scholarly journals The urban fingerprint in the sea-breeze hodograph reveled by high resolution WRF simulations.

2021 ◽  
Author(s):  
David Avisar ◽  
Ran Pelta ◽  
Alexandra Chudnovsky ◽  
Dorita Rostkier-Edelstein
Keyword(s):  
Wrf Model ◽  
Single Layer ◽  
Urban Canopy ◽  
Sea Breeze ◽  
Building Energy ◽  
Weather Research And Forecasting ◽  
Diurnal Cycles ◽  
Convergence Line ◽  
Urban Heat ◽  
First Time

<p>We implement and verify for the first time four Weather Research and Forecasting (WRF) model urban configurations, focused on the coastal metropolitan area of Tel-Aviv (MTA) using updated land use and urban morphological maps. We analyze the mesoscale summertime flow and the urban canopy (UC) role in the occurrence of different hodograph dynamics observed within MTA at night. These events may be significant in the context of air quality research. The four configurations – bulk (MM), single-layer (SLUCM), multi-layer (BEP), and BEP coupled with the building energy model (BEPBEM) – reproduce the observed diurnal temperature and wind diurnal cycles, with similar 10m wind direction bias and RMSE (15° and ~30°, respectively), with preference for MM and SLUCM at night. However, the SLUCM shows the lowest skill for the 10m wind speed (WS) (bias and RMSE equal or larger than 1ms-1), and the BEP shows the largest underestimation of the 2m temperature, ~-2.5°C. In the SLUCM, the WS increases over an UC region and with increasing building heights. The simulations show that at night, a convergence line (CL) builds up with the urban heat island, downstream of the NW flow. West of the CL, the wind continues flowing from the sea, and rotates anti-clockwise to form a non-elliptical sea-breeze hodograph. Removing MTA UC restores an elliptical hodograph. East of the CL, the UC supports an elliptical hodograph with a clockwise rotation through the NE sector, previously reported as dynamically unstable. We expect such wind hodograph dynamics within similar coastal metropolitan areas.</p>

The urban fingerprint in the sea-breeze hodograph reveled by high resolution WRF simulations

2021 ◽  
Author(s):  
David Avisar ◽  
Ran Pelta ◽  
Alexandra Chudnovsky ◽  
Dorita Rostkier-Edelstein
Keyword(s):  
Single Layer ◽  
Urban Canopy ◽  
Sea Breeze ◽  
Building Energy ◽  
Weather Research And Forecasting ◽  
Clockwise Rotation ◽  
Convergence Line ◽  
Urban Configurations ◽  
Urban Heat ◽  
First Time

<p>We implement and verify for the first time four Weather Research and Forecasting model urban configurations, focused on the coastal metropolitan area of Tel-Aviv (MTA) using updated land use and urban morphological maps. We analyze the mesoscale summertime flow and the urban canopy (UC) role in the occurrence of different hodograph dynamics observed within MTA at night. These events may be significant in air quality research. The four configurations – bulk (MM), single-layer (SLUCM), multi-layer (BEP), and BEP coupled with the building energy model (BEPBEM) – reproduce the observed diurnal temperature and wind cycles, with similar 10m wind direction bias and RMSE (15° and ~30°, respectively), with preference for MM and SLUCM at night. However, the SLUCM shows the lowest skill for the 10m wind speed (WS) (bias and RMSE 1ms<sup>-1</sup>), and the BEP shows the largest underestimation of the 2m temperature, ~-2.5°C. In the SLUCM, the WS increases over an UC and with increasing building heights. The simulations show that at night, a convergence line (CL) builds up with the urban heat island, downstream of the NW flow. West of the CL, the wind continues flowing from the sea, and rotates anti-clockwise to form a non-elliptical sea-breeze hodograph. Removing MTA UC restores an elliptical hodograph. East of the CL, the UC supports an elliptical hodograph with a clockwise rotation through the NE sector, previously reported as dynamically unstable. We expect such wind hodograph dynamics within similar coastal metropolitan areas.</p>

