Breeze Circulation Research Articles

Numerical Modeling for the Accidental Dispersion of Hazardous Air Pollutants in the Urban Metropolitan Area

A numerical simulation system is developed to predict the dispersion of hazardous air pollutants (HAPs) over a populated city due to accidental release. Ulsan, as one of the megacities in Korea, is chosen as an ideal testbed for the simulation, as it is located in complex terrain and hosts a national industrial complex on the outskirts of the city. The system is based on the California puff model (CALPUFF) for simulating a HAP’s dispersion, in which the three-dimensional atmospheric circulation derived from the observed weather station data is specified at a fine horizontal resolution of 200 m. A test scenario is developed for the accidental release of benzene during the daytime and nighttime, respectively, by a fictitious explosion of a storage container, and the injection amount is determined arbitrarily yet comparable to those in the past accidents. In attempting a quantitative assessment and zoning the level of potential risk over the impacted area, multiple simulations have been conducted each day with different hourly varying meteorological conditions in August. The dispersion characteristics of the air pollutant depend largely on the local wind patterns that vary substantially from day to day. Nevertheless, the composite analysis sufficiently identifies the impacted area by the HAP’s dispersion due to the local prevailing wind such as the land–sea breeze circulation. An immediate hazardous area is determined based on the vulnerability map constructed by zoning the level of risk determined by the spatial distribution of the HAPs’ concentration and the harmfulness standard to the human body.

The impact of steel emissions on air quality and pollution control strategy in Caofeidian, North China

Pollutant emission from steel industries is an important source of air pollution in Beijing-Tianjin-Hebei region. Using WRF-FLEXPART atmospheric diffusion model, this paper simulated the pollutant diffusion processes of two steel industries from Oct. 2018 to Mar. 2019 in Caofeidian district, and then analysed the pollutant diffusion characteristics, the impacts of atmospheric circulation and local circulation on pollutants diffusion, the contribution of steel industry emissions on air quality nearby emission sources and air quality observation stations. According to the statistics, the emissions of particulate matter from Jingtang (JT)and Wenfeng (WF) steelworks are 669 and 69tonsduring the period of Oct. 2018–Mar. 2019, respectively. Under the influence of East Asian winter monsoon circulation, most of the pollutants emitted from JT and WF are diffused and transported to the Bohai Sea. The contribution of emissions from JT and WF on the concentration of particulate matter with aerodynamic diameters of less than 2.5(PM2.5) in Caofeidian is relatively small, with the daily maximums of local contribution rate on PM2.5 concentration from JT and WF reaching about 15% for both. Compared to the local contribution, the contribution rate in air quality observation stations is obviously lower, with the daily maximumsless than 2% and 5% for JT and WF respectively. It is significant that the pollutant diffusion and its contribution on air quality are affected by the large-scale atmospheric circulation and local sea-land breeze circulation, providing rational insights for policy makers to formulate control strategies.

Dominance of Shortwave Radiative Heating in the Sea‐Land Breeze Amplitude and its Impacts on Atmospheric Visibility in Tokyo, Japan

AbstractThis study uses 21‐year observations to analyze the characteristics of sea‐land breeze (SLB) circulation and its potential influencing factors in the metropolis of Tokyo. Unlike in other megacities, the magnitude of the SLB in Tokyo does not show a decreasing trend over the years. It is found that the diurnal variation magnitude of the SLB fits an approximately sinusoidal function. The diurnal variation amplitude mainly depends on shortwave radiation that reaches the ground. Stronger radiation is often accompanied by SLB circulation with greater energy, which helps transport more air pollution in the urban area of Tokyo. Correspondingly, atmospheric visibility shows good correlation with in situ shortwave radiation. Generally, strong radiation heats the ground surface, which causes larger land‐sea temperature differences and thus greater SLB circulation amplitudes, which is favorable for pollution dispersion and better atmospheric visibility. The presence of less aerosols and the associated better atmospheric visibility weaken the umbrella effect on solar radiation, which allows more solar radiation to reach the ground. This positive feedback could further strengthen the connection between solar radiation, sea‐land breezes, and atmospheric visibility. Increasing solar radiation and atmospheric visibility even produces stronger SLB magnitudes at night. Moreover, it is noteworthy that urban heat island circulation plays a similar role to that of SLB circulation, which also makes the variation of in situ radiation and visibility synchronous.

