scholarly journals Sensitivity of a Mesoscale Model to Microphysical Parameterizations in the MAP SOP Events IOP2b and IOP8

2007 ◽  
Vol 46 (9) ◽  
pp. 1438-1454 ◽  
Author(s):  
Stefano Serafin ◽  
Rossella Ferretti
Keyword(s):  
Mesoscale Model ◽  
Deposition Velocity ◽  
Rain Gauge ◽  
Forecast Skill ◽  
Windward Side ◽  
State University ◽  
Radar Observations ◽  
Microphysical Processes ◽  
The One ◽  
The Impact

Abstract The sensitivity of a mesoscale model to different microphysical parameterizations is investigated for two events of precipitation in the Mediterranean region, that is, the Mesoscale Alpine Program (MAP) intensive observation periods (IOP) 2b (19–21 September 1999) and 8 (20–22 October 1999). Simulations are performed with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5); the most commonly used bulk microphysical parameterization schemes are evaluated, with a particular focus on their impact on the forecast of rainfall. To evaluate the forecast skill, the verification is carried out quantitatively by using the observations recorded by a high-resolution rain gauge network during the MAP campaign. The results show that, for the surface rainfall forecast, all microphysical schemes produce a similar precipitation field and none of them perform significantly better than the others. The ability of different schemes to reproduce events with different ongoing microphysical processes is briefly discussed by comparing model simulations and knowledge of hydrometeor fields from radar observations. The vertical profiles of hydrometeors from two of the analyzed schemes show gross similarities with available radar observations. Last, the role of one of the parameterizations appearing in a typical bulk microphysical scheme, that is, the one of the snowfall speed, is evaluated in detail. Adjustments in the semiempirical relationships describing the fall speed of snow particles have a large impact, because a reduced snowfall speed enhances precipitation on the lee side of mountain ridges and diminishes it on the windward side. Anyway, this effect does not appear to be able to largely improve or reduce the forecast skill of the MM5 systematically; the impact of changes in the parameterization of the snow deposition velocity very likely depends on the dynamics of the event under investigation.

scholarly journals Small-Scale Spatial Gradients in Climatological Precipitation on the Olympic Peninsula

2007 ◽  
Vol 8 (5) ◽  
pp. 1068-1081 ◽  
Author(s):  
Alison M. Anders ◽  
Gerard H. Roe ◽  
Dale R. Durran ◽  
Justin R. Minder
Keyword(s):  
Simple Model ◽  
Mesoscale Model ◽  
Windward Side ◽  
Small Scale ◽  
Precipitation Pattern ◽  
State University ◽  
Spatial Gradients ◽  
The Individual ◽  
High Topography ◽  
The Impact

Abstract Persistent, 10-km-scale gradients in climatological precipitation tied to topography are documented with a finescale rain and snow gauge network in the Matheny Ridge area of the Olympic Mountains of Washington State. Precipitation totals are 50% higher on top of an ∼800-m-high ridge relative to valleys on either side, 10 km distant. Operational fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) runs on a 4-km grid produce similar precipitation patterns with enhanced precipitation over high topography for 6 water years. The performance of the MM5 is compared to the gauge data for 3 wet seasons and for 10 large precipitation events. The cumulative MM5 precipitation forecasts for all seasons and for the sum of all 10 large events compare well with the precipitation measured by the gauges, although some of the individual events are significantly over- or underforecast. This suggests that the MM5 is reproducing the precipitation climatology in the vicinity of the gauges, but that errors for individual events may arise due to inaccurate specification of the incident flow. A computationally simple model of orographic precipitation is shown to reproduce the major features of the event precipitation pattern on the windward side of the range. This simple model can be coupled to landscape evolution models to examine the impact of long-term spatial variability in precipitation on the evolution of topography over thousands to millions of years.

scholarly journals Impact of Four-Dimensional Variational Data Assimilation of Atmospheric Motion Vectors on Tropical Cyclone Track Forecasts

2006 ◽  
Vol 21 (4) ◽  
pp. 663-669 ◽  
Author(s):  
Dongliang Wang ◽  
Xudong Liang ◽  
Yihong Duan ◽  
Johnny C. L. Chan
Keyword(s):  
Tropical Cyclone ◽  
Data Assimilation ◽  
Mesoscale Model ◽  
State University ◽  
Motion Vectors ◽  
Geostationary Meteorological Satellite ◽  
Atmospheric Motion ◽  
Atmospheric Motion Vectors ◽  
Data Assimilation Technique ◽  
The Impact

