Monthly Frequency Distribution Research Articles

Growth and Reproductive Biology of Bream, Acanthobrama thisbeae (Freyhof&Özuluğ, 2014) a New Endemic Species in Sır Reservoir, Kahramanmaraş, Turkey

In this study growth and reproductive biology of endemic and new species Acanthobrama thisbeae in Sır Reservoir were investigated. The population were composed of 80.6% female and 19.40 % male individuals. The individuals' total lengths (mm) and total weights (g) varied between 130.4 to 260.5 mm and 12.92 to 203.89 g, respectively. Age groups 2 to 8 were identified in the population and the majority of the sample was between 130 to 180 mm (80.22%). The length-weight relationship for all samples was W= 0.0000003*TL3.7265 with b value was significantly (p<0.001). The mean condition factors were 1.011±0.17 (n:263) between females and males. In observations of monthly changes, the gonadosomatic index (GSI) and the monthly frequency distribution spawning period were determined between April and June. Mean fecundity was 3574 egg/fish on mature individuals in reproductive periods. In addition, A. thisbeae individuals in Sır Reservoir were observed to be under the pressure of exotic species such as Liza abu and Carassius gibelio.

Reproductive biology of the white marlin ( Kajikia albida ) in the southwestern and equatorial Atlantic Ocean

The present work describes the reproductive biology of the white marlin (Kajikia albida) caught in the southwestern and equatorial Atlantic Ocean. The gonads of 924 fish were collected by observers on board Brazilian tuna longliners, between November 2004 and December 2006. The spawning season was assessed by the monthly frequency distribution of distinct stages of maturity and monthly mean female gonadosomatic index GSI. Sixty-one percent (n = 656) of the fish examined were female, with a Lower Jaw Fork Length (LJFL) between 83 and 236 cm (mean = 155.5 ± 16.63). The 268 males had a LJFL between 90 and 220 cm (mean = 152.3 ± 34.62). Although the northeastern region of Brazil does not appear to be a significant spawning area for the species, the results suggest a higher reproductive activity in the third quarter of the year. Using a Bayesian logistic model approach, length at 50% maturity was estimated at 145.04 cm (credibility interval of 95%, 143.94–146.09 cm), for females, and at 140.03 cm (credibility interval of 95%, 137.28–142.52 cm), for males.

The Combined Effects of SST and the North Atlantic Subtropical High-Pressure System on the Atlantic Basin Tropical Cyclone Interannual Variability

The combined effect of the sea surface temperature (SST) and the North Atlantic subtropical high-pressure system (NASH) in the interannual variability of the genesis of tropical cyclones (TCs) and landfalling in the period 1980–2019 is explored in this study. The SST was extracted from the Centennial Time Scale dataset from the National Oceanic and Atmospheric Administration (NOAA), and TC records were obtained from the Atlantic Hurricane Database of the NOAA/National Hurricane Center. The genesis and landfalling regions were objectively clustered for this analysis. Seven regions of TC genesis and five for landfalling were identified. Intercluster differences were observed in the monthly frequency distribution and annual variability, both for genesis and landfalling. From the generalized least square multiple regression model, SST and NASH (intensity and position) covariates can explain 22.7% of the variance of the frequency of TC genesis, but it is only statistically significant (p < 0.1) for the NASH center latitude. The SST mostly modulates the frequency of TCs formed near the West African coast, and the NASH latitudinal variation affects those originated in the Lesser Antilles arc. For landfalling, both covariates explain 38.7% of the variance; however, significant differences are observed in the comparison between each region. With a statistical significance higher than 90%, SST and NASH explain 33.4% of the landfalling variability in the archipelago of the Bahamas and central–eastern region of Cuba. Besides, landfalls in the Gulf of Mexico and Central America seem to be modulated by SST. It was also found there was no statistically significant relationship between the frequency of genesis and landfalling with the NASH intensity. However, the NASH structure modulates the probability density of the TCs trajectory that make landfall once or several times in their lifetime. Thus, the NASH variability throughout a hurricane season affects the TCs trajectory in the North Atlantic basin. Moreover, we found that the landfalling frequency of TCs formed near the West Africa coast and the central North Atlantic is relatively low. Furthermore, the SST and NASH longitude center explains 31.6% (p < 0.05) of the variance of the landfalling intensity in the archipelago of the Bahamas, while the SST explains 26.4% (p < 0.05) in Central America. Furthermore, the 5-year moving average filter revealed decadal and multidecadal variability in both genesis and landfalling by region. Our findings confirm the complexity of the atmospheric processes involved in the TC genesis and landfalling.

