This function downloads climate change data of rainfall and air temperature from NASA Earth Exchange Global Daily Downscaled Projections NEX-GDDP-CMIP6 AMES 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-CMIP6 data set 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 6 CMIP6 and across two of the four "Tier 1" greenhouse gas emissions scenarios known as Shared Socioeconomic Pathways SSPs.
NEX_GDDP_CMIP6(
Dir = "./INPUT/",
watershed = "LowerMekong.shp",
DEM = "LowerMekong_dem.tif",
start = "2060-12-1",
end = "2060-12-3",
model = "MIROC6",
type = "pr",
slice = "ssp245"
)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 6 CMIP6 (e.g., MIROC6 which is the sixth version of the Model for Interdisciplinary Research on Climate MIROC model).
A flux data type. It's value can be 'pr' for precipitation or 'tas' for air temperature.
A scenario from the Shared Socioeconomic Pathways (SSPs). It's value can be 'ssp126', 'ssp245', 'ssp370', 'ssp585', or 'historical'.
A table that includes points ID, Point file name, Lat, Long, and Elevation information formatted to be read with hydrological models and
a scalar of climate change gridded data values at each point within the study watershed in ascii format needed by hydrological model weather inputs will be 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 AMES Research Center server for NEX-GDDP-CMIP6
climate change data products at https://www.nccs.nasa.gov/services/data-collections/land-based-products/nex-gddp-cmip6. The function uses variable name ('pr') for rainfall in NEX-GDDP-CMIP6 data products and variable name ('tas') for NEX-GDDP-CMIP6 minimum ('tasmin') and maximum ('tasmax')
air temperature data products. The NEX_GDDP_CMIP6 function outputs gridded rainfall data in 'mm' and gridded air temperature (maximum and minimum) data in degrees 'C'.
NEX-GDDP-CMIP6 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 6 CMIP6 (Eyring et al. 2016)
and across the four "Tier 1" greenhouse gas emissions scenarios known as Shared Socioeconomic Pathways SSPs (O'Neil et al. 2016; Meinshausen et al. 2020). The CMIP6 GCM runs were developed in support of the Sixth Assessment Report
of the Intergovernmental Panel on Climate Change IPCC AR6. This data set includes downscaled projections from the 35 models and scenarios for which daily scenarios were produced and distributed under CMIP6. Please visit NCCS Dataportal - Datashare technical note https://www.nccs.nasa.gov/sites/default/files/NEX-GDDP-CMIP6-Tech_Note.pdf to ensure that the requested model and greenhouse gas emissions scenario (SSPs) is available on the server before you execute your run.
The Bias-Correction Spatial Disaggregation BCSD method used in generating the NEX-GDDP-CMIP6 data set 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-CMIP6 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_CMIP6 downscales the NEX-GDDP-CMIP6 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_CMIP6 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-CMIP6/ 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_CMIP6 or any other function part of the this package (NASAaccess).
start should be equal to or greater than 2015-Jan-01 for 'ssp126', 'ssp245', 'ssp370', or 'ssp585' SSPs climate scenario.
start should be equal to or greater than 1950-Jan-01 and end should be equal to or less than 2014-Dec-31 for the 'historical' GCM retrospective climate data.
Eyring, V., Bony, S., Meehl, G.A., Senior, C.A., Stevens, B., and et al., 2016. Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geoscientific Model Development, 9, 1937-1958, doi: 10.5194/gmd-9-1937-2016
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., Nicholls, Z.R.J., Lewis, J., Gidden, M.J., Vogel, E., and et al., 2020. The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500. Geoscientific Model Development, 13, 3571-3605, doi: 10.5194/gmd-13-3571-2020
Meinshausen, M., Smith, S.J., Calvin, K., Daniel, J.S., Kainuma, M.L.T., 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., Bolten, J., Srinivasan, R., 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.
O'Neill, B.C., Tebaldi, C., van Vuuren, D.P., Eyring, V., Friedlingstein, and et al., 2016. The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6. Geoscientific Model Development, 9, 3461-3482, doi: 10.5194/gmd-9-3461-2016
Thrasher, B., Maurer, E. P., McKellar, C., and P. B. Duffy, 2012. Technical Note: Bias correcting climate model simulated daily temperature extremes with quantile mapping. Hydrology and Earth System Sciences, 16(9), 3309-3314, doi:1 0.5194/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_CMIP6(Dir = "./INPUT/", watershed = "LowerMekong.shp",
DEM = "LowerMekong_dem.tif", start = "2060-12-1", end = "2060-12-3",
model = 'MIROC6', type = 'pr', slice = 'ssp245')