scholarly journals Effects of Meteorology Nudging in Regional Hydroclimatic Simulations of the Eastern Mediterranean

Atmosphere ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 470 ◽  
Author(s):  
George Zittis ◽  
Adriana Bruggeman ◽  
Panos Hadjinicolaou ◽  
Corrado Camera ◽  
Jos Lelieveld
Keyword(s):  
Eastern Mediterranean ◽  
Hot Spot ◽  
Wrf Model ◽  
Weather Conditions ◽  
Specific Humidity ◽  
Spectral Nudging ◽  
Precipitation Characteristics ◽  
Simulated Precipitation ◽  
Computational Resources ◽  
Wrf Modeling

In this study, we investigated the effects of grid and spectral nudging in regional hydroclimatic simulations over the Eastern Mediterranean climate change hot-spot. We performed year-long simulations for the hydrological year October 2001–September 2002 using the Weather Research and Forecasting (WRF) model at 12-km resolution, driven by the ERA-Interim reanalyses. Six grid and three spectral nudging options were tested using a number of model configurations. Due to the large uncertainty of regional observations, we compared the model with various satellite- and station-based meteorological datasets. The effect of nudging was tested for mean weather conditions and precipitation characteristics and extremes. For certain parts of the study domain, WRF was found to reproduce both aspects of rainfall over the Eastern Mediterranean reasonably well. Our findings highlighted that, for the WRF modeling system, nudging is critical for the simulation of rainfall; however, the application of interior constraint methods was found to have different impacts on various locations and climatic regimes. For the hyperarid parts of the domain, nudging did not improve the simulation of precipitation amounts (about 20% additional drying was introduced), while it added much value for the wetter rainfall regimes of the Eastern Mediterranean (corrections of about 30%). Improvements in the simulated precipitation were mostly introduced by spectral nudging; however, this option required significant computational resources. For these ERA-Interim-driven simulations, grid nudging that involves specific humidity within the planetary boundary layer is not recommended for the simulation of precipitation since it introduces dry biases up to 75–80%.

scholarly journals The Potential of Satellite Sounding Observations for Deriving Atmospheric Wind in All-Weather Conditions

2021 ◽  
Vol 13 (15) ◽  
pp. 2947
Author(s):  
Yijia Zhang ◽  
Hao Hu ◽  
Fuzhong Weng
Keyword(s):  
Water Vapor ◽  
Wrf Model ◽  
Weather Conditions ◽  
Specific Humidity ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Time Step ◽  
Atmospheric Motion ◽  
Temporal And Spatial ◽  
Surrounding Areas

Atmospheric wind is an essential parameter in the global observing system. In this study, the water vapor field in Typhoon Lekima and its surrounding areas simulated by the Weather Research and Forecasting (WRF) model is utilized to track the atmospheric motion wind through the Farneback Optical Flow (OF) algorithm. A series of experiments are conducted to investigate the influence of temporal and spatial resolutions on the errors of tracked winds. It is shown that the wind accuracy from tracking the specific humidity is higher than that from tracking the relative humidity. For fast-evolving weather systems such as typhoons, the shorter time step allows for more accurate wind retrievals, whereas for slow to moderate evolving weather conditions, the longer time step is needed for smaller retrieval errors. Compared to the traditional atmospheric motion vectors (AMVs) algorithm, the Farneback OF wind algorithm achieves a pixel-wise feature tracking and obtains a higher spatial resolution of wind field. It also works well under some special circumstances such as very low water vapor content or the region where the wind direction is parallel to the moisture gradient direction. This study has some significant implications for the configuration of satellite microwave sounding missions through their derived water vapor fields. The required temporal and spatial resolutions in the OF algorithm critically determine the satellite revisiting time and the field of view size. The brightness temperature (BT) simulated through Community Radiative Transfer Model (CRTM) is also used to track winds. It is shown that the error of tracking BT is generally larger than that of tracking water vapor. This increased error may result from the uncertainty in simulations of brightness temperatures at 183 GHz.

