THE U N VE RS ITY OF M ICHIGAN COLLET GE OF ENGINEERING Department of Engineering Mechanics Meteorological Laboratories Final Report SOME HEAT TRANSFER CHARACTERISTICS OF TWO THERMOCOUPLE PROBES Donald J. Portman Associate Research Meteorologist ORA Project 03501 NATIONAL SCIENCE FOUNDATION IGY GRANT Y/21013/336 through The Ohio State University'Research Foundation (Project No. 971) and The U. S. Army Quarterlraster Research and Engineering Command Environmental Protection Research Division Natick, Massachusetts administered through: OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR September 1961

TABLE OF CONTENTS Page LIST OF TABLES iii LIST OF FIGURES iv ABSTRACT v 1. INTRODUCTION 1 2. CONCLUSIONS 4 3. RESULTS 5 4. DISCUSSION 8 5. EQUIPMENT AND PROCEDURES 13 ACKNOWLEDGMENTS 16 REFERENCES 17 ii

LIST OF TABLES Table Page I-A Radiation Errors: Wind Perpendicular to Probe from Junction Side; Radiation Perpendicular from Side Opposite Junction 18 I-B Radiation Errors: Wind Perpendicular to Probe from Junction Side; Radiation Parallel to Probe from End Opposite Connector 19 I-C Radiation Errors: Wind Perpendicular to Probe from Junction Side; Radiation Parallel to Probe from Connector End 19 II-A Radiation Errors: Wind Sixty Degrees from Perpendicular, from Junction Side; Radiation Perpendicular from Side Opposite Junction 20 II-B Radiation Errors: Wind Sixty Degrees from Perpendicular, from Junction Side; Radiation Perpendicular from Junction Side 21 II-C Radiation Errors: Wind Sixty Degrees from Perpendicular, from Junction Side; Radiation Parallel to Probe from End Opposite Connector 22 III-A Radiation Errors: Wind Parallel to Probe from End Opposite Connector; Radiation Perpendicular to Probe from Side Opposite Junction 22 IV Temperature Corrections in Degrees F., for Selected Periods at the Amundsen-Scott South Pole Station 23 V Test Data Used for Compiling Temperature Corrections given in Table IV 24 VI Temperature Differences for Nighttime Tests over Snow 25 iii

LIST OF FIGURES Figure Page 1 Side view of shield probe 26 2 Wind tunnel test arrangement, looking upwind 27 3 Wind tunnel test arrangement, looking downwind 27 4 Test arrangements over snow 28 5 Two views of test arrangement "B" over snow 29 6 Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 0.0 degrees 30 7 Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 5.0 degrees 31 8 Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 10.0 degrees 32 9 Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 15.0 degrees 33 10 Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 20.0 degrees 34 11 Probe orientation at South Pole Station 35 12 Thermocouple junction position in shield with respect to elevation angles 35 13 Radiation errors versus wind speed 36 iv

ABSTRACT A thermocouple probe with flat-plate radiation shields was tested iL a wind tunnel to determine steady-state radiation errors for small solar elevation angles. The probe had been used in the Uo S. Army Quartermaster Research and Engineering Command micrometeorological investigation in the Antarctic. Test data are given for various radiation intensities and angles of incidence and for various wind speeds and directions. Data are interpolated from these results to provide corrections for temperature profiles measured at the Scott-Amundson South Pole Station. A second probe, without a shield, was compared with shield probes when mounted over a snow surface in northern Michigan during a winter night. The experimental results are discussed and test equipment and procedures are described.

1. INTRODUCTION Accurate measurement of air temperature with thermocouple probes in the atmospheric surface layer is dependent upon both wind and thermal radiation conditions. In the presence of solar radiation) when the wind is light, the probes are likely to be in thermal equilibrium at a temperature higher than that of air. Tn the absence of solar radiation, with light winds, and particularly with a cold, cloudless atmosphere, the probes tend to be in thermal equilibrium at a temperature lower than that of the air. Only in windy, cloudy conditions are probes likely to indicate true air temperatures. In other words, ideal measurement conditions exist when the radiative heat transfer between a probe and its environment is negligible in comparison to the transfer by convection. The problem of radiation error is particularly significant in measuring air-temperature profiles near the ground because of the increase of wind speed with height. A probe within a meter from the ground might have a radiation error of <C, while an identical probe at 6 or 8 meters above the ground would have no discernible radiation error, At any one time the two probes might have the same radiative heat transfer rates but would experience entirely different wind speeds and, therefore, different convective heat transfer rates. This difficulty has impeded research on relationships between wind and temperature profiles near the ground and on heat transfer in the atmospheric surface layer. Radiation error in temperature measurement presents a difficult problem also in specifying climatic extremes, Both the highest and