Abstract The fifth-generation Pennsylvania State University–National Center for Atmospheric Research nonhydrostatic Mesoscale Model is employed to evaluate the impact of the Geostationary Meteorological Satellite-5 water vapor and infrared atmospheric motion vectors (AMVs), incorporated with the four-dimensional variational (4DVAR) data assimilation technique, on tropical cyclone (TC) track predictions. Twenty-two cases from eight different TCs over the western North Pacific in 2002 have been examined. The 4DVAR assimilation of these satellite-derived wind observations leads to appreciable improvements in the track forecasts, with average reductions in track error of ∼5% at 12 h, 12% at 24 h, 10% at 36 h, and 7% at 48 h. Preliminary results suggest that the improvement depends on the quantity of the AMV data available for assimilation.

scholarly journals The Same-Source Parallel MM5

2000 ◽  
Vol 8 (1) ◽  
pp. 5-12 ◽  
Author(s):  
John Michalakes
Keyword(s):  
Shared Memory ◽  
Distributed Memory ◽  
Mesoscale Model ◽  
State University ◽  
Parallel Performance ◽  
Hybrid Parallelization ◽  
Beowulf Clusters ◽  
Penn State ◽  
Library Support ◽  
The Impact

Beginning with the March 1998 release of the Penn State University/NCAR Mesoscale Model (MM5), and continuing through eight subsequent releases up to the present, the official version has run on distributed -memory (DM) parallel computers. Source translation and runtime library support minimize the impact of parallelization on the original model source code, with the result that the majority of code is line-for-line identical with the original version. Parallel performance and scaling are equivalent to earlier, hand-parallelized versions; the modifications have no effect when the code is compiled and run without the DM option. Supported computers include the IBM SP, Cray T3E, Fujitsu VPP, Compaq Alpha clusters, and clusters of PCs (so-called Beowulf clusters). The approach also is compatible with shared-memory parallel directives, allowing distributed-memory/shared-memory hybrid parallelization on distributed-memory clusters of symmetric multiprocessors.

scholarly journals Influences of Asymmetric Heating on Hurricane Evolution in the MM5

2005 ◽  
Vol 62 (11) ◽  
pp. 3974-3992 ◽  
Author(s):  
J. Dominique Möller ◽  
Lloyd J. Shapiro
Keyword(s):  
Diabatic Heating ◽  
Mesoscale Model ◽  
State University ◽  
Short Term ◽  
Term Change ◽  
Passive Response ◽  
Tangential Wind ◽  
Small Change ◽  
The Impact

Abstract While previous idealized studies have demonstrated the importance of asymmetric atmospheric features in the intensification of a symmetric tropical cyclone vortex, the role of convectively generated asymmetries in creating changes in the azimuthally averaged cyclone is not well understood. In the present study the full-physics nonhydrostatic fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) is used to evaluate the influence of such asymmetries. Rather than adding winds and temperatures in balance with a specified potential vorticity (PV) asymmetry, or temperature perturbations themselves, to a symmetric vortex as in previous studies, a diabatic heating asymmetry is imposed on a spunup model hurricane. The impact of short-duration eyewall-scale monochromatic azimuthal wavenumber diabatic heating on the short- and long-term evolution of the azimuthally averaged vortex is evaluated, and a tangential wind budget is made to determine the mechanisms responsible for the short-term impact. It is found that the small eddy kick created by the additional diabatic heating asymmetry leads to a substantially amplified long-term change in the azimuthally averaged vortex, with episodes of strong relative weakening and strengthening following at irregular intervals. This behavior is diabatically controlled. It is also found that the symmetric secondary circulation can be active in creating short-term changes in the vortex, and is not simply a passive response as in previous studies with dry physics. A central conclusion of the study is that the structure of the spunup hurricane vortex, in particular preexisting asymmetric features, can have a substantial influence on the character of the response to an additional diabatic heating asymmetry. The results also imply that a small change in the factors that control convective activity will have a substantial lasting consequence for the intensification of a hurricane.

scholarly journals Toward a climate downscaling for the Eastern Mediterranean at high-resolution

2008 ◽  
Vol 12 ◽  
pp. 159-164 ◽  
Author(s):  
A. N. Hahmann ◽  
D. Rostkier-Edelstein ◽  
T. T. Warner ◽  
Y. Liu ◽  
F. Vandenberghe ◽  
...  
Keyword(s):  
Mesoscale Model ◽  
Eastern Mediterranean ◽  
Precipitation Amount ◽  
Rain Gauge ◽  
State University ◽  
Model Simulations ◽  
Test Region ◽  
Lateral Boundary Conditions ◽  
Monthly Total Precipitation ◽  
Monthly Total

