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- Author or Editor: Teddy Holt x
- Journal of Applied Meteorology and Climatology x
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Abstract
Multiply nested urbanized mesoscale model [Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS)] simulations of the New York–New Jersey metropolitan region are conducted for 4–11 July 2004. The simulations differ only in their specification of sea surface temperatures (SSTs) on nest 4 (1.33-km resolution) and nest 5 (0.44-km resolution). The “control SST” simulation (CONTROL-SST) uses an analyzed SST product, whereas the “New York Harbor Observing and Prediction System (NYHOPS) SST” simulation (NYHOPS-SST) uses hourly SSTs from the NYHOPS model hindcast. Upwelling-favorable (southerly) winds preceding the simulation time period and continuing for much of the first 5 days of the simulation generate cold water adjacent to the New Jersey coast and a cold eddy immediately outside of the harbor in the New York Bight. Both features are prominent in NYHOPS-SST but are not pronounced in CONTROL-SST. The upwelled water has a discernible influence on the overlying atmosphere by cooling near-surface air temperatures by approximately 1°–2°C, slowing the near-surface winds by 15%–20%, and reducing the nocturnal urban heat island effect by up to 1.3°C. At two coastal land-based sites and one overwater station, the wind speed mean bias is systematically reduced in NYHOPS-SST. During a wind shift to northwesterly on day 6 (9 July 2004) the comparatively cooler NYHOPS-SSTs impact the atmosphere over an even broader offshore area than was affected in the mean during the previous 5 days. Hence, air temperature evolution measured at the overwater site is better reproduced in NYHOPS-SST. Interaction of the offshore flow with the cool SSTs in NYHOPS-SST induces internal boundary layer (IBL) formation, sustained and deepened by turbulent kinetic energy advected from adjacent land areas; IBL formation did not occur in CONTROL-SST.
Abstract
Multiply nested urbanized mesoscale model [Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS)] simulations of the New York–New Jersey metropolitan region are conducted for 4–11 July 2004. The simulations differ only in their specification of sea surface temperatures (SSTs) on nest 4 (1.33-km resolution) and nest 5 (0.44-km resolution). The “control SST” simulation (CONTROL-SST) uses an analyzed SST product, whereas the “New York Harbor Observing and Prediction System (NYHOPS) SST” simulation (NYHOPS-SST) uses hourly SSTs from the NYHOPS model hindcast. Upwelling-favorable (southerly) winds preceding the simulation time period and continuing for much of the first 5 days of the simulation generate cold water adjacent to the New Jersey coast and a cold eddy immediately outside of the harbor in the New York Bight. Both features are prominent in NYHOPS-SST but are not pronounced in CONTROL-SST. The upwelled water has a discernible influence on the overlying atmosphere by cooling near-surface air temperatures by approximately 1°–2°C, slowing the near-surface winds by 15%–20%, and reducing the nocturnal urban heat island effect by up to 1.3°C. At two coastal land-based sites and one overwater station, the wind speed mean bias is systematically reduced in NYHOPS-SST. During a wind shift to northwesterly on day 6 (9 July 2004) the comparatively cooler NYHOPS-SSTs impact the atmosphere over an even broader offshore area than was affected in the mean during the previous 5 days. Hence, air temperature evolution measured at the overwater site is better reproduced in NYHOPS-SST. Interaction of the offshore flow with the cool SSTs in NYHOPS-SST induces internal boundary layer (IBL) formation, sustained and deepened by turbulent kinetic energy advected from adjacent land areas; IBL formation did not occur in CONTROL-SST.
Abstract
In this study, we use observational and numerical model data from the Coupled Air Sea Processes and Electromagnetic Ducting Research (CASPER) field campaign to describe the mean refractive conditions offshore Duck, North Carolina. The U.S. Navy operational numerical weather prediction model known as the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) performed well forecasting large-scale conditions during the experiment, with an observed warm bias in SST and cold and dry biases in temperature and humidity in the lowest 2000 m. In general, COAMPS underpredicted the number of ducts, and they were weaker and at lower height than those seen in observations. It was found that there is a noticeable diurnal evolution of the ducts, more over land than over the ocean. Ducts were found to be more frequent over land but overall were stronger and deeper over the ocean. Also, the evaporative duct height increases as one moves offshore. A case study was chosen to describe the electromagnetic properties under different synoptic conditions. In this case the continental atmospheric boundary layer dominates and interacts with the marine atmospheric boundary layer. As a result, the latter moves around 80 km offshore and then back inland after 2 h.