Maturity, growth and natural mortality rate of the introduced fish Parachromis managuensis (Perciformes: Cichlidae) in the semiarid region of Brazil

Abstract: Aim The present study aimed to estimate the sexual maturity, growth and mortality rates of the jaguar guapote, Parachromis managuensis, an introduced fish species in the Brazilian semiarid region. Methods Specimens were collected between December 2015 and November 2016, in a dam at Serra Talhada municipality, Pernambuco, where the species was abundant. Results In total, 520 individuals were analyzed, with total lengths (TL) varying between 23 and 240 mm. Length at sexual maturity varied between 130.87 and 140.68 mm TL (Mean = 135.78 mm TL). Through the modal progression of monthly frequency distributions, the following growth parameters were obtained according to the von Bertalanffy model: L∞ = 341.40 mm, k = 0.840 and t0 = -0.035 year-1. Ages varied from 0.05 to 1.41 year, and an age at first maturity between 0.48 and 0.53 year (Mean = 0.51 year), with the largest part of the sample (72.64%) made of adult individuals. Natural mortality rates (M) were estimated from three different methods, varying between 1.53 and 3.04, with a mean of 2.27. Conclusions P. managuensis shows fast growth and maturation and high natural mortalities, which grants it biological advantages when compared to native species from the same trophic level in the area.

Dynamic and Statistical Features of Internal Solitary Waves on the Continental Slope in the Northern South China Sea Derived From Mooring Observations

AbstractFor investigation of internal solitary waves (ISWs) in the South China Sea (SCS), most cruise observations are concentrated from Luzon Strait to Dongsha Atoll in the northeastern SCS but few on the continental slope far away from the west of Dongsha Atoll. In this study, we use 1‐year long mooring data to determine dynamic and statistical features of the ISWs on the shelf slope of the northwestern SCS. The analysis results of the mooring data reveal that the ocean internal waves on the shelf slope of the northwestern SCS have physical properties of highly nonlinear waves, which are well described by the solutions of the Korteweg‐de Vries equation. The mean nonlinear phase speeds of mode‐1 and mode‐2 ISWs are 1.38 ± 0.14 and 0.66 ± 0.12 m/s, respectively. The major direction of mode‐1 ISWs is northwestward 305° ± 21°. Strong ISW currents force the major direction of total current velocities to turn 67.5° in the upper layer and 135° in the lower layer. The monthly occurrence frequency distribution of ISWs shows a peak in July with a maximum frequency of 16.2% and a trough in March with a minimum frequency of 3.3%. Mode‐2 ISWs appear most in December, accounting for 50% of total mode‐2 ISWs. The largest mode‐2 ISW on record up today with the depressed amplitude as large as 91 m, and the elevated amplitude of 73 m was observed at mooring station. These new findings and new data are of significance to local internal wave prediction model development.

Growth estimation of the larger foraminifer Heterostegina depressa by means of population dynamics.

