In 2015 NASA launched the Soil Moisture Active Passive (SMAP) instrument, which measures global surface soil moisture and soil freeze-thaw conditions from space. The data are publicly available in HDF5 format via an FTP server hosted by the National Snow and Ice Data Center (NSIDC). The smapr package provides a suite of functions for programmatic discovery, download, exploration, and extraction of SMAP data.
Multiple SMAP data products are provided by the NSIDC, and these products vary in the amount of processing. Currently, smapr supports the more processed level 3 and level 4 data products, which represent global daily composite and global three hourly modeled data products, respectively. NSIDC provides documentation for all SMAP data products on their website, and we provide a summary of level 3 and level 4 products below.
| Dataset id | Description | Resolution |
|---|---|---|
| SPL3FTA | Radar Northern Hemisphere Daily Freeze/Thaw State | 3 km |
| SPL3SMA | Radar Global Daily Soil Moisture | 3 km |
| SPL3SMP | Radiometer Global Soil Moisture | 36 km |
| SPL3SMAP | Radar/Radiometer Global Soil Moisture | 9 km |
| SPL4SMAU | Surface/Rootzone Soil Moisture Analysis Update | 9 km |
| SPL4SMGP | Surface/Rootzone Soil Moisture Geophysical Data | 9 km |
| SPL4SMLM | Surface/Rootzone Soil Moisture Land Model Constants | 9 km |
| SPL4CMDL | Carbon Net Ecosystem Exchange | 9 km |
Data are hosted on an FTP server by the National Snow and Ice Data Center. The find_smap function searches for specific data products and returns a data frame of available data. As data mature and pass checks, versions advance. At any specific time, not all versions of all datasets for all dates may exist. For the most up to date overview of dataset versions, see the NSIDC SMAP data version webpage.
library(smapr)
library(raster)## Loading required package: spavailable_data <- find_smap(id = "SPL3SMAP", date = "2015-05-25", version = 3)
str(available_data)## 'data.frame': 1 obs. of 3 variables:
## $ name : chr "SMAP_L3_SM_AP_20150525_R13080_001"
## $ date : Date, format: "2015-05-25"
## $ ftp_dir: chr "SPL3SMAP.003/2015.05.25/"Given a data frame produced by find_smap, download_smap downloads the data onto the local file system. Unless a directory is specified as an argument, the data are stored in the user’s cache.
downloads <- download_smap(available_data)
str(downloads)## 'data.frame': 1 obs. of 4 variables:
## $ name : chr "SMAP_L3_SM_AP_20150525_R13080_001"
## $ date : Date, format: "2015-05-25"
## $ ftp_dir : chr "SPL3SMAP.003/2015.05.25/"
## $ local_dir: chr "/home/max/.cache/smap"The SMAP data are provided in HDF5 format, and in any one file there are actually multiple data sets, including metadata. The list_smap function allows users to inspect the contents of downloaded data at a high level (all = FALSE) or in depth (all = TRUE).
