Synoptic Charts Research Articles

Early signals of synoptic-scale atmospheric anomalies associated with the summer low temperature events in Northeast China

Following a description of the climatology of the boreal summer persistent low temperature (LT) events of the Northeast (NE) China, this paper explores the synoptic characteristics of these events by decomposing atmospheric variables into three components: the daily climate, the zonal-averaged anomaly and the synoptic-scale anomaly. The synoptic-scale anomaly is used to construct the anomalous synoptic charts which tend to perform better compared to traditionally defined synoptic charts in terms of revealing synoptic characteristics of these LT events. Based on the analysis of 21 persistent LT events occurring during summers of 1961–2008 in NE China, we show that temperature anomaly at 850 hPa and geopotential height anomaly at 300 hPa were two critical early signals prior to the occurrences of these persistent LT events.

Geostrophic momentum approximation Q-vector and its application in synoptic charts

In this paper, we extend the expression of quasi-geostrophic Q-vector brought forward by Hoskins et al. into the Q-vector equation under the condition of geostrophic momentum approximation, and discuss the method of how to quantitatively estimate vertical motion in synoptic charts with Q-vector expression under geostrophic momentum approximation. Compared with the expression of quasi-geostrophic Q-vector, the Q-vector expression under geostrophic momentum approximation has two more terms which are related to geopotential height extremum and wind velocity extremum. Then, each term of Q-vector under geostrophic momentum approximation is transformed into the expression which is conveniently judged in synoptic charts. The results show that to judge vertical motions in synoptic chart quantitatively, one of the three ways can be used: when contour line presents the form of wave-like trough-ridge and passes through the entrance and exit areas of jet stream, correspondingly use the 1st term of Q-vector under geostrophic momentum approximation (i.e., quasi-geostrophic Q-vector); when there exist a closed pressure system and an angle between contour line and wind velocity, correspondingly use the 2nd term of Q-vector under geostrophic momentum approximation; at the jet streak, correspondingly use the 3rd term of Q-vector under geostrophic momentum approximation.

北京汛期暴雨气候特征分析

利用北京站(54511)1951~2012年的降水资料、环流特征量资料和历史天气图资料对过去62年北京汛期(6~8月)暴雨气候变化特征以及暴雨产生的天气形势分类进行分析。得出以下结论：1) 北京汛期暴雨累积雨量与汛期累积雨量变化趋势一致，呈逐年减少趋势，汛期暴雨贡献率呈现波动变化；2) 7、8月份的暴雨占前汛期累积雨量的比例呈一定左右的周期变化，未来10年北京可能再次进入暴雨高发期；3) 汛期暴雨频次的小波功率谱显示其存在2~3年和准5年的周期变化，估计2013年暴雨频次有偏少趋势；4) 北京汛期暴雨偏多的年份，副高面积偏大，强度偏强，脊线偏北、偏西，太阳黑子处于非活跃期；暴雨频次较少的年份，副高面积偏小，强度偏弱，脊线偏北、偏西，海温偏低，太阳黑子处于活跃期。 Using the data of precipitation, circulation parameters and historic synoptic chart at Beijing station, the climatic characteristics and the classification of weather situation in main flood season at Beijing station in the last 62 years were analysed. The conclusion was expressed as follow. 1) In flood season, the variation trend of accumulated rainstorm rainfall is as same as accumulated rainfall, showing a decreasing trend, and the rainstorm contribution rate shows a wave change. 2) In former flood season, the proportion of rainstorm in July and August shows some periodic changes, and the storm period may be coming in the next 10 years. 3) In flood season, the wavelet power spectrum of storm frequency is a 2 - 3-year period and a qusi-5-year period. According to it, the storm frequency will be on the low side in 2013. 4) In the years of more storms, the Western Pacific Subtropic High Area is larger; the strength is stronger; the ridge is more north and west; and sunspot is in an inactive period. Instead, in the years of fewer storms, the Western Pacific Subtropic High Area is smaller; the strength is weaker; the ridge is more north and west; the temperature is lower; and sunspot is in an active period.