In Heterostegina depressa, the flagship species of laboratory investigations of larger benthic foraminifera (LBF) since the 70’s, the timing of reproduction, longevity and natural chamber building rates are still understudied. A recently developed method, the natural laboratory (sensu Hohenegger), has been applied on H. depressa populations from Sesoko Jima, NW Okinawa, Japan. An averaged chamber building rate and longevity of H. depressa were calculated based on 17 monthly samplings at fixed stations. All samples were collected at 20 and 50 m water depths using SCUBA. Live populations were dried and investigated by microCT. The monthly frequency distributions of chamber numbers and test diameters have been decomposed in normally distributed components. For each month, mean and standard deviations of the components were used to calculate the maximum chamber number and maximum test diameter. Based on these values, the natural chamber building rate (CBR) or diameter increase rate (DIR) could be estimated using the Michaelis-Menten function. CBR and DIR were inverted to estimate the ‘birthdate’ of all investigated individuals. Based on frequencies of these ‘birthdates’, main reproduction events could be detected and compared to the reproduction timing of other subtropical and tropical LBF taxa. Furthermore, peaks in reproduction could be linked to monsoon wet seasons (=“rainy seasons”) and winter rains.

Intraseasonal Variations of Winter Wind Chill Temperatures across Canada and the United States

AbstractWind chill temperature (WCT) is a measure of the human sensation of cold and also is a parameter used to represent the severity of winter weather. This study provides a unique investigation to quantify the spatial patterns of monthly mean, extreme, and severe WCTs across Canada and the United States. WCT was examined across 45 winters (December–February) spanning 1969/70–2013/14 using 156 surface locations reporting hourly meteorological conditions. Intraseasonal analyses of WCT showed that January had 1) the coldest mean WCTs, 2) the most extreme WCTs as statistically represented by the coldest 1% of the monthly WCT frequency distribution at each surface location, and 3) the greatest frequency of severe WCT hours that were ≤ −32°C. The most extreme WCTs were most often located in the Hudson Bay region of Canada, and north-central and northeastern North America experienced the largest monthly changes in WCT during the winter season. Results suggest that intraseasonal changes of air temperature are the primary influence on variations of WCT and that changes of wind speed are a secondary factor.

Trends and variability of atmospheric PM<sub>2.5</sub> and PM<sub>10–2.5</sub> concentration in the Po Valley, Italy

Abstract. The Po Valley is one of the largest European regions with a remarkably high concentration level of atmospheric pollutants, both for particulate and gaseous compounds. In the last decade stringent regulations on air quality standards and on anthropogenic emissions have been set by the European Commission, including also for PM2.5 and its main components since 2008. These regulations have led to an overall improvement in air quality across Europe, including the Po Valley and specifically PM10, as shown in a previous study by Bigi and Ghermandi (2014). In order to assess the trend and variability in PM2.5 in the Po Valley and its role in the decrease in PM10, we analysed daily gravimetric equivalent concentration of PM2.5 and of PM10–2.5 at 44 and 15 sites respectively across the Po Valley. The duration of the times series investigated in this work ranges from 7 to 10 years. For both PM sizes, the trend in deseasonalized monthly means, annual quantiles and in monthly frequency distribution was estimated: this showed a significant decreasing trend at several sites for both size fractions and mostly occurring in winter. All series were tested for a significant weekly periodicity (a proxy to estimate the impact of primary anthropogenic emissions), yielding positive results for summer PM2.5 and for summer and winter PM10–2.5. Hierarchical cluster analysis showed moderate variability in PM2.5 across the valley, with two to three main clusters, dividing the area in western, eastern and southern/Apennines foothill sectors. The trend in atmospheric concentration was compared with the time series of local emissions, vehicular fleet details and fuel sales, suggesting that the decrease in PM2.5 and in PM10 originates from a drop both in primary and in precursors of secondary inorganic aerosol emissions, largely ascribed to vehicular traffic. Potentially, the increase in biomass burning emissions in winter and the modest decrease in NH3 weaken an otherwise even larger drop in atmospheric concentrations.

