Evaluation of Precipitating Hydrometeor Parameterizations in a Single-Moment Bulk Microphysics Scheme for Deep Convective Systems over the Tropical Central Pacific

2014 ◽  
Vol 71 (7) ◽  
pp. 2654-2673 ◽  
Author(s):  
Woosub Roh ◽  
Masaki Satoh
Keyword(s):  
Tropical Rainfall Measuring Mission ◽  
Cloud Microphysics ◽  
Horizontal Distribution ◽  
Size Distributions ◽  
Central Pacific ◽  
Microphysics Scheme ◽  
Convective Systems ◽  
Joint Histogram ◽  
Single Moment ◽  
Deep Convective Systems

Abstract Cloud microphysics of deep convective systems over the tropical central Pacific simulated by a cloud system–resolving model using satellite simulators are evaluated in terms of the joint histogram of cloud-top temperature and precipitation echo-top heights. A control experiment shows an underestimation of stratiform precipitation and a higher frequency of precipitating deep clouds with top heights higher than 12 km when compared with data from the Tropical Rainfall Measuring Mission. The comparison shows good agreement for horizontal distribution and statistical cloud size distributions of deep convective systems. Biases in the joint histogram are improved by changing cloud microphysics parameters of a single-moment bulk microphysics scheme. The effects of size distribution of precipitating hydrometeors are examined. Modification of the particle size distributions of rain, snow, and graupel size distributions based on observed relationships improves cloud precipitation statistics. This study implies that a single-moment bulk cloud microphysics scheme can be improved by employing comparison of satellite observations and diagnostic relationships.

Improvement of a Cloud Microphysics Scheme for a Global Nonhydrostatic Model Using TRMM and a Satellite Simulator

2017 ◽  
Vol 74 (1) ◽  
pp. 167-184 ◽  
Author(s):  
Woosub Roh ◽  
Masaki Satoh ◽  
Tomoe Nasuno
Keyword(s):  
Joint Probability ◽  
Tropical Rainfall Measuring Mission ◽  
Atmospheric Model ◽  
Cloud Microphysics ◽  
Horizontal Resolution ◽  
Microphysics Scheme ◽  
Tropical Ocean ◽  
Nonhydrostatic Model ◽  
Joint Histogram ◽  
The Tropics

Abstract The cloud and precipitation simulated by a global nonhydrostatic model with a 3.5-km horizontal resolution, the Nonhydrostatic Icosahedral Atmospheric Model (NICAM), are evaluated using the Tropical Rainfall Measuring Mission (TRMM) and a satellite simulator. A previous study by Roh and Satoh evaluated the single-moment bulk microphysics and established the modified microphysics scheme for the specific tropical open ocean using a regional version of NICAM. In this study, the authors expanded the evaluation over the entire tropics and parts of the midlatitude areas (20°–36°S, 20°–36°N) using a joint histogram of the cloud-top temperature and precipitation echo-top heights and contoured frequency by altitude diagrams of the deep convective systems. The modified microphysics simulation improves the joint probability density functions of the cloud-top temperatures and precipitation cloud-top heights over not only the tropical ocean but also the land and midlatitude areas. Compared with the default microphysics simulation, the modified microphysics simulation shows a clearer distinction between the land and ocean in the tropics, which is related to the contrast between the shallow and the deep clouds. In addition, the two microphysics simulation methods were also compared over the tropics using joint histograms of the cloud-top and precipitation cloud-top heights on the basis of CloudSat measurements. It was found that the microphysics scheme that was modified for the tropical ocean displayed general cloud and precipitation improvements in the global domain over the tropics.

scholarly journals Cloud and Radiative Characteristics of Tropical Deep Convective Systems in Extended Cloud Objects from CERES Observations

2009 ◽  
Vol 22 (22) ◽  
pp. 5983-6000 ◽  
Author(s):  
Zachary A. Eitzen ◽  
Kuan-Man Xu ◽  
Takmeng Wong
Keyword(s):  
Optical Depth ◽  
Large Scale ◽  
Radiant Energy ◽  
Radiative Properties ◽  
Cloud Optical Depth ◽  
Water Path ◽  
Convective Systems ◽  
Joint Histogram ◽  
Deep Convective Systems ◽  
Cloud Top Temperature

