---
title: "nasapower"
author: "Adam H. Sparks"
output:
  rmarkdown::html_vignette:
    toc: true
vignette: >
  %\VignetteIndexEntry{nasapower}
  %\VignetteEngine{knitr::rmarkdown_notangle}
  %\VignetteEncoding{UTF-8}
---



## Introduction

{nasapower} aims to make it quick and easy to automate downloading NASA [POWER](https://power.larc.nasa.gov) global meteorology, surface solar energy and climatology data  data in your R session as a tidy data frame for analysis and use in modelling or other purposes using `get_power()`.
POWER (Prediction Of Worldwide Energy Resource) data are freely available for download through a web interface with a spatial resolution of 0.5 x 0.625 degree latitude and longitude for meteorology and  1 x 1 degree latitude and longitude for solar parameters with various temporal resolutions depending on the POWER parameter and community.

## Using get_power() to fetch POWER data

The `get_power()` function has eight possible arguments and returns a data frame with a metadata header in the current R session.

### Example fetching daily data for a single point

Fetch daily "AG" community temperature, relative humidity and precipitation for January 1985 for Kingsthorpe, Queensland, Australia.


``` r
library("nasapower")
daily_single_ag <- get_power(
  community = "ag",
  lonlat = c(151.81, -27.48),
  pars = c("RH2M", "T2M", "PRECTOTCORR"),
  dates = c("1985-01-01", "1985-01-31"),
  temporal_api = "daily"
)

daily_single_ag
#> NASA/POWER CERES/MERRA2 Native Resolution Daily Data  
#>  Dates (month/day/year): 01/01/1985 through 01/31/1985  
#>  Location: Latitude  -27.48   Longitude 151.81  
#>  Elevation from MERRA-2: Average for 0.5 x 0.625 degree lat/lon region = 442.77 meters 
#>  The value for missing source data that cannot be computed or is outside of the sources availability range: NA  
#>  Parameter(s):  
#>  
#>  Parameters: 
#>  RH2M            MERRA-2 Relative Humidity at 2 Meters (%) ;
#>  T2M             MERRA-2 Temperature at 2 Meters (C) ;
#>  PRECTOTCORR     MERRA-2 Precipitation Corrected (mm/day)  
#>  
#> # A tibble: 31 × 10
#>      LON   LAT  YEAR    MM    DD   DOY YYYYMMDD    RH2M   T2M PRECTOTCORR
#>    <dbl> <dbl> <dbl> <int> <int> <int> <date>     <dbl> <dbl>       <dbl>
#>  1  152. -27.5  1985     1     1     1 1985-01-01  54.7  24.9        0.9 
#>  2  152. -27.5  1985     1     2     2 1985-01-02  42.1  28.6        0.49
#>  3  152. -27.5  1985     1     3     3 1985-01-03  43.4  27.4        0.01
#>  4  152. -27.5  1985     1     4     4 1985-01-04  48.9  24.3        0.05
#>  5  152. -27.5  1985     1     5     5 1985-01-05  55.3  26.5        1.33
#>  6  152. -27.5  1985     1     6     6 1985-01-06  60.2  27.0        4.88
#>  7  152. -27.5  1985     1     7     7 1985-01-07  63.1  27.2       10.7 
#>  8  152. -27.5  1985     1     8     8 1985-01-08  70.6  24.9       10   
#>  9  152. -27.5  1985     1     9     9 1985-01-09  60    26.1        2.45
#> 10  152. -27.5  1985     1    10    10 1985-01-10  45.2  27.0        0.48
#> # ℹ 21 more rows
```

### Example fetching daily data for an area

Fetch daily "ag" community relative humidity and temperature for south east Queensland region.


``` r
daily_region_ag <- get_power(
  community = "ag",
  lonlat = c(150.5, -28.5 , 153.5, -25.5),
  pars = c("RH2M", "T2M"),
  dates = c("1985-01-01", "1985-01-02"),
  temporal_api = "daily"
)

daily_region_ag
#> NASA/POWER CERES/MERRA2 Native Resolution Daily Data  
#>  Dates (month/day/year): 01/01/1985 through 01/02/1985  
#>  Location: Regional  
#>  Elevation from MERRA-2: Average for 0.5 x 0.625 degree lat/lon region = na meters 
#>  The value for missing source data that cannot be computed or is outside of the sources availability range: NA  
#>  Parameter(s):  
#>  
#>  Parameters: 
#>  RH2M     MERRA-2 Relative Humidity at 2 Meters (%) ;
#>  T2M      MERRA-2 Temperature at 2 Meters (C)  
#>  
#> # A tibble: 72 × 9
#>      LAT   LON  YEAR    MM    DD   DOY YYYYMMDD    RH2M   T2M
#>    <dbl> <dbl> <dbl> <int> <int> <int> <date>     <dbl> <dbl>
#>  1 -28.2  151.  1985     1     1     1 1985-01-01  43.6  26.5
#>  2 -28.2  151.  1985     1     1     1 1985-01-01  44.4  25.8
#>  3 -28.2  152.  1985     1     1     1 1985-01-01  52.6  24.0
#>  4 -28.2  152.  1985     1     1     1 1985-01-01  57.7  23.9
#>  5 -28.2  153.  1985     1     1     1 1985-01-01  61.4  24.9
#>  6 -28.2  153.  1985     1     1     1 1985-01-01  66.1  26.0
#>  7 -27.8  151.  1985     1     1     1 1985-01-01  45.8  26.5
#>  8 -27.8  151.  1985     1     1     1 1985-01-01  47.9  26.0
#>  9 -27.8  152.  1985     1     1     1 1985-01-01  53.4  24.8
#> 10 -27.8  152.  1985     1     1     1 1985-01-01  56.7  25.1
#> # ℹ 62 more rows
```

