scholarly journals Planetary boundary influence at the Jungfraujoch analyzed by aerosol cycles and synoptic weather types

2011 ◽  
Vol 11 (1) ◽  
pp. 985-1024 ◽  
Author(s):  
M. Collaud Coen ◽  
E. Weingartner ◽  
M. Furger ◽  
S. Nyeki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Relative Increase ◽  
Weather Type ◽  
Specific Humidity ◽  
Weather Types ◽  
Annual Cycles ◽  
Air Masses ◽  
Scattering Coefficients ◽  
Diurnal Cycles ◽  
Synoptic Weather ◽  
Time Of Year

Abstract. Fourteen years of meteorological parameters, aerosol variables (absorption and scattering coefficients, aerosol number concentration) and trace gases (CO, NOx, SO2) measured at the Jungfraujoch (JFJ, 3580 m a.s.l.) have been analyzed as a function of different synoptic weather types. The Alpine Weather Statistics (AWS) classification was used to define the synoptic meteorology over the whole Swiss region. The seasonal contribution of each synoptic weather type to the aerosol concentration was deduced from the aerosol annual cycles while the planetary boundary layer (PBL) influence was estimated by means of the diurnal cycles. Since aerosols are scavenged by precipitation, the diurnal cycle of the CO concentration was also used to identify polluted air masses. SO2 and NOx concentrations were used as precursor tracers for new particle formation and growth. This study confirms the consensus view that the JFJ is mainly influenced by the free troposphere during winter and by injection of air parcels from the PBL during summer. A more detailed picture is, however, drawn where the JFJ is completely influenced by free tropospheric air masses in winter during advective weather types and largely influenced by the PBL also during the night in summer during the subsidence weather type. Between these two extreme situations, the PBL influence at the JFJ depends on both the time of year and the synoptic weather type. The fraction of PBL air transported to the JFJ was estimated by the relative increase of the specific humidity and CO.

scholarly journals Aerosol climatology and planetary boundary influence at the Jungfraujoch analyzed by synoptic weather types

2011 ◽  
Vol 11 (12) ◽  
pp. 5931-5944 ◽  
Author(s):  
M. Collaud Coen ◽  
E. Weingartner ◽  
M. Furger ◽  
S. Nyeki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Relative Increase ◽  
Number Concentration ◽  
Weather Type ◽  
Specific Humidity ◽  
Optical Parameters ◽  
Weather Types ◽  
Annual Cycles ◽  
Air Masses ◽  
Scattering Coefficients ◽  
Synoptic Weather

Abstract. Fourteen years of meteorological parameters, aerosol variables (absorption and scattering coefficients, aerosol number concentration) and trace gases (CO, NOx, SO2) measured at the Jungfraujoch (JFJ, 3580 m a.s.l.) have been analyzed as a function of different synoptic weather types. The Schüepp synoptic weather type of the Alps (SYNALP) classification from the Alpine Weather Statistics (AWS) was used to define the synoptic meteorology over the whole Swiss region. The seasonal contribution of each synoptic weather type to the aerosol concentration was deduced from the aerosol annual cycles while the planetary boundary layer (PBL) influence was estimated by means of the diurnal cycles. Since aerosols are scavenged by precipitation, the diurnal cycle of the CO concentration was also used to identify polluted air masses. SO2 and NOx concentrations were used as precursor tracers for new particle formation and growth, respectively. The aerosol optical parameters and number concentration show elevated loadings during advective weather types during the December–March period and for the convective anticyclonic and convective indifferent weather types during the April–September period. This study confirms the consensus view that the JFJ is mainly influenced by the free troposphere during winter and by injection of air parcels from the PBL during summer. A more detailed picture is, however, drawn where the JFJ is completely influenced by free tropospheric air masses in winter during advective weather types and largely influenced by the PBL also during the night in summer during the subsidence weather type. Between these two extreme situations, the PBL influence at the JFJ depends on both the time of year and the synoptic weather type. The fraction of PBL air transported to the JFJ was estimated by the relative increase of the specific humidity and CO.

