(From the QuARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY
Vol. 81. No. 350. October 1955).
I
Some
recent
heights
measurements
of about
By R. J. MURGATROYD,
of humidity
50,000 ft
over
P. GOLDSMITH
from
southern
England
and W. E. H. HOLLINGS
Meteorological Research Flight, Farnborough, Hants.
I
aircraft
up
to
551.571.7
Some
recent
heights
By R.
J.
measurements
of humidity from aircraft up
of about 50,000 ft over southern England
MURGATROYD,
Meteorological
P. GOLDSMITH
and W. E. H. HOLLINGS
Research Flight, Farnborough,
(Manuscript
to
Hants.
received 25 May 1955)
I
1
SUMMARY
The humidity of
aircraft up to heights
point decreased with
- 115°F to - 120°F
the air was measured with a pressurized Dobson-Brewer hygrometer in a Canberra
of about 50,000 ft over southern England on 35 occasions during 1954. The frost
increasing height in the stratosphere and usually approached a constant value of
a few thousand feet above the tropopause.
1.
INTRODUCTION
The humidity measurements in the upper troposphere and lower stratosphere made
in aircraft of the Meteorological Research Flight at Farnborough and the High Altitude
Flight at Boscombe Down from 1943 to 1950, which have been presented by Bannon,
Frith and Shellard (1952), extended up to a height of about 40,000 ft, the ceiling of the
piston-engined aircraft then available. Late in 1953 a Canberra jet aircraft was obtained
and it then became possible to extend the ceiling of these measurements to about
50,000 ft. 35 ascents were made for this purpose in 1954 and are described below.
2.
INSTRUMENTATION
The pressurized form of the aircraft frost-point hygrometer described by Brewer,
Cwilong and Dobson (1948) was used for these measurements.
This instrument requires
experienced operators to obtain measurements of frost points below about - 100°F, and
when they are below - 120°F the frost deposit becomes difficult to recognize. In order
to extend its range and, incidentally, guard against possible small leaks of cabin air into
the instrument, measurements were also made on some occasions using air which had
passed through the jet engine compressor, a method due to Goldsmith (1955). Good
agreement was obtained between the frost points measured in this way and those obtained
using outside air directly.
Temperatures were measured using Meteorological Office
flat-plate resistance thermometers with balanced-bridge indicators, the readings being
corrected for airspeed.
3.
j
I
THE
OBSERVATIONS
All the readings of temperature and frost points obtained have been listed in Table 1.
The mean values at the heights given have been plotted to obtain the mean curves shown
in Fig. 1. In addition mean temperature and frost-point values have been plotted at
heights above and below the tropopause in the two groups shown in Fig. 2. The group
listed as 'high tropopause'
cases refers to ascents when the tropopause was above
35,000 ft and that of the' low tropopause'
cases to occasions when it was below that
level.
4.
DISCUSSION
The preliminary results from this set of measurements are:
(1) The frost point over southern England decreases with height above the tropopause
and tends to approach a constant value, usually between - 115°F and - 120°F, a few
thousand feet above this level.
533
R.
534
TABLE
J. MURGATROYD,
1.
P. GOLDSMITH
TEMPERATURE AND FROST POINT (IN BRACKETS)
I.C.A.N.
19 Jan.
Height Pressure
(ft)
(mb)
1335
22 Feb.
24 Feb.
25 Feb.
1555
1110
1115
843
697
572
465
376
+49(-)
+34(+10)
+18 (-21)
-03 (-46)
-24(-62)
+42(+27)
+33(+12)
- (-14)
-08(-29)
-29 (-63)
+34(+21)
+17(+04)
-03(-19)
-25(-42)
-46 (-66)
+42(+17)
+12(-04)
+01(-52)
-21(-64)
-31 (-71)
+28(+15)
30,000
32,000
33,000
34,000
35,000
301
274
262
250
238
-50 (-63)
-so
-54 (-8S)
-53 (-81)
-55 (-87)
-5S (-77)
36,000
37,000
38,000
39,000
40,000
227
216
206
197
187
41,000
42,000
43,000
44,000
45,000
178
170
162
155
147
46,000
48,000
49,000
50,000
51,000
140
127
121
116
111
-65 (-75)
