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Collection and analysis of condensation nuclei counter measurements in the Arabian Gulf and the Gulf of Oman
~ Pergamon
PH: 50021-8502(96)00086-9
J. Aerosol Sci•• Vol. 27.Suppl. I. pp. 527-528. 1996 Copyrighl 0 1996 E1sevtcr ScieDcc LId Printed in 0 ...1 Britain. All nghU rescr\'ed 0021-8502/96$1$.00 + 0.00
COLLECfION AND ANALYSIS OF CONDENSATION NUCLEI COUNTER MEASUREMENTS IN THE ARABIAN GULF AND THE GULF OF OMAN ANDREAS K. GOROCH NavalResearch Laboratory, Marine Meteorology Division, Monterey, CA 93943 USA
KEYWORDS Visibility, Aerosol Concentration, Condensation Nuclei, Arabian Gulf
The concentration of aerosol particles in the atmosphere has a strongeffect on optical propagation in the visible and infrared frequencies. Aerosol particles cause most of the extinction of a signal in the visible wavelengths, as well as being important in the near infrared and mid-infrared wavelength regions. The purpose of this document is to describe measurements made aboardship duringthe US Navy SHAREM 110-1 exercise from 5 February to 18February, 1995. The measurements included standard meteorology, as well as total condensation nuclei (CN)concentrations duringpre-shamal and shamal conditions in the Arabian Gulf, and duringcalm winterconditions in the Gulf of Oman. Furtherdetails of the synoptic and local weather conditions are published elsewhere (Byers, 1995). Total condensation nuclei concentrations weremeasured aboard the US Navy guided missilecruiser USS Lake Erie (CG70). The particles were measured with an Environment One condensation nuclei counter. The air intakewas located on the bridge of the ship, approximately 25 m above the waterline on an HF antenna, 2 m forward of the main bridge superstructure. The intake was connected to the counter by 16mof Y2 inchTygon tubing. Data were recorded as one minute averages of signal voltage on a PC. The voltages wereconverted to concentrations using manufacturer's calibrations. The instrument voltage tended to be anomalous immediately after a scalechange- these measurements around the scale change werenot used in the analysis. The counts were further averaged over a 10 minute interval, corresponding to the 10minute averaging of the meteorological data. Although the CN counterair intake was mounted on the bridge, well forward of the ship stacks, the influence of ship emissions was quite marked, and seemed to correspond to when relative wind was from 1500 to 2100 relative to the ship course. These data were not studied further to identify sources and characteristics of the effluents. The aerosol data weresupplemented by wind, temperature, and humidity measurements taken at the bow of the ship, approximately 4 m abovedeck and 12 m above the water line. The measurements were separated into two geographic regions, the first in the Arabian Gulf, the second in theGulfof Oman. The Arabian Gulf measurements were obtainedduring the passage of a wintertime shamal event characterized by changedwinddirections, increased wind speed, and drying of the atmosphere. The lattermeasurements wereseparated into periods,preshamal and shamaI. 827
Abstracts of the 1996 European Aerosol Conference
S28
The pre-shamal CN concentrations were observed to be in the range on 1,000 particles/ml, somewhat similar to background CN concentrations observed in other calm marine regions (Fig. 1). The concentration increased 10 dramatically with the onset of the shamal to an average I concentration of 80,000 particles/ml (Fig.2). This seemed to • be associated with the increased sea state, as well as 7 possible advection of desert particles into the Arabian Gulf. f e £. During the transit from the Arabian Gulf to the Gulf )11 of Oman, the weather conditions became relatively calm, ~ • with general offshore upper level flow and low relative ... :I humidity (30-50%), even though measurements were 2 approximately 20 miles from the nearest shore. The CN concentrations were measured to be 20,000 particles/ml, o lUll 1300 14.00 IS.OO 1600 17.00 11.00 higher than those observed in the Arabian Gulf pre-shamal FIg. 1. Pr...hamal perIod In observations. This is consistent with advection of some the Areblan Gulf. 5 Feb 95. desert aerosol. The CN observations were used together with wind. temperature. and humidity observations £.80 to infer parameterization parameters of a tri-modal maritime aerosol model (Gathman and Davidson, 11993). The CN counts were assumed to describe f.2!J 10 the complete aerosol concentration of particles O':2~ ".)f 10.. lUll UI1 IU4 1S.:16 smaller than 0.03 micrometers in radius; the three Flg.2. Aerolol co~l::ntratlon. during mode parameters were retrieved using a ahamal period, ArabIan GUlf, 10 Fib 95. methodology suggested by Battalino (1995). The resulting concentrations were used to calculate optical visibility. The visibility was consistent with the observations recorded in the ship log.