list_smap(downloads, all = FALSE)## $SMAP_L3_SM_AP_20150525_R13080_001
## group name otype dclass dim
## 0 / Metadata H5I_GROUP
## 1 / Soil_Moisture_Retrieval_Data H5I_GROUPlist_smap(downloads, all = TRUE)## $SMAP_L3_SM_AP_20150525_R13080_001
## group name
## 0 / Metadata
## 1 /Metadata AcquisitionInformation
## 2 /Metadata/AcquisitionInformation platform
## 3 /Metadata/AcquisitionInformation platformDocument
## 4 /Metadata/AcquisitionInformation radar
## 5 /Metadata/AcquisitionInformation radarDocument
## 6 /Metadata/AcquisitionInformation radiometer
## 7 /Metadata/AcquisitionInformation radiometerDocument
## 8 /Metadata DataQuality
## 9 /Metadata/DataQuality CompletenessOmission
## 10 /Metadata/DataQuality DomainConsistency
## 11 /Metadata DatasetIdentification
## 12 /Metadata Extent
## 13 /Metadata GridSpatialRepresentation
## 14 /Metadata/GridSpatialRepresentation Column
## 15 /Metadata/GridSpatialRepresentation GridDefinition
## 16 /Metadata/GridSpatialRepresentation GridDefinitionDocument
## 17 /Metadata/GridSpatialRepresentation Row
## 18 /Metadata Lineage
## 19 /Metadata/Lineage EASEGRID_LON_M
## 20 /Metadata/Lineage InputConfiguration
## 21 /Metadata/Lineage L2_SM_AP
## 22 /Metadata/Lineage MetadataConfiguration
## 23 /Metadata/Lineage OutputConfiguration
## 24 /Metadata/Lineage RunConfiguration
## 25 /Metadata OrbitMeasuredLocation
## 26 /Metadata ProcessStep
## 27 /Metadata ProductSpecificationDocument
## 28 /Metadata QADatasetIdentification
## 29 /Metadata SeriesIdentification
## 30 / Soil_Moisture_Retrieval_Data
## 31 /Soil_Moisture_Retrieval_Data EASE_column_index
## 32 /Soil_Moisture_Retrieval_Data EASE_row_index
## 33 /Soil_Moisture_Retrieval_Data albedo
## 34 /Soil_Moisture_Retrieval_Data alpha_tbh_hh
## 35 /Soil_Moisture_Retrieval_Data alpha_tbv_vv
## 36 /Soil_Moisture_Retrieval_Data bare_soil_roughness_retrieved
## 37 /Soil_Moisture_Retrieval_Data beta_tbh_hh
## 38 /Soil_Moisture_Retrieval_Data beta_tbv_vv
## 39 /Soil_Moisture_Retrieval_Data distance_from_nadir
## 40 /Soil_Moisture_Retrieval_Data freeze_thaw_fraction
## 41 /Soil_Moisture_Retrieval_Data gamma_hh_xpol
## 42 /Soil_Moisture_Retrieval_Data gamma_vv_xpol
## 43 /Soil_Moisture_Retrieval_Data landcover_class
## 44 /Soil_Moisture_Retrieval_Data latitude
## 45 /Soil_Moisture_Retrieval_Data longitude
## 46 /Soil_Moisture_Retrieval_Data radar_vegetation_index
## 47 /Soil_Moisture_Retrieval_Data retrieval_qual_flag
## 48 /Soil_Moisture_Retrieval_Data sigma0_hh_aggregated
## 49 /Soil_Moisture_Retrieval_Data sigma0_vv_aggregated
## 50 /Soil_Moisture_Retrieval_Data sigma0_xpol_aggregated
## 51 /Soil_Moisture_Retrieval_Data soil_moisture
## 52 /Soil_Moisture_Retrieval_Data soil_moisture_std_dev
## 53 /Soil_Moisture_Retrieval_Data spacecraft_overpass_time_seconds
## 54 /Soil_Moisture_Retrieval_Data spacecraft_overpass_time_utc
## 55 /Soil_Moisture_Retrieval_Data surface_flag
## 56 /Soil_Moisture_Retrieval_Data surface_temperature
## 57 /Soil_Moisture_Retrieval_Data