An objective definition of seasons for the Mediterranean region based on synoptic weather types

2020 ◽  
Author(s):  
George Kotsias ◽  
Christos Lolis ◽  
Nikolaos Hatzianastassiou ◽  
Piero Lionello ◽  
Aristides Bartzokas
Keyword(s):  
Air Temperature ◽  
Mediterranean Region ◽  
Grid Point ◽  
Specific Humidity ◽  
Weather Types ◽  
Similar Frequency ◽  
Annual Variations ◽  
Synoptic Weather ◽  
The Mediterranean ◽  
Definition Of

<p>An objective definition of seasons for the Mediterranean region is performed based on the intra-annual variation of the frequencies of eight (8) objectively defined synoptic Weather Types (WTs). The data used for the determination of the 8 WTs are daily NCEP/NCAR Reanalysis grid point values of 2m air temperature, total cloud cover, 2m zonal and meridional wind components, 500hPa and 1000hPa geopotential height, 500hPa and 850hPa air temperature, 850hPa specific humidity and precipitable water over the Mediterranean region, for the period 1949-2018. Firstly, Principal Component Analysis (PCA) is applied to the inter-annual variations of the above parameters in order to reduce the dimensionality and then k-means Cluster Analysis (CA) is applied to the resultant Principal Components (PCs) in order to group dates with similar patterns of the above parameters, resulting in 8 synoptic WTs. Then, PCA and CA are applied again, now on the intra-annual variations of the frequencies of the resultant WTs and group dates of the year (seasons) with similar frequency distribution among the 8 WTs. According to the results, four (4) seasons are defined for the 70-year period 1949-2018. The same methodology is applied also for the five overlapping 30-year sub-periods 1949-1978, 1959-1988, 1969-1998, 1979-2008 and 1989-2018, leading to 4 seasons too. Although the characteristics of these seasons generally correspond to the ones of the four conventional seasons, there are differences regarding the onset and cessation dates and the duration. In general, it is found that winter and summer last about 4 months (115 and 114 days respectively), spring has a duration of about 2.5 months (72 days) and autumn lasts about 2 months (64 days). The most remarkable long-term changes of the seasons’ characteristics are: (i) the colder winters and warmer autumns during the last decades, (ii) the shortening of winter and spring due to later onset and earlier cessation dates, respectively, and (iii) the extension of autumn and summer due to later cessation and earlier onset dates, respectively.</p>

Seasonal and Synoptic Variations in Near-Surface Air Temperature Lapse Rates in a Mountainous Basin

2008 ◽  
Vol 47 (1) ◽  
pp. 249-261 ◽  
Author(s):  
Troy R. Blandford ◽  
Karen S. Humes ◽  
Brian J. Harshburger ◽  
Brandon C. Moore ◽  
Von P. Walden ◽  
...  
Keyword(s):  
Air Temperature ◽  
Surface Air Temperature ◽  
Lapse Rate ◽  
Maximum Temperature ◽  
Weather Types ◽  
Near Surface ◽  
Air Masses ◽  
Synoptic Weather ◽  
South Central ◽  
Lapse Rates