Impact of variational assimilation technique on simulation of a heavy rainfall event over Pune, India

Prediction of heavy rainfall events due to severe convective storms in terms of their spatial and temporal scales is a challenging task for an operational forecaster. The present study is about a record-breaking heavy rainfall event observed in Pune (18°31′N, 73°55′E) on October 4, 2010. The day witnessed highest 24-h accumulated precipitation of 181.3 mm and caused flash floods in the city. The WRF model-based real-time weather system, operating daily at Centre for Development of Advanced Computing using PARAM Yuva supercomputer showed the signature of this convective event 4-h before, but failed to capture the actual peak rainfall and its location with reference to the city’s observational network. To investigate further, five numerical experiments were conducted to check the impact of assimilation of observations in the WRF model forecast. First, a control experiment was conducted with initialization using National Centre for Environmental Prediction (NCEP)’s Global Forecast System 0.5° data, while surface observational data from NCEP Prepbufr system were assimilated in the second experiment (VARSFC). In the third experiment (VARAMV), NCEP Prepbufr atmospheric motion vectors were assimilated. Fourth experiment (VARPRO) was assimilated with conventional soundings data, and all the available NCEP Prepbufr observations were assimilated in the fifth experiment (VARALL). Model runs were compared with observations from automated weather stations (AWS), synoptic charts of Indian Meteorological Department (IMD). Comparison of 24-h accumulated rainfall with IMD AWS 24-h gridded data showed that the fifth experiment (VARALL) produced better picture of heavy rainfall, maximum up to 251 mm/day toward the southern side, 31 km away from Pune’s IMD observatory. It was noticed that the effect of soundings observations experiment (VARPRO) caused heavy precipitation of 210 mm toward the southern side 49 km away from Pune. The wind analysis at 850 and 200 hPa indicated that the surface and atmospheric motion vector observations (VARAMV) helped in shifting its peak rainfall toward Pune, IMD observatory by 18 km, though VARALL over-predicted rainfall by 60 mm than the observed.

Variability of phenological stages of Dactylis glomerata in dependence on meteorological conditions in the Czech Republic

pressure (SLP) and 500 hPa geopotential height pattern over Europe on days with high concentration of ragweed pollen in Poznan in years 1996-2010. Methods: Ambrosia pollen data was collected by Hirst-type volumetric spore trap. Pollen grains were counted under the optical microscope (magni cation: 400x) and expressed as P m-3. Daily pollen concentrations were clustered in three intervals: low ( 30 Pm3) levels. For days attributed to these groups, synoptic charts were created on the basis of see level pressure (SLP) records from NCEP/NCAR reanalysis [2]. In addition, maps of 500 hPa geopotential heights were constructed. e method of interpolation was kriging. Results: Overall, 206, 23 and 17 days with low, medium and high concentration of ragweed pollen (respectively) were recorded in Poznan in years 1996-2010. Synoptic charts showed (Fig. 1) that during days with high pollen count of Ambrosia in Poznan the high pressure center was located in the area of northern Belorussia. e lowest pressure center was located over Iceland and the Atlantic Ocean in the south of the Iceland. As the geostrophic wind is parallel to the isobars and approximately determines the air mass transfer, it can be concluded that presented pressure pattern causes the air motion exactly from the Pannonian Plain to Poland, with south-east direction. Conclusions: e mechanism of long-range transport of Ambrosia pollen from Balkans to Poland highlighted by Sikoparija et al. [1] seems to be valid in all days with high concentrations of Ambrosia pollen in Poznan, 1996-2010. Averaged synoptic charts con rm that the air mass transport occurs from southeast to northwest with the strong high pressure center over Belorussia. When that pressure pattern is observed in weather forecast during August or September there is a possibility to record Ambrosia pollen in Poznan.

