
[1] GloFAS官方主页 [http://www.globalfloods.eu/]