Organization of tropical convection in low vertical wind shears: Role of updraft entrainment

Abstract

Radiative-convective equilibrium simulations with a 2 km horizontal resolution are conducted to investigate the impact on convective organization of different parameterizations for horizontal and vertical subgrid turbulence mixing. Three standard approaches for representing horizontal diffusion produce starkly differing mixing rates, particularly for the entrainment mixing into updrafts, which differ by more than an order of magnitude between the schemes. The simulations demonstrate that the horizontal subgrid mixing of water vapor is key, with high mixing rates a necessary condition for organization of convection to occur, since entrainment of dry air into updrafts suppresses convection. It is argued that diabatic budgets, while demonstrating the role of spatially heterogeneous radiative heating rates in driving organization, can overlook the role of physical processes such as updraft entrainment. These results may partially explain previous studies that showed that organization is more likely to occur at coarser resolutions, when entrainment is solely represented by subgrid-scale turbulence schemes, highlighting the need for benchmark simulations of higher horizontal resolution. The recommendation is for the use of larger ensembles to ensure robustness of conclusions to subgrid-scale parameterization assumptions when numerically investigating convective organization, possibly through a coordinated community model intercomparison effort.

References Arakawa, A., and W. H. Shubert (1974), Interaction of a cumulus ensemble with the large- scale environment: Part 1, J. Atmos. Sci., 31, 674–701. Benner, T. C., and J. A. Curry (1998), Characteristics of small tropical cumulus clouds and their impact on the environment, J. Geophys. Res., 103, 28,753–28,767. Bretherton, C. S., and P. K. Smolarkiewicz (1989), Gravity waves, compensating subsidence and detrainment around cumulus clouds, J. Atmos. Sci., 46, 740–759. Bretherton, C. S., and M. F. Khairoutdinov (2015), Convective self-aggregation feedbacks in near-global cloud-resolving simulations of an aquaplanet, J. Adv. Model. Earth Syst., 7, 1765–1787, doi:10.1002/2015MS000499. Bretherton, C. S., M. E. Peters, and L. E. Back (2004), Relationships between water vapor path and precipitation over the tropical oceans, J. Clim., 17(7), 1517–1528. Bretherton, C. S., P. N. Blossey, and M. Khairoutdinov (2005), An energy-balance analysis of deep convective self-aggregation above uniform SST, J. Atmos. Sci., 62, 4273–4292. Bryan, G. H. (2005), Spurious convective organization in simulated squall lines owing to moist absolutely unstable layers, Mon. Weather Rev., 133, 1978–1997. Bryan, G. H., J. C. Wyngaard, and J. M. Fritsch (2003), Resolution requirements for the simulation of deep moist convection, Mon. Weather Rev., 131, 2394–2416. Coppin, D., and S. Bony (2015), Physical mechanisms controlling the initiation of convective self-aggregation in a general circulation model, J. Adv. Model. Earth Syst., 7, 2060–2078, doi:10.1002/2015MS000571. Couhert, A., T. Schneider, J. Li, D. E. Waliser, and A. M. Tompkins (2010), The maintenance of the relative humidity in the subtropical free-troposphere, J. Clim., 23, 390–403. Craig, G. C. (1996), Dimensional analysis of a convecting atmosphere in equilibrium with external forcing, Q. J. R. Meteorol. Soc., 122, 1963–1967. Craig, G. C., and