Abstract The physical and radiative properties of tropical deep convective systems for the period from January to August 1998 are examined with the use of Clouds and the Earth’s Radiant Energy System Single-Scanner Footprint (SSF) data from the Tropical Rainfall Measuring Mission satellite. Deep convective (DC) cloud objects are contiguous regions of satellite footprints that fulfill the DC criteria (i.e., overcast footprints with cloud optical depths >10 and cloud-top heights >10 km). Extended cloud objects (ECOs) start with the original cloud object but include all other cloudy footprints within a rectangular box that completely covers the original cloud object. Most of the non-DC footprints are overcast but have optical depths and/or cloud-top heights that are too low to fit the DC criteria. The histograms of cloud physical and radiative properties are analyzed according to the size of the ECO and the SST of the underlying ocean. Larger ECOs are associated with greater magnitudes of large-scale upward motion, which supports stronger convection for larger sizes of ECOs. This leads to shifts toward higher values in the DC distributions of cloud-top height, albedo, condensate water path, and cloud optical depth. However, non-DC footprints become less reflective with increasing ECO size, as the longer-lived large convective systems have more time to develop thin cirrus anvils. The proportion of DC footprints remains fairly constant with size. The proportion of DC footprints also remains nearly constant with SST within a given size class, although the number of footprints per object increases with SST for large objects. As SSTs increase, there is a decrease in the proportion of updraft water that goes into detrainment, causing the non-DC distributions of albedo, condensate water path, and cloud optical depth to shift toward lower values. The all-cloud distributions of cloud-top temperature and outgoing longwave radiation (OLR) shift toward lower values as SST increases owing to the increase in convective instability with SST. Both the DC and non-DC distributions of cloud-top temperature do not change much with satellite precession cycle, supporting the fixed anvil temperature hypothesis of Hartmann and Larson. When a joint histogram is formed from the cloud-top pressures and cloud optical depths of the ECOs, it is very similar to the corresponding histogram of the deep convective weather state obtained by cluster analysis of International Satellite Cloud Climatology Project data.

scholarly journals Satellite-Based Assessment of Various Cloud Microphysics Schemes in Simulating Typhoon Hydrometeors

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Ying Zhang ◽  
Yu Wang ◽  
Guosheng Liu ◽  
Jianping Guo ◽  
Yuanjian Yang ◽  
...  
Keyword(s):  
Microwave Radiometer ◽  
Wrf Model ◽  
Cloud Microphysics ◽  
Horizontal Distribution ◽  
Microwave Brightness Temperature ◽  
Joint Histogram ◽  
Double Moment ◽  
Significant Intensity ◽  
Scattering Index ◽  
Ice Water

The accurate simulation of typhoon hydrometeors remains a challenge. This study attempts to evaluate the performances of five microphysics schemes (MPSs) in the Weather Research and Forecasting (WRF) model in simulating the supertyphoon Neoguri in July 2014. The observed microwave brightness temperature, as well as retrieved data from the microwave radiometer imager (MWRI) onboard Chinese FY-3B satellite, are used to test hydrometeor simulations. In particular, two MWRI radiance indices, including the emission index (EI) and scattering index (SI), are used to assess the performance of five MPSs in simulating liquid and frozen hydrometeors, respectively. Overall, the WRF model can well reproduce the overall pattern of typhoon-produced precipitation, albeit with slightly overestimated precipitation in the inner rainband and underestimated precipitation in the stratiform rainband. Moreover, ice water paths (IWPs) from all five MPS simulations are higher than those estimated from MWRI retrieval in most areas, and the spatial pattern and values of IWP for the National Severe Storms Laboratory double-moment MPS (NSSL) are much closer to those for MWRI. The NSSL scheme reproduces a more realistic joint histogram distribution of SI and EI than other MPSs do, relative to the observation. Besides, the nonlinear Lucas–Kanade optical flow approach has been used to reflect the horizontal distribution of hydrometeors in the typhoon. The results show that the simulated EI and SI from the five MPSs show a systematic southwest bias of approximately about 10∼20 km and significant intensity bias in the convection area. Further model sensitivity tests confirm that the NSSL scheme generates more realistic graupel and supercooled water close to the observations among all MPSs. The findings suggest that satellite measurements would be helpful to assess MPSs in numeric weather models, especially for hydrometeor distributions in the whole typhoon system.

scholarly journals Statistics on High-Cloud Areas and Their Sensitivities to Cloud Microphysics Using Single-Cloud Experiments

2009 ◽  
Vol 66 (9) ◽  
pp. 2659-2677 ◽  
Author(s):  
Masaki Satoh ◽  
Yuya Matsuda
Keyword(s):  
Longwave Radiation ◽  
Cloud Microphysics ◽  
Distribution Functions ◽  
Cumulus Clouds ◽  
Microphysics Scheme ◽  
High Cloud ◽  
Probability Distribution Functions ◽  
Single Moment ◽  
Parameter Dependency ◽  
Cloud Ice