scholarly journals Comprehensive Methodology for the Evaluation of High-Resolution WRF Multi-Physics Precipitation Simulations for Small, Topographically Complex Domains 

2021 ◽  
Author(s):  
Ioannis Sofokleous ◽  
Adriana Bruggeman ◽  
Silas Michaelides ◽  
Panos Hadjinicolaou ◽  
George Zittis ◽  
...  
Keyword(s):  
High Resolution ◽  
Evaluation Method ◽  
Dynamical Downscaling ◽  
Extreme Event ◽  
Eastern Mediterranean ◽  
Wrf Model ◽  
Monthly Precipitation ◽  
Complete Evaluation ◽  
Simulated Precipitation ◽  
Physics Parameterizations

<p> </p><p>A stepwise evaluation method and a comprehensive scoring approach are proposed and applied to select a model setup and physics parameterizations of the Weather Research and Forecasting (WRF) model for high-resolution precipitation simulations. The ERA5 reanalysis data were dynamically downscaled to 1-km resolution for the topographically complex domain of the eastern Mediterranean island of Cyprus. The performance of the simulations was examined for three domain configurations, two model initialization frequencies and 18 combinations of atmospheric physics parameterizations (members). Two continuous scores, i.e., Bias and Mean Absolute Error (MAE) and two categorical scores, i.e., the Pierce Skill Score (PSS) and a new Extreme Event Score (EES) were used for the evaluation. The EES combines hits and frequency bias and it was compared with other commonly used verification scores. A composite scaled score (CSS) was used to identify the five best performing members.</p><p>The EES was shown to be a complete evaluator of the simulation of extremes. The least errors in mean daily and monthly precipitation amounts and daily extremes were found for the domain configuration with the largest extent and three nested domains. A 5-day initialization frequency did not improve precipitation, relative to 30-day continuous simulations. The use of multiple and comprehensive evaluation measures for the assessment of WRF performance allowed a more complete evaluation of the different properties of simulated precipitation, such as daily and monthly volumes and daily extremes, for different dynamical downscaling options and model configurations. The scores obtained for the selected five members for a three-month simulation period ranged for BIAS from zero to -25%, for MAE around 2 mm, for PSS from 0.25 to 0.52 and for EES from 0.19 to 0.26. The CSS ranged from 0.56 to 0.83 for the same members. The proposed stepwise approach can be applied to select an efficient set of WRF multi-physics configurations that accounts for these properties of precipitation and that can be used as input for hydrologic applications.</p>

scholarly journals Numerical Simulations of Airborne Glaciogenic Cloud Seeding Using the WRF Model with the Modified Morrison Scheme over the Pyeongchang Region in the Winter of 2016

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Sanghee Chae ◽  
Ki-Ho Chang ◽  
Seongkyu Seo ◽  
Jin-Yim Jeong ◽  
Baek-Jo Kim ◽  
...  
Keyword(s):  
Wrf Model ◽  
Weather Conditions ◽  
Cloud Microphysics ◽  
Cloud Water ◽  
Weather Research And Forecasting ◽  
Cloud Seeding ◽  
Wind Fields ◽  
Liquid Water Path ◽  
Microphysics Scheme ◽  
Simulated Precipitation

A model was developed for simulating the effects of airborne silver iodide (AgI) glaciogenic cloud seeding using the weather research and forecasting (WRF) model with a modified Morrison cloud microphysics scheme. This model was used to hindcast the weather conditions and effects of seeding for three airborne seeding experiments conducted in 2016. The spatial patterns of the simulated precipitation and liquid water path (LWP) qualitatively agreed with the observations. Considering the observed wind fields during the seeding, the simulated spatiotemporal distributions of the seeding materials, AgI, and snowfall enhancements were found to be reasonable. In the enhanced snowfall cases, the process by which cloud water and vapor were converted into ice particles after seeding was also reasonable. It was also noted that the AgI residence time (>1 hr) above the optimum AgI concentration (105 m−3) and high LWP (>100 g m−2) were important factors for snowfall enhancements. In the first experiment, timing of the simulated snowfall enhancement agreed with the observations, which supports the notion that the seeding of AgI resulted in enhanced snowfall in the experiment. The model developed in this study will be useful for verifying the effects of cloud seeding on precipitation.

