Search Results

You are looking at 1 - 10 of 58 items for :

  • Diabatic heating x
  • Bulletin of the American Meteorological Society x
  • All content x
Clear All
Sourabh S. Diwan, P. Prasanth, K. R. Sreenivas, S. M. Deshpande, and Roddam Narasimha

. The flow generated in the apparatus may be appropriately called a “transient diabatic plume” (TDP) to emphasize the use of off-source heating in a cloud-type transient plume flow. Fig. 1. The cloud-flow simulator. LLS: lower-level stratification, ULS: upper-level stratification, RTD: resistance temperature detector, HIZ: heat injection zone, T : temperature, z : height, g : acceleration due to gravity, FF: false floor. Subscripts: c : plume chamber, ls : lower stratification, us : upper

Full access
Gary M. Lackmann

hurricane symbol indicates the location of Sandy. F ig . 2. Sea level pressure (yellow contours; 4-hPa interval) from 54-km control run, with 300-hPa wind speed difference (vector arrows) between a full-physics model simulation and a simulation in which the effects of condensational heating were withheld, valid at 0000 UTC 30 Oct 2012. This time corresponds to hour 96 of the model simulations, which were initialized at 0000 UTC 26 Oct. The center of the upper-level anticyclonic perturbation flow is

Full access
W.-K. Tao, E. A. Smith, R. F. Adler, Z. S. Haddad, A. Y. Hou, T. Iguchi, R. Kakar, T. N. Krishnamurti, C. D. Kummerow, S. Lang, R. Meneghini, K. Nakamura, T. Nakazawa, K. Okamoto, W. S. Olson, S. Satoh, S. Shige, J. Simpson, Y. Takayabu, G. J. Tripoli, and S. Yang

Rainfall is a fundamental process within the Earth's hydrological cycle because it represents a principal forcing term in surface water budgets, while its energetics corollary, latent heating, is the principal source of atmospheric diabatic heating well into the middle latitudes. Latent heat production itself is a consequence of phase changes between the vapor, liquid, and frozen states of water. The properties of the vertical distribution of latent heat release modulate large-scale meridional and zonal circulations within the Tropics, as well as modify the energetic efficiencies of midlatitude weather systems.

This paper highlights the retrieval of latent heating from satellite measurements generated by the Tropical Rainfall Measuring Mission (TRMM) satellite observatory, which was launched in November 1997 as a joint American–Japanese space endeavor. Since then, TRMM measurements have been providing credible four-dimensional accounts of rainfall over the global Tropics and subtropics, information that can be used to estimate the space–time structure of latent heating across the Earth's low latitudes.

A set of algorithm methodologies for estimating latent heating based on precipitation-rate profile retrievals obtained from TRMM measurements has been under continuous development since the advent of the mission s research program. These algorithms are briefly described, followed by a discussion of the latent heating products that they generate. The paper then provides an overview of how TRMM-derived latent heating information is currently being used in conjunction with global weather and climate models, concluding with remarks intended to stimulate further research on latent heating retrieval from satellites.

Full access
K. S. Gage, C. R. Williams, and W. L. Ecklund

Uncertainty in the magnitude and distribution of diabatic heating associated with precipitating cloud systems is one of the major factors giving rise to uncertainty in the simulation of large-scale atmospheric circulations in numerical models of the atmosphere. A major international effort is under way to develop an improved parameterization of the hydrological cycle within numerical models. Progress will require better observations of the distribution of the diabatic heating associated with cloud systems in the Tropics. In this paper new observations are presented demonstrating the potential of UHF profilers for diagnosing the vertical structure of convective systems in the Tropics. These preliminary results indicate that while mesoscale convective systems are prevalent in the Tropics there are important contributions to rainfall from smaller-scale warm rain systems that do not extend above the freezing level. They also show that extensive regions of upper-tropospheric precipitating clouds often exist at times when no rain is detected at the surface. These observations provide important information that should prove useful in developing improved methods for estimating precipitation from satellite observations.

