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Dew Point Climatology DewDew PointPoint ClimatologyClimatology ForFor SoutheastSoutheast Minnesota,Minnesota, NortheastNortheast Iowa,Iowa, andand WesternWestern WisconsinWisconsin WFOWFO LaLa CrosseCrosse ClimatologyClimatology SeriesSeries #17#17 Mary-Beth Schreck Dan Baumgardt NWS La Crosse, WI ObjectivesObjectives •• BecomeBecome familiarfamiliar withwith climatologicalclimatological hourlyhourly TdTd curvescurves •• UnderstandUnderstand howhow windwind directiondirection affectsaffects TdTd •• BecomeBecome awareaware ofof thethe uniqueunique characteristicscharacteristics ofof KLSEKLSE andand KRSTKRST DataData MethodologyMethodology •• 19611961--19951995 SurfaceSurface HourlyHourly ObservationsObservations – NCDC SAMSON CDROM 1960-1990 – NCDC HUSWO CDROM 1990-1995 – 1965-1972 removed due to station closures: 23 total years possible. • LSE (17) – No 62,63,80,81,85, 91. Removed June 78,82,95. • RST (20) – No 78, 80, 90 • ALO (18) – No 73,74,80,81 • EAU (19) – No 78-81 • MSN: (23) • MCW: (17) – No 73,74,78-81 DataData MethodologyMethodology •• HourlyHourly dewpointdewpoint calculatedcalculated overover thethe periodperiod ofof recordrecord forfor everyevery dayday ofof thethe yearyear atat eacheach ofof thethe sixsix sites.sites. AlsoAlso donedone hourlyhourly forfor everyevery month.month. •• AverageAverage monthlymonthly dewpointdewpoint categorizedcategorized byby windwind directiondirection waswas calculatedcalculated forfor eacheach sitesite byby month.month. •• AA groupgroup averageaverage waswas calculatedcalculated byby averagingaveraging thethe thethe datadata fromfrom eacheach ofof thethe sixsix sites.sites. •• AA ‘‘perturbationperturbation’’ oror anomalyanomaly (Td(Td’’)) waswas createdcreated byby subtractingsubtracting thethe sitesite dewpointdewpoint (Td)(Td) fromfrom thethe groupgroup averageaverage (Td(Td aveave).). TdTd’’ == TdTd aveave -- TdTd – This perturbation, or Td’, is used to show where the dewpoint varies from the group average. – Shows local or site specific differences more clearly. SynopticSynoptic vs.vs. LocalLocal SignalsSignals •• AllAll monthsmonths –– whenwhen therethere isis aa synopticsynoptic signal,signal, itit dominatesdominates •• WinterWinter monthsmonths –– synopticsynoptic scalescale tendstends toto havehave moremore influenceinfluence •• SummerSummer monthsmonths –– locallocal signalsignal hashas moremore influenceinfluence – Exchange between soil moisture and water vapor in air – Crop coverage vs. moisture in air – River as moisture source JanuaryJanuary -- JuneJune Average Hourly Dewpoint - January La Crosse, Wisconsin 12 2.0 11 1.5 10 1.0 0.5 9 Average Hourly Dewpoint - February 0.0 8 La Crosse, Wisconsin -0.5 Dewpoint (F) 7 -1.0 KLSE vs.Group 17 2.0 6 -1.5 (F) Difference Dewpoint 16 1.5 5 -2.0 1.0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 15 0.5 Hour (LT) 14 Average Hourly Dewpoint - March 0.0 13 La Crosse, Wisconsin KLSE Td KLSE Td vs. Group -0.5 Dewpoint (F) Dewpoint 12 KLSE vs. Group -1.0 27 3.0 11 -1.5 Difference (F) Dewpoint 2.5 26 2.0 10 -2.0 25 1.5 123456789101112131415161718192021222324 1.0 Hour (LT) 24 0.5 0.0 23 -0.5 KLSE Td KLSE Td