Long-term observations of aerosol optical properties at three GAW regional sites in the Central Mediterranean

In this work we present the results of the four-years (2015–2018) data-analysis of aerosols optical extensive properties such as scattering (σsc) and backscattering coefficients (σbsc), scattering Ångström exponent (SAE), single scattering albedo (SSA), and asymmetry parameter (g). They were measured at three GAW (Global Atmosphere Watch-WMO) regional observatories in the South of Italy: CGR (Capo Granitola), LMT (Lamezia Terme) and ECO (Lecce). The aim of this work is to characterize the optical properties of the aerosols, in terms of scattering, absorption and radiative forcing, to study their relationship with the equivalent black carbon (eBC) mass concentration, meteorological parameters and to evaluate their variability in the Central Mediterranean area. From the mean values of SAE (1.73 ECO, 1.93 LMT) and SSA (0.81 ECO, 0.78 LMT) observations can be argued that ECO and LMT are mainly influenced by ultrafine particles, while CGR, with mean values of SAE and SSA of 1.15 and 0.87, respectively, is characterized by natural sources, mainly marine. In all stations, g550 is very similar, 0.68 at CGR and 0.63 at LMT, with the greatest value (0.70) at ECO. The aerosol optical properties, at the three stations, are significantly influenced by the meteorological conditions. The daily pattern for eBC concentration at ECO and LMT is essentially influenced by local activities, namely due to vehicular traffic, and, for LMT, to local sea-land breeze circulation. Wood burning is the main source contribute to eBC concentration in the remote site of CGR. Aerosols optical properties were analysed in the cold (from October to March) and warm (from April to September) period in the three observatories to highlight the behaviour of optical parameters as a response to changing black carbon concentration, especially, from local sources. As expected, three observatories exhibited low values of SSA, during the cold season, 0.87 at CGR, 0.78 at LMT and 0.80 at ECO, which confirm an increment of industrial/traffic and wood combustion contributions at the three observatories. SSA values are very similar in warm and cold period, especially in the middle part of the day. A persistent and important results in the findings of this study is that aerosol optical properties vary widely from station to station throughout the central Mediterranean basin. Thus, the wide spatial and temporal variability of aerosol characteristics in the basin need additional investigations to study the relationship between particle size distribution, optical parameters and local sources contribution at the three sites. Further, our results show a negative radiative forcing of aerosols, with mean values of −58.8 at CGR, −45.4 at LMT and − 55.9 at ECO, according also to several studies in central Mediterranean area.

Impact of land surface physics in WRF on the simulation of sea breeze circulation over southeast coast of India

In this work, the impact of land surface physics in simulating the sea and land breeze circulation along the south east coast of India near Kalpakkam is studied using the Weather Research and Forecasting (WRF) model for emergency response application. Simulations were conducted with three different land surface models (LSMs)—5-Layer soil thermal diffusion scheme (5-Layer), Noah land surface model (Noah) and Noah Multi-Physics land surface model (Noah-MP) for different days in summer and southwest monsoon. Observations from meteorological towers, automated weather stations, sonic anemometers and GPS Radiosonde profiles were used for comparison. Results indicate that the Noah-MP followed by Noah schemes produce more realistic simulations of the sea breeze circulation in terms of intensity, onset time, duration, horizontal and vertical extents in most of the studied cases compared to the 5-Layer scheme. Results indicate that the 5-Layer model grossly overestimated air temperature, heat flux and boundary layer height relative to Noah and Noah-MP schemes. The Noah-MP scheme better represented the land-surface feedback in terms of soil temperature, skin temperature and surface energy fluxes leading to more realistic simulations of sea breeze and boundary layer characteristics.

