http://samos.coaps.fsu.edu

Height MattersHeight Matters

http://samos.coaps.fsu.edu

Wind, Temperature, and HumidityWind, Temperature, and Humidity

0

2

4

6

8

10

12

14

16

18

20

0 1 2 3 4 5 6

Wind speed m/s

He

igh

t

Profile

Measurements

Sys-2 buoy

WHOTS-2 June 24 2006 Hr 6

0

2

4

6

8

10

12

14

16

18

20

24.4 24.6 24.8 25.0 25.2 25.4

Potential Temperature °C

Profile

Measurements

Surface

Sys-2 buoy

Assman

0

2

4

6

8

10

12

14

16

18

20

14 15 16 17 18 19 20Humidity g/kg

Profile

Measurements

Surface

Sys-2 buoy

Assman

http://samos.coaps.fsu.edu

-25 -20 -15 -10 -5 0 5 10 15 20 251011.15

1011.2

1011.25

1011.3

1011.35

Air Temp (C)

Pre

ssur

e(m

b)

Air Temperature Effect

0 5 10 15 20 25 30 35 40 45 500

1

2

3

4

5

6

Sensor Ht (m)

Ps

- 10

10(m

b)

Surface Pressure Calculation

Ps = Pze(gz/RaT)

Pz = Station pressure (mb)Ra = Universal Constant (J/kgK)… 287.05;T = Temperature (K)g = gravity (m/s)… 9.81; z = height of pressure sensor (m)Ps = sea level pressure (SLP mb)

Rough guesstimate 1mb = 10m

SLP >= Station Pressure

Station Pressure to Sea Level calculation

7.67m

2.946m

2.883m

Deck2

Deck3

Deck1

Pilot House

7/11/2013 Measurements

Ship’s pressure sensor

PSD dynamic pressure port and sensor14.388m above water

Ship dynamic pressure port12.02m above water

Ship ~1.38 mb @ 25oCPSD ~1.66 mb @ 25oC

NWS barometer

Ship pressure12.02m above water

65”

Tygon tubing to dynamic pressure port

Ship pressure sensorPSD3 Hand Held barometer

Prior to resetting Vaisala unitw/30m offset

Ship pressure sensorVaisala PTB330

PSD3 Hand Held barometer

After resetting Vaisala unit7/11/2013 ~0115UTC

NWS barometer last calibrated 7/25/2011Appears to be reading Sea level pressure~.3-.5 mb higher than Vaisala

Sea Level

Station

http://samos.coaps.fsu.edu

PressurePressure

http://samos.coaps.fsu.edu

Accuracy TargetsAccuracy Targets

http://samos.coaps.fsu.edu

Applying Heights in the FieldApplying Heights in the Field

Image Courtesy NOAA OAR

http://samos.coaps.fsu.edu

Questions?Questions?

http://samos.coaps.fsu.edu

Pressure ExercisePressure Exercise

• Using the equation • Given

• pz = 1010 hPa

• T = 290 K• g = 9.81 m s-2

• Ra = 287.05 J kg-1 K-1

• e = 2.718281

• Calculate the surface pressure (ps) for your vessel using your barometer height (z).

• Calculate the pressure difference (ps – pz) and add it to the list on the whiteboard.

} Pressure and temperature at a given time

} Constants