vs. Group Dewpoint (F) -1.0 22 -1.5 KLSE vs. Group 21 -2.0 (F) Difference Dewpoint -2.5 Average Hourly Dewpoint - April 20 -3.0 La Crosse, Wisconsin 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 Hour (LT) 37 3.0 2.5 KLSE Td KLSE Td vs. Group 36 2.0 1.5 35 1.0 Average Hourly Dewpoint - May 34 0.5 0.0 La Crosse, Wisconsin 33 -0.5 Dewpoint (F) -1.0 50 3.0 32 KLSE vs.Group -1.5 2.5 31 -2.0 (F) Difference Dewpoint 49 2.0 -2.5 Average Hourly Dewpoint - June 48 1.5 30 -3.0 1.0 La Crosse, Wisconsin 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 47 0.5 0.0 Hour (LT) 46 -0.5 60 2.0 Dewpoint (F) -1.0 45 KLSE vs.Group 1.5 KLSE Td KLSE Td vs. Group -1.5 59 Dewpoint Difference (F) Difference Dewpoint 1.0 44 -2.0 58 -2.5 0.5 43 -3.0 57 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 0.0 56 Hour (LT) -0.5 Dewpoint (F) 55 KLSE vs. Group -1.0 KLSE Td KLSE Td vs. Group DifferenceDewpoint (F) 54 -1.5 53 -2.0 123456789101112131415161718192021222324 Hour (LT) KLSE Td KLSE Td vs. Group JulyJuly -- DecemberDecember Average Hourly Dewpoint - July La Crosse, Wisconsin 65 2.0 64 1.5 63 1.0 Average Hourly Dewpoint - August 0.5 62 La Crosse, Wisconsin 0.0 61 -0.5 64 2.0 Dewpoint (F) 60 KLSE vs. Group -1.0 63 1.5 59 -1.5 (F) Difference Dewpoint 62 1.0 58 -2.0 0.5 61 123456789101112131415161718192021222324 0.0 60 Hour (LT) -0.5 Average Hourly Dewpoint - September Dewpoint (F) 59 KLSE vs. Group La Crosse, Wisconsin KLSE Td KLSE Td vs. Group -1.0 58 -1.5 (F) Difference Dewpoint 56 2.0 57 -2.0 123456789101112131415161718192021222324 55 1.5 1.0 Hour (LT) 54 0.5 53 KLSE Td KLSE Td vs. Group 0.0 52 -0.5 Average Hourly Dewpoint - October Dewpoint (F) 51 KLSE vs.Group La Crosse, Wisconsin -1.0 50 -1.5 (F) Difference Dewpoint 43 2.0 49 -2.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 42 1.5 Hour (LT) 1.0 41 0.5 KLSE Td KLSE Td vs. Group 40 0.0 Average Hourly Dewpoint - November 39 -0.5 La Crosse, Wisconsin Dewpoint (F) 38 KLSE vs. Group -1.0 37 -1.5 Dewpoint Difference (F) 30 2.0 36 -2.0 29 1.5 123456789101112131415161718192021222324 28 1.0 Average Hourly Dewpoint - December Hour (LT) 0.5 27 La Crosse, Wisconsin 0.0 KLSE Td KLSE Td vs. Group 26 -0.5 17 2.0 Dewpoint (F) 25 KLSE vs. Group -1.0 16 1.5 24 -1.5 (F) Difference Dewpoint 1.0 15 23 -2.0 0.5 14 123456789101112131415161718192021222324 0.0 Hour (LT) 13 -0.5 Dewpoint (F) 12 KLSE vs. Group KLSE Td KLSE Td vs. Group -1.0 11 -1.5 (F) Difference Dewpoint 10 -2.0 123456789101112131415161718192021222324 Hour (LT) KLSE Td KLSE Td vs. Group TheThe BigBig PicturePicture (All(All Sites):Sites): HourlyHourly DewDew PointsPoints •• LargerLarger variationvariation overover 2424 hourshours duringduring thethe WinterWinter monthsmonths thanthan SummerSummer monthsmonths ExerciseExercise -- JanuaryJanuary Average Hourly Dewpoint - January 12 2.0 11 1.5 1.0 10 0.5 9 0.0 8 -0.5 Dewpoint (F) 7 Difference (F) -1.0 6 -1.5 Site vs. Group Dewpoint 5 -2.0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 Hour (LT) JanuaryJanuary –– TdTd variationvariation 66ooFF Average Hourly Dewpoint - January La Crosse, Wisconsin 12 2.0 11 1.5 ) 1.0 ) 10 0.5 9 0.0 8 -0.5 Dewpoint (F Dewpoint 7 -1.0 KLSE vs. Group 6 -1.5 Dewpoint Difference (F 5 -2.0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 Hour (LT) KLSE Td KLSE Td vs. Group ExerciseExercise -- JulyJuly Average Hourly Dewpoint - July 65 2.0 64 1.5 1.0 63 0.5 62 0.0 61 -0.5 Dewpoint (F) 60 Difference (F) -1.0 59 -1.5 Site vs. Group Dewpoint 58 -2.0 123456789101112131415161718192021222324 Hour (LT) JulyJuly –– TdTd variationvariation 33oo FF Average Hourly Dewpoint - July La Crosse, Wisconsin 65 2.0 64 1.5 ) 1.0 ) 63 0.5 62 0.0 61 -0.5 Dewpoint (F 60 KLSE vs. Group -1.0 59 -1.5 (F Difference Dewpoint 58 -2.0 123456789101112131415161718192021222324 Hour (LT) KLSE Td KLSE Td vs. Group Exercise:Exercise: LabelingLabeling Mixing/ET battle Average Hourly Dewpoint - July ET Condensation Sunset La Crosse, Wisconsin Stable PBL Begins Sunrise ET tiny ET still occurring 65 64 63 62 61 Dewpoint (F) Dewpoint 60 59 58 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 Hour (LT) KLSE Td JulyJuly –– DailyDaily CycleCycle Average Hourly Dewpoint - July La Crosse, Wisconsin 65 2.0 64 Sunset 1.5 ) Co nd Mixing/ET battle en 1.0 E sa ) 63 T t tin io ET y n 0.5 62 Stable PBL Begins ET still occurring 0.0 61 Sunrise -0.5 Dewpoint (F 60 KLSE vs. Group -1.0 59 -1.5 (F Difference Dewpoint 58 -2.0 123456789101112131415161718192021222324 Hour (LT) KLSE Td KLSE Td vs. Group ExerciseExercise –– WetWet andand DryDry Average Hourly Dewpoint - July La Crosse, Wisconsin 65 2.0 64 Sunset 1.5 ) Co nd Mixing/ET battle en 1.0 E sa ) 63 T t tin io ET y n 0.5 62 Stable PBL Begins ET still occurring 0.0 61 Sunrise -0.5 Dewpoint (F 60 KLSE vs. Group -1.0 59 -1.5 (F Difference Dewpoint 58 -2.0 123456789101112131415161718192021222324 Hour (LT) KLSE Td KLSE Td vs. Group Answers:Answers: WetWet andand DryDry YearsYears Hourly Dewpoint - July - La Crosse WI 65 64 63 62 61 Dewpoint (F) Dewpoint 60 59 58 0 2 4 6 8 1012141618202224 Hour (LST) LSE July LSE Wet 1976 - Dry RealReal LifeLife ExampleExample –– JulyJuly 20042004 Hourly Dew point - July - La Crosse WI 72 67 LSE July 26 2004 Ridge LSE July Average Td 62 LSE July 10 2004 Ridge Dewpoint (F) Dewpoint 57 After Rains 52 0 6 12 18 24 Hour (LST) ARXARX ForecastForecast TrendsTrends Normal Diurnal cycle (condensation) Wrong trend Southerly NW, post-frontal Moisture Advection dry air advection. 0Z 4Z Non-climo diurnal curve TheThe BigBig PicturePicture (All(All Sites):Sites): HourlyHourly DewDew PointsPoints •• LargerLarger variationvariation overover 2424 hourshours duringduring thethe WinterWinter monthsmonths thanthan SummerSummer monthsmonths •• TdTd risesrises duringduring eveningevening hourshours fromfrom AprilApril throughthrough October;October; 99 toto 1010 pmpm peakpeak –– VegetationVegetation relatedrelated EveningEvening TdTd RisesRises Average Hourly Dewpoint - April La Crosse, Wisconsin 37 3.0 Average Hourly Dewpoint - May 2.5 36 2.0 La Crosse, Wisconsin 1.5 35 1.0 34 0.5 50 3.0 Average Hourly Dewpoint - June 0.0 2.5 49 33 -0.5 2.0 La Crosse, Wisconsin 1.5 Dewpoint (F) -1.0 48 32 KLSE vs.Group -1.5 1.0 60 2.0 47 0.5 31 -2.0 Dewpoint Difference (F) -2.5 0.0 59 1.5 46 30 -3.0 -0.5 1.0 Dewpoint (F) Dewpoint -1.0 58 1 2 3 4 5 6 7 8 9 101112131415161718192021222324 45 KLSE vs.
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