The local climate impact of an African city during clear‐sky conditions—Implications of the recent urbanization in Kampala (Uganda)

AbstractThis study aims at assessing and understanding the impact of recent urbanization on the (surface) urban heat island ((S)UHI) under clear‐sky conditions in a tropical African city using different sources of remotely sensed data sets together with an urban climate model (UCM). The observed SUHI during clear sky conditions is found to be about 4°C on average over the capital city of Kampala, Uganda. The UCM, consisting of TERRA_URB embedded in COSMO‐CLM, represents the SUHI well during night but overestimates it by about 3°C in the mean during day. Moreover, a systematic warm land surface temperature bias of about 4°C is identified by night. Improved urban input parameters—derived from Local Climate Zones following the World Urban Database and Access Portal Tool (WUDAPT) framework—lead to a more realistic representation of spatial land surface temperatures patterns. In addition, this parameterization of the UCM can properly represent atmospheric variables such as air temperature, specific and relative humidity, as observed by the automated weather stations. A model sensitivity study furthermore demonstrates that the stronger urban heat island induced by the recent urbanization of Kampala over the past 15 years strongly interacts with the lake–land breeze circulation. Stronger daytime convection over the hotter city leads to areas of convergence that amplify the afternoon lake breeze in the Southern parts of the metropolis. Overall, this study demonstrates that the city of Kampala has a tangible effect on the regional climate that needs to be considered when studying present and future climate impacts.

Simulated effects of land immersion on regional arid climate: a case study of the pre-Saharan playa of Chott el-Jerid (south of Tunisia)

The potential effects on the regional climate induced by partially immersing the arid pre-Saharan playa basin of Chott el-Jerid (south of Tunisia) are investigated by comparing two multi-year (1991–2011) sets of numerical simulations each consisting of ten-member ensemble and performed using the WRF regional climate model. The first WRF ensemble is performed under current land use and land cover, while the second is carried out after introducing a virtual large and shallow surface water reservoir (a lake) in Chott el-Jerid. The most pronounced effects generated by the artificial lake are circumscribed over its surface and slightly spread downwind to the other parts of the Chott. The lake has a clear moderating effect on near-surface air temperatures by increasing (decreasing) the wintertime (summertime) air temperatures. Sensible heat fluxes are remarkably increased in winter and decreased in summer over the lake following the temperature gradient between the lake surface and the overlying atmosphere. Latent heat fluxes, moisture convergence, and water vapor mixing ratio are increased over the lake throughout the year, especially in winter. The lake also induces domain-wide decreased (increased) surface pressures and land (lake) breeze circulation in winter (summer). Simulated rainfall amounts are most increased over the lake in winter likely because of an enhanced atmospheric instability, while they slightly decrease in summer.

Enhanced NO2 and aerosol extinction observed in the tropospheric column behind lake-breeze fronts using MAX-DOAS

Abstract The lake breezes that frequently occur in Southern Ontario impact the levels of pollutants experienced by the populations in urban areas. The effects of lake breeze circulations on pollution transport and processing are not well understood. Few studies have measured the circulations’ impact on pollutants both at the surface and within the tropospheric column. In this study, pollutants in the tropospheric column (NO2 VCDs and AODs) were measured using MAX-DOAS concurrent with near-surface measurements of NOx, O3, and PM2.5 on lake breeze days in Toronto in September and October. The arrival of lake-breeze fronts (LBF) was identified using co-located meteorological data. The presence of lake breezes was confirmed using mesoscale analyses of radar, satellite and a network of meteorological stations. NO2 VCDs exhibited short-term increases of 0.8-3.4×1016 molecules cm-2 above the pre-LBF levels following the arrival of a LBF. These measurements are the first confirmation of the theorized presence of enhanced total burden of pollution within the total column behind the front within a lake-breeze circulation on multiple lake breeze days. Rapid decreases of O3 of up to 13 ppb at the arrival of the lake-breeze front were unexpected based on observed increases in O3 in other studies, but can be attributed to reduced photochemical O3 production during late summer and fall compared to mid-summer. AODs exhibited delayed enhancements compared to NO2 VCDs, appearing to be driven by enhanced humidity following the front, in addition to enhanced particle concentration. Our measurements highlight the complex 3-D structure of lake-breeze circulations.