### Example fetching interannual data for an area

Fetch interannual solar cooking parameters for south east Queensland region.


``` r
interannual_re <- get_power(
  community = "re",
  lonlat = c(150.5, -28.5 , 153.5, -25.5),
  dates = c("1984", "1985"),
  temporal_api = "monthly",
  pars = c("CLRSKY_SFC_SW_DWN",
           "ALLSKY_SFC_SW_DWN")
)

interannual_re
#> NASA/POWER CERES/MERRA2 Native Resolution Monthly and Annual  
#>  Dates (month/day/year): 01/01/1984 through 12/31/1985  
#>  Location: Regional  
#>  Elevation from MERRA-2: Average for 0.5 x 0.625 degree lat/lon region = na meters 
#>  The value for missing source data that cannot be computed or is outside of the sources availability range: NA  
#>  Parameter(s):  
#>  
#>  Parameters: 
#>  ALLSKY_SFC_SW_DWN     CERES SYN1deg All Sky Surface Shortwave Downward Irradiance (kW-hr/m^2/day) ;
#>  CLRSKY_SFC_SW_DWN     CERES SYN1deg Clear Sky Surface Shortwave Downward Irradiance (kW-hr/m^2/day)  
#>  
#> # A tibble: 144 × 17
#>    PARAMETER       YEAR   LAT   LON   JAN   FEB   MAR   APR   MAY   JUN   JUL   AUG   SEP   OCT   NOV
#>    <chr>          <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#>  1 ALLSKY_SFC_SW…  1984 -25.8  151.  6.01  6.49  5.79  4.67  4.12  3.77  2.46  4.87  6.11  5.5   7.97
#>  2 ALLSKY_SFC_SW…  1984 -25.8  151.  5.92  5.97  5.64  4.37  4.01  3.61  2.6   4.8   5.84  5.24  7.6 
#>  3 ALLSKY_SFC_SW…  1984 -25.8  152.  5.92  5.97  5.64  4.37  4.01  3.61  2.6   4.8   5.84  5.24  7.6 
#>  4 ALLSKY_SFC_SW…  1984 -25.8  152.  5.96  5.85  5.56  4.26  3.92  3.52  2.66  4.59  5.58  4.94  7.23
#>  5 ALLSKY_SFC_SW…  1984 -25.8  153.  5.96  5.85  5.56  4.26  3.92  3.52  2.66  4.59  5.58  4.94  7.23
#>  6 ALLSKY_SFC_SW…  1984 -25.8  153.  6.23  6.05  5.88  4.26  3.81  3.3   2.96  4.73  5.66  5.25  7.6 
#>  7 ALLSKY_SFC_SW…  1984 -26.2  151.  5.97  6.65  6     4.66  4.02  3.72  2.28  4.86  6.08  5.74  7.74
#>  8 ALLSKY_SFC_SW…  1984 -26.2  151.  6     6.38  5.71  4.38  4.01  3.66  2.17  4.88  6.01  5.43  7.46
#>  9 ALLSKY_SFC_SW…  1984 -26.2  152.  6     6.38  5.71  4.38  4.01  3.66  2.17  4.88  6.01  5.43  7.46
#> 10 ALLSKY_SFC_SW…  1984 -26.2  152.  5.75  5.96  5.37  4.13  3.8   3.44  2.38  4.81  5.75  4.99  6.94
#> # ℹ 134 more rows
#> # ℹ 2 more variables: DEC <dbl>, ANN <dbl>
```

### Example fetching climatology data

Climatology data can be retrieved for point or regional areas as demonstrated previously.
Change the `temporal_api` value to "climatology" to get these data.