Coronal Holes in Solar Cycles 21 to 23

We present identifications of coronal holes (CHs) from observations in the He i 10 830 A line made at Kitt Peak Observatory (from 1975 to 2003) and in the EUV 195 A wavelength with SOHO/EIT (from 1996 to 2012). To determine whether a feature is a CH we have developed semi-automatic techniques for delineating CH borders on synoptic charts and for subsequent mapping of these borders on magnetic-field charts. Using these techniques, we superimposed CH borders on magnetic-field charts over the time interval from 1975 to 2012. A major contribution to the total area was made by high-latitude CHs, but in the declining phase of solar cycle 23, the contribution from low-latitude CHs increased substantially. Variations in the flux of Galactic cosmic rays and those in the inclination angle of the heliospheric current sheet followed the cyclic variations of CH areas. High-latitude CHs affect the properties of the solar wind in the ecliptic plane.

Trends of Dust Transport Episodes in Cyprus Using a Classification of Synoptic Types Established with Artificial Neural Networks

The relationship between dust episodes over Cyprus and specific synoptic patterns has long been considered but also further supported in recent studies by the authors. Having defined a dust episode as a day when the average PM10 measurement exceeds the threshold of 50 mg/(m3 day), the authors have utilized Artificial Neural Networks and synoptic charts, together with satellite and ground measurements, in order to establish a scheme which links specific synoptic patterns with the appearance of dust transport over Cyprus. In an effort to understand better these complicated synoptic-scale phenomena and their associations with dust transport episodes, the authors attempt in the present paper a followup of the previous tasks with the objective to further investigate dust episodes from the point of view of their time trends. The results have shown a tendency for the synoptic situations favoring dust events to increase in the last decades, whereas, the synoptic situations not favoring such events tend to decrease with time.

Identification of Long-Range Transported Haze Phenomena and Their Meteorological Features over Northeast Asia

AbstractThis paper presents a technique used to empirically classify operationally defined “haze” days in South Korea from 2000 to 2007 into long-range transported (LRT) and stagnant (STG) haze cases. A total of 547 haze days were classified into these two cases by tracking consecutive 6-day synoptic weather charts and air trajectories. The meteorological features associated with long-range transport of haze were identified by contrasting the values of 35 candidate meteorological parameters corresponding to the two types of haze cases. A suitable subset of synoptic variables was then chosen to diagnose the unique meteorological features of each case. The statistical test showed that geostrophic wind speed, vorticity, vorticity advection at a geopotential height of 850 hPa, and the vertical stability index of the lower atmosphere were indicated as highly effective parameters for distinguishing between the LRT and STG cases. The classification accuracies showed 93.2%, 87.8%, 85.4%, and 84.4% for these four variables, respectively. The STG case was well characterized by negative vorticity, with stable atmospheric stability conditions and weak geostrophic wind speed, that is, ~2.8 m s−1at a geopotential height of 850 hPa, whereas the LRT case had relatively strong geostrophic wind speed, >6 m s−1. For both cases, the location of the anticyclone played an important role in haze occurrence, directly and indirectly. A high pressure system led to stable STG haze with weak ventilation, resulting from upper-atmospheric subsidence. The LRT case was associated with a strong anticyclone that prevailed over southwestern China, maintaining the pressure gradient force that generated the westerly wind that was persistently conducive to downwind long-range transport of haze.

The 1962/1963 winter as observed at Belstead Hall (Suffolk) and through investigation of the synoptic charts

The 1962/1963 winter as observed at Belstead Hall (Suffolk) and through investigation of the synoptic charts

MODELING MAGNETIC FIELD STRUCTURE OF A SOLAR ACTIVE REGION CORONA USING NONLINEAR FORCE-FREE FIELDS IN SPHERICAL GEOMETRY