Turbulence, Low-Level Jets, and Waves in the Tyrrhenian Coastal Zone as Shown by Sodar

The characteristics of the vertical and temporal structure of the coastal atmospheric boundary layer are variable for different sites and are often not well known. Continuous monitoring of the atmospheric boundary layer was carried out close to the Tyrrhenian Sea, near Tarquinia (Italy), in 2015–2017. A ground-based remote sensing instrument (triaxial Doppler sodar) and in situ sensors (meteorological station, ultrasonic anemometer/thermometer, and net radiometer) were used to measure vertical wind velocity profiles, the thermal structure of the atmosphere, the height of the turbulent layer, turbulent heat and momentum fluxes in the surface layer, atmospheric radiation, and precipitation. Diurnal alternation of the atmospheric stability types governed by the solar cycle coupled with local sea/land breeze circulation processes is found to be variable and is classified into several main regimes. Low-level jets (LLJ) at heights of 100–300 m above the surface with maximum wind speed in the range of 5–18 m s−1 occur in land breezes, both during the night and early in the morning. Empirical relationships between the LLJ core wind speed characteristics and those near the surface are obtained. Two separated turbulent sub-layers, both below and above the LLJ core, are often observed, with the upper layer extending up to 400–600 m. Kelvin–Helmholtz billows associated with internal gravity–shear waves occurring in these layers present opposite slopes, in correspondence with the sign of vertical wind speed gradients. Our observational results provide a basis for the further development of theoretical and modelling approaches, taking into account the wave processes occurring in the atmospheric boundary layer at the land–sea interface.

Superenhancement of Precipitation at the Center of Tropical Islands

AbstractWe identified a canonical pattern of the diurnal cycle (DC) of precipitation on tropical islands, with exceptions for small and very large islands, using an 18‐year climatology of satellite estimates. Medium‐to‐large islands receive more precipitation than the surrounding ocean with superenhancement of precipitation in their center respective to their periphery. Differential heating of the island surface generates a sea breeze front (SBF) propagating inland in the afternoon, triggering precipitation. SBF segments from different coasts meet in the island center, further invigorating precipitation. Small islands exhibit neither DC nor precipitation enhancement most likely because ventilation prevents the genesis of the land‐sea breeze circulation. On the largest islands, the SBFs decay after sunset before reaching the center; hence, the superenhancement is not significant, also precipitation lasts longer and cloud remnants delay the DC on the next day, which we attribute to the presence of high mountains.

Sodar Observation of the ABL Structure and Waves over the Black Sea Offshore Site

Sodar investigations of the breeze circulation and vertical structure of the atmospheric boundary layer (ABL) were carried out in the coastal zone of the Black Sea for ten days in June 2015. The measurements were preformed at a stationary oceanographic platform located 450 m from the southern coast of the Crimean Peninsula. Complex measurements of the ABL vertical structure were performed using the three-axis Doppler minisodar Latan-3m. Auxiliary measurements were provided by a temperature profiler and two automatic weather stations. During the campaign, the weather was mostly fair with a pronounced daily cycle. Characteristic features of breeze circulation in the studied area, primarily determined by the adjacent mountains, were revealed. Wave structures with amplitudes of up to 100 m were regularly observed by sodar over the sea surface. Various forms of Kelvin–Helmholtz billows, observed at the interface between the sea breeze and the return flow aloft, are described.

