Does a monsoon circulation exist in the upper troposphere over the central and eastern tropical Pacific?

考虑到赤道中东太平洋地区(CETP)具有重要的气候影响,以及显著的季节性变率,本文利用可精确描述风向变化的动态标准化季节变率(DNS)方法,分析了该区域上对流层大气环流。结果发现该区域大气环流在冬季和夏季之间存在着类似于经典季风的、明显的季节性反转现象。以此为基础本文提出了赤道中东太平洋上对流层季风的概念,将传统的低对流层季风区扩展到了上对流。     

Relationship between the Interannual Variations of Total Ozone in the Northern Hemisphere and the QBO of Basic Flow in the Tropical Stratosphere

The harmonic analyses of monthly mean total ozone in the atmosphere over the Northern Hemisphere for 26 years (1960-1985) are made by using the Fourier expansion. The analysed results show that there is obviously a quasi-biennial oscillation (QBO) in the interannual variations of the amplitudes of total ozone. Generally, the amplitudes of wavenumber 1 and 2 during the westerly of the equatorial QBO are larger than those during the easterly. In the early winter, the amplitude of wavenumber 1 during the easterly phase is larger, and in the late winter, it is larger during the westerly phase. These are in good agreement with the observational distributions.     

Seasonality of the Interaction between Convection over the Western Pacific and General Circulation in the Northern Hemisphere

The seasonality of the interaction between convection over the western Pacific and general circulation in the Northern Hemisphere (NH) is analyzed in the present paper with singular value decomposition (SVD) and empirical orthogonal function (EOF) analysis approaches, based on 500 hPa monthly mean geopotential height data and high-cloud amount data. The analyses demonstrate that coupled dominant patterns in the interaction between the convection over the western Pacific and the general circulation in NH are different in various seasons. In spring, the convection over the western Pacific is closely related with the western Atlantic (WA) and North Pacific (NP) like patterns of the general circulation in NH, and some associations between the WA and NP like pat?terns and the El Ni?o / Southern Oscillation (ENSO) cycle are also existed. The Pacific Japan (PJ) pattern is the dom?inant pattern in the interaction between the interannual variabilities of the convection over the western Pacific and the general circulation in NH summer. The WA like pattern and 3-4 year period oscillation are also relatively obvious for the summer case. In autumn, the convection over the western Pacific is closely linked with the Eurasian (EU) like pattern and the Atlantic oscillation in the general circulation in NH, it is suggested that in autumn the vitiation of convective activity over the western Pacific is largely affected by the general circulation anomaly (cold air from high latitudes) through EU like teleconnection pattern. Abrupt change happened by the end of 1980’s in the autumn interaction. The strong interaction between the western Pacific (WP) and EU like patterns in the general circulation in NH and the convection over the western Pacific and a linear trend of increasing of this interaction are also suggested in winter. It is also demonstrated that the interaction in summer and winter is stronger than in the transition seasons (spring and autumn).     

Response of the Intensity of Subtropical High in the Northern Hemisphere to Solar Activity

Using the intensity data of each northern subtropical high measured by monthly 500 hPa height charts for the recent 38 years (1954-1991), we calculate their correlations with the monthly sunspot number and monthly solar radio flux at 10.7 cm wave length, respectively. Through strict test, we further confirm a series of high correlations. Next, using a method called the non-integer (year) wave, the significant response of each subtropical high’s intensity to so-lar activity at its main period of 10.9-year length is found. Special attention is paid to that of the eastern Pacific high, the possible mechanism of such sensible response is also analysed.     

Some Aspects of the Diurnal and Semidiurnal Tidal Wind Field in Meteor Zone

The diurnal and semidiurnal tidal wind field variations in the altitudes between 80 and 100 km of the earth's atmosphere over a mid-latitude station are studied by means of the phases of the zonal and meridional wind measurements made at Atlanta (34 ° N, 84 ° W). The rotation of diurnal tidal wind vector is seen to be clockwise at lower heights (80-86 km), swinging between clockwise and anti-clockwise at intermediate heights (88-96 km) and anti-clockwise at higher heights (96-100 km). The senses of rotation of diurnal and semidiurnal tidal wind vectors are compared between the stations located in the same and opposite hemispheres. The results are consistent with the tidal theory in the case of Atlanta and Adelaide (35°S, 139 ° E) whereas in the case of other stations considered in the present study, they showed marked variations.     

