REA air sampling using the Bayreuth Whole-air REA system

using the Bayreuth Whole-air REA system

The air sampling („eddy sampling“) is managed from subroutines running

independently from the ATEM timing main sequence. However, they can be started from the front panel of the ATEM timing program. ATEM joint control serves as interface for the global variables exchanged between the different subroutines and the main sequence.

Before starting the eddy sampling procedure, first flush bags and flasks with ambient air to condition them to air, which is similar to the sample that will be stored in it.

At the beginning of each eddy sampling period, check and adjust the settings in ATEM setup. By continuously switching the definition of bag 1 as reservoir for either updrafts or downdrafts (bag 1 samples up/down) systematic errors originating from e.g. a small contamination in only one sampling path in the REA system can be avoided or at least detected.

An additional data file covering exactly the time of the eddy sampling is stored including the extension “_ES” in the filename instead of the file number.

After the sampling procedure, transfer samples from bags to flasks.

Depending on the pump voltages, pump performance and bag filling, time for the flushing and emptying may vary significantly. You can adjust the times in seconds in the corresponding subroutines on the front panel.

When using the Bayreuth Whole-air REA system with balloon bags as reservoirs always control the filling processes of the balloons and

Note:

stop the eddy sampling process by either pushing the stop button on the REA system or stopping the ATEM eddy sampling subroutine. Balloon filling and emptying needs to be monitored also during the sample transfer from bag to flask and flushing bags and flasks

procedures. Sampling, filling and flushing procedures can be stopped at any time by either stopping the corresponding subroutine (press stop button or next button) or pressing the stop button on the REA system box outside.

22

4.1 REA system connection setup

Pump 6 needs additional external 16…24 Vdc)

sampleairinlet

sonic MFM MFM

Ba g 1 Ba g 2

Valves 1-10 Pumps 3,4,5 Pumps 1 + 2 Analog Signals

↑

c

↓

c

RS232 COM1 RS232 COM2

C om p ut er + A T E M s o ftw ar e

BMC PC20TR Digital Out Analog In

REA Box Valves, Pumps, Analog PC Digital PC Analog

R E A E lect ro n ic B o x E L U B 674

Pu

R E A P um p E L U B 695

flushingairinlet

CO2H2O analyzer

F lask 1 + 2

RE A Bo x CO 2 H2 O A n al yz er E lect ro n ic Bo x

sampleairinlet

sonic MFM MFM

Ba g 1 Ba g 2

Valves 1-10 Pumps 3,4,5 Pumps 1 + 2 Analog Signals

↑

c

↓

c

RS232 COM1 RS232 COM2

C om p ut er + A T E M s o ftw ar e

BMC PC20TR Digital Out Analog In

REA Box Valves, Pumps, Analog PC Digital PC Analog

R E A E lect ro n ic B o x E L U B 674

Pu

R E A P um p E L U B 695

flushingairinlet

CO2H2O analyzer

F lask 1 + 2

RE A Bo x CO 2 H2 O A n al yz er E lect ro n ic Bo x

23

4.2 REA system technical components

NMP 830 KVDC, ryton®, viton® (FPM) Sicherheitsventile DN 8

+0.5 bar, brass, viton® (FPM) SD-30, -1…+1.5 bar, stainless steel magnesium perchlorate granulate in 200 mm x 20 mm ID glass tubes with viton® (FPM) seals

mylar® foil balloons, 45 cm, circle

(one bag reservoir consists of two balloons, each balloon is equipped with a stainless steel filler tube through the foil valve of the balloon) valve 1, 2 and dummy: 0330, 3/2 way solenoid valve, 3 mm orifice, stainless steel, viton® (FPM) valve 3 to 8: 6011A, 2/2 way solenoid valve, 2.4 mm orfice, version for analytical applications, stainless steel, viton® (FPM)

MD-110-48S-4, stainless steel, nafion®

pump 6: DC24/80S

pump 1, 3, 4: N 86 AVDC, aluminium, viton®

(FPM)

pump 2, 5: N 86 KVDC, ryton®, viton® (FPM) F-111C-HA-33-V, 6 ln/min.