Abstract. As a first step toward downscaling global model simulations of future climates for the eastern Mediterranean Sea and surrounding land area, mesoscale-model simulations with the Pennsylvania State University – National Center for Atmospheric Research (NCAR) mesoscale model, version 5 (MM5) are verified in the context of precipitation amount. The simulations are driven with January NCAR-NCEP reanalysis project (NNRP) lateral-boundary conditions and assimilate surface and upper air observations. The results of the simulations compare reasonably well with rain gauge and satellite estimates of monthly total precipitation, and the model reproduces the overall trends in inter-annual precipitation variability for one test region. Cyclones during the period were tracked, and their properties identified.

scholarly journals Four-Dimensional Variational Data Analysis of Water Vapor Raman Lidar Data and Their Impact on Mesoscale Forecasts

2008 ◽  
Vol 25 (8) ◽  
pp. 1437-1453 ◽  
Author(s):  
Matthias Grzeschik ◽  
Hans-Stefan Bauer ◽  
Volker Wulfmeyer ◽  
Dirk Engelbart ◽  
Ulla Wandinger ◽  
...  
Keyword(s):  
Water Vapor ◽  
Data Analysis ◽  
Vertical Structure ◽  
Mesoscale Model ◽  
Test Case ◽  
State University ◽  
Raman Lidar ◽  
Initial Water ◽  
Forecast Time ◽  
The Impact

Abstract The impact of water vapor observations on mesoscale initial fields provided by a triangle of Raman lidar systems covering an area of about 200 km × 200 km is investigated. A test case during the Lindenberg Campaign for Assessment of Humidity and Cloud Profiling Systems and its Impact on High-Resolution Modeling (LAUNCH-2005) was chosen. Evaluation of initial water vapor fields derived from ECMWF analysis revealed that in the model the highly variable vertical structure of water vapor profiles was not recovered and vertical gradients were smoothed out. Using a 3-h data assimilation window and a resolution of 10–30 min, continuous water vapor data from these observations were assimilated in the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) by means of a four-dimensional variational data analysis (4DVAR). A strong correction of the vertical structure and the absolute values of the initial water vapor field of the order of 1 g kg−1 was found. This occurred mainly upstream of the lidar systems within an area, which was comparable with the domain covered by the lidar systems. The correction of the water vapor field was validated using independent global positioning system (GPS) sensors. Much better agreement to GPS zenith wet delay was achieved with the initial water vapor field after 4DVAR. The impact region was transported with the mean wind and was still visible after 4 h of free forecast time.

The Impact of Assimilating Dropwindsonde Data Deployed at Different Sites on Typhoon Track Forecasts

2013 ◽  
Vol 141 (8) ◽  
pp. 2669-2682 ◽  
Author(s):  
Boyu Chen ◽  
Mu Mu ◽  
Qin Xiaohao
Keyword(s):  
Mesoscale Model ◽  
Three Dimensional ◽  
Weather Research And Forecasting ◽  
Surveillance Program ◽  
State University ◽  
Optimal Perturbation ◽  
Fifth Generation ◽  
Typhoon Track ◽  
Adaptive Observation ◽  
The Impact

Abstract This study investigates the impacts on typhoon track forecasting by the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) and its three-dimensional variational data assimilation (3DVAR) system of assimilating dropwindsonde observational data acquired from different sites. All of the sonde data were obtained between 2004 and 2009 in the typhoon surveillance program Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR). Experiments were conducted to test the model's response to five scenarios involving differing dropwindsonde data inputs: 1) no dropwindsonde data, 2) all available dropwindsonde data, 3) data gathered in sensitive regions identified by the conditional nonlinear optimal perturbation (CNOP) approach, 4) data gathered in sensitive regions identified by the first singular vector (FSV) approach, and 5) several sondes selected at random. The results show that using dropwindsonde data based on CNOP sensitivity can lead to improvements in typhoon track forecasting similar to, and occasionally better than, those achieved by assimilating all of the available data. Both approaches offered greater benefits than the other three alternatives averagely. It is proposed that CNOP provides a suitable approach to determining sensitive regions during adaptive observation of typhoons. Similar results may be obtained if the sensitivity products developed using MM5 are employed in the Weather Research and Forecasting Model (WRF), suggesting that it is applicable to utilize sensitivity produced by MM5 in WRF.