Abstract To accurately estimate near-surface (2 m) air temperatures in a mountainous region for hydrologic prediction models and other investigations of environmental processes, the authors evaluated daily and seasonal variations (with the consideration of different weather types) of surface air temperature lapse rates at a spatial scale of 10 000 km2 in south-central Idaho. Near-surface air temperature data (Tmax, Tmin, and Tavg) from 14 meteorological stations were used to compute daily lapse rates from January 1989 to December 2004 for a medium-elevation study area in south-central Idaho. Daily lapse rates were grouped by month, synoptic weather type, and a combination of both (seasonal–synoptic). Daily air temperature lapse rates show high variability at both daily and seasonal time scales. Daily Tmax lapse rates show a distinct seasonal trend, with steeper lapse rates (greater decrease in temperature with height) occurring in summer and shallower rates (lesser decrease in temperature with height) occurring in winter. Daily Tmin and Tavg lapse rates are more variable and tend to be steepest in spring and shallowest in midsummer. Different synoptic weather types also influence lapse rates, although differences are tenuous. In general, warmer air masses tend to be associated with steeper lapse rates for maximum temperature, and drier air masses have shallower lapse rates for minimum temperature. The largest diurnal range is produced by dry tropical conditions (clear skies, high solar input). Cross-validation results indicate that the commonly used environmental lapse rate [typically assumed to be −0.65°C (100 m)−1] is solely applicable to maximum temperature and often grossly overestimates Tmin and Tavg lapse rates. Regional lapse rates perform better than the environmental lapse rate for Tmin and Tavg, although for some months rates can be predicted more accurately by using monthly lapse rates. Lapse rates computed for different months, synoptic types, and seasonal–synoptic categories all perform similarly. Therefore, the use of monthly lapse rates is recommended as a practical combination of effective performance and ease of implementation.

Convective cold pools in long-term boundary layer mast observations

2021 ◽  
Author(s):  
Bastian Kirsch ◽  
Felix Ament ◽  
Cathy Hohenegger
Keyword(s):  
Boundary Layer ◽  
Specific Humidity ◽  
Cold Pool ◽  
Temperature Perturbation ◽  
Statistical Characterization ◽  
Near Surface ◽  
Air Masses ◽  
Diurnal Cycles ◽  
Cold Pools ◽  
Rapid Temperature

AbstractCold pools are mesoscale features, that are key for understanding the organization of convection, but are insufficiently captured in conventional observations. This study conducts a statistical characterization of cold-pool passages observed at a 280 m high boundary layer mast in Hamburg (Germany) and discusses factors controlling their signal strength. During 14 summer seasons 489 cold-pool events are identified from rapid temperature drops below -2 K associated with rainfall. The cold-pool activity exhibits distinct annual and diurnal cycles peaking in July and mid afternoon, respectively. The median temperature perturbation is -3.3 K at 2-m height and weakens above. Also the increase in hydrostatic air pressure and specific humidity is largest near the surface. Extrapolation of the vertically weakening pressure signal suggests a characteristic cold-pool depth of about 750 m. Disturbances in the horizontal and vertical wind speed components document a lifting-induced circulation of air masses prior to the approaching cold-pool front. According to a correlation analysis, the near-surface temperature perturbation is more strongly controlled by the pre-event saturation deficit (r=-0.71) than by the event-accumulated rainfall amount (r=-0.35). Simulating the observed temperature drops as idealized wet-bulb processes suggests that evaporative cooling alone explains 64 % of the variability in cold-pool strength. This number increases to 92 % for cases that are not affected by advection of mid-tropospheric low-Θe air masses under convective downdrafts.

scholarly journals The Link Between from Day to Day Change of Weather Types and Synoptic Situations in Kraków During the Period 1961–2010

2013 ◽  
Vol 32 (3) ◽  
pp. 69-84 ◽  
Author(s):  
Katarzyna Piotrowicz ◽  
Joanna Szlagor
Keyword(s):  
Air Temperature ◽  
Temperature Fluctuations ◽  
Weather Type ◽  
Synoptic Situation ◽  
Weather Types ◽  
Air Mass ◽  
Air Masses ◽  
Circulation Types ◽  
Atmospheric Fronts ◽  
The Impact

Abstract This paper analyses day-to-day changes of weather types and links these with synoptic situations, i.e. circulation types, air masses and weather fronts. The weather types were classified according to Woś (1999), while a calendar proposed by Niedźwiedź (2013) was used for synoptic situations. Weather records from Kraków were used covering the period 1961-2010. The frequency of all combinations of day-to-day weather type changes was calculated, identified using specific values of air temperature, cloudiness and precipitation. The analysis of the succession and frequency of the day-to-day changes was linked with the synoptic situations accompanying the change. It was found that the thermal weather types were relatively very stable and remained unchanged on the following day in 61.3% of cases, and that the synoptic situation also remained similar. Weather subtypes, identified with just cloudiness and precipitation, but not temperature, displayed much more day-to-day change in terms of frequency and scale. Synoptically it was the air mass change and/or the occurrence of atmospheric fronts, which tended to cause day-to-day weather type changes, while the impact of circulation was not always clear. Particular attention was devoted to sudden weather type changes caused primarily by dramatic air temperature fluctuations.