stainless steel fittinge, seals: viton® (FPM) stainless steel fittinge

quick connects and ultra torr conectors seals: viton® (FPM)

SERTOflex-6 stainless steel

ACRO 50, 1.0 µm, teflon® (PTFE) type

company REA system part

University of Bayreuth, Germany connectors

Swagelock, Solon, OH, USA

connectors tubing

in REA system

KNF Neuberger GmbH, Freiburg, Germany

pumps

(profile system)

Riegler & Co. KG, Bad Urach, Germany backpressure valves

Suchy Messtechnik, Lichtenau, Germany pressure sensor

University of Bayreuth, Germany drying traps

Anagram

International, Inc., Eden Prairie, MN, USA

bags (bag1, bag2)

Bürkert, Ingelfingen, Germany

valves (V1, V2) valves (V3, V4, V5, V6, V7, V8)

Perma Pure Inc., Toms River, NJ, USA nafion gas-dryer

FÜRGUT,

Aichstetten, Germany pump (P6)

KNF Neuberger GmbH, Freiburg, Germany

pumps (P1, P3, P4,) pumps (P2, P5)

Bronkhorst Hi-Tec B.

V., Ruurlo, Netherlands mass flow meters

(MFM1, MFM2)

SERTO jacob GmbH, Fuldabrück, Germany inlet tubing

Gelman Sciences Inc., Ann Arbor, MI, USA

filter

NMP 830 KVDC, ryton®, viton® (FPM) Sicherheitsventile DN 8

+0.5 bar, brass, viton® (FPM) SD-30, -1…+1.5 bar, stainless steel magnesium perchlorate granulate in 200 mm x 20 mm ID glass tubes with viton® (FPM) seals

mylar® foil balloons, 45 cm, circle

(one bag reservoir consists of two balloons, each balloon is equipped with a stainless steel filler tube through the foil valve of the balloon) valve 1, 2 and dummy: 0330, 3/2 way solenoid valve, 3 mm orifice, stainless steel, viton® (FPM) valve 3 to 8: 6011A, 2/2 way solenoid valve, 2.4 mm orfice, version for analytical applications, stainless steel, viton® (FPM)

MD-110-48S-4, stainless steel, nafion®

pump 6: DC24/80S

pump 1, 3, 4: N 86 AVDC, aluminium, viton®

(FPM)

pump 2, 5: N 86 KVDC, ryton®, viton® (FPM) F-111C-HA-33-V, 6 ln/min.

stainless steel fittinge, seals: viton® (FPM) stainless steel fittinge

quick connects and ultra torr conectors seals: viton® (FPM)

SERTOflex-6 stainless steel

ACRO 50, 1.0 µm, teflon® (PTFE) type

company REA system part

University of Bayreuth, Germany connectors

Swagelock, Solon, OH, USA

connectors tubing

in REA system

KNF Neuberger GmbH, Freiburg, Germany

pumps

(profile system)

Riegler & Co. KG, Bad Urach, Germany backpressure valves

Suchy Messtechnik, Lichtenau, Germany pressure sensor

University of Bayreuth, Germany drying traps

Anagram

International, Inc., Eden Prairie, MN, USA

bags (bag1, bag2)

Bürkert, Ingelfingen, Germany

valves (V1, V2) valves (V3, V4, V5, V6, V7, V8)

Perma Pure Inc., Toms River, NJ, USA nafion gas-dryer

FÜRGUT,

Aichstetten, Germany pump (P6)

KNF Neuberger GmbH, Freiburg, Germany

pumps (P1, P3, P4,) pumps (P2, P5)

Bronkhorst Hi-Tec B.

