Temperature-Induced Errors in the ML-476 Humidity Data

Morrissey, James F.; Brousaides, Frederick J.

doi:10.1175/1520-0450(1970)009<0805:tieitm>2.0.co;2

Cited by 23 publications

(18 citation statements)

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“…For this reason, we choose T, as a base series. The above computations were based on the 1200 GCT (nighttime) data in order to avoid contamination due to the large instrument errors in the daytime soundings [Morrissey and Brousaides, 1970;Colton, 1970]. In order to investigate the effect of this instrument error, the same computations were performed on the 0000-GCT soundings.…”

Section: Meridional Wind Component We Begin By Showing Inmentioning

confidence: 99%

Spectral studies of tropospheric wave disturbances in the tropical western Pacific

Wallace¹

1971

Reviews of Geophysics

128

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Tropospheric wave disturbances in the tropical western Pacific have been subjected to intensive analysis during three separate seasons. These all show evidence of spectral peaks in the 4‐ to 5‐day range and at periods longer than 10 days. In this review I attempt to synthesize the results for these three seasons, together with the analysis of a fourth season, into a tentative description of the various types of wave disturbances in this region. The conclusions are outlined below. It appears that there are two types of tropical disturbances that contribute to the 4‐ to 5‐day peaks: synoptic‐scale, westward‐propagating waves with phase speeds on the order of 6‐7 degrees per day, and planetary‐scale equatorial waves that extend into the lower stratosphere. There are also one or more wave types associated with the low‐frequency spectral peaks. All the tropical waves exhibit a similar vertical structure, with a phase reversal in the wind field between upper and lower troposphere. There are warm temperature anomalies at 300 mb, above the low‐level troughs, in qualitative agreement with the thermal‐wind equation. These warm anomalies coincide with the regions of maximum rising motion. As distinguished from tropical waves, the subtropical disturbances do not exhibit a phase reversal in the wind field between upper and lower tropospheric levels. The troughs of these waves appear to be colder than their surroundings at 300 mb. The available potential energy the tropical waves derive from condensation heating is immediately converted into kinetic energy by the synoptic‐scale divergent wind field. This appears to be the dominant energy source for these waves. The leakage of wave energy upward through the tropopause appears to be at least an order of magnitude smaller than the rate of energy generation. The spectral results indicate that most of the synoptic‐scale mass convergence into regions of disturbed weather takes place above the subcloud layer. Although the vertical distribution of latent heat release displays the same gross features in different regions, a simple linear proportionality between boundary‐layer convergence and condensation heating (as is usually assumed in the CISK hypothesis) does not appear to exist.

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Section: Meridional Wind Component We Begin By Showing Inmentioning

confidence: 99%

Spectral studies of tropospheric wave disturbances in the tropical western Pacific

Wallace¹

1971

Reviews of Geophysics

128

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“…3 Jounal of the Meteorological Society of Japanh is the convective heat-transfer coefficient, and A is the total surface area of the sensor. Morrissey and Brousaides (1970) proposed that, assuming that the RH sensor is a flat plate with a zero angle of attack to airflow, h can be calculated from…”

Section: Estimation Of Thermal Lag For the Rs-06g Rh Sensormentioning

confidence: 99%

“…Among these errors, the thermal lag of the RH sensor is caused by the finite time required for RH sensors to reach equilibrium with the changing ambient air temperature during flight (e.g., Morrissey and Brousaides 1970;Williams and Acheson 1976;WMO 2008). In this study, we also investigate the thermal lag of the RS-06G RH sensor using a laboratory-based thermostatic chamber test.…”

Section: Introductionmentioning

confidence: 99%

Correction of the Stepwise Change Observed at 0°C in Meisei RS2-91, RS-01G, and RS-06G Radiosonde Relative Humidity Profiles

Sugidachi

Fujiwara

2013

Journal of the Meteorological Society of Japan

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Comparisons of relative humidity (RH) measurements between the Meisei RS-06G radiosonde and a chilled-mirror hygrometer revealed that the RS-06G radiosonde shows a stepwise change of~3% RH at 0°C (drying when air temperature is decreasing). This is due to a discontinuous correction factor in the processing software that compensates for the temperature dependence of the RH sensor. Results from chamber experiments regarding the temperature and RH dependence of RS-06G RH sensors under steady-state conditions showed a wet bias exceeding 7% RH below +10°C. As this result contradicted previous in-flight intercomparisons that used the original manufacturerʼs correction, we investigated a possible additional dry bias caused by a thermal lag in the RH sensor. We speculated that the thermal lag of the RH sensor typically causes a dry bias during a tropospheric ascent, which largely compensates for the wet bias related to the temperature and RH dependence of the RH sensor. We observed that the experimental results of the temperature and RH dependence considering the thermal lag were in agreement with the extrapolation of the original manufacturerʼs correction. Consequently, we proposed to extrapolate the original manufacturerʼs correction, which is currently applied at temperatures between −40°C and 0°C, up to +14.5°C to resolve the artificial stepwise change at 0°C. Because the RS-06G radiosonde is a successor to the Meisei RS-01G and RS2-91 radiosondes, which have adopted the same RH sensor material installed since July 1999 and have used the same processing software, the current results should be applied to the data obtained by those radiosondes. The bias of RS-06G RH measurements using this new correction is estimated to be within 7% RH, which is within the manufacturerʼs specifications, being drier at +40°C and wetter between −40°C and +10°C.

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“…In radiosonde applications the air temperature is measured using the thermistor (Figure 1). The current shape of the duct was the result of a redesign In the early 70's due to the work of Morrissey and Brousaides,4 quantifying the magnitude of the temperature-induced errors using the earlier duct. The principal differences between the old and new ducts are an extended curved exit, blackening of the inside walls and a secondary air path beneath the duct.…”

Section: Introductionmentioning

confidence: 99%

A Proposed Improved Method of Radiosonde Humidity Sensing

Morrissey¹

1991

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Temperature-Induced Errors in the ML-476 Humidity Data

Cited by 23 publications

References 0 publications

Spectral studies of tropospheric wave disturbances in the tropical western Pacific

Spectral studies of tropospheric wave disturbances in the tropical western Pacific

Correction of the Stepwise Change Observed at 0°C in Meisei RS2-91, RS-01G, and RS-06G Radiosonde Relative Humidity Profiles

A Proposed Improved Method of Radiosonde Humidity Sensing

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