We test a nonlinear force-free field (NLFFF) optimization code in spherical geometry using an analytical solution from Low and Lou. Several tests are run, ranging from idealized cases where exact vector field data are provided on all boundaries, to cases where noisy vector data are provided on only the lower boundary (approximating the solar problem). Analytical tests also show that the NLFFF code in the spherical geometry performs better than that in the Cartesian one when the field of view of the bottom boundary is large, say, $20^\circ \times 20^\circ$. Additionally, We apply the NLFFF model to an active region observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) both before and after an M8.7 flare. For each observation time, we initialize the models using potential field source surface (PFSS) extrapolations based on either a synoptic chart or a flux-dispersal model, and compare the resulting NLFFF models. The results show that NLFFF extrapolations using the flux-dispersal model as the boundary condition have slightly lower, therefore better, force-free and divergence-free metrics, and contain larger free magnetic energy. By comparing the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the Atmospheric Imaging Assembly (AIA) on board SDO, we find that the NLFFF performs better than the PFSS not only for the core field of the flare productive region, but also for large EUV loops higher than 50 Mm.

Lagrangian coherent structures in the ocean favorable for fishery

Regions rich in nutrients with food grounds for zooplankton, the main feeding resource of pelagic fish, are locations of fishing grounds. Favorable condi� tions are usually formed in the subarctic frontal zones at the boundaries between cold and warm currents and in the periphery of mesoscale eddies. These are regions with high mechanical energy and intense horizontal mixing, in which phytoplankton, the food for zoop� lankton, can concentrate. Numerous investigations in different seas and oceans confirm that fronts and eddies are formations in which favorable conditions are formed for reproduction of plankton and growth of fish [1–3]. In the northwestern part of the Pacific Ocean east of Hokkaido Island (Japan) and the South� ern Kuril Islands, the waters of the cold subarctic Oyashio Current mix with the waters of the warm Kuroshio Current. Owing to the high concentration of nutrients in the cold waters of the Oyashio and high tides facilitating reproduction of phytoplankton in the surface waters, this region is known as one of the rich� est fishing locations in the world. The objective of this work is to distinguish the Lagrangian coherent structures in the ocean at the fronts (boundaries between the waters of different ori� gins), along which favorable conditions for fishery are formed. In the language of the theory of dynamic sys� tems, these structures are called unstable manifolds of hyperbolic points of nonstationary flow. The geo� strophic velocity field was calculated from the data of satellite altimetry. By calculating the displacements D of a large number of particles during a specific time period, one can plot a synoptic chart of this value for any region in which the fronts and the curves of the local minimum of D are clearly pronounced that visu� alize the strongest unstable manifolds in the region. It is shown in this paper that the vessels with the maximum catches of saury in the fall of 2002 and 2004 were located mainly along the unstable manifold depicting the Oyashio front at that period of time. We solve the equation for the advection of a passive admixture

Solar Activity and Deep Convection Modeling

We suggest from synoptic charts of radial magnetic field and intensities of spectral lines (Fe i, He ii, and Fe ix/x) over Carrington rotations 1942 – 2050 that deep convective layers control the pattern of large-scale solar activity. A new result is a Kolmogorov-type energy spectrum of the longitudinal variations of solar activity. This spectrum for nonphotospheric scales of convection (harmonic number m<100) is a new “fingerprint” of turbulence in the deep layers of the solar convection zone (CZ). The manifestation of one source of convective turbulence in the deep CZ is revealed as the excess in the power spectrum over the Kolmogorov spectrum. This source may be identified with giant convection cells at the CZ bottom. The convective cascade of the turbulence starts at the vortex size corresponding to the trans-CZ convective cells with the turnover time which the mixing length theory (MLT) predicts. This connection between the MLT formalism and real features in the Sun could account for the success of the MLT in stellar modeling.

LARGE-SCALE MAGNETIC HELICITY FLUXES ESTIMATED FROM MDI MAGNETIC SYNOPTIC CHARTS OVER THE SOLAR CYCLE 23

To investigate the characteristics of large-scale and long-term evolution of magnetic helicity with solar cycles, we use the method of Local Correlation Tracking to estimate the magnetic helicity evolution over solar cycle 23 from 1996 to 2009 using 795 MDI magnetic synoptic charts. The main results are as follows: the hemispheric helicity rule still holds in general, i.e., the large-scale negative (positive) magnetic helicity dominates the northern (southern) hemisphere. However, the large-scale magnetic helicity fluxes show the same sign in both hemispheres around 2001 and 2005. The global, large-scale magnetic helicity flux over the solar disk changes from a negative value at the beginning of solar cycle 23 to a positive value at the end of the cycle, while the net accumulated magnetic helicity is negative in the period between 1996 and 2009.