scholarly journals Assimilation of Lightning Data Using a Nudging Method Involving Low-Level Warming

2014 ◽  
Vol 142 (12) ◽  
pp. 4850-4871 ◽  
Author(s):  
Max R. Marchand ◽  
Henry E. Fuelberg
Keyword(s):  
Numerical Models ◽  
Deep Convection ◽  
Computational Cost ◽  
Wrf Model ◽  
Stage Iv ◽  
Simulated Precipitation ◽  
Synoptic Forcing ◽  
Total Lightning ◽  
Mu Method ◽  
Short Time

Abstract This study presents a new method for assimilating lightning data into numerical models that is suitable at convection-permitting scales. The authors utilized data from the Earth Networks Total Lightning Network at 9-km grid spacing to mimic the resolution of the Geostationary Lightning Mapper (GLM) that will be on the Geostationary Operational Environmental Satellite-R (GOES-R). The assimilation procedure utilizes the numerical Weather Research and Forecasting (WRF) Model. The method (denoted MU) warms the most unstable low levels of the atmosphere at locations where lightning was observed but deep convection was not simulated based on the absence of graupel. Simulation results are compared with those from a control simulation and a simulation employing the lightning assimilation method developed by Fierro et al. (denoted FO) that increases water vapor according to a nudging function that depends on the observed flash rate and simulated graupel mixing ratio. Results are presented for three severe storm days during 2011 and compared with hourly NCEP stage-IV precipitation observations. Compared to control simulations, both the MU and FO assimilation methods produce improved simulated precipitation fields during the assimilation period and a short time afterward based on subjective comparisons and objective statistical scores (~0.1, or 50%, improvement of equitable threat scores). The MU generally performs better at simulating isolated thunderstorms and other weakly forced deep convection, while FO performs better for the case having strong synoptic forcing. Results show that the newly developed MU method is a viable alternative to the FO method, exhibiting utility in producing thunderstorms where observed, and providing improved analyses at low computational cost.

scholarly journals Effects of Dynamic Crop Growth on the Simulated Precipitation Response to Irrigation*

2015 ◽  
Vol 19 (14) ◽  
pp. 1-31 ◽  
Author(s):  
Keith J. Harding ◽  
Tracy E. Twine ◽  
Yaqiong Lu
Keyword(s):  
Environmental Variability ◽  
Wrf Model ◽  
Crop Growth ◽  
Climate Impacts ◽  
Rapid Expansion ◽  
Area Index ◽  
Community Land Model ◽  
Precipitation Response ◽  
Simulated Precipitation ◽  
Dynamic Crop Growth

Abstract The rapid expansion of irrigation since the 1950s has significantly depleted the Ogallala Aquifer. This study examines the warm-season climate impacts of irrigation over the Ogallala using high-resolution (6.33 km) simulations of a version of the Weather Research and Forecasting (WRF) Model that has been coupled to the Community Land Model with dynamic crop growth (WRF-CLM4crop). To examine how dynamic crops influence the simulated impact of irrigation, the authors compare simulations with dynamic crops to simulations with a fixed annual cycle of crop leaf area index (static crops). For each crop scheme, simulations were completed with and without irrigation for 9 years that represent the range of observed precipitation. Reduced temperature and precipitation biases occur with dynamic versus static crops. Fundamental differences in the precipitation response to irrigation occur with dynamic crops, as enhanced surface roughness weakens low-level winds, enabling more water from irrigation to remain over the region. Greater simulated rainfall increases (12.42 mm) occur with dynamic crops compared to static crops (9.08 mm), with the greatest differences during drought years (+20.1 vs +5.9 mm). Water use for irrigation significantly impacts precipitation with dynamic crops (R2 = 0.29), but no relationship exists with static crops. Dynamic crop growth has the largest effect on the simulated impact of irrigation on precipitation during drought years, with little impact during nondrought years, highlighting the need to simulate the dynamic response of crops to environmental variability within Earth system models to improve prediction of the agroecosystem response to variations in climate.

