scholarly journals A Forecast Advisory for Afternoon Thunderstorm Occurrence in the Taipei Basin during Summer Developed from Diagnostic Analysis*

2016 ◽  
Vol 31 (2) ◽  
pp. 531-552 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Eugene S. Takle
Keyword(s):  
Onset Time ◽  
Sea Breeze ◽  
Forecast Model ◽  
Well Being ◽  
Thunderstorm Activity ◽  
Meteorological Conditions ◽  
Diurnal Variations ◽  
Maximum Rainfall ◽  
Taipei Basin ◽  
Synoptic Conditions

Abstract Summer is a dry season in northern Taiwan. By contrast, the Taipei basin, located in this region, has its maximum rainfall during summer (15 June–31 August), when 78% of this rainfall is contributed by afternoon thunderstorms. This thunderstorm activity occurs during only 20 days in summer. Because of the pronounced impacts on the well-being of three million people in the basin and the relative infrequency of occurrence, forecasting thunderstorm events is an important operational issue in the Taipei basin. The basin’s small size (30 km × 60 km), with two river exits and limited thunderstorm occurrence days, makes the development of a thunderstorm activity forecast model for this basin a great challenge. Synoptic analysis reveals a thunderstorm day may develop from morning synoptic conditions free of clouds/rain, with a NW–SE-oriented dipole located south of Taiwan and southwesterlies straddling the low and high of this dipole. The surface meteorological conditions along the two river valleys exhibit distinct diurnal variations of pressure, temperature, dewpoint depression, relative humidity, and land–sea breezes. The primary features of the synoptic conditions and timings of the diurnal cycles for the four surface variables are utilized to develop a two-step hybrid forecast advisory for thunderstorm occurrence. Step 1 validates the 24-h forecasts for the 0000 UTC (0800 LST) synoptic conditions and timings for diurnal variations for the first five surface variables on thunderstorm days. Step 2 validates the same synoptic and surface meteorological conditions (including sea-breeze onset time) observed on the thunderstorm day. The feasibility of the proposed forecast advisory is successfully demonstrated by these validations.

scholarly journals Interannual Variation of Summer Rainfall in the Taipei Basin

2016 ◽  
Vol 55 (8) ◽  
pp. 1789-1812 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Jenq-Dar Tsay ◽  
Eugene S. Takle
Keyword(s):  
Southern Oscillation ◽  
Summer Rainfall ◽  
Thunderstorm Activity ◽  
River Valley ◽  
Interannual Variations ◽  
Asian Monsoon Region ◽  
Maximum Rainfall ◽  
Vapor Flux ◽  
Taipei Basin ◽  
Northern Taiwan

AbstractThe Taipei basin, located in northern Taiwan, is formed at the intersection of the Tanshui River valley (~30 km) and the Keelung River valley (~60 km). Summer is the dry season in northern Taiwan, but the maximum rainfall in the Taipei basin occurs during 15 June–31 August. The majority of summer rainfall in this basin is produced by afternoon thunderstorms. Thus, the water supply, air/land traffic, and pollution for this basin can be profoundly affected by interannual variations of thunderstorm days and rainfall. Because the mechanism for these interannual variations is still unknown, a systematic analysis is made of thunderstorm days and rainfall for the past two decades (1993–2013). These two variables are found to correlate opposite interannual variations of sea surface temperature anomalies over the National Oceanic and Atmospheric Administration Niño-3.4 region. Occurrence days for afternoon thunderstorms and rainfall amounts in the Taipei basin double during the cold El Niño–Southern Oscillation (ENSO) phase relative to the warm phase. During the latter phase, a stronger cold/drier monsoon southwesterly flow caused by the Pacific–Japan Oscillation weakens the thunderstorm activity in the Taipei basin through the land–sea breeze. In contrast, the opposite condition occurs during the cold ENSO phase. The water vapor flux over the East/Southeast Asian monsoon region converges more toward Taiwan to maintain rainfall over the Taipei basin during the cold ENSO phase than during the warm ENSO phase.

scholarly journals Impact of Afternoon Thunderstorms on the Land–Sea Breeze in the Taipei Basin during Summer: An Experiment

