The Role of Convective Parameterization in the Simulation of a Gulf Coast Precipitation System

Kalb, Michael

doi:10.1175/1520-0493(1987)115<0214:trocpi>2.0.co;2

Cited by 9 publications

(4 citation statements)

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“…It adjusts the model's thermal and moisture structures toward reference profiles that reflect the quasi-equilibrium state established by deep convection (Betts 1986). Deep convection is generally parameterized and not explicitly predicted when the horizontal grid spacing is greater than about 10 km (e.g., Molinari and Dudek 1986;Kalb 1987;Zhang et al 1988; Gallus and Segal 2000;Bélair and Mailhot 2001;Liu et al 2001;Roberts and Rutledge 2003), but convective parameterization (CP) is typically avoided at higher resolution. This avoidance is appropriate because the conceptual basis for CP becomes increasingly ambiguous as the grid spacing decreases further (e.g., Kain et al 2008;Molinari and Dudek 1992;Arakawa 2004).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of NU-WRF Rainfall Forecasts for IFloodS

Peters‐Lidard

Tao

et al. 2016

Journal of Hydrometeorology

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The Iowa Flood Studies (IFloodS) campaign was conducted in eastern Iowa as a pre-GPM-launch campaign from 1 May to 15 June 2013. During the campaign period, real-time forecasts were conducted utilizing the NASA-Unified Weather Research and Forecasting (NU-WRF) Model to support the daily weather briefing. In this study, two sets of the NU-WRF rainfall forecasts are conducted with different soil initializations, one from the spatially interpolated North American Mesoscale Forecast System (NAM) and the other produced by the Land Information System (LIS) using daily analysis of bias-corrected stage IV data. Both forecasts are then compared with NAM, stage IV, and Multi-Radar Multi-Sensor (MRMS) quantitative precipitation estimation (QPE) to understand the impact of land surface initialization on the predicted precipitation. In general, both NU-WRF runs are able to reproduce individual peaks of precipitation at the right time. NU-WRF is also able to replicate a better rainfall spatial distribution compared with NAM. Further sensitivity tests show that the highresolution runs (1 and 3 km) are able to better capture the precipitation event compared to its coarser-resolution counterpart (9 km). Finally, the two sets of NU-WRF simulations produce very close rainfall characteristics in bias, spatial and temporal correlation scores, and probability density function. The land surface initialization does not show a significant impact on short-term rainfall forecast, which is largely because of high soil moisture during the field campaign period.

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Section: Introductionmentioning

confidence: 99%

Evaluation of NU-WRF Rainfall Forecasts for IFloodS

Peters‐Lidard

Tao

et al. 2016

Journal of Hydrometeorology

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“…A major concern in this regard is the representation of deep moist convection. Deep convection is generally parameterized and not explicitly predicted when the horizontal grid spacing is greater than about 10 km (see Molinari and Dudek 1986;Kalb 1987;Zhang et al 1988;Gallus and Segal 2001;Bélair and Mailhot 2001;Liu et al 2001;Roberts 2003), but convective parameterization (CP) is typically avoided at higher resolution. This avoidance is appropriate because the conceptual basis for CP becomes increasingly ambiguous as the grid spacing decreases further (Molinari and Dudek 1992;Arakawa 2004).…”

Section: Introductionmentioning

confidence: 99%

Some practical considerations regarding horizontal resolution in the first generation of operational convection-allowing NWP