B. G. Cohen (2006), Fluctuations in an equilibrium convective ensemble: Part I: Theoretical formulation, J. Atmos. Sci., 63(8), 1996–2004. Craig, G. C., and A. Dörnbrack (2008), Entrainment in cumulus clouds: What resolution is cloud-resolving?, J. Atmos. Sci., 65(12), 3978–3988. Craig, G. C., and J. M. Mack (2013), A coarsening model for self-organization of tropical convection, J. Geophys. Res., 118, 8761–8769, doi:10.1002/jgrd.50674. Cronin, T. W., and K. A. Emanuel (2013), The climate time scale in the approach to radiative-convective equilibrium, J. Adv. Model. Earth Syst., 5, 843–849, doi:10.1002/jame.20049. Dawe, J. T., and P. H. Austin (2013), Direct entrainment and detrainment rate distributions of individual shallow cumulus clouds in an LES, Atmos. Chem. Phys., 13(15), 7795–7811. De Rooy, W. C., P. Bechtold, K. Fröhlich, C. Hohenegger, H. Jonker, D. Mironov, A. Pier Siebesma, J. Teixeira, and J.-I. Yano (2013), Entrainment and detrainment in cumulus convection: An overview, Q. J. R. Meteorol. Soc., 139(670), 1–19. Derbyshire, S. H., I. Beau, P. Bechtold, J.-Y. Grandpeix, J.-M. Piriou, J.-L. Redelsperger, and P. M. M. Soares (2004), Sensitivity of moist convection to environmental humidity, Q. J. R. Meteorol. Soc., 130, 3055–3079. Emanuel, K. A. (1991), A scheme for representing cumulus convection in large-scale models, J. Atmos. Sci., 48, 2313–2335. Emanuel, K. A. (1995), The behavior of a simple hurricane model using a convective scheme based on subcloud-layer entropy equilibrium, J. Atmos. Sci., 52, 3960–3968. Emanuel, K. A., and M. Zivkovic-Rothman (1999), Development and evaluation of a convective scheme for use in climate models, J. Atmos. Sci., 56, 1766–1782. Emanuel, K. A., A. A. Wing, and E. M. Vincent (2014), Radiative-convective instability, J. Adv. Model. Earth Syst., 6, 75–90, doi:10.1002/2013MS000270. Grabowski, W. W., and M. W. Moncrieff (2004), Moisture-convection feedback in the Tropics, Q. J. R. Meteorol. Soc., 130, 3081–3104. Gray, W. M., and R. W. Jacobson Jr. (1977), Diurnal-variation of deep cumulus convection, Mon. Weather Rev., 105, 1171–1188. Hanley, K. E., R. S. Plant, T. H. Stein, R. J. Hogan, J. C. Nicol, H. W. Lean, C. Halliwell, and P. A. Clark (2015), Mixing-length controls on high-resolution simulations of convective storms, Q. J. R. Meteorol. Soc., 141(686), 272–284. Heinze, R., et al. (2016), Large-eddy simulations over Germany using icon: A comprehensive evaluation, Q. J. R. Meteorol. Soc., 143, 69–100, doi:10.1002/qj.2947. Held, I. M., R. S. Hemler, and V. Ramaswamy (1993), Radiative-convective equilibrium with explicit two-dimensional moist convection, J. Atmos. Sci., 50, 3909–3927. Holloway, C., and S. Woolnough (2016), The sensitivity of convective aggregation to diabatic processes in idealized radiative-convective equilibrium simulations, J. Adv. Model. Earth Syst., 8, 166–195, doi:10.1002/2015MS000511. Holloway, C. E., and J. D. Neelin (2009), Moisture vertical structure, column water vapor, and tropical deep convection, J. Atmos. Sci., 66(6), 1665–1683. Holloway, C. E., and J. D. Neelin (2010), Temporal relations of column water vapor and tropical precipitation, J. Atmos. Sci., 67(4), 1091–1105. Hong, S. Y., Y. Noh, and J. Dudhia (2006), A new vertical diffusion package with an explicit treatment of entrainment processes, Mon. Weather Rev., 134, 2318–2341. Hu, X.