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UTH data from microwave measurements

Long-term UTH
Figure 1. Median UTH from AMSU-B on NOAA 16.
UTH annual cycle
Figure 2. Annual cycle of UTH.

Scientific Objectives

Upper tropospheric humidity (UTH) is a key parameter of Earth's climate system. Our goal is to derive a UTH data set from operational satellite microwave data. In the papers linked below you can find more information on the scientific background, on the definition of UTH, and on the methodology that was used to derive it.

Data from the AMSU-B instruments on NOAA 15 to 17 and MHS on NOAA 18 and MetOp-A have been processed. The figures here show some data examples. Figure 1 shows the median UTH distribution from NOAA 16, Figure 2 a movie of the anual cycle.

Science Team

The project is a collaboration between LTU and the Met Office Hadley Centre, UK.

Project scientists (in alphabetical order):

  • Stefan Buehler (LTU)
  • Viju Oommen John (Met Office Hadley Centre)
  • Mathias Milz (LTU)


The UTH data are freely available from the following address. The data are distributed in a compressed format. To extract the data from the archive use the'tar jxf' command. The format of current version of the data is NetCDF.

  • Current version: uth-data-v2d.tar.bz2
  • Monthly statistics (mean, standard deviation, median, and no. of pixels) are available.
  • Start date - 1999/01
  • End date - 2008/05
  • Spatial resolution: 2.5 x 2.5 degrees
  • Spatial bounds: 0 to 360 in longitude and -60 to +60 in latitude
  • First grid box centre is (1.25, -58.75) and last is (358.75, 58.75)
  • File names: noaaxx_yyyy_mm.nc
  • xx is for 2-digit satellite number, yyyy for 4-digit year, and mm for 2-digit month of the year
  • Previous versions:

Available parameters

   lon = 144 ;
   lat = 48 ;

float lon(lon) ;
   lon:long_name = "longitude" ;
   lon:units = "degrees_east" ;
float lat(lat) ;
   lat:long_name = "latitude" ;
   lat:units = "degrees_north" ;
float uth_water_ascend_cloud_free_mean(lat, lon) ;
float uth_water_ascend_cloud_free_standard_deviation(lat, lon) ;
float uth_water_ascend_cloud_free_median(lat, lon) ;
float uth_water_ascend_cloud_free_n_pixels(lat, lon) ;
float uth_water_ascend_mean(lat, lon) ;
float uth_water_ascend_standard_deviation(lat, lon) ;
float uth_water_ascend_median(lat, lon) ;
float uth_water_ascend_n_pixels(lat, lon) ;
float uth_water_descend_cloud_free_mean(lat, lon) ;
float uth_water_descend_cloud_free_standard_deviation(lat, lon) ;
float uth_water_descend_cloud_free_median(lat, lon) ;
float uth_water_descend_cloud_free_n_pixels(lat, lon) ;
float uth_water_descend_mean(lat, lon) ;
float uth_water_descend_standard_deviation(lat, lon) ;
float uth_water_descend_median(lat, lon) ;
float uth_water_descend_n_pixels(lat, lon) ;
float uth_ice_ascend_cloud_free_mean(lat, lon) ;
float uth_ice_ascend_cloud_free_standard_deviation(lat, lon) ;
float uth_ice_ascend_cloud_free_median(lat, lon) ;
float uth_ice_ascend_cloud_free_n_pixels(lat, lon) ;
float uth_ice_ascend_mean(lat, lon) ;
float uth_ice_ascend_standard_deviation(lat, lon) ;
float uth_ice_ascend_median(lat, lon) ;
float uth_ice_ascend_n_pixels(lat, lon) ;
float uth_ice_descend_cloud_free_mean(lat, lon) ;
float uth_ice_descend_cloud_free_standard_deviation(lat, lon) ;
float uth_ice_descend_cloud_free_median(lat, lon) ;
float uth_ice_descend_cloud_free_n_pixels(lat, lon) ;
float uth_ice_descend_mean(lat, lon) ;
float uth_ice_descend_standard_deviation(lat, lon) ;
float uth_ice_descend_median(lat, lon) ;
float uth_ice_descend_n_pixels(lat, lon) ;
float n_dcc_pixels_ascend(lat, lon) ;
float n_dcc_pixels_descend(lat, lon) ;

We will be very happy to receive any feedback if you use our UTH data product. Also, if you use these data in your published work, we kindly ask to give credit to the origin of the data, by citing the papers given below.

Summary of the changes:

  • Version 2d:
    • Extended until April 2009
  • Version 2c:
    • Extended until December 2008
    • Contains bug fix for deep convective clouds. Instead of putting total number of dcc pixels for the month, only the number of dcc pixels for day one was kept.
  • Version 2b:
    • Added new satellites NOAA-18 and MetOp-A
  • From version 1 to version 2:
    • Separated ascending and descending passes
    • Data format is changed to NetCDF


Recommended reading

Thanks to:

  • Comprehensive Large Array-data Stewardship System, NOAA (especially Lisa Neclos) for providing level 1b AMSU-B data set.
  • EUMETSAT NWP SAF for the AAPP package


  • Viju Oommen John: viju.john (at) metoffice.gov.uk