lowest temperatures in a region are likely to be recorded under clear conditions with light winds. These are exactly the conditions that yield the greatest radiation errors, errors that, in either case, tend to indicate greater extremes than actually existed. Two types of thermocouple probes were used in the U. S. Army Quartermaster Research and Engineering Command Antarctic micrometeorological investigation. In the presence of solar radiation, thermocouple junctions were mounted in rectangular radiation shields made of thin, flat, reflective aluminum plates. The junctions were formed by twisting pairs of Noo 36 B and S gauge copper and constantan wires. It is known that radiation shields of this type reduce radiation errors but since the shield plates are normally mounted horizontally, the thermocouple junctions were exposed directly to solar radiation for low sun angles. In the absence of solar radiation, i.e, in the winter months, thermocouple probes without shields were used. These were long, thin probes with the thermocouple junctions and their leads imbedded in ceramic insulation. Air temperature measurements made with these probes in clear weather with light winds may be expected to have significant errors due to unrestricted radiative heat loss. This report gives the results of a series of wind tunnel tests to determine steady state radiation errors for the shielded thermocouple junctions for small solar elevation angles. Test data are given for different azimuth and elevation angles of direct radiation and for various wind speeds and relative directions. Data are interpolated from these

results to provide, for various wind speeds, specific corrections for temperature profiles measured at the Scott-Amundson South Pole Station. Evaluation of performance characteristics of the unshielded probe used in the absence of solar radiation was restricted to a few nighttime field tests over snow. Because of limitations in time and funds it was not possible to continue the evaluation.

2. CONCLUSIONS The steady-state radiation error for the probe with a flat-plate radiation shield varies in a consistent way with wind speed and relative direction and with radiation intensity and azimuth and elevation angles. The error varies directly with intensity of radiation and is greatest for radiation striking the probe horizontally from the side on which the junction is mounted. It is greatest, also, for least wind speed and for wind aligned in direction with the long dimension of the probe. With appropriate interpolation the test data may be used to correct temperature observations if the following information is known: (a) Wind speed; (b) Wind direction relative to probe; (c) Radiation intensity; (d) Radiation elevation angle; and (e) Radiation azimuth angle. The probe without a shield may indicate an air temperature at least 0.10 to 0.15 degrees colder than real when near a snow surface under a clear, cold atmosphere when the wind is from 0.5 to 3 mph. Experimental and theoretical findings of others may be used to extend these results to other wind speeds.

35 RESULTS The results of the wind tunnel tests for the shield probe are given in Tables I through III in terms of temperature errors in degrees Fahrenheit, for different wind speeds and directions and different radiation intensities, elevation angles and azimuth angles. Since the errors represent increases in probe temperature caused by incident radiation, the values should be subtracted from measurements made in the field under similar conditions. The probe that was tested had been used for measurement of temperature profiles at the South Pole Station. It was a standard item as obtained from Thornthwaite Associates* except that for the tests the two inner plates of the shield were removed as they were for the South Pole measurements in order to prevent the accumulation of snow near the thermocouple junction. The probe is shown in Figure 1. It may be seen, also, in Figures 2, 3 and 4, Details of the probe and of the test equipment and procedures are given in Section 5o The data in Table I-A are displayed in Figures 6 through 10. Each figure shows relationships between steady state radiation errors and radiation intensity for different wind speeds at a given radiation elevation angle. The plotted points were obtained by interpolation from graphs prepared to show radiation error as a function of wind speed for various test conditions. The interpolation was made to obtain lines for wind speeds in even units to facilitate further interpolation. As seen A thermocouple probe of nearly identical construction (except for its supporting elements) was described by Portman (lg957)