2014 ◽  
Vol 53 (7) ◽  
pp. 1714-1738 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Ming-Cheng Yen ◽  
Jenq-Dar Tsay ◽  
Chi-Chang Liao ◽  
Eugene S. Takle
Keyword(s):  
Life Cycle ◽  
Environmental Conditions ◽  
Sea Breeze ◽  
Thunderstorm Activity ◽  
Land Breeze ◽  
Urban Air ◽  
Open Sea ◽  
Taipei Basin ◽  
Basic Characteristics ◽  
New Perspective

AbstractEnvironmental conditions for the roughly three million people living in the Taipei basin of Taiwan are greatly affected by the land–sea breeze and afternoon thunderstorm activities. A new perspective on the land–sea breeze life cycle and how it is affected by afternoon thunderstorm activity in the Taipei basin during the dry season is provided. During the summer monsoon break–revival phase, about 75% of rainfall in the Taipei basin is produced by afternoon thunderstorms triggered by sea-breeze interactions with the mountains to the south of this basin. Because the basic characteristics of the land–sea breeze and the changes it undergoes through the influence of afternoon thunderstorms have not been comprehensively analyzed/documented, a mini–field experiment was conducted during the summers of 2004 and 2005 to explore these aspects of the land–sea breeze in this basin. Thunderstorm rainfall is found to change not only the basin’s land–sea-breeze life cycle, but also its ventilation mechanism. On the nonthunderstorm day, the sea breeze supplies the open-sea fresh air for about 8 h during the daytime, but the land breeze persists on the thunderstorm day from afternoon to the next morning, acting to sweep polluted urban air out of the basin.

Objective Prediction of Warm Season Afternoon Thunderstorms in Northern Taiwan Using a Fuzzy Logic Approach

2012 ◽  
Vol 27 (5) ◽  
pp. 1178-1197 ◽  
Author(s):  
Pin-Fang Lin ◽  
Pao-Liang Chang ◽  
Ben Jong-Dao Jou ◽  
James W. Wilson ◽  
Rita D. Roberts
Keyword(s):  
Fuzzy Logic ◽  
Warm Season ◽  
Sea Breeze ◽  
Skill Score ◽  
Storm Activity ◽  
Fuzzy Algorithm ◽  
Fuzzy Logic Algorithm ◽  
Taipei Basin ◽  
Synoptic Conditions ◽  
Northern Taiwan

Abstract In this study, a fuzzy logic algorithm is developed to provide objective guidance for the prediction of afternoon thunderstorms in northern Taiwan using preconvective predictors during the warm season (May–October) from 2005 to 2008. The predictors are derived from surface stations and sounding measurements. The study is limited to 277 days when synoptic forcing was weak and thermal instability produced by the solar heating is primarily responsible for thunderstorm initiation. The fuzzy algorithm contains 29 predictors and associated weights. The weights are based on the maximum of the critical success index (CSI) to forecast afternoon thunderstorms. The most important predictors illustrate that under relatively warm and moist synoptic conditions, sea-breeze transport of moisture into the Taipei Basin along with weak winds inland provide favorable conditions for the occurrence of afternoon convective storms. In addition, persistence of yesterday’s convective storm activity contributed to improving today’s forecast. Skill score comparison between the fuzzy algorithm and forecasters from the Taiwan Central Weather Bureau showed that for forecasting afternoon thunderstorms, the fuzzy logic algorithm outperformed the operational forecasters. This was the case for both the calibration and independent datasets. There was a tendency for the forecasters to overforecast the number of afternoon thunderstorm days. The fuzzy logic algorithm is able to integrate the preconvective predictors and provide probability guidance for the prediction of afternoon thunderstorms under weak synoptic-scale conditions, and could be implemented in real-time operations as a forecaster aid.

Enhancement of Afternoon Thunderstorm Activity by Urbanization in a Valley: Taipei

2007 ◽  
Vol 46 (9) ◽  
pp. 1324-1340 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Shih-Yu Wang ◽  
Ming-Cheng Yen
Keyword(s):  
Summer Rainfall ◽  
Southwest Monsoon ◽  
Thunderstorm Activity ◽  
Ground Subsidence ◽  
Maximum Rainfall ◽  
Taipei Basin ◽  
Downwind Side ◽  
River Valleys ◽  
The City ◽  
Northern Taiwan

