Mode-S Enhanced Surveillance

Introduction

A novel method to measure wind and temperature is related to tracking and ranging by an enhanced surveillance (EHS) air traffic control (ATC) radar.

Modern aircraft carry sensors to measure the Mach number (using pitotstatic probe) and the total air temperature (T). An EHS radar interrogates all aircraft in sight in a selective mode (Mode-S), on which the aircraft replies with a message containing, for example, magnetic heading, airspeed and Mach number. From this information wind and temperature can be extracted.

Mode-S EHS data

Description

The data description is available here: http://mode-s.knmi.nl/data/

Access

Access to MUAC Mode-S EHS data can be requested from KNMI by signing a Non Disclosure Agreement. Send an e-mail to mode-s@knmi.nl with a request like this:

Dear Sir/Madam,

On behalf of MyNHMS, My NHMS Full Name, I would like to request access to Mode-S EHS derived meteorological data made available by Maastricht Upper Area Centre (MUAC) of EUROCONTROL and KNMI.

MyNHMS intend to use these data for NWP (Numerical Weather Prediction) research and development with the hope of assimilating these data in operational NWP system(s) in the near future.

My contact details are as follows:
Name
Address
e-mail
Telephone

Yours Sincerely,
Name

Prepare the BUFR data

ftp server

Mode-S EHS bufr, netCDF and ASCII data are available on the KNMI ftp server, ftpservice.knmi.nl. The ASCII and netCDF file contain all observations, while BUFR file contains about 10% of the available observations. The thinning is for descending and ascending aircraft evry 300m in pressure altitude, and for level flight one observation per 2 minutes.

BUFR data sub-category change

At present the BUFR-sub category needs to be changed: bufr_set, an ecCodes tool, can be used to change the data sub-category from 146 to 147. This is required by HARMONIE.

bufr_set -sdataSubCategory=147 Mode-S-EHS_MUAC_20170507_2345.bufr Mode-S-EHS_MUAC_20170507_2345_147.bufr

HARMONIE changes

scr/include.ass

In scr/include.ass should be edited to "switch on" the use of Mode-S EHS data:

export MODESEHS_OBS=1          # Mode-S EHS

Processing using Bator

The BUFR template (WMO AMDAR v7) used by your Mode-S EHS data should be defined in the param.cfg file used by Bator. param.cfg files for Bator are in the nam namelist directory. The modes param.cfg template should be something like this:

BEGIN amdar

END

Processing using Oulan

The processing of Mode-S EHS BUFR using Oulan is controlled by the following namelist entry in scr/Oulan:

LMODES=.FALSE.

Thinning of Mode-S

Thinning of a bufr file

A collection of python scripts which directly thin the Mode-S csv and bufr file is uploaded here https://gitlab.com/haandes/emaddc-public.

E.g. the emaddcc-thinning4.py script works with the large Mode-S_EMADDC_KNMI_oper_${DTG}.bufr file and thins the data in 4 dimensions, horizontal, vertical and in observation time closest to analysis time. Emaddcc-thinning4.py currently assumes valid temperature and wind observations at the same time and fix vertical thinning intervals of:

[300, 300, 600, 1000] m

which corresponds to the heights of the lowest, second lowest, third lowest and all above boxes. The horizontal box width is variable and in the following example 40 km.

The .py script is triggered in scr/Prepare_ob, with:

  nMsgs=`bufr_count $OBDIR/Mode-S_EMADDC_KNMI_oper_${DTG}.bufr`
  time python3 $HM_LIB/scr/emaddcc_thinning4.py --infile $OBDIR/Mode-S_EMADDC_KNMI_oper_${DTG}.bufr --box_width 40 --DTG $DTG --nMsgs $nMsgs --outfile emaddcc_thinned.bufr
  cat emaddcc_thinned.bufr  /dev/null >> $BUFRFILE

It takes about 1:35 min on Atos-Bologna and results in reduction of Mode-S data by a factor of 4-5.