in Tables I, Ii and III most of the original data were obtained for fractional units of wind speed. The figures show that radiation error for these data is a linear function of radiation intensity. Thus, linear interpolation may be used to obtain radiation errors for different radiation intensities. The results are discussed in Section 4, Temperature corrections for six different observation periods, one to three days each, at the South Pole Station in 1958 are listed in Table IV. The six periods were those during which measurements of solar radiation at normal incidence were made by Mr. Kirby J. Hanson.* Temperature corrections for these days were obtained by interpolation from test results selected on the basis of South Pole Station wind observations and solar elevation angles. The test data used for the corrections are identified in Table V and the probe orientation at the South Pole Station is shown in Figure 11 In the cases of two entries for a given parameter in Table V, approximately linear interpolation was used to obtain appropriate corrections. Results of nighttime field tests of the unshielded rod probe over snow are given in Table VI. Included, also, are similar data for the shield probe for comparison. The temperature differences were obtained by arranging a thermocouple circuit so that the outputs of both the rod probe and the shield probe were recorded directly with reference to a second shield probe, The latter was quite similar to the one tested in the wind tunnel but had a smaller, soldered thermocouple junction and *Dr, Harry Wexler, Director of Meteorological Research, U. So Weather Bureau kindly supplied the radiation data in advance of its publication. 6

thinner shield plates. Figure 4 shows the two test arrangements and the relative wind directions during the tests. In Figure 5 are two photographs of test arrangement "B". As revealed by the averages for the separate test periods given in Table VI, the temperature of the rod probe for the first three tests was lower than that of the University of Michigan reference probe but the situation was reversed for the fourth test. During the last test, as noted in the table, all probes were covered with frost. The results are discussed in Section 4.

4. DISCUSSION The experimental results presented in the previous section may be interpreted in terms of steady-state heat transfer rates between an isolated cylinder and its environment. If only heat transfer by radiation, qr, and forced convection, q,, are considered, the heat balance per unit length of the cylinder may be expressed as qc = qr (1) or h(T-Ta) =R + r - e-T4 (2) in which h = convective heat transfer coefficient T = cylinder temperature, ~A Ta = air temperature, ~A R = "short-wave" radiation received r = "long-wave" radiation received e = emissivity of cylinder u = Stefan-Boltzmann constant. It is assumed that the end effects are negligible and that the cylinder is isothermal. The quantity (T-Ta) = At is the steady-state radiation error if the cylinder is used as an air temperature probe. The heat transfer coefficient, h, may be expressed in terms of the Nusselt number, Nu, which is related to the Reynolds number, Re, and the Prandtl number, Pr, (See McAdams, 1942 or Jacob, 1949). Thus hD Nu = f(Re, Pr) upC uD (3) Re if Pr = k

in which D = diameter of cylinder = kinematic viscosity u = air speed f = empirically determined function k = thermal conductivity p = density Cp = specific heat at constant pressure According to Jacob (1949, p. 560), Hilpert found that for wires 0.002 to 0.1 cm in diameter, the Nusselt number could be expressed as Nu = B Ren (4) in which B and n depend on Re. Thus, h = k B -n Dn-l un (5) and from (2) At = (R + r - e CoT4) h-1 (6) (R + r - e T4) k-1 B-1 In Dln u-n (7) From Hilpert's data an appropriate value for n is about 0O4 for the wind tunnel test data. Equation (7) shows, therefore, that for conditions otherwise constant, the radiation error (1) increases linearly with radiation intensity, (2) decreases with increasing wind speed, and (3) increases with increase in diameter of probe. As revealed by Figures 6 through 10 the wind tunnel data show the expected linear dependence on radiation intensity. The fact suggests that changes in the term e GT4 were insignificant during the test interval and that linear interpolation and extrapolation may be used to determine radiation errors for intensities other than those measured. The dependency of one set of test data on wind speed is shown in

Figure 13 in which temperature errors and wind speeds are plotted in logarithmic co-ordinates. Shown also is a dashed line whose slope is -0.4. It appears that the wind tunnel results may be extrapolated to low wind velocities with the aid of such a relationship. The possible influence of free convection at very low velocities, however must be considered so that extrapolation below 0.5 mph with these data is probably not reliable. The applicability of wind tunnel test data to measurements in the Antarctic may be examined by considering Equation 6 for both test and measurement conditions. The ratio of radiation errors for the wind tunnel to those for the Antarctic is Atwt R + (r - eGT4 wtj haa = (8) Ataa R + (r - eoT4)aaj hwt The term (r - ecT4)wt is negligible in comparison to R and (r - eiT4aa is negative, but not large, so that the first term on the right is probably somewhat larger than unity. An estimate of the heat transfer coefficient ratio may be i.;ade if it is assumed that an equation of the type h = K Re Prp (9) is valid for both conditions with K, c and a invariant. Then haa aa aa Paa C Paa hwt Wt (kt Pwt/ Pwt from the defining relationships after eliminating u and D. For relationships like Equation (9), Jacob (1949, p. 563) gives the following values 10