Analysis of solar irradiation measurements at Beer Sheva, Israel from 1985 through 2013

An in-depth analysis of the solar horizontal global, normal incidence beam and solar global incident on a south-facing surface tilted at 40° irradiation monitored at Beer Sheva from 1985 through 2013 has been performed. The horizontal beam irradiation, daily clearness index, daily beam index and beam fraction of the horizontal global irradiation were determined from the measured parameters. A statistical analysis, which included average, median, standard deviation, maximum and minimum values and the coefficient of variation, was performed on the parameters under investigation. The monthly frequency distribution types were determined for the solar global, normal incidence beam and solar global incident on a south-facing surface tilted at 40° irradiation based upon their corresponding skewness and kurtosis values. In addition, typical meteorological years were developed for the solar horizontal global and normal incidence beam irradiation.Beer Sheva is characterized as a site with a high incidence of clear days with global irradiation consisting of a relatively high beam fraction. A relatively steep minimum in the annual average daily normal incidence beam irradiation is observed from 1991 to 1993 and has been attributed to the eruption of Mt. Pinatubo, Philippines during June 1991. A time series analysis of the both individual monthly and annual average daily global and normal incidence irradiation indicated a slight trend of solar brightening for this region during the time interval 1985 through 2013, but in most cases they were not statistically significant based upon their p values.

The Sensitivity of Rainfall Estimation to Error Assumptions in a Bayesian Passive Microwave Retrieval Algorithm

AbstractThe Goddard profiling algorithm (GPROF) uses Bayesian probability theory to retrieve rainfall over the global oceans. A critical component of GPROF and most Bayes theorem–based retrieval frameworks is the specification of uncertainty in the observations being utilized to retrieve the parameter of interest. In the case of GPROF, for any sensor, uncertainties in microwave brightness temperatures (Tbs) arise from radiative transfer model errors, satellite sensor noise and/or degradation, and nonlinear, scene-dependent Tb offsets added during sensor intercalibration procedures. All mentioned sources impact sensors in a varying fashion, in part because of sensor-dependent fields of view. It is found that small errors in assumed Tb uncertainty (ranging from 0.57 K at 10 GHz to 2.29 K at 85 GHz) lead to a 3.6% change in the retrieved global-average oceanic rainfall rate, and 10%–20% (20%–40%) shifts in the pixel-level (monthly) frequency distributions for given rainfall bins. A mathematical expression describing the sensitivity of retrieved rainfall to uncertainty is developed here. The strong global sensitivity is linked to rainfall variance scaling systematically as Tb varies. For ocean scenes, the same emission-dominated rainfall–Tb physics used in passive microwave rainfall retrieval is also responsible for the substantial underestimation (overestimation) of global rainfall if uncertainty is overestimated (underestimated). Proper uncertainties are required to quantify variability in surface rainfall, assess long-term trends, and provide robust rainfall benchmarks for general circulation model evaluations. The implications for assessing global and regional biases in active versus passive microwave rainfall products, and for achieving rainfall product agreement among a constellation of orbiting microwave radiometers [employed in the Global Precipitation Measurement (GPM) mission], are also discussed.

Long-term trend and variability of atmospheric PM<sub>10</sub> concentration in the Po Valley

Abstract. The limits to atmospheric pollutant concentration set by the European Commission provide a challenging target for the municipalities in the Po Valley, because of the characteristic climatic conditions and high population density of this region. In order to assess climatology and trends in the concentration of atmospheric particles in the Po Valley, a data set of PM10 data from 41 sites across the Po Valley have been analysed, including both traffic and background sites (either urban, suburban or rural). Of these 41 sites, 18 with 10 yr or longer record have been analysed for long-term trend in deseasonalized monthly means, in annual quantiles and in monthly frequency distribution. A widespread significant decreasing trend has been observed at most sites, up to a few percent per year, by a generalized least squares and Theil–Sen method. All 41 sites have been tested for significant weekly periodicity by Kruskal–Wallis test for mean anomalies and by Wilcoxon test for weekend effect magnitude. A significant weekly periodicity has been observed for most PM10 series, particularly in summer and ascribed mainly to anthropic particulate emissions. A cluster analysis has been applied in order to highlight stations sharing similar pollution conditions over the reference period. Five clusters have been found, two encompassing the metropolitan areas of Turin and Milan and their respective nearby sites and the other three clusters gathering northeast, northwest and central Po Valley sites respectively. Finally, the observed trends in atmospheric PM10 have been compared to trends in provincial emissions of particulates and PM precursors, and analysed along with data on vehicular fleet age, composition and fuel sales. A significant basin-wide drop in emissions occurred for gaseous pollutants, contrarily to emissions of PM10 and PM2.5, whose drop was low and restricted to a few provinces. It is not clear whether the decrease for only gaseous emissions is sufficient to explain the observed drop in atmospheric PM10, or if the low drop in particulate emissions is indeed due to the uncertainty in the emission inventory data for this species.