Winter daily precipitation variability over the East Anglian region of Great Britain and its relationship with river flow

This paper investigates winter (DJF) precipitation variability over East Anglia at the daily and 2 d timescales using rain gauge data from 134 sites. The first three principal components (PCs) explain 80.2% (82.0%) of the variance in daily (2 d totals). Precipitation displays higher spatial coherence in winter, with the first three PCs of summer daily totals (Neal and Phillips, 2009, International Journal of Climatology 29: 1661–1679) explaining only 72.3% of the variance. The winter PCs for both 24- and 48-h timescales display precipitation maxima in South Essex (PC 1), NE Norfolk (PC 2), and NW Cambridgeshire (PC 3). The rainfall maximum over South Essex is more important in winter than in summer. Lamb Weather Types and synoptic charts are used to explain the causes of the PCs. A precipitation regionalization is also produced. Discharge for 11 rivers is then modelled as a linear function of the rainfall patterns (as represented by the PC scores). With the exception of the River Babingley, whose discharge is not significantly related to the PCs, these models explain on average 26.5% of the variance. For most rivers, there are significant relationships between discharge and precipitation that fell up to 4 d ago on average. In general, East Anglian river flows show persistence over 6–8 d.

Weather and climate induced spatial variability of surface suspended particulate matter concentration in the North Sea and the English Channel

Images from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite have been used to investigate the meteorological and climate induced variability of suspended particulate matter (SPM) concentration in the North Sea. The meteorology has been characterized by the 11 weather types deduced from a refined system of Lamb’s classification of synoptic weather charts. Climatological effects have been related to the North Atlantic Oscillation index. The surface SPM concentration maps from MODIS have been ensemble averaged according to these weather types or climatological conditions. The data show that each type has a distinct distribution of surface SPM concentration in the North Sea. The differences are explained by different hydrodynamic and wave conditions. The occurrence of storms will impact the shallow regions by increasing the resuspension of bottom material. Prevailing winds will, on the other hand, change the residual transport of SPM in the North Sea. The more protected Southern Bight exhibits relatively stronger influences of advection, whereas in the central North Sea and the German Bight resuspension is more pronounced. This patterns result in an alternation of relatively high SPM concentration in the Southern Bight and in the rest of the southern North Sea during certain weather conditions. Limitations in satellite images have been assigned to stratification effects due to the occurrence of highly concentrated mud suspensions during certain weather types. The approach provides a tool to improve our understanding of coastal and shelf sea processes, especially with respect to variations of SPM concentration distribution according to weather, climate and climate change.

Digitization of Spörer's sunspot drawings

AbstractMuch of our knowledge about the solar dynamo is based on sunspot observations. It is thus desirable to extend the set of positional and morphological data of sunspots into the past. Gustav Spörer observed in Germany from Anklam (1861–1873) and Potsdam (1874–1894). He left detailed prints of sunspot groups, which we digitized and processed to mitigate artifacts left in the print by the passage of time. After careful geometrical correction, the sunspot data are now available as synoptic charts for almost 450 solar rotation periods. Individual sunspot positions can thus be precisely determined and spot areas can be accurately measured using morphological image processing techniques. These methods also allow us to determine tilt angles of active regions (Joy's law) and to assess the complexity of an active region.

