radiosonde temperature, humidity, and pressure response at low temperatures stephen r. hudson,...
Post on 21-Dec-2015
214 views
TRANSCRIPT
![Page 1: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/1.jpg)
RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE
RESPONSE AT LOW TEMPERATURES
Stephen R. Hudson, Michael S. Town,
Von P. Walden, and Stephen G. Warren
24 June 2003
![Page 2: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/2.jpg)
Introduction
• Vaisala RS80 and AIR 4A and 5A radiosondes were tested during summer and winter at South Pole.
• Their response to sudden, large changes in temperature and humidity was characterized.
• Some data were collected with the RS80s to characterize their response to smaller, more gradual changes in temperature, humidity and pressure.
![Page 3: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/3.jpg)
Large, Sudden Changes• Moved sondes from inside to outside and recorded response of reported temperature (T), humidity (RH) and pressure (P).• Usually building was heated, with an indoor T of –5° to +25°C.
• A couple tests were done with an unheated building, with indoor T between –43° and –56°C.• Outside T ranged from -24° to –71°C.• Range of T differences was 11 to 94 K.
![Page 4: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/4.jpg)
0 10 20 30 40 50 60 70-70
-60
-50
-40
-30
-20
-10
0
10
20
RS80 Temperature Response 2001/09/20
Elapsed time (seconds)
Te
mp
era
ture
(C
)
Reported TemperatureExponential Decay Fit
= 4.7 s
RS80 Temperature Response
![Page 5: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/5.jpg)
RS80 Temperature Response
Minimum 2.6 s
Median 5.4 s
Mean 5.9 s
Maximum 10.9 s
• Reported temperature responded with a simple exponential decay.
• Exponential-decay time constants ranged from 2.6 to 10.9 seconds, with a mean of 5.9 seconds.
• There was no apparent difference in the character or time of the response between summer and winter.
![Page 6: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/6.jpg)
0 5 10 15 2030
35
40
45
50
55RS80 Humidity Response 2001/09/20
Elapsed time (minutes)
Re
lativ
e H
um
idity
(%
)
Reported HumidityExponential Decay Fit
= 321.8 seconds = 5.4 minutes
RS80 Humidity Response
![Page 7: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/7.jpg)
RS80 Humidity Response
• When moved outside, reported RH initially decreased, then increased with an exponential decay towards the outside value.• The exponential decay began between 5 and 120 seconds after being moved outside.• E-folding time constants were between 13 and 420 seconds.• Response was significantly slower in winter (T<-40°C) than in summer (T near –25°C).• Response in unheated winter cases (T = 17 K) was similar to winter cases using a heated building.
Summer Winter Unheated winter
# of Tests 5 24 2
Outside T (°C) -24 to -25 -45 to -71 -60
t1 (sec) 5-30 (30) 5-120 (33) 60-90
(sec) 13-20 (15) 30-420 (146) 50-120
![Page 8: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/8.jpg)
0 5 10 15 20 25 30671
672
673
674
675
676
677
678
679
680
681RS80 Pressure Response 2001/09/20
Elapsed time (minutes)
Pre
ssu
re (
mb
)
Reported PressureExponential Decay Fit
= 328.2 seconds = 5.5 minutes
RS80 Pressure Response
![Page 9: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/9.jpg)
RS80 Pressure Response• When moved outside, the sonde initially reported increasing P, followed by a slow exponential decay back to the correct P.• Reported P increased by 0.4 to 10.0 mb over a period of 175 to 450 seconds.• E-folding time constants were between 230 and 600 seconds.• Magnitude of maximum error increased with increasing thermal shock.
Summer Winter Unheated Winter
# of Tests 1 24 2
Outside T (°C) -25 -45 to -71 -60
t1 (sec) 450 175 to 450 (300) 275 to 400
P (mb) 3.3 3.5 to 10.0 (6.0) 0.4 to 1.6
(sec) N/A 230 to 600 (380) N/A, ~1500 to recover
![Page 10: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/10.jpg)
Small, Gradual Changes
• After equilibrating to conditions outside, sonde was raised and lowered on a 22 m tower at speeds of 0.4 to 1.0 ms-1.
• At the top of the tower, the temperature was 3 to 5 K warmer, the relative humidity was 3 to 5% higher, and the pressure was about 2 mb lower than at the surface.
![Page 11: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/11.jpg)
Tower Tests
0 50 100 150 200689
690
691
692
Time (seconds)
Pre
ssur
e (m
b)
0 50 100 150 200-64
-63
-62
-61
-60
-59
-58
Time (seconds)
Tem
pera
ture
(C
)
0 50 100 150 200101
102
103
104
105
106
Time (seconds)
Rel
ativ
e hu
mid
ity w
.r.t
. ic
e (%
)(a)
(b)
(c)
• Pressure responded to within the noise level by the time descent was completed. Change (about 2.2 mb) is approximately correct, according to hypsometric eqn.
• Temperature responded fully within 8 to 15 seconds of completion of descent.
•Relative Humidity took 15 to 20 seconds after descent to fully equilibrate. The sonde was able to correctly report the supersaturation with respect to ice.
![Page 12: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/12.jpg)
Conclusions
• Radiosondes should be stored and prepared at ambient temperatures
• If sondes must be prepared inside, they should be given at least 30 minutes to equilibrate to cold environments before launching
• Problems can arise even from small temperature differences, so unheated buildings should be avoided unless well ventilated
![Page 13: RADIOSONDE TEMPERATURE, HUMIDITY, AND PRESSURE RESPONSE AT LOW TEMPERATURES Stephen R. Hudson, Michael S. Town, Von P. Walden, and Stephen G. Warren 24](https://reader031.vdocuments.site/reader031/viewer/2022032522/56649d6a5503460f94a491cf/html5/thumbnails/13.jpg)
Conclusions (continued)
• Tests on the tower indicate that the sondes are capable of providing better data in cold conditions when given time to equilibrate to shock of being moved outside
• Further work should be done in more controlled environments, and with proper ventilation
• Radiosonde instrumentation still remains sluggish at low temperatures