obtained by Ulsamer~ = o0. 385 = 0.31 For the temperature and pressure conditions: wind tunnel 78~F and 985mb South Pole Station -100~F and 680mb the ratios are aa 0.71- 75 (Handbook of Chemistry and Physics, 37th ed.) 0aa 67 69 (Zemansky, 1943) kkwt/ \aB (up aa )> (p 1 (Handbook of Meteorology, PWt kCpwt 1945) and haa o.8 hwt It appears, therefore, that the product of the two ratios on the right side of Equation (8) is near unity so that the wind tunnel results may be applied directly to the South Pole measurements. The results of the field tests I, II and III for the rod probe may be considered minimum radiation errors for the conditions of the experiment since the reference shield probe itself was probably colder than the air. in test IV the presence of frost on all probes undoubtedly accounted for the reversal of temperature differenceso Either the heat required for change of state —more on the larger rod probe than on the fine wire 11

shielded junction —or the modification of surface by the frost cover could account for the rod probe indicating higher temperatures than the shield probe. Extension of these findings to other situations with the aid of a heat-balance equation such as Equation (6) is difficult for several reasons. Perhaps the most important difficulty is the lack of information on long wave radiation exchange between the probe and its environment. Another difficulty is the fact that conduction within the rod may be an important term in this case. Finally, it should be noted that there appears to be no information on Nusselt numbers in the literature for blunt-ended rods with sub-sonic flow at various angles. The results are significant, nonetheless, for revealing the order of magnitude of radiation error for unshielded probes in an Antarctic environment without solar radiation. 12

5. EQUIPMENT AND PROCEDURES Thermocouple Probes —The shield probe is shown in Figure 1 and can be seen in test arrangements shown in Figures 2, 3 and 5. (In Figure 5 the QMRE shield probe is the one on the left.) The shield plates were made of "Alzak Aluminum" and were highly reflective on the outward facing surfaces, but painted black on the inward ones. The upper plate was 2-5/8 x 9-11/16 x 0.032 inches and the lower 8-9/16 x 1-5/16 x 0.32 inches. They were about one-half inch apart. The twisted thermocouple junction can be seen in Figure 1, about two-thirds of the distance between the connector and the spacer near the end of the probe. The remainder of the thermocouple lead wire between the plates was covered with a thin f iber insulation, The unshielded (rod) probe is shown in Figure 5 in the field test arrangement. It is a standard element manufactured by Thermo-electric Coo The outer diameter of the rod housing the thermocouple junction was 0.040 inches and it was 12 inches longo Wind Tunnel Test Equipment and Procedures —The shield probe was tested in a 14' x 8? x.515 working section of a low speed wind tunnelo The tunnel is a closed loop, double return type with a contraction ratio of approximately 4 to 1 at the Venturi section. The air is circulated by an adjustable-pitch, axial-flow fan powered by a variable speed d.c.o motor. Air speed in the tunnel is measured by a pitot tube and a micro -manometer. The test arrangement in the wind tunnel is shown in Figures 2 and 13

3, looking upwind in the former and downwind in the latter. Attached to the stand supporting the shield probe is a Dwyer wind speed probe which was calibrated with the tunnel pitot tube. The radiation source was a 250 watt Ken-Rad infrared lamp positioned on a ring stand as shown in the figureso Radiation intensity of the lamp for different positions was determined with a standard Eppley pyrheliometero The reference thermocouple junction for the probe was placed about 5 feet upwind at the same distances from the tunnel floor and walls as the probe. The lamp and probe positions were altered to obtain the orientations required. The temperature difference between the test probe and the reference junction was recorded directly with a Leeds and Northrup Speedomax Model S, AZAR recorder. A Leeds and Northrup DC amplifier was used to provide the desired sensitivity. For each test measurement, the radiation intensity and the tunnel wind speed were held constant for a period sufficiently long to assure that steady-state conditions prevailed. Field Test Equipment and Procedures —The test arrangements over snow are shown in Figures 4 and 5. The three probes were mounted side by side approximately 2 1/2 inches apart and 14 inches above a smooth snow surface. Wind speed at the same height was measured with a Beekman and Whitley Model 170-34 anemometer, and net radiation with a Beckman and Whitley Model N188-1 net exchange radiometer. The reference probe was a shielded thermocouple junction made of No. 36 B and S gauge copper and constantan wires. The junction was made by soldering the ends together with a minimum overlap. The probe was 14

quite similar to that tested in the wind tunnel except that there were two inner, parallel plates, equally spaced between the external ones. The thermocouple outputs were recorded with the same system as that used in the wind tunnel. A switching arrangement permitted alternate recording of the difference between the two shield probes and the rod and the shield probe.

