# Remote sensing data

## Overview of remote sensing data that may be useful for hydrological analysis

### Spectrometer

Institute Satellite Sensor channels launched resolution Notes
ESA ENVISAT MERIS 15 March 2002 260x290m Visible and Near Infrared spectrum (390 to 1040 nm), cloud cover, water bodies, frequency 3 days (higher at the poles)
NASA TIROS-N AVHRR 4 1.09x1.09km http://www.nsof.class.noaa.gov.
Can be used for cloud cover (Bendix et al.), surface temperature (ref), delineation of water bodies (Zhou et al., 2000)
NOAA NOAA-7 AVHRR 5
NOAA NOAA-15 AVHRR 6 May 1998
NOAA NOAA-16 AVHRR 6 Sep 2000
NOAA NOAA-17 AVHRR 6 Jun 2002
NOAA NOAA-18 AVHRR 6 May 2005
Eumetsat METOP AVHRR ? cloud cover, surface temperature
ESA MSG-1 & 2 (Meteosat-8 & 9) SEVIRI 12 2002 Spinning Enhanced Visible and Infrared Imager. [Africa and Europe] @ 15 minutes. 8 channels can be used for monitoring the earth surface. Channel 12 is a high resolution visible (hrv) channel. Resolution: 3 km at the sub-satellite point (5 – 6 km over Europe). Channel 12 has a resolution of 1 km at the sub-satellite point (1.5 – 2 km over Europe). Can be used for precipitation (see e.g. Thies et al. doi:10.1029/2008JD010464)
NASA TRMM ?? 25x25km (0.25°) rainfall
NASA AQUA AMSR-E May 2002 6.25 - 25 km Wind speed, water vapor, cloud liquid water, Snow water equivalent,Surface Soil Moisture (daily). [More details].
NASA TERRA ASTER 15 1999 15-90m temperature, reflectance, elevation, land use. On demand; some images exist for the Andes
NASA TERRA/AQUA MODIS 36 1999/2002 see notes http://www.landcover.org, spatial resolution: 250 m (bands 1-2) 500 m (bands 3-7) 1000 m (bands 8-36), temporal resolution 1 to 2 days, visible and near infrared (400 to 14400 nm)

Institute Satellite Sensor launched resolution Notes
ESA ENVISAT ASAR March 2002 30m APG HH and HV -> delineation of water bodies
ESA ENVISAT Altimeter March 2002 400m altitude (only 1 dimension)
ASI COSMO-SkyMed SAR June 2007 Constellation of 4 satellites

### other

One that has not gone up yet: SWOT

## Data aquisition

### ESA

ESA is a very big engine and it is tricky to find what you are actually looking for or what you need but there is lots:

The following link is a shortcut to ESA's 'Resources' page that includes upcoming workshops, the ESA library, data samples and archives, and probably most useful for anyone working with ESA data, there are ESA-tailored software tools that run free-of-charge on Windows, linux and also MacOS (although mac versions are usually appearing a bit later than the other two!): http://earth.esa.int/resources/ P.S. I attended an ESA Land Training course in Lisbon in September 2007 on Flooding/Soil moisture and Forests and have lots of lecture notes on ASAR, ALOS and how to use these data with the BEST, BEAM and POLSARPRO packages (I have actually worked with an ALOS quadpol for tree height and soil moisture retrieval: amazing data!). If you want any of these notes or some help, just email me (guy.schumann@bristol.ac.uk) and I'll try to help!

There is a useful tool from the ESA website to search for available images (does ENVISAT and others):

To access online (last 7-10 days) data and submit CAT-1 (free data) proposals for projects:

To answer third party mission (from non-ESA satellites) calls: http://eopi.esa.int/esa/esa?type=10&cmd=aolist, and go to the 'TPM' link to the left of the page,

and AO (Announcement of Opportunities) calls: http://eopi.esa.int/esa/esa?type=10&cmd=aolist

### ESA conferences and workshops

Anyone interested in this year's (2008) ESA summer school in August (4-14) at the ESRIN centre in Italy? Topic: Data assimilation, monitoring and modelling the Earth System. Have a look at: http://envisat.esa.int/envschool/

## Detailed info on satellites

### meteosat

The channels of SEVERI on board meteosat-8 (spectral band / μm)

Channel min max description
1 0.635 0.56 0.71 visual
2 0.81 0.74 0.88 visual
3 1.64 1.50 1.78 near infrared
4 3.90 3.48 4.36 infrared
5 6.25 5.35 7.15 infrared (water vapour absorption)
6 7.35 6.85 7.85 infrared (water vapour absorption)
7 8.70 8.30 9.1 infrared
8 9.66 9.38 9.94 infrared (ozone absorption)
9 10.80 9.80 11.80 infrared
10 12.00 11.00 13.00 infrared
11 13.40 12.40 14.40 infrared (CO2 absorption)
12 0.75 0.60 0.90 high resolution visual broadband (hrv)

## Processing

### Envisat altimeter

Some information that may make life easier when dealing with ESA's altimeter N1 files:

• ESA's Basic Radar Altimeter Toolbox provides a set of tools and an interface for extracting data from the original N1 files. The interface is broken on recent linux versions due to obsolete dependencies but the command line tools work.
• The XY extraction utility (BratCreateZFXY) does not seem capable of extracting the original data directly. It requires a predefined raster size and automatically interpolates before exporting.
• BratCreateYFX extracts the measurements in the original resolution. However it only includes one dimension so you have to add the other one manually as a dataset. Something like this in the parameter file:
    # longitude
X=lon
X_NAME=X
X_TYPE=Longitude
X_UNIT=degrees_east
X_TITLE=X
# latitude
FIELD=lat
FIELD_NAME=Y
FIELD_TYPE=Data
FIELD_UNIT=count
FIELD_TITLE=Y
# data of interest follow
FIELD=alt_cog_ellip
FIELD_NAME=alt_cog_ellip
FIELD_TYPE=Data
FIELD_UNIT=mm
FIELD_TITLE=alt_cog_ellip

• Extracting many fields from many files is much easier using the command line tools and a batch script.

## downscaling techniques

### statistical

singular vector decomposition

Bretherton CS, Smith C, Wallace JM. 1992. An intercomparison of methods for finding coupled patterns in climate data. Journal of Wilks DS. 1995. Statistical Methods in the Atmospheric Sciences. Climate 5: 541–560