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Get MERRA-2 aerosol diagnostics data

Source: R/merra.R
get_merra_data.Rd

Total and component (Dust, OC, BC, SS, SO4) surface PM2.5 concentrations from the MERRA-2 M2T1NXAER v5.12.4 product. Because installing MERRA-2 data takes a long time, "pre-compiled" data binaries for each year are available as pre-releases specific to MERRA data on GitHub.

Usage

get_merra_data(x, dates, merra_release = "merra-2025-01-02")

install_merra_data(
  merra_year = as.character(2017:2024),
  merra_release = "merra-2025-01-02"
)

create_daily_merra_data(merra_date)

Arguments

x

a vector of s2 cell identifers (s2_cell object)

dates

a list of date vectors for the MERRA data, must be the same length as x

merra_release

a character string of a release tag from which "pre-compiled" MERRA data binary is used instead of installing latest data from source; see details

merra_year

a character string that is the year for the merra data

merra_date

a date object that is the date for the merra data

Value

for get_merra_data(), a list of tibbles the same length as x, each containing merra data columns (merra_dust, merra_oc, merra_bc, merra_ss, merra_so4, merra_pm25) with one row per date in dates

for install_merra_data(), a character string path to the merra data

for create_daily_merra_data(), a tibble with columns for s2, date, and concentrations of PM2.5 total, dust, oc, bc, ss, so4

Details

  • Installed data are filtered to a bounding box around the contiguous US, averaged to daily values, and converted to micrograms per cubic meter ($ug/m^3$).

  • Total surface PM2.5 mass is calculated according to the formula in https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/FAQ/#Q4

  • Set options("appc_install_data_from_source"), or the environment variable APPC_INSTALL_DATA_FROM_SOURCE to any non-empty value to install MERRA-2 directly from their sources instead of using the released GitHub data binary.

    • An Earthdata account linked with permissions for GES DISC is required. The EARTHDATA_USERNAME and EARTHDATA_PASSWORD must be set. If a .env file is present, environment variables will be loaded using the dotenv package.

    • Set a proxy to be used by all httr calls in the merra functions with httr::set_config(httr::use_proxy( ... ))

Examples

d <- list(
  "8841b39a7c46e25f" = as.Date(c("2023-05-18", "2023-11-06")),
  "8841a45555555555" = as.Date(c("2023-06-22", "2023-08-15"))
)
get_merra_data(x = s2::as_s2_cell(names(d)), dates = d)
#> $`8841b39a7c46e25f`
#> # A tibble: 2 × 6
#>   merra_dust merra_oc merra_bc merra_ss merra_so4 merra_pm25
#>        <dbl>    <dbl>    <dbl>    <dbl>     <dbl>      <dbl>
#> 1      1.77      6.84    0.532    0.994      2.43      13.5 
#> 2      0.842     2.65    0.392    0.244      2.21       7.17
#> 
#> $`8841a45555555555`
#> # A tibble: 2 × 6
#>   merra_dust merra_oc merra_bc merra_ss merra_so4 merra_pm25
#>        <dbl>    <dbl>    <dbl>    <dbl>     <dbl>      <dbl>
#> 1       1.34     2.52    0.327    0.356      3.71       9.64
#> 2       1.18     2.80    0.441    0.722      5.78      13.1 
#>