This function downloads climate change data of rainfall and air temperature from NASA Earth Exchange Global Daily Downscaled Projections NEX-GDDP GSFC servers, extracts data from grids within a specified watershed shapefile, and then generates tables in a format that any hydrological model requires for rainfall or air temperature data input. The function also generates the climate stations file input (file with columns: ID, File NAME, LAT, LONG, and ELEVATION) for those selected climatological grids that fall within the specified watershed. The NASA Earth Exchange Global Daily Downscaled Projections NEX-GDDP dataset is comprised of downscaled climate scenarios for the globe that are derived from the General Circulation Model GCM runs conducted under the Coupled Model Intercomparison Project Phase 5 CMIP5 and across two of the four greenhouse gas emissions scenarios known as Representative Concentration Pathways RCPs (rcp45, rcp85).
NEX_GDDP_CMIP5(
Dir = "./INPUT/",
watershed = "LowerMekong.shp",
DEM = "LowerMekong_dem.tif",
start = "2060-12-1",
end = "2060-12-3",
model = "IPSL-CM5A-MR",
type = "pr",
slice = "rcp85"
)A directory name to store gridded climate data and stations files.
A study watershed shapefile spatially describing polygon(s) in a geographic projection crs ='+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs'.
A study watershed digital elevation model raster in a geographic projection crs ='+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs'.
Beginning date for gridded climate data.
Ending date for gridded climate data.
A climate modeling center and name from the World Climate Research Programme WCRP global climate projections through the Coupled Model Intercomparison Project 5 CMIP5 (e.g., IPSL-CM5A-MR which is Institut Pierre-Simon Laplace CM5A-MR model).
A flux data type. It's value can be 'pr' for precipitation or 'tas' for air temperature.
A scenario from the Representative Concentration Pathways. It's value can be 'rcp45' , 'rcp85', or 'historical'.
A table that includes points ID, Point file name, Lat, Long, and Elevation information, and
a scalar of climate change gridded data values at each point within the study watershed in ascii format stored at Dir.
A user should visit https://disc.gsfc.nasa.gov/information/documents Data Access document to register with the Earth Observing System Data and Information System (NASA Earthdata) and then authorize NASA GESDISC Data Access to successfully work with this function. The function accesses NASA Goddard Space Flight Center server for IMERG remote sensing data products at (https://gpm1.gesdisc.eosdis.nasa.gov/data/GPM_L3/GPM_3IMERGDF.06/), and NASA Goddard Space Flight Center server for NEX-GDDP climate change data products at (https://www.nccs.nasa.gov/services/climate-data-services). The function uses variable name ('pr') for rainfall in NEX-GDDP data products and variable name ('tas') for NEX-GDDP minimum ('tasmin') and maximum ('tasmax') air temperature data products. The NEX-GDDP function outputs gridded rainfall data in 'mm' and gridded air temperature (maximum and minimum) data in degrees 'C'.
NEX-GDDP dataset is comprised of downscaled climate scenarios for the globe that are derived from the General Circulation Model GCM runs conducted under the Coupled Model Intercomparison Project Phase 5 CMIP5 (Taylor et al. 2012) and across two of the four greenhouse gas emissions scenarios known as Representative Concentration Pathways RCPs (Meinshausen et al. 2011). The CMIP5 GCM runs were developed in support of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change IPCC AR5. This dataset includes downscaled projections from the 21 models and scenarios for which daily scenarios were produced and distributed under CMIP5.
The Bias-Correction Spatial Disaggregation BCSD method used in generating the NEX-GDDP dataset is a statistical downscaling algorithm specifically developed to address the current limitations of the global GCM outputs (Wood et al. 2002; Wood et al. 2004; Maurer et al. 2008; Thrasher et al. 2012). The NEX-GDDP climate projections is downscaled at a spatial resolution of 0.25 degrees x 0.25 degrees (approximately 25 km x 25 km). The NEX_GDDP_CMIP5 downscales the NEX-GDDP data to grid points of 0.1 degrees x 0.1 degrees following nearest point methods described by Mohammed et al. (2018).
The NEX_GDDP_CMIP5 function relies on 'curl' tool to transfer data from NASA servers to a user machine, using HTTPS supported protocol. The 'curl' command embedded in this function to fetch precipitation/air temperature NEX-GDDP/ netcdf annual global files is designed to work seamlessly by appending appropriate logging information to the ".netrc" file and the cookies file ".urs_cookies". The ".netrc" and ".urs_cookies" files need to be stored at local directory before running any function in this package. Instructions on creating the ".netrc" and ".urs_cookies" files can be accessed at https://wiki.earthdata.nasa.gov/display/EL/How+To+Access+Data+With+cURL+And+Wget. It is imperative to say here that a user machine should have 'curl' installed as a prerequisite to run NEX_GDDP_CMIP5 or any other function part of the this package (NASAaccess).
start should be equal to or greater than 2006-Jan-01 for 'rcp45' or 'rcp85' RCP climate scenario.
start should be equal to or greater than 1950-Jan-01 and end should be equal to or less than 2005-Dec-31 for the 'historical' GCM retrospective climate data.
Maurer, E. P. and Hidalgo, H. G., 2008: Utility of daily vs. monthly large-scale climate data: an intercomparison of two statistical downscaling methods. Hydrology and Earth System Sciences, 12, 551-563, doi:10.5194/hess-12-551-2008.
Meinshausen, M. S.J. Smith, K. Calvin, J.S. Daniel, M.L.T. Kainuma, and et al., 2011: The RCP greenhouse gas concentrations and their extensions from 1765 to 2300. Climatic Change, 109, 213-241, doi:10.1007/s10584-011-0156-z.
Mohammed, I.N., J. Bolten, R. Srinivasan, and V. Lakshmi, 2018: Improved Hydrological Decision Support System for the Lower Mekong River Basin Using Satellite-Based Earth Observations. Remote Sensing, 10, 885, doi:10.3390/rs10060885.
Taylor, Karl E., Ronald J. Stouffer, Gerald A. Meehl, 2012: An Overview of CMIP5 and the Experiment Design. Bull. Amer. Meteor. Soc., 93, 485–498, doi:10.1175/BAMS-D-11-00094.1.
Thrasher, B., Maurer, E. P., McKellar, C., & Duffy, P. B., 2012: Technical Note: Bias correcting climate model simulated daily temperature extremes with quantile mapping. Hydrology and Earth System Sciences, 16(9), 3309-3314, doi:10.5194/hess-16-3309-2012
Wood, A.W., E.P. Maurer, A. Kumar, and D.P. Lettenmaier, 2002: Long-range experimental hydrologic forecasting for the eastern United States. J. Geophysical Research-Atmospheres, 107, 4429, doi:10.1029/2001JD000659.
Wood, A.W., L.R. Leung, V. Sridhar, and D.P. Lettenmaier, 2004: Hydrologic implications of dynamical and statistical approaches to downscaling climate model outputs. Climatic Change, 15,189-216, doi: 10.1023/B:CLIM.0000013685.99609.9e
#Lower Mekong basin example
if (FALSE) NEX_GDDP_CMIP5(Dir = "./INPUT/", watershed = "LowerMekong.shp",
DEM = "LowerMekong_dem.tif", start = "2060-12-1", end = "2060-12-3",
model = 'IPSL-CM5A-MR', type = 'pr', slice = 'rcp85')