Large scale magnetic helicity fluxes estimated from MDI magnetic synoptic charts

AbstractTo investigate the characteristics of large scale and long term evolution of magnetic helicity with solar cycles, we use the method of Local Correlation Tracking (LCT) to estimate the magnetic helicity evolution over the 23rd solar cycle from 1996 to 2009 by using 795 MDI magnetic synoptic charts. The main results are: the hemispheric helicity rule still holds in general, i.e. the large-scale negative (positive) magnetic helicity dominates the northern (southern) hemisphere. However, the large scale magnetic helicity fluxes show the same sign in both hemispheres around 2001 and 2005. The global, large scale magnetic helicity flux over the solar disk changes from negative value at the beginning of the 23rd solar cycle to positive value at the end of the cycle, which also shows the similar trend from the normalized magnetic flux by using the magnetic flux. The net accumulated magnetic helicity is negative in the period between 1996 and 2009.

Analysis of intense rainfall events on Madeira Island during the 2009/2010 winter

Abstract. This paper constitutes a step towards the understanding of some characteristics associated with high rainfall amounts and flooding on Madeira Island. The high precipitation events that occurred during the winter of 2009/2010 have been considered with three main goals: to analyze the main atmospheric characteristics associated with the events; to expand the understanding of the interaction between the island and the atmospheric circulations, mainly the effects of the island on the generation or intensification of orographic precipitation; and to evaluate the performance of high resolution numerical modeling in simulating and forecasting heavy precipitation events over the island. The MESO-NH model with a horizontal resolution of 1 km is used, as well as rain gauge data, synoptic charts and measurements of precipitable water obtained from the Atmospheric InfraRed Sounder (AIRS). The results confirm the influence of the orographic effects on precipitation over Madeira as well as the tropical–extratropical interaction, since atmospheric rivers were detected in six out of the seven cases analyzed, acting as a low level moisture supplier, which together with the orographic lifting induced the high rainfall amounts. Only in one of the cases the presence of a low pressure system was identified over the archipelago.

Spatial and temporal variation of the impact of an extreme Saharan dust event

The impact on PM10, meteorology and visibility of the severe Saharan dust outbreak registered in Europe in October 2008 is evaluated in detail in mainland Spain and the Balearic Islands. Data from a large number of air quality stations (261), METAR observations at 39 airports, besides records from meteorological networks, were used. Information from dispersion models, satellite observations, synoptic charts and back‐trajectory analysis, supported the interpretation. During the event, 89% of the monitoring stations exceeded the daily limit value. The highest daily averaged PM10 concentration across Spain ranged from 378 to 18μg m−3, following a hyperbolic decay with increasing latitude. An opposite relationship between visibility and PM10 was found for data at 12 UTC. The strength of the episode may be related to strong subsidence at low levels over the Iberian Peninsula.

Comparison of Line-of-Sight Magnetograms Taken by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and Solar and Heliospheric Observatory/Michelson Doppler Imager

We compare line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) and the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO). The line-of-sight magnetic signal inferred from the calibrated MDI data is greater than that derived from the HMI data by a factor of 1.40. This factor varies somewhat with center-to-limb distance. An upper bound to the random noise for the 1′′ resolution HMI 720-second magnetograms is 6.3 Mx cm−2, and 10.2 Mx cm−2 for the 45-second magnetograms. Virtually no p-mode leakage is seen in the HMI magnetograms, but it is significant in the MDI magnetograms. 12-hour and 24-hour periodicities are detected in strong fields in the HMI magnetograms. The newly calibrated MDI full-disk magnetograms have been corrected for the zero-point offset and underestimation of the flux density. The noise is 26.4 Mx cm−2 for the MDI one-minute full-disk magnetograms and 16.2 Mx cm−2 for the five-minute full-disk magnetograms observed with four-arcsecond resolution. The variation of the noise over the Sun’s disk found in MDI magnetograms is likely due to the different optical distortions in the left- and right-circular analyzers, which allows the granulation and p-mode to leak in as noise. Saturation sometimes seen in sunspot umbrae in MDI magnetograms is caused by the low intensity and the limitation of the onboard computation. The noise in the HMI and MDI line-of-sight magnetic-field synoptic charts appears to be fairly uniform over the entire map. The noise is 2.3 Mx cm−2 for HMI charts and 5.0 Mx cm−2 for MDI charts. No evident periodicity is found in the HMI synoptic charts.