Snow Temperature Changes within a Seasonal Snowpack and Their Relationship to Turbulent Fluxes of Sensible and Latent Heat

Abstract Snowpack temperatures from a subalpine forest below Niwot Ridge, Colorado, are examined with respect to atmospheric conditions and the 30-min above-canopy and subcanopy eddy covariance fluxes of sensible Qh and latent Qe heat. In the lower snowpack, daily snow temperature changes greater than 1°C day−1 occurred about 1–2 times in late winter and early spring, which resulted in transitions to and from an isothermal snowpack. Though air temperature was a primary control on snowpack temperature, rapid snowpack warm-up events were sometimes preceded by strong downslope winds that kept the nighttime air (and canopy) temperature above freezing, thus increasing sensible heat and longwave radiative transfer from the canopy to the snowpack. There was an indication that water vapor condensation on the snow surface intensified the snowpack warm-up. In late winter, subcanopy Qh was typically between −10 and 10 W m−2 and rarely had a magnitude larger than 20 W m−2. The direction of subcanopy Qh was closely related to the canopy temperature and only weakly dependent on the time of day. The daytime subcanopy Qh monthly frequency distribution was near normal, whereas the nighttime distribution was more peaked near zero with a large positive skewness. In contrast, above-canopy Qh was larger in magnitude (100–400 W m−2) and primarily warmed the forest–surface at night and cooled it during the day. Around midday, decoupling of subcanopy and above-canopy air led to an apparent cooling of the snow surface by sensible heat. Sources of uncertainty in the subcanopy eddy covariance flux measurements are suggested. Implications of the observed snowpack temperature changes for future climates are discussed.

Annual production and its dynamics of four dominant mayflies in Hujiaxi Stream of Qingjiang River catchment,Yangtze River Basin

2006年4月至2007年3月对长江支流清江二级支流——胡家溪的大型底栖动物群落结构和生产量进行为期一周年的调查和研究.结果表明,主要蜉蝣优势种小裳蜉(Leptophlebia sp.)、扁蜉(Electrogena sp.)、四节蜉(Indobaetis sp.)的生活史为一年三代,细蜉(Caenis sp.)为一年两代;小裳蜉的年均密度和年均生物量分别为407 ind./m²、1.00 g/m²;扁蜉为150 ind./m²、0.37 g/m²,四节蜉为232 ind./m²、0.30 g/m²,细蜉为91 ind./m²、0.17 g/m².采用龄期频率法测算的周年生产量和P/B分别为:小裳蜉为441.42 g/m²(WW),14.3;扁蜉为434.88 g/m²(WW),7.6;四节蜉为747.21 g/m²(WW),15.0;细蜉为40.52 g/m²(WW),7.2.四种蜉蝣生产量的时间重叠比例相似系数较高,均大于0.55,这可能与四种蜉蝣的生境及食物资源较为相似有关.;During the period of April 2006 to March 2007,secondary production and its dynamics of the dominant species of mayfly community in a second order river (Hujiaxi Stream) of Qingjiang River,Yangtze River Basin were investigated.From the upper to the lower reach of the stream,we sampled at six sites of different habitats quantitatively.The life cycles of the four dominant mayflies, namely Leptophlebia sp.,Electrogena sp.,Indobaetis sp.,and Caenis sp.,were analyzed by the monthly size-class frequency distribution,the cohort and annual production were estimated by size frequency method,and the production dynamics were examined by the method sensu Benke and Wallace (1997).The results show that Leptophlebia sp.,Electrogena sp.,and Indobaetis sp.appear to develop three generations per year,while Caenis sp.completed two generation a year.Their average annual standing stocks were: for Leptophlebia sp.,407 ind./m²,1.00 g/m²;for Electrogena sp.,150 ind./m²,0.37 g/m²;for Indobaetis sp., 232 ind./m²,0.30 g/m²;and for Caenis sp.,91 ind./m²,0.17 g/m²,respectively.The annual production (g/m² (WW)) and the annual P/B ratio of four mayflies were: for Leptophlebia sp.,441.42 g/m² (WW),14.3;for Electrogena sp.,434.88 g/m² (WW),7.6;for Indobaetis sp.,747.21 g/m² (WW),15.0;and for Caenis sp.,40.52 g/m² (WW),7.2.Temporal overlap of secondary production dynamics of the four species,which measured with the proportional similarity index as 0.55,indicates that they utilize similar or same food resources along time dimension.