Fetch "ag" climatology for temperature and relative humidity for Kingsthorpe, Queensland, Australia.


``` r
climatology_ag <- get_power(
  community = "ag",
  pars = c("T2M", "RH2M"),
  lonlat = c(151.81, -27.48),
  temporal_api = "climatology"
)

climatology_ag
#> NASA/POWER CERES/MERRA2 Native Resolution Climatology Climatologies  
#>  20-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2020)  
#>  Location: Latitude  -27.48   Longitude 151.81  
#>  Elevation from MERRA-2: Average for 0.5 x 0.625 degree lat/lon region = 442.77 meters 
#>  The value for missing source data that cannot be computed or is outside of the sources availability range: NA  
#>  Parameter(s):  
#>  
#>  Parameters: 
#>  T2M      MERRA-2 Temperature at 2 Meters (C) ;
#>  RH2M     MERRA-2 Relative Humidity at 2 Meters (%)  
#>  
#> # A tibble: 2 × 16
#>     LON   LAT PARAMETER   JAN   FEB   MAR   APR   MAY   JUN   JUL   AUG   SEP   OCT   NOV   DEC   ANN
#>   <dbl> <dbl> <chr>     <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#> 1  152. -27.5 T2M        24.7  23.7  22.0  19.0  15.1  12.6  11.6  13.1  16.9  20    22.3  23.7  18.7
#> 2  152. -27.5 RH2M       64.7  69.6  71.1  70.5  69.1  75.1  70.4  63.1  59.8  59.4  60.3  63.4  66.4
```

_Note_ the associated metadata in the data frame header are not saved if the data are exported to a file format other than an R data format, _e.g._, .Rdata, .rda or .rds.

## Interrogating the API for available parameters

The POWER API offers functionality to get detailed information on any parameter offered or all parameters that are offered for a given community and temporal API.
This can be used to find available parameter names and definitions for each community and temporal API.

Fetch the complete available information for the temperature at 2 metres above the Earth's surface, T2M.


``` r
query_parameters(pars = "T2M")
#> $T2M
#> $T2M$temporal
#> $T2M$temporal$HOURLY
#> $T2M$temporal$HOURLY$name
#> [1] "Temperature at 2 Meters"
#> 
#> $T2M$temporal$HOURLY$definition
#> [1] "The average air (dry bulb) temperature at 2 meters above the surface of the earth."
#> 
#> $T2M$temporal$HOURLY$communities
#> [1] "AG" "RE" "SB"
#> 
#> $T2M$temporal$HOURLY$calculated
#> [1] FALSE
#> 
#> 
#> $T2M$temporal$DAILY
#> $T2M$temporal$DAILY$name
#> [1] "Temperature at 2 Meters"
#> 
#> $T2M$temporal$DAILY$definition
#> [1] "The average air (dry bulb) temperature at 2 meters above the surface of the earth."
#> 
#> $T2M$temporal$DAILY$communities
#> [1] "AG" "RE" "SB"
#> 
#> $T2M$temporal$DAILY$calculated
#> [1] FALSE
#> 
#> 
#> $T2M$temporal$MONTHLY
#> $T2M$temporal$MONTHLY$name
#> [1] "Temperature at 2 Meters"
#> 
#> $T2M$temporal$MONTHLY$definition
#> [1] "The average air (dry bulb) temperature at 2 meters above the surface of the earth."
#> 
#> $T2M$temporal$MONTHLY$communities
#> [1] "AG" "RE" "SB"
#> 
#> $T2M$temporal$MONTHLY$calculated
#> [1] FALSE
#> 
#> 
#> $T2M$temporal$CLIMATOLOGY
#> $T2M$temporal$CLIMATOLOGY$name
#> [1] "Temperature at 2 Meters"
#> 
#> $T2M$temporal$CLIMATOLOGY$definition
#> [1] "The average air (dry bulb) temperature at 2 meters above the surface of the earth."
#> 
#> $T2M$temporal$CLIMATOLOGY$communities
#> [1] "AG" "RE" "SB"
#> 
#> $T2M$temporal$CLIMATOLOGY$calculated
#> [1] FALSE
#> 
#> 
#> 
#> $T2M$type
#> [1] "METEOROLOGY"
```

Fetch complete temporal and community specific attribute information for "T2M" in the "ag" community for the "hourly" temporal API.


``` r
query_parameters(pars = "T2M",
                 community = "ag",
                 temporal_api = "hourly")
#> $T2M
#> $T2M$type
#> [1] "METEOROLOGY"
#> 
#> $T2M$temporal
#> [1] "HOURLY"
#> 
#> $T2M$source
#> [1] "MERRA2"
#> 
#> $T2M$community
#> [1] "AG"
#> 
#> $T2M$calculated
#> [1] FALSE
#> 
#> $T2M$inputs
#> NULL
#> 
#> $T2M$units
#> [1] "C"
#> 
#> $T2M$name
#> [1] "Temperature at 2 Meters"
#> 
#> $T2M$definition
#> [1] "The average air (dry bulb) temperature at 2 meters above the surface of the earth."
```

## A Note on API Throttling

The POWER API endpoints limit queries to prevent overloads due to repetitive and rapid requests.
If you find that the API is throttling your queries, I suggest that you investigate the use of `limit_rate()` from [_ratelimitr_](https://cran.r-project.org/package=ratelimitr) to create self-limiting functions that will respect the rate limits that the API has in place.
It is best to check the [POWER website](https://power.larc.nasa.gov/docs/services/api/#rate-limiting) for the latest rate limits as they differ between temporal APIs and may change over time as the project matures.

## References

<https://power.larc.nasa.gov>

<https://power.larc.nasa.gov/docs/methodology/>