V., Ruurlo, Netherlands mass flow meters

(MFM1, MFM2)

SERTO jacob GmbH, Fuldabrück, Germany inlet tubing

Gelman Sciences Inc., Ann Arbor, MI, USA

filter

24

REA sampling unit

dry air

drierite

1 l glass flask

1 l glass flask

flask fill unit 2

flushing inlet

P

P

flask fill unit 1

Mg(ClO₄)₂

Mg(ClO₄)₂

Mg(ClO₄)₂

P

MFM mass -flow-meter

REA sampling unit

dry air

drierite

1 l glass flask

1 l glass flask

flask fill unit 2

flushing inlet

P

P

flask fill unit 1

REA sampling unit

dry air

drierite

1 l glass flask

1 l glass flask

flask fill unit 2

flushing inlet

P P

P P

flask fill unit 1

MFM mass -flow-meter MFM mass

-flow-meter MFM mass

-flow-meter

Bowling, D. R., A. C. Delany, et al. (1999). "Modification of the relaxed eddy accumulation technique to maximize measured scalar mixing ratio differences in updrafts and downdrafts." Journal of

Geophysical Research D: Atmospheres 104(D)(8): 9121-9133.

Businger, J. A. and S. P. Oncley (1990). "Flux Measurement with Conditional Sampling." Journal of Atmospheric and Oceanic Technology 7: 349-352.

Ruppert, J., B. Wichura, et al. (2002). Eddy Sampling Methods, a comparison using simulation results. 15th Symposium on Boundary Layers an Turbulence, Wageningen, Netherlands, American

Meteorological Society.

25

Appendix

Example of Tube delay definitions

from GRASATEM-2003 and WALDATEM-2003

All Values are given as number of sampling intervals (= number of data rows). With a sampling frequency of 10 Hz, the length of one sampling interval is 1/10 s.

Numbers followed by * are the time lags showing a maximum cross correlation of a scalar signal (CO2 densityor event code) and the vertical wind velocity (w). Values in brackets indicate the second most frequent time lag found by evaluating maximum corss correlation for different intervals during a tube delay experiment.

Experiment Period Days of the year

GA1 141, 142

GA2 144, 145

GA3 150

WA1 - 3

177, 179, 187 188, 189, 204

Tube length ~ 4 m ~ 4 m ~ 4 m ~ 6 m

Sample air flow (MFM1) 3.0 l/min 3.0 l/min 3.0 l/min 2.58 l/min Bypass air flow (MFM2) 3.6 l/min 3.6 l/min 3.6 l/min 3.6 l/min

[1/10 s] [1/10 s] [1/10 s] [1/10 s]

Physical tube delay

differential measurement =

(= 1. – 2., see chapter 3) 8 7 11

1. inlet tube, REA system up to the valves plus the short connection tube and CO2 Analyzer and

11 (12) * 11 * 15-16 *

2. short connection tube

and CO2 Analyzer only. 3-4 * 4 (5) * 4-5 *

REA settings (.ati file) delay_for_valve_switching=

software delay used to match valve switching to the correct samples at valves V1 and V2

doy 141: 8

doy 142: 7 7 6 10

Lag in data record:

ATEM_EVAL settings REA_valve_delay =

used to match w, CO2 data with valve switching recorded in the event code

doy 141: 8 *

doy 142: 7 * 7 6 10 *

26

Note on physical delay vs. delay in data file

There is an undefined additional delay of about 0.020 to 0.120 s. This delay arises from the fact that physical measurement take place some time (about –

0.020… -120 s) before the data is read from the serial port by the ATEM subroutines during the next cycle of the ATEM main sequence. A detailed analysis is given in

“ATEM timing diagram v7.xls”. This delay is indicated in the figure below by the circle (physical measurement) and arrow (submitting data to the serial ports). The time reference 0 ms used here (also see chapter 3.2) corresponds to the start of the ATEM main sequence, in which the data is recived.

In order to match the physical tube delay to valve switching and to receive the correct setting for the software delay (delay_for valve_switching), decrease the number of the measured physical tube delay by about 0.020… 0.120 s (at 10 Hz sampling frequency i.e. -1 interval, accounting for the additional delay described above).

This value also determines the lag of rows in the data file between measured data and the event code.

