Radiatively driven convection in icecovered lakes: Observations, scaling, and a mixed layer model
(2002) In Journal of Geophysical Research 107(C4). Abstract
 Penetrative convection is discussed where the instability is driven by radiative heating of water below the temperature of maximum density. Convection of this type occurs in icecovered freshwater lakes in late spring, when the snow cover vanishes and solar radiation is absorbed beneath the ice cover. The vertical temperature structure, bulk mixed layer scaling, and mixed layer deepening are examined for a number of temperate and polar lakes. A bulk mixed layer scaling for this type of convection is based on energy arguments underlying the classical Deardorff convective scaling. The depth of the convective layer serves as an appropriate length scale. However, a modified scale that takes account of the energetics of a distributed radiation... (More)
 Penetrative convection is discussed where the instability is driven by radiative heating of water below the temperature of maximum density. Convection of this type occurs in icecovered freshwater lakes in late spring, when the snow cover vanishes and solar radiation is absorbed beneath the ice cover. The vertical temperature structure, bulk mixed layer scaling, and mixed layer deepening are examined for a number of temperate and polar lakes. A bulk mixed layer scaling for this type of convection is based on energy arguments underlying the classical Deardorff convective scaling. The depth of the convective layer serves as an appropriate length scale. However, a modified scale that takes account of the energetics of a distributed radiation source term replaces the surface buoyancy flux velocity scale used by Deardorff. The scaling compares favorably with largeeddy simulations of turbulence kinetic energy (TKE) and with both observations and largeeddy simulations of the TKE dissipation rate. Mixed layer deepening is simulated with a model of convection beneath lake ice. The model describes the structure of the stably stratified layer just beneath the ice with a stationary solution to the heat transfer equation; the structure of the entrainment layer is parameterized with a zeroorder jump approach. The entrainment equation is derived from the mixed layer TKE budget and bulk mixed layer scaling. Entrainment regimes characteristic of convection beneath ice are analyzed. It is shown that if the Deardorff convective velocity scale is replaced with a scale incorporating the distributed buoyancy flux, the entrainment equation describing atmospheric and oceanic convective boundary layers also applies beneath the ice. Model predictions compare well with data from observations in a number of lakes. We propose and compare with observations an extension of the mixed layer model that allows for the inclusion of salinity. Although the salt concentration is low in most temperate and polar lakes, its dynamical effect can be significant close to the temperature of maximum density. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/324743
 author
 Mironov, D; Terzhevik, A; Kirillin, G; Jonas, T; Malm, Joakim ^{LU} and Farmer, D
 organization
 publishing date
 2002
 type
 Contribution to journal
 publication status
 published
 subject
 keywords
 scaling, convection, icecovered lake, mixed layer model
 in
 Journal of Geophysical Research
 volume
 107
 issue
 C4
 publisher
 American Geophysical Union
 external identifiers

 wos:000178923600001
 scopus:0037092388
 ISSN
 21562202
 DOI
 10.1029/2001JC000892
 language
 English
 LU publication?
 yes
 id
 1f900905760b4085a067e4c63d33abb6 (old id 324743)
 date added to LUP
 20071102 12:01:35
 date last changed
 20170903 03:45:03
@article{1f900905760b4085a067e4c63d33abb6, abstract = {Penetrative convection is discussed where the instability is driven by radiative heating of water below the temperature of maximum density. Convection of this type occurs in icecovered freshwater lakes in late spring, when the snow cover vanishes and solar radiation is absorbed beneath the ice cover. The vertical temperature structure, bulk mixed layer scaling, and mixed layer deepening are examined for a number of temperate and polar lakes. A bulk mixed layer scaling for this type of convection is based on energy arguments underlying the classical Deardorff convective scaling. The depth of the convective layer serves as an appropriate length scale. However, a modified scale that takes account of the energetics of a distributed radiation source term replaces the surface buoyancy flux velocity scale used by Deardorff. The scaling compares favorably with largeeddy simulations of turbulence kinetic energy (TKE) and with both observations and largeeddy simulations of the TKE dissipation rate. Mixed layer deepening is simulated with a model of convection beneath lake ice. The model describes the structure of the stably stratified layer just beneath the ice with a stationary solution to the heat transfer equation; the structure of the entrainment layer is parameterized with a zeroorder jump approach. The entrainment equation is derived from the mixed layer TKE budget and bulk mixed layer scaling. Entrainment regimes characteristic of convection beneath ice are analyzed. It is shown that if the Deardorff convective velocity scale is replaced with a scale incorporating the distributed buoyancy flux, the entrainment equation describing atmospheric and oceanic convective boundary layers also applies beneath the ice. Model predictions compare well with data from observations in a number of lakes. We propose and compare with observations an extension of the mixed layer model that allows for the inclusion of salinity. Although the salt concentration is low in most temperate and polar lakes, its dynamical effect can be significant close to the temperature of maximum density.}, author = {Mironov, D and Terzhevik, A and Kirillin, G and Jonas, T and Malm, Joakim and Farmer, D}, issn = {21562202}, keyword = {scaling,convection,icecovered lake,mixed layer model}, language = {eng}, number = {C4}, publisher = {American Geophysical Union}, series = {Journal of Geophysical Research}, title = {Radiatively driven convection in icecovered lakes: Observations, scaling, and a mixed layer model}, url = {http://dx.doi.org/10.1029/2001JC000892}, volume = {107}, year = {2002}, }