ACKNOWLEDGMENTS The assistance of Joy Beil, Floyd C. Elder, Alvin E. Marshall, Dwight D. Meeks and Edward Ryznar is greatfully acknowledged. Mr. Marshall conducted the wind tunnel tests and Messrs. Elder, Meeks and Ryznar were responsible for the field tests. Mrs. Beil typed the report and assisted in other aspects of its preparation. 16

REFERENCES Handbook of Chemistry and Physics, 1955-1956: Hodgman, Charles D., Ed., Thirty-seventh Edition, Cleveland, Ohio, Chemical Rubber Publishing Company. Handbook of Meteorology, 1945: Berry, Jr., F. A., E. Bollay, and N. R. Beers, Ed., First Edition, New York, McGraw-Hill. Jakob, Max, 1953. Heat Transfer, Vol. I, New York, John Wiley and Sonso McAdams, William H., 1942: Heat Transmission, New York, McGraw-Hill. Portman, D. J., 1947: "Shielded Thermocouples," Exp. the Atmoso First Mile, New York, Pergamon Press, Inc., 1, 157-167. 17

Table I-A Radiation Errors: Wind Perpendicular to Probe from Junction Side; Radiation Perpendicular from Side Opposite Junction Radiation Elev. angle Intensity Wind Speed, mph Temp. Degrees ly/min 4.3 5.8 8.0 10.1 13.7 18.4 2353 33.9 dego Fo 0.0 0.48 0.53 0.30 0.27 0.25 0.21 ---- ---- -- 78.2 0.0 0.72 0.66 0.53 0.39 0.31 0.o 31 -- ---- ---- 78,2 0.0 0.87 0.75 0.62 0.48 0.40 03 ---- ---- ---- 78.2 0o. 0.87 ---- ---- ---- ---- o.40 o38 0.35 o.33 75.3 0.0 1.10 0.93 0.80 0.62 0.53 0.48 ---- ---- ---- 78.2 0.0 1.44 1 o15 1,02 0.80 0.74 0.62 ---- 78.2 0.0 1.44 ---- ---- -—. ---- 62 0.58 0.53 0.49 7593 5.0 0.72 0.75 0.62 0.47 0.39 0.31 ---- 77.8 5.0 0.87 0.86 0.71 0.51 0.44 0.38 ---- ---- ---- 77.8 5.0 0.87 ---- ---- ---- ---- 0.35 0,33 0.31 0.29 75.3 5.0 1.10 1.00 0.77 0.57 0.52 0.41 ---- — 77.8 10.0 0.87 0.62 0o42 0.33 0.27 0.22 ---- -- 78.o o.o o0.87 -0.22 0.20 0.20 0.18 75, 3 10.0 1.10 0.66 0.60 0.33 0.29 0.27 ---- ---- 78,0 10.0 1.27 0.66 0.49 0o35 0.29 0.24 ---- -— 78.o 10o.o 1.44 0.67 0.55 0o38 0.33 0.29 78,o 10.0 1.44 ---- ---- ---- ---- 0.33 0.31 0.27 0.22 75o3 15.0 1.44 0.33 0.27 0,15 0.11 009 --- ---- ---- 8.0 1500 1.44 -- 0.15 013 0. 11 75 3 20.0 1.10 02o 2 o.11 o. 4 0.00 0.00 o80 Q 20.0 1.44 0O29 0.11. 4 0.02 0.02 -78 —- ---- ----.0 2tS o 1.44 --- --- ---- ---- ---- o-.g o-oo 20.0 1.44 O0.11 0.09 0.07 20.0 1.94 0.31 0.27 0.13 0.11 0.07 -78 0 30.0 1.44 0.15 0.07 oo o.oo o.oo ---- -. —- 78. 30.0 1.44 -- - 0.11 o.09 0.07 18