OF,
INDIVIDUAL ASCENTS
Dates
5 Mar.
10 Mar.
Times (GMT)
1505
1220
5,000
10,000
15,000
20,000
25,000
(-57)
-60 (-66)
HUMIDITY
and W. E. H. HOLLINGS
-09(-67)
-48 (-68)
(1954)
TABLE
11 Mar.
22 Mar.
23 Mar.
1515
1505
1600
+41( +21)
+22(-25)
+07 (-28)
-14(-41)
-35 (-66)
-60 (-92)
+35(-)
+27 (-37)
+06 (-33)
-18(-54)
-37 (-58)
5,000
10,000
15,000
20,000
25,000
843
697
572
465
376
-57 (-82)
30,000
32,000
33,000
34,000
35,000
301
274
262
250
238
36,000
37,000
38,000
39,000
40,000
227
216
206
197
187
41,000
42,000
43,000
44,000
45,000
178
170
162
155
147
46,000
48,000
49,000
50,000
51,000
140
127
121
116
111
-52 (-74)
-59 (-79)
-50 (-81)
-56 (-85)
-52 (-53)
-59 (-67)
-65 (-83)
-60 (-91)
-66 (-73)
-71 (-97)
-78 (-85)
-78 (-77)
-61 (-98)
-54 (-102)
-82(-90)
-84(-87)
-62(-102)
-51(-10S)
-81(-99)
-85(-92)
-56(-108)
-50(-112)
-71 (-113)
-78 (-102)
-55 (-115)
-54 (-115)
-64(-109)
I.C.A.N.
Height Pressure
(ft)
(mb)
+42(+25)
+33 (-02)
+14 (-40)
-07(-19)
-26 (-28)
-62 (-90)
-69 (-74)
-55 (-103)
-69(-89)
-61(-98)
-69(-79)
-70(-97)
-59(-109)
-71(-86)
-65 (-105)
-57 (-115)
-70 (-93)
-52 (-111)
-63(-113)
-57(-119)
-66(-101)
-52(-117)
1
J
-61 (-112)
-72(-124)
-67(-105)
-59(-115)
-55(-117)
-59(-115)
-63(-115)
-58(-122)
-59(-108)
-51(-119)
-72(-121)
-71 (-120)
-63(-107)
-64 (-108)
-56(-113)
-57 (-113)
-55(-116)
-50 (-118)
-61(-116)
-61 (-117)
-63 (-117)
-63(-119)
-60 (-120)
-64(-123)
-63 (-122)
-57(-115)
-54 (-117)
-52(-120)
-52 (-121)
-71 (-121)
-67 (-107)
-61 (-113)
-54 (-118)
-62 (-120)
-6S (-122)
-59 (-120)
-55 (-120)
I.C.A.N.
25 May
Height Pressure
(ft)
(mb)
1345
28 May
10 June
11 June
28 June
29 June
1 July
0935
1100
0930
1015
0915
1415
5,000
10,000
15,000
20,000
25,000
843
697
572
465
376
+45 (+38)
+25 (+12)
+11(+13)
-04 (-09)
-27 (-26)
+55(+35)
+34 (+25)
+17(+15)
-02 (-03)
-22 (-38)
30,000
32,000
33,000
34,000
35,000
301
274
262
250
238
-48(-49)
-58 (-62)
-41(-46)
-49 (-56)
-64 (-76)
-57 (-62)
36,000
37,000
38,000
39,000
40,000
227
216
206
197
187
41,000
42,000
43,000
44,000
45,000
178
170
162
155
147
46,000
48,000
49,000
50,000
51,000
140
127
121
116
111
+49 (-01)
+38(+25)
+22(+14)
+04(-11)
-20 (-36)
-51(-74)
-61(-90)
-42(-57)
-39(-48)
-52(-65)
-51(-103)
-67(-78)
-60(-67)
-58(-105)
-68(-106)
-44(-115)
-56(-104)
-76(-90)
-42(-108)
-46 (-lIS)
-59 (-108)
-63 (-107)
-44 (-110)
-58 (-112)
-59(-119)
-48(-120)
-47 (-121)
-49(-)
-60(-111)
-58 (-110)
-60(-117)
-60 (-118)
-61 (-119)
-47(-111)
-47 (-)
-46 (-120)
1440
1025
-41 (-104)
+49(+26)
+33(-11)
+17(-44)
-02(-55)
-18(-36)
+58 (+24)
-49(-83)
-38(-56)
-44(-57)
-35(-52)
-51(-59)
-53(-58)
-55(-70)
-52(-65)
-64(-69)
-61(-83)