Interaction of Urban Heat Island Effects and Land–Sea Breezes during a New York City Heat Event

2020 ◽  
Vol 59 (3) ◽  
pp. 477-495 ◽  
Author(s):  
Timothy J. Bauer
Keyword(s):  
New York ◽  
New York City ◽  
Wrf Model ◽  
Sea Breeze ◽  
Heat Island ◽  
Model Data ◽  
Sea Temperature ◽  
Heat Event ◽  
Urban Heat ◽  
Surface Observations

AbstractThe state of knowledge of the effects of urban heat islands is advanced through investigation of a heat event in the highly complex coastal environment of New York City (NYC) by using the Weather Research and Forecasting (WRF) Model and surface observations in the NYC metropolitan area to evaluate heat retention at high- and low-temperature times during 18–20 July 2013. Urban surface air temperatures are 1°–2°C higher than rural temperatures throughout the daytime and increase to 3°–5°C higher during the night. Lack of a land–sea temperature gradient prevents development of a land breeze during the night. A land–sea temperature difference approaching 20°C leads to sea-breeze effects during 18 July that reduce daytime skin temperatures, but higher winds greatly reduce the sea breeze during 19 July. WRF Model data are generated using three urban parameterization schemes. The most sophisticated multilayer urban parameterization proves to be most accurate when compared with surface observation data. Errors between WRF Model data and surface observations are attributed to assigned coastal sea surface temperatures, excessive building drag, and too little urban heat retention. Adjustments to the input parameters to the multilayer scheme improved accuracy to lead to the control simulation used for urban heat island effects and land–sea-breeze analysis. NYC building interaction with the synoptic flow generates urban drag and wake effects, although relatively high winds limit their extent. Urban flow results and identified model errors support the development and deployment of the best urban parameterization scheme.

Simulation of Downstream Effects of Urbanization on Cloud and Precipitation with WRF Model in Yangtze River Delta, China

2020 ◽  
Author(s):  
Xiaomen Han ◽  
Jianning Sun
Keyword(s):  
Yangtze River ◽  
Vertical Mixing ◽  
Wrf Model ◽  
Single Layer ◽  
Urban Canopy ◽  
Yangtze River Delta ◽  
River Delta ◽  
Dominant Factor ◽  
Urbanization Effect ◽  
Downstream Effects

<p>Urbanization, one of the extreme cases of land-use change, plays an important role in modifying precipitation and urban hydrology. In this study, urbanization effect on cloud and precipitation in the Yangtze River Delta of China is simulated using Weather Research and Forecasting (WRF) model coupled with a single-layer Urban Canopy Model(SLUCM). Based on the 4-summer simulation results from 2011 to 2014, we find that the influence of cities on clouds and precipitation is obviously affected by wind field. During the day, more cloud on higher level and precipitation occurs in urban area and downwind region of urban, induced by more unstable urban air transported downstream, which enhances vertical mixing and updraft moisture transport. At night, the urban dry island become the dominant factor, resulting in the decrease of cloud occurrence in the urban and downstream areas. The downstream effects of urbanization on cloud and precipitation turn out to be strongly related to the moisture and convective conditions.</p><p> </p>

Sensitivity of Predictions of the Urban Surface Energy Balance and Heat Island to Variations of Urban Canopy Parameters in Simulations with the WRF Model

2017 ◽  
Vol 56 (3) ◽  
pp. 573-595 ◽  
Author(s):  
Kodi L. Nemunaitis-Berry ◽  
Petra M. Klein ◽  
Jeffrey B. Basara ◽  
Evgeni Fedorovich
Keyword(s):  
Climate Models ◽  
Wrf Model ◽  
Single Layer ◽  
Urban Canopy ◽  
Heat Fluxes ◽  
Urban Air ◽  
Near Surface ◽  
Air Temperatures ◽  
Oklahoma Mesonet ◽  
Joint Urban 2003 Experiment