Secondary production and trophic basis of sinopotamon teritisum in Heizhuchong Stream, Hanjiang Catchment

Macrozoobenthos community plays an important role in material cycle and energy flow in riverine ecosystem. During the period of June, 2003 to June 2004, an investigation on the life cycle and production of the dominant species of macrozoobenthos community in a second-order river of Hanjiang River Basin was carried out. From the upper to the lower reach of Heizhuchong stream, we chose six types of habitats to collect quantitative samples. Station 1 (S1) lied in the middle of the stream with big round rocks in the upper reach, station 2 (S2) was in the inner part of a weir with cobble substratum, station 3 (S3) in the middle of a peacefully flowing section with gravel-sand bottom, station 4 (S4) at the side of the riparian with aquatic macrophytes and snags, station 5 (S5) in the middle of the riffle, station 6 (S6) at the lower reach with a sewage outlet ca 100 meters uppstream. At each station, four quantitative samples were taken with a 167μm D-frame kick net or a Surber net, and the samples were sieved with a 167μm net, sorted in a porcelain dish with naked eye. The specimens were kept in 10% formalin for later processing. The life cycle of the S. teritisum Dai et al. population was analysed by the monthly size-class frequency distribution, the cohort and annual production were estimated by size frequency method. The results showed that S. teritisum completed one generation for nearly 4 years, the reproduction mainly occurred in from middle August to middle October, and most of the senescent individuals died in February. The abundance of the population varied greatly during the year, probably due to the relatively smaller sampling area compared with the strong activity of motion of S. teritisum. Whereas, the variation of the biomass followed the same pattern of the abundance. The a-bundance attained its peak in September with 35 ind/m2, and biomass reached its highest level in June at 41. 7 g/ m2. The estimated cohort production and cohort P/B ratio by size-frequency method were 605.2g/(m2·a) (wet wt) and 5. 5, respectively; the annual production and P/B ratio were 151. 3g/(m2·a) ( wet wt) and 1.4. The reason why the annual production of the animal in Heizhuchong Stream was the relatively higher was because of its high density. By analyzing its stomach content, the proportions of amorphous detritus, caridina, aquatic insect larvae, gastropods and vascular tissues were 45.4% , 10.9% , 35.6% , 5.7% , 8. 1% . Therefore, the contribution rates of the above types of food to production were 10.84% , 18.21% , 59.49% , 9.52% , and 1.94% , respectively.

Secondary production and its trophic basis of five dominant chironomids in Heizhuchong Stream, Hanjiang River Basin