Analysis of the non-linearity in the pattern and time evolution of El Niño southern oscillation

In this study the observed non-linearity in the spatial pattern and time evolution of El Niño Southern Oscillation (ENSO) events is analyzed. It is shown that ENSO skewness is not only a characteristic of the amplitude of events (El Niños being stronger than La Niñas) but also of the spatial pattern and time evolution. It is demonstrated that these non-linearities can be related to the non-linear response of the zonal winds to sea surface temperature (SST) anomalies. It is shown in observations as well as in coupled model simulations that significant differences in the spatial pattern between positive (El Niño) versus negative (La Niña) and strong versus weak events exist, which is mostly describing the difference between central and east Pacific events. Central Pacific events tend to be weak El Niño or strong La Niña events. In turn east Pacific events tend to be strong El Niño or weak La Niña events. A rotation of the two leading empirical orthogonal function modes illustrates that for both El Niño and La Niña extreme events are more likely than expected from a normal distribution. The Bjerknes feedbacks and time evolution of strong ENSO events in observations as well as in coupled model simulations also show strong asymmetries, with strong El Niños being forced more strongly by zonal wind than by thermocline depth anomalies and are followed by La Niña events. In turn strong La Niña events are preceded by El Niño events and are more strongly forced by thermocline depth anomalies than by wind anomalies. Further, the zonal wind response to sea surface temperature anomalies during strong El Niño events is stronger and shifted to the east relative to strong La Niña events, supporting the eastward shifted El Niño pattern and the asymmetric time evolution. Based on the simplified hybrid coupled RECHOZ model of ENSO it can be shown that the non-linear zonal wind response to SST anomalies causes the asymmetric forcings of ENSO events. This also implies that strong El Niños are mostly wind driven and less predictable and strong La Niñas are mostly thermocline depth driven and better predictable, which is demonstrated by a set of 100 perfect model forecast ensembles.     

Remote and in situ measurements of aerosol concentration in the Arctic troposphere from the Yak-42D “Roshydromet” research aircraft

The results are presented of measurements of aerosol content at different heights in the Arctic troposphere in the area of Naryan-Mar city and the Yamal Peninsula on June 24, 2014 using in situ and remote instruments installed on the Yak-42D "Roshydromet" research aircraft. The maximum aerosol content was detected in the layer up to 3000 m, and the aerosol concentration in the troposphere over the Yamal Peninsula is higher than that in the area of Naryan-Mar by 100 times. The in situ aircraft instrument measured the number concentration of black carbon particles in the tropospheric aerosol. To identify the sources of aerosol in the Arctic troposphere during airborne measurements the air mass trajectory analysis was performed. Simulations were conducted using the TRACAO trajectory model and FLEXPART particle dispersion model. The possible contribution of long-range and local transport of industrial pollutants to the Arctic troposphere was analyzed. The air mass transport was simulated using the trajectory model. Model computations of aerosol concentration in the troposphere using the satellite data on the gas flaring incite that the high content of black carbon in the lower troposphere over the Yamal Peninsula was caused by its transfer from the oil-producing areas located on the adjoining territory of Russia. The contribution of long-range transport of pollutants from industrial enterprises in Western Europe to the Arctic area under study was insignificant in the period under consideration.     

Amplitude—Phase Characteristics of the Annual Cycle of Surface Air Temperature in the Northern Hemisphere

The amplitude-phase characteristics(APC)of surface air temperature(SAT)annual cycle(AC)in the Northern Hemisphere are analyzed.From meteorological observations for the 20th century and meteorological reanalyses for its second half,it is found that over land negative correlation of SAT ACamplitude with annual mean SAT dominates.Nevertheless,some exceptions exist.The positive correlationbetween these two variables is found over the two desert regions:in northern Africa and in Central America.Areas of positive correlations are also found for the northern Pacific and for the tropical Indian and PacificOceans.Southward of the characteristic annual mean snow-ice boundary (SIB) position,the shape ofthe SAT AC becomes more sinusoidal under climate warming.In contrast,northward of it,this shapebecomes less sinusoidal.The latter iS also found for the above-mentioned two desert regions.In theFar East(southward of about 50°N),the SAT AC shifts as a whole:here its spring and autumn phasesoccur earlier if the annual     