Two-Dimensional Idealized Simulations of the Impact of Multiple Windward Ridges on Orographic Precipitation

2008 ◽  
Vol 65 (2) ◽  
pp. 509-523 ◽  
Author(s):  
Brian A. Colle
Keyword(s):  
Mesoscale Model ◽  
Two Dimensional ◽  
State University ◽  
Mountain Waves ◽  
Freezing Level ◽  
Fifth Generation ◽  
Warm Rain ◽  
Windward Slope ◽  
The Impact ◽  
Precipitation Enhancement

Abstract This paper presents two-dimensional (2D) idealized simulations at 1-km grid spacing using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) in order to illustrate how a series of ridges along a broad windward slope can impact the precipitation distribution and simulated microphysics. The number of windward ridges for a 2000-m mountain of 50-km half-width is varied from 0 to 16 over a 150-km distance using different stratifications, freezing levels, uniform ambient flows, and ridge amplitudes. A few (200–400 m) windward ridges can enhance the precipitation locally over each ridge crest by a factor of 2–3. Meanwhile, a series of 8–16 ridges that are 200–400 m in height can increase the net precipitation averaged over the windward slope by 10%–35%. This average precipitation enhancement is maximized when the ridge spacing is relatively small (<20 km), since there is less time for subsidence drying within the valleys and the mountain waves become more evanescent, which favors a simple upward and downward motion couplet over each ridge. In addition, small ridge spacing is shown to have a synergistic effect on precipitation over the lower windward slope, in which an upstream ridge helps increase the precipitation over the adjacent downwind ridge. There is little net precipitation enhancement by the ridges for small moist Froude numbers (Fr < 0.8), since flow blocking limits the flow up and over each ridge. For a series of narrow ridges (∼10 km wide), the largest precipitation enhancement for a 500-mb freezing level occurs over lower windward slope of the barrier through warm-rain processes. In contrast, a 1000-mb freezing level has the largest precipitation enhancement over the middle and upper portions of a barrier for a series of narrow (∼10 km wide) ridges given the horizontal advection of snow aloft.

scholarly journals Digital Filter Initialization for MM5

2006 ◽  
Vol 134 (4) ◽  
pp. 1222-1236 ◽  
Author(s):  
Min Chen ◽  
Xiang-Yu Huang
Keyword(s):  
Digital Filter ◽  
Mesoscale Model ◽  
Heavy Rain ◽  
State University ◽  
Initial Model ◽  
Pennsylvania State University ◽  
Fifth Generation ◽  
Beijing Institute ◽  
The Impact

Abstract In this paper several configurations of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5), which is implemented at Beijing Institute of Urban Meteorology in China, are used to demonstrate the initial noise problem caused either by interpolating global model fields onto an MM5 grid or by using MM5 objective analysis schemes. An implementation of a digital filter initialization (DFI) package to MM5 is then documented. A heavy rain case study and intermittent data assimilation experiments are used to assess the impact of DFI on MM5 forecasts. It is shown that DFI effectively filters out the noise and produces a balanced initial model state. It is also shown that DFI improves the spinup aspects for precipitation, leading to better scores for short-range precipitation forecasts. The issues related to the initialization of variables that are not observed and/or analyzed, in particular those for nonhydrostatic quantities, are discussed.

The Impact of Trade Wind Strength on Precipitation over the Windward Side of the Island of Hawaii

2008 ◽  
Vol 136 (3) ◽  
pp. 913-928 ◽  
Author(s):  
Mary Ann Esteban ◽  
Yi-Leng Chen
Keyword(s):  
Daily Rainfall ◽  
Early Morning ◽  
Rain Gauge ◽  
Windward Side ◽  
Trade Wind ◽  
Climatic Data ◽  
Maximum Rainfall ◽  
Late Afternoon ◽  
National Climatic Data Center ◽  
The Impact

Abstract The effects of trade wind strength and the diurnal heating cycle on the production of summer trade wind rainfall on the windward side of the island of Hawaii are examined from the data collected from the Hawaiian Rainband Project (HaRP) during 11 July–24 August 1990 and from National Weather Service Hydronet and National Climatic Data Center rain gauge data during 11 July–24 August for the years 1997–2000. For strong trades, the daily rainfall totals on the windward lowlands west of Hilo are higher with a nocturnal maximum there due to the convergence of the katabatic flow and the incoming decelerating trade wind flow, and orographic lifting aloft. The maximum rainfall axis shifts farther inland when trades are stronger. Except in the late afternoon hours, rainfall amounts on the windward side are higher when trades are stronger. For weak trades (≤5 m s−1), the rainfall distributions have a pronounced late afternoon maximum on the windward slopes due to the development of anabatic winds. The nocturnal rainfall over the windward lowlands and the early morning coastal rainfall are lower when trades are weaker.

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