联合国西亚经济社会委员会-使用地理信息系统分析气候变化数据培训手册（英）-2021.7-40页_22mb

Summary of the Training Manual on the Use of GIS to Analyse Climate Change Data

Core Content

This training manual provides a step-by-step guide on how to use Geographic Information Systems (GIS), specifically ESRI ArcMap, to download and analyze climate change data within the framework of the Regional Initiative for the Assessment of Climate Change Impacts on Water Resources and Socio-Economic Vulnerability in the Arab Region (RICCAR). It outlines the procedures for handling NetCDF files, creating raster layers, and performing climate data interpolation and ensemble creation.

Main Points

RICCAR Overview

• RICCAR is a joint initiative of the United Nations and the League of Arab States, launched in 2010.
• It is implemented by 11 regional and specialized organizations, including ESCWA and ACSAD.
• The initiative is supported by the Government of Sweden and the Government of the Federal Republic of Germany.
• It is coordinated under the Arab Ministerial Water Council and follows resolutions from various councils and sessions.

Climate Data Availability

• Climate data includes temperature, precipitation, and extreme event ensembles for three time periods: reference, mid-century, and end-century.
• Data is available for two climate scenarios: RCP4.5 and RCP8.5.
• The data is stored in NetCDF format and can be accessed from the Regional Knowledge Hub (RKH) and the Earth System Grid Federation (ESGF) portals.

Data Formats and Usage

• NetCDF is a multidimensional data format that supports time, latitude, and longitude dimensions.
• It is compatible with various platforms but this manual focuses on ArcMap GIS.
• The manual provides detailed steps for converting NetCDF files into usable raster layers and tables.

Key Information

NetCDF File Structure

• NetCDF files are named with a specific convention that includes:
  • Climate variable (e.g., pr for precipitation, tas for temperature)
  • CORDEX domain and spatial resolution (e.g., MNA-44 for 50 km resolution)
  • Global Climate Model (GCM) used (e.g., CNRM-CM5, EC-EARTH, GFDL-ESM2M)
  • Climate scenario (e.g., RCP4.5, RCP8.5)
  • Bias-correction method (e.g., v1-bc-dbs-wfdei)
  • Temporal resolution (e.g., day, annual, seasonal)
  • Period of the dataset (e.g., 1951-2100)
  • Seasonal representation (e.g., DJF, MAM, JJA, SON)

Creating Raster Layers from NetCDF Files

• Use the Make NetCDF Raster Layer tool to create raster layers from NetCDF files.
• Select the relevant climate variable, X dimension (longitude), and Y dimension (latitude).
• The resulting raster layer represents the first time band (e.g., 1 January for temperature and precipitation files or the first year for extreme event indices).
• Raster layers are temporarily stored in memory; users can save or export them for further analysis.

Extracting Time Slices and Ensembles

• Use the NetCDF Time Slice Export Tool to extract multiple time slices from NetCDF raster layers.
• Each time slice is stored as a separate raster file, named Band_n, where n corresponds to the day of the year or year in the dataset.
• For extreme events indices, each band represents a year (e.g., Band_1 = 1951, Band_150 = 2100).
• Users are advised to avoid mixing bias-corrected and raw RCM outputs to maintain data integrity.

Climate Data Interpolation

• The manual explains how to perform interpolation and downscaling using tools such as the Geostatistical Wizard and Resample Tool.
• Interpolation is used to create continuous surfaces from discrete data points, while downscaling involves increasing the resolution of climate data.
• Special attention is given to handling coastal areas where grid cells with less than 50% water coverage are removed during bias correction. Users are advised to use nearest neighbor interpolation or extrapolation in such cases.

Additional Tools and Processes

• Model Builder is used to automate the creation of raster layers from multiple NetCDF files.
• It allows users to define an area of interest using a shapefile and iteratively process all files in a folder.
• The process includes:
  • Creating a geodatabase
  • Clipping raster layers to the area of interest
  • Exporting the clipped rasters
  • Merging multiple raster outputs into a single file
  • Exporting data to Excel for further analysis

Recommendations

• Users should avoid mixing bias-corrected and raw RCM outputs.
• Use the Geostatistical Wizard for interpolation and the Resample Tool for data resampling.
• Export data to Excel for more detailed analysis and visualization.
• Define the area of interest using shapefiles to ensure accurate clipping and data processing.

References

• The RICCAR Arab Climate Change Assessment Report – Main Report (ESCWA, 2017)
• RICCAR Technical Note: Regional Climate Modelling and Regional Hydrological Modelling Applications in the Arab Region
• RICCAR Technical Note: Guidelines for Accessing CORDEX Regional Climate Projections

Figures and Tables

• Figure 1: Arab Domain (CORDEX-MENA Domain)
• Figure 2: 3-dimensional NetCDF array
• Figure 3: List of Multidimension Tools in ArcMap
• Figure 4: Make NetCDF Raster Layer tool
• Figure 5: Raster Layer from NetCDF file
• Figure 6: NetCDF Raster Layer properties
• Figure 7: NetCDF Raster Layer zoomed in to show gapped coastal areas
• Figure 8: NetCDF time slice export tool in process
• Figure 9: Model Builder: Add Make NetCDF Raster Layer
• Figure 10: Model Builder: Iterate files
• Figure 11: Model Builder: Create variable as folder
• Figure 12: Enter data into Make NetCDF Raster Layer
• Figure 13: Model Builder: Perform process on all files in folder
• Figure 14: Model Builder: Add variable as workspace and create a geodatabase
• Figure 15: Model Builder: Clip NetCDF rasters to area of interest
• Figure 16: Model Builder: Clip rasters
• Figure 17: Model Builder: Add clipped rasters to display
• Figure 18: Model Builder: Clip NetCDF rasters to area of interest result
• Figure 19: Multiband raster layer properties
• Figure 20: Multiband raster files in ArcCatalog
• Figure 21: Grid system for nlat and non
• Figure 22: Make NetCDF Table View tool
• Figure 23: Make NetCDF Table View result
• Figure 24: Model Builder: MakeNetCDFTableViewinitialsteps
• Figure 25: Model Builder: MakeNetCDFTableViewenteringdata
• Figure 26: Model Builder: MakeNetCDFTableViewTabletoTable
• Figure 27: Model Builder: Enter data into Table to Table
• Figure 28: Model Builder: View output in file folder and copy first table
• Figure 29: Model Builder: Merge output into single table
• Figure 30: Model Builder: Enter data into Append tool
• Figure 31: Model Builder: Table to Excel tool
• Figure 32: Model Builder: Enter data into Table to Excel tool
• Figure 33: Model Builder: MakeNetCDFTableViewExceloutput
• Figure 34: Cell Statistics tool
• Figure 35: Raster calculator
• Figure 36: Resample tool
• Figure 37: Option to activate Extensions in ArcMap
• Figure 38: Geostatistical Wizard tool
• Figure 39: Example of IDW interpolation result

Tables

• Table 1: Precipitation and temperature regional climate modelling outputs
• Table 2: Extreme temperature indices climate modelling outputs
• Table 3: Extreme precipitation indices climate modelling outputs

The manual provides a comprehensive guide to the use of GIS for climate change data analysis, emphasizing the importance of proper data handling, processing, and visualization. It is an essential resource for researchers and institutions working on climate change impact assessments in the Arab Region.