11 Aug.
17 Aug.
23 Aug.
1000
1100
1000
+38 (+34)
+25 (+17)
+03(-14)
00(-12)
-11 (-38)
-47(-53)
-42(-67)
-50(-77)
-58(-75)
-53(-80)
-56(-62)
-57(-86)
-65(-75)
-51(-87)
-49(-92)
-61(-84)
-54(-99)
-53(-93)
-66(-92)
-46(-92)
-51(-96)
-60(-95)
-49(-99)
-49(-98)
-69(-73)
-45(-99)
-51(-103)
-52(-103)
-48(-105)
-58(-112)
-54(-105)
-65(-86)
-47(-100)
-54(-106)
-56(-107)
-49(-106)
-55(-116)
-56(-110)
-67(-90)
-48(-108)
-54(-111)
-59(-113)
-46(-110)
-50 (-111)
-49 (-116)
-57 (-115)
-56(-117)
-59 (-116)
-60 (-118)
-49 (-112)
-51 (-113)
-56 (-121)
-62 (-121)
-56 (-118)
21 Dec.
22 Dec.
1420
1355
-42 (-102)
-42(-112)
-41 (-115)
-42 (-112)
-46(-117)
-49(-118)
-45(-113)
-48(-116)
-53(-119)
-56(-119)
-60(-114)
-59(-118)
-68(-90)
-67(-89)
-49(-)
-45 (-117)
-57 (-121)
-60 (-120)
-61 (-99)
9 Dec.
10 Dec.
13 Dec.
1210
1045
1100
227
216
206
197
187
-66(-73)
-54(-110)
36,000
37,000
3S,OOO
39,000
40,000
41,000
42,000
43,000
44,000
45,000
178
170
162
155
147
46,000
48,000
49,000
50,000
51,000
140
127
121
116
111
-52(-117)
-53 (-119)
-50 (-118)
Dates
5 Aug.
10 Aug.
Times (GMT)
1010
1100-
+18(-04)
-01(-33)
-22(-35)
-40(-59)
-43(-111)
-60(-79)
1
j
535
-66(-96)
-39 (-61)
-52 (-115)
-45(-120)
-47 (-120)
0950
301
274
262
250
238
-45 (-120)
-45(-118)
-45 (-118)
1510
30,000
32,000
33,000
34,000
35,000
-45 (-41)
-44(-117)
-46 (-114)
-54(-113)
-57 (-117)
-44(-112)
4 Aug.
843
697
572
465
376
-47(-107)
-46(-113)
14 July
'-45(-85)
STRATOSPHERE
1 (continued)
6 July
5,000
10,000
15,000
20,000
25,000
-50(-99)
-64(-85)
-71(-91)
-47(-62)
-55 (-6S)
-53(-95)
-61 (-Sl)
-62(-101)
-55 (-114)
-54(-120)
-54(-74)
+40(+33)
+33(+12)
+15 (00)
-05 (-34)
-25 (-48)
LOWER
5 July
I.C.A.N.
26 Aug.
Height Pressure
(ft)
(mb)
1005
-57(-84)
-48(-92)
-67(-86)
Dates
16 June
24 June
Times (GMT)
0940
0835
OF THE
-31 (-40)
+42(-)
+31 (-37)
+15(+09)
-07(-12)
-30 (-40)
+40 (-03)
+27 (00)
+16 (-38)
-10(-54)
-33 (-56)
-67 (-93)
-66(-104)
-51 (-59)
-60(-74)
-48 (-64)
-55(-69)
-57 (-77)
-65(-80)
-68(-110)
-67(-82)
-66(-71)
-73(-84)
+08 (-26)
-13 (-43)
+08(-10)
-60 (-63)
+05(-19)
-54 (-65)
-67 (-81)
-65(-93)
-66 (-98)