Abstract Statistics on high-altitude cloud areas associated with deep cumulus clouds and their sensitivities to cloud microphysics are studied in the framework of single-cloud experiments with an explicit cloud system–resolving model. A comprehensive six-category single-moment bulk cloud microphysics scheme is used to investigate parameter dependency. High-cloud areas are defined by the threshold values of the outgoing longwave radiation, and probability distribution functions of high-cloud areas are obtained. First, resolution dependencies on grid sizes of approximately 3.5, 7, and 14 km are examined. It is found that although quantitative differences are confirmed, diurnal variations in high-cloud covers are similarly captured by all three experiments conducted. The main focus of the sensitivity experiments of cloud microphysics is on the fall speed and number concentration, or mean radius, of ice particles. The results clearly show that the sum of snow and cloud ice amounts is closely related to high-cloud covers. Among the number of experiments conducted, one interesting result is that the intercept parameters of snow and graupel have opposite effects on high-cloud covers. As the intercept parameter of graupel increases, the graupel amount increases because of an increase in the accretion rate of cloud water by graupel, which results in a decrease in the amount of snow and hence a decrease in high-cloud covers. This implies that a greater production of graupel leads to an increase in precipitation efficiency.

scholarly journals Benefits of a Fourth Ice Class in the Simulated Radar Reflectivities of Convective Systems Using a Bulk Microphysics Scheme

2014 ◽  
Vol 71 (10) ◽  
pp. 3583-3612 ◽  
Author(s):  
Stephen E. Lang ◽  
Wei-Kuo Tao ◽  
Jiun-Dar Chern ◽  
Di Wu ◽  
Xiaowen Li
Keyword(s):  
Squall Line ◽  
Microphysics Scheme ◽  
Vapor Growth ◽  
Convective Systems ◽  
Mixing Ratios ◽  
Density Mapping ◽  
Aggregation Effect ◽  
Single Moment ◽  
Simulated Surface ◽  
Cloud Ice

Abstract Current cloud microphysical schemes used in cloud and mesoscale models range from simple one-moment to multimoment, multiclass to explicit bin schemes. This study details the benefits of adding a fourth ice class (frozen drops/hail) to an already improved single-moment three-class ice (cloud ice, snow, graupel) bulk microphysics scheme developed for the Goddard Cumulus Ensemble model. Besides the addition and modification of several hail processes from a bulk three-class hail scheme, further modifications were made to the three-ice processes, including allowing greater ice supersaturation and mitigating spurious evaporation/sublimation in the saturation adjustment scheme, allowing graupel/hail to transition to snow via vapor growth and hail to transition to graupel via riming, wet graupel to become hail, and the inclusion of a rain evaporation correction and vapor diffusivity factor. The improved three-ice snow/graupel size-mapping schemes were adjusted to be more stable at higher mixing ratios and to increase the aggregation effect for snow. A snow density mapping was also added. The new scheme was applied to an intense continental squall line and a moderate, loosely organized continental case using three different hail intercepts. Peak simulated reflectivities agree well with radar for both the intense and moderate cases and were superior to earlier three-ice versions when using a moderate and large intercept for hail, respectively. Simulated reflectivity distributions versus height were also improved versus radar in both cases compared to earlier three-ice versions. The bin-based rain evaporation correction affected the squall line more but overall the agreement among the reflectivity distributions was unchanged. The new scheme also improved the simulated surface rain-rate histograms.

scholarly journals Evaluation of WRF Cloud Microphysics Schemes Using Radar Observations

2015 ◽  
Vol 30 (6) ◽  
pp. 1571-1589 ◽  
Author(s):  
Ki-Hong Min ◽  
Sunhee Choo ◽  
Daehyung Lee ◽  
Gyuwon Lee
Keyword(s):  
Summer Monsoon ◽  
Cross Sections ◽  
Korean Peninsula ◽  
Cloud Microphysics ◽  
Convective Precipitation ◽  
Microphysics Scheme ◽  
Radar Observations ◽  
Single Moment ◽  
Double Moment ◽  
The Difference

Abstract The Korea Meteorological Administration (KMA) implemented a 10-yr project to develop its own global model (GM) by 2020. To reflect the complex topography and unique weather characteristics of the Korean Peninsula, a high-resolution model with accurate physics and input data is required. The WRF single-moment 6-class microphysics scheme (WSM6) and WRF double-moment 6-class microphysics scheme (WDM6) that will be implemented in the Korea GM (KGM) are evaluated. Comparisons of the contoured frequency by altitude diagram (CFAD), time–height cross sections, and vertical profiles of hydrometeors are utilized to assess the two schemes in simulating summer monsoon and convective precipitation cases over the Korean Peninsula during 2011. The results show that WSM6 and WDM6 overestimate the height of the melting level and bright band as compared to radar observations. However, the accuracy of WDM6 is in better agreement with radar observations. This is attributed to the difference in the sedimentation process simulated by the additional second-moment total number concentrations of liquid-phase particles in WDM6. WDM6 creates larger raindrops and higher relative humidity beneath the melting layer, allowing the scheme to simulate a more realistic reflectivity profile than WSM6 for the summer monsoon case. However, for the convective case, both schemes underestimate the precipitation and there is resolution dependence in the WRF Model’s ability to simulate convective precipitation.