Abstract Located in northern Taiwan, Taipei is a metropolis surrounded by hills and mountains that form a basin in which two river valleys funnel the surface airflow of this basin to the open sea. Because of the southwest monsoon, summer is a dry season in northern Taiwan but is the season of maximum rainfall in the Taipei basin. This unusual summer rainfall maximum in Taipei is largely produced by afternoon/evening thunderstorms—in particular, on the downwind side and slopes of mountains south of the city. The population in the city of Taipei and the county in which this city is located has more than tripled during the past four decades while land use for building and surface construction increased by a factor of 3. This urbanization may contribute to an increase of 1.5°C in daily mean temperature, a decrease of 1°C in daily temperature range, an increase of more than 67% in the frequency of afternoon/evening thunderstorms, and an increase of 77% in rainfall generated by thunderstorms. These findings may explain the reduction in the water supply deficit to the Taipei metropolitan area and the ground subsidence of the Taipei basin caused by the excessive use of groundwater. Results of this study also provide important information for urban planning and pollution control and for management of the increasing traffic hazards caused by the enhanced thunderstorm activity and rainfall.

scholarly journals The Effect of Variable Sea Surface Temperature on Forecasting Sea Fog and Sea Breezes: A Case Study

2012 ◽  
Vol 51 (5) ◽  
pp. 986-990 ◽  
Author(s):  
Yongming Tang
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Coastal Region ◽  
Weather Forecast ◽  
Sea Breeze ◽  
Forecast Model ◽  
Sea Surface ◽  
Sea Breezes ◽  
Shelf Sea ◽  
Numerical Weather Forecast

AbstractA preliminary study of the effect of sea surface temperature (SST) temporal and spatial variability on regional coastal weather forecasts is described. A high-resolution numerical weather forecast model from the Met Office is run for the U.K. region with hourly updates of SST data obtained from a shelf sea model. When compared with a control run in which SST is maintained with Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) data, it is found that there are significant differences in the coastal-region forecasts for sea breezes and fog formation. The control run underestimates surface temperature and the strength of the sea breeze when compared with the run with hourly SST updates.

scholarly journals Continuous detection and characterization of the Sea Breeze in clear sky conditions using Meteosat Second Generation

2011 ◽  
Vol 11 (12) ◽  
pp. 33357-33377
Author(s):  
I. M. Lensky ◽  
U. Dayan
Keyword(s):  
Second Generation ◽  
Field Measurements ◽  
Sea Breeze ◽  
Atmospheric Conditions ◽  
Clear Sky ◽  
Synoptic Conditions ◽  
Desert Regions ◽  
Convergence Zones ◽  
Sky Conditions ◽  
The Impact

Abstract. The sea breeze (SB) is a thermally induced boundary layer phenomenon that occurs at coastal locations throughout the world. Previous satellite remote sensing studies used low-level clouds formed over the sea-breeze convergence zones to identify the SB. In this study continuous thermal infrared data from a geostationary satellite (Meteosat Second Generation) and concurrent field measurements were used to detect and characterize the SB in clear sky conditions during the summer. Surface data (wind speed and direction) from 11 sites over Israel for ten summer days in July 2010 for three different synoptic circulation categories were selected. In order to assess the impact of the synoptic induced flow on the SB, we looked for the best agreement between surface and satellite SB timing. An independent classification of synoptic categories performed for the ten summer days revealed two distinct patterns of the SB. During weak horizontal pressure gradient (Weak Persian Trough and High to the West), which enables full development of the SB, the timing of the SB from satellite and field measurements were well correlated (R2=0.75), as compared to unfavorable atmospheric conditions (Deep Persian Trough) yielding lower value (R2=0.5). The SB was identified by surface measurements in an earlier time of the day, with respect to the satellite column integrated measurements. Visualizing a product of time series analysis of the satellite data enabled clear distinction of SB behavior under different synoptic categories. Over desert regions the strong thermal contrast enables detection of the SB even under suppressing synoptic conditions (Deep Persian Trough). This method enables detection and timing of the SB over desert regions where clouds and field measurements are scarce, and is applicable worldwide.

scholarly journals Air pollution measurements related to urban traffic in Bucharest

2019 ◽  
Vol 111 ◽  
pp. 06070
Author(s):  
Lelia Letitia Popescu ◽  
Razvan Stefan Popescu ◽  
Andrei Preda ◽  
Karim Limam
Keyword(s):  
Air Pollution ◽  
Particulate Matter ◽  
Solar Radiation ◽  
Meteorological Conditions ◽  
Diurnal Variations ◽  
Urban Traffic ◽  
Ozone Production ◽  
Pollution Level ◽  
Mobile Laboratory ◽  
Btex Compounds