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ACKNOWLEDGMENTS The support of the study sponsor. Space and Naval Warfare Systems Command, Program Element 0603207N, is gratefully acknowledged. REFERENCES Battalino, Terry E.• 1995: Condensation Nuclei Air Mass Parameter of the Navy Aerosol Model. Geophysics Technical Note no. 160. Naval Air Warfare Center-WPNS, Point Mugu. CA Byers, David J., 1995: Synoptic and Mesoscale Influences on Refraction During SHAREM 110, MS Thesis, US Naval Postgraduate School, Monterey , CA Gathman, Stuart. and Davidson. K.L.. 1993: The Navy Oceanic Vertical Aerosol Model, NRA t 634. Naval Command. Control and Ocean Surveillance Center, RDTE Division, San Diego, CA
PH: 50021-8502(96)00086-9
J. Aerosol Sci•• Vol. 27.Suppl. I. pp. 527-528. 1996 Copyrighl 0 1996 E1sevtcr ScieDcc LId Printed in 0 ...1 Britain. All nghU rescr\'ed 0021-8502/96$1$.00 + 0.00
COLLECfION AND ANALYSIS OF CONDENSATION NUCLEI COUNTER MEASUREMENTS IN THE ARABIAN GULF AND THE GULF OF OMAN ANDREAS K. GOROCH NavalResearch Laboratory, Marine Meteorology Division, Monterey, CA 93943 USA
KEYWORDS Visibility, Aerosol Concentration, Condensation Nuclei, Arabian Gulf
The concentration of aerosol particles in the atmosphere has a strongeffect on optical propagation in the visible and infrared frequencies. Aerosol particles cause most of the extinction of a signal in the visible wavelengths, as well as being important in the near infrared and mid-infrared wavelength regions. The purpose of this document is to describe measurements made aboardship duringthe US Navy SHAREM 110-1 exercise from 5 February to 18February, 1995. The measurements included standard meteorology, as well as total condensation nuclei (CN)concentrations duringpre-shamal and shamal conditions in the Arabian Gulf, and duringcalm winterconditions in the Gulf of Oman. Furtherdetails of the synoptic and local weather conditions are published elsewhere (Byers, 1995). Total condensation nuclei concentrations weremeasured aboard the US Navy guided missilecruiser USS Lake Erie (CG70). The particles were measured with an Environment One condensation nuclei counter. The air intakewas located on the bridge of the ship, approximately 25 m above the waterline on an HF antenna, 2 m forward of the main bridge superstructure. The intake was connected to the counter by 16mof Y2 inchTygon tubing. Data were recorded as one minute averages of signal voltage on a PC. The voltages wereconverted to concentrations using manufacturer's calibrations. The instrument voltage tended to be anomalous immediately after a scalechange- these measurements around the scale change werenot used in the analysis. The counts were further averaged over a 10 minute interval, corresponding to the 10minute averaging of the meteorological data. Although the CN counterair intake was mounted on the bridge, well forward of the ship stacks, the influence of ship emissions was quite marked, and seemed to correspond to when relative wind was from 1500 to 2100 relative to the ship course. These data were not studied further to identify sources and characteristics of the effluents. The aerosol data weresupplemented by wind, temperature, and humidity measurements taken at the bow of the ship, approximately 4 m abovedeck and 12 m above the water line. The measurements were separated into two geographic regions, the first in the Arabian Gulf, the second in theGulfof Oman. The Arabian Gulf measurements were obtainedduring the passage of a wintertime shamal event characterized by changedwinddirections, increased wind speed, and drying of the atmosphere. The lattermeasurements wereseparated into periods,preshamal and shamaI. 827
Abstracts of the 1996 European Aerosol Conference
S28
The pre-shamal CN concentrations were observed to be in the range on 1,000 particles/ml, somewhat similar to background CN concentrations observed in other calm marine regions (Fig. 1). The concentration increased 10 dramatically with the onset of the shamal to an average I concentration of 80,000 particles/ml (Fig.2). This seemed to • be associated with the increased sea state, as well as 7 possible advection of desert particles into the Arabian Gulf. f e £. During the transit from the Arabian Gulf to the Gulf )11 of Oman, the weather conditions became relatively calm, ~ • with general offshore upper level flow and low relative ... :I humidity (30-50%), even though measurements were 2 approximately 20 miles from the nearest shore. The CN concentrations were measured to be 20,000 particles/ml, o lUll 1300 14.00 IS.OO 1600 17.00 11.00 higher than those observed in the Arabian Gulf pre-shamal FIg. 1. Pr...hamal perIod In observations. This is consistent with advection of some the Areblan Gulf. 5 Feb 95. desert aerosol. The CN observations were used together with wind. temperature. and humidity observations £.80 to infer parameterization parameters of a tri-modal maritime aerosol model (Gathman and Davidson, 11993). The CN counts were assumed to describe f.2!J 10 the complete aerosol concentration of particles O':2~ ".)f 10.. lUll UI1 IU4 1S.:16 smaller than 0.03 micrometers in radius; the three Flg.2. Aerolol co~l::ntratlon. during mode parameters were retrieved using a ahamal period, ArabIan GUlf, 10 Fib 95. methodology suggested by Battalino (1995). The resulting concentrations were used to calculate optical visibility. The visibility was consistent with the observations recorded in the ship log.
...
-
,....
1:
f:
I;
ACKNOWLEDGMENTS The support of the study sponsor. Space and Naval Warfare Systems Command, Program Element 0603207N, is gratefully acknowledged. REFERENCES Battalino, Terry E.• 1995: Condensation Nuclei Air Mass Parameter of the Navy Aerosol Model. Geophysics Technical Note no. 160. Naval Air Warfare Center-WPNS, Point Mugu. CA Byers, David J., 1995: Synoptic and Mesoscale Influences on Refraction During SHAREM 110, MS Thesis, US Naval Postgraduate School, Monterey , CA Gathman, Stuart. and Davidson. K.L.. 1993: The Navy Oceanic Vertical Aerosol Model, NRA t 634. Naval Command. Control and Ocean Surveillance Center, RDTE Division, San Diego, CA