scholarly journals Improving Simulations of Convective Systems from TRMM LBA: Easterly and Westerly Regimes

2007 ◽  
Vol 64 (4) ◽  
pp. 1141-1164 ◽  
Author(s):  
S. Lang ◽  
W-K. Tao ◽  
J. Simpson ◽  
R. Cifelli ◽  
S. Rutledge ◽  
...  
Keyword(s):  
Large Scale ◽  
Collection Efficiency ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Squall Line ◽  
Gradual Transition ◽  
Microphysics Scheme ◽  
Easterly Wind ◽  
Low Level ◽  
Convective Systems

Abstract The 3D Goddard Cumulus Ensemble model is used to simulate two convective events observed during the Tropical Rainfall Measuring Mission Large-Scale Biosphere–Atmosphere (TRMM LBA) experiment in Brazil. These two events epitomized the type of convective systems that formed in two distinctly different environments observed during TRMM LBA. The 26 January 1999 squall line formed within a sheared low-level easterly wind flow. On 23 February 1999, convection developed in weak low-level westerly flow, resulting in weakly organized, less intense convection. Initial simulations captured the basic organization and intensity of each event. However, improvements to the model resolution and microphysics produced better simulations as compared to observations. More realistic diurnal convective growth was achieved by lowering the horizontal grid spacing from 1000 to 250 m. This produced a gradual transition from shallow to deep convection that occurred over a span of hours as opposed to an abrupt appearance of deep convection. Eliminating the dry growth of graupel in the bulk microphysics scheme effectively removed the unrealistic presence of high-density ice in the simulated anvil. However, comparisons with radar reflectivity data using contoured-frequency-with-altitude diagrams (CFADs) revealed that the resulting snow contents were too large. The excessive snow was reduced primarily by lowering the collection efficiency of cloud water by snow and resulted in further agreement with the radar observations. The transfer of cloud-sized particles to precipitation-sized ice appears to be too efficient in the original scheme. Overall, these changes to the microphysics lead to more realistic precipitation ice contents in the model. However, artifacts due to the inability of the one-moment scheme to allow for size sorting, such as excessive low-level rain evaporation, were also found but could not be resolved without moving to a two-moment or bin scheme. As a result, model rainfall histograms underestimated the occurrence of high rain rates compared to radar-based histograms. Nevertheless, the improved precipitation-sized ice signature in the model simulations should lead to better latent heating retrievals as a result of both better convective–stratiform separation within the model as well as more physically realistic hydrometeor structures for radiance calculations.

scholarly journals The Use of Partial Cloudiness in a Bulk Cloud Microphysics Scheme: Concept and 2D Results

2018 ◽  
Vol 75 (8) ◽  
pp. 2711-2719 ◽  
Author(s):  
So-Young Kim ◽  
Song-You Hong
Keyword(s):  
Cloud Microphysics ◽  
Cloud Fraction ◽  
Weather Research And Forecasting ◽  
Statistical Relationship ◽  
Microphysics Scheme ◽  
Underlying Assumption ◽  
Alternative Concept ◽  
Single Moment ◽  
Microphysical Processes ◽  
Source And Sink

The source and sink terms of microphysical processes vary nonlinearly with cloud condensate amount. Therefore, partial cloudiness is one of the important factors to be considered in a cloud microphysics scheme given that in-cloud condensate amount depends on the cloud fraction of the grid box. An alternative concept to represent the partial cloudiness effect on the microphysical processes of a bulk microphysics scheme is proposed. Based on the statistical relationship between cloud condensate and cloudiness, all hydrometeors in the microphysical processes are treated after converting them to in-cloud values by dividing the amount by estimated cloudiness and multiplying it after the computation of all microphysics terms. The underlying assumption is that all the microphysical processes occur in a cloudy part of the grid box. In a 2D idealized storm case, the Weather Research and Forecasting (WRF) single-moment 5-class (WSM5) microphysics scheme with the proposed approach increases the amount of snow and rain through enhanced autoconversion/accretion and increases precipitation reaching the surface.

scholarly journals Life cycle of midlatitude deep convective systems in a Lagrangian framework

2012 ◽  
Vol 117 (D23) ◽  
pp. n/a-n/a ◽  
Author(s):  
Zhe Feng ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Sally A. McFarlane ◽  
Aaron Kennedy ◽  
...  
Keyword(s):  
Life Cycle ◽  
Convective Systems ◽  
Lagrangian Framework ◽  
Deep Convective Systems
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