Contents

SWESARR Tutorial

SWESARR Tutorial

NASA

Objectives: This is a 30-minute tutorial where we will ...
  1. Introduce SWESARR
  2. Briefly introduce active and passive microwave remote sensing
  3. Learn how to access, filter, and visualize SWESARR data

What is SWESARR?

  • Description from Batuhan Osmanoglu.
  • Airborne sensor system measuring active and passive microwave measurements
  • Colocated measurements are taken simultaneously using an ultra-wideband antenna

SWESARR gives us insights on the different ways active and passive signals are influenced by snow over large areas.

Active and Passive? Microwave Remote Sensing?

Passive Systems

  • All materials can naturally emit electromagnetic waves

  • What is the cause?



  • Material above zero Kelvin will display some vibration or movement of particles

  • These moving, charged particles will induce electromagnetic waves

  • If we’re careful, we can measure these waves with a radio wave measuring tool, or “radiometer”

  • Radiometers see emissions from many sources, but they’re usually very weak

  • It’s important to design a radiometer that (1) minimizes side lobes and (2) allows for averaging over the main beam

  • For this reason, radiometers often have low spatial resolution

✏️ Radiometers allow us to study earth materials through incoherent averaging of naturally emitted signals

Active Systems

  • While radiometers generally measure natural electromagnetic waves, radars measure man-made electromagnetic waves

  • Transmit your own wave, and listen for the returns

  • The return of this signal is dependent on the surface and volume characteristics of the material it contacts

✏️ Synthetic aperture radar allows for high spatial resolution through processing of coherent signals

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SWESARR Sensors

SWESARR Frequencies, Polarization, and Bandwidth Specification

Center-Frequency (GHz)

Band

Sensor

Bandwidth (MHz)

Polarization

9.65

X

SAR

200

VH and VV

10.65

X

Radiometer

200

H

13.6

Ku

SAR

200

VH and VV

17.25

Ku

SAR

200

VH and VV

18.7

K

Radiometer

200

H

36.5

Ka

Radiometer

1,000

H


SWESARR Coverage

  • Below: radiometer coverage for all passes made between February 10 to February 12, 2020

  • SWESARR flights cover many snowpit locations over the Grand Mesa area as shown by the dots in blue

Reading SWESARR Data



Accessing Data: SAR

SAR Data Example

# Import several libraries. 
# comments to the right could be useful for local installation on Windows.

from shapely import speedups      # https://www.lfd.uci.edu/~gohlke/pythonlibs/
speedups.disable()                # <-- handle a potential error in cartopy

import requests                   # !conda install -c anaconda requests 

# raster manipulation libraries
import rasterio                   # https://www.lfd.uci.edu/~gohlke/pythonlibs/
from osgeo import gdal            # https://www.lfd.uci.edu/~gohlke/pythonlibs/
import cartopy.crs as ccrs        # https://www.lfd.uci.edu/~gohlke/pythonlibs/
import rioxarray as rxr           # !conda install -c conda-forge rioxarray
import xarray as xr               # !conda install -c conda-forge xarray dask netCDF4 bottleneck

# plotting tools
from matplotlib import pyplot     # !conda install matplotlib
import datashader as ds           # https://www.lfd.uci.edu/~gohlke/pythonlibs/
import hvplot.xarray              # !conda install hvplot

# append the subfolders of the current working directory to pythons path

import os
import sys

swesarr_subdirs = ["data", "util"]
tmp = [sys.path.append(os.getcwd() + "/" + sd) for sd in swesarr_subdirs]
del tmp # suppress Jupyter notebook output, delete variable

from helper import gdal_corners, join_files, join_sar_radiom