Table I-B Radiation Errors: Wind Perpendicular to Probe from Junction Side; Radiation Parallel to Probe from End Opposite Connector Radiation Elev. angle Intensity Wind Speed, mph Temp. Degrees ly/min 4.3 5.8 8.0 10.1 13.7 18o4 23o3 33.9 deg. F. O.o 0.72 0.29 0.20 0.13 0.09 o.04 -78.2 0.0 1.10 0.29 0.20 0.13 0.11 0.07 - ---- ---- 78.2 0.0 1)44 0.31 0.22 0.16 Oo10 0.08 78.2 10.0 1.10 0.22 0.11 0.04 0.02 O.0 ---- ---- ---- 79~ 5 10.0 1.44 0.27 0.20 0.07 0.0o4 0.02 79.5 20.0 1.10 0.18 0.11 0.02 0.00 0.00 79~ 5 20.0 1.94 0.20 0 o 11 0.04 0.02 0.00 ---- ---- ---- 79.5 Table I-C Radiation Errors: Wind Perpendicular to Probe from Junction Side; Radiation Parallel to Probe from Connector End Radiation Elev. angle Intensity Wind Speed, mph Tenmp Degrees ly/min 4,3 5 8 8.0 10.1 13o7 18.4 23 3 33~9 deg. F. 20.0 1,10 0. 42 0. 33 o. 18 0.13 0o09 79 5 20.0 1,94 o. 58 O.49 0.31 0.24 0.20 --- 79 5 r z z~~1

Table II-A Radiation Errors~ Wind Sixty Degrees from Perpendicular, from Junction Side; Radiation Perpendicular from Side Opposite Junction Radiati on Elev. angle Intensity Wind Speed, mph Temp. Degrees ly/min 4.3 5.8 8.0 10.1 13.7 18.4 23.3 33.9 deg. F. 0.0 o0.87 1oo 0.80 0.62 0.53 0.44 ---- ---- ---- 79 5 0.0 1o44 1.46 1.24 0.95 0.84 0.71 ---- --- - 79.5 5.0 0.87 o.84 0.71 0.55 0,47 0.40 ---- ---- ---- 79.5 10.0 0.87 0,62 0.49 0.31 0.27 0.22 ---- ---- ---- 79 5 10.0 1.44 o.80 0.60 0.44 0.40 0.33 ---- ---- ---- 79.5 15.0 1,44 0.53 0.44 0,27 0.22 0.18 ---- ---- 78.5 20.0 1.10 0.31 0.18 0.13 0.09 4 ---- ---- ---- 785 20.0 1.44 0.29 0.18 0.13 0.10 0.07 ---- ---- ---- 78.5 20.0 1.94 0.29 0,18 0.12 0o08 0.07 ---- ---- ---- 78.5 30.0 1.44 0.13 0.08 0.02 0.00 0.00 ---- ---- 78.5 20

Table II-B Radiation Errors: Wind Sixty Degrees from Perpendicular, from Junction Side; Radiation Perpendicular from Junction Side Radiation Elev. angle Intensity Wind speed, mph Temp. Degrees ly/min 4.3 5.8 8.0 10.1 13.7 18.4 23.3 28.2 33.9 deg. F. O.o 0.87 1.02 0.88 0.71 0.63 0.55 --- ---- 78.0 0.0 0.87 ---- ---- ---- ----. o.49 0.44 0.42 0.40 77.0 0.0 1.10 ---- ---- --— 0.70 0.58 0.53 o.49 0.46 77.0 0.0 1.44 1.60 1.39 1.12 1.02 0.86 ---- ---- ---- ---- 78.0 0.0 1.44 ---- ---- ---- ---- 0.84 0.75 0.66 0.60 o.58 77~0 5.0 0.87 1.00oo 084 0.66 0.57 0.52 ---- ---- ---- ---- 78.0 5.0 0.87 ---- ---- ---- ---- o.58 0.49 0.47 0.42 0.38 77.0 10.0 0.87 0.95 0.75 0.57 0.46 0.40 ---- ---- ---- -- 78.0 10.0 0.87 ---- ---- - ---- o0.49 0.42 0.38 0.33 0.31 77.0 10.0 1.44 1.24 1.06 0.86 0.75 0.66 --- - ---- 78.0 10.0 1.44 ---- --- ---- ---- 0.71 0.62 0.53 0.49 0.46 77.0 15.0 1.10 0.75 o0.60 0.49 0.42 0.35 ---- ---- ---- 77.0 15.0 1.10 ---- ---- ---- 0.39 0.33 0.30 0.26 0.22 77.0 15.0 1,44 1.22 0.97 0.80 0.69 0.62 ---- ---- - 77.0 15.0 1.44 ---- ---- ---- ---- 0.42 0.35 0.31 0.27 0.24 77o0 20.0 1.44 0.42 0.27 0.15 0.12 ---- ---- ---- ---- 77.0 20.0 1.44 ---- ---- ---- ---- 0.08 o.o5 0.04 ---- 0.04 77.0 20.0 1.94 0.57 0.49 0.35 0.27 0.24 ---- ---- ---- ---- 77.0 20.0 1.94 - -- - 0.20 0.17 0.14 ---- o.11 77,0 30.0 1.44 0.09 0.02 0.02 0.00 0.00 ---- ---- ---- ---- 77.0 30.0 1.44 ---- --- ---- ---- 0.02 0.00 0.00 ---- 0.00 77.0 21