-M., J. W. Nielsen-Gammon, and F. Zhang (2010), Evaluation of three planetary boundary layer schemes in the WRF model, J. Appl. Meteorol. Clim., 49(9), 1831–1844. Johnson, R. H., and X. Lin (1997), Episodic trade wind regimes over the western pacific warm pool, J. Atmos. Sci., 54(15), 2020–2034. Johnson, R. H., T. M. Rickenbach, S. A. Rutledge, P. E. Ciesielski, and W. H. Shubert (1999), Trimodal characteristics of tropical convection, J. Clim., 12, 2397–2418. Jordan, C. L. (1958), Mean soundings for the West Indies area, J. Meteorol., 15, 91–97. Khairoutdinov, M. F., S. K. Krueger, C.-H. Moeng, P. A. Bogenschutz, and D. A. Randall (2009), Large-eddy simulation of maritime deep tropical convection, J. Adv. Model. Earth Syst., 1, 15, doi:10.3894/JAMES.2009.1.15. Knievel, J. C., G. H. Bryan, and J. P. Hacker (2007), Explicit numerical diffusion in the WRF Model, Mon. Weather Rev., 135, 3808–3824. LeMone, M. A., and E. J. Zipser (1980), Cumulonimbus vertical velocity events in GATE. Part I: Diameter, intensity and mass flux, J. Atmos. Sci., 37, 2444–2457. Lin, Y. L., R. D. Farley, and H. D. Orville (1983), Bulk parameterization of the snow field in a cloud model, J. Clim. Appl. Meteorol., 22, 1065–1092. Machado, L. A., and J.-P. Chaboureau (2015), Effect of turbulence parameterization on assessment of cloud organization, Mon. Weather Review, 143(8), 3246–3262. Mapes, B. (2016), Gregarious convection and radiative feedbacks in idealized worlds, J. Adv. Model. Earth Syst., 8, 1029–1033, doi:10.1002/2016MS000651. Mapes, B. E., and P. Zuidema (1996), Radiative-dynamical consequences of dry tongues in the tropical troposphere, J. Atmos. Sci., 53, 620–638. Mauritsen, T., and B. Stevens (2015), Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models, Nat. Geosci., 8(5), 346–351. Mlawer, E. J., and S. Clough (1997), Shortwave and longwave enhancements in the Rapid Radiative Transfer Model, in Proceedings of the 7th Atmospheric Radiation Measurement (ARM) Science Team Meeting, CONF-970365, pp. 409–413, ARM, U.S. Dep. of Energy, Washington, D. C. [Available at http://www.arm.gov/publications.] Mlawer, E. J., S. J. Taubman, P. D. Brown, M. J. Iacono, and S. A. Clough (1997), Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave, J. Geophys. Res., 102, 16,663–16,682. Muller, C. J., and I. M. Held (2012), Detailed investigation of the self-aggregation of convection in cloud-resolving simulations, J. Atmos. Sci., 69(8), 2551–2565. Paluch, I. R. (1979), The entrainment mechanism in Colorado Cumuli, J. Atmos. Sci., 36, 2467–2478. Pauluis, O., and S. Garner (2006), Sensitivity of radiative-convective equilibrium simulations to horizontal resolution, J. Atmos. Sci., 63(7), 1910–1923. Pierrehumbert, R. T., and H. Yang (1993), Global chaotic mixing on isentropic surfaces, J. Atmos. Sci., 50, 2462–2480. Polvani, L. M., and A. H. Sobel (2002), The Hadley circulation and the weak temperature gradient approximation, J. Atmos. Sci., 59(10), 1744–1752. Popke, D., B. Stevens, and A. Voigt (2013), Climate and climate change in a radiative-convective equilibrium version of ECHAM6, J. Adv. Model. Earth Syst., 5, 1–14, doi:10.1029/2012MS000191. Randall, D. A., and G. J. Huffman (1980), A stochastic model of cumulus clumping, J. Atmos. Sci., 37, 2068–2078. Randall, D. A., D. A. Harshvardhan, D. A. Dazlich, and T. G. Corsetti (1989), Interactions among radiation, convection, and large-scale dynamics in a general-circulation model, J. Atmos. Sci., 46, 1943–1970. Raymond, D. J. (1995), Regulation of moist convection over the west Pacific warm