Dates
14 Dec.
20 Dec.
Times. (GMT)
1100
1420
-65 (-104)
+43 (+31)
+24 (+18)
-04 (-55)
-26 (-39)
-45 (-68)
+27 (+15)
+09 (00)
-11(-19)
-25 (-41)
-49 (-63)
-57(-76)
-66(-75)
-70 (-71)
-64(-113)
-72(-86)
-76(-81)
-77(-89)
-76(-91)
-69(-116)
-69(-97)
-82(-91)
-81(-98)
-83(-90)
-68 (-120)
-70 (-107)
-75 (-105)
-77 (-104)
-64 (-93)
-68 (-121)
-72 (-108)
-75 (-116)
-81 (-111)
-59(-105)
-72(-122)
-68(-112)
-74(-119)
-75(-113)
-69 (-111)
-67(-81)
-68(-112)
-66 (-85)
-95 (-98)
-92 (-100)
-69(-112)
-97 (-109)
-84(-114)
-82 (-111)
-62 (-110)
-66(-111)
-65(-116)
-66 (-118)
-71 (-122)
-75(-122)
-70 (-116)
-75(-115)
-75 (-123)
-76(-123)
-80 (-115)
-73(-117)
-84 (-117)
-77 (-117)
-72 (-117)
-76 (-125)
-73 (-117)
-73(-119)
536
R.
J. MURGATROYD, P. GOLDSMITH
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Figure 1. Mean values of temperature and frost point, M.R.F. ascents 1954.
-16,000
(2) The lapse rate of frost point also decreases with height, being on the average
about 4°F in the 1,000ft above the tropopause but less than 1°F per 1,000 ft at heights
of about 15,000 ft above the tropopause.
Usually no discontinuity in the lapse rate of
frost point was observed at the tropopause.
In some cases however the change from
a large lapse rate of frost point to a lower lapse rate higher up appeared to be discontinuous,
suggesting a ' humidity tropopause' a few thousand feet above the temperature tropopause.
The distance between these two levels varied between 2,000 and 10,000 ft and no relationship between it and other meteorological variables has yet been noticed.
(3) Owing to aircraft unserviceability the ascents could not be evenly spaced throughout the year but readings were obtained in all four seasons. No significant difference of
frost point at 50,000 ft between winter and summer has been found.
(4) When the heights are referred to the tropopause level the ' high tropopause'
cases show a lower temperature and also a lower frost point, level for level, compared with
the 'low tropopause' cases. In general, high and low values of frost points in the lowest
10,000 ft or so of the stratosphere correspond well with high and low frost-point values
at the tropopause, but this correspondence disappears at higher altitudes as the frost
point approaches constancy.
The accuracy of the temperatures quoted is thought to be ± 2°F, a value deduced
from the variability of the airspeed correction of the flat-plate thermometer in trials
made for this purpose at high speeds with the Canberra aircraft. The heights quoted
may be up to 500 ft in error, a figure obtained from comparative trials between the pilot's
altimeter and a radar altimeter. The frost points have a random error of ± 3°F due to
uncertainties in reading the hygrometer under these conditions. An analysis of humidities
measured with this instrument in the neighbourhood of high cloud by Murgatroyd and
Goldsmith (1953) gave the result that the air there had a frost point on the average 3°F
Jower than would have been expected if the air were saturated with respect to ice. This
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Figure 2. Mean values of temperature and frost point relative to height of tropopause.
suggests that the instrument may also have a constant error, reading somewhat low at
these altitudes but it is unlikely that the error will be more than a few degrees Fahrenheit.
The general picture obtained from these measurements is therefore one of variable
frost points at the tropopause tending to constancy of frost point at - U5°F or so at
levels of 10,000 to 15,000 ft above it. The air at these altitudes is therefore very dry
with a relative humidity with respect to ice of less than 1 per cent. The range of variation
of frost-point values there is usually small although considerably higher frost-point values
were observed on one occasion (5 August 1954). These values of frost point are in
general agreement with those expected from the tendency observed at the greatest heights
by Bannon, Frith and Shellard (1952), although they are a few degrees lower.
It is hoped to continue measurements of this type throughout 1955.
ACKNOWLEDGMENT
We are indebted to the Director of the Meteorological
publish this paper.
Office for permission to
REFERENCES
Bannon, J. K, Frith, R.
and Shellard, H. C.
Brewer, A. W., Cwilong, B. M.
and Dobson, G. M. B.
Goldsmith, P.
Murgatroyd, R.]. and Goldsmith, P.
1952
Met. Off., Geophys. Mem., London, No. 88.
1948
1955
1953
Proc. Phys. Soc., 60, p. 52.
Quart.]. R. Met. Soc., 81, p. 607.
Air Ministry, Met. Res. Cttee., M.R.P., No. 833,