Analysis and Case Study of Duststorms in the Beijing Area

The physical processes in the Yellow Sea

A climatological and numerical study of “Karakkaze,” a type of local wind in Japan, was conducted. First, winter days under a winter-type synoptic pressure pattern with daily minimum relative humidity of less than 40% were classified according to strong wind (wind speed ≥ 9 ms-1, Karakkaze day), medium wind (6 ms-1 ≤ wind speed -1), and weak wind (wind speed -1). Secondly, the spatial patterns of the surface wind in each category are confirmed by the Japan Meteorological Agency (JMA)-Automated Meteorological Data Acquisition System (AMeDAS) observation data. In addition, we compared the boundary-layer wind of the three categories using wind speed data from the observation tower of the Meteorological Research Institute (MRI) in Tsukuba and from the JMA wind profiler in Kumagaya. Finally, we performed one-dimensional numerical experiments using a column Planetary Boundary Layer (PBL) model to evaluate the impact of solar radiation and upper-level wind on the formation of the Karakkaze. The results are summarized as follows. On the strong-wind days, strong northwesterly winds appear in the area along the Arakawa River and the Tonegawa River from Maebashi. The surface wind speed has a clear diurnal variation with a peak in the early afternoon. Such a diurnal variation is observed up to a 200 m level, but this diurnal pattern nearly reverses itself between 200 m and 400 m levels. On weak-wind days, the diurnal variation pattern is similar to that in other two categories, but the reversed pattern appears at a 100 m level, not at a 200 m level. Stronger surface winds appear under a clearer winter-type pressure pattern. The correlation coefficient is 0.632 between the daily maximum surface wind speed and the daily mean wind speed at a height of 2759 m, whereas the correlation is 0.284 between the surface wind speed and daily sunshine duration, which, in a previous study, was suggested to be the most significant factor. Numerical experiments indicate that a large amount of solar radiation is a necessary condition for a strong daytime wind, but this is not a sufficient explanation for the difference in the surface wind speed between weak and strong-wind days.

The seasonal variability of strong afternoon winds in a northern Himalayan valley and their relationship with the synoptic circulation were examined using in situ meteorological data from March 2006 to February 2007 and numerical simulations. Meteorological observations were focused on the lower Rongbuk valley, on the north side of the Himalayas (4270 m MSL), where a wind profile radar was available. In the monsoon season (21 May–4 October), the strong afternoon wind was southeasterly, whereas it was southwesterly in the nonmonsoon season. Numerical simulations were performed using the Weather Research and Forecasting Model to investigate the mechanism causing these afternoon strong winds. The study found that during the nonmonsoon season the strong winds are produced by downward momentum transport from the westerly winds aloft, whereas those during the monsoon season are driven by the inflow into the Arun Valley east of Mount Everest. The air in the Arun Valley was found to be colder than that of the surroundings during the daytime, and there was a horizontal pressure gradient from the Arun Valley to Qomolangma Station (QOMS), China Academy of Sciences, at the 5200-m level. This explains the formation of the strong afternoon southeasterly wind over QOMS in the monsoon season. In the nonmonsoon season, the colder air from Arun Valley is confined below the ridge by westerly winds associated with the subtropical jet.

In the present study, an intense unseasonal dust storm has been analyzed during third week of March 2012 from multi satellite datasets and from surface measurements over National Capital Region (NCR), Delhi. The intrusion of dust over study region has increased the MODIS Aerosol Optical Depth at 550 nm more than 1.0 whereas significant decrease in Angstrom Exponent (α) has been observed . Very high UV aerosol Index (> 2) over study location indicates the presence of UV absorbing aerosols . Fire activities are found to be negligible over the source region confirming the effect of dust storm. Strong southwesterly winds prevailed over northern Arabian Sea which trans ported the dust plume across the oceanic region towards Indian capital region. In-situ measurements of PM 2.5 and PM10, obtained from CPCB observational site over the IGI airport, NCR Delhi, showed abrupt increase on 20, 21 March. Eight hourly average concentration of the particulate matters less than 10 μm (PM10) is found to be ~990 μg/m 3 and particulate matters less than 2.5 μm (PM2.5) is found to be ~900 μg/m 3 over IGI Airport, NCR Delhi. These values are remarkably higher as compared to the daily National Ambient Air Quality Standards (NAAQS) i.e. 100 μg/m 3 and 60 μg/m 3 for PM10 and PM2.5 respectively. In addition, Vertical distribution of dust has been examined using CALIPSO observation. The layer of dust is found to be trapped within lower 3 km in altitude. The Potential Source Contribution Function (PSCF) modeling has been carried out to identify the specific source locations.

Abstract. Storm Xaver on 5–6 December 2013 was a serious winter storm in northern Europe with important impacts on societal and energy infrastructure. The storm's low pressure centre passed eastward north of Scotland, across the North Sea and southern Scandinavia, and into the Baltic region. The trajectory resulted in strong northwest winds and a cold air outbreak southward across the North Sea. The resultant convection system was associated with powerful wind gusts and freezing precipitation that impacted the UK, Belgium, the Netherlands, Germany, Poland, Denmark, Sweden, and Norway. The storm caused coastal flooding that was comparable with the most serious North Sea surge events of the 20th century. The primary impact for energy meteorology was a large scale electrical power loss in the northern part of the British Isles, Sweden, Poland, and parts of Germany. Petroleum production was reduced as offshore platforms were evacuated ahead of the storm. For wind energy, a number of onshore turbines were damaged by the gust field. Other societal impacts included travel and transport interruptions, building damage, forest damage, and coastal erosion. Because of the high water levels and sea state in the North Sea, the storm was important for offshore wind energy. The wind energy research tower FINO1 sustained unexpected damage during the storm, similar to previous wave strikes during Storm Britta (2006) and Storm Tilo (2007). A closer analysis is made of the tide gauge records across the North Sea to understand the progression of the storm surge and identify high amplitude, short-period features that may be linked to unusual seiches, meteotsunamis, or infragravity waves. Similar to previous storms, there is an indication that large infragravity waves during Storm Xaver may have had an impact on North Sea transport and energy infrastructure as well as coastal erosion. The review of information from different sources permits the met-ocean conditions and resultant societal/energy impacts to be related in time and space.

A numerical simulation of the strong southeasterly (SE) wind in Yamagata, Japan on August 30, 2004, is examined and compared to the Coherent Doppler Lidar (CDL) observation. Three-dimensional numerical simulations were performed using a non-hydrostatic meso-scale model developed by the Japan Meteorological Agency. The sensitivity of the numerical simulation was examined with respect to the resolution of the horizontal and vertical grid, surface roughness, and ground surface temperature. For the case of a 1-km grid with 85 vertical layers including realistic surface settings, the observed characteristics of Kiyokawa-dashi were well reproduced: the strong SE wind (10 m s -1 ) was extremely low, about 0.1-0.5 km AGL, and the maximum wind speed over 12 m s -1 was observed at 0.1-0.2 km, AGL, under the low-level stable layer. Strong winds appeared at the foot of the final lee slope facing the Shonai Plain and 1 km south of the valley; this result was in good agreement with the CDL observation. On the basis of the stream line analysis, Kiyokawa-dashi was strongly affected by the upper SE wind, i.e., upper air on the eastern side of the mountains blew down to the middle and lower layer on the western side. The strongest wind field located 1 km south of the valley was affected by the mountain at the southwestern end of the valley. It was observed from the sensitivity experiments that the height of the jet-like flow was found to be closely related to the low-level stable layer, and the critical layer was not very important in reinforcing the low-level SE wind. This case of Kiyokawa-dashi was explained on the basis of the hydraulic theory.

Water-soluble brown carbon in atmospheric aerosols along the transport pathway of Asian dust: Optical properties, chemical compositions, and potential sources

Aerosol vertical distribution and optical properties of different pollution events in Beijing in autumn 2017

The eruption of the Mount Asama volcano on 16 September 2004 produced an ash cloud and led to ashfall in the Tokyo metropolitan area that lies on the Kanto Plain. Satellite images showed the ash cloud drifting toward the south in the morning but to the southeast in the afternoon. An aerosol lidar and a ceilometer, installed in the metropolitan area, continuously observed the southeastward-transported ash particles passing at altitudes of 2.6–4.5 km above mean sea level (MSL) in the nighttime. Results of meteorological analyses and numerical experiments showed that the south-to-southeasterly sea breezes and valley winds prevailed at altitudes below 1.5 km MSL over the Kanto Plain in the afternoon and the compensatory return flow (CRF) was formed aloft at altitudes of 1.5–4.5 km MSL as strong northwesterly winds, which were encouraged by a synoptic wind. The numerical experiments also showed that the direction of the ash transport turned from the south to the southeast following the formation of the northwesterly CRF. This demonstrates that the daytime ash transport was influenced by the CRF. The nocturnal ash transport, however, depended on the intensified synoptic wind. Thus, in addition to synoptic winds, the large-scale local wind circulation prevailing over the Kanto Plain can determine the direction of ash transport originating from the Mount Asama volcano and increase the possibility of ashfall in the Tokyo metropolitan area.

The preserved carbonate record in Holocene sediments of the Alfonso and Pescadero basins, Gulf of California, Mexico

The acoustic Doppler current profiler, temperature, salinity and density data set were recorded monthly over the course of a year in a tropical coral reef system to elucidate the effects of abrupt bathymetric changes on current variability and surface temperature over time. A minimum of five transect repetitions were performed during one diurnal tidal cycle each month during the year 2008. According to the empirical orthogonal functions, the dominant terms were advection and friction due to the shallowness of the system and the relatively short continental shelf located in front of the Port of Veracruz (Mexico). The data showed the dominance of the northwest-southeast current velocity components (parallel to the coast) attributed to the winds. The southeastward current velocity was the dominant component throughout the year, followed by the northwestward current velocity component. The data suggested that coral reefs produce current rectification near the shallow reef areas (1 m depth). No correlation existed between surface temperature and the chlorophyll-a levels throughout the year. Residual current velocities throughout the year never reached more than 50 cm –1 during the sampling periods, and the surface temperature varied from 21 to 30°C, with the highest temperature being observed near the coast and reefs. Finally there was a direct correlation of the northeasterly and strong northwesterly winds with the well-mixed cold-salty water column in the reef area.

The China National Climate Center and National Centers for Environmental Prediction data were used in this work. Using the knowledge of synoptic principles and synoptic analysis, the rain and snow weather process in the middle and east of China from December 28 to 30, 2020 was analyzed. The results show that: 1) This weather process was a large-scale precipitation process. Affected by the cold wave, the temperature drops sharply, and the temperature in many places dropped below the extreme value, accompanied by strong winds. 2) This process is mainly caused by the eastward movement of the upper-level trough leading the cold air southward to intersect with the warm and wet air, and the shear thread in the lower layer cooperates. 3) The cold air is from the ocean east of Novaya Zemlya. 4) From the evolution trend of 500 hPa geopotential height field and ground pressure field, the cold surge process belongs to the type of transverse trough to vertical.

In March 2004, a large‐scale, strong and persistent outbreak of Saharan dust on to the adjacent tropical and subtropical Atlantic Ocean was observed in satellite imagery. Surface observations show that the event was accompanied by unusual weather conditions across large parts of North Africa including low temperatures and strong winds over the Sahara, extreme precipitation in Libya and a heat wave on the Guinea coast. The dust outbreak was associated with an unseasonally southerly position of the Intertropical Convergence Zone and a delayed northward progression of the African monsoon.The dust front was initially related to a density current caused by strong evaporational cooling along a precipitating cloud‐band that penetrated into the northern Sahara ahead of an upper‐level trough. At later stages, massive upper‐level convergence, sinking, low‐level divergence and an explosive anticyclogenesis over northwest Africa caused strong northerly flow and a quick spreading of the dust front to the south and west. The strong pressure gradients over North Africa were further enhanced by the formation of a cyclone ahead of the upper‐trough. A dynamical analysis based on potential‐vorticity (PV) theory provides new insights into the generation of North African harmattan surges. Using a PV inversion, it is shown that the explosive anticyclogenesis was caused largely by unbalanced dynamics related to the density current, divergent outflow from the precipitation over Libya and inertial instability in the entrance region of the strong subtropical jet and tropical plume along the eastern side of the upper trough. These processes enhanced the effects of the balanced advection of negative vorticity and cold air by the large‐scale wave. Moreover, we show the importance of an explosive cyclogenesis event over the central North Atlantic for the amplification of the downstream wave associated with the penetration of the cold front into North Africa. Copyright © 2006 Royal Meteorological Society.

The nonhydrostatic multiscale model on the B grid (NMMB) was employed to forecast an episode of intense local Kosava wind in northeast Serbia. Kosava, a vigorously turbulent local wind, originates from the east or southeast near the Danube's "Iron Gate," moves westward over Belgrade, and then extends northward into the regions of Romania and Hungary. Typically attributed to a jet-effect wind within the narrow gorge of the "Iron Gate," it can reach maximum speeds exceeding 30 m/s. The NMMB model, with a horizontal resolution of 1.2 km, was utilized for the 2019 Kosava episode forecast. The high resolution, that surpasses the typical standards in numerical prediction models used by national meteorological services and other centers, can be crucial for accurately predicting strong wind gusts and capturing the specific dynamics and characteristics of the wind associated with the narrow gorge. The NMMB model results are compared with measured wind data and the results from models with lower resolutions.

Dust storm episodes at the aerodromes in the Asian part of Russia / Ivanova A.R., Skriptunova E.N., Komasko N.I., Zavialova A.A.// Hydrometeorological Research and Forecasting, 2021, no. 2 (380), pp. 20-42. According to 2001-2020 METAR data, episodes of dust storms at 26 international aerodromes in the Asian Russia causing poor visibility are studied. The conditions for issuing reports on dust storms, their correspondence to the definition of a dust storm are discussed. It was found that out of 337 reports describing dust transport by strong wind, only 7 episodes registered at the aerodromes of Irkutsk, Abakan, Omsk, and Blagoveshchensk corresponded to the classical definition. The others detected at 15 of 26 aerodromes may be defined as “dust events” – the episodes of dust transfer causing the nonessential visibility reduction. The seasonal variation in such episodes and its connection with changes in visibility are studied. The characteristics of dusty air masses and the direction of their advection are given. Keywords: dust storm, dust events, aerodromes of Asian Russia, seasonal variation, trajectory analysis