pool, J. Atmos. Sci., 52, 3945–3959. Reed, K. A., B. Medeiros, J. T. Bacmeister, and P. H. Lauritzen (2015), Global radiative–convective equilibrium in the community atmosphere model, version 5, J. Atmos. Sci., 72(5), 2183–2197. Robe, F. R., and K. A. Emanuel (1996), Dependence of tropical convection on radiative forcing, J. Atmos. Sci., 53, 3265–3275. Roca, R., J. P. Lafore, C. Piriou, and J. L. Redelsperger (2005), Extratropical dry-air intrusions into the West African monsoon midtroposphere: An important factor for the convective activity over the Sahel, J. Atmos. Sci., 62, 390–407. Romps, D. M. (2010), A direct measure of entrainment, J. Atmos. Sci., 67(6), 1908–1927. Romps, D. M. (2016), The stochastic parcel model: A deterministic parameterization of stochastically entraining convection, J. Adv. Model. Earth Syst., 8, 319–344, doi:10.1002/2015MS000537. Romps, D. M., and Z. Kuang (2010), Do undiluted convective plumes exist in the upper tropical troposphere?, J. Atmos. Sci., 67(2), 468–484. Ross, A. N., A. M. Tompkins, and D. J. Parker (2004), The role of cold pools in triggering convection—A simple model, J. Atmos. Sci., 61, 1582–1595. Rotunno, R., and K. A. Emanuel (1987), An air-sea interaction theory for tropical cyclones: Part II, J. Atmos. Sci., 44, 542–561. Seifert, A., and T. Heus (2013), Large-eddy simulation of organized precipitating trade wind cumulus clouds, Atmos. Chem. Phys., 13, 5631–5645. Sessions, S. L., S. Sentic, and M. J. Herman (2016), The role of radiation in organizing convection in weak temperature gradient simulations, J. Adv. Model. Earth Syst., 8, 244–271, doi:10.1002/2015MS000587. Sherwood, S. C. (1999), Convective precursors and predictability in the tropical western Pacific, Mon. Weather Rev., 127, 2977–2991. Sherwood, S. C., R. Roca, T. M. Weckwerth, and N. G. Andronova (2010), Tropospheric water vapor, convection, and climate, Rev. Geophys., 48, G2001, doi:10.1029/2009RG000301. Sherwood, S. C., D. Hernández-Deckers, M. Colin, and F. Robinson (2013), Slippery thermals and the cumulus entrainment paradox, J. Atmos. Sci., 70(8), 2426–2442. Skamarock, W. C., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, M. G. Duda, X.-Y. Huang, W. Wang, and J. G. Powers (2008), A description of the advanced research WRF Version 3, Tech. Rep. NCAR/TN-475+STR, Natl. Cent. Atmos. Res., Boulder, Colo. [Available at http://www2.mmm.ucar.edu/wrf/users/docs/arw_v3.pdf.] Slingo, A., and J. M. Slingo (1988), The response of a general-circulation model to cloud longwave radiative forcing: 1: Introduction and initial experiments, Q. J. R. Meteorol. Soc., 114, 1027–1062. Smagorinsky, J. (1963), General circulation experiments with the primative equations: I: The basic experiment, Mon. Weather Rev., 91, 99–164. Sobel, A. H., J. Nilsson, and L. M. Polvani (2001), The weak temperature gradient approximation and balanced tropical moisture waves, J. Atmos. Sci., 58(23), 3650–3665. Stephens, G. L., S. Van Den Heever, and L. Pakula (2008), Radiative-convective feedbacks in idealized states of radiative-convective equilibrium, J. Atmos. Sci., 65(12), 3899–3916. Stoyan, D., W. S. Kendalla, and J. Mecke (1987), Stochastic Geometry and Its Applications, 345 pp., John Wiley, New York. Stull, R. B. (1988), An Introduction to Boundary Layer Meteorology, 666 pp., Kluwer Acad., Dordrecht, Netherlands. Sullivan, P. P., and E. G. Patton (2011), The effect of mesh resolution on convective boundary layer statistics