TY  - JOUR
A1  - Anurose, Theethai-Jacob
A1  - Bašták Ďurán, Ivan
A1  - Schmidli, Jürg
A1  - Seifert, Axel
T1  - Understanding the moisture variance in precipitating shallow cumulus convection
T2  - JGR. Atmospheres
N2  - The impact of precipitation in shallow cumulus convection on the moisture variance and third-order moments of moisture is investigated with the help of large-eddy simulations. Three idealized simulations based on the Rain in Cumulus over the Ocean field experiment are analyzed: one nonprecipitating, on a smaller domain, and two precipitating cases, on a larger domain with different initial profiles of moisture. Results show that precipitation and the associated cloud organization lead to increased generation of higher-order moments (HOM) of moisture compared to the nonprecipitating case. To understand the physical mechanism and the role of individual processes in this increase, budgets of HOM of moisture are studied. Microphysics directly decreases the generation of HOM of moisture, but this effect is not dominant. The gradient production term is identified as the main source term in the HOM budgets. The influence of the gradient production term on moisture variance is further examined separately in cloud active and nonactive regions. The main contribution to the gradient production term comes from the smaller cloud active region because of the stronger moisture flux. Further analyses of the horizontal and vertical cross sections of moisture fluctuations show that the precipitation-induced downdrafts and updrafts are the main mechanism for the generation of moisture variance. The variance increase is linked to shallow dry downdraft regions with horizontal divergence in the subcloud layer, moist updrafts with horizontal convergence in the bulk cloud layer, and finally wider areas of horizontal divergence in the cloud inversion layer.
KW  - Large eddy simulation
KW  - Atmospheric boundary layer
KW  - Turbulent budget
KW  - Shallow cumulus convection
Y1  - 2019
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/63824
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-638249
SN  - 2169-8996
N1  - This study was supported by the Federal Ministry of Education and Research in Germany (Bundesministerium fr Bildung und Forschung; BMBF) through the research program High Definition Clouds and Precipitation for Climate Prediction-HD(CP)2. The simulations were performed on LOEWE supercomputing and MISTRAL, DKRZ, Hamburg, Germany. Ivan Bastak Duran and Juerg Schmidli were supported by the Hans Ertel Centre for Weather Research.
N1  - The data for this study were generated with the LES model MicroHH, openly available in Zenodo at https://doi.org/10.5281/zenodo.822842 (van Heerwaarden et al., 2017b). The configuration files and output statistics of the three simulations (STD, MST, and CTRL) are openly available in Zenodo at http://doi.org/10.5281/zenodo.3472616 (Bastak Duran et al., 2019).
VL  - 125
IS  - 1, art. e2019JD031178
SP  - 1
EP  - 20
PB  - Wiley
CY  - Hoboken, NJ
ER  -