Bulk Parameterization of the Snow Field in a Cloud Model

This study aims to investigate the impacts of 30-secondupdate and 100-m-resolution data assimilation (DA) on a prediction of sudden local torrential rains caused by an isolated convective system in Kobe city on 11 September 2014. We perform a Local Ensemble Transform Kalman filter (LETKF) experiment with the Japan Meteorological Agency non-hydrostatic model (JMA-NHM) at 1-km and 100-m resolution using every-30-second radar reflectivity observed by the phased array weather radar (PAWR) at Osaka University. The 1-km-mesh experiment shows that 30-second-update PAWR DA has positive impacts on the analyses and forecasts. Moreover, the 100-m-mesh experiment shows significant advantages in representing the rainfall intensity and fine structure of the convective system. The promising results suggest that 30-second-update, 100-m-mesh DA have a great potential for predicting sudden local rain events.(Citation: Maejima, Y., M. Kunii, and T. Miyoshi, 2017: 30-second-update 100-m-mesh data assimilation experiments: A sudden local rain case in Kobe on 11 September 2014. SOLA, 13, 174−180, doi:10.2151/sola.2017-032.) IntroductionIn modern numerical weather prediction (NWP), improvement for predicting hazardous phenomena is one of the central issues. Among others, much attention has been paid to skillful NWP for severe weather (e.g., Kain et al. 2006, Hohenegger and Schär 2007a, b;Kawabata et al. 2007;Roberts and Lean 2008). Recently, the ensemble Kalman filter (EnKF;Evensen 1994Evensen , 2003 has become a major method in data assimilation (DA), and has contributed to investigate convection-permitting regional NWP (e.g., Zhang et al. 2007;Stensrud et al. 2009Stensrud et al. , 2013Clark et al. 2010;Schwartz et al. 2010; Baldauf et al. 2011;Melhauser and Zhang 2012; Yussolf et al. 2013, Kunii 2014a, Weng and Zhang 2016.Recently, Miyoshi et al. (2016aMiyoshi et al. ( , 2016b reported an innovation of the "Big Data Assimilation" (BDA) technology, implementing a 30-second-update, 100-m-mesh local ensemble transform Kalman filter (LETKF;Hunt et al. 2007) to assimilate data from a Phased Array Weather Radar (PAWR) at Osaka University (Ushio et al. 2014) into regional NWP models known as the Japan Meteorological Agency non-hydrostatic model (JMA-NHM, Saito et al. 2006Saito et al. , 2007 and the Scalable Computing for Advanced Library and Environment-Regional Model (SCALE-RM, Nishizawa et al. 2015). The PAWR captures the rapid development of convective activities every 30 seconds at approximately 100-m resolution. The 100-m-mesh NWP models can resolve the internal structures of convective cells. The BDA system combines these two to enable NWP resolving each cumulonimbus explicitly.This study provides details of a case study shown in the review paper by Miyoshi et al. (2016b) and aims to investigate the benefits of the BDA system for predicting an isolated convective system. We apply the BDA system described by Miyoshi et al. (2016aMiyoshi et al. ( , 2016b for a sudden local severe rainstorm that occurred in the morning of 1...

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“…To calculate these mean terminal velocities, we employ the following equations described in Lin et al (1983): …”

Section: -Second-update 100-m-mesh Data Assimilation Experimentsmentioning

confidence: 99%

30-second-Update 100-m-Mesh Data Assimilation Experiments: A Sudden Local Rain Case in Kobe on 11 September 2014

Maejima

Kunii

Miyoshi

2017

SOLA

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“…First, because some studies (e.g., Gilmore et al 2004;Jankov et al 2005) have shown that the choice of microphysical scheme can have a large impact on the simulated rainfall, the VGR impact associated with the changes in model microphysics was examined for the 23-24 June 2003 case, chosen because of its relatively high QPF skill. The following microphysical schemes were used for this evaluation: WRF single-moment three-class (WSM3; Hong et al 2004), WRF singlemoment five-class (WSM5; Hong et al 2004), WRF single-moment six-class (WSM6; Hong and Lim 2006), Thompson (Thompson et al 2006), Lin (Lin et al 1983), and Ferrier (Rogers et al 2001). Second, the VGR impact for the larger sample of all seven cases was studied with all runs using only the Ferrier microphysical scheme.…”

Section: B Experimental Designmentioning

confidence: 99%

On the Impact of WRF Model Vertical Grid Resolution on Midwest Summer Rainfall Forecasts

