Details
| Original language | English |
|---|---|
| Pages (from-to) | 349-368 |
| Number of pages | 20 |
| Journal | Meteorologische Zeitschrift |
| Volume | 23 |
| Issue number | 4 |
| Early online date | 27 Aug 2014 |
| Publication status | Published - 26 Sept 2014 |
Abstract
This study combines observations, large-eddy simulations (LES), and direct numerical simulations (DNS) in order to analyze entrainment and mixing in shallow cumulus clouds at all relevant spatial scales and, additionally, to verify the results by the multiple methods used. The observations are based on three flights of the CARRIBA campaign which are similar to the classical BOMEX case used for LES. Virtual flights in the LES data are used to validate the observational method of line measurements. It is shown that line measurements overrepresent the cloud core, and it is quantified how derived statistics depend on small perturbations of the flight track, which has to be taken in account for the interpretation of airborne observations. A linear relation between fluctuations of temperature and liquid water content has been found in both LES and observations in a good quantitative agreement. However, the constant of proportionality deviates from purely adiabatic estimates, which can be attributed to cloud edge mixing. The cloud edge is compared in detail in observations and LES, which agree qualitatively although the LES cloud edge is smoother due to the model's resolution. The resulting typical amplitudes of the turbulence fields from this comparison are compared with the large-scale forcing model which is used in a series of DNS which study the mixing below the meter scale, which show that LES does not resolve the intermittency of small-scale turbulence.
Keywords
- Airborne observations, Cumulus clouds, Direct numerical simulations, Entrainment and mixing, Large-eddy simulations
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Atmospheric Science
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In: Meteorologische Zeitschrift, Vol. 23, No. 4, 26.09.2014, p. 349-368.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Entrainment and mixing at the interface of shallow cumulus clouds
T2 - Results from a combination of observations and simulations
AU - Hoffmann, Fabian
AU - Siebert, Holger
AU - Schumacher, Jörg
AU - Riechelmann, Theres
AU - Katzwinkel, Jeannine
AU - Kumar, Bipin
AU - Götzfried, Paul
AU - Raasch, Siegfried
N1 - Funding sponsor: Deutsche Forschungsgemeinschaft Fundning number: SI 1534/3 Institution of Civil Engineers
PY - 2014/9/26
Y1 - 2014/9/26
N2 - This study combines observations, large-eddy simulations (LES), and direct numerical simulations (DNS) in order to analyze entrainment and mixing in shallow cumulus clouds at all relevant spatial scales and, additionally, to verify the results by the multiple methods used. The observations are based on three flights of the CARRIBA campaign which are similar to the classical BOMEX case used for LES. Virtual flights in the LES data are used to validate the observational method of line measurements. It is shown that line measurements overrepresent the cloud core, and it is quantified how derived statistics depend on small perturbations of the flight track, which has to be taken in account for the interpretation of airborne observations. A linear relation between fluctuations of temperature and liquid water content has been found in both LES and observations in a good quantitative agreement. However, the constant of proportionality deviates from purely adiabatic estimates, which can be attributed to cloud edge mixing. The cloud edge is compared in detail in observations and LES, which agree qualitatively although the LES cloud edge is smoother due to the model's resolution. The resulting typical amplitudes of the turbulence fields from this comparison are compared with the large-scale forcing model which is used in a series of DNS which study the mixing below the meter scale, which show that LES does not resolve the intermittency of small-scale turbulence.
AB - This study combines observations, large-eddy simulations (LES), and direct numerical simulations (DNS) in order to analyze entrainment and mixing in shallow cumulus clouds at all relevant spatial scales and, additionally, to verify the results by the multiple methods used. The observations are based on three flights of the CARRIBA campaign which are similar to the classical BOMEX case used for LES. Virtual flights in the LES data are used to validate the observational method of line measurements. It is shown that line measurements overrepresent the cloud core, and it is quantified how derived statistics depend on small perturbations of the flight track, which has to be taken in account for the interpretation of airborne observations. A linear relation between fluctuations of temperature and liquid water content has been found in both LES and observations in a good quantitative agreement. However, the constant of proportionality deviates from purely adiabatic estimates, which can be attributed to cloud edge mixing. The cloud edge is compared in detail in observations and LES, which agree qualitatively although the LES cloud edge is smoother due to the model's resolution. The resulting typical amplitudes of the turbulence fields from this comparison are compared with the large-scale forcing model which is used in a series of DNS which study the mixing below the meter scale, which show that LES does not resolve the intermittency of small-scale turbulence.
KW - Airborne observations
KW - Cumulus clouds
KW - Direct numerical simulations
KW - Entrainment and mixing
KW - Large-eddy simulations
UR - http://www.scopus.com/inward/record.url?scp=84925458208&partnerID=8YFLogxK
U2 - 10.1127/0941-2948/2014/0597
DO - 10.1127/0941-2948/2014/0597
M3 - Article
AN - SCOPUS:84925458208
VL - 23
SP - 349
EP - 368
JO - Meteorologische Zeitschrift
JF - Meteorologische Zeitschrift
SN - 0941-2948
IS - 4
ER -