CISK-rossby wave and the 30-60 Day Oscillation in the Tropics

The 30-60 day oscillation is an important aspect of the atmospheric variance in the tropical area. A number of works have been done on this phenomenon, this article is a further one. A quasi-geostrophic linear model that consists of a two-layer free atmosphere and a well-mixed boundary layer is used to investigate the instability of intraseasonal oscillation, its propagation and vertical structures. Results show that the dynamical coupling and interaction between the barotropic and baroclinic components via boundary layer convergence / divergence are responsible for the appearance of a new kind of low-frequency wave. Such wave is very different from the traditional tropical Rossby wave. It can propagate westward and eastward. Some behaviours of it appear to resemble the observed 30-60 day oscillation mode in many aspects, such,as vertical structures, zonal and meridional propagations. Now many researchers emphasize the direct relationship between CISK-Kelvin mode and the tropical atmospheric 30-60 oscil     

Warming of intermediate layers in the upper Oyashio in 1953–2007

Considerable variations in intermediate water characteristics were found in the upper Oyashio based on the oceanographic data from 1953 to 2007. The long-term temperature trend at the 26.75σ_? isopycnal is 0.03°C/year. This temperature trend is considerably higher than that determined earlier for the Sea of Okhotsk intermediate water and much higher than the World Ocean temperature trend. The westward transport of warm and salty water of the Alaskan Stream is most likely to cause the changes in the Kamchatka Current and upper Oyashio. It is established that Aleutian mesoscale eddies move westward from the location of their formation south of the Blizhniy Strait and transport warm water (3.8–4.2°C) in their core (100–600 m, ～26.75σ_?)). As the trajectory of eddies is quite stable, the westward flow of warm and salty intermediate waters considerably influences the upper Oyashio characteristics.     

Observing upper troposphere–lower stratosphere climate with radio occultation data from the CHAMP satellite

High quality observations of the atmosphere are particularly required for monitoring global climate change. Radio occultation (RO) data, using Global Navigation Satellite System (GNSS) signals, are well suited for this challenge. The special climate utility of RO data arises from their long-term stability due to their self-calibrated nature. The German research satellite CHAllenging Minisatellite Payload for geoscientific research (CHAMP) continuously records RO profiles since August 2001 providing the first opportunity to create RO based climatologies for a multi-year period of more than 5 years. A period of missing CHAMP data from July 3, 2006 to August 8, 2006 can be bridged with RO data from the GRACE satellite (Gravity Recovery and Climate Experiment). We have built seasonal and zonal mean climatologies of atmospheric (dry) temperature, microwave refractivity, geopotential height and pressure with 10° latitudinal resolution. We show representative results with focus on dry temperatures and compare them with analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Although we have available only about 150 CHAMP profiles per day (compared to millions of data entering the ECMWF analyses) the overall agreement between 8 and 30 km altitude is in general very good with systematic differences <0.5 K in most parts of the domain. Pronounced systematic differences (exceeding 2 K) in the tropical tropopause region and above Antarctica in southern winter can almost entirely be attributed to errors in the ECMWF analyses. Errors resulting from uneven sampling in space and time are a potential error source for single-satellite climatologies. The average CHAMP sampling error for seasonal zonal means is <0.2 K, higher values occur in restricted regions and time intervals which can be clearly identified by the sampling error estimation approach we introduced (which is based on ECMWF analysis fields). The total error of this new type of temperature climatologies is estimated to be <0.5 K below 30 km. The recently launched Taiwan/U.S. FORMOSAT-3/COSMIC constellation of 6 RO satellites started to provide thousands of RO profiles per day, but already now the single-satellite CHAMP RO climatologies improve upon modern operational climatologies in the upper troposphere–lower stratosphere and can act as absolute reference climatologies for validation of more bias-sensitive climate datasets and models.     

Numerical Simulation Study on the Scientific and Methodological Aspects of the Brazilian Proposal

1. IntroductionObservations of surface air temperature indicatethat a significant global average warming has occurredduring the 20th century. The Intergovernmental Panelon Climate Change (IPCC, 2001) concludes that thereis new and stronger evidence that man has influencedthe climate. International negotiations have led to afirst step in combating climate change with the UnitedNations Framework Convention on Climate Change(UNFCCC) and the Kyoto Protocol, but further stepsare needed in …     

Power and Cross-Spectra for the Turbulent Atmospheric Motion and Transports in the Domain of Wave Number Frequency Space: Theoretical Aspects

The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed.     