AbstractAs NWP and climate models continue to evolve toward finer grid spacing, efforts have been undertaken to better represent urban effects. For this study, the single-layer urban canopy model (SLUCM) of the High-Resolution Land Data Assimilation System (HRLDAS) and WRF Model was used to investigate the sensitivity of near-surface air temperatures and energy fluxes to SLUCM parameters in uncoupled (land) and coupled (land–atmosphere) predictions. Output from HRLDAS and WRF was compared with observations from the Oklahoma Mesonet and Joint Urban 2003 experiment. Variations in roof albedo (0.04–0.4) produced 40–135 W m−2 changes in net radiation and sensible heat fluxes. Sensible and ground heat fluxes varied by 40–100 W m−2 with changes in roof thermal conductivity (0.05–1.4). The urban fraction was found to be the only SLUCM parameter to significantly impact latent heat fluxes. Near-surface air temperatures, particularly during the daytime, did not show significant variations with SLUCM parameters (remaining within the 0.5-K range). Differences in urban air temperatures due to the change in boundary layer scheme were greater than the temperature changes due to SLUCM parameter variations. The sensitivity of near-surface air temperatures to SLUCM parameters depended on the method used to calculate the skin temperature of the impervious surface. For all simulations, predicted 2-m urban air temperatures were consistently higher than observations, with deviations approaching 8 K during the day and below 3 K at night. These large errors affected the model’s skill in reproducing the diurnal cycle of UHI intensity.

scholarly journals The Influences of Urban Building Complexes on the Ambient Flows over the Washington–Reston Region

2019 ◽  
Vol 58 (6) ◽  
pp. 1325-1336 ◽  
Author(s):  
Da-Lin Zhang ◽  
Menglin S. Jin ◽  
Yixuan Shou ◽  
Chunqing Dong
Keyword(s):  
Mesoscale Model ◽  
Urban Canopy ◽  
Static Stability ◽  
Wake Flow ◽  
Weather Research And Forecasting ◽  
Flow Strength ◽  
Blocking Effects ◽  
Downwind Side ◽  
Urban Heat ◽  
Canopy Model

AbstractThis paper examines the collective impacts of urban building complexes on the planetary boundary layer (PBL) winds using both observations and a mesoscale model. Horizontal winds measured on the rooftops of federal buildings over the regions of Washington, D.C., and a small city nearby (i.e., Reston, Virginia) show the blocking effects of urban building complexes on the downstream winds during the daytime of 9 July 2007. A modeling study of the case using a coupled version of the Weather Research and Forecasting (WRF)–multilayer urban canopy model in which the observed building height and density information is implemented to advance the calculations of momentum and heat, reproduces the rooftop-observed wind patterns and the related urban heat island effects, especially the wake flows on the downstream sides of the above-mentioned two cities. Results show that under daytime conditions the building complexes can collectively form a mesoscale wake on the downwind side of each city, about 2–10 km away, horizontally from the edge of the building complexes. The wake flow may extend to much higher levels than the building tops, depending on the incoming flow strength, the static stability in the PBL, the height of the building complexes, and the time of the day because of the strength of surface insolation.

scholarly journals Comparison of the Diurnal Precipitation Cycle in Convection-Resolving and Non-Convection-Resolving Mesoscale Models

2007 ◽  
Vol 135 (10) ◽  
pp. 3456-3473 ◽  
Author(s):  
Adam J. Clark ◽  
William A. Gallus ◽  
Tsing-Chang Chen
Keyword(s):  
United States ◽  
Spatial Correlation ◽  
Diurnal Cycle ◽  
Wrf Model ◽  
Correlation Coefficients ◽  
Weather Research And Forecasting ◽  
Grid Spacing ◽  
Diurnal Cycles ◽  
Central United States ◽  
Precipitation Cycle