scholarly journals An Advanced Numerical Trajectory Model Tracks a Corn Earworm Moth Migration Event in Texas, USA

Insects ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 115 ◽  
Author(s):  
Qiu-Lin Wu ◽  
Gao Hu ◽  
John Westbrook ◽  
Gregory Sword ◽  
Bao-Ping Zhai
Keyword(s):  
Helicoverpa Zea ◽  
Wrf Model ◽  
Weather Conditions ◽  
Computational Design ◽  
Corn Earworm ◽  
Long Distance ◽  
Hysplit Model ◽  
Trajectory Model ◽  
Trajectory Simulation ◽  
Migration Event

Many methods for trajectory simulation, such as Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), have been developed over the past several decades and contributed greatly to our knowledge in insect migratory movement. To improve the accuracy of trajectory simulation, we developed a new numerical trajectory model, in which the self-powered flight behaviors of insects are considered and trajectory calculation is driven by high spatio-temporal resolution weather conditions simulated by the Weather Research and Forecasting (WRF) model. However, a rigorous evaluation of the accuracy of different trajectory models on simulated long-distance migration is lacking. Hence, in this study our trajectory model was evaluated by a migration event of the corn earworm moth, Helicoverpa zea, in Texas, USA on 20–22 March 1995. The results indicate that the simulated migration trajectories are in good agreement with occurrences of all pollen-marked male H. zea immigrants monitored in pheromone traps. Statistical comparisons in the present study suggest that our model performed better than the popularly-used HYSPLIT model in simulating migration trajectories of H. zea. This study also shows the importance of high-resolution atmospheric data and a full understanding of migration behaviors to the computational design of models that simulate migration trajectories of highly-flying insects.

scholarly journals Expanding the Goddard CSH Algorithm for GPM: New Extratropical Retrievals

2019 ◽  
Vol 58 (5) ◽  
pp. 921-946 ◽  
Author(s):  
W.-K. Tao ◽  
T. Iguchi ◽  
S. Lang
Keyword(s):  
High Latitude ◽  
Wrf Model ◽  
Tropical Rainfall Measuring Mission ◽  
Consistency Check ◽  
New Classification ◽  
Surface Precipitation ◽  
Winter Conditions ◽  
Simulated Precipitation ◽  
Combined Algorithm ◽  
Self Consistency

AbstractThe Goddard convective–stratiform heating (CSH) algorithm has been used to retrieve latent heating (LH) associated with clouds and cloud systems in support of the Tropical Rainfall Measuring Mission and Global Precipitation Measurement (GPM) mission. The CSH algorithm requires the use of a cloud-resolving model to simulate LH profiles to build lookup tables (LUTs). However, the current LUTs in the CSH algorithm are not suitable for retrieving LH profiles at high latitudes or winter conditions that are needed for GPM. The NASA Unified-Weather Research and Forecasting (NU-WRF) Model is used to simulate three eastern continental U.S. (CONUS) synoptic winter and three western coastal/offshore events. The relationship between LH structures (or profiles) and other precipitation properties (radar reflectivity, freezing-level height, echo-top height, maximum dBZ height, vertical dBZ gradient, and surface precipitation rate) is examined, and a new classification system is adopted with varying ranges for each of these precipitation properties to create LUTs representing high latitude/winter conditions. The performance of the new LUTs is examined using a self-consistency check for one CONUS and one West Coast offshore event by comparing LH profiles retrieved from the LUTs using model-simulated precipitation properties with those originally simulated by the model. The results of the self-consistency check validate the new classification and LUTs. The new LUTs provide the foundation for high-latitude retrievals that can then be merged with those from the tropical CSH algorithm to retrieve LH profiles over the entire GPM domain using precipitation properties retrieved from the GPM combined algorithm.