Comparative assessment of the microclimate in the «Cape Martyan» Nature Reserve according to two weather stations

A comparative assessment of the microclimate in the «Cape Martyan» Nature Reserve according to meteorological observations in meteorological station "Lavrovoe" and the climate agrometeorological station "Nikitsky sad" is given. As a result of the conducted researches homogeneity and spatio-temporal connectedness of climatic parameters within the investigated territory is established. Statistically significant differences in average and maximum values of air temperature, precipitation and relative humidity between the meteorological station "Lavrovoe" and the climate agrometeorological station "Nikitsky sad" were not revealed. This indicates to the representativeness of the data agrometeorological station for the territory of the «Cape Martyan» Nature Reserve. Statistically significant differences established for minimum air temperatures and relative humidity during the cold period should be taken into account when conducting research in the Eastern part of the Nature Reserve. It was found that the wind regime in the area of the observations by meteorological station "Lavrovoe" in the night period is characterized by air drainage phenomena and the predominance of breeze circulation in the warm season, which largely determine the microclimatic differences between observed meteorological values by station "Lavrovoe" and by station "Nikitsky sad", especially when the radiation weather type.

Numerical Simulation of the Irrigation Effects on Surface Fluxes and Local Climate in Typical Mountain‐Oasis‐Desert Systems in the Central Asia Arid Area

AbstractIn this study, the Weather Research and Forecasting model was coupled with an improved Noah land surface model (WRF‐Noah) where dynamic flood and drip irrigation processes were implemented firstly. We simulated the different irrigation effects on surface water‐heat processes in a typical mountain‐oasis‐desert system in Central Asia for both wet and drought years, respectively, using the modified WRF‐Noah. The modified WRF‐Noah model can dynamically generate amounts of irrigation in agreement with actual values. The statistically significant decrease in the root mean square error and increase in the Pearson correlation coefficient for the 2‐m temperature (T2), relative humidity (RH), latent heat flux (LE), and precipitation suggest that the modified WRF‐Noah model was improved by implementing irrigation processes. During the irrigation season, flood and drip irrigation decreased the average sensible heat flux by −80.69 and −50.50 W/m2 and T2 by 1.09 and 0.82 °C over the irrigated area and increased LE by 88.47 and 66.70 W/m2 and RH by 6.23% and 4.65%, respectively. Throughout the domain, flood irrigation had equivalent or slightly weaker effects on near‐surface temperature and humidity due to the smaller irrigated area. Both flood and drip irrigation increased precipitation throughout the domain, especially in the mountainous area, thereby accelerating the hydrological cycle in the mountain‐oasis‐desert system. The local oasis breeze circulation that plays a role in maintaining the oasis stability is still counteracted by the dominant background circulation even with irrigation processes. Thus, more effort should be exerted to maintain the future sustainability of the oasis.

Impact of Sea Breeze Circulation on the Transport of Ship Emissions in Tangshan Port, China

A sea breeze is a local circulation that occurs in coastal regions from the poles to the equator. The adverse influence of ship emissions on air quality in coastal areas may be aggravated by the onshore flow of sea breeze circulation. However, our knowledge regarding the evolution of ship-emitted pollutants during a specific sea breeze episode is still limited. To address this knowledge gap, this study investigated the evolution of ship emissions during a sea breeze episode that occurred on 29 June, 2014 in Tangshan port in China by employing the WRF/Chem model. NO2, one of the primary pollutants emitted by ships, was selected as the target pollutant for investigation. The results indicate that the ground level NO2 concentration was considerably affected by sea breeze circulation. Although the onset of the sea breeze was delayed until nearly midday due to offshore synoptic winds, ship-emitted NO2 was transported to more than 100 km inland with the penetration of the sea breeze. Further investigation found that the averaged concentration of ship-contributed NO2 during the episode showed an evident downward trend as the distance from the coastline increased. Vertically, the shallow atmospheric boundary layer (ABL) on the sea limited the vertical dispersion of ship emissions, and the pollutant was transported shoreward by the sea breeze within this shallow ABL. The height of the ABLs is lowered in coastal regions due to the cooling effect of sea breezes which brings the cool marine air to the hot land surface. Ship-contributed NO2 was mostly trapped in the shallow ABL; thereby, its concentration increased.