Measurement: -20... -120 ms Read data: 0 ms valve setting: +800 ms (delay_for valve_switching

= 8 intervals)

reservoirs

Delay in data file write REA sampling data:

+1200 ms Measurement: -20... -120 ms Read data: 0 ms Measurement: -20... -120 ms Read data: 0 ms valve setting: +800 ms (delay_for valve_switching

= 8 intervals)

reservoirs

= 8 intervals) reservoirs

76543218 0

76543218 Delay in data file write REA sampling data:

+1200 ms

76543218 0w76543218 0

76543218

Delay in data file write REA sampling data:

+1200 ms

reservoirsup down8

1 9

27 Foto of Tube delay experiment:

2. short connection tube and CO2 Analyzer only.

28

Volumes in the series ‚University of Bayreuth, Department of Micrometeorology, Arbeitsergebnisse’

No Name Titel Date

01 Foken Der Bayreuther Turbulenzknecht 01/99

02 Foken Methode zur Bestimmung der trockenen De-position von Bor

02/99

03 Liu Error analysis of the modified Bowen ratio method

02/99

04 Foken et al. Nachtfrostgefährdung des ÖBG 03/99 05 Hierteis Dokumentation des Expertimentes Dlouha

Louka

03/99

06 Mangold Dokumentation des Experiments am Standort Weidenbrunnen, Juli/August 1998

07/99

07 Heinz, Handorf, Foken

Strukturanalyse der atmosphärischen Turbulenz mittels Wavelet-Verfahren zur Bestimmung von Austauschprozessen über dem antarktischen Schelfeis

07/99

08 Foken Comparison of the sonic anemometer Young Model 81000 during VOITEX-99

10/99

09 Foken et al. Lufthygienisch-Bioklimatische Kennzeichnung des oberen Egertales,

Zwischenbericht 1999

11/99

10 Sodemann Stationsdatenbank zum BStMLU-Projekt Lufthygienisch-Bioklimatische Kennzeichnung des oberen Egertales

03/00

11 Neuner Dokumentation zur Erstellung der

meteorologischen Eingabedateien für das Modell BEKLIMA

10/00

12 Foken et al. Dokumentation des Experimentes VOITEX-99

12/00

13 Bruckmeier et al. Documentation of the experiment EBEX-2000, July 20 to August 24, 2000

01/01

29

14 Foken et al. Lufthygienisch-Bioklimatische Kennzeichnung des oberen Egertales

02/01

15 Göckede Die Verwendung des footprint-Modells nach SCHMID (1997) zur stabilitätsabhängigen Bestimmung der Rauhigkeitslänge

03/01

16 Neuner Berechnung der Evapotranspiration im ÖBG (Universität Bayreuth) mit dem SVAT-Modell BEKLIMA

05/01

17 Sodemann Dokumentation der Software zur Bearbeitung der FINTUREX-Daten

08/02

18 Göckede et al. Dokumentation des Experiments STINHO-1 08/02 19 Göckede et al. Dokumentation des Experiments STINHO-2 12/02 20 Göckede et al. Characterisation of a complex measuring site

for flux measurements

12/02

21 Liebethal Strahlungsmessgerätevergleich während des Experimentes STINHO_1

01/03

22 Mauder et al. Dokumentation des Experiments EVA_GRIPS 03/03 23 Mauder et al. Dokumentation der Litfass-2003 und

GRASATEM-2003 Experimente

24 Thomas et al. Dokumentation des WALDATEM-2003 Experimentes

05/04

25 Göckede et al. Qualitätsbegutachtung komplexer

mikrometeorologischer Messstationen im Rahmen des VERTIKO-Projekts

11/04

26 Mauder und Foken Documentation and Instruction Manual of the

Eddy Covariance Software Package TK2 12/04 27 Herold et al. The OP-2 open path infrared gas analyser for

CO2and H2O 01/05

28 Ruppert ATEM software for Atmospheric Turbulent Exchange Measurements using Eddy

Covariance and Relaxed Eddy Accumulation Systems and Bayreuth whole-air REA system setup

04/05

Im Dokument ATEM Software for Athmospheric Turbulence Exchange Measurements using Eddy Covariance and Relaxed Eddy Accumulation Systems and Bayreuth whole-air REA system setup (Seite 21-29)