Epic Fall 99 Monitoring cruise on R/V Ronald H. Brown
C. Fairall 6/29/00
chris.fairall@noaa.gov

The ETL radar group operated a microwave radiometer (MWR) manufactured by Radiometrics
Inc. (Boulder) for this cruise.  Contact Duane Hazen (ETL) for details on the instrument.  Duane
used sondes and tipcals to 'calibrate' the system and gave me hourly files.  I wrote a matlab
program that read his data, stripped out the stuff I wanted, and wrote new files with the raw 21-s
time resolution (micro_s.txt), 10-min (micro_10min.txt), and hourly time resolution (micro_h.txt).  The data on the files is as
follows:

f99_micro_s.txt         size= (111566,3)

:,1  decimal julian date  (301 to 337)
:,2  IWV, integrated atmospheric water vapor (column precipitable water), cm
:,3  IWL, integrated cloud liquid content, cm

f99_micro_h.txt         size= (672,6)

:,1  decimal julian date  (301 to 337)
:,2  IWC, integrated atmospheric water vapor (column precipitable water), cm
:,3  IWL, integrated cloud liquid content, cm
:,4  number of 21-s values in hourly median
:,5  standard deviation of IWV, cm
:,6  standard deviation of IWL, cm



f99_micro_10min.txt         size= (3684,6)
same as micro_h, but at 10-min time resolution





f99_modcld_10min.txt         size= (4008,6)
:,1  decimal julian date  (301 to 337)
:,2  Cloud fraction, computed from ceilometer
:,3  IWL, integrated cloud liquid content, cm
:,4  IWC, integrated cloud liquid content ZERO OFFSET, cm
:,5  IWC, integrated atmospheric water vapor (column precipitable water), cm
Note this file has a larger time base because it has been interpolated to the ceilometer data.





To get this data, go to my ftp site:
ftp etl.noaa.gov 
username> anonymous
password> your email
cd /pub/et7/anonymous/cfairall/epic/epicmonitor/fall99/microwave

Included on the ftp site are the original hourly files from Duane Hazen (YYMMDDHH.new), his
descriptions (datainfo.txt, pacs.txt), and the matlab file I did the processing with (micro_red.txt). 
I have also included a second matlab file (micortxt_red.m) that will read micro_h.txt and
micro_s.txt and plot a couple of representative days.  These plots illustrate some problems with
the data.




1.  The tends to be a time-varying bias in the IWL; it doesn't give zero when it is clear buy
something like 0.003 cm (30 g/m^2).  To use this data quantitatively, this bias must be computed
and subtracted.  A file named modcld_10min.txt has been created to do this at 10-min time resolution. 
The ceilometer data was used to identify clear periods, the clear values of IWL were found and interpolated
to the entire time series.  The 3rd column of this file is the original ILW and the fourth
column is the IWL offset.  Just subtract column 4 from column 3 to remove the bias.  

2.  In the deep convection regions there are a lot of bad values caused by rain water on the
system.


microtxt_rec.m also reads in an hourly ceilometer file (epic99_cloudf_hr.txt),interpolates it to the
microwave time base, and plots the 'background' ILW values for cloudfree conditions.  This
shows the bias very well. See the figure cloudfree.jpg .