Sponsored by Chinese Meteorological Society (CMS)
ISSN 0577-6619 CN 11-2006/P
6 issues per year
Current Issue: Issue 06, 2016
The awards and honors that Acta Meteor. Sinica has received in recent years include: (1) Top 5% Chinese Academic Journals with the Highest International Impact 2012－2014, (2) Top 100 S&T Journals of China 2013, (3) China Government Award for Journals--Nominees Award 2013, (4) Outstanding S&T Journals of China 2008, 2011, 2014, and (5)Elite S&T Journal Support Program of the China Association for Science and Technology (CAST) for 2015-2017. AMS publishes the latest achievements and developments in the field of atmospheric sciences and related disciplines such as geophysics and environmental sciences. AMS covers a broad range of topics such as: global climate change, monsoons, Tibetan Plateau meteorology, earth system modeling, atmospheric chemistry and environment, radar and satellite meteorology, atmospheric sounding and remote sensing, boundary layer meteorology, aerosols, clouds, and air pollution, weather modification, agricultural and forest meteorology, and so on.
Multi-scale characteristics of atmospheric circulation related to short-time strong rainfall events in Beijing
Vol 74,No. 06
Auto-weather station observations and ERA-Interim reanalysis data are used to investigate large and meso-scale circulation characteristics related to short-time strong rainfall events over Beijing during June to August from 2007 to 2014. This is done by classifying large-scale synoptic circulations. The results show that: (1) according to their occurrence frequencies, weather systems generally are able to be classified into four synoptic types for short-time strong rainfall events, i.e. the interaction between subtropical high and western trough (Ⅰ), small trough moving along the westerly stream (Ⅱ), cold vortex in northeastern China (Ⅲ), and low-pressure vortex or inverted trough over Huanghuai Plain (Ⅳ). Except that water vapor comes from Bohai Sea and Yellow Sea for Type Ⅲ, for the other three patterns the water vapor are related to remote supplies from the South China Sea and the East China Sea; (2) temporal and spatial distributions of short-time strong rainfall are different with different weather systems: the rainfall distribution is along the southeast-to-northwest mountain range extending from the southeastern plain across the urban area to northwestern mountains under Type Ⅳ. However, the rainfall distribution under the other three types is generally along the southwest-to-northeast mountain range (also along the topography in Beijing area). In particular, three high frequency centers are located in front of the southwestern and northeastern mountains and central urban area respectively. Looking at the time series, it is found that short-time strong rainfall mainly occurs in the afternoon for Type Ⅲ, from dusk till mid-night for TypeⅠ, and at night for Type Ⅱ and Ⅳ; (3) looking at the meso-scale characteristics, convections over mountainous area in Beijing are often triggered first by cold air at the lower level in western and northern Beijing, followed by organized thunderstorm highs. The cold pool outflow from the thunderstorm high and the warm moist airflow from the southerly winds in front of the mountains converge, further intensifying convections; for Type Ⅱ, the southeasterly winds at the boundary layer are blocked by the opography in front of the northwestern mountain over Beijing. The flow bifurcates around the two sides of the mountains. The southwestern branch generates a cyclonic circulation and triggers convective weather over western urban area; the northern branch generates a topography-induced convergence line in front of the mountain, and vertical motion strengthens at the nighttime because the southern component of the southeasterly winds enhances obviously, and triggers convective weather in front of northeastern mountains. As a result, two separate high-frequency rainfall centers characterized by nighttime rainfall appear. For Type Ⅲ, cold air invades from the north or west of Beijing, and meet with easterly winds at the lower layer in front of mountain, leading to convective weather in the afternoon. For type Ⅳ, the easterly flow at the top of the low vortex over Huanghuai Plains is lifted by the topography in front of western mountains, which triggers convections. Meso-scale cyclonic circulation gradually forms, resulting in short-time strong rainfall.
