UBCATSC3032016W
Lab5–Barometry(/77)
LearningGoals
Bytheendofthislab,youshouldbeableto:
1. Beconfidentinyourhandlingofthephysicalsensorsandsoftwarecovered
inthislab.
2. Read,interpret,andcomparethepressurefromdifferentbarometers.
3. Applyappropriatecorrectionstorawpressuredata.
4. Convertbetweenpressureunits.
5. Reinforcethelearninggoalsfromthelectureanddemo.
Background
Barometrylecture
WMOCh.3
Harrison:Ch.7
Safety
TheEco-cellibarometerisveryfragile,pleasedonottouchit.Also,nomorethan
fourpeopleatatimeshouldsurrounditwhiletakingtheirreadings.
Method
Manuallyrecordingpressuredatafrommultiplebarometersand
manipulatingthedata.
Equipment:
• Eco-cellibarometer(stationpressure)
• Kestrelpocketweathertrackerbarometerx2(SLP)
• RMYoung61205Vbarometer(withlaptop/datalogger)(stationpressure)
• ESBrooftopweatherstationbarometer(seeconsole)(SLP)
• YVRairportaltimetersetting:https://flightplanning.navcanada.ca/cgibin/CreePage.pl?Langue=anglais&NoSession=NS_Inconnu&Page=Foreobs/metar-taf-map&TypeDoc=html(SLP;searchCYVR,andchoose
“standard”or“plainlanguage”dependingonyourfamiliaritywithreading
METARs;youarelookingforaltimetersettingininchesofHg)
1. Manuallyrecordpressurefromeachofthese6barometersevery15minutes,
approximatelyonthequarter-hourmark.DatafromtheESBrooftopstation
and the RM Young barometer will be automatically saved so read the
pressurefromtheothersensorsbeforethesetwoeachtime.(Youcancheck
your manual observations against the automated ones when we post them
afterthelab.)
1
2. Youshouldrecordpressuredataaminimumof6timesfromeachstation(i.e.
atleast1.5hours).
3. Remembertorecordthetimeofyourobservation.
ThefollowingcorrectionsshouldbeappliedtoeachsensorAFTERyourecordraw
data:
• applygravitycorrectiontotheEco-cellibarometer
• applysea-levelreductiontotheRMYoungANDtheEco-cellibarometer
• nocorrectionsfortheKestrelsandtheESBrooftopstation(theyhavebeen
correctedforelevationalreadyanddisplaysealevelpressure)
• convertallreadingsintokPa(iftheyarenotalready)
Somepotentiallyhelpfulcorrectionequations:
• Lecturenoteequations(slides23-27,43-46)
• WMONo.8eq.3.2,equationsinAnnex3.A
LabReport(/30)
Inthelabreport,youshouldincludethefollowing:
• onegraphoftherawdata:comparethe6sensorsonthesamegraph(check
yourunits)
• separategraphofthecorrecteddata:comparethe6sensorsonthesame
graph
• separategraphshowingthedifferencebetweenrawandcalibrateddata,if
thereisasignificantdifference(0.1hPaandover)
• anyothergraphsshowinginterestingtrendsorobservationsinthedata,if
applicable
• listhowyoucorrectedyourdatawhereapplicable
• listanypotentialerrorsandassumptionsyoumade
• a1pagemax.discussionaboutyourgraphedresults(whatdoyouthinkwas
theactualsea-levelpressure,whythebarometersmightbereading
differentlyfromeachother,anyoutlyingdata,etc.)
2
LabQuestions(basedonlectureandreadings)
1. What was the value of the gravity correction(s)? Did it make a difference
whencomparedtothesensor’ssignificantfigures?/2
2. Whatwasthevalueofthesea-levelreduction?Diditmakeadifferencewhen
comparedtothesensor’ssignificantfigures?/2
3. Whichbarometerdoyouthinkisthemostaccurateandwhy?/2
4. Whichbarometerdoyouthinkhasthehighestresolutionandwhy?/2
5. Whichbarometerdoyouthinkistheleastaccurateandwhy?/2
6. Whichbarometerdoyouthinkhasthelowestresolutionandwhy?/2
7. Whenyouadjustyourpressurereadingtosealevel,e.g.withtheRMYoung
61205VandtheEco-celli,whyisyouranswerprobablydifferentthanthesea
level pressure reported at YVR airport? (hint: think about the equation(s)
used,anyassumptionswearemaking,andweatherconditions)/3
8. Forwhatsituationsisgravitycorrectionimportantforpressure
measurements,andforwhatsituationsisitnot?(Shortanswer,inyourown
words.)/2
9. Calculate(onaspreadsheet)andplotthevariationofsea-levelgravitational
accelerationwithlatitude.(Hint,useeq.3.A.6fromWMO-8chapter3,annex
3.A)/4
10. ForthelatitudeofVancouver,plotlocalgravitationalaccelerationgvs
elevationHabovesealevelfor
(a)overlandhavingterrainelevationof500m;/2
(b)overtheoceanofdepth1km;and/2
(c)atashorelineata50%mixoflandfrom(a)andoceanfrom(b)./2
(Hint,useslide27andeqs.3.A.7-9fromWMO-8chapter3,Annex3.A)
11. Compare(discuss,plotusingaspreadsheet)theequationsforpressure
reductiontosealevelfortheWMOequationsinWMO-8Chapter3,vs.the
reductionequationfromStull’stextbook(aspresentedinLecture,andinthe
lecturenotesonline;seeslide46)./4
3
12. Withrespecttothemercurybarometer,howmuchinaccuracycanwe
tolerateinthemeasurementoftemperatureifwewantthepressureerror≤
0.05hPa?Assumethepressureis960hPa./3
13. Namethreecorrectionscommonlyusedwithamercurybarometer./3
14. Calculatethestaticsensitivityofamercurybarometer.Howcouldyou
increasethestaticsensitivityofamercurybarometer?/3
15. Whatisthedynamicwinderrorwhenthewindspeedis20ms-1?Whydowe
needtotaketemperatureintoaccountwhencalculatingthedynamicwind
errorforveryhighwindspeeds?/3
16. Whatistherawoutputforthefollowingsensors:amercurybarometer,and
ananeroidbarometer?/2
17. Whyhaveaneroidbarometerstendedtoreplacemercurybarometers?/2
4