and structures generated by large-eddy simulation, J. Atmos. Sci., 68(10), 2395–2415. Takemi, T., and R. Rotunno (2003), The effects of subgrid model mixing and numerical filtering in simulations of mesoscale cloud systems, Mon. Weather Rev., 131, 2085–2101. Tiedtke, M. (1989), A comprehensive mass flux scheme for cumulus parameterization in large-scale models, Mon. Weather Rev., 117, 1779–1800. Tobin, I., S. Bony, and R. Roca (2012), Observational evidence for relationships between the degree of aggregation of deep convection, water vapor, surface fluxes, and radiation, J. Clim., 25(20), 6885–6904. Tompkins, A. M. (2000), The impact of dimensionality on long-term cloud resolving model simulations, Mon. Weather Rev., 128, 1521–1535. Tompkins, A. M. (2001a), Organization of tropical convection in low vertical wind shears: The role of water vapor, J. Atmos. Sci., 58, 529–545. Tompkins, A. M. (2001b), On the relationship between tropical convection and sea surface temperature, J. Clim., 14, 633–637. Tompkins, A. M. (2001c), Organization of tropical convection in low vertical wind shears: The role of coldpools, J. Atmos. Sci., 58, 1650–1672. Tompkins, A. M., and G. C. Craig (1998a), Radiative-convective equilibrium in a three-dimensional cloud ensemble model, Q. J. R. Meteorol. Soc., 124, 2073–2097. Tompkins, A. M., and G. C. Craig (1998b), Time-scales of adjustment to radiative-convective equilibrium in the tropical atmosphere, Q. J. R. Meteorol. Soc., 124, 2693–2713. Tompkins, A. M., and K. A. Emanuel (2000), The vertical resolution sensitivity of simulated equilibrium temperature and water vapour profiles, Q. J. R. Meteorol. Soc., 126, 1219–1238. Trenberth, K. E., Z. Yongxin, F. T. John, and T. Shoichi (2015), Climate variability and relationships between top of atmosphere radiation and temperatures on earth, J. Geophys. Res., 120, 3642–3659, doi:10.1002/2014JD022887. Warner, J. (1955), The water content of cumuliform cloud, Tellus, 7, 449–457. Warner, J., and T. D. Newnham (1952), new method of measurement of cloud water content, Q. J. R. Meteorol. Soc., 78, 46–52. Waugh, D. W., and L. M. Polvani (2000), Climatology of intrusions into the tropical upper troposphere, Geophys. Res. Lett., 27, 3857–3860. Weger, R. C., J. Lee, T. Zhu, and R. M. Welch (1992), Clustering, randomness and regularity in cloud fields: 1: Theoretical considerations, J. Geophys. Res., 97, 20,519–20,536. Wing, A. A., and T. W. Cronin (2016), Self-aggregation of convection in long channel geometry, Q. J. R. Meteorol. Soc., 142(694), 1–15, doi:10.1002/qj.2628. Wing, A. A., and K. A. Emanuel (2013), Physical mechanisms controlling self aggregation of convection in idealized numerical modeling simulations, J. Adv. Model. Earth Syst., 6, 59–74, doi:10.1002/2013MS000269. Wyngaard, J. C. (2004), Toward numerical modeling in the terra incognita, J. Atmos. Sci., 61(14), 1816–1826. Xue, M. (1999), High-order monotonic numerical diffusion and smoothing, Mon. Weather Rev., 128, 2853–2864. Yang, H., and R. T. Pierrehumbert (1994), Production of dry air by isentropic mixing, J. Atmos. Sci., 51, 3437–3454. Yeo, K., and D. M. Romps (2013), Measurement of convective entrainment using Lagrangian particles, J. Atmos. Sci., 70(1), 266–277. Zhang, C. (2005), Madden-Julian oscillation, Rev. Geophys., 43, G2003, doi:10.1029/2004RG000158. Zhang, C., B. E. Mapes, and B. J. Soden (2003), Bimodality in tropical water vapour, Q. J. R. Meteorol. Soc., 129(594), 2847–2866.