tb_h_disaggregated
## 58 /Soil_Moisture_Retrieval_Data tb_h_disaggregated_qual_flag
## 59 /Soil_Moisture_Retrieval_Data tb_h_disaggregated_std
## 60 /Soil_Moisture_Retrieval_Data tb_v_disaggregated
## 61 /Soil_Moisture_Retrieval_Data tb_v_disaggregated_qual_flag
## 62 /Soil_Moisture_Retrieval_Data tb_v_disaggregated_std
## 63 /Soil_Moisture_Retrieval_Data vegetation_opacity
## 64 /Soil_Moisture_Retrieval_Data vegetation_water_content
## 65 /Soil_Moisture_Retrieval_Data water_body_fraction
## otype dclass dim
## 0 H5I_GROUP
## 1 H5I_GROUP
## 2 H5I_GROUP
## 3 H5I_GROUP
## 4 H5I_GROUP
## 5 H5I_GROUP
## 6 H5I_GROUP
## 7 H5I_GROUP
## 8 H5I_GROUP
## 9 H5I_GROUP
## 10 H5I_GROUP
## 11 H5I_GROUP
## 12 H5I_GROUP
## 13 H5I_GROUP
## 14 H5I_GROUP
## 15 H5I_GROUP
## 16 H5I_GROUP
## 17 H5I_GROUP
## 18 H5I_GROUP
## 19 H5I_GROUP
## 20 H5I_GROUP
## 21 H5I_GROUP
## 22 H5I_GROUP
## 23 H5I_GROUP
## 24 H5I_GROUP
## 25 H5I_GROUP
## 26 H5I_GROUP
## 27 H5I_GROUP
## 28 H5I_GROUP
## 29 H5I_GROUP
## 30 H5I_GROUP
## 31 H5I_DATASET INTEGER 3856 x 1624
## 32 H5I_DATASET INTEGER 3856 x 1624
## 33 H5I_DATASET FLOAT 3856 x 1624
## 34 H5I_DATASET FLOAT 3856 x 1624
## 35 H5I_DATASET FLOAT 3856 x 1624
## 36 H5I_DATASET FLOAT 3856 x 1624
## 37 H5I_DATASET FLOAT 3856 x 1624
## 38 H5I_DATASET FLOAT 3856 x 1624
## 39 H5I_DATASET FLOAT 3856 x 1624
## 40 H5I_DATASET FLOAT 3856 x 1624
## 41 H5I_DATASET FLOAT 3856 x 1624
## 42 H5I_DATASET FLOAT 3856 x 1624
## 43 H5I_DATASET INTEGER 3856 x 1624
## 44 H5I_DATASET FLOAT 3856 x 1624
## 45 H5I_DATASET FLOAT 3856 x 1624
## 46 H5I_DATASET FLOAT 3856 x 1624
## 47 H5I_DATASET INTEGER 3856 x 1624
## 48 H5I_DATASET FLOAT 3856 x 1624
## 49 H5I_DATASET FLOAT 3856 x 1624
## 50 H5I_DATASET FLOAT 3856 x 1624
## 51 H5I_DATASET FLOAT 3856 x 1624
## 52 H5I_DATASET FLOAT 3856 x 1624
## 53 H5I_DATASET FLOAT 3856 x 1624
## 54 H5I_DATASET STRING 3856 x 1624
## 55 H5I_DATASET INTEGER 3856 x 1624
## 56 H5I_DATASET FLOAT 3856 x 1624
## 57 H5I_DATASET FLOAT 3856 x 1624
## 58 H5I_DATASET INTEGER 3856 x 1624
## 59 H5I_DATASET FLOAT 3856 x 1624
## 60 H5I_DATASET FLOAT 3856 x 1624
## 61 H5I_DATASET INTEGER 3856 x 1624
## 62 H5I_DATASET FLOAT 3856 x 1624
## 63 H5I_DATASET FLOAT 3856 x 1624
## 64 H5I_DATASET FLOAT 3856 x 1624
## 65 H5I_DATASET FLOAT 3856 x 1624The extract_smap function extracts gridded data products (e.g., global soil moisture) and returns Raster* objects with the proper spatial projections etc. If more than one file has been downloaded and passed into the first argument, extract_smap extracts all of the rasters and returns a RasterStack.
sm_raster <- extract_smap(downloads, "Soil_Moisture_Retrieval_Data/soil_moisture")
plot(sm_raster, main = "Level 3 soil moisture: May 25, 2015")
The raster stack can be saved as a GeoTIFF using the writeRaster function from the raster pacakge.
writeRaster(sm_raster, "wgs84_ft.tif")Bug reports, issues, and feature requests can be submitted via GitHub: https://github.com/mbjoseph/smapr