Abstract The diurnal cycles of rainfall in 5-km grid-spacing convection-resolving and 22-km grid-spacing non-convection-resolving configurations of the Weather Research and Forecasting (WRF) model are compared to see if significant improvements can be obtained by using fine enough grid spacing to explicitly resolve convection. Diurnally averaged Hovmöller diagrams, spatial correlation coefficients computed in Hovmöller space, equitable threat scores (ETSs), and biases for forecasts conducted from 1 April to 25 July 2005 over a large portion of the central United States are used for the comparisons. A subjective comparison using Hovmöller diagrams of diurnally averaged rainfall show that the diurnal cycle representation in the 5-km configuration is clearly superior to that in the 22-km configuration during forecast hours 24–48. The superiority of the 5-km configuration is validated by much higher spatial correlation coefficients than in the 22-km configuration. During the first 24 forecast hours the 5-km model forecasts appear to be more adversely affected by model “spinup” processes than the 22-km model forecasts, and it is less clear, subjectively, which configuration has the better diurnal cycle representation, although spatial correlation coefficients are slightly higher in the 22-km configuration. ETSs in both configurations have diurnal oscillations with relative maxima occurring in both configurations at forecast hours corresponding to 0000–0300 LST, while biases also have diurnal oscillations with relative maxima (largest errors) in the 22-km (5-km) configuration occurring at forecast hours corresponding to 1200 (1800) LST. At all forecast hours, ETSs from the 22-km configuration are higher than those in the 5-km configuration. This inconsistency with some of the results obtained using the aforementioned spatial correlation coefficients reinforces discussion in past literature that cautions against using “traditional” verification statistics, such as ETS, to compare high- to low-resolution forecasts.

scholarly journals URBAN MICRO CLIMATE MODELLING USING DIFFERENT URBAN PHYISCS SCHEMES AND HIGH RESOLUTION LULC WITH WRF MODEL

2018 ◽  
Vol XLII-5 ◽  
pp. 491-498 ◽  
Author(s):  
M. Bhavana ◽  
K. Gupta ◽  
P. K. Pal
Keyword(s):  
High Resolution ◽  
Wind Speed ◽  
Relative Humidity ◽  
Wrf Model ◽  
Urban Canopy ◽  
Building Energy ◽  
Urban Morphology ◽  
Urban Land Use ◽  
Single Class ◽  
Ground Observation

<p><strong>Abstract.</strong> Urban areas are treated as a single entity by mesoscale urban canopy models (UCM) for assessing the influence of urban morphology on climate. Weather Research and Forecasting Model (WRF) coupled with UCM along with urban physics options to describe the urban features such as Single Layer Urban Canopy Model (SLUCM), Building Energy Parameterization (BEP) and Building Energy Model (BEM) which enumerates the influence of urban features on the local scale other than the bulk parameterization (no urban physics option), which is generally used in most of the operational forecasting models. Besides, WRF model also enables to integrate multi-class Urban Land Use Land Cover (LULC) whereas most of the globally available LULC depict urban area as single urban built-up class. This study aims to analyze performance of high resolution urban LULC and urban physics options for Chandigarh area by downscaling climatic variables up to 1km and its validation with the ground observation data. The inner domain (1<span class="thinspace"></span>km resolution) was configured with default LULC for one set of simulations and multi-class urban LULC for other set of simulations. All the simulations were carried out for 3 days (August 19&amp;ndash;21, 2017) due to computational restrictions by employing all the four urban physics options. It has been found that multi-class urban LULC yielded better results than single class urban built –up simulation when validated with respect to ground observation. The RMSE values for multi-class urban LULC provided less RMSE than single class urban LULC, those are in terms of temperature at 2<span class="thinspace"></span>m, relative humidity and wind speed are 0.91<span class="thinspace"></span>&amp;deg;C, 2.63% and 1.82<span class="thinspace"></span>m/s respectively. Similarly, BEP+BEM urban physics option provided reduced RMSE values than the SLUCM and BEP scheme. The RMSE values in terms of temperature at 2<span class="thinspace"></span>m, relative humidity and wind speed are 1.11<span class="thinspace"></span>&amp;deg;C, 4.39% and 2.62<span class="thinspace"></span>m/s respectively.</p>

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