2003年6月至2004年6月间对汉江流域2级河流—黑竹冲河大型底栖动物群落优势种类的生产力进行为期-周年的调查研究,其中主要优势摇蚊中粗腹摇蚊(Pentaneura sp.)和多足摇蚊(Polypedilum sp.)的生活史为-年三代, 小摇蚊(Microtendipes sp.)和帕摇蚊(Pagastia sp.)为-年两代,刺突摇蚊(Chaetocladius sp.)为-年-代.粗腹摇蚊种群生物量和多度在-年中出现两次峰值,多足摇蚊则出现三次,小摇蚊在6月份达到最大峰值,刺突摇蚊在1月份达到最大峰值,帕摇蚊在10月份和次年1月份分别达到次峰值和主峰值.采用龄期频率法(instar-frequency method)测算的周年生产量(鲜重)分别为:粗腹摇蚊,19.9233g/(m²·a),P/B为8.7;多足摇蚊,7.2177g/(m²·a),P/B为8.1;小摇蚊, 0.8996g/(m²·a),P/B为6.0;刺突摇蚊,3.2533 g/(m²·a),P/B为3.4;帕摇蚊,8.5132g/(m²·a),P/B为8.4.除粗腹摇蚊外,其它四种摇蚊的前肠内含物中无形态碎屑所占比例均高于90%,对生产量的贡献率达到77%-96%;粗腹摇蚊的动物性食物所占比例达到14.73%,其对生产量的贡献率高达46.04%.;Macrozoobenthos community plays an important role in material cycle and energy flow in riverine ecosystem. During the period of June, 2003 to.Tune 2004, an investigation on the life cycle and production of the domipant species of macrozoobenthos community in a second-grade river of Hanjiang River Basin was carried out. From the upper reach to the lower reach of Heizhuchong stream, we chose six types of habitats to sample. At each station, two quantitative samples were taken with a 167μm D-frame kick net or a Surber net, and the samples were sieved with a 167μm net, sorted in a porcelain dish with naked eye. The specimens were kept in 10% formalin for later processing. The life cycles of the two dominant chironomids were analysed by the monthly size-class frequency distribution, the cohort and annual production were estimated by size frequency method. The results showed that the Pencaneura sp. and Polypedilum sp. appeared to develop 3 generations for one year, Microtendipes sp. and Pagastia sp. had two generations one year, while Chaetocladius sp. just developed one generation per year, The standing stocks of Pentaneurn sp. and Pagastia sp. had two peaks, that of Polypedilum. sp. had three, while that of Microtendipes sp. and Chaetocladius sp. only had one. The estimated annual production of Pentaneura sp. by size-frequency method was 19. 9233g/(m²·a)(FW), and the P/B ratios was 8.7. The annual production of Polypediluna sp. was 7. 2177 g/(m²·a), and the P/B ratios was 8.1. Annual productiont of Microtendipes sp.was 0.8996g/(m²·a), and P/ B was 6.0;production of Chaecodadius sp. was 3. 2533g/(m²·a), and P/B was 3.4; and that of Pagastia sp. was 8. 5132 g/(m²·a) and 8.4, respectively. By analyzing their fore-gut contents, it was found that all species except Pentaneura sp. consumed a large portion of amorphous detritus, constituting more than 90% of their diets, and contributing 77%-90% to their secondary production.

Frequency distributions of the mixing height over an urban area from SODAR data

The height of the mixing-layer (MLH) is an important parameter in the assessment of the dilution of primarily emitted or secondarily formed air pollutants in the atmospheric boundary-layer. A continuous measurement of MLH is possible only by remote sensing. Here, 17 months of SODAR data have been analysed automatically to derive the MLH over the city of Hannover in Northern Germany. In contrast to earlier studies the MLH has been determined from vertical profiles of the acoustic backscatter intensity and from the variance of the vertical velocity component. The results are presented in form of monthly frequency distributions and mean daily courses of MLH. These statistical evaluations of MLH show a clear annual course and interannual variability. The study shows the possibility to derive meaningful climatological information from long-term SODAR measurements for air quality issues.