New Climatic Zones in Iran: A Comparative Study of Different Empirical Methods and Clustering Technique

2021 ◽  
Author(s):  
Faezeh Abbasi ◽  
Saeed Bazgeer ◽  
Parviz Rezazadeh Kalehbasti ◽  
Ebrahim Asadi Oskoue ◽  
Masoud Haghighat ◽  
...  
Keyword(s):  
Zagros Mountains ◽  
Empirical Methods ◽  
Climate Classification ◽  
Climate Type ◽  
Air Masses ◽  
Clustering Technique ◽  
Mountainous Regions ◽  
Synoptic Weather ◽  
Industrial Sectors ◽  
Weather Stations

Abstract It is a scientifically novel insight to classify the climate of a region using empirical methods together with clustering technique for practical usage in agricultural and industrial sectors. The main objective of this study is to compare the empirical approach to climate classification (Thornthwaite and Mather, De Martonne, the Extended De Martonne and the IRIMO (I.R. of Iran Meteorological Organization)) with clustering technique, Ward’s hierarchical agglomerative method over Iran. The maximum and minimum temperatures and precipitation data of 356 weather stations are used from IRIMO databases. 35 synoptic weather stations are selected for detailed inspection based on appropriate geographical distribution and availability of a continuous 50-year data (1966–2015). Compared with the three empirical reference methods of climate classification, the Thornthwaite and Mather method clearly shows the role of water bodies and air masses for determining the climate type in different regions. This factor is identified as the main advantage of this method over the three others. This superiority is the most visible for the highlands/mountainous regions, in the vicinity of the Zagros Mountains, and in the western regions of Iran. As a case in point, while in the De Martonne and the Extended De Martonne methods, the Zagros storm cell is climatically classified similar to patchy areas in Caspian Sea coastal zone, this cell is correctly identified as a separate zone in the Thornthwaite and Mather method. The results revealed that the clusters obtained from Ward’s algorithm are comparable to those of empirical climate classifications, particularly Thornthwaite and Mather method.

scholarly journals The Role of Weather Types in Assessing the Rainfall Key Factors for Erosion in Two Different Climatic Regions

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 443 ◽  
Author(s):  
María Fernández-Raga ◽  
Roberto Fraile ◽  
Covadonga Palencia ◽  
Elena Marcos ◽  
Ana María Castañón ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Weather Type ◽  
Key Factors ◽  
Weather Types ◽  
Climatic Regions ◽  
Distribution Parameters ◽  
Study Zone ◽  
Raindrop Size ◽  
Rain Events ◽  
One Year

This paper compares two different geographical sites, Aveiro and León, from different climatic regions, oceanic and continental, but which share the same type of weather (according to Lamb’s classification). The analysis was carried out over one year, and has revealed that rainfall in Aveiro is heavier and more abundant, with a higher number of raindrops and a longer duration of rain events (on average, 10 min longer than in Leon). Mean raindrop size is 0.45 mm in Aveiro and slightly smaller (0.37 mm) in Leon; in addition, the kinetic energy and linear momentum values in Aveiro are three times higher than those in Leon. A comparison of raindrop size distributions by weather type has shown that for both locations westerly weather presented a higher probability of rainfall, and the gamma distribution parameters for each weather type were independent of the study zone. When the analysis is done for the characteristics of rain related with erosion, the westerly cyclonic weather types (cyclonic west (CW) and cyclonic south-westerly (CSW)) are among the most energetic ones in both locations. However, comparing their five weather types with higher kinetic energy, in Aveiro a westerly component implies higher kinetic energy, while in Leon a southerly component involves more energy in the rain.

Sign in / Sign up

Export Citation Format

Share Document