Aligo

Gallus

Segal

2009

Weather and Forecasting

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Weather Research and Forecast (WRF) model exploratory sensitivity simulations were performed to determine the impact of vertical grid resolution (VGR) on the forecast skill of Midwest summer rainfall. Varying the VGR indicated that a refined VGR, while adopting the widely used North America Regional Reanalysis (NARR) for initial and lateral boundary conditions, does not necessarily result in a consistent improvement in quantitative precipitation forecasts (QPFs). When averaged over a variety of microphysical schemes in an illustrative case, equitable threat score (ETS) and bias values actually worsened with a greater overpredicted rainfall for half of the rainfall thresholds when the VGR was refined. Averaged over strongly forced cases, ETS values worsened for all rainfall thresholds while biases mostly increased, indicating a further overprediction of rainfall when the number of levels was increased. Skill improved, however, for all rainfall thresholds when the resolution above the melting level was increased. Skill also improved for most rainfall thresholds when the resolution in the surface layer was increased, which is attributed to better-resolved surface turbulent momentum and thermal fluxes. Likewise, a refined VGR resulted in improvements in weakly forced cases, which are governed mostly by thermodynamic forcing and are sensitive to vertical profiles of temperature and moisture. Application of the factor separation method suggested that the refined VGR more frequently had a negative impact on skill through the interaction between lower-atmospheric processes and microphysical processes above the melting level. KeywordsAgronomy, atmospheric process, equitable threat score, illustrative case, lateral boundary conditions, melting levels, microphysical process, negative impacts, quantitative precipitation forecast, reanalysis, sensitivity simulation, summer rainfall, surface layers, thermal fluxes, turbulent momentum, vertical grids, WRF model, atmospheric thermodynamics, climate prediction, rainfall, weather forecasting Varying the VGR indicated that a refined VGR, while adopting the widely used North America Regional Reanalysis (NARR) for initial and lateral boundary conditions, does not necessarily result in a consistent improvement in quantitative precipitation forecasts (QPFs). When averaged over a variety of microphysical schemes in an illustrative case, equitable threat score (ETS) and bias values actually worsened with a greater overpredicted rainfall for half of the rainfall thresholds when the VGR was refined. Averaged over strongly forced cases, ETS values worsened for all rainfall thresholds while biases mostly increased, indicating a further overprediction of rainfall when the number of levels was increased. Skill improved, however, for all rainfall thresholds when the resolution above the melting level was increased. Skill also improved for most rainfall thresholds when the resolution in the surface layer was increased, which is attributed to better-resolved surface turbulent momentum ...

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“…NHM includes the bulk-type cloud microphysics introduced by Ikawa et al (1991). The scheme is based on Lin et al (1983), Murakami (1990), and Murakami et al (1994). The Kain-Fritsch convection scheme (Kain and Fritsch 1990;Kain 2004;Kato et al 2010) is included as a cumulus scheme.…”

Section: Methodsmentioning

confidence: 99%

Summertime Temperature Extremes over Japan in the Late 21st Century Projected by a High-Resolution Regional Climate Model

Murata¹,

Nakano

Kanada

et al. 2012

Journal of the Meteorological Society of Japan

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Future changes in summertime temperature extremes over Japan are projected by a well-developed regional climate model (RCM) with a spatial resolution of 5 km. The performance of the RCM with respect to temperature in the present climate is evaluated first based on observations. Although the di¤erences in the biases (from observations) of daily temperatures between the RCM and the driving atmospheric general circulation model (AGCM) simulations are not statistically significant, root-mean-square errors (from observations) in daily mean and minimum temperatures reproduced by the RCM are smaller than those by the AGCM with a coarser spatial resolution. These results indicate that RCM with a higher spatial resolution has better performance than the driving AGCM in simulating temperature variability. A test of whether the RCM can capture temperature extremes reveals a good quantitative agreement between simulated and observed values in appearance frequency of extreme high temperature for the daily minimum temperature during July and August. The spatial pattern of the upper tail of the frequency distribution for the daily maximum temperature is also in good agreement with observations, although the model values are underestimated.Projected changes for extremely high daily minimum temperature are relatively large in July on the lee side of the Hidaka Mountains, southeast of Hokkaido. This finding can be explained by the foehn phenomenon: changes in the windward Froude number indicate that atmospheric conditions in the future climate are more favorable for the intensification of foehn. In terms of extremely high daily maximum temperature, the di¤erence between the present-day and future climates during August is relatively large over the Tama area, west of Tokyo. Although the foehn phenomenon is not solely responsible for the projected changes, the phenomenon can explain the projected changes when westerly winds prevail over the Tama area, located on the lee side of the Kanto Mountains.

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Bulk Parameterization of the Snow Field in a Cloud Model

Cited by 3,064 publications

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30-second-Update 100-m-Mesh Data Assimilation Experiments: A Sudden Local Rain Case in Kobe on 11 September 2014

30-second-Update 100-m-Mesh Data Assimilation Experiments: A Sudden Local Rain Case in Kobe on 11 September 2014

On the Impact of WRF Model Vertical Grid Resolution on Midwest Summer Rainfall Forecasts

Summertime Temperature Extremes over Japan in the Late 21st Century Projected by a High-Resolution Regional Climate Model

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