Table II-C Radiation Errors: Wind Sixty Degrees from Perpendicular, from Junction Side; Radiation Parallel to Probe from End Opposite Connector Radiation Elev. angle Intensity Wind speed, mph Temp. Degrees ly/min 4.3 5.8 8.0 10.1 13.7 18.4 23.3 28.2 33.9 deg. F. 0.0 1.10 0.24 0.15 0.09 0.07 004 ---- -- - - 775 10.0 1.10 0. 11 0,07 0.02 0.00 0.00 - 77.5 20.0 1.44 0.11 0.07 0.02 0.00 0.00 ---- ---- ---- ---- 77.5 Table III-A Radiation Errors: Wind Parallel to Probe from End Opposite Connector; Radiation Perpendicular to Probe from Side Opposite Junction Radiation Elev. angle Intensity Wind speed, mph Temp. Degrees ly/min 4.3 5.8 8.0 10.1 13.7 18.4 23.3 28.2 33o9 deg. F. 0.0 1.44 4.24 2.70 1.52 1.32 10o8 ---- 80.0 0 0 1.44 ---- 2.79 1.72 ---- ---- ---- ---- ---- ---- 80.0 22

Table IV Temperature Corrections in Degrees F., for Selected Periods at the Amundsen-Scott South Pole Station (Values to be subtracted from observed data) Date Wind speed, mph 4.3 5.8 8.0 10.0 13.7 18.4 23.3 28.2 33.5 2 March (a) 1.00* 0.90* 0.70* 0.62 0.55 0.45 0.42 0.38 0.33 (b) 0.88 0.72 0.51 0.44 0.37 0.33 0.30 0.30 0.28 4, 5, 6 (a) 0.79 0.67 0.52 0.45 0.38 0.36 0.30 0.30 0.30 March (b) 0.93 0. 74. 54. 48 0.38 0. 35 0. 33 0. 30 0.28 5, 8, 9 (a) 1.20 0.95 o.80 0.70 0.50 0.35 0.30 0.25 0.25 November (b) 0.50 0. 35 0.25 0.20 0.13 0.09. 08. 08. 08 6 November (a) 0.91 0.71 0.58 0.50 0.38 0.25 0.22 0.21 0.20 (b) 0.32 0.24 0.13 0.10 0.09 0.09 0.09 0.09 0.09 10, 13 (a) 0.78 0.59 0.46 0.38 0.30 0.19 0.17 0-.14 November (b) 0.38 0.28 0.19 0.15 0.10 0.08 0.07 0.07 0.07 (c) 0.49 0.40 0.24 0.18 0.14 ---- ---- ---- ---- (d) 0.20 0.11 0.02 0.01 --- ---- ---- ---- ---- 16, 17 (a) 0.31 0.22 0. 0. 12 0.09 0.07 0.05 0.05 0.05 November (b) 0.28. 17 0.10 0.06 0.05 0.0 0. 04. 04 0o 03 (c) o.49 o.40 0.24 0.18 0.14 ---- ---- ---- (d) 0.20 0.11 o.o4 0.02 0.01 ---- ---- ---- ---- *Extrapolated value. (a) Radiation from junction side of probe. (b) Radiation from side opposite junction. (c) Radiation from connector end of probeI (d) Radiation from end opposite connector~ 23

Table V Test Data Used for Compiling Temperature Corrections given in Table IV Date Radiation Intensity, Radiation Elevation Wind Direction ly/min Angle, deg. Relative Thermocouple wire in probe, deg. 2 March (a) 1.10 0 and 15 30 (b) 1,10 5 and 10 30 4, 5, 6 Mar 1.10 and 0.87 5 90 4, 8, 9 Nov 1.44 15 30 6 Nov 1.44 15 90 10, 13 Nov 1o44 15 and 20 30 and 90 16, 17 Nov 1.44 15 and 20 90 24

