Tuesday, February 9, 2010

Taking A Look At Raw AMSR-E Data

In this post we're going to take a look at the data in the Level 2A AMSR-E file. But first, a short review on how the AMSR-E scans data.

The AMSRE-E scans at 6 frequencies: 6.9, 10.7, 18.7, 23.8, 36.5, and 89.0 GHz. There are 5 scanning resolutions. The first four scanning resolutions are considered "low res" and stored in an array of data that is 1994 by 243 positions. The fifth scanning resolution is "high res" and stored in an array that is 1994 by 486 positions.

There are also smoothed and unsmoothed versions of the data. The chart below shows which versions of data for each frequency are stored in the Level 2A file.

Link to original table
AMSR-E Spatial Characteristics of Observations
Reso-lutionFoot printMean spatial resolutionChannels
89.0 GHz36.5 GHz23.8 GHz18.7 GHz10.7 GHz6.9 GHz
75 km x 43 km
56 km
51 km x 29 km
38 km
27 km x 16 km
21 km
14 km x 8 km
12 km
6 km x 4 km
5.4 km
•  Includes Level-2A (smoothed) data
o  Includes Level 1B (un smoothed) data at original spatial resolution

In addition to all this each scan has two components, a vertical (V) component and a horizontal (H) component. These different components are used to measure electric and magnetic values which in turn are used to make determinations about exactly what is being scanned (land, sea, ice, water vapor, etc.)

All of these variations are stored in the Level 2A AMSR-E file. The table below provides the variable names for all this data.

Level 2A Variable names
Variable NameData
6.9V_Res.1_TB_(not-resampled)6.9 V Res 1
6.9H_Res.1_TB_(not-resampled)6.9 H Res 1
10.7V_Res.2_TB_(not-resampled)10.7 V Res 2
10.7H_Res.2_TB_(not-resampled)10.7 H Res 2
18.7V_Res.3_TB_(not-resampled)18.7 V Res 3
18.7H_Res.3_TB_(not-resampled)18.7 H Res 3
23.8V_Approx._Res.3_TB_(not-resampled)23.8 V Res 3
23.8H_Approx._Res.3_TB_(not-resampled)23.8 H Res 3
36.5V_Res.4_TB_(not-resampled)36.5 V Res 3
36.5H_Res.4_TB_(not-resampled)36.5 H Res 3
6.9V_Res.1_TB6.9 V Res 1 Smoothed
6.9H_Res.1_TB6.9 H Res 1 Smoothed
10.7V_Res.1_TB10.7 V Res 1 Smoothed
10.7H_Res.1_TB10.7 H Res 1 Smoothed
10.7V_Res.2_TB10.7 V Res 2 Smoothed
10.7H_Res.2_TB10.7 H Res 2 Smoothed
18.7V_Res.1_TB18.7 V Res 1 Smoothed
18.7H_Res.1_TB18.7 H Res 1 Smoothed
18.7V_Res.2_TB18.7 V Res 2 Smoothed
18.7H_Res.2_TB18.7 H Res 2 Smoothed
23.8V_Res.1_TB23.8 V Res 1 Smoothed
23.8V_Res.1_TB23.8 H Res 1 Smoothed
23.8V_Res.2_TB23.8 V Res 2 Smoothed
23.8H_Res.2_TB23.8 H Res 2 Smoothed
23.8V_Res.3_TB23.8 V Res 3 Smoothed
23.8H_Res.3_TB23.8 H Res 3 Smoothed
36.5V_Res.1_TB36.5 V Res 1 Smoothed
36.5H_Res.1_TB36.5 H Res 1 Smoothed
36.5V_Res.2_TB36.5 V Res 2 Smoothed
36.5H_Res.2_TB36.5 H Res 2 Smoothed
36.5V_Res.3_TB36.5 V Res 3 Smoothed
36.5H_Res.3_TB36.5 H Res 3 Smoothed
89.0V_Res.1_TB89.0 V Res 1 Smoothed
89.0H_Res.1_TB89.0 H Res 1 Smoothed
89.0V_Res.2_TB89.0 V Res 2 Smoothed
89.0H_Res.2_TB89.0 H Res 2 Smoothed
89.0V_Res.3_TB89.0 V Res 3 Smoothed
89.0H_Res.3_TB89.0 H Res 3 Smoothed
89.0V_Res.4_TB89.0 V Res 4 Smoothed
89.0H_Res.4_TB89.0 H Res 4 Smoothed
89.0V_Res.5A_TB_(not-resampled)89.0 V Res 5
89.0H_Res.5A_TB_(not-resampled)89.0 H Res 5

The different frequencies are used to measure different attributes of the Earth, as shown in the table below.

Frequency Measurements
6.9Sea Surface Temperature, Soil Moisture, Vegetation
10.7Sea Surface Temperature, Wind Speed
18.7Wind Speed, Water Vapor
36.5Cloud Liquid Water
89.0Rain Rate

With the above information, you can pull the desired data from the Level 2A file. The data for an actual file for 36.5V_Res.4_TB_(not-resampled), which the cloud liquid water frequency,  is shown below. It shows a single scan line.

References And Previous Posts In this Series:
Taking A Look At Raw UAH Data
HDF Reader C++ Code Is Written!
Some Useful Climate Code
Summary Of Aqua Satellite Data, Computer Code, And Broken Equipment
Aqua Satellite Raw AMSR-E Data
Aqua Satellite Raw UAH Data, Part 2
Aqua Satellite Raw UAH Data, Part 1
Satellite Summary
Aqua Satellite Data Processing
A Note On The UAH And RSS Raw Data
How UAH And RSS Temperatures Are Measured
Overview Of The Aqua Satellite
Looking At The Aqua Satellite Data
UAH Satellite Data
Dangit! More Climate Stuff. UAH and RSS Raw Data

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