scholarly journals Comparison of Simulated Precipitation over East Asia in Two Regional Models with Hydrostatic and Nonhydrostatic Dynamical Cores

2016 ◽  
Vol 144 (10) ◽  
pp. 3579-3590 ◽  
Author(s):  
Jihyeon Jang ◽  
Song-You Hong
Keyword(s):  
Wrf Model ◽  
Local Maximum ◽  
Weather Research And Forecasting ◽  
Model Program ◽  
Grid Spacing ◽  
Dynamical Core ◽  
Simulated Precipitation ◽  
Precipitation Area ◽  
Hydrostatic Limit ◽  
Regional Forecasts

This study examines the characteristics of a nonhydrostatic dynamical core compared to a corresponding hydrostatic dynamical core in the Regional Model Program (RMP) of the Global/Regional Integrated Model system (GRIMs), a spectral model for regional forecasts, focusing on simulated precipitation over Korea. This kind of comparison is also executed in the Weather Research and Forecasting (WRF) finite-difference model with the same physics package used in the RMP. Overall, it is found that the nonhydrostatic dynamical core experiment accurately reproduces the heavy rainfall near Seoul, South Korea, on a 3-km grid, relative to the results from the hydrostatic dynamical core in both models. However, the characteristics of nonhydrostatic effects on the simulated precipitation differ between the RMP and WRF Model. The RMP with the nonhydrostatic dynamical core improves the local maximum, which is exaggerated in the hydrostatic simulation. The hydrostatic simulation of the WRF Model displaces the major precipitation area toward the mountainous region along the east coast of the peninsula, which is shifted into the observed area in the nonhydrostatic simulation. In the simulation of a summer monsoonal rainfall, these nonhydrostatic effects are negligible in the RMP, but the simulated monsoonal rainfall is still influenced by the dynamical core in the WRF Model even at a 27-km grid spacing. One of the reasons for the smaller dynamical core effect in the RMP seems to be the relatively strong horizontal diffusion, resulting in a smaller grid size of the hydrostatic limit.

scholarly journals Sensitivity Evaluation of Spectral Nudging Schemes in Historical Dynamical Downscaling for South Asia

2017 ◽  
Vol 2017 ◽  
pp. 1-20 ◽  
Author(s):  
Mehwish Ramzan ◽  
Suryun Ham ◽  
Muhammad Amjad ◽  
Eun-Chul Chang ◽  
Kei Yoshimura
Keyword(s):  
South Asia ◽  
Dynamical Downscaling ◽  
Regional Climate ◽  
Weather Conditions ◽  
Monsoon Precipitation ◽  
Short Term ◽  
Spectral Nudging ◽  
Sensitivity Evaluation ◽  
Constant Strength

Sensitivity experiments testing two scale-selective bias correction (SSBC) methods have been carried out to identify an optimal spectral nudging scheme for historical dynamically downscaled simulations of South Asia, using the coordinated regional climate downscaling experiment (CORDEX) protocol and the regional spectral model (RSM). Two time periods were selected under the category of short-term extreme summer and long-term decadal analysis. The new SSBC version applied nudging to full wind components, with an increased relaxation time in the lower model layers, incorporating a vertical weighted damping coefficient. An evaluation of the extraordinary weather conditions experienced in South Asia in the summer of 2005 confirmed the advantages of the new SSBC when modeling monsoon precipitation. Furthermore, the new SSBC scheme was found to predict precipitation and wind patterns more accurately than the older version in decadal analysis, which applies nudging only to the rotational wind field, with a constant strength at all heights.

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