Abstract
In this study, we use observational and numerical model data from the Coupled Air Sea Processes and Electromagnetic Ducting Research (CASPER) field campaign to describe the mean refractive conditions offshore Duck, North Carolina. The U.S. Navy operational numerical weather prediction model known as the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) performed well forecasting large-scale conditions during the experiment, with an observed warm bias in SST and cold and dry biases in temperature and humidity in the lowest 2000 m. In general, COAMPS underpredicted the number of ducts, and they were weaker and at lower height than those seen in observations. It was found that there is a noticeable diurnal evolution of the ducts, more over land than over the ocean. Ducts were found to be more frequent over land but overall were stronger and deeper over the ocean. Also, the evaporative duct height increases as one moves offshore. A case study was chosen to describe the electromagnetic properties under different synoptic conditions. In this case the continental atmospheric boundary layer dominates and interacts with the marine atmospheric boundary layer. As a result, the latter moves around 80 km offshore and then back inland after 2 h.
Abstract
Results are presented from a tracer-release modeling study designed to examine atmospheric transport and dispersion (“T&D”) behavior surrounding the complex coastal–urban region of New York City, New York, where air–sea interaction and urban influences are prominent. The puff-based Hazard Prediction Assessment Capability (HPAC, version 5) model is run for idealized conditions, and it is also linked with the urbanized COAMPS (1 km) meteorological model and the NAM (12 km) meteorological model. Results are compared with “control” plumes utilizing surface meteorological input from 22 weather stations. In all configurations, nighttime conditions result in plume predictions that are more sensitive to small changes in wind direction. Plume overlap is reduced by up to 70% when plumes are transported during the night. An analysis of vertical plume cross sections and the nature of the underlying transport and the dispersion equations both suggest that heat flux gradients and boundary layer height gradients determine vertical transport of pollutants across land–sea boundaries in the T&D model. As a consequence, in both idealized and realistic meteorological configurations, waterfront releases generate greater plume discrepancies relative to plumes transported over land/urban surfaces. For transport over water (northwest winds), the higher-fidelity meteorological model (COAMPS) generated plumes with overlap reduced by about one-half when compared with that of the coarser-resolution NAM model (13% vs 24% during the daytime and 11% vs 18% during the nighttime). This study highlights the need for more sophisticated treatment of land–sea transition zones in T&D calculations covering waterside releases.
Abstract
Results are presented from a tracer-release modeling study designed to examine atmospheric transport and dispersion (“T&D”) behavior surrounding the complex coastal–urban region of New York City, New York, where air–sea interaction and urban influences are prominent. The puff-based Hazard Prediction Assessment Capability (HPAC, version 5) model is run for idealized conditions, and it is also linked with the urbanized COAMPS (1 km) meteorological model and the NAM (12 km) meteorological model. Results are compared with “control” plumes utilizing surface meteorological input from 22 weather stations. In all configurations, nighttime conditions result in plume predictions that are more sensitive to small changes in wind direction. Plume overlap is reduced by up to 70% when plumes are transported during the night. An analysis of vertical plume cross sections and the nature of the underlying transport and the dispersion equations both suggest that heat flux gradients and boundary layer height gradients determine vertical transport of pollutants across land–sea boundaries in the T&D model. As a consequence, in both idealized and realistic meteorological configurations, waterfront releases generate greater plume discrepancies relative to plumes transported over land/urban surfaces. For transport over water (northwest winds), the higher-fidelity meteorological model (COAMPS) generated plumes with overlap reduced by about one-half when compared with that of the coarser-resolution NAM model (13% vs 24% during the daytime and 11% vs 18% during the nighttime). This study highlights the need for more sophisticated treatment of land–sea transition zones in T&D calculations covering waterside releases.