Table VI Temperature Differences for Nighttime Tests over Snow (AT = U. of M. probe temperature minus QJRD probe temperature) Test Number I II III IVI Date 20 Feb. 1960 20 Feb. 1960 20 Feb. 1960 25Feb. 1960 Time, EST 1920-1929 1937-1946 1948-1958 2026-2050 Sky Condition Clear Clear Clear Clear Net Radiation, ly/m.,in 0.013 0.017 0.020 Probe Arrangement As in Fig. 4(A) As in Fig. 4(A) As in Fig. 4(A) As in Fig. 4(B) Wind Direction, deg. 34o 340 540 550 Temperature, deg. F. -4,0 -4.0 -4.0 1.4 Temp. Gradient, deg. F. 7.0 7,0 7.0 16.0 (T4m - Tl/2m) Sh ie ld Rod Wind Shield Rod Wind Shield Rod Wind Shield Rod Wind R) Probe Probe mph Probe Probe mph Probe Probe mph Probe Probe mph eF OF'OF GF OF OF OF.54.09.41 355 -.25 0,5.50 0.4.45 1.9.41.45 1.8.54.13.51 -.27.63.36.18.05 1,9.49 0.8.18 2.6.51 3.5 -.41 1.8.05.23.23 0.36.09 353.27 -.45 1,9.41.41.51 2.5.18.27 0.9 -.49 0.8.49.05 1.2 -.67.091. -.27 1.8 0 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _-.18 1.9 Averages.44.42 0.7.12.36 2.6.33.28 5.2.12 -.57 1.5 *All probes were covered with frost du-ring test No. Ill.

Figure 1. Side view of shield probe.

Figure 2. Wind tunnel test arrangement, looking upwind. Figure 3. Wind tunnel test arrangement, looking downwind. __~~~~~~2

340~ WIND 330~ WIND Figure 4. Test arrangements over snow. 28

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Two views of test arrangement "B" over snow. 29

1.0o O =4 mph / = 6 mph o o8 mph C = IOmph.9 a=I12mph C =15mph < = 20mph = 25mph:.74 3: RADIATIN0 6INTENSITY speeds; radiation elevation angle of 0.0 degrees5.4-.~-.2.4.5.6.7.8.9 1.0 1.1 1.2 1.5 1.4 1.5 RADIATION INTENSITY,(LY/MIN) Figure 6. Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 0.0 degrees.

1.1 1.0 0 = 4 mph A = 6 mph.9 (i/ = 8 mph El - 10 mph = 12 mph = 15 mph _./ = 20 mph L'' X I= 25mph 0~~ | < (E)~~~~~~~~~~ = 30mph ~k.7 ~.5.4.5.6.7.9 1.0 1.1 1.2 1.3 1.4 1.5 RADIATION INTENSITY, (LY/MIN) Figure 7. Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 5.0 degrees.

.8.7 0 = 4 mph A = 6 mph.6 0= 8 mph El = 10 mph A= 12 mph 0 = 15 mph.5 = 20 mph LL 9 = 25 mph 0 = 30 mph'~.4 (rl a:4 w O~~ ru~~~~c z.2.1 0.5.6.7.8.9 1.0 1.1 1.2 1.3 1.4 1.5 RADIATION INTENSITY. (LY/ MIN) Figure 8. Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 10.0 degrees.

.6.5 L. 0 o 4 mph cz o.3.28 mph lOmph 2mph I t o15mph -. 20mph -25mph 30mph 0 I I I I I I I.8.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 RADIATION INTENSITY, (LY/MIN) Figure 9. Radiation errors versus radiation intensity for different wind speeds; radiation elevation angle of 15.0 degrees.

.4 0 0 o~~~~~~~~~~~~~~~~~~ 6 mph 0 *~~~~~~~~~~~~~~~~~~~~~~- 8 m ph It~~~~~~~~~~~~~~~~~~~~~p * 12 mph O - 1~~~~~~~~~~~~*5 mph 20'25,30 mph lc0 1.' L2 ~1.3 1.4 1.5 1.6 5,.8. Figure lo.RADII\rION INrENsiry. (LY/MIN) Figuees i.radiation errators versus radiation intensity for different wind speeds; radiation elevation2angle of 20.0 degrees.

NORTH NNE NE 600 30 ~ENE 600 ____EAST Figure 11. Probe orientation at South Pole Station. 20 200 Figure 12. Thermocouple junction position in shield with respect to elevation angles.

2.0 1.5 1.0 LL cr 0.5 z 0 0.I 0.1 I I I I I I I I I I i I I 1 1 I I 5 10 50 100 WIND SPEED (mph) Figure 13. Radiation Errors versus Wind Speed. (Data from Figure 5 for radiation intensity = 1.44 ly/min.)