This study is presenting pollution level in Bucharest, the sources being mainly the traffic or vehicles, that became in larger numbers every year. A new mobile laboratory is used which is able to monitor continuously PM2,5, PM10, NOx, NO, NO2, O3, CO, SO2 and BTEX. The diurnal variations are presented in different environmental conditions: rainy day and sunny day, to compare the results and to present which is the outdoor influence of meteorological conditions. Particulate matter is influenced by rain as well as other compounds like BTEX. Ozone production is influenced by the solar radiation, so it’s also an interesting comparison between the two studied cases. BTEX compounds are measured by a mobile chromatograph placed in the lab and presents for every 30min. the diurnal variations of toluene, benzene, m, p, o xylene and ethylbenzene.

scholarly journals On the Efficiency of Using Transpiration Cooling to Mitigate Urban Heat

Climate ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 69 ◽  
Author(s):  
Kai Gao ◽  
Mattheos Santamouris ◽  
Jie Feng
Keyword(s):  
Temperature Difference ◽  
Sap Flow ◽  
Principal Component ◽  
Sea Breeze ◽  
Maximum Temperature ◽  
Transpiration Cooling ◽  
Maximum Temperature Difference ◽  
Large Trees ◽  
Synoptic Conditions ◽  
Multiple Variables

Trees are considered to be effective for the mitigation of urban overheating, and the cooling capacity of trees mainly comes from two mechanisms: transpiration and shading. This study explores the transpiration cooling of large trees in urban environments where the sea breeze dominates the climate. In the experiment, sap flow sensors were used to measure the transpiration rate of two large trees located in Sydney over one year. Also, the temperature difference between the inside and outside of the canopy, as well as the vertical temperature distribution below the canopy, were measured during summer. In this experiment, the temperature under the canopies decreased by about 0.5 degrees from a 0.5 m height to a 3.5 m height, and the maximum temperature difference between the inside and outside of the canopy was about 2 degrees. After applying a principal component analysis of multiple variables, we found that when a strong sea breeze is the primary cooling mechanism, the sap flow still makes a considerable contribution to cooling. Further, the sea breeze and the transpiration cooling of trees are complementary. In conclusion, the characteristics of synoptic conditions must be fully considered when planting trees for mitigation purposes. Since the patterns of sea breeze and sap often do not coincide, the transpiration cooling of trees is still effective when the area is dominated by sea breeze.

A 7-Yr Climatological Study of Land Breezes over the Florida Spaceport

2005 ◽  
Vol 44 (3) ◽  
pp. 340-356 ◽  
Author(s):  
Jonathan L. Case ◽  
Mark M. Wheeler ◽  
John Manobianco ◽  
Johnny W. Weems ◽  
William P. Roeder
Keyword(s):  
Onset Time ◽  
Sea Breeze ◽  
Land Breeze ◽  
Density Currents ◽  
East Central ◽  
Central Florida ◽  
Onshore Flow ◽  
Kennedy Space ◽  
Horizontal Temperature Gradients ◽  
Land Breezes

Abstract Seven years of wind and temperature data from a high-resolution network of 44 towers at the Kennedy Space Center and Cape Canaveral Air Force Station were used to develop an objective method for identifying land breezes, which are defined as seaward-moving wind shift lines in this study. The favored meteorological conditions for land breezes consisted of surface high pressure in the vicinity of the Florida peninsula, mainly clear skies, and light synoptic onshore flow and/or the occurrence of a sea breeze during the afternoon preceding a land breeze. The land breeze characteristics are examined for two events occurring under different weather regimes—one with light synoptic onshore flow and no daytime sea breeze, and another following a daytime sea breeze under a prevailing offshore flow. Land breezes were found to occur over east-central Florida in all months of the year and had varied onset times and circulation depths. Land breezes were most common in the spring and summer months and least common in the winter. The average onset times were ∼4–5 h after sunset from May to July and ∼6.5–8 h after sunset from October to January. Land breezes typically moved from the west or southwest during the spring and summer, from the northwest in the autumn, and nearly equally from all directions in the winter. Shallow land breezes (<150-m depth) were typically not associated with the afternoon sea breeze and behaved like density currents, exhibiting the largest temperature decreases and latest onset times. Deep land breezes (>150-m depth) were most often preceded by an afternoon sea breeze, had the smallest horizontal temperature gradients, and experienced a mean onset time that is 4 h earlier than that of shallow land breezes.

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