Numerical simulation of breeze circulation in Crimea using WRF-ARW model

Breeze circulation is an important atmospheric process that affects the weather and climate of coastal regions. Crimea is one of such regions. One of the methods of breeze research is numerical simulation, which has been quite successfully used to obtain information on breeze circulation in various geographical regions. The purpose of this work is to describe the regional features of sea breeze in Crimea, specifically, a breeze circulation near the Crimean Mountains. We use an array of satellite images and data of global operational analysis, NCEP GDAS, to choose a day with a pronounced breeze. A numerical experiment is performed for the day using a mesoscale model, WRF-ARW. Based on the results of the numerical simulation, the structure of the sea breeze circulation in Crimea is described. Some classical elements of the breeze characteristics of the flat part of Crimea are observed. A unique phenomenon of collision of breeze gravity currents has been revealed. It is a characteristic of the rather small land areas. Much attention is given to the features of breeze in the mountains associated with the complex topography.

Sensitivity of Ozone Production to NOx and VOC Along the Lake Michigan Coastline

AbstractWe report on the sensitivity of enhanced ozone (O3) production, observed during lake breeze circulation along the coastline of Lake Michigan, to the concentrations of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs). We assess the sensitivity of O3 production to NOx and VOC on a high O3 day during the Lake Michigan Ozone Study 2017 using an observationally constrained chemical box model that implements the Master Chemical Mechanism (MCM v3.3.1) and recent emission inventories for NOx and VOCs. The Master Chemical Mechanism model is coupled to a backward air mass trajectory analysis from a ground supersite in Zion, IL, where an extensive series of measurements of O3 precursors and their oxidation products, including hydrogen peroxide (H2O2), nitric acid (HNO3), and particulate nitrates (NO3−) serve as model constraints. We evaluate the chemical evolution of the Chicago‐Gary urban plume as it advects over Lake Michigan and demonstrate how modeled indicators of VOC‐ versus NOx‐sensitive regimes can be constrained by measurements at the trajectory endpoint. Using the modeled ratio of the instantaneous H2O2 and HNO3 production rates (PH2O2/PHNO3), we suggest that O3 production over the urban source region is strongly VOC sensitive and progresses towards a more NOx‐sensitive regime as the plume advects north along the Lake Michigan coastline on this day. We also demonstrate that ground‐based measurements of the mean concentration ratio of H2O2 to HNO3 describe the sensitivity of O3 production to VOC and NOx as the integral of chemical production along the plume path.

Influences of Lake Malawi on the spatial and diurnal variability of local precipitation

Abstract. We investigate how the intensity and spatial distribution of precipitation vary around Lake Malawi on a diurnal timescale, which can be valuable information for water resource management in tropical south-eastern African nations. Using a state-of-the-art satellite product and regional atmospheric model, the well-defined diurnal cycle is detected around Lake Malawi with harmonic and principle component analyses: the precipitation is intense during midnight to morning over Lake Malawi and the precipitation peaks in the daytime over the surrounding area. This diurnal cycle in the precipitation around the lake is associated with the lake–land breeze circulation. Comparisons between the benchmark simulation and an idealized simulation in which Lake Malawi is removed reveal that the diurnal variations in precipitation are substantially amplified by the presence of Lake Malawi. This is most evident over the lake and surrounding coastal regions. Lake Malawi also enhances the lake–land breeze circulation; the nocturnal lakeward land breeze generates surface convergence effectively and precipitation intensifies over the lake. Conversely, the daytime landward lake breeze generates the intense divergence over the lake and precipitation is strongly depressed over the lake. The lake–land breeze and the background vapour enriched by Lake Malawi drive primarily a diurnal variation in the surface moisture flux divergence/convergence over the lake and surrounding area which contributes to the diurnal cycle of precipitation in this region.

