The Technical Note series provides an outlet for a variety of NCAR manuscripts that contribute in specialized ways to the body of scientific knowledge but which are not suitable for journal, monograph, or book publication. Reports in this series are issued by the NCAR Scientific Divisions ; copies may be obtained on request from the Publications Office of NCAR. Designation symbols for the series include: Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation.

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A Description of the Advanced Research WRF Version 3

This paper proposes a revised vertical diffusion package with a nonlocal turbulent mixing coefficient in the planetary boundary layer (PBL). Based on the study of Noh et al. and accumulated results of the behavior of the Hong and Pan algorithm, a revised vertical diffusion algorithm that is suitable for weather forecasting and climate prediction models is developed. The major ingredient of the revision is the inclusion of an explicit treatment of entrainment processes at the top of the PBL. The new diffusion package is called the Yonsei University PBL (YSU PBL). In a one-dimensional offline test framework, the revised scheme is found to improve several features compared with the Hong and Pan implementation. The YSU PBL increases boundary layer mixing in the thermally induced free convection regime and decreases it in the mechanically induced forced convection regime, which alleviates the well-known problems in the Medium-Range Forecast (MRF) PBL. Excessive mixing in the mixed layer in the presenc...

/pdf/a-new-vertical-diffusion-package-with-an-explicit-treatment-11t7nq83se.pdf

A New Vertical Diffusion Package with an Explicit Treatment of Entrainment Processes

This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted here is that the land surface model should be able to provide not only reasonable diurnal variations of surface heat fluxes as surface boundary conditions for coupled models, but also correct seasonal evolutions of soil moisture in the context of a long-term data assimilation system. In a similar way to that in which the modified Oregon State University land surface model (LSM) has been used in the NCEP global and regional forecast models, it is implemented in MM5 to facilitate the initialization of soil moisture. Also, 1-km resolution vegetation and soil texture maps are introduced in the coupled MM5–LSM system to help identify vegetation/water/soil characteristics at fine scales and capture the feedback of these land surface forcings. A monthly varying climatological 0.15° × 0.15° green ...

https://www.sjsu.edu/people/frank.freedman/courses/metr130/s1/Paper-Chen-and-Dudhia---MWR.pdf

Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

/pdf/climate-change-2007-the-physical-science-basis-1x93ttz9jt.pdf

Climate Change 2007: The Physical Science Basis.

Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model [presentation]

Comments on “Decomposing the Atmospheric Flow Using Potential Vorticity Framework”

A transient feature marked primarily by a sudden increase in wind speed and brief period of heavy snow was observed over northeastern Colorado on 11-12 March 1993. Little, if any, abrupt changes in surface pressure or temperature were noted, such as might accompany a gravity current. Gradual temperature falls and pressure rises were observed behind the velocity surge; however, there was no cyclonic wind shift nor did the feature last for more than a few hours, suggesting that it was not likely a classical front. Data indicate that the surge originated near the peak of the Cheyenne Ridge, a 400-m, east-west elongated hill near the border between Colorado and Wyoming. Simulations using an idealized, two-dimensional isentropic model show that a transient resembling observed surge results from impulsively started flow over heated terrain. Heating creates convergence that is in phase with the velocity surge at the leading edge of the topographic wave. The result is a coherent disturbance in velocity, which moves downstream at nearly the mean flow speed. Simulations with The Pennsylvania State University-National Center for Atmospheric Research nonhydrostatic model (MM5) using a horizontal resolution of 6.7 km capture the evolution of the observed surge. These simulations support the identification of the surge as a topographic wave modified by heating, but they also indicate an important role played by latent heating in the updraft at the leading edge of the surge. Because the latent heating occurs mainly downstream from the Cheyenne Ridge, the formation of the topographic wave is unaltered by it, however, the updraft at the leading edge of the surge it greatly intensified, leading to a narrow, propagating band of heavy snow

Observations and Modeling of a Mesoscale Cold Surge during WISPIT

Spatial and temporal object-based evaluation of numerical precipitation forecasts

Bow Echo and Mesoscale Vortex (MCV) Experiment is a study of life cycles of convective systems using three multiple, mobile ground-based s. It represents a combination of d programs to investigate (a) es (Fujita, 1978), principally ch produce damaging surface last at least 4 hours and (b) vective systems which produce mesoscale convective vortices artels and Maddox, 1991). The s conducted from 20 May to 6 , based at MidAmerica Airport utah, Illinois. A detailed of the project, including y results appears in Davis et al. he reader wishing to view BAMEX data should visit .joss.ucar.edu/bamex/catalog/. ment what is already published AMEX, we will herein discuss liminary, perhaps speculative, from the project. Broadly these fall into two categories: esults and lessons learned about ment of facilities or about the re of the project.

Christopher A. Davis

Papers

Comments on “Decomposing the Atmospheric Flow Using Potential Vorticity Framework”

Observations and Modeling of a Mesoscale Cold Surge during WISPIT

Spatial and temporal object-based evaluation of numerical precipitation forecasts

An Overview of the Bow Echo and MCV Experiment (BAMEX)

A Modeling Study on the Impacts of Typhoon Morakot's (2009) Vortex Structure on Rainfall in Taiwan Using Piecewise Potential Vorticity Inversion