Role of high- and low-frequency winds and wave reflection in the onset, growth and termination of the 1997–1998 El Niño

The present study aims at studying the role played by high-frequency wind variability, wave reflection and easterly wind anomalies in the western Pacific in the onset, growth and termination phases of the 1997–1998 El Niño using the Trident intermediate coupled model and observations. While the anomalous strength of the trade winds in 1996 favored the initiation of a warm event in 1997 (via western Pacific boundary Rossby wave reflection), the actual timing of the onset and the amplitude of the event resulted from the large March 1997 wind event. Once initiated, high-frequency westerly winds strongly contributed to the rapid growth of the warm event and to the displacement of the eastern edge of the warm-pool. Moreover, both easterly and westerly high-frequency wind variability in 1997–1998 contributed to the amplitude of the event, set the evolution of the warm event and potentially influenced the equatorial Pacific conditions at least one year after the El Niño event. In addition, eastern boundary reflection also significantly contributed to the amplitude and duration of the warm event, whereas its termination was a combination of various factors: reflection of upwelling Rossby waves at the western boundary and large easterly wind anomalies observed in the western Pacific from November 1997 to early 1998. These factors were sufficient to terminate the event and to switch temperature anomalies from warm to cold. To conclude, understanding the coupling between the high- and low-frequency wind variability, i.e., studying ENSO as a multi-scale phenomenon, will certainly lead to a better comprehension of the diversity of its behavior and potentially to an improvement of its predictability.     

Vertical behaviour and meteorological properties of air masses in the southwest of the Iberian Peninsula (1997–2007)

Air masses are characterized by physical (temperature, humidity) and chemical (transported gases and aerosols) properties, being associated their arrival to different meteorological scenarios. The knowledge of the air masses over a region is fundamental as complementary information in several atmospheric studies, being the calculation of back-trajectory the most widely used tool whenever air masses are analyzed. A study of air masses has been carried out in southwestern Iberian Peninsula using 5-day kinematic back trajectories computed by the HYSPLIT model at three heights (500, 1,500 and 3,000 m) from 1997 to 2007. The main aims have been to characterize their vertical behaviour and their thermal and humidity properties. Thirteen trajectory clusters have been defined, showing the northerly and westerly clusters a high coupling degree. Seasonal daily variation of potential temperature and specific humidity has been analyzed, obtaining higher differences among clusters in the cold season.     

Impacts of two types of El Niño on atmospheric circulation in the Southern Hemisphere

Based on NCEP/NCAR （National Centers for Environmental Prediction/National Center for Atmo- spheric Research） reanalysis data from 1979 to 2010, the impacts of two types of E1 Nino on atmospheric circulation in the Southern Hemisphere （SH） are analyzed. It is shown thaL when a warming event occurs in the equatorial eastern Pacific （EP E1 Nino）, there is a negative sea level pressure （SLP） anomaly in the east- ern Pacific and a positive one in the western Pacific. Besides, there exists a negative anomaly between 40°S and 60°S and a positive anomaly to the south of 60°S. When a warming event in the central Pacific （CP E1 Nino） occurs, there appears a negative SLP anomaly in the central Pacific and a positive SLP anomaly in the eastern and western Pacific, but the SLP anomalies are not so evident in the SH extratropics. In particular, the Pacific-South America （PSA） pattern induced by the CP E1 Nino is located more northwestward, with a weaker anomaly compared with the EP E1 Nino. This difference is directly related with the different position of heating centers associated with the two types of E1 Nino events. Because the SST anomaly associated with CP E1 Nino is located more westward than that associated with EP El Nino, the related heating center tends to move westward and the response of SH atmospheric circulation to the tropical heating changes accordingly, thus exciting a different position of the PSA pattern. It is also noted that the local meridional cell plays a role in the SH high latitudes during EP E1 Nino. The anomalous ascending motion due to the enhancement of convection over the eastern Pacific leads to an enhancement of the local Hadley cell and the meridional cell in the middle and high latitudes, which in turn induces an anomalous descending motion and the related positive anomaly of geopotential height over the Amundsen-Bellingshausen Sea.     

Modelling the behaviour of oil spills in ice‐infested waters

Abstract

This paper describes methodologies developed for predicting the drift and spread of oil spills in ice‐infested waters. Particular emphasis is placed on oil spills in medium and high ice concentrations. For ice concentrations greater than about 30%, the oil is found to drift with the ice. Empirical methods are used to determine the spread of oil in ice of different concentrations. The study showed that the equilibrium oil thickness in slush or brash (broken) ice is nearly 4 times that on cold water, which is itself very different from that on warm water. Comparisons with limited available data show good agreement.