Full access
Christopher S. Bretherton, Taneil Uttal, Christopher W. Fairall, Sandra E. Yuter, Robert A. Weller, Darrel Baumgardner, Kimberly Comstock, Robert Wood, and Graciela B. Raga

Overlaying the cool southeast Pacific Ocean is the most persistent subtropical stratocumulus cloud deck in the world. It produces a profound affect on tropical climate by shading the underlying ocean and radiatively cooling and stirring up turbulence in the atmosphere. In October 2001, the East Pacific Investigation of Climate undertook an exploratory cruise from the Galapagos Islands to Chile. The cruise gathered an unprecedented dataset, integrating radiosonde, surface, cloud remote sensing, aerosol, and ocean measurements. Scientific objectives included measuring the vertical structure of the ABL in this region, understanding what physical processes are determining the stratocumulus cloud albedo, and understanding the fluxes of heat and water that couple the atmosphere and ocean in this region.

An unexpectedly well-mixed stratocumulus-capped boundary layer as a result of a strong inversion was encountered throughout. A strong diurnal cycle was observed, with thicker clouds and substantial drizzle (mainly evaporating above the sea surface) during the late night and early morning. This was driven in part by local diabatic processes, and was reinforced by a surprisingly pronounced diurnal cycle of vertical motion. The vertical motion appears to be an inertia-gravity wave driven by daytime heating over South America that propagates over 1000 km offshore. Much more nocturnal drizzle and pronounced mesoscale cellularity were observed in “clean” conditions when cloud droplet concentrations and aerosol concentrations were low. Entrainment of dry, warm air is inferred to be the primary regulator of cloud thickness in this region, but drizzle also appears to have a large indirect impact by inhibiting and changing the spatial organization of turbulence.

Full access
Andrew D. Elvidge and Ian A. Renfrew

θ − θ e , with convergence indicating latent heat gain (from condensation or freezing) and divergence indicating latent heat loss (from evaporation or melting). Changes in air parcel θ e reflect the remaining diabatic contributions from mechanical mixing leading to sensible heating Δ SH T and radiative heating Δ RH T . These two mechanisms can be isolated by computing Δ RH T along the foehn trajectories using numerical model output. Note that Δ RH T is not shown as—together with

Open access
Jian Ling, Chongyin Li, Tim Li, Xiaolong Jia, Boualem Khouider, Eric Maloney, Frederic Vitart, Ziniu Xiao, and Chidong Zhang

“quasi-equilibrium” state; and realistic vertical profiles in temperature, humidity, and diabatic heating. Different models disagree on the role of ocean coupling, surface flux feedbacks, and large-scale radiative–convective feedbacks to the MJO. While tuning model parameterizations can lead to improved MJO simulations, it is often at the expense of a deterioration elsewhere, including the mean state. The MJO is a major source of predictability on subseasonal time scales (3–6 weeks). The

Full access
Kenneth P. Bowman, John C. Lin, Andreas Stohl, Roland Draxler, Paul Konopka, Arlyn Andrews, and Dominik Brunner

extrapolation produces fictitious values. Unrealistic trajectories can be generated anywhere that the 1,000-hPa surface intersects the ground. Isentropic coordinate trajectory models have advantages for trajectory studies of the upper troposphere and stratosphere, where vertical velocities in θ coordinates (diabatic heating rates) are usually small ( Ploeger et al. 2010 , 2011 ). Isentropic coordinates are rarely used for trajectory studies in the lower atmosphere because of conceptual and technical

Full access
Mitchell W. Moncrieff, Duane E. Waliser, and James Caughey

-scale convective organization. However, a challenge is finding clear observational support and improved prediction of these features. Distinguishing whether the organization is upscale or downscale is difficult to directly observe. In mature MJOs, important aspects include the vertical tilting associated with the first and second baroclinic vertical modes of diabatic heating, which is relatively well discerned from observations, and the third mode associated with organized convective momentum transport (CMT

Full access
David D. Turner, P. Jonathan Gero, and David C. Tobin

infrared could affect vertical motions through the diabatic heating rate. With growing interest and improvements in remote sensing in the far infrared, a focused two-day workshop was convened to review the importance of the far-infrared portion of the electromagnetic spectrum, assess the state of the science in measuring and modeling radiation in this spectral band, and recommend future directions in its development. The workshop, which was attended by leading scientists in the fields of infrared

Full access