Bay Breeze and Sea Breeze Circulation Impacts on the Planetary Boundary Layer and Air Quality From an Observed and Modeled DISCOVER‐AQ Texas Case Study

AbstractThe role of the sea/bay breeze in the planetary boundary layer evolution and air quality during a high ozone event day in the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER‐AQ) Texas 2013 campaign was examined. Data from surface air quality monitoring network stations, airborne lidar data, and additional ground‐based lidar instrumentation deployed during the campaign allowed for a unique three‐dimensional spatial and temporal study of the progression of both meteorological and air quality conditions in the Houston‐Galveston regions on 25 September 2013. The Weather Research and Forecasting model coupled with Chemistry model was used to examine the relationship of the land and bay/sea breeze circulations and its influence on air quality during the case study. Comparisons between observations and simulations revealed the largest discrepancies near the Galveston Bay shore areas where the highly localized ozone concentrations were observed and were linked to the strength and timing of the bay/sea breeze progression. Additionally, results indicate vertical downmixing from the remnants of the nighttime residual layer during morning hours into the convective boundary layer and from the lofted offshore return flow into the subjacent bay breeze flow.

Simulation of Sea Breeze Events in Gulf of Jakarta under Different Synoptic Condition: An Application of WRF Model

The behaviour of the sea breeze developing along the Gulf of Jakarta during days with different synoptic condition is examined using observational data and simulations from the Weather Research and Forecasting (WRF). An objective and systematic selection method is used to detect sea breeze days from observational data. The simulation used three nested grids at 27, 9 and 3 km resolution covering Gulf of Jakarta and its joining region for sea breeze event at November 22th, 2016 which formed under offshore large-scale ambient wind, January 20th, 2017 which formed under westerly large-scale ambient wind, and August 10th, 2017 which formed under easterly large-scale ambient wind. Results show that the development of sea breeze circulation under offshore ambient wind produced lower 10-m wind speed simulation, while sea breeze conditions under westerly large-scale ambient wind are associated with highest surface wind speeds reaching 9.5 ms-1 in Gulf of Jakarta. Sea breeze simulation also indicates the formation of calm zone which is 22 - 56 km away from the Jakarta Gulf coastline. Model also shows the formation of thermal internal boundary layer that are about 300-700 m near the coast gradually merged with the mixing layer inland. Performance of WRF on the simulated circulation is studied by conducting value of correlation, RMSE, and MBE. Overall, model simulation agrees fairly well with the observations taken at a near-surface meteorological station.

GPS-based precipitable water vapour retrieval and variability using measured and global reanalysis data in the coastal regions of China

ABSTRACT The atmospheric water vapour is an important indicator of the climate state and evolution, and also the key parameter affecting the hydrological cycle, atmospheric convection, and the weather. This study validated the accuracy of surface pressure and temperature data interpolated from European Centre for Medium-Range Weather Forecasts (ECMWF) Interim ReAnalysis (ERA-Interim) and ECMWF 5th ReAnalysis (ERA5) datasets, and evaluated the performance of the interpolation meteorological data for precipitable water vapour (PWV) retrieval using the measured meteorological data and Global Positioning System (GPS) data of the year 2014 obtained from 25 stations of the Chinese Coastal GPS Observation Network. We then analysed the temporal and spatial distribution of water vapour in the coastal regions of China using a 3-year GPS PWV time series calculated with the interpolated reanalysis meteorological data at 25 stations from 2014 to 2016. Evaluation of the reanalysis meteorological data results showed that the accuracies of the interpolated pressure and temperature data from ERA5 were slightly superior than those from ERA-Interim. The root-mean-square errors (RMSEs) of the surface temperature and pressure interpolated from two reanalysis datasets were less than 2.4 K and 1.6 hPa, respectively. Data based on GPS PWV products that used interpolated parameters were very close to those of meteorological observations, with biases within ±0.4 mm and RMSEs below 0.5 mm in most areas; these data also strongly agreed with radiosonde observations. However, the interpolated meteorological data from reanalysis datasets could not reflect the true change during typhoon events, which could not be used in GPS PWV retrieval. The analysis of the temporal and spatial distribution showed that the distribution of water vapour was mainly affected by latitude, land-sea distribution, and water vapour advection. The variations in water vapour were mainly seasonal with the highest PWV occurring in the summer and the lowest always occurring in the winter. Significant diurnal variations of water vapour varied with season and latitude, with an amplitude of about 0.9–3.5 mm; the peak value occurred in the afternoon or early morning, and was affected by surface evaporation, large-scale land–sea breeze circulation, and valley-wind circulation.