Kain¹,

Weiss²,

Bright³

et al. 2008

Wea. Forecasting

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During the 2005 NOAA Hazardous Weather Testbed Spring Experiment two different high-resolution configurations of the Weather Research and Forecasting-Advanced Research WRF (WRF-ARW) model were used to produce 30-h forecasts 5 days a week for a total of 7 weeks. These configurations used the same physical parameterizations and the same input dataset for the initial and boundary conditions, differing primarily in their spatial resolution. The first set of runs used 4-km horizontal grid spacing with 35 vertical levels while the second used 2-km grid spacing and 51 vertical levels.Output from these daily forecasts is analyzed to assess the numerical forecast sensitivity to spatial resolution in the upper end of the convection-allowing range of grid spacing. The focus is on the central United States and the time period 18-30 h after model initialization. The analysis is based on a combination of visual comparison, systematic subjective verification conducted during the Spring Experiment, and objective metrics based largely on the mean diurnal cycle of the simulated reflectivity and precipitation fields. Additional insight is gained by examining the size distributions of the individual reflectivity and precipitation entities, and by comparing forecasts of mesocyclone occurrence in the two sets of forecasts.In general, the 2-km forecasts provide more detailed presentations of convective activity, but there appears to be little, if any, forecast skill on the scales where the added details emerge. On the scales where both model configurations show higher levels of skill-the scale of mesoscale convective features-the numerical forecasts appear to provide comparable utility as guidance for severe weather forecasters. These results suggest that, for the geographical, phenomenological, and temporal parameters of this study, any added value provided by decreasing the grid increment from 4 to 2 km (with commensurate adjustments to the vertical resolution) may not be worth the considerable increases in computational expense.

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“…In particular, Zhang and Fritsch (1987) and Zhang et al (1988) pointed out that as the grid size decreases to capably resolve mesoscale features, the grid-scale phase changes need to be described realistically, since it has been widely recognized that with such a grid spacing resolvable-scale updrafts and downdrafts become an integral part of MCSs and phase-change processes (Zipser, 1977 ;Houze, 1977;Ogura and Liou, 1980;Brown, 1979;Leary, 1980;Maddox, 1983). Furthermore, Molinari and Dudek (1986), Kalb (1987) and Zhang et al (1988) found that mesoscale models are prone to the unrealistic development of the conditional instability of the second kind (or the CISK-like instability) when simulating mesovortices or when a model cyclone is falsely generated (so-called numerical point storm) as a result of unsatisfactory mechanisms to release local gravitational instability (also see Kasahara, 1961). (The CISK-like instability is referred to by Zhang et al (1988) as an overenhanced positive feedback process on the resolvable scale among latent heat release, moisture convergence and the surface pressure fall.)…”

Section: Introductionmentioning

confidence: 99%

The effect of parameterized ice microphysics on the simulation of vortex circulation with a mesoscale hydrostatic model

Zhang¹

1989

Tellus A: Dynamic Meteorology and Oceanography

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It has been proposed that ice microphysics, particularly the melting effect, can play an important rde in the generation of mesoscale structure and evolution of convective weather systems and associated stratiform rainfall. In this paper, parameterized cloud ice and snow crystals are incorporated into an explicit (grid-resolved) convective scheme as prognostic variables and tested using an observed mesovortex on a grid resolution of 25 km. With the inclusion of ice microphysics parameterization. the resolvable-scale precipitation begins to develop nearly 1 h earlier and undergoes a more rapid acceleration. Meanwhile, the resulting maximum upward motion and locally accumulated rainfall are significantly larger than that without ice microphysics. However, the model produced a relatively weak mesovortex circulation with the maximum cyclonic vorticity located more than 50 mb higher when the ice microphysics is incorporated. It is found that the freezing and sublimation provide a positive forcing for the rapid development of the mid-tropospheric warm-core vortex circulation, while the melting tends to destroy the concentration of cyclonic vorticity in the lower levels. In particular, intercomparisons among all sensitivity experiments so far performed reveal that the melting effect can be of equal importance to those of the hydrostatic water loading and evaporative cooling in retarding the development of the CISK-like instability and in reducing the intensity of the mesovortex. The results indicate that the vertical distribution of diabatic heating may be more important than the total heating in determining the strength of mesovortices. when the melting effect is considered.

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The Role of Convective Parameterization in the Simulation of a Gulf Coast Precipitation System

Cited by 9 publications

References 0 publications

Evaluation of NU-WRF Rainfall Forecasts for IFloodS

Evaluation of NU-WRF Rainfall Forecasts for IFloodS

Some practical considerations regarding horizontal resolution in the first generation of operational convection-allowing NWP

The effect of parameterized ice microphysics on the simulation of vortex circulation with a mesoscale hydrostatic model

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