Rethinking convective quasi-equilibrium: observational constraints for stochastic convective schemes in climate models Export

@article{citeulike:5193566, abstract = {10.1098/rsta.2008.0056 Convective quasi-equilibrium (QE) has for several decades stood as a key postulate for parametrization of the impacts of moist convection at small scales upon the large-scale flow. Departures from QE have motivated stochastic convective parametrization, which in its early stages may be viewed as a sensitivity study. Introducing plausible stochastic terms to modify the existing convective parametrizations can have substantial impact, but, as for so many aspects of convective parametrization, the results are sensitive to details of the assumed processes. We present observational results aimed at helping to constrain convection schemes, with implications for each of conventional, stochastic or \^{a}€˜superparametrization\^{a}€™ schemes. The original vision of QE due to Arakawa fares well as a leading approximation, but with a number of updates. Some, like the imperfect connection between the boundary layer and the free troposphere, and the importance of free-tropospheric moisture to buoyancy, are quantitatively important but lie within the framework of ensemble-average convection slaved to the large scale. Observations of critical phenomena associated with a continuous phase transition for precipitation as a function of water vapour and temperature suggest a more substantial revision. While the system's attraction to the critical point is predicted by QE, several fundamental properties of the transition, including high precipitation variance in the critical region, need to be added to the theory. Long-range correlations imply that this variance does not reduce quickly under spatial averaging; scaling associated with this spatial averaging has potential implications for superparametrization. Long tails of the distribution of water vapour create relatively frequent excursions above criticality with associated strong precipitation events.}, author = {Neelin, J. David and Peters, Ole and Lin, Johnny W. B. and Hales, Katrina and Holloway, Christopher E.}, citeulike-article-id = {5193566}, citeulike-linkout-0 = {http://dx.doi.org/10.1098/rsta.2008.0056}, citeulike-linkout-1 = {http://rsta.royalsocietypublishing.org/content/366/1875/2579.abstract}, citeulike-linkout-2 = {http://rsta.royalsocietypublishing.org/content/366/1875/2579.full.pdf}, day = {28}, doi = {10.1098/rsta.2008.0056}, journal = {Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences}, keywords = {assimilation, atmosphere, boundary-layer, circulation, climate, convection, dynamics, gcm, model, parameterization, precipitation, stochastic, superparameterization, troposphere, water-vapor}, month = {July}, number = {1875}, pages = {2579--2602}, posted-at = {2009-07-17 17:54:09}, priority = {2}, title = {Rethinking convective quasi-equilibrium: observational constraints for stochastic convective schemes in climate models}, url = {http://dx.doi.org/10.1098/rsta.2008.0056}, volume = {366}, year = {2008} }

TY - JOUR ID - citeulike:5193566 L3 - citeulike-article-id:5193566 N2 - 10.1098/rsta.2008.0056 Convective quasi-equilibrium (QE) has for several decades stood as a key postulate for parametrization of the impacts of moist convection at small scales upon the large-scale flow. Departures from QE have motivated stochastic convective parametrization, which in its early stages may be viewed as a sensitivity study. Introducing plausible stochastic terms to modify the existing convective parametrizations can have substantial impact, but, as for so many aspects of convective parametrization, the results are sensitive to details of the assumed processes. We present observational results aimed at helping to constrain convection schemes, with implications for each of conventional, stochastic or ‘superparametrization’ schemes. The original vision of QE due to Arakawa fares well as a leading approximation, but with a number of updates. Some, like the imperfect connection between the boundary layer and the free troposphere, and the importance of free-tropospheric moisture to buoyancy, are quantitatively important but lie within the framework of ensemble-average convection slaved to the large scale. Observations of critical phenomena associated with a continuous phase transition for precipitation as a function of water vapour and temperature suggest a more substantial revision. While the system's attraction to the critical point is predicted by QE, several fundamental properties of the transition, including high precipitation variance in the critical region, need to be added to the theory. Long-range correlations imply that this variance does not reduce quickly under spatial averaging; scaling associated with this spatial averaging has potential implications for superparametrization. Long tails of the distribution of water vapour create relatively frequent excursions above criticality with associated strong precipitation events. IS - 1875 JF - Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences EP - 2602 TI - Rethinking convective quasi-equilibrium: observational constraints for stochastic convective schemes in climate models VL - 366 SP - 2579 KW - assimilation KW - atmosphere KW - boundary-layer KW - circulation KW - climate KW - convection KW - dynamics KW - gcm KW - model KW - parameterization KW - precipitation KW - stochastic KW - superparameterization KW - troposphere KW - water-vapor AU - Neelin, David AU - Peters, Ole AU - Lin, Johnny AU - Hales, Katrina AU - Holloway, Christopher PY - 2008/07/28/ UR - http://dx.doi.org/10.1098/rsta.2008.0056 ER -