Overestimates of Entrainment From Wetting of Aircraft Temperature Sensors in Cloud

Heymsfield, Andrew J.; Dye, J. E.; Biter, Cleon J.

doi:10.1175/1520-0450(1979)018<0092:ooefwo>2.0.co;2

Cited by 26 publications

(12 citation statements)

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“…Measurements of temperature inside clouds can be inaccurate as a result of wetting or icing of the sensor (e.g. Lenschow and Pennell 1974;Heyms eld 1979). Therefore, the measured temperatures during SCMS ight RF12 as used in this paper were corrected by Rodts et al (submitted to J. Atmos.…”

Section: Instrumentation and Observations In Scmsmentioning

confidence: 99%

Shallow cumulus convection: A validation of large‐eddy simulation against aircraft and Landsat observations

Neggers

Duynkerke²,

Rodts³

2003

Quart J Royal Meteoro Soc

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SUMMARYLarge-eddy simulation (LES) results of shallow cumulus convection are directly evaluated against in-cloud aircraft measurements, as made during the Small Cumulus Microphysics Study (SCMS). To this purpose an LES case is rst constructed, based on available observations (during SCMS). Then the simulations are directly compared with the in-cloud measurements by using conditionally sampled elds. An advantage of the SCMS dataset is the combination of a range of different surface measurements, in-cloud measurements by an aircraft at many levels in the cloud layer, and the availability of high-resolution Landsat images.The results show that given the correct initial and boundary conditions the LES concept is capable of realistically predicting the bulk thermodynamic properties of temperature, moisture and liquid-water content of the cumulus-cloud ensemble as observed in SCMS. Furthermore, the vertical component of the in-cloud turbulent kinetic energy and the cloud size distribution in LES were in agreement with the observations. These results support the credibility of cloud statistics as produced by LES in general, and encourage its use as a tool for testing hypotheses and developing parametrizations of shallow cumulus cloud processes.Several hypotheses which make use of conditionally sampled elds were tested on the SCMS data. The magnitudes and the decrease with height of the bulk entrainment rate following from the SCMS data con rm the typical values of the order of magnitude of 10 ¡3 m ¡1 as reported in several other recent LES studies. An alternative formulation of the lateral entrainment rate as a function of the liquid-water content and the mean lapse rate agrees well with the original form based on the conserved variables. Applying an often-used simpli ed equation for the cloud vertical velocity to the aircraft measurements results in a reasonably closed budget.

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Section: Instrumentation and Observations In Scmsmentioning

confidence: 99%

Shallow cumulus convection: A validation of large‐eddy simulation against aircraft and Landsat observations

Neggers

Duynkerke²,

Rodts³

2003

Quart J Royal Meteoro Soc

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“…The temperature and humidity measurements are used to calculate relative humidity in cloud-free air. The temperature measurement in cloud was subject to significant wetting effects that led to a cold bias, as illustrated by Heymsfield et al (1979). The derived in-cloud relative humidity is therefore set to 100% in this work.…”

Section: Case Study and Aircraft Measurementsmentioning

confidence: 99%

Improving aerosol activation in the double-moment Unified Model with CLARIFY measurements

Gordon

Field

Abel

et al. 2020

Preprint

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<p><strong>Abstract.</strong> Representing the number and mass of cloud and aerosol particles independently in a climate, weather prediction or air quality model is important in order to simulate aerosol direct and indirect effects on radiation balance. Here we introduce the first configuration of the UK Met Office Unified Model in which both cloud and aerosol particles have <q>double-moment</q> representations with prognostic number and mass. The GLOMAP aerosol microphysics scheme, already used in the HadGEM3 climate configuration, is coupled to the CASIM cloud microphysics scheme. We demonstrate the performance of the new configuration in cloud-resolving simulations of a case study defined from the CLARIFY aircraft campaign in 2017 near Ascension Island in the tropical south Atlantic. We improve the physical basis of the activation scheme by representing the effect of existing cloud droplets on the activation of new aerosol, and we also attempt to account for the effect of unresolved vertical velocities. The first of these improvements should be applicable to the representation of aerosol activation in other microphysics schemes. While these changes lead only to a modest improvement in model performance, they reinforce our confidence in the ability of the model to simulate aerosol-cloud microphysical interactions. Capturing these interactions accurately is critical to simulating aerosol effects on climate.</p>

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“…Measurement of temperature in cloud has been challenging because immersion sensors can become wet and, in the dynamically heated airflow, experience wet-bulb cooling to a variable extent dependent on the wetting (e.g. Heymsfield et al, 1979;Wang and Geerts, 2009). If the measurement of temperature available from LAMS remains valid in cloud, it can provide important information on the buoyancy of clouds and would support studies of entrainment via mixing-diagram analysis of the type undertaken by Paluch (1979) or Betts (1983), which can be compromised when using conventional temperature sensors.…”

Section: Using the Lams To Measure Temperaturementioning

confidence: 99%

Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor

et al. 2014

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Abstract.A new laser air-motion sensor measures the true airspeed with a standard uncertainty of less than 0.1 m s −1 and so reduces uncertainty in the measured component of the relative wind along the longitudinal axis of the aircraft to about the same level. The calculated pressure expected from that airspeed at the inlet of a pitot tube then provides a basis for calibrating the measurements of dynamic and static pressure, reducing standard uncertainty in those measurements to less than 0.3 hPa and the precision applicable to steady flight conditions to about 0.1 hPa. These improved measurements of pressure, combined with high-resolution measurements of geometric altitude from the global positioning system, then indicate (via integrations of the hydrostatic equation during climbs and descents) that the offset and uncertainty in temperature measurement for one research aircraft are +0.3 ± 0.3 • C. For airspeed, pressure and temperature, these are significant reductions in uncertainty vs. those obtained from calibrations using standard techniques. Finally, it is shown that although the initial calibration of the measured static and dynamic pressures requires a measured temperature, once calibrated these measured pressures and the measurement of airspeed from the new laser air-motion sensor provide a measurement of temperature that does not depend on any other temperature sensor.

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Overestimates of Entrainment From Wetting of Aircraft Temperature Sensors in Cloud

Cited by 26 publications

References 0 publications

Shallow cumulus convection: A validation of large‐eddy simulation against aircraft and Landsat observations

Shallow cumulus convection: A validation of large‐eddy simulation against aircraft and Landsat observations

Improving aerosol activation in the double-moment Unified Model with CLARIFY measurements

Calibrating airborne measurements of airspeed, pressure and temperature using a Doppler laser air-motion sensor

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