A long-term record of photosynthetically available radiation (PAR) and total solar energy at 38.6°N, 78.2°W

Photosynthetically available radiation (PAR; 400–700 nm, E m−2 d−1) is the fraction of the total solar energy (Mjoules m−2 d−1) that is used by organisms for photosynthesis and vision. We present a statistical summary of a 17-yr time series of PAR data (1982–1998) collected near Chesapeake Bay as well as a second set of data on PAR and total solar energy gathered over a shorter time span (1997–1998). The time series data (5,126 daily totals) varied between 1–67 E m−2 d−1 and were used to estimate the minimum and maximum values of PAR as a function of day of the year. In monthly frequency distributions of the PAR data, three modes were observed corresponding to sunny, partly cloudy, and overcast days. The second set of PAR and total solar energy data were used to examine the ratio of PAR to total solar energy, which was 2.04 E Mjoule−1 for PAR between 10 and 70 E m−2 d−1. On overcast days, the ratio increased to as high as 3 E Mjoule−1 as PAR increased in importance as a fraction of the total solar energy. These values were consistent with others in the literature, and the relationships reported here can be used to predict the climatology of PAR and total solar energy within the Chesapeake region. The PAR data were also combined with reported minimum values of PAR for net primary production in the surface mixed layer of the water column of aquatic systems to estimate the combinations of mixed layer depth and diffuse attenuation coefficient (number of optical depths) under which light limitation of phytoplankton primary production is expected to occur.

Reproductive biology of brown trout, Salmo trutta macrostigma Dumeril 1858, in a tributary of the Ceyhan River which flows into the eastern Mediterranean Sea

Summary The study describes some key elements of the reproductive biology, including spawning season, age at sexual maturity, fecundity and egg diameter of the native brown trout, Salmo trutta macrostigma, in a tributary of the Ceyhan River. A total of 197 brown trout (118 females and 79 males) were captured in 2000–2001 by electric fishing. In observations on monthly changes, the gonadosomatic index (GSI) and the monthly frequency distribution of egg diameter confirmed that spawning lasted from November to January. Some 27.7% of the females and 62.5% of the males attained sexual maturity in their second year. The smallest fork length (FL) of brown trout attaining sexual maturity was 17.4 cm for males and 17.8 cm for females. Mean fecundity in age groups II, III, IV and V were 360, 452, 693 and 1283 eggs per female, respectively. One 9-year-old female had a unique 3232 egg count. The mean fecundity of the sampled population was 554 eggs per fish, positively correlated with the FL (mm) (R = 0.8227 ) and body weight (R = 0.8130). The diameter of mature eggs in the spawning season ranged from 3.250 to 5.930 mm, with a 4.146 mm average. Mean egg diameter in age groups II, III, IV and V in the spawning season were 0.813, 3.799, 4.663 and 5.243 mm, respectively. Fecundity, egg weight and diameter were statistically different in all age groups.

Statistical bivariate modelling of wind using first-order Markov chain and Weibull distribution

This paper studies the statistical features of the wind at Oran (Algeria). The data used are the wind speed and wind direction measurements collected every 3 h at the meteorological station of Es Senia (Oran), during the 1982/92 period. The eight directions of the compass card have been considered to build the frequency distribution of the wind speed for each month of the year and each direction. The three-hourly wind data have been modelled by means of Markov chains. First-order nine-state Markov chains are found to fit well the wind direction data, whereas the related wind speed data are well fitted by first-order three-state Markov chains. The Weibull probability distribution function has also been considered and found to fit the monthly frequency distributions of wind speed measurements. Two methods of wind data retrieval are thus made available. In fact, two models of chronological bi-series are obtained describing wind speed and wind direction.

Seasonal variation of the circulation types occurring over southern Greece: a 50 yr study

In this study we introduce a new procedure for grouping the circulation types occurring over an area. This procedure combines the surface air mass characteristics affecting an area with the synoptic conditions prevailing over it. Factor analysis along with cluster analysis are used to derive the circulation types, based on surface meteorological data, as well as on surface pressure grid data. The methods are applied in Athens, Greece, using data for the period 1954-1999. The circulation types are analyzed daily at the sea surface; their temporal evolution is also examined via transition matrices. A total of 315 grid points were used in the area 25-60° N, 10° W-40° E. This analysis derived 8 circulation types for the cold period of the year and 6 for the warm period. The annual and monthly frequency distributions of these types are analyzed. Annual and interannual trends of the types as well as their persistence for 1 and 2 d after their occurrence are examined, as is the transition of one type to another.