Japan Brief Description & Validation Report Dec. 16th, 2020 (ver. 3.0) Today’s Earth Developers Group Copyright 2018, All rights reserved. TABLE OF CONTENTS 1. What is “Today’s Earth - Japan”? .................................................................................... 1 2. System Configuration and Calculation Flow ................................................................... 2 3. Data and File Naming Conventions .................................................................................. 5 4. Validation Results ............................................................................................................. 6 4.1. Snow Amount (GLSNW) .................................................................................................... 6 4.2. Soil Moisture (GLW) .......................................................................................................... 8 4.3. River Discharge (OUTFLW) ............................................................................................. 11 4.4. Summary of the Validation ............................................................................................... 13 5. Terms of Use .................................................................................................................... 15 5.1. Site Policy ....................................................................................................................... 15 5.2. User Registration ............................................................................................................. 15 5.3. Deletion of User Registration ........................................................................................... 15 5.4. Protection of Personal Information & Handling of Personal Information ........................... 15 5.5. Management of Account and Password ........................................................................... 15 5.6. Ownership of Data etc. .................................................................................................... 15 5.7. Change of the Service ..................................................................................................... 16 5.8. Termination of the Service ............................................................................................... 16 5.9. How to Cite ...................................................................................................................... 16 5.10.Disclaimer ....................................................................................................................... 16 5.11. Contact Information ......................................................................................................... 16 References .................................................................................................................................. 17 Appendix I: Variable List of Today’s Earth ................................................................................ 18 Appendix II: Member List of TE Developers Group .................................................................. 20 1. What is “Today’s Earth - Japan”? “Today’s Earth” (hereafter called “TE”) is JAXA's terrestrial hydrological simulation system. The system derives land surface and river conditions from numerical calculations according to the ever-changing weather conditions and provides the results as data and images. “Today’s Earth - Japan” (hereafter called “TE-Japan”) is the regional version of TE, which enables us to see the detailed land surface state of Japan (see Figure 1 for the comparison with TE-Global). Since the target of the TE-Japan is to produce and evaluate long-term high resolution land water cycle data set to calculate risk indices of water hazards, we use MSM- GPV (JMA’s Meso-Scale Model-Grid Point Value) atmospheric analysis data as forcing data of baseline experiment. Furthermore, we are going to utilize satellite data sets developed by JAXA/EORC to replace some input parameters of MSM ver. rainfall from the Global Satellite Mapping of Precipitation (GSMaP) and solar radiation from Himawari satellite provided by the JAXA Himawari Monitor system are going to be used for satellite version in near future. The TE developers group consists of the researchers in Japan Aerospace Exploration Agency (JAXA) Earth Observation Research Center (EORC), The University of Tokyo (UT), and Remote Sensing Technology Center of Japan (RESTEC). Detailed member list is attached at the end of this document. Figure 1. Comparison between simulated images of river discharge by TE-Global (0.25-deg lat/lon) and TE-Japan (1/60-deg lat/lon) 1 2. System Configuration and Calculation Flow The TE system consists of land surface model MATSIRO[1] (Minimal Advanced Treatments of Surface Interaction and Runoff) version5[2] and river routing model CaMa-Flood[3] (Catchment-based Macro-scale Floodplain). Table 1 and 2 describe the basic information of TE-Japan. Figure 2 shows the schematic procedure of TE-Japan system. By giving forcing of surface meteorological parameters, MATSIRO simulates the water and energy interactions between a land surface with a vegetation canopy and atmosphere. The surface runoff and baseflow were calculated independently using Horton flow and the advanced application in TOPMODEL[4], respectively. Based on the calculated runoff amount, CaMa-Flood enables hydrodynamic simulation with floodplain on a global scale. The model solves the local inertial equation[5], considering a rectangular river channel and trapezium flood plain storage, and represents flood plain dynamics assuming that the elevation profile of the floodplain monotonically increases in each pixel. TE not only visualizes and provides data on these geophysical quantities, but also translates them into user-friendly risk indicators such as return periods (i.e. an event that occurs about once every x years) and Mahalanobis distances (i.e. how rare an event is). Table 1. TE-Japan components 1/60° Land Surface Model Horizontal south west lat. = 24° [1][2] resolution south west lon. = 123° MATSIRO [Nx, Ny]=[1500, 1320] (Minimal Advanced Treatments of Surface Interaction and Runoff) Temporal hourly, daily, monthly resolution 1/60° River Routing Model Horizontal south west lat. = 24° resolution south west lon. = 123° [3] CaMa-Flood [Nx, Ny]=[1500, 1320] (Catchment-based Macro-scale Floodplain) Temporal hourly, daily, monthly resolution 2 Table 2. TE-Global experiments Name MSM/GPV ver. Period 2007-present Forcing rainfall M Data*1 snowfall M eastward wind M northward wind M surface air temperature M specific humidity M surface shortwave radiation M (downward) surface longwave radiation M (downward) surface air pressure M Data distribution Latency*2 Realtime 1. M: MSM-GPV[6] 2. MSM-GPV forecast data is used to cover the data latency. To distinguish the data using forecast, users are requested to check “Initial_date” described in global_attributes of netCDF data(If the difference between “initial_date” and the date of the file name is within 3 hours, the data is analysis value.). The item of initial_date is included in the data after March 1, 2020. Anything before that will be the analysis value. 3 Figure 2. Schematic figure of TE-Japan system. 4 3. Data and File Naming Conventions The naming conventions for the provided data files are shown below. ① Target Area (3 characters) e.g.) “JPN” for TE-Japan ② Horizontal Resolution (2 digits + 1character) e.g.) “01M” for 1min. lat/lon deg., “15S” for 15 sec. lat/lon deg. ③ Experiment Name (3 characters） e.g.) “MSM” for MSM/GPV ver. (see Table 2.) ④ Date & Time (UTC） e.g.) “H2020010100” for hourly data of 1st of July 0Z in 2020 “D20200101” for daily data of 1st of July in 2020 “M202001” for monthly data of July in 2020 ⑤ Item Name (See Appendix I) 5 4. Validation Results In order to verify the performance of the TE-Japan products, we had validations for 3 variables: snow amount and soil moisture from MATSIRO, and river discharge from CaMa- Flood. For each variable, we compared the results of TE-Japan and observation data and made some statistical comparison between them. 4.1. Snow Amount (GLSNW) First, we investigated the general characteristics of the results of snow amount. AMeDAS[7] (Automated Meteorological Data Acquisition System) observation of snow depth by JMA (Japan Meteorological Agency) is utilized to validate the TE simulation. Since TE simulates snow amount as a Snow Water Equivalent (SWE) [kg/m2], direct comparison with the AMeDAS snow depth will not be recommended. Here we used the method introduced by Sturm et al. (2010)[8] to convert snow depth to SWE by calculating snow density as a function of snow depth and its aging time. As shown in Figure 3, we picked up 316 AMeDAS observation sites that have snow depth observation from 2011/1/1 to 2015/12/31 in common. Figure 4 is a scatter density diagram during that period, showing the relation between TE-Japan SWE estimates (y-axis) and in-situ SWE converted from observed snow depth (x-axis). Overall, TE-Japan estimates shows good correlation with the in-situ SWE. Looking at the results by each validation site, we found over/underestimation at some sites, however. Aomori site in Figure 4(d) is one example where there is significant underestimation. This can be partly explained by the over/underestimation and/or misalignment of forcing data itself, since the time series of the SWE and snowfall (model forcing) in Figure 5 are in good correspondence, indicating that TE-Japan has the capacity to estimates