Statistical characteristics of the tropical cyclone activities over the Northwest Pacific and the Bay of Bengal during the Asian summer monsoon onset
Vol 74,No. 06
Climatologically, the Asian summer monsoon (ASM) onset first occurs at the Bay of Bengal (BOB) and then spreads to the South China Sea (SCS) and Indian subcontinent. The onset usually lasts for about one month. The summer monsoon onsets in different areas show apparent inter-annual variations. The relationship between the tropical cyclone (storm) over the Northwest Pacific and BOB during the ASM onset is analyzed using the datasets from 1951 to 2010. Results show that there are tropical storm activities over the BOB during the BOB summer monsoon onset in 36 years. The earlier onset years are coincident with years of higher probability of up to 80% for tropical storm occurrence. For the three types of the BOB summer monsoon onset (early, normal and late), the high frequency of the BOB tropical storm appears several days before the BOB summer monsoon onset, and the tropical cyclones over the Northwest Pacific become active before the high frequency occurrence of the BOB tropical storm. For the early BOB summer monsoon onset years, tropical cyclones occur in about 40%–50% of the years over the Northwest Pacific, and the tropical cyclones usually occur over the SCS and near the Philippines in the second pentad of April. When the BOB summer monsoon onset is normal, the tropical cyclones usually occur to the east of the Philippines in the fourth pentad of April. When the BOB summer monsoon onset is late, the tropical cyclones most likely occur over the Pacific, which is the easternmost among the areas of tropical cyclone occurrence corresponding to the three types of monsoon onset in early May. During the SCS summer monsoon onsets from 1951 to 2010, there are tropical cyclone activities over the northwestern Pacific in 29 years. In the early and normal SCS summer monsoon onset years, the frequency of tropical cyclone activities is high. The tropical cyclone over the northwestern Pacific usually becomes active on the SCS summer monsoon onset date or several days later. That is, the tropical cyclone activity over the Northwest Pacific intensifies first before the Asian summer monsoon onset, followed by the enhanced BOB tropical storm activity and the Asian summer monsoon onset. In early and normal onset years of the Asian summer monsoon, the tropical cyclone activity over the northwestern Pacific intensifies again after the BOB summer monsoon onset, and the SCS summer monsoon breaks out subsequently.
Vol 74,No. 06
The charge structure and formation in Typhoon Molave (2009) before and after its landfall and during its decaying stage are investigated using satellite observations and lightning detection data as well as a mesoscale simulation. Results show that Molave was intensifying prior to landfall with a well-defined eye and relatively high-frequency lightning activities in the eyewall. Convections near the eyewall exhibited a positive tripole charge structure with a negative charge region located between the levels of −25 ºC and −10 ºC sandwiched by two positive charge regions. However, the charge structure of the convections became a negative bipole with a negative charge in the middle and a positive charge at the bottom of the convective clouds after Molave reached its maximum intensity. The charge structure in the eyewall convections was closely associated with the typhoon intensity, but not directly correlated with the landfall process. The outer spiral rainbands displayed a positive tripole charge or apositive bipole charge in different stages of Molave. Previous studies suggested that the outer rainbands of a typhoon only feature a positive bipole charge structure. The positive tripole charge structure in Molave formed with different mechanisms: One mechanism resembled that in the eyewall, and the other mechanism was related to a positive charge region composed of hails and a positive bipole region composed of graupels and ice crystals in the upper level, which formed a positive tripole charge structure. During the decaying stage of Molave, weak convections were mainly featured by a negative bipole similar to that in the terrestrial thunderstorms in dissipative stage. In addition, different charge structures and corresponding convection intensity are also discussed in this paper.
Vol 74,No. 06
This study presents the climatology of anticyclones in Eurasia during the winter based on the sea level pressure and 10 m winds extracted from the NCEP/NCAR reanalysis data in the period of 1948–2013. Results show that the main sources of anticyclones are: The Mongolian Plateau, Iran and its neighboring regions, the Mediterranean coast, central Siberia, north and west of the Baltic Sea and northeastern Russia. The Mongolian Plateau and Iran regions are the main sources of strong anticyclone events. Areas of large frequency of anticyclone occurrence also correspond to centers of high anticyclogenesis. Major areas of active anticyclones correspond to areas of large meridional gradients of temperature in the lower troposphere (850 hPa) and in the front of the upper-level ridge. There is a close relationship between the intensity and displacement of the anticyclones except for those originating from Mongolian Plateau and northeastern Russia. 44.2% of the total anticyclone events last 1–2 d, and only 3.2% last for more than 7 d. Strong anticyclone events are more likely to last longer than the weak ones.
Sensitivity study of vertical resolution in WRF numerical simulation for sea fog over the Yellow Sea
Vol 74,No. 06
The performance and sensitivity of the Weather Research and Forecasting (WRF) model to different vertical resolutions for simulating the Yellow Sea fog are studied. Numerical experiments with combinations of three vertical resolutions (35η, 44η and 63η) and two planetary boundary layer schemes (YSU, MYNN) are designed and conducted for the simulation of 10 sea fog cases. The sensitivity of fog-area and fog-top height to vertical resolution is statistically analyzed, and a typical case is investigated in detail to reveal the effects of fog-top long-wave radiation cooling and turbulence inside the fog. The statistical results show that: (1) the fog-area simulation is significantly improved with increases in vertical resolution, and the model also performs better in fog-area simulations for those cases that have large fog height differences between the experiments with different vertical resolutions; (2) the YSU scheme is more sensitive than the MYNN scheme. Compared to the 35η-experiments, the averaged probability of detection (POD) and equitable threat score (ETS) in the 44η-experiments have improved by 13.29% and 10.22%, respectively. Detailed analysis of the typical case indicates that a reliable modeling of fog-top long-wave radiation cooling and turbulence inside the fog strongly depends on vertical resolution. It can be outlined as: (1) a coarse vertical resolution with a weak turbulence intensity leads to the failure of simulation; (2) apositive feedback—"increased cloud liquid water→enhancing long-wave radiation→strengthening cooling→cloud liquid water increased" —forms near the fog top, and fine vertical resolution is more helpful to maintain and strengthen this feedback loop than the coarse resolution; (3) only the simulations with fine vertical resolution can capture the downward buoyancy turbulence that is produced by fog-top long-wave radiation cooling. The intensity of the buoyancy turbulence is comparable to that of the shear turbulence near the sea surface, and it results in the phenomenon that sea surface temperature is higher than air temperature, which is often observed during sea fog occurrence.
Vol 74,No. 06
Based on analysis of the aerosol hygroscopic parameter (κ) and the aerosol ionic components observed in July 2014 in Huangshan Mountain, characteristics of the multi-size aerosol hygroscopic parameter (κ) were investigated and a parameterization scheme of κ was developed. Results indicate that the sampling site was mainly affected by southwesterly, northerly and southeasterly flows during the summer. The value of κ varies from 0.2 to 0.48, and it first increases and then decreases with the increase of the aerosol particle size. When the aerosol particle size is within the highly hygroscopic range of 0.15 to 1.1 μm, the κ value is greater than 0.3; when the aerosol particle size is within the range of less hygroscopic, the value of κ is smaller than 0.3. For those aerosol particles with a diameter Dp < 1.1 μm, the highest value of κ appears when influenced by southwesterly flow, and the lowest value appears when southeasterly flow is prevalent. The opposite is true for aerosol particles with a diameter Dp > 1.1 μm. The main water-soluble chemical compositions of aerosol particles are NH4+, SO42−and WSOC, which affect the hygroscopicity of aerosol particles with a size smaller than 1.1 μm. NH4+, SO42−, NO3−, WSOC and Ca2+ are the main soluble chemical compositions that affect the hygroscopicity of aerosol particles with a size greater than 1.1μm. The parametric equation of κ for aerosol particles with a size less than 1.1 μm is κreg = 0.12 + 0.45fNH4+ + 0.63fSO42− + 0.18fWSOC, and the equation for aerosol particles with a size greater than 1.1 μm is κreg = 0.01 + 0.78fNH4+ + 0.76fNO3− + 0.8fSO42− – 0.28fCa2+ + 0.14fWSOC.( f is the mass percentage of the corresponding component). Both equations can well predict the values of κ for multi-size aerosol particles, and the deviations of predicted values are less than 30%. The forecast values of κreg are highly correlated with calculated values of κ, and the correlation passes the significance test at the 99% confidence level.
Vol 74,No. 06
Analytical solutions of stationary waves forced by sensible heating in a linear quasi-geostrophic model are obtained; effects of the basic flow, the Newton cooling and surface friction on the amplitude and phase of stationary waves are discussed. Results show that when the basic flow is easterly, the stationary waves exhibit a baroclinic structure in the vertical direction and the amplitude in the surface is stronger than in the middle and upper layer. When the basic flow is westerly, the waves propagate upward. In the lower layer, the cyclone (anticyclone) lies mainly to the west (east) of the heating center when the basic flow is easterly, and the cyclone (anticyclone) is located to the east (west) of the heating center when the basic flow is westerly. In the middle and upper layer, however, the opposite is true. It is found that the effects of the basic flow on the amplitude and phase of the waves are symmetric, which is different from the effects of condensation latent heating. The results also show that the Newton cooling has an important influence on the stationary waves especially when the basic flow is very weak. In a static atmosphere, the inviscid solution, i.e., the Sverdrup solution forced by sensible heating does not exist. When the Newton cooling is considered, the cyclone is forced in the lower layer and the anticyclone is forced in the middle and upper layers within the area influenced by the sensible heating, and the center of the cyclone is located slightly to the west of the heating center. In a non-static atmosphere, the Newton cooling makes the centers of the surface systems move upwind. As a dissipative term, it weakens the system in both the lower and upper layers, which is different from the effects of surface friction. The surface friction always weakens the system in the lower layer and intensifies the system in the upper layer.
Vol 74,No. 06
Using the level 2 CloudSat-CALIPSO product 2B-CLDCLASS-LIDAR from January 2007 to December 2010, the occurrence frequencies of convective clouds over China and its surrounding oceans were calculated. Based on the frequencies, China and the surrounding oceans were first divided into four regions, i.e. the Tibetan Plateau region (TP), the eastern land region (EC), the southern ocean region (SO), and the Northwest Pacific region (WP). Horizontal and vertical scales of convective clouds over these four regions were then studied. Results showed that the horizontal scales of cumulus clouds over the ocean and land were about 2 and 1 km respectively, indicating a more scattered feature over land than over the ocean. Cumulus clouds over the ocean showed a larger scale because of the homogeneous thermodynamic property of ocean. Horizontal scales of deep convective clouds showed a feature opposite to the cumulus clouds, the scale range was 10–50 km with the largest scale of approximately 45 km in EC, and the smallest scale of about 30 km in WP. The horizontal scale of deep convective clouds over land was larger than that over the ocean and displayed a multi-scale feature, which is attributed to the complicated weather background over the ocean. The vertical scale of cumulus clouds was within the range of 0.24–2 km without obvious differences among the four sub-regions. The vertical scale of deep convective clouds over the ocean were deeper than that over the continent, with the maximum (15 km) in SO and the minimum (10 km) in the TP. Deep convective systems showed a smaller and deeper range over the ocean than over land.
Impacts of relative humidity and PM 2.5 concentration on atmospheric visibility: A comparative study of hourly observations of multiple stations
Vol 74,No. 06
To comprehensively investigate fundamental characteristics and associated influencing mechanisms in different regions of Zhejiang Province, based on hourly visibility data during 2013–2014 at Hangzhou station, Ningbo station and Wenzhou station, comparative analysis is conducted to study variability of visibility at different time-scales for the three cities. It is found that the occurrence frequencies of different visibility levels for the three cities are broadly consistent; with the rise of visibility level, the occurrence frequency gradually decreases. Besides, the visibility displays significant diurnal cycle. There are two low-visibility periods during the year, i.e. December to February and May to June. Generally speaking, the visibility in Ningbo is better while those in Hangzhou and Wenzhou are similar. Power spectrum analysis indicates that visibility in the three cities exhibits significant diurnal periodicity; many distinct peaks occur in the high-frequency range, and some peaks are also prominent in the low-frequency band. Further studies have been carried out to investigate the mechanism responsible for the change in visibility. Relative humidity and PM2.5 concentration are critically important and can effectively influence visibility. Increases in relative humidity and PM2.5 concentration can lead to the decline of visibility. At the same relative humidity level, the visibility drops rapidly in the beginning but decreases much slower after the “inflection point”. At the same level of PM2.5 concentration, the visibility gradually falls with the elevation of the relative humidity, which proves the importance of water vapor. Using the relative humidity and PM2.5 concentration as the impact factors, aquantitative statistical-model is constructed with nonlinear fitting scheme. It is demonstrated that the fitting result is pretty good. Finally, some existing problems and valuable scientific issues are discussed.
?Inter-annual and inter-decadal variability of the spring storm track over the North Pacific and its association with SST anomalies
Vol 74,No. 06
Based on the 20 CR reanalysis data and sea surface temperature (SST) data provided by European Center, the inter-annual (inter-decadal) variability of spring storm track over the North Pacific as well as the inter-decadal change in the relationship between the storm track and North Pacific SST are investigated. Results of Empirical Orthogonal Function (EOF) analysis show that there are two main variation modes for the spring storm track. The first mode represents its intensity variation and the second mode reflects its meridional variation in position. On the inter-decadal scale, the relationship between the storm track and North Pacific SST anomalies mainly indicates an atmosphere-to-ocean forcing. Under different decadal backgrounds, the inter-annual relationship between the storm track and SST anomalies over the Pacific Ocean exhibits different inter-decadal changes. After 1977, the relationship between the intensity of the storm track and North Pacific SST indicates an atmosphere-to-ocean forcing. Before 1977, however, the relationship reflected an ocean-to-atmosphere forcing that is opposite to the situation after 1977. Specifically, SST anomalies over the Kuroshio Extension imposed strong concurrent forcing on the atmosphere in the spring. On the other hand, the relationship between the meridional position of the storm track and North Pacific SST anomalies after 1977 indicates an atmosphere-to-ocean forcing as the storm track behaves to lead the central North Pacific SST anomalies. However, before 1977, the meridional position of the storm track was also closely related to simultaneous SST anomalies in the